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1Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Applications ― Battery monitoring for industrial, automotive,
railroad and utility scale storage
DescriptionThe Sendyne SFP200 IC is a high precision sensing
IC addressing the unique requirements of electrical
energy storage and monitoring. The IC is rated for the
automotive temperature range of -40 °C to +125 °C.
It simultaneously measures bi-directional DC current
through a resistive shunt and is capable of sensing
three voltages with flexible range.
For current sensing, the SFP200 achieves an un-
calibrated maximum offset error of less than 200
nanovolts when measuring the voltage drop across
the shunt. This performance extends throughout the
entire automotive temperature range. With an ap-
propriate shunt, the IC can accurately measure a wide
dynamic range of currents from tens of thousands of
amperes to milliamperes.
Sendyne’s proprietary, patented “Continuous Cali-
bration” technology allows the IC to compensate for
thermal drifts including those arising from external
interface circuitry such as EMI/RFI/anti-aliasing fil-
ters. The IC provides internally-accumulated coulomb
counting information. Communications are achieved
via an isolated CAN 2.0B interface (500 kbaud). The
SFP200MOD is an implementation of the reference
design contained in this document.
Sendyne® Sensing Products Family
Sendyne SFP200 IC for Precision Automotive Grade Current and Voltage Measurements
Operating Specifications with Suggested Circuit and the Sendyne SFP Shunt
Parameter Value
Power supply +5.5~+6.5 V Isolated - See suggested schematics
Interface CAN 2.0B isolated, termination per user’s application, 120 Ω suggested
Current measurement range ±600 A continuous / ±1250 A (220 s), <±1.0 % error, using Sendyne SFP
Shunt attached to 108 mm2 busbars
Voltage measurement range 3 Channels: ±800 V nominal, ±1000 V/channel max, <±1.0 % error
Rating Automotive
Power consumption < 350 mW
IC operating temperature range -40 °C to +125 °C
2 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
― High precision current and voltage sensing IC
― Pre-programmed, no additional firmware required
― Achieves an offset error of less than 200 nanovolts
― Systems using the SFP200 IC need only be calibrated at a single room temperature point
― Accurate voltage measurement with flexible range
― Automotive temperature range, –40 °C to +125 °C
― Low power consumption
― “High” or “Low” side current sensing and voltage sensing reference point with isolated front end
― Patented zero offset functionality
― Automatically compensates for the shunt’s varying resistance relative to temperature (Gain Error)
― Built-in calibration for voltage measurements
― Separate charge, discharge, and total Coulomb counters
― Automotive rated, AEC-Q100
― Reference design as described in this, and related documents, allows for configurability based on system specific
needs (e.g. different input power supply, different full-scale voltages, no voltage measurement, etc.)
― Isolated CAN2.0B interface (500 kbaud)
Features
3Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
SFP200 IC Pin Description LQFP64
Pin Number Pin Name Pin Function1 S4 One of the digital input pins for selection of the CAN address,
40 kΩ (typical) built-in pull-up
2 S3 Same as above
3 S2 Same as above
4 S1 Same as above
5-6 NU - Not used, do not connect
7 DVDD Positive supply voltage for the digital circuits in the IC. DVDD
pin 7 must be connected to DVDD pin 41
8 AVDD Positive supply voltage for the analog circuits in the IC and
voltage reference for the ADC. AVDD voltage must be within
±300 mV of the DVDD voltage
9-10 AVSS Negative supply voltage for the analog circuits in the IC. AVSS
pins must be connected to DVSS pin
11 XIN Input to the built-in crystal oscillator circuit; to be connected
to the external feedback resistor and 16 MHz crystal with
built-in load capacitors
12 XOUT Output from the built-in crystal oscillator circuit; to be con-
nected to the external feedback resistor and 16 MHz crystal
with built-in load capacitors
13 NU - Not used, do not connect
14 CH2S2 Digital output pin controlling cross-bar switch for CH2
current sensing
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
48474645444342414039383736353433
NUNUNUNUNUNUNU
DVDDDVSS
NUNUNUNUNUNUNU
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
HB
2C
H1S
2C
H1S
1V
TH1
ZRE
FZD
RV
NU
NU
CU
R2N
CU
R1P
VX
4V
X3
VX
2V
X1
CU
R2P
CU
R1N
123456789
10111213141516
S4S3S2S1NUNUDVDDAVDDAVSSAVSSXINXOUTNUCH2S2CH2S1HB1
RIO
3R
IO2
RIO
1N
UN
UN
UN
UN
UN
UN
UN
UN
UC
AN
_R
XC
AN
_TX N
UN
U
PIN 1
SFP200
4 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Pin Number Pin Name Pin Function
15 CH2S1 Digital output pin controlling series-disconnect switch for
CH2 current sensing
16 HB1 Optional Heartbeat outputs; see design notes section
17 HB2 Optional Heartbeat outputs; see design notes section
18 CH1S2 Digital output pin controlling cross-bar switch for CH1
current sensing
19 CH1S1 Digital output pin controlling series-disconnect switch for
CH1 current sensing
20 VTH1 Analog input pin for thermistor sensing
21 ZREF Analog input pin for analog-zero reference voltage sensing
22 ZDRV Digital output pin for analog-zero reference voltage control
23-24 NU - Not used, do not connect
25 CUR2N Negative analog input for CH2 current sensing
26 CUR1P Positive analog input for CH1 current sensing
27 VX4 Analog input for voltage measurements, referenced to VX1
pin 30
28 VX3 Analog input for voltage measurements, referenced to VX1
pin 30
29 VX2 Analog input for voltage measurements, referenced to VX1
pin 30
30 VX1 Analog input, reference for voltage measurements on VX2,
VX3, and VX4
31 CUR2P Positive analog input for CH2 current sensing
32 CUR1N Negative analog input for CH1 current sensing
33-39 NU - Not used, do not connect
40 DVSS Negative supply voltage for the digital circuits in the IC. DVSS
pin must be connected to AVSS pins.
41 DVDD Positive supply voltage for the digital circuits in the IC. DVDD
pin 41 must be connected to DVDD pin 7
42-50 NU - Not used, do not connect
51 CAN_TX Digital output pin for the CAN interface data stream
52 CAN_RX Digital input pin for the CAN interface data stream
53-61 NU- Not used, do not connect
62 RIO1 Reserved digital I/O pin, factory test only; do not connect,
keep open
63 RIO2 Same as above
64 RIO3 Same as above
NU pin name means Not Used pin. These pins are electrically connected to the silicon chip via bonding wires, there-fore they should be left as electrically open on the PCB, i.e. not connected to any potential on the board.
5Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Absolute Maximum Ratings
TA= -40 °C to +125 °C
Parameter RatingAVSS to DVSS ±0.05 V
AVDD to DVDD ±0.3 V
Input lines VSS -0.3 V to
DVDD +0.3 V
DVDD -0.3 V to 6.0 V
ESD (human body model)
all pins
±6 kV
ESD (charged-device model) ±500 V
Storage temperature -55 °C to +150 °C
Lead temperature
soldering reflow
260 °C Max,
per J-STD-020
Stresses above those listed under Absolute Maximum
Ratings may cause permanent damage to the device.
This is a stress rating only; functional operation of the
device at these or any other conditions above those
indicated in the operational section of this specifica-
tion is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device.
Electrostatic charges readily accumulate on the
human body as well as test equipment, and can
discharge without detection. Although this product
features protection circuitry, damage may occur in
devices subjected to high energy ESD. Proper ESD
precautions should be taken to avoid performance
degradation or loss of functionality.
6 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Electrical Specifications
These specifications are based on the performance of Sendyne SFP200MOD units
Parameter Min Typ Max Units Conditions/CommentsPower and GeneralIC operating
temperature range
-40 +125 °C
IC Supply Voltage 5.95 5.00 5.05 V Regulated supply voltage for the IC
Supply Voltage 5.5 6 6.5 V Unregulated supply voltage for isolated
part of the circuit
Supply Current 40 mA Nominal load of the isolating DC/DC con-
verter, consumption of the whole isolated
circuit
Start-up time 0.5 0.75 s After initial application of power and
power supply stabilization
Current MeasurementNominal full-scale current ±500 A Continuous rating in still air at room
temperature of 25 °C with module
connected to busbars of at least 108 mm2
cross-section (the same cross-section as
the shunt)
Peak full-scale current ±1250 A Maximum current value that is measured
without clipping; less than 5 s duration,
the same conditions as above
Current offset error* -50 <±20 +50 mA Uncalibrated performance, applies over
the full operating temperature range
Current noise error* <25 50 mARMS 1 Hz reporting rate
Current value error* -0.25 +0.25 % Room temperature, test current ±20 A or
higher
-0.5 +0.5 % 0 oC to +50 oC, test current as above
-1 +1 % -40 oC to +125 oC, test current as above
±1 % End of life, test current as above
Current measurement
resolution
<100 μA Minimum discernible current change; cor-
responds to one count of Analog to Digital
Converter (ADC), 1 Hz current report rate
Charge measurement
resolution
<1 μC Minimum discernible amount of charge
change,100 Hz report rate
Technical Specifications
* The combined Total Current Error is the ±sum of Current offset error, Current noise error, and
[Current value error] x [measured value]. For currents over 100 A the Current offset error and the Current noise error
could be omitted from the calculation since they will typically contribute less than 0.05 % to the error.
7Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Electrical Specifications
These specifications are based on the performance of Sendyne SFP200MOD units
Parameter Min Typ Max Units Conditions/CommentsVoltage MeasurementNominal Full-scale voltage
range
±800 V In reference to negative terminal
of the shunt
Maximum transient voltage ±982 ±1002 V Maximum voltage value measured and
reported without clipping or distortion
Voltage offset error -300 <±50 +300 mV VX = 0 V, applies over the full ambient
operating temperature range,
TA = -40 °C to +125 °C
Voltage gain error <±1 % Over full operating temperature range,
TA = -40 °C to +125 °C
Voltage noise error <12 20 mVRMS 1 Hz reporting rate
Voltage measurement
resolution
<1 mV Minimum discernible voltage change;
corresponds to one count of ADC, voltage
report rate of 10 Hz or lower
Impedance of the voltage
measurement inputs
12 MΩ Resistive dividers utilized for the volt-
age inputs consist of four (4) elements
connected in-series. Combined Limiting
Element Voltage is 2 kV, and combined
Maximum Overload Voltage is 4 kV.
Temperature Measurement (For shunt temperature measurement) Absolute temperature
measurement error
-5 ±0.5 +5 °C Built-in temperature sensor for shunt
temperature measurements
Temperature measurement
resolution
10 m°C Practical temperature measurement
granularity
IsolationTest voltage 3 kVDC CAN interface to SHUNT.
1 min duration
Communication
Interface Spec Speed TerminationNumber of units in the same CAN branch
CAN 2.0B 500 kbit/s *None or
120 Ω
16 (DIP switch or wires/jumpers selects
one of sixteen CAN address sets)
* When two or more devices are connected to the same CAN branch, only a single device may have the termination.
8 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Measured Performance Data (based on Sendyne SFP200MOD units)
Current magnitude error over temperature range of –40 °C to +125 °C
Cur
rent
mag
nitu
de e
rror
(%)
Temperature (oC)
-40 -20 0 20 40 60 80 100 120 140
3.0
2.5
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
9Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Performance data provided in this datasheet assumes the combined use of Sendyne’s SFP200 IC and SFP 18 µΩ shunt
(please see separate Sendyne SFP Shunt datasheet). Automatic compensation for changes in resistance due to tem-
perature fluctuations (Gain Error) is pre-set in the SFP200 IC for use with Sendyne’s RoHS compliant SFP Shunt. If a
shunt other than the Sendyne SFP Shunt is selected for use, the automatic compensation feature must be disabled, or
alternatively, another compensation table can be loaded in its place. Both options can be achieved through the CAN
interface. No firmware changes are needed. For more detailed information, including instructions instructions on how
to create an appropriate compensation table please see “Notes on Automatic Calibration for Systems Using Shunts
Other Than the Sendyne SFP Shunt”.
A Note About ShuntsThe Sendyne IC can work with any shunt of any material of any resistance, including, for example, a copper busbar, as
long as that material remains reasonably consistent throughout production. For optimal performance, an appropriate
compensation table must be loaded onto the IC through the CAN 2.0B interface. The SFP200 IC ships as default with
a compensation table for the Sendyne SFP Shunt. For instructions on creating an appropriate compensation table
please refer to “Notes on Automatic Calibration for Systems Using Shunts Other Than the Sendyne SFP Shunt”.
SFP200 IC and SFP Shunt
10 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Table for selection of the CAN address set
Switch 1 (IC pin 4)
Switch 2 (IC pin 3)
Switch 3 (IC pin 2)
Switch 4 (IC pin 1)
Address set Notes
Off Off Off Off 1 Default
Off Off Off On 2
Off Off On Off 3
Off Off On On 4
Off On Off Off 5
Off On Off On 6
Off On On Off 7
Off On On On 8
On Off Off Off 9
On Off Off On 10
On Off On Off 11
On Off On On 12
On On Off Off 13
On On Off On 14
On On On Off 15
On On On On 16
“Off” signifies a sensing pin is not connected / floating; “On” signifies a sensing pin is shorted to IC’s DVSS (local logic GND) potential.
The IC can operate with sixteen (16) different sets of CAN addresses, thus 16 modules based on the SFP200 IC can
simultaneously reside on the same CAN bus stub. When two or more devices are connected to the same CAN branch,
only a single device may have the 120 Ω suggested termination between the two CAN communications lines (assum-
ing that the Host has the termination at the other end of the transmission line).
Selection of a specific set of addresses is performed by the activation of one or more switches from the four individual
switches on the quad-switch unit (or selectively cutting the traces on the PCB, as shown below). After the state of any
of the switches is changed, it is required that the module is powered-down (supply voltage is removed) for 10 seconds,
in order for the new settings to be accepted. In other words, any changes made while the unit is powered on will be
ignored until the next power-up.
Selected address set follows the switch settings shown in the table below:
CAN Addresses Selection
11Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
S1 S2 S3 S4
DVS
S
IC
Address selection with switches
The Host (controller) communicates with the SFP200 via the CAN interface using the request-response method.
The Host issues a message requesting the specific data, and SFP200 responds with that data. For details on the com-
position of these messages, please see the following Communications section. Requests for data from the Host and
the response of the SFP200 are sent using different Extended Message ID values. These values are shown in the table
below for the sixteen (16) address sets supported by the IC.
Table for SFP200 supported Message ID sets
Address Set Request Message ID Response Message ID Notes
1 0xA100201 0xA100200 Default Address Set
2 0xA100211 0xA100210
3 0xA100221 0xA100220
4 0xA100231 0xA100230
5 0xA100241 0xA100240
6 0xA100251 0xA100250
7 0xA100261 0xA100260
8 0xA100271 0xA100270
9 0xA100281 0xA100280
10 0xA100291 0xA100290
11 0xA1002A1 0xA1002A0
12 0xA1002B1 0xA1002B0
13 0xA1002C1 0xA1002C0
14 0xA1002D1 0xA1002D0
15 0xA1002E1 0xA1002E0
16 0xA1002F1 0xA1002F0
12 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Communications
Features
― CAN2.0B extended frame format
― 500 kbaud
― Polling mechanism allows host to determine the rate of incoming data
Registers The SFP200 provides Current, Voltage, Shunt Temperature and Coulomb-count registers, mapped in memory space
as shown in Table 3. Registers can only be accessed one at a time. All other addresses are reserved; any writes outside
of the defined register address range are ignored.
Message Frames Access to the registers of the SFP200 is accomplished through polling by the host. When operated with the Default
Address Set, the SFP200 listens for extended ID 0xA100201 with data length of 1. Data byte 0 of the message carries
the requested register address. If the message data length is greater than 1, the message is ignored and discarded. The
simple structure of the message is demonstrated in Table 1.
Host Request for Data, Default Address Set
Request message ID Data byte 00xA100201 Register Address
When operated with the Default Address Set, the SFP200 returns data using message ID 0xA100200. Byte 0 of the
returned message is the requested register, followed by the data with the most significant byte first. See Table 2 for
details.
SFP200 Response, Default Address Set
Response Message ID
Data byte 0 Data byte 1 Data byte 2 Data byte 3 Data byte 4
0xA100200 Register Address MSB data byte Data byte Data byte LSB Data byte
Register Map
Register address Description0x00 Reserved
0x20 Current, μA
0x40 Coulomb Count Low, μC
0x41 Coulomb Count High, μC * 232
0x60 Voltage 0, μV
0x61 Voltage 1, μV
0x62 Voltage 2, μV
0x80 Temperature, m°C
Table 1
Table 2
Table 3
13Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Data format
All data returned by the SFP200 is in a 32-bit signed integer format (2’s complement signed data). Divide the signed
data by 106 (1000000) to get the values in Amperes or Volts. For Temperature, divide the signed data by 103 (1000) to
get the values in degrees Celsius.
Coulomb counts are split into two registers, Coulomb Count High and Coulomb Count Low. The data is a combined
64-bit signed integer value (2’s complement signed data). Divide the signed data by 106 to get the value expressed in
Coulombs. Register Coulomb Count Low should always be read first. Read of this register causes Coulomb Count High
to latch and remain unchanged until Coulomb Count Low is read again.
Example Communications, Default Address Set
Origin Message ID Byte 0 Byte 1 Byte 2 Byte 3 Byte 4Host 0xA100201 0x60
SFP200 0xA100200 0x60 0xFF 0x45 0xA1 0x34
Example walkthrough1. Host sends a request message with ID 0xA100201 (extended), byte 0 set to 0x60 (voltage) and message
length set to 1.
2. The SFP200 receives the message and responds with the requested register address and contents using
extended ID 0xA100200.
3. Host receives the message and checks byte 0 to determine if the correct register address has been received.
4. Host re-assembles the bytes into a signed integer, and then divides by 106 to scale the value.
Pseudo-code for Current and Voltage received data reassembly by the host:// Example raw data from SFP module
unsigned char byte1 = 0xFF;
unsigned char byte2 = 0x45;
unsigned char byte3 = 0xA1;
unsigned char byte4 = 0x34;
// Assembling to 32 bit unsigned integer
unsigned int reassembled_data = 0;
reassembled_data |= byte1 << 24;
reassembled_data |= byte2 << 16;
reassembled_data |= byte3 << 8;
reassembled_data |= byte4 << 0;
// Converting to volts
float voltage = (int)(reassembled_data) / 1000000.0f;
// Calculated value is -12.213964 Volts
Table 4
14 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
SHU
NT
x1
x1
x1
x1
Current Sensing
Voltage sensing
HEARTBEATLEDs(optional)
ADC
t
21
22
32
26
19
18
AVDD
GND
20
28
30
29
SW SW
GND
SW SW
GND
GND
Temperature sensing
51
8
AVDD
GND
7 41
9 10 40
DVDD
Control Logic
Communications Logic
52
11
12
CLOCK
16
17
CAN_TX
CAN_RX
CRYSTAL 16 MHz
14
15
31
25 G
G
x1
x1
ZDRVControl
ZREF
x1
27
x1
GND GND
CAN
VREF
GND
HV1
HV2
HV3
4
3
2
1
GND
CAN Address Selection
Nonvolatile memory for
calibration data
Calibration controls
Block Diagram in Application Circuit
15Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Suggested Schematic
J2J1
0J1
1J4
J3J1
J12
J9
Sen
dyne
18
µΩ s
hunt
(SFP
SH85
36-1
-8P1
8U)
NU
NU
NU
NU
NU
NU
NU
NU
NU
NU
NU
CA
N_
RX
CA
N_
TX
RI0
3R
I02
RI0
1
NUNUNUNUNU
NUNUNU
NUNUNU
NU
DVSSDVDD
ZDR
VN
UN
U
ZRE
FV
TH1
CH
1S1
CH
1S2
CU
R2N
CU
R1P
VX
4V
X3
VX
2V
X1
CU
R1N
CU
R2P
NUNU
DVDDAVDDAVSSAVSS
NUXOUT
XIN
CH2S2CH2S1
S1S2S3S4
SFP2
0058596061626364 51525354555657 4950
123456789
10111213141516
23222120191817 292827262524 323130
39383736353433
46454443424140
4847
To/F
rom
isol
ated
C
AN
tran
scie
ver
U1
GN
DG
ND
GN
D
+5V
+5V
A +5V
C16
C17 C15
100n
F
100n
F
10uF
L5FBEAD
R23
1M 1
%
X1
16M
Hz
CAN address select
GN
D
C9100nF
R12
10k
1%
R13
1M 1
%
R38
1M 1
%
R11
10k
1%
ZREF
+5V
GN
D
GN
DC14
100n
F
C10 C12
C13
R19R18
C11 R17
R16
30k
1%
30k
1%
30k
1%
30k
1%
100n
F
100n
F
100n
F
100n
F
T1TE
ST_
POIN
T
GN
DC8
10uF
R15
10k
1%
R14
1M 1
%G
ND
U2
MCP6234
DM
G69
68U
DM
DM
G69
68U
DM
R6
R7
499
1%
499
1%
GN
D
C2
100n
F
C3
100n
F
C6
100n
F CH
2P
CH
2N
ZRE
F
CH
1P
CH
1N
C7
100n
F
C4
100n
F
C5
100n
F
R8
R9
499
1%
499
1%
GN
D
+5V
A R5
10k
1%
10k @ 23C
TH1
GN
DG
ND
C1
100n
F
1234567
12111098
1314
VOUTB
VINB -
VINB +
VDD
VINA +
VINA -
VOUTA
VOUTC
VINC -
VINC +
VSS
VIND +
VIND -
VOUTD
+5V R27
1M 1
%
SHU
NT
SHU
NT
SHU
NT
SHU
NT
J10
J11
J12
J9
Q1
1 2 3
6 5 4
Q2
1 2 3
6 5 4
R4
10k
1%
R3
10k
1%
R2
10k
1%
R1
10k
1%
CH
2S2
CH
1S1
CH
1S2
CH
2S1
R20
R24
R28
R31
3M 1
%3M
1%
3M 1
%3M
1%
VSE
NSE
J6
R21
R25
R29
R32
3M 1
%3M
1%
3M 1
%3M
1%
VSE
NSE
J7
R33
R30
R26
R22
3M 1
%3M
1%
3M 1
%3M
1%
VSE
NSE
J8
Full
- Sca
le ±
982
V(i
nput
impe
danc
e 12
M a
s sh
own)
Thes
e re
sist
ors
have
a v
alue
of
750k
1%
for
full-
scal
e in
put ±
247
V
J1 J2 J3 J4TIE
DO
WN
TIE
DO
WN
TIE
DO
WN
TIE
DO
WN
NUNU
NU
NU
Inpu
t sw
itch
ing
EM
I/R
FI F
ilter
s
Cur
rent
Am
plifi
ers
Clo
ckB
ypas
s
Vol
tage
Sens
ing
Shun
t Tem
p.Se
nsin
g
16 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Suggested Schematic Isolated DC/DC and CAN communication
Isolation
Isolated powersupply 5.5-6.5 V
CAN_RXCAN_TX
GND
GND GND
GND
ISOLATED
ISOLATED
+5V
ISOLATED
12345678
131211109 161514
213
456
32
123
4
5
C28
10uFC29
100nF
C20
100nF
GNDPWR GNDPWR GNDPWR
GNDPWR
GNDPWR
GNDPWR
GNDPWR GNDPWR GNDPWR GNDPWR GNDPWR
GNDPWR
BA
V70
W76
0390
014
R36
1VDD
FBE
AD
L1
TX1
D1
U3
SI86
22_
WB
1234
8765
TJA1051T
U4
C1810uF
C19100nF
1234
NUP2105L
CONN_01X04
1
23
D2P1
R39
120
CANHCANL
C311uF 100V
R421
U5
SN6501-Q1
TXDGNDVCC RXD
SCANHCANL
NC
GND
GND
D
D2VCC
GN
D2
NC
NC
B2
B1
VD
D2
NC GN
D2
NC
GN
D1
NC
A2 A1
VD
D1
NC
GN
D1
XM
ITR
RC
VR
RC
VR
XM
ITR
C22 47pF
R37
100C21
100n
F
1
Isolated DC/DC
CAN Tranceiver
Isolated Digital I/O
Supply VoltageFiltering & Current Limit
GND
GND
GNDC271uF
C2410uF
FBE
AD
L3
GNDGND
C2310uF
VO
UT
VIN
GN
DU6
+5 V
MC
P170
3AT-
5002
E
LDO & Reference
17Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
SFP200 IC Packaging
12
10
6 5
PIN 11
16 33
48
64 49
12° (4X)
seating plane 12° (4X)
1.60 MAX
0.270.17
(64X)
0.5(60X)
PITCH
LQFP6410 x 10 x 1.4 P 0.5All dimensions are in millimeters
5 6
10 12
17 32
18 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Design Notes for SFP200 Circuit
General Background Information The SFP200 is a precision mixed-signal analog-digital
IC that provides measurements for current (by sensing
the voltage drop across a shunt), voltage and shunt
temperature.
Measurements of large currents are difficult due to
high heat generation (Joule heating) in the shunt. In
order to provide sufficient accuracy and negate the
effects of various errors, the voltage drop across the
shunt must be adequately large. However, the heat
production resulting from the passage of the current
is linearly dependent on that voltage drop. The only
solution for limiting the heat is to lower the resistance
of the shunt, thus limiting the voltage drop across the
shunt.
When dissimilar materials are jointed together, and
when the assembly is heated (due to environment
and/or Joule heating), there are so-called thermoelec-
tric voltages generated; these are commonly known as
resulting from Seebeck / Peltier / Thomson (Kelvin)
effects. The value of these errors in the carefully con-
structed devices may be in the range of single micro-
volts (10-6 V) to as much as several tens of millivolts.
These error voltages will manifest themselves as large
offset (deviation from zero) errors in the measured
current.
Sendyne’s proprietary and patented method reduces
the errors associated with sensing of the low-level
voltages, and enables measurements of the large cur-
rents with shunts having extremely small resistance.
This is achieved with the proprietary circuit that
reduces voltage-sensing errors at the shunt to below
200 nV (0.0000002 V), independent of the ambient/
environment or shunt’s operating temperature, and
operating within the whole specified temperature
range of –40 °C to +125 °C.
The Standard Sendyne shunt utilized in the
SFP200MOD devices have a nominal resistance value
of 18 µΩ; maximum voltage drop at the declared
maximum full-scale (unclipped) currents of ±1250 A
is ±22.5 mV and nominal voltage drop at the currents
of ±500 A (that are rated for continuous operations)
is ±9 mV, with resulting Joule heating (power loss) of
only 4.5 W.
In addition, Sendyne’s circuit allows the use of RC
filtering for the reduction of the RFI/EMI-induced
noise, specifically without any detrimental effects to
the quality and accuracy of the current measurements.
Any errors resulting from thermoelectric effects in the
elements of the filters are completely eradicated.
Furthermore, SFP200 utilizes redundant sensing of
two independent current measurement channels (with
two independent sets of sensing contact on the shunt).
The SFP200 is capable of sensing arbitrary-large volt-
age potentials in reference to the negative terminal of
the shunt. The magnitude of the sensed voltage only
depends on the capabilities of the voltage dividers
used for the purpose. Care in designing of the PCB
artwork should be exercised in order to guarantee
sufficient minimum clearance and creepage distances
between the parts of the circuit energized with high
voltage potentials; an example of such design is shown
later in this document.
19Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
PCB Artwork Design Guidelines In order to achieve minimal levels of the current offset
errors, there are specific guidelines to be followed in
the design of the artwork for the PCB.
Referring to Fig. 1 below, the copper artwork nets
between the sensing pins of the shunt (J9, J10, J11,
and J12) and the pins of the input-switching MOSFET
transistors (Q1 and Q2) must NOT have vias (plated
pass-troughs from one side of the PCB to the other).
These four (4) nets and the transistors Q1/Q2 must
be located on the same external copper layer on the
PCB, and must be routed on the same single layer, as
outlined in dashed black lines in Fig 1.
The artwork shown below resolves the whole low-level
signal chain on a single layer without the use of vias.
However, this is not strictly required, the signal nets
to the right of Q1 (to resistors R7/R6) and all nets
after that, following to OpAmp U2 and including the
circuitry around U2, can have vias without any detri-
mental effects on the circuit’s operations. The same is
true for the nets to the left of Q2 (to resistors R8/R9)
and all nets after that.
The rest of the artwork for the PCB should be designed
utilizing good practices; ground plane under the
amplifying components (shown in light blue in Fig 1),
stitching vias between the ground planes on the top
and bottom of the PCB, close location of the bypass
capacitors to their respective ICs.
The high-voltage sensing lines and associated PCB art-
work is shown below in Fig 2. Design considerations
and spacing between the connectors and between
components in this part of the circuit depend on the
level of the voltages being sensed, and on the particu-
lar safety standards followed. On the SFP200MOD
assemblies, the rating for the voltage sensing is ±1 kV
measurement range, and ±4 kV momentary overload.
As can be seen, an utmost care has been taken in order
to have the clearance and creepage distances as large
as possible; two slots have been cut into the PCB in
order to provide better creepage, with possibility to
improve clearance, if an external plastic case is de-
signed with vertical “walls” that fit into the slots.
This part of the layout does not have any copper pours
(on both sides of the PCB) in order to promote large
clearance and creepage distances; the ground planes
start just past the edge of the leftmost terminals of
the bottom resistors of the voltage dividers, where the
maximum voltage levels are already small.
Do not place any components of the voltage dividers
in the areas of the PCB that may experience flexing, as
this may degrade the sensing accuracy (due to resis-
tance changes of the SMD resistors with mechanical
stress).
The rationale for using multiple series-connected
resistors is explained in the following section of this
document describing the voltage sensing and voltage
dividers.Figure 1: Example of PCB artwork for the connection to
the shunt’s sensing pins.
20 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
For proper functioning, the SFP200 circuit requires a
galvanically isolated power supply and digital I/O.
Example of the PCB layout of the circuit implemented
on the SFP200MOD assembly is shown in Fig 3.
The clearance and creepage between the isolated parts
is 7.3 mm, mostly due to the spacing of the (SMT WB
SOIC-16) PCB footprint for the digital signal isola-
tor. The clearance between the copper pours (ground
planes) for the two isolated sections is slightly larger.
It is important not to place any copper within the
isolation gap; a specific note to the PCB fabricator
should be made, as they often place manufacturing lot
numbers and/or other data within seemingly empty
areas, on the copper layers, thus defeating the original
design intentions of keeping these areas completely
clear of the copper tracks.
For the shape of the copper pours in the lower-left
corner of Fig 3 (indicated with an arrow), the spacing
is maintained (to preserve the clearance distance) de-
spite the presence of the cut into the PCB outline (that
is made for unrelated mechanical reasons, but does
improve the creepage in that specific area).
7.3
mm
7.
3 m
m
Circuit Operations and Selection of Components
Current-sensing
Looking at the schematic of the circuitry around the
SFP200 IC, the components Q1/Q2, R6, R7, R8, and
R9 together with C2, C3, C4, C5, C6, and C7 form two
input switching circuits and two EMI/RFI RC filters.
The topology of these filters enables rejection of both
common-mode and differential-mode high-frequency
interference.
Quad OpAmp U2 with the surrounding components
R12, R13, R14, R15, R27, and R38 form the two dif-
ferential amplifiers for the two current-measurement
channels.
Figure 2: Example of PCB artwork for high voltage
sensing Figure 3: Example of PCB artwork for the galvani-
cally isolated power and digital I/O.
21Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
A local bypass capacitor (100 nF, C9) for the OpAmp
U2 must be located close to its supply pins, pin 4 and
pin 11.
As shown on the schematics, the values of the resistors
around the OpAmp U2 provide the differential gain of
201 for each of the channels. If the value of the gain
has to be changed (for example, if a different range of
currents need to be measured with the same shunt, or
a shunt with different resistance is utilized), then the
values of resistors can be adjusted, considering that
R13=R38=R14=R27 and R12=R14, and their ratio
determines the gain value. These resistors should be
1 % low-noise metal film units. The value of the dif-
ferential gain (for example, for channel 1) is equal to
[(2*R14/R15) + 1]. The maximum voltage drop across
the shunt (for the full-scale unclipped readings) mul-
tiplied by the gain should be less than approximately
4.6 V.
Resistors R1, R2, R3, and R4 provide protection of
both transistors Q1/Q2 and the pins of SFP200 IC
from the fast voltage transients or ESD overvoltages
on the shunt, as well as reduce possible contamination
of the low-level signals (via parasitic capacitances of
the transistors Q1/Q2) with digital noise originating
on the switch-control digital pins of the SFP200 IC
(pins 14, 15, 18, and 19).
Analog “Zero” Reference
The common analog “zero” reference point for the
shunt-sensing circuits is the net ZREF that provides a
potential that is roughly 1/2 of the +5 V analog supply
voltage of the SFP200 IC (VZREF≈2.5 V), as measured
in reference to net GND, that is the most-negative
supply voltage for the IC. All ground plains (copper
pours) on the board are also the part of the net GND,
however it is not a reference potential for any external
measurements.
The signal ZREF is generated on capacitor C8 with
the action of resistor R11. The values and properties
of these two components (C8 = 10 µF ±10 % X7R and
R11 = 10 k 1 %) should not be changed; there is an in-
tentional triangular waveform, roughly 100 mV pk-pk,
generated on C8 that is important for the operations
of the circuit and for improvement of the statistical
properties of the measured and reported values.
ZREF net absorbs the minute leakage currents from
the gates of transistors Q1/Q2 as well as provides
return path for the bias currents originating from the
inputs of the OpAmp U2.
In addition, capacitor C8 couples any fast transients
and ESD overvoltages from the shunt to the common
ground plane (local GND, that is the most-negative
supply voltage of the SFP200 IC).
Selecting this specific potential for the “zero” analog
reference net ZREF provides the most-advantageous
conditions for operations of the current-sense
amplifiers and of the SFP200 IC; furthermore, it
makes possible the sensing of bipolar currents and
bipolar voltages.
All measurements are done in respect to the potential
of the net ZREF; for the external (high-voltage) sens-
ing inputs the “0 V” reference is effectively the nega-
tive terminal of the shunt (that has an independent
connection to the net ZREF via the shunt’s pin J3).
However, in order to enable proper operations of the
whole SFP200 circuit, it must have galvanic isolation
from any and all potentials in the target system that is
being measured, including its own power supply rails,
system commons/grounds and CAN communications
lines.
In an isolated (floating) SFP200 circuit, there are
never any (DC) currents in the ZREF line, except for
the above-mentioned leakage and bias currents, as
22 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
well as some possible leakage current in the isolation
circuit; the total sum of these current is always less
than several microamperes (µA, 10-6 A).
Please note that the currents in the high-voltage divid-
ers flow through the dividers and exit from the shunt’s
negative terminal; again – these currents do not flow
by the way of the ZREF line to the SFP200 IC.
Voltage Sensing
In order to enable the measurements of high poten-
tials on the voltage sensing inputs, the SFP200 circuit
utilizes HV-capable voltage dividers, consisting of
resistors R16 – R22, R24 – R26, and R28 - R33;
capacitors C10 – C13 provide noise and anti-aliasing
filtering for the sensed voltages (with a time constant
of approximately 3 ms and the equivalent bandwidth
of 53 Hz at –3 dB point).
The resistors form three simple resistive dividers, with
the upper resistors of the dividers specifically made-
up from several equal units connected in series. This
follows industry practices for handling high voltage
signals, increasing the reliability, since a shorting fault
in one of the resistors will not cause a catastrophic
malfunction and/or smoke/fire. The measured voltage
divides equally among the series-connected units, al-
lowing safe operations within the continuous working
voltage capabilities of the individual low-cost resis-
tors. Alternatively, a single HV-rated resistor can be
utilized for the upper resistor in the voltage divider.
The tolerance of the resistors in the dividers does not
appreciably change the accuracy of the measurements,
since the units are calibrated on the voltage-sensing
lines (and retain calibration parameters in a nonvola-
tile memory); the initial errors due to inaccuracy of
the individual resistors are zeroed out. However, these
resistors should have reasonably good thermal stabil-
ity (i.e. low and equal TCR – Temperature Coefficient
of Resistance), and thermal tracking between the units
composing each divider (specifically between the “up-
per” resistors and the “lower” resistor, so that the divi-
sion ratio stays relatively constant with temperature).
Components R19 and C13 create a compensation
point for negation of the effects from the bias and
leakage currents that are originating at the SFP200
voltage-sensing inputs (pins 27, 28, and 29); these
components must not be removed from the design.
Temperature Measurement
Resistor R5 and NTC (Negative Temperature Coef-
ficient) thermistor TH1 create a simple circuit for
estimation of the temperature of the shunt. The small
thermistor (SMD 0402 size) is placed near (but with-
out electrical contact) to one of the shunt’s pins, as
shown in Figure 4; all the shunt’s pins have solid elec-
trical and thermal connection to the shunt, and convey
the shunt’s temperature to the immediate areas of the
PCB near the pins’ soldering sites.
Figure 4: Example of artwork for thermistor placement
on the PCB
By measuring the voltage at the junction of R5 and
TH1, the present resistance value of the thermistor is
calculated; then an application of the Steinhart–Hart
equation yields the estimated temperature of the
thermistor.
Please note that the coefficients for the Steinhart–
Hart model are specifically tailored to the particular
J2
TH1
23Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
thermistor used (Murata NCP15XH103F03RC,
a 0402-sized miniature surface-mount device,
10 k ±1 % at 25 °C and B25-50 = 3380 K ±1 %). Capacitor C1 provides filtering of the RFI/EMI.
Voltage Regulator and Reference
The analog supply voltage of the SFP200 IC is effec-
tively a Voltage Reference for all measurements. It is
important that this voltage is stable and has predict-
able behavior due to temperature changes.
Absolute initial accuracy of this voltage is not as im-
portant, as both current-measurement channels and
voltage-measurement channels are typically calibrated
at least at a single (room) temperature; all calibration
parameters are retained by the SFP200 IC indefinitely
in the dedicated nonvolatile memory and automati-
cally applied to the measurements.
Sendyne characterized a family of specific low-cost
micropower Voltage Regulator (LDO) devices for uti-
lization in the SFP200 circuit (Microchip Technology
Inc. MCP1703AT-5002E).
Please note that the supply voltage at the input of the
LDO must always be higher than the regulated output
voltage; this requires that the raw isolated power sup-
ply voltage must be higher than +5 V nominal regu-
lated operating voltage. For the LDO mentioned above
at the required supply current levels for the SFP200
circuit, the minimum headroom can be as small as
50 mV - 100 mV; however, considering the variations
of the raw isolated voltage at low operating tempera-
tures (mostly due to changes in forward-voltage-drop
of the silicon diodes), we recommend a minimum
room-temperature raw supply voltage of 5.5 V.
There is no point in providing the raw isolated voltage
of above 6.5 V; this will simply result in additional
heating without providing any benefits.
The regulated voltage from LDO supplies the digi-
tal portion of the SFP200 IC directly, utilizing both
bulk 10 µF (C23) and local 100 nF (C14/C15) bypass
capacitors; the local bypasses must be positioned close
to the respective supply pins (pin 7 and pin 41) as
shown on schematics.
The analog supply rail is developed by filtering the
digital rail through a ferrite bead with another set of
bypass capacitors, bulk 10 µF (C26) and local 100 nF
(C17); again the local bypass must be located as close
as possible to the IC (pin 8).
Isolated power supply
A DC/DC converter consisting of a driver IC U5 and
isolation transformer TX1 provides the isolated power
supply for the floating SFP200 circuit.
The whole solution was selected for the lower-price
(vs integrated AEC-Q100 qualified DC/DC and Digital
Isolator) and for the ability to reliably operate the
circuit to the temperature limits of -40 °C to +125 °C.
Specifically, ordinary silicon diodes (not the Schottky
type) are used as the full-wave rectifiers (dual-unit
D1) from the outputs of the transformer. Schottky
diodes, while providing smaller forward voltage
drop, have prohibitively high reverse leakage at high
temperatures; for a low-power circuit like the SFP200
their leakage may reach and many times exceed the
power requirements of the circuit itself, overloading
the DC/DC driver IC.
The DC/DC converter circuit is a so-called push-pull
forward architecture; is does not provide any voltage
regulation or adjustments, the ratio of input/output
voltages is fixed. A transformer with the secondary
24 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
windings that have more turns than the primaries,
provides a slight voltage step-up in order to satisfy the
requirements of the LDO, as discussed previously.
Isolated digital communications
A Digital Isolator based on the capacitively-crossed
isolation barrier (U3) provides isolation for the
buffered CAN communications signals; a CAN-rated
transceiver U4 directly interfaces to the CAN trans-
mission lines.
It is strongly recommended to include the transient-
suppressor D2 (a unit that is specifically rated for CAN
operation); it will protect from possible transients on
the CAN wires, as well as from possible ESD discharg-
es during the installation of the whole circuit.
A terminating resistor R39 of 120 Ω is connected
between the CAN lines; please assure that if several
units operate “parallel-connected” on the same CAN
branch then only a single unit from the group has the
terminating resistor.
The power supply line on the entry to the circuit is
filtered by the capacitor C31. Intentionally, this device
has the voltage rating that seems overly high; how-
ever, this is done to enable the device to survive volt-
age transients that can be present at the end of a long
cable, in a high electrical noise environment.
Supply voltage on C31 is then distributed through
current-limiting 1-Ω resistors and a ferrite bead to the
rest of the circuit.
Optional Heartbeat Indicator
It is recommended to utilize the optional Heartbeat
Indicator LEDs, at least in the initial prototyping
and testing stages. By alternatively energizing one of
the two LEDs, the IC provides a clear visual indica-
tion that the unit is powered and operating, without
requiring any information from the CAN Host or the
Sendyne GUI / Software Application. This is very use-
ful during set-up of the testing and/or calibrations.
It is recommended to design the PCB to include these
Heartbeat indicators, and simply do not populate
(DNP) their locations if they are not required; alter-
natively, two test points can be incorporated into the
design, and external “off-board” components could be
attached to provide Heartbeat functionality.
The Heartbeat drivers are on pins 16 and 17 of the IC.
They source the current (meaning the LEDs and their
current-limiting resistors would terminate into the
GND net).
These pins are typically shown as NU (Not Used)
pins on schematics, since these components are not
required for the mass-production units.
Both LEDs must be used if the Heartbeat indication
is desired; this is to make the current consumption of
the circuit constant and independent of the state of a
single LED; the alternating pattern of the LEDs
consumes a constant level of the supply current,
resulting in no variations of the supply voltage (that in
turn is used as the Reference voltage inside of the IC).
The circuit for the Heartbeat LEDs is shown in
Figure 5.
25Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Low-current LEDs. These two devices must be the same part number
GNDGND
DVSS
SFP200 IC
2.7k to 4.7kBoth resistors must have the same value
16
17
16
Figure 5: Circuit for Heartbeat LEDs
26 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Additional Documentation
― Sendyne SFP Shunt for Precision Current Measurement
― Sendyne SFP200 IC Reference Design Annotated BOM
― Sendyne SFP200 CAN 2.0B Protocol
― Simple Single Point Room Temperature Current Calibration for Systems Using the SFP200 IC
― Simple Single Point Room Temperature Voltage Calibration for Systems Using the SFP200 IC
― Notes on Automatic Calibration for Systems Using Shunts Other Than the Sendyne SFP Shunt
27Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Ordering Information
Part Number Description
SFP2001ASTZA SFP200 control IC, tray
SFP2001ASTZAR SFP200 control IC, tape and reel
28 Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Revision History
Revision Table
Revision Number Date Comments
0.1 5/26/2017 Preliminary; Initial release
29Preliminary Rev 1.0 © 2017 Sendyne Corp.
Sendyne SFP200
Information contained in this publication regarding
device applications and the like is provided only for
your convenience and may be superseded by updates.
SENDYNE MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EX-
PRESSED OR IMPLIED, WRITTEN OR ORAL,
STATUTORY OR OTHERWISE, RELATED TO THE
INFORMATION, INCLUDING BUT NOT LIMITED
TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANTABILITY OR FITNESS FOR PURPOSE.
Sendyne disclaims all liability arising from this in-
formation and its use. Use of Sendyne devices in life
support and/or safety applications is entirely at the
buyer’s risk, and the buyer agrees to defend, indemni-
fy and hold harmless Sendyne from any and all dam-
ages, claims, suits, or expenses resulting from such
use. No licenses are conveyed, implicitly or otherwise,
under any Sendyne intellectual property rights.
PatentsUS Pat. 8,264,216
US Pat. 8,289,030
US Pat. 9,052,343
US Pat. 9,588,144
Other patents pending
TrademarksThe Sendyne name and logo are registered trademarks
of Sendyne Corp.
All other trademarks mentioned herein are properties
of their respective owners.
© 2017 Sendyne Corp.
All Rights Reserved.
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