M3TEK Preliminary Datasheet MT3123/MT3123A · PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Input Voltage Range V IN 2.5 6 V Shutdown Current V EN = 0V, V IN = 5.5V 0.1 1 µA Input Under

M3TEK Preliminary Datasheet MT3123/MT3123A

5V 4A 1.25MHz 15µA Low Iq FAST-PWM Synchronous Step-Down Converter

Rev. 0.4 M3tekic Confidential 1 www.m3tekic.com

DESCRIPTION

The MT3123/MT3123A is a 4A high efficiency

constant on-time controlled synchronous step-

down converter. It operates with input voltage from

2.5V to 6V and provide output range from 0.6V to

as high as input level, thanks to its 100% duty cycle

operation. Its advanced constant on-time control

Fast-PWM scheme simplifies loop compensation

and offers excellent load transient response while

maintaining a relatively constant 1.25MHz

switching frequency. MT3123/MT3123A consumes

extremely low 15µA quiescent current hence

achieves superior light load efficiency. The high

gain error amplifier in the control loop provides

excellent load and line regulation. For fault tolerant

operation, MT3123/MT3123A has cycle-by-cycle

current limit protection and hiccup mode for short

circuit or over-load condition.

MT3123/MT3123A is available in QFN3x3mm

package and ideal for high performance, portable

applications.

FEATURES

Wide Input Range from 2.5V to 6V

High Efficiency up to 97%

Output Voltage as low as 0.6V

100% Duty Cycle Operation

+/-1.5% 0.6V Feedback Voltage Accuracy

1.25MHz Pseudo Constant Switching Frequency

15µA Quiescent Current

Continuous Output Current up to 4A

Built-in 48mΩ HS and 38mΩ LS Power Switches

Cycle-by-cycle Current Limit Protection

Hiccup Mode for Short Circuit and Over-Load

Protection

Open Drain Power Good Indication with Internal Pull-

up Resistor

Thermal Shutdown Protection

Stable with low ESR ceramic Output Capacitors

Available in a Small QFN3x3mm_16L Package

Pb-Free RoHS Compliant

APPLICATIONS

Solid-State and Hard Disk Drives

Portable / Handheld Devices

WiFi Moudule, Set-top Boxes

DC/DC Micro Modules

TYPICAL APPLICATIONS

AVIN

PVIN1

PVIN2

ENAGND

SW1

SW2

OUTPG

MT3123

MT3123A

22uF

VIN

2.5V~5.5V

1uH

VOUT

3.3V

CIN

L

10uFx2

COUT10R

0.1uF

PGND1

PGND2

PG

10K

0.1uF

EN

FB

196KR1

43.2K

R2

CFFOptionSS*

*Option for MT3123A

70%

75%

80%

85%

90%

95%

100%

0.001 0.01 0.1 1

Iout (A)

Efficiency

5Vin 3.3Vo5Vin 2.5Vo5Vin 1.8Vo5Vin 1.2Vo




Ordering Information

Part No. Marking Temp. Range Package MOQ

MT3123NQAR MT3123

YWWxx -40°C ~ 85°C QFN3X3_16L 5,000/Reel

MT3123AQAR 3123A

YWWxx -40°C ~ 85°C QFN3X3_16L 5,000/Reel

Note: Y: Year, WW: Week

PIN CONFIGURATION

1

4

3

2

SW

EPPVIN

NC

AVIN

16

5 6 7 8

9

10

11

12

15

14

13

SW

NC

PG

FB

AG

ND

NC

NC

PVIN

EN

PG

ND

PG

ND

OU

T

1

4

3

2

SW

EPPVIN

SS

AVIN

16

5 6 7 8

9

10

11

12

15

14

13

SW

NC

PG

FB

AG

ND

NC

NC

PVIN

EN

PG

ND

PG

ND

OU

T

MT3123 MT3123A

QFN3x3_16L TOP VIEW

Pin Description

PIN NAME MT3123

PIN NO.

MT3123A

PIN NO. DESCRIPTION

SW 1, 2 1, 2 Switching pin, connect to external inductor

NC 3, 7, 8, 9 3, 7, 8 No connection, Leave float

PG 4 4 Open-drain power good indication.

FB 5 5 Feedback voltage input, connect to external feedback resistors

AGND 6 6 Analog ground

SS - 9

Soft-start programming pin. Do not float this pin. Connect a capacitor

from this pin to ground to program the soft-start time.

TSS=Max(CSS×0.6V/1.6μA, 60μs)

AVIN 10 10 Analog Input supply voltage

PVIN 11, 12 11, 12 Power Input supply voltage

PGND 14, 15, EP 14, 15, EP Power ground

EN 13 13 Enable input, Integrated 1MΩ pull down resistor.

OUT 16 16 Output voltage sense




Absolute Maximum Rating (Reference to GND) (Note1)

SW to PGND …..…………….....……......… -0.5V to VOUT+1V

VIN/PVIN to AGND ……..………….....………….. -0.3V to 6V

PGND to AGND …………………………………. -0.3V to 0.3V

EN, OUT, FB, PGOOD to AGND ..……….……... -0.3V to 6V

ESD …………………………………………...……….. Class 2

Lead Temperature( Soldering 10s) ……………..…… 260°C

Junction Temperature Range …………..….. -40°C to 150°C

Storage Temperature Range …………........ -65°C to 150°C

Recommend Operating Conditions (Note2)

Input Voltage (VBAT) …………..…….…..……… +2.4V to 5.5V

Output Voltage (VOUT) ………..………..………… +0.6V to VIN

Operating Temperature Range …………..….. -40°C to 85°C

Junction Temperature Range, TJ ………...…..……. <.135°C

Thermal information (Note3, 4)

Maximum Power Dissipation (TA=25°C) QFN3x3_16 ..... 2W Thermal Resistance (θJA) QFN ………...…..………. 50°C/W

Thermal Resistance (θJC) QFN ………...….....……. 7.8°C/W

Note(1): Stress exceeding those listed “Absolute Maximum Ratings” may damage the device.

Note(2): The device is not guaranteed to function outside of the recommended operating conditions.

Note(3): Measured on JESD51-7, 4-Layer PCB.

Note(4): The maximum allowable power dissipation is a function of the maximum junction temperature TJ_MAX, the junction to

ambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any

ambient temperature is calculated by PD_MAX= (TJ_MAX-TA)/θJA. Exceeding the maximum allowable power dissipation will cause

excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device

from permanent damage.

Electrical Characteristics

TA = 25°C, VIN=5V, unless otherwise noted.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Input Voltage Range VIN 2.5 6 V

Shutdown Current VEN = 0V, VIN = 5.5V 0.1 1 µA

Input Under Voltage Lockout Threshold VIN Increasing 2.3 2.4 2.5 V

Input Under Voltage Lockout Hysteresys 250 mV

Quiescent Current IQ VFB = 0.63V, OUT float 15 18 µA

Feedback Voltage VFB 591 600 609 mV

Feedback Current IFB 1 nA

Oscillator Frequency IOUT=500mA 1.25 MHz

HS Switch Current Limit 5 6 A

HS Switch On Resistance 48 mΩ

LS Switch On Resistance 38 mΩ

HS Leakage Current VIN = 5.5V, VEN = VSW = 0V 0.1 1 µA

LS Leakage Current VIN = VSW = 5.5V, VEN = 0V 0.1 1 µA

On-time for HS Switch VIN = 5V, VOUT = 1.2V 200 ns

VIN = 5V, VOUT = 3.3V 530 ns

PGOOD Output Low Voltage VFB =0.5V, sink 1mA 0.2 V

PGOOD Output Leakage Current VFB = 0.63V , VPGOOD = VIN = 5.5V 10 nA




PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

PGOOD Over Voltage Rise Threshold VFB with ramp from over voltage +8 +10 +12 %

PGOOD Over Voltage Fall Threshold VFB ramp up from regulation +15 %

PGOOD Under Voltage Rise Threshold VFB with ramp up from under voltage -12 -10 -8 %

PGOOD Under Voltage Fall Threshold VFB ramp down from regulation -15 %

PGOOD Delay PGOOD going High to Low 25 µs

PGOOD Pull-up resistor 0.8 1 1.2 MΩ

EN On Threshold 1.0 V

EN Off Threshold 0.5 V

EN Internal Pull Down Resistor 0.8 1 1.2 MΩ

Internal Soft Start Time, MT3123 600 µs

Soft Start Current, MT3123A TSS=Max(CSS×0.6V/1.6μA, 60μs) 1.6 µA

Soft Start Time, MT3123A CSS=1nF 400 µs

Thermal Shutdown 160

Thermal Shutdown Hysteresis 30

Functional Block Diagram

V060

FB

Control

Logic

ILIMTOUT

0.66V

0.54V

0.54V < FB < 0.66V

AIN

AIN

SW

V054

V066

V060

VREFSS

VREFSS EA

UVLO

&

Bandgap

0.60V

0.54V

0.66V

VREFSS

OVLD

ILIMT

VFB

EN

AGND

PVIN

PGND

Soft-Start

Modulation Ramp

Constant

On-time

ON

VIN

VOUT

TON

VIN

Current Limit

&Over-load Detection

HSON

LSON

PG




TYPICAL PERFORMANCE CHARACTERISTICS

(CIN=10uF, COUT = 10uFx2, L=1uH, TA =25 )

Steady State Test

Vin=5V, Vout=1.2V, Iout=0A

CH1:SW CH2:VOUT CH3:VIN CH4:IL

Steady State Test

Vin=5V, Vout=1.2V, Iout=3.5A


Load Transient Response

Vin=5V, Vout=1.2V, Iout=1.5A to 3A

CH1:VOUT CH2:IL

Vin Power On



Vin Power Off



EN On


CH1:SW CH2:VOUT CH3:EN CH4:IL

Vin Power On



Vin Power On



EN Off






TYPICAL PERFORMANCE CHARACTERISTICS

(CIN=10uF, COUT = 10uFx2, L=1uH, TA =25 )

EN On



EN Off



Short Circuit Entry



Short Circuit Recovery






OPERATION

MT3123/MT3123A is a constant on-time controlled synchronous step-down converter that offers excellent transient

response over a wide range of input voltage. It achieves superior light-load efficiency with extremely low quiescent

current.

FAST-PWM CONSTANT ON-TIME CONTROL

MT3123/MT3123A employs advanced constant on-time control (Fast-PWM) to achieve superior transient response.

The Fast-PWM constant on-time control turns on HS immediately when FB droops below reference. The HS is

turned on for a pre-determined period (on-time) to ramp up the inductor current, and then the LS will be turned on

to ramp down the inductor current. The cycle repeats itself if FB droops below reference again. MT3123/MT3123A

uses adaptive on-time based on input and output voltage level to achieve a relatively constant switching frequency.

The on-time can be estimated as:

TON =VOUT

VIN

∙ 0.833μ

Due to its immediate response on FB voltage droop and simplified loop compensation, Fast-PWM constant on-time

offers a superior transient response compare to traditional fixed frequency PWM control step-down converters.

LIGHT LOAD OPERATION

In light load condition where the switcher operates in discontinuous mode, MT3123/MT3123A cuts down its

quiescent current to as low as 15uA, thus achieve excellent light load efficiency.

ENABLE

When input voltage is above the under voltage lock-out threshold, MT3123/MT3123A can be enabled by pulling the

EN pin to above 1V. MT3123/MT3123A will be disabled if the EN pin is kept below 0.5V.

SOFT START

MT3123 has built-in 600µs soft-start timer. During the soft start period, output voltage is ramped up linearly to the

regulation voltage, independent of the load current level and output capacitor value. MT3123A provides an external

soft-start pin that gradually raises the output voltage. The soft-start time can be programmed by the external

capacitor across SS pin and GND. The chip provides a 1.6μA charge current for the external capacitor, It is not

recommended to leave SS pin, The soft start time is calculated as:

TSS = Max ( CSS∙0.6V

1.6μ𝐴 , 60μs )

CURRENT LIMIT and HICCUP MODE

MT3123/MT3123A has cycle-by-cycle HS current limit protection to prevent inductor current from running away.

Once HS current limit is triggered, MT3123/MT3123A will turn on LS and wait for the inductor to drop down to a

pre-determined level before the HS can be turned on again. If this current limit condition is repeated for a sustained

long period of time, MT3123/MT3123A will consider it as over-load or short circuit. Either way, MT3123/MT3123A

will enter hiccup mode, where it stop switching for a pre-determined period of time before automatically re-try to

start up again. It always starts up with soft-start to limit inrush current and avoid output overshoot.




POWER GOOD INDICATION

MT3123/MT3123A has open drain PGOOD indicator with internal 1MΩ pull-up resistor to input voltage. PGOOD

will be pulled up if output voltage is within +/-10% of regulation, otherwise PGOOD is pulled down by the internal

NMOS.

APPLICATION INFORMATION

Setting the Output Voltage

External feedback resistors are used to set the output voltage. Refer to typical application circuit on page 1, the top

feedback resistor R2 has some impact on the loop stability, so its recommended range is below 100kΩ. For any

chosen R2, the bottom feedback resistor R1 can be calculated as:

VOUT = VREF ∙ (R1

R2

+ 1) , thus R1 = R2 ∙ (VOUT

0.6− 1)

Inductor Selection

The recommended inductor value for MT3123/MT3123A is between 0.68uH to 4.7uH. Usually the inductor value is

chosen to satisfy a desired ripple current:

L =VOUT ∙ (VIN − VOUT)

VIN ∙ fSW ∙ ∆I

Where ∆𝐼 is the inductor ripple current.

With the chosen ∆𝐼, the peak inductor current will be:

IPK = ILOAD +1

2∙ ∆I

Input Bypass Capacitor Selection

The input current to the step-down converter is discontinuous with very sharp edges, therefore an input bypass

capacitor is required. For best performance, it’s recommended to use low ESR ceramic capacitors and place them

as close to the input pin as possible. For lowest temperature variations, use X5R or X7R dielectric ceramic

capacitors. The RMS current of the input capacitor is approximately:

ICIN_RMS = IOUT√D(1 − D)

From the equation, it can be seen that the highest RMS current occurs when D is 0.5:

ICIN_RMS =1

2IOUT

Choose the capacitor with RMS current rating higher than 1/2 IOUT, The power dissipation on the input capacitor

can be estimated with the RMS current and the ESR resistor.

Electrolytic or tantalum capacitors can also be used, but due to their significantly higher ESR, a small size ceramic

capacitor should be placed as close to the IC as possible.

The voltage ripple on the input capacitor, neglecting the ESR impact, can be calculated as:

∆VCIN =ILOAD

fSW ∙ CIN

∙VOUT

VIN

∙ (1 −VOUT

VIN

)




Output Capacitor Selection

An output capacitor is required to obtain a stable output voltage. To minimize the output voltage ripple, ceramic

capacitors should be used, and the ripple voltage can be estimated as:

∆VOUT =1

8∙ (1 −

VOUT

VIN

) ∙VOUT

L∙

1

(fSW)2 ∙ COUT

If electrolytic or tantalum capacitors are used, the ESR will dominate the output voltage ripple:

∆𝑉𝑂𝑈𝑇 = (1 −𝑉𝑂𝑈𝑇

𝑉𝐼𝑁

) ∙𝑉𝑂𝑈𝑇

𝑓𝑆𝑊 ∙ 𝐿∙ 𝑅𝐸𝑆𝑅

AVIN Bypass Cap

Recommend a R-C filter 10Ω and 0.1uF for AVIN when IOUT >3A.

AVIN

PVIN1

PVIN2

EN

AGND

SW1

SW2

OUT

FBPG

MT3123

VIN

2.5V~5.5V

1uH

100k

VOUT

1.2V

CIN

L

R1

100k

R2

COUT

0.1uF

PGND1

PGND2

PG

10K

0.1uF

EN

AVIN

PVIN1

PVIN2

EN

AGND

SW1

SW2

OUT

FBPG

MT3123

VIN

2.5V~5.5V

1uH

100k

VOUT

1.2V

CIN

L

R1

100k

R2

COUT

10R

0.1uF

PGND1

PGND2

PG

10K

0.1uF

EN

Iout < 3A Iout > 3A

PCB Layout Recommendation

Proper layout and component placement are very important, and sometimes critical for the step-down converters.

The PCB can radiate excessive noise and contribute to converter instability with improper layout.

Certain points must be considered before starting a layout using the MT3123/MT3123A.

Use wide trace for the high current paths, the traces of the high current paths as short and wide as possible.

Place the input capacitor CIN close to pin11,12 (PVIN) and pin14,15 (PGND), so the total PCM trace from the

pins to CIN capacitor is minimized.

SW pin and the trace will be the most noisy signal on the board, so proper isolation between SW from FB is

essential, SW node encounters high frequency voltage swings so it should be kept in a small area.

Ensure all feedback network connections are short and direct. Place the feedback network as close to the

chip as possible.

Components away from the SW node to prevent stray capacitive noise pick-up.

The GND pin and Exposed Pad should be connected to a strong ground plane for heat sinking and noise

protection.

An example of PCB layout guide is shown in below Figure for reference.




PACKAGING INFORMATION

QFN 16L 3mmx3mm PACKAGE OUTLINE DIMENSIONS

D

E

D1

E1

L

b

A

A1

e

DETAIL A

SYMBOLS MILLIMETERS INCHES

MIN. MAX. MIN. MAX.

A 0.70 0.80 0.028 0.031

A1 0.00 0.05 0.000 0.002

b 0.18 0.30 0.007 0.012

E 2.90 3.10 0.114 0.122

D 2.90 3.10 0.114 0.122

D1 1.70 0.067

E1 1.70 0.067

e 0.50 0.020

L 0.30 0.50 0.012 0.020




Carrier Tape & Reel Dimensions

1. Orientation / Carrier Tape Information :

AB

C

D

Feeding direction

2. Rokreel Information :

3. Dimension Details :

PKG Type A B C D E F Q'ty/Reel

Q(D)FN 3x3 4.0 mm 1.5 mm 12.0 mm 8.0 mm 13 inches 13.0 mm 5,000




Reflow Profile

Classification Of IR Reflow Profile

Reflow Profile Green Assembly

Average Ramp-Up Rate (Tsmin to Tp) 1~2/second, 3/second max.

Preheat & Soak

-Temperature Min(Tsmin)

-Temperature Max(Tsmax)

-Time(tsmin to ts tsmax)

150

200

60~120 seconds

Time maintained above:

-Temperature(TL)

-Time(tL)

217

60~150 seconds

Peak Temperature(Tp) See Classification Temp in table 1

Time within 5 of actual Peak Temperature(tp) 30 seconds max.

Ramp-Down Rate 6/second max.

Time 25 to Peak Temperature 8 minutes max.

* Tolerance for peak profile Temperature (Tp) is defined as a supplier minimum and a user maximum. ** Tolerance for time at peak profile temperature (tp) is defined as a supplier minimum and a user maximum.

Table 1. Pb-free Process – Classification Temperatures (Tc)

Package Thickness Volume mm

3

<350

Volume mm3

350-2000

Volume mm3

>2000

<1.6 mm 260 260 260

1.6 mm – 2.5 mm 260 250 245

2.5 mm 250 245 245

Note: For all temperature information, please refer to topside of the package, measured on the package body surface.

Documents

M3TEK Preliminary Datasheet MT3123/MT3123A · PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Input Voltage Range V IN 2.5 6 V Shutdown Current V EN = 0V, V IN = 5.5V 0.1 1 µA Input Under