(1/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

PSI tests - Comparator Results

• Devices under test and beam conditions

• Schematics

• Results

o Input bias current

o Output drift

o I-V acquisition of the comparator outputs

o Gain

o Response time

o SET

(2/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Devices under test and beam conditions

• DUT

o LM339D, LP339M and LM139:

SET

o LM339D and LP339M

Input bias measurements

o LM339D:

Output drift

I-V acquisition of the comparator outputs

Gain

Response time

• Beam conditions:

o PIF facility at PSI Proton energy was set to 230 MeV

Dose rate : 7.5 rad/s (270 Gy/h)

(3/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Schematics

Board name

V+/V- (V)

Vin (mV)

outmA)

LM339D +/-15 50 18.75

LM339P +/-15 15 18.75

LM139 +/-15 50 18.75

SET evaluation

• From literature, the lowest ΔVin gives the highest chance to get SETs

(4/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Schematics

Input bias current

Board name

V+/V- (V)

Negative input (V)

outmA)

LM339D +/-15/(0-34) +7.5/(+17) 18.75/(21.25)

LM339P +/-15/(0-34) +7.5/(+17) 18.75/(21.25)

(5/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Schematics

Output drift / Response time / Gain / I-V measurements

• 4 kinds of measurements performed:

• Output drift by applying a constant V(-) during irradiation

• During test breaks:

Gain by applying a saw tooth at V(-)

Response time by supplying V(-) with a square wave

I-V curves by using a Source Measure Unit (Keithley)

(6/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Input Bias Current

• 1st Run • Up to 80 Gy • Vin > 0• V(-) = 7.5V• I(+) = 75 nA → V(+) = 7.5 V

• At 80 Gy run was stopped• Change supply voltage from:

• +/- 15V to 0/34V

• LM339D

(7/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Input Bias Current

• 2nd Run

• Vin > 0• V(-) = 17V• I(+) = 170 nA → V(+) = 17 V

• At ≈ 155 Gy → I(+)max is exceeded (250 nA)

(8/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Input Bias Current

• LP339M

• At ≈ 57 Gy → I(+)max is exceeded (25 nA)

(9/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Output Drift

• LM339D • Voutinit set to –Vcc (-15V)

• Test break :

• Other measurements (Gain etc…)

• Trend of the Vout variation vs

dose:

• Vout tends to lower values

• From 0 to 300Gy:

• Vout drifted from:

-14.927 V to -14.895 V (32 mV)• Can be assumed as very small

• Datasheet affords no information

concerning the allowed drift

(10/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

I-V measurements of the comparator outputs

• LM339D

• Test break :

• I-V measurements

• Source-Measure Unit (Keithley)

• Inject I and measure Vout

(11/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

I-V measurements of the comparator outputs

• LM339D • A trend of the output is observable:

o I-V curves → Lower values of Ic vs

Dose

Active field of the transistor

Breakdown

• Reasons:

o β (output transistor) decreased

o Current source is damaged

(12/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Gain

• Test break :

• V(-) → Sawtooth waveform ΔV = 10mV

• V(+) → Ground

(13/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Gain

• Specifications:Gainmin = 50V/mV

• Gain of the 2 irradiated comparators decrease vs dose

• Variation of the reference Gain is due to the limited resolution of the scope to measure Vin.

• The increase of Vin is due to the input offset

• As dose increases, ΔVin increases to change the output state→ Low resolution is less dominant

• Switching voltage increases with dose.

(14/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Response time

• A step from -100mV to +100mV was applied on V(-).

• Results show that response time increases vs dose with respect to the reference:

• Rising time can be acceptable depending on the application

o 50% after a TID of 150 Gy (from 2.1 µs to 3 µs)

o 220% after a TID of 300Gy (from 2.1 µs to 4.75 µs)

(15/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Summary of the Results

Test type Comparator type Limit TID (Gy) Corresponding Fluence(p+ 230MeV/cm2)

Comments/observations

Input bias current LM339D 155 2.9×1011 Input bias current increases vs TID.

LP339M is the more sensitive

LP339M 56 1.04×1011

Gain LM339D 100 1.87×1011 Gain decreases vs TIDThe gain value can be accepted depending on the application

I-V curves LM339D No indication in the Datasheet

No indication in the Datasheet

I-V curves drift to lower values of I as TID increases.

β of the output transistor and/or a current source inside the comparator is affected by radiation.

Output drift LM339D No indication in the Datasheet

No indication in the Datasheet

From 0 to 300 Gy Vout drifts by 32mV toward lower values

Response time LM339D No indication in the Datasheet

No indication in the Datasheet

Tr increases vs TIDThe Tr value can be accepted depending on the application• The analysed parameters show a degradation. In some cases the datasheet limit is exceeded

(16/16)08/05/12 – RadWG meetingG. Spiezia, P. Peronnard, E. Lefteris, P. Oser, J. Mekki

Conclusions

• No SET (>15 ns and > 100 mV) have been observed for any of the DUTs.

• The analysed parameters show a degradation

• In some cases the datasheet limit is exceeded as shown in the previous table

• The degradation can be tolerated depending on the application