Actel Power Supply Transient Evaluation on RTAX-S/SL and RTSX-SU Devices Solomon Wolday, Roopa Kaltippi, Antony Wilson September 2, 2009

Actel Power Supply Transient Evaluation on RTAX-S/SL and RTSX-SU Devices

Solomon Wolday, Roopa Kaltippi, Antony Wilson

September 2, 2009

Actel Corporation © 2009 2

Agenda

Background Experiment Vehicles

RTAX2000S and RTSX72SU Enhanced Antifuse Qualification (EAQ) design

Summary of Experiments RTAX-S/SL Summary RTSX-SU Summary

Additional Reliability Testing Conclusion


Background

Single Event Effect (SEE) events can cause momentary power supply transients on third-party RH power regulators The output of the regulator can be as high as the

regulator input The high transient voltages last for durations on the

order of microseconds This results in overstress for all devices powered by

these regulators Investigations were completed by Actel to study the

effects of the overshoots This presentation summarizes the experiments and

data collected


Experiment Vehicles

Experiments were completed on RTAX-S/SL and RTSX-SU devices Devices from multiple wafer lots were stressed thereby

eliminating process variations RTAX2000S-CQ352B

Second largest device in the RTAX-S/SL device family Same device used for the qualification of initial RTAX-S

qualification Devices programmed with the EAQ design

Design utilizes 98.6% of device logic

RTSX72SU-CQ256B The larger device in the RTSX-SU device family Same device and package used for the RTSX-SU qualification Devices programmed with EAQ design

Design utilizes 99.9% of device logic


EAQ Design Overview

Enhanced Antifuse Qualification (EAQ) design Design used for study of antifuse reliability experiment EAQ design has four different test blocks

Array Test Block(2106 bit SR) each in

4 rows of tiles

IO Test Block138 I/Os

(414 I/O Regs)

RAM Test Block(sixteen 1x16384 ram)

Delay Chain(15 X 1170 NAND)

IO_pin[0]

IO_pin[138]

15 Delay_out [5:0]

Ram out [15:0]

Ram Monitor

IO_Monitor

4

21

Array Monitor

Global Monitor

Array Monitor

Global Monitor

Error Flags [3:0]

Error Flag

Error Flag [15:0] 16


EAQ Design Overview (Cont’d)

EAQ design fully utilizes device logic Design has high perceptibility delay measurements

Multiple delay lines of combinatorial modules per device Design exercises all device features

Array test block Covers registers and combinatorial logic

I/O test block Covers both input and output buffers of each I/O

RAM test block Utilizes all SRAM blocks in the devices

All logic and I/O toggled during stress experiment


Stress Setup

Setup used to stress the RTAX-S/SL and RTSX-SU devices Setup ensures that there is no current limiting during stress Device Under Test (DUT) stressed with exact applied stress

pulse Enables flexibility to control stress amplitude and duration

Stress applied on one power supply at a time

RTAX-S/RTSX-SU

VCCA

Voffset = Vcca + Vt

Vsupply >> Vpulse

Vpulse

Vt

+

-Pulse Generator

DUT to be stressed

VCCI

RTAX-S Stress


RTAX-S/SL AC Transient Stress RTAX-S/SL nominal operating conditions

Both VCCA and VCCI/VCCDA power supplies were stressed Stress applied separately on the two power supply levels

Clocks were running at 20MHz during these experiments Functionality of devices also monitored during stress

Power Supply Nominal Level

VCCA 1.5V

VCCI 3.3V

VCCDA 3.3V

1.5V

4.0V 4.0V

2.5V100 pulses

1mS

VCCI/VCCDA

3.3V

6.0V 6.0V

2.7V100 pulses

2.5V

2.7V

1mS 1mS

1mS

VCCA


RTAX-S/SL AC Transient Stress (Cont’d)

Devices were programmed with the EAQ design All stress tests were performed at room temperature Pre and post stress functional and parametric data collected

Delta calculations performed for each parametric test 26 RTAX2000S devices were stressed with above

conditions Devices collected from 2 different wafer lots All 26 devices passed functional parametric testing No out of family delay shifts or parametric deltas were observed

Summary of test results below

Number of Device AC Stress Level Result

26 VCCA = 4.0V Pass

26 VCCI/VCCDA = 6.0V Pass


RTAX-S/SL DC Stress

Both VCCA and VCCI/VCCDA power supplies were stressed VCC increased from nominal level by increments of 0.1V

Clocks were running at 20MHz during these experiments Summary of test results shown below

VCCA1.5V

1.6V1.7V

3.5V

4 SecVCCI/VCCDA

3.3V3.4V

3.5V

5.5V

4 Sec

Functional and parametric measurements at nominal conditions


Number of Device DC Stress Level Result

26 VCCA = 3.5V Pass

26 VCCI/VCCDA = 5.5V Pass

RTSX-SU Stress


RTSX-SU AC Transient Stress RTSX-SU nominal operating conditions

Both VCCA and VCC power supplies were stressed

Clocks were running at 20MHz during these experiments Functionality of devices also monitored during stress

Power Supply Nominal Level

VCCA 2.5V

VCCI 5.0V

2.5V

5.5V 5.5V

3.0V100 pulses

1mS

VCCI5.0V

7.5V 7.5V

2.5V100 pulses

3.0V

2.5V

1mS 1mS

1mS

VCCA


RTSX-SU AC Transient Stress (Cont’d)

Devices were programmed with the EAQ design All stress tests were performed at room temperature Pre and post stress functional and parametric data collected

Delta calculations performed for each parametric test 27 RTSX72SU-CQ256 devices were stressed with above

conditions Devices collected from 3 different wafer lots All 27 devices passed functional parametric testing No out of family delay shifts or parametric deltas were observed

Summary of test results below

Number of Device AC Stress Level Result

27 VCCA = 5.5V Pass

27 VCCI = 7.5V Pass


RTSX-SU DC Stress

Both VCCA and VCCI power supplies were stressed VCC increased from nominal level by increments of 0.1V

Clocks were running at 20MHz during these experiments Summary of test results shown below

Number of Device DC Stress Level Result

27 VCCA = 4.5V Pass

27 VCCI = 6.5V Pass

VCCA2.5V

2.6V2.7V

4.5V

4 SecVCCI/VCCDA

5.0V5.1V

5.2V

6.5V

4 Sec




Additional Reliability Testing

All devices in the preceding experiments were then

processed through Group C life test To understand long term reliability concerns

Dynamic programmed burn-in at maximum specified VCC conditions

Group C experiments completed with 1000hrs burn-in at

ambient temperature of 125°C

Functional and parametric data analysis completed at

168hrs and 500hrs pull-points

All devices passed functional and parametric tests No out of family deltas or parametric shifts were observed


RTAX-S/SL and RTSX-SU Damage Levels

Additional experiments were completed to determine voltage levels at which permanent damage occurs

Damage was only possible with DC stress AC transient stresses were not able to cause damage with available setup Damage only occurred on VCCA supplies

Permanent damage levels

ICC increase and functional failures were observed at damage levels

DeviceVCCA Nominal

LevelDamage

Level

RTAX-S/SL 1.5V 5.0V

RTSX-SU 2.5V 6.0V


Conclusion

Devices were stressed beyond their absolute maximum rated conditions using DC and AC stress

Outcome of the study indicates RTAX-S/SL and RTSX-SU devices are robust and reliable RTAX-S/SL devices withstood AC transients exceeding nominal

voltages by 1.8X on VCCI/VCCDA and 2.6X on VCCA

RTSX-SU devices withstood AC transients exceeding nominal voltages by 1.5X on VCCI and 2.2X on VCCA

Customers are still advised against stressing beyond the conditions outlined in the datasheet

The RTAX-S and RTSX-SU are designed to withstand high voltages applied during programming Far more tolerant to voltage overshoots than other technologies

Documents

Actel Power Supply Transient Evaluation on RTAX-S/SL and RTSX-SU Devices Solomon Wolday, Roopa Kaltippi, Antony Wilson September 2, 2009