TPS65185: VEE Output is abnormal after stress test

Hirotsugu Kobayashi

Mastermind 9540 points

Part Number: TPS65185

Hi, team.

A high-humidity/temperature test was performed by equipment with TPS65185.

The output voltage of VEE was -27V abnormally, therefore VEE_FB is about 1.3 V.

Where would it be broken?

over 7 years ago

0 Richard Solarski over 7 years ago

TI__Genius 10885 points

Kobayashi-san,

This device implements a large feedback divider, was 1.3V confirmed at VEE_FB to exclude variations from the external resistors?

Was VEE the only regulator affected?

Best Regards,
Rick S.

0 Hirotsugu Kobayashi over 7 years ago in reply to Richard Solarski

Mastermind 9540 points

Rick-san,

The resistance value is 1 MΩ and 52.3 kΩ and there are the 1% precision.
The resistator's were removed from boad and checked.
There is no abnormality in the resistance value.

Only VEE is abnormal, other outputs are normal.

Is it possible that only the reference voltage of VEE becomes abnormal?

Best Regards,
Kobayashi

0 Richard Solarski over 7 years ago in reply to Hirotsugu Kobayashi

TI__Genius 10885 points

Kobayashi-san,

Can you clarify if the device now regulates at -27V at room temperature, or if the device temporarily reached -27V during the HTOL tests? Were they able to confirm the voltage on VEE_FB while operating? How many devices have this behavior?

It should be very unlikely for only the negative charge pump reference to be affected.

Best Regards,

Rick S.

0 Hirotsugu Kobayashi over 7 years ago in reply to Richard Solarski

Mastermind 9540 points

Rick-san,

VEE is -27V at room temperature.
VEE_FB was checked in operating.
Stress testing is only one.

This phenomenon was confirmed after operating on for 72 hours by 40 ℃ of temperature and 80 % of humidity.
What kind of stress testing do you make this device?

Best Regards,

0 Richard Solarski over 7 years ago in reply to Hirotsugu Kobayashi

TI__Genius 10885 points

Kobayashi-san,

The reliability testing page lists the standards used for the device qualification tests: www.ti.com/.../reliability_testing.page

Devices are tested at high temperatures, but from my understanding the device might not be operating during moisture or humidity tests. The most relevant test would follow JESD22-A110.

We would need to initiate a failure analysis to find out exactly how the device is damaged: www.ti.com/.../failure_analysis.page

Best Regards,
Rick S.

0 Hirotsugu Kobayashi over 7 years ago in reply to Richard Solarski

Mastermind 9540 points

Rick-san,
The maximum output current value of VEE is 12mA.
When any more current is flowed, is there a possibility that CP2 breaks?
Does CP2 have a current limit protection?

Best Regards,

0 Hirotsugu Kobayashi over 7 years ago in reply to Hirotsugu Kobayashi

Mastermind 9540 points

Does CP2 have a current limit protection?

0 Richard Solarski over 7 years ago in reply to Hirotsugu Kobayashi

TI__Genius 10885 points

Kobayashi-san,

Both charge pumps have internal current limits, and I cannot determine how an overcurrent condition could lead to the behavior described.

Best Regards,

Rick S.

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TPS65185: VEE Output is abnormal after stress test