OPA2377-Q1: One abnormal Vos shifting of OPA2377-Q1 was observed at ambient (25℃, 50%RH) condition, how could this happen?

Hi there,

OPA2377-Q1 was used in one of our vehicle level project and we observed an abnormal Vos shifting. Hopefully we can get some support here.

Vos of OPA2377-Q1 was supposed to way less then 1mV according to datasheet.

• V_tp223 = Vcc · R207 / (R207 + R203) = 3.75mV；
• V_tp223 - V_tp226 ≤ 1mV (typical 0.25mV) 
• Gain_a = R202 / R201 = 66.7

And therefore V_tp227 is supposed to equal to 3.75mV * 66.7 = 250mV, and which it is, based on 5,000 samples test data.

However we found out one abnormal sample, V_tp227 = 255mV when first tested, and it changed to ~140mV after a couple of days without any operation.

And we tested some voltage level in this abnormal sample, which leads to an guess that Vos of this OPA was shifting somehow.

• V_tp223 ≈ 3.7mV；
• V_tp226 ≈ 2.1mV；

Can I get some professional opinion that what could cause this phenomenon? And how can we detect & prevent it.

Thanks in advance.

Yang Fan.