Part Number: TPS2121
In our application, IN1 (15.0VDC) serves as the main power source, while IN2 (20.0 VDC) serves as a backup. Design intent is to configure IN1 with higher priority over IN2, with OV1 and OV2 disabled.
The circuit works as expected for all switching use cases with one exception: if there are no valid inputs and IN1 is applied, there is no output until IN2 is also applied, at which point IN1 becomes the output. This failure mode is consistently reproduced, and is best captured in the following sequence of steps:
| STEP # | IN1 (VDC) | IN2 (VDC) | OUT (VDC) | ST | DESCRIPTION OF USER ACTION | RESULT |
| 1 | - | - | - | 1 | No valid inputs, no output | PASS |
| 2 | 15.0 | - | - | 1 | IN1 applied, no output | FAIL |
| 3 | 15.0 | 20.0 | 15.0 | 1 | IN2 applied in addition to IN1, output = IN1 | PASS |
| 4 | - | 20.0 | 20.0 | 0 | IN1 removed, output = IN2 | PASS |
| 5 | 15.0 | 20.0 | 15.0 | 1 | IN1 applied in addition to IN2, output = IN1 | PASS |
| 6 | 15.0 | - | 15.0 | 1 | IN2 removed, output = IN1 | PASS |
| 7 | - | - | - | 1 | IN1 removed, no output | PASS |
| 8 | - | 20.0 | 20.0 | 0 | IN2 applied, output = IN2 | PASS |
| 9 | - | - | - | 1 | IN2 removed, no output (back to Step 1) | PASS |
| 10 | 15.0 | - | - | 1 | IN1 applied, no output | FAIL |
Please advise if we overlooked something.
Regards,
AGS