Part Number: TCAN1146-Q1
Hi Team,
below a request by our customer. We'll provide schematics, scope shots and detailed description:
We have observed that if VSUP does not fall below a certain voltage level before the next power-on cycle, the next power-on sequence does not take effect: INH does not switch to HIGH, and consequently the system does not power up as expected.
We are currently investigating the conditions under which this behavior occurs and would like to understand the expected behavior of the TCAN1146 in this situation.
Some observations from our measurements:
- During the power-off sequence, VSUP decreases gradually and can remain at a residual voltage level before the next power-on cycle.
- If the next power-on cycle occurs while VSUP is still above a certain level, INH remains LOW.
- If VSUP is allowed to discharge further before the next power-on cycle, INH switches HIGH and the system starts normally.
- Therefore, the behavior appears to be dependent on the VSUP voltage reached during the previous power-off cycle.
We also noticed that the TCAN1146 datasheet, in Table 8.6 – Supply characteristics, specifies the following thresholds.
Based on these specifications, we would like to better understand how these thresholds interact with the INH behavior and the power-on detection mechanism.
In particular, could you please clarify:
- Which of these thresholds is relevant for ensuring that a subsequent power-on event can activate INH?
- Is the TCAN1146 expected to recognize a new power-on cycle if VSUP has not fallen below VSUP(PU)F during the previous power-off sequence?
- Is there an internal state or condition that needs to be reset before INH can be asserted again?
- Are there any TCAN1146 configuration options or recommended hardware measures that could improve the robustness of this behavior?
Best
Khai
