SLVSHA1 September 2024 TPS1685
ADVANCE INFORMATION
This pin can be used to configure the TPS1685x as a primary device in a chain along with other TPS1685x eFuses, designated as secondary devices. This feature allows some of the TPS1685x pin functions to be changed to aid the primary + secondary parallel connection.
This pin is sampled at power up. Leaving the pin open configures it as a primary or standalone device. Connecting this pin to GND configures it as a secondary device.
The following functions are disabled in secondary mode and the device relies on the primary device to provide this functionality:
IREF internal current source
DVDT internal current source
Overcurrent detection in steady-state for circuit-breaker response
PG de-assertion (pulldown) after reaching steady-state
Latch-off after fault
In secondary mode, the following functions are still active:
Overtemperature protection
Start-up current limit
Active current sharing during inrush as well as steady-state
Analog current monitor (IMON) in steady state
Steady-state overcurrent detection based on IMON. This is indicated by pulling ITIMER pin low internally, but does not trigger circuit-breaker action on ITIMER expiry. Rather, it relies on the primary device to start its own ITIMER and then trigger the circuit-breaker action for the whole chain by pulling SWEN low after the ITIMER expiry. However, the secondary devices use an internal overcurrent timer as a backup in case the primary device fails to initiate circuit-breaker action for an extended period of time. Refer to Single Point Failure Mitigation section for details.
Each device still has individual scalable and fixed fast-trip thresholds to protect itself. The individual short-circuit protection threshold is set to higher values in secondary mode so that the primary device can lower it further for the whole system.
Individual OVP is set to maximum in secondary device so that the primary can lower it further for the whole system.
FLT assertion based on individual device fault detection (except circuit-breaker).
PG de-assertion control during inrush and assertion control after device reaches steady state. However, after that in steady state, the secondary device no longer controls the de-assertion of the PG in case of faults.
SWEN assertion or de-assertion based on internal events as well as FET ON and OFF control based on SWEN pin status.
In secondary mode, the device behavior during short-circuit and fast-trip is also altered. More details are available in the Short-Circuit Protection section.