ZHCSOF5A May 2022 – September 2022 TPS25985
PRODUCTION DATA
The SWEN pin is a signal which is driven high when the FET must be turned ON. When the SWEN pin is driven low (internally or externally), it signals the driver circuit to turn OFF the FET. This pin serves both as a control and handshake signal and allows multiple devices in a parallel configuration to synchronize their FET ON and OFF transitions.
Device State | FET Driver Status | SWEN |
|---|---|---|
Steady-state | ON | H |
Inrush | ON | H |
Overtemperature shutdown | OFF | L |
Auto-retry timer running | OFF | L |
Undervoltage (EN/UVLO) | OFF | L |
Undervoltage (VDD UVP) | OFF | L |
Undervoltage (VIN UVP) | OFF | L |
Insertion delay | OFF | L |
Overvoltage lockout (VIN OVP) | OFF | L |
Transient overcurrent | ON | H |
Circuit-breaker (persistent overcurrent followed by ITIMER expiry) | OFF | L |
Fast-trip | OFF | L |
Fault response mono-shot running (MODE = GND) | OFF | L |
Fault response mono-shot expired (MODE = GND) | ON | H |
ILM pin open (start-up) | OFF | L |
ILM pin short (start-up) | OFF | L |
ILM pin open (steady-state) | OFF | L |
ILM pin short (steady-state) | OFF | L |
FET health fault | OFF | L |
The SWEN is an open-drain pin and must be pulled up to an external supply.
In a primary + secondary parallel configuration, the SWEN pin is used by the primary device to control the on and off transitions of the secondary devices. At the same time, it allows the secondary devices to communicate any faults or other condition which can prevent it from turning on to the primary device. Refer to Fault Response and Indication (FLT) for more details.
To maintain state machine synchronization, the devices rely on SWEN level transitions as well as timing for handshakes. This ensures all the devices turn ON and OFF synchronously and in the same manner (for example, DVDT controlled or current limited start-up). There are also fail-safe mechanisms in the SWEN control and handshake logic to ensure the entire chain is turned off safely even if the primary device is unable to take control in case of a fault.
TI recommends to keep the parasitic loading on the SWEN pin to a minimum to avoid synchronization timing issues.