Improvised Diagnostic Strategy for High-Side Switch Power-Stage

A vehicle electronic control unit consists of various high side power stages for driving different loads. Common faults such power stages experience are Short Circuit to Battery (SCB), Short Circuit to Ground (SCG) and Open Load (OL). These faults can occur during either on-state or off-state of power stage output. It is essential to diagnose a fault such as SCB during switch off-state, SCG during switch on-state and OL during both on and off-state of the switch in order to avoid system malfunction, power-stage damage etc. A high-side power-stage mainly consists of a switching power MOSFET and its driver section. Quite often the semiconductor manufacturers provide diagnostic information through a digital status (ST) output. A logic low level on the ST pin indicates a fault. The limitation the ST signal is its inability to distinguish faults SCG, SCB and OL.

For high-side switches (HSS), to overcome these drawbacks, there is a need of proper diagnosing technique. The diagnosis technique should address

1. i
   Detect a fault of power stage.
2. ii
   Clearly distinguish the kind of fault.

The improvised diagnostic strategy provides a simplified solution for fulfilling the requirements by utilizing ST and reading output via ADC.