U6813B

Features Digital Self-supervising Watchdog with Hysteresis One 150-mA Output Driver for Relay One High-side Driver for N-channel Power FET Positive and Negative Enable Output Positive and Negative Reset Output Over/Under-voltage Detection Relay and Power FET Outputs Protected Against Standard Transients and 55-V Load Dump Description The function of microcontrollers in safety-critical applications (e.g., anti-lock systems) needs to be monitored permanently. Usually, this task is accomplished by an independent watchdog timer. The monolithic IC U6813B, designed in bipolar technology and qualified according to the needs of the automotive industry, includes such a watchdog timer and provides additional features for added value. With the help of integrated driver stages, it is easy to control safety-related functions of a relay and of an N-channel power MOSFET in high-side applications. In case of a microcontroller malfunction or supply-voltage anomalies, the U6813B provides positive and negative reset and enable output signals. This flexibility guarantees a broad range of applications. The U6813B is based on of Atmel’s fail-safe ICs U6808B and U6809B. Figure 1. Block Diagram Fail-safe IC with High-side and Relay Driver U6813B VCC Bandgap reference 2.44 V Power-on reset Reset delay fosc 3 P-RES 3.3 V 16 Reset debounce fosc 3.3-V under- and overvoltage detect. 4 N-RES 1 VCC 14 RELO Current limitation VCC 5-V under- and overvoltage detect. 6 N-EN RELI 13 1...