BTS 771 G

Semiconductor Group

6

1999-01-07

Circuit Description

Input Circuit

The control inputs GH1,2 consist of TTL/CMOS compatible Schmitt-Triggers with

hysteresis. Buffer amplifiers are driven by these stages and convert the logic signal into

the necessary form for driving the power output stages.

The inputs GH1 and GH2 are connected to a standard N-channel logic level power-MOS

gate.

Output Stages

The output stages consist of an ultra low

R

make the outputs short circuit proof to ground and load short circuit proof. Positive and

negative voltage spikes, which occur when driving inductive loads, are limited by

integrated power clamp diodes.

Short Circuit Protection (valid only for the high-side switches)

The outputs are protected against

– output short circuit to ground, and

– overload (load short circuit).

An internal OP-Amp controls the Drain-Source-Voltage of the HS-Switches by

comparing the DS-Voltage-Drop with an internal reference voltage. Above this trippoint

the OP-Amp reduces the output current depending on the junction temperature and the

drop voltage.

In the case of overloaded high-side switches the status output is set to low.

If the HS-Switches are in OFF-state-Condition internal resistors

R

pull the voltage at SH1,2 to low values. On each output pin SH1 and SH2 an output

examiner circuit compares the output voltages with the internal reference voltage VEO.

This results in switching the status output to low. In H-Bridge condition this feature can

be used to protect the low-side switches against short circuit during the OFF-period.

Overtemperature Protection (valid only for the high-side-switches)

The chip also incorporates an overtemperature protection circuit with hysteresis which

switches off the output transistors and sets the status output to low.

Undervoltage-Lockout (UVLO)

When

V

The High-Side output transistors are switched off if the supply voltage

V

the switch off value

V