TLE 4271-2

Data Sheet Rev. 2.4

11

2001-04-04

Application Description

The IC regulates an input voltage in the range of 6 V <

V

26 V it produces a regulated output current of more than 550 mA. Above 26 V the save-

operating-area protection allows operation up to 36 V with a regulated output current of

more than 300 mA. Overvoltage protection limits operation at 42 V. The overvoltage

protection hysteresis restores operation if the input voltage has dropped below 36 V. The

IC can be switched off via the inhibit input, which causes the quiescent current to drop

below 50

watchdog circuit monitors a connected controller. If there is no positive-going edge at the

watchdog input within a fixed time, the reset output is set to low. The delay for power-on

reset and the maximum permitted watchdog-pulse period can be set externally with a

capacitor.

Design Notes for External Components

An input capacitor

C

circuit consisting of lead inductance and input capacitance can be damped by a resistor

of approx. 1

the regulating circuit. Stability is guaranteed at values of

C

<3

Ω.

Reset Circuitry

If the output voltage decreases below 4.5 V, an external capacitor

discharged by the reset generator. If the voltage on this capacitor drops below

reset signal is generated on pin RO, i.e. reset output is set low. If the output voltage rises

above the reset threshold,

reset time the voltage on the capacitor reaches

again. The value of the power-on-reset time can be set within a wide range depending

of the capacitance of

Reset Timing

The power-on reset delay time is defined by the charging time of an external capacitor

Definitions: