TLE 4268

Semiconductor Group

4

1998-11-01

Circuit Description

The control amplifier compares a reference voltage, which is kept highly accurate by

resistance adjustment, to a voltage that is proportional to the output voltage and drives

the base of the series transistor via a buffer. Saturation control as a function of the load

current prevents any over-saturation of the power element. If The externally scaled down

output voltage at the reset threshold input drops below 1.35 V, the external reset delay

capacitor is discharged by the reset generator. If the voltage on the capacitor reaches

the lower threshold

V

again until the upper threshold voltage is exceeded. If the reset threshold input is

connected to GND, reset is triggered at an output voltage of 4.5 V. A connected

microcontroller is monitored by the watchdog logic. If pulses are missing, the rest output

is set to low. The pulse sequence time can be set within a wide range with the reset delay

capacitor. The IC also incorporates a member of internal circuits for protection against:

• Overload

• Overtemperature

• Reverse polarity

Figure 3

Block Diagram

AEB01539

Temperature

Sensor

Control

Amplifier

Protection

Circuit

Reference

Bandgap

Adjustment

Generator

Reset

Watchdog

Watchdog

Input

3

12

10

9

Output

Reset

Reset

Reset

Output

Switching

Delay

11

Threshold

18

Input

4-7, 14-17

GND