Data Sheet

12

Rev. 3.4, 2007-08-16

TLE 6711

Circuit Description

The TLE 6711 G/GL is also protected against several boost loop errors:

In case of a feedback interruption a pull-up current source (

I

voltage at the feedback pin BOFB above the reference voltage. The boost output is switched off by the high error

voltage which controls the PWM-Comparator at a zero duty cycle.

In the case of a resistive loop error caused by leakage currents to ground, the boost output voltage would increase

to very high values. In order to protect the

V

an overvoltage protection is provided which switches the output transistor off as soon as the voltage at pin

V

BOOST

exceeds the internal fixed overvoltage threshold

V

Application Note

A short circuit from

V

the boost inductance if there is no overcurrent limitation in that path.

Figure 9

Most Important Waveforms of the Boost Converter Circuit

AED02672

t

C

V

Error

V

and

V

CV

CP

V

t

L

H

OCLK

PWM

L

H

t

t

I

BOI

BOLI

I

DBO

I

t

BOI

V

t

BOOST

V

S

V

Overcurrent Threshold Exceeded

Controlled by the

Load-Current Increasing with Time;

Error Voltage

Overcurrent Comp

Controlled by the Error Amp