TLE4271 datasheet(3/23 Pages) INFINEON

3 / 23 page

TLE 4271-2

Data Sheet Rev. 2.4

2001-04-04

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

current prevents any over-saturation of the power element.

The reset output RO is in high-state if the voltage on the delay capacitor

D is greater or

equal

UD. The delay capacitor CD is charged with the current ID for output voltages

greater than the reset threshold

RT. If the output voltage gets lower than VRT (’reset

condition’) a fast discharge of the delay capacitor

D sets in and as soon as VD gets lower

than

LD the reset output RO is set to low-level.

The time for the delay capacitor charge from

UD to VLD is the reset delay time tD.

When the voltage on the delay capacitor has reached

UD and reset was set to high, the

watchdog circuit is enabled and discharges

D with the constant current IDWD. If there is

no rising edge observed at the watchdog input,

D will be discharge down to VLDW, then

reset output RO will be set to low and

D will be charged again with the current IDWC until

D reaches VUD and reset will be set high again.

If the watchdog pulse (rising edge at watchdog input WI) occurs during the discharge

period

D is charged again and the reset output stays high. After VD has reached VUD,

the periodical behavior starts again.

Internal protection circuits protect the IC against:

• Overload

• Overvoltage

• Overtemperature

• Reverse polarity

TLE4271 Datasheet(PDF) 3 Page - Infineon Technologies AG