TLE 4269

Data Sheet

5

Rev. 2.4, 2007-03-20

Circuit Description

The control amplifier compares a reference voltage, made highly accurate by resistance

balancing, with a voltage proportional to the output voltage and drives the base of the

series PNP 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

C

equal

V

greater than the reset threshold

V

condition’) a fast discharge of the delay capacitor

C

lower than

V

The time gap for the delay capacitor discharge is the reset reaction time

t

The reset threshold

V

the pin RADJ. In this case the reset condition is reached if

V

and

V

V

the reset threshold can be decreased down to 3.5 V. If the reset-adjust-option is not

needed the RADJ-pin should be connected to GND causing the reset threshold to go to

its default value (typ. 4.65 V).

A built in comparator compares the signal of the pin SI, normally fed by a voltage divider

from the input voltage, with the reference and gives an early warning on the pin SO. It is

also possible to superwise another voltage e.g. of a second regulator, or to build a

watchdog circuit with few external components.

Application Description

The input capacitor

C

approx. 1

capacitance can be damped. The output capacitor

C

regulating circuit. Stability is guaranteed at values

≥ 10 µF and an ESR ≤ 10 Ω within the

operating temperature range. For small tolerances of the reset delay the spread of the

capacitance of the delay capacitor and its temperature coefficient should be noted.