TLE 4284

Data Sheet

21

Rev. 2.1, 2007-03-20

Application Hints

Adjustable Version

At the fixed voltage TLE 4284 devices, the output voltage is divided internally and

compared to an internal reference of 1.25 V typical. The regulation loop controls the

output voltage to achieve the output voltage of 5 V, 3.3 V, 2.6 V, 1.8V or 1.5V. The

variable version compares the voltage difference between the adjust pin ADJ and the

output pin Q to the internal reference of typically 1.25 V. The output voltage is adjusted

by an external voltage divider between Q, ADJ and GND and calculates:

For the variable regulator TLE 4284 DV, a minimum load current of 5 mA is necessary

in order to keep the output voltage regulated. If the application does not assure this

minimum load requirement, the output voltage divider should be dimensioned sufficiently

low-ohmic: R

For the variable voltage type an additional decoupling a capacitor

C

improves the ripple rejection ratios. Placing

C

an increased output

capacitance of C

Output

The output current limitation is reduced as a function of the input voltage for high input

voltages above 25 V.

The TLE 4284 requires a 10 µF output capacitor with 0.1

Ω ≤ ESR ≤ 10 Ω for the stability

of the regulation loop.

At the input of the regulator a capacitor is necessary for compensation of line influences.

A serial diode should be used to eliminate negative voltages from the input. As a

minimum, a 100 nF ceramic input capacitor should be used. If the regulator is used in an

environment with long input lines, an input capacitance of 10 µF is recommended.

V

Q

V

REF

1

R

2

R

1

-----

+





I

ADJ

R

2

×

+

×

=