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
1
≤ 240 Ω.
For the variable voltage type an additional decoupling a capacitor
C
ADJ
at the adjust pin
improves the ripple rejection ratios. Placing
C
ADJ
requires an increased output
capacitance of C
Q
≥22 µF.
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
×+×=
