A8450
Automotive Multioutput Voltage Regulator
Load Transients Diagrams
V
IN
= 12 V; I
LOAD
= 100 mA; T
A
= 25°C; ac-coupled; C1, C2, C3 and C4 = 1 µF
I
LOAD
3.3 V Regulator
I
LOAD
= 5 to 100 mA
90%
10%
t
RISE
V
OUT
(50 mV / Div.)
t (0.2 µs/Div.)
V5D Regulator
t (50 µs/Div.)
Adjustable Regulator, at 1.8 V*
V
OUT
(50 mV / Div.)
t (50 µs/Div.)
V
OUT
(50 mV / Div.)
t (50 µs/Div.)
V5A Regulator
V
OUT
(50 mV / Div.)
*For the adjustable regulator, the transient load response
is improved as the voltage is reduced. This is due to the
ability of the regulator to provide more base drive (VADJBD)
because of more available voltage. When the adjustable
regulator approaches 3.3 V, its transient load response is
equivalent to the response of the V33 regulator.
For all regulators, load transients can be improved by
increasing the output capacitance (C1, C2, C3, and C4).
In order to keep ESR down it is best to use ceramic type
capacitors. However, large values in ceramic type capacitors
are either not available or very expensive. If larger values are
needed, above 22 µF, electrolytic capacitors with low ESR
ratings can be used. Performance can be improved further
by adding a 1 µF ceramic in parallel with the electrolytic.
t (50 µs/Div.)
A8450KLB-DS, Rev. 1
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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ALLEGRO [ ALLEGRO MICROSYSTEMS ]
