spx1580 Exar Corporation, spx1580 Datasheet - Page 4

• Manufacturer Part Number: spx1580
• Description: 7a Ultra Dropout Voltage Regulator
• Manufacturer: Exar Corporation

Output Capacitor
An output capacitor for SPX1580 is for circuit
compensation for the device to prevent
oscilliation. The minimum size of the output
capacitor is either a 330µF aluminum electro-
lytic capacitor or 33uF tantalum. Larger capaci-
tor values improve the regulator transient re-
sponse performance and increase surge load
capability. The output capacitor should have an
ESR not more than 0.3Ω.
Adjustable Regulator Design
1.25V reference voltage is being developed be-
tween the SENSE pin and the ADJ pin of the
SPX1580. Adding two external resistors (see fig
1.) will allow setting the output voltage from
1.25V to 6V. R
specified minimum load current of 10mA. R
given by the formula: V
+ I
pin is typicaly 50uA. This ADJ pin contributes
to the final V
Connecting the sense pin to the top of the resis-
tor divider will improve load regualtion.
Figure 1. Adjustable Regulator.
Date: 5/16/04
ADJ
(R
2
). The current flowing from the ADJ
3.3V
V
5V
V
IN
CTRL
OUT
1
is chosen so that this current is
but is usually neglected.
OUT
C1
33µF
= V
V
IN
V
REF
CTRL
C2
10µF
SPX1580 7A Ultra Dropout Voltage Regulator
(1+ R
5
4
(1) V
(2) V
(3) V
SPX1580
2
/R
2
is
1
2
CTRL
OUT
REF
)
ADJ
C4
0.033µF
is measured across adjust to sense.
= V
4
needed when V
3
REF
1
Lowering Noise
Using the SENSE pin to Kelvin the load will
increase accuracy of the output voltage during
load regulation. For the fixed voltage device,
adding a bypass capacitor from ADJ pin to
ground improves transient response. A 330pF
ceramic capacitor is recommended.
(1+R
SENSE
V
OUT
2
/R
1
IN
)+I
APPLICATION INFORMATION
< 5V.
ADJ
R
R1
124Ω
R2
124Ω
2
.
©Copyright 2004 Sipex Corporation
C3
68µF
2.5V
V
OUT