SPX3819 SIPEX [Sipex Corporation], SPX3819 Datasheet - Page 7

• Manufacturer Part Number: SPX3819
• Description: 500 mA, Low-Noise LDO Voltage Regulator
• Manufacturer: SIPEX [Sipex Corporation]

Figure 1. Standard Application Circuit
The SPX3819 requires an output capacitor for
device stability. Its value depends upon the
application circuit. In general, linear regulator
stability decreases with higher output currents.
In applications where the SPX3819 is putting
out less current, a lower output capacitance may
be sufficient. For example, a regulator sourcing
only 10mA, requires approximately half the
capacitance as the same regulator sourcing
150mA.
Bench testing is the best method for determining
the proper type and value of the capacitor since
the high frequency characteristics of electro-
lytic capacitors vary widely, depending on type
and manufacturer. A high quality 2.2µF alumi-
num electrolytic capacitor works in most appli-
cation circuits, but the same stability often can
be obtained with a 1µF tantalum electrolytic.
With the SPX3819 adjustable version, the mini-
mum value of output capacitance is a function of
the output voltage. The value decreases with
higher output voltages, since closed loop gain is
increased.
Typical Applications Circuits
A 10nF capacitor on BYP pin will significantly
reduce output noise but it may be left uncon-
nected if the output noise is not a major concern.
Date:6/8/2004
V
IN
+
ENABLE may be tied directly to V
GND
EN
1
3
2
SPX3819
TOP View
IN
5
4
(Opt.)
BYP
SPX3819 500mA, Low Noise LDO Voltage Regulator
+
V
OUT
7
The SPX3819 start-up speed is inversely pro-
portional to the size of the BYP capacitor. Ap-
plications requiring a slow ramp-up of the out-
put voltage should use a larger C
if a rapid turn-on is necessary, the BYP capaci-
tor can be omitted.
The SPX3819’s internal reference is available
through the BYP pin.
Figure 1 represents a SPX3819 standard appli-
cation circuit. The EN (enable) pin is pulled
high (>2.0V) to enable the regulator.
To disable the regulator, EN < 0.4V.
The SPX3819 in Figure 2 illustrates a typical
adjustable output voltage configuration. Two
resistors (R
output voltage is calculated using the formula:
R
should be between 22 kΩ and 47kΩ. A capacitor
placed between Adj and ground will provide
improved noise performance.
Figure 2. Typical Adjustable Output Voltage Configuration
2
V
IN
+
must be > 10 kΩ and for best results, R
GND
EN
Hi-ON
Lo-OFF
V
OUT
1
APPLICATION INFORMATION
and R
= 1.235V x [ 1 + R
1
3
2
TOP View
2
SPX3819
SOT-23
) set the output voltage. The
(Opt.)
© Copyright 2004 Sipex Corporation
BYP
5
4
ADJ
BYP
1
R1
R2
/R
. However,
2
]
+
V
OUT
2