CS5231-3
CS5231-3
500mA, 3.3V Linear Regulator
with Auxiliary Control
Description
The CS5231-3 combines a three-
terminal linear regulator with cir-
cuitry to control an external PFET
transistor with the intent of manag-
ing two input supplies. A 5V sup-
ply powers the regulator while an
auxiliary 3.3V supply is controlled
by the IC. The design has been opti-
mized to provide a “glitch-free”
transition between the two sup-
plies.
The CS5231-3 linear regulator pro-
vides a fixed 3.3V output @ 500mA
with an overall accuracy of ± 2%.
The NPN-PNP composite pass tran-
sistor provides a low dropout volt-
age and requires less supply cur-
rent than PNP designs. Full protec-
tion including current limit and
thermal shutdown is provided.
Also designed for low reverse cur-
rent, the IC prevents excessive cur-
rent from flowing from the output
to ground if the regulator input
voltage is lower than the output
voltage.
The CS5231-3 also controls an auxil-
iary supply that can provide power
to the regulator output when input
voltage for the regulator is not
available. The AuxDrv auxiliary
output is normally pulled up to the
regulator input voltage and drives
low whenever the input voltage
drops below 4.4V (nominal). It is
typically used to control a PFET
switch that connects a 3.3V auxil-
iary supply to the regulator output.
The CS5231-3 is available in a
5-lead D
2
PAK (TO-263) package.
Applications include Network
Interface Cards (NICs), modem
cards and power supplies with
multiple input sources.
Features
Linear Regulator
s
3.3V ± 2% Output Voltage
s
3mA Quiescent Current
@ 500mA
s
Fast Transient Response
s
Current Limit
s
Thermal Shutdown with
Hysteresis
s
450µA Reverse Output
Current
s
Fast Transient Response
System Power Management
s
Auxiliary Supply Control
Package Options
5 Lead D
2
PAK
V
OUT
Block Diagram
V
IN
10kΩ
50kΩ
Internal
Bias
Current
Limit
−
AuxDrv
V
IN
UV
Comparator
Bandgap
Reference
Gnd
Thermal
Shutdown
+
Error
Amp
Shutdown
−
+
1
1. No Connect
2. V
IN
3. Gnd
4. V
OUT
5. AuxDrv
Tab = Gnd
V
REF
Consult factory for other package
options.
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 3/31/99
1
A
®
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
