400mA SmartLDO
TM
SC1534
PRELIMINARY - July 26, 2000
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
The SC1534 is designed to maintain a glitch-free 3.3V
output when at least one of two inputs, 5V (VIN) and
3.3V (VAUX), is present.
Whenever VIN exceeds a predetermined threshold
value, the internal 3.3V linear regulator is enabled, and
DR is pulled high.
When VIN falls below a lower threshold value, DR is
pulled low and the internal linear regulator is turned off.
DR has been designed to drive the gate of an external
low threshold P-channel MOSFET, which can be used
to connect the 3.3V supply directly to the regulator out-
put. This ensures an uninterrupted 3.3V output even if
VIN falls out of specification. A maximum R
DS(ON)
of
200m鈩?is recommended.
When both supplies are simultaneously available, the
drive pin (DR) will be pulled High, turning off the exter-
nal PMOS switch.
The internal 5V detector has its upper threshold (for
VIN rising) set to 4.22V (typical) while the lower thresh-
old (for VIN falling) is at 4.05V (typical) giving a hys-
teresis of approximately 170mV.
The SC1534 is available in the popular SO-8 and 5-
lead TO-263 surface mount packages.
FEATURES
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
鈥?
Glitch-free transition between input sources
Internal logic selects input source
Gate drive for external PMOS bypass switch
5V detector with hysteresis
1% regulated output voltage accuracy
400mA load current capability
SO-8 and TO-263 packages
APPLICATIONS
Desktop Computers
Network Interface Cards (NICs)
PCMCIA/PCI Interface Cards
Cardbus
TM
Technology
Power supplies with multiple input sources
(1)
ORDERING INFORMATION
Part Number
Package
TO-263-5L
SO-8
SC1534CM.TR
SC1534CS.TR
Note:
(1) Only available in tape and reel packaging.
ABSOLUTE MAXIMUM RATINGS
Parameter
Input Supply Voltage
Auxiliary Supply Voltage
Symbol
VIN
VAUX
I
O
T
A
T
J
T
STG
T
LEAD
Maximum
-0.5 to +7
-0.5 to +7
10 to 400
-5 to +70
-5 to +125
-65 to +150
300
Units
V
V
mA
擄C
擄C
擄C
擄C
BLOCK DIAGRAM
LDO Output Current
Operating Ambient
Temperature Range
Operating Junction
Temperature Range
Storage Temperature
Range
Lead Temperature
(Soldering) 10 Sec
PIN CONFIGURATION
Top View
Thermal Impedance
Junction to Ambient
SO-8
(1)
TO-263
Thermal Impedance
Junction to Case
SO-8
TO-263
胃
JA
65
60
擄C/W
胃
J C
39
3
2
擄C/W
kV
SO-8
TO-263-5L
ESD Rating
ESD
Note:
(1) 1 inch square of 1/16鈥?FR-4, double sided, 1 oz. mini-
mum copper weight.
1
漏 2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
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