Details, datasheet, quote on part number: SC1534CSTR
Description400ma Smartldotm
CompanySemtech Corporation
DatasheetDownload SC1534CSTR datasheet
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Features, Applications


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 output. This ensures an uninterrupted 3.3V output even if VIN falls out of specification. A maximum RDS(ON) 200m is recommended. When both supplies are simultaneously available, the drive pin (DR) will be pulled High, turning off the external PMOS switch. The internal 5V detector has its upper threshold (for VIN rising) set to 4.22V (typical) while the lower threshold (for VIN falling) at 4.05V (typical) giving a hysteresis of approximately 170mV. The SC1534 is available in the popular SO-8 and 5lead TO-263 surface mount packages.

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


Desktop Computers Network Interface Cards (NICs) PCMCIA/PCI Interface Cards CardbusTM Technology Power supplies with multiple input sources

Note: (1) Only available in tape and reel packaging.

Parameter Input Supply Voltage Auxiliary Supply Voltage Symbol VIN VAUX TA TJ TSTG TLEAD Maximum +150 300 Units mA C

LDO Output Current Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) 10 Sec

Thermal Impedance Junction to Ambient SO-8(1) TO-263 Thermal Impedance Junction to Case SO-8 TO-263
Note: (1) 1 inch square 1/16" FR-4, double sided, 1 oz. minimum copper weight.

Pin Name DR GND VAUX VIN VO SO-8 Pin TO-263-5L Pin 2 4 Pin Function Driver output for external P-channel MOSFET pass element. Logic and power ground. This is the auxiliary input supply, nominally 3.3V. This is the main input supply for the IC, nominally 5V. LDO 3.3V output.

NOTE: (1) External switch (Q1): use a low threshold P-channel MOSFET such as Fairchild FDN338P or International Rectifier IRF7604, or equivalent. (PMOS, typical gate threshold voltage ~ 1V, RDS(ON) 200m at VGS = 2.7V).


Unless specified, = 25C, VIN = 5V, VAUX = 10F. Values in bold apply over full operating temperature range.

VAUX Supply Voltage Quiescent Current VAUX IQ(AUX) VAUX = 3.3V, VIN = 0mA VAUX = 3.3V, VIN = 0mA Reverse Leakage From VIN



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