Datasheet
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78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B04 Page 1 of 6
Murata’s 78SR-3.3/2 (3.3V, 2 Amp output) and 78SR-5/2 (5V, 2 Amp output) step-down,
switching regulators are ultra high-effi ciency, modern replacements for LM78xx series
1.5Amp linear regulators. They are pin- and size-compatible, drop-in replacements for
TO-220 style, 3-pin SIP or modular packages which require heat sinks. And, to ensure the
lowest installed cost, no messy thermal grease, no mounting hardware and no external
components are required for full operation.
A 200KHz switching frequency, combined with a synchronous rectifi er buck regulator
topology, provides for effi ciencies exceeding 95%. 78SR switchers can easily drive 2A loads
from 12V or 24Vsupplies—at ambient temperatures up to +70°C—without heat sinks,
fans, or thermal derating. A thermally effi cient 3-pin vertical mount SIP occupies less than
0.09in.
2
(58mm
2
) of pc-board real estate, while a horizontal mount option has an installed
height of less than 0.290in. (7.4mm).
78SR Series 2A switching regulators are lower cost, improved-effi ciency upgrades for
many 78HT2, 78SR1, 78ST1, and PT5100 series switchers. Their higher effi ciency ensures
signifi cantly lower heat generation and provides increased run time in battery-powered
applications, making these regulators ideal for today’s low power “green” applications.
FEATURES
Up to 95% effi ciency– no costly heat sinks or fans
required
3.3V/2A & 5V/2A models; pin compatible with 1.5A 78xx
regulators
Wide 8– 32Vdc input voltage range
Two package options:
3-pin vertical mount SIP
Low profi le, horizontal mount SIP
No external Input/Output fi lter capacitors required
–40 to +70°C full load operation at 24Vin with no
derating
Excellent load (±0.25%) and line (±0.35%) regulation
Low-cost upgrade for 78HT2, 78SR1, 78ST1, and
PT5100 switchers
Open frame design minimizes self-heating & pc-board
footprint
Includes output short-circuit protection and thermal
shutdown
Low noise output for powering sensitive instrumentation
TECHNICAL NOTES
1. Input/Output (I/O) Filtering: As shown in the accompanying noise and ripple graphs,
78SR Series regulators exhibit excellent low noise performance with no additional I/O
fi lter components. However, if additional noise reduction is required, be sure to use low
ESR capacitors that are rated for continuous operation (with an additional 20% safety
margin) at the highest input voltage and ambient temperatures. Adding external output
capacitors will improve the unit’s load-transient response.
Applications in which 78SR regulators are located more than 24 inches (61cm) from
the input power supply should include an external 47uF/50V (or greater) aluminum
electrolytic capacitor, connected as close as possible to the regulator’s +Vin and GND
terminals (pins 1 and 2). An external input capacitor is particularly important if the input
voltage is applied to the regulator via a mechanical switch or relay. Contact bounce at
turn-on can produce large inductive current spikes, and these current spikes can gener-
ate potentially damaging voltage transients at the regulator’s input terminals.
2. Input Fusing: 78SR switching regulators are not internally fused. If fusing their input
and/or output terminals is required, use the data shown in the Effi ciency Curves as a
guide to select an appropriate slow-blow fuse.
Part No. Output Output Input
Voltage Current Voltage
78SR-3.3/2-C 3.3Vdc 2.0A 8.0-32Vdc
78SR-5/2-C 5.0Vdc 2.0A 8.0-32Vdc
78SRH-3.3/2-C 3.3Vdc 2.0A 8.0-32Vdc
78SRH-5/2-C 5.0Vdc 2.0A 8.0-32Vdc
Ordering Information