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78xxSR Series
3.3V/5V/12V Outputs High-Effi ciency
Switching Regulators with LM78xx Pinouts
30 Oct 2015 MDC_78xxSR Series.B07 Page 1 of 7
Murata Power Solutions’ 7805SR-C (5V output), 7812SR-C (12V output) and 7803SR-C
(3.3V output) step-down switching regulators are modern drop-in replacements for older,
ineffi cient, LM7805 and LM7812 linear regulators. The 78XXSR's are pin- and size-compat-
ible with industry-standard TO-220 SIP packages. A 260kHz switching frequency provides
for effi ciencies as high as 95%. Full-load (up to 0.5A) operation from 9V, 12V, 24V, or 36V
supplies at ambient temperatures up to +70°C requires no heat sinks, no temperature
derating, no forced-air cooling, and no external capacitors.
78SR switching regulators provide many signifi cant improvements over their linear coun-
terparts: lower quiescent current (3mA vs. 5 mA), higher input voltage (40V vs. 32V), and
better output accuracy (±2% vs. ±5%). All these features combine to make 78SR regulators
ideal for new or existing LM7805 & LM7812 applications requiring full-load operation at
elevated voltages.
TECHNICAL NOTES
1. Input/Output (I/O) Filtering: As shown in the noise and ripple graphs, 78SR switching
regulators exhibit excellent low-noise performance with no external I/O capacitors.
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 system voltages and temperatures. Adding external output capacitors will also
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 generate 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 selecting an appropriate slow-blow fuse.
3. Input-Output Isolation: 78SR regulators’ internal input and output circuits share a
common connection (GND, pin 2); there is no electrical isolation between the INPUT
(pin 1) and OUTPUT (pin 3) terminals.
4. Overvoltage Protection: 78SR switching regulators do not provide input or output
overvoltage protection. In the extremely rare situation in which a catastrophic failure
occurs, the output voltage may rise to excessively high levels. If your load must be
protected against all possible overvoltage situations, external voltage-limiting circuitry
must be provided.
5. Operation at 40Vdc: Operating with inputs up to 40Vdc is permissible if, for inputs
between 36 and 40Vdc, the maximum load current is reduced to 0.35A for 7805SR-C
and 7803SR-C, and to 0.3A for 7812SR-C. Under no circumstances should the input
voltage be allowed to exceed 45Vdc.
MPS Part No. Output Output Input
Voltage Current Voltage
Standard Pin Package
7803SR-C +3.3Vdc 0.5A +7.5-36Vdc
7805SR-C +5.0Vdc 0.5A +7.5-36Vdc
7812SR-C +12.0Vdc 0.4A +15-36Vdc
Horizontal Pin Package
7803SRH-C +3.3Vdc 0.5A +7.5-36Vdc
7805SRH-C +5.0Vdc 0.5A +7.5-36Vdc
7812SRH-C +12.0Vdc 0.4A +15-36Vdc
Ordering Information
FEATURES
3.3V/0.5A, 5V/0.5A or 12V/0.4A outputs; Pin and
size-compatible with LM7805 & LM7812 regulators
Up to 95% effi ciency – no heat sinks or thermal
derating required
Two SIP-packages fi t existing TO-220 footprints:
- Vertical-pin models occupy less than 0.1 square in.
- Optional horizontal pins provide 0.350 in. installed
height
+7.5-36Vdc operating input range; Low 3mA
quiescent current
Built-in fi lter capacitors – no external components
required
–40 to +70°C operation at full load; Short-circuit
protection
Excellent load (±0.2%) and line (±0.3%) regulation
Ideal for powering instrumentation from
9V/12V/24V/28V supplies or batteries
Can be used with unregulated dc supplies
protection
