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78xxSR Series
3.3V/5V/12V Outputs High-Efficiency
Switching Regulators with LM78xx Pinouts
FEATURES
3.3V/0.5A, 5V/0.5A or 12V/0.4A outputs; Pin and
size-compatible with LM7805 & LM7812 regulators
to 95% efficiency – no heat sinks or thermal
Up
derating required
SIP-packages fit existing TO-220 footprints:
Two
- 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 filter capacitors – no external components
required
to +70°C operation at full load; Short-circuit
–40
protection
Excellent load (±0.2%) and line (±0.3%) regulation
for powering instrumentation from
Ideal
9V/12V/24V/28V supplies or batteries
be used with unregulated dc supplies
Can
protection
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,
inefficient, 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 efficiencies 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 significant 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 Efficiency 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.
Ordering Information
MPS Part No.
Output
Voltage
Output
Current
0.5A
0.5A
0.4A
0.5A
0.5A
0.4A
Input
Voltage
+7.5-36Vdc
+7.5-36Vdc
+15-36Vdc
+7.5-36Vdc
+7.5-36Vdc
+15-36Vdc
Standard Pin Package
7803SR-C
+3.3Vdc
7805SR-C
+5.0Vdc
7812SR-C
+12.0Vdc
Horizontal Pin Package
7803SRH-C
+3.3Vdc
7805SRH-C
+5.0Vdc
7812SRH-C
+12.0Vdc
For full details go to
www.murata-ps.com/rohs
www.murata-ps.com/support
30 Oct 2015
MDC_78xxSR Series.B07
Page 1 of 7
78xxSR Series
TECHNICAL NOTES
(continued)
6. Soldering & Handling Precautions:
All units are designed to be hand
soldered to pc-boards using no-clean solders (+260°C, 5 seconds max.).
Water-soluble solders can also be used, but the units must be washed
and dried using processes appropriate to the type of solder employed.
See the Mechanical Specifications section for pin 1 orientation and
recommended plated-through hole dimensions.
While 78SR regulators easily withstand a 2kV ESD discharge to any ter-
minal (using human body model), they should always be treated as ESD
sensitive devices.
7. Horizontal-Pin Models (78XXSRH-C):
78XXSRH-C switching regulators
are pin-compatible replacements for TO-220 style LM78XX linear regula-
tors that are installed with their metal tabs lying flat on the surface of the
pc-board. However, because the surface of inductor L1 on 78XXSRH-C
models is electrically conductive, it must not be allowed to come in con-
tact with any exposed pc-board traces, other than power ground (GND).
While the 2-mil-thick (0.05mm) polyester label attached to L1 provides
some degree of electrical insulation (only if L1 sits perfectly flat on the
pc-board), it is recommended that a 0.020” (0.5mm) clearance be main-
tained between L1 and all exposed pc-board traces.
8. Dropout Voltage:
78SR series regulators described in this data sheet
specify a minimum input voltage at which full-load accuracy and output
regulation are guaranteed (7.5V for 7803SR-C and 7805SR-C, and 15.0V
for 7812SR-C). However, these devices will stay in regulation at lower
input voltages if they are operated at less than their rated loads.
The following dropout-voltage data, derived from sample testing
performed at an ambient temperature of +25°C with resistive loads,
should be used for information purposes only. For these tests, a unit was
considered to be out of regulation when its output changed by more
+/–0.005Vdc from its nominal value. All voltages were measured directly
at the regulator’s I/O pins.
3.3V/5V/12V Outputs High-Efficiency
Switching Regulators with LM78xx Pinouts
Performance/Functional Specifications
Typical at T
A
= +25°C
Input/Output
Models
Output Voltage
Rated Output Current
Output Voltage Accuracy
Input Voltage Range
➀
Line Regulation (100% load)
Load Regulation (0-100% load)
Quiescent Current
Input Current
Efficiency
Transient Response
Input & Output Noise
Short Circuit Protection
➁
Isolation
Overvoltage Protection
Undervoltage Protection
7803SR-C
+3.3Vdc
0.5A
±2%
+7.5-36Vdc
±0.3%
±0.2%
7805SR-C
+5.0Vdc
0.5A
±2%
+7.5-36Vdc
±0.3%
±0.2%
7812SR-C
+12.0Vdc
0.4A
±2%
+15-36Vdc
±0.3%
±0.2%
3mA typ., 5mA max.
See Performance Curves
See Performance Curves
See Performance Curves
See Performance Curves
Continuous
None
None
None
Environmental
Models
Operating Temperature
Storage Temperature
Cooling
Humidity (Non-condensing)
7803SR-C
7805SR-C
–40 to +70°C
–40 to +85°C
Free Air Convection
0 to 85%
7812SR-C
Physical
Mechanical
Package
Pins
See Mechanical Specifications
Open-frame SIP
0.025” (0.64mm) square,
tin-plated bronze
0.08 ounces (2.2g)
+260°C for 5 seconds
Typical Dropout Voltage
0% Load
7803SR-C
7805SR-C
7812SR-C
6.0V
6.3V
12.8V
25% Load
6.2V
6.2V
13.0V
50% Load
6.2V
6.2V
12.8V
100% Load
6.3V
6.8V
13.0V
Weight
Pin Soldering
➀
See Technical Note 5.
➁
While these regulators can withstand a continuous short-circuit across their
output terminals, they will experience a significant temperature rise. Extended
short-circuit operation will adversely affect the unit’s reliability.
www.murata-ps.com/support
30 Oct 2015
MDC_78xxSR Series.B07
Page 2 of 7
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