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Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B02 Page 1 of 5
Datel’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 (58mm2) 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 generate 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
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com/dpm
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B02 Page 2 of 5
TECHNICAL NOTES (continued)
3. Input-Output Isolation: 78SR regulators’ internal input and output cir-
cuits share a common connection (GND, pin 2), there is no electrical
isolation between their 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
where a catastrophic failure occurs, the output voltage may rise to
excessively high levels. If the load circuit must be protected against
all possible overvoltage situations, voltage-limiting circuitry must be
provided externally.
5. Soldering & Handling Precautions: All units are designed to be hand
soldered to pc-boards, using lead-free no-clean solders (+260°C, 5
seconds max.). See the Mechanical Specifi cations section for pin 1
orientation and recommended pc-board hole dimensions.
78SR series regulators have limited built-in ESD protection; therefore
they should always be treated as ESD susceptible devices.
6. Horizontal-Pin Models (78SRH): 78SRH switching regulators are pin-
compatible replacements for TO-220 style LM78xx linear regulators
which are installed with their metal tabs or heat sinks laying fl at on
the surface of the pc-board. In replacement applications, 78SRH units
must be soldered to the pc-board such that the insulating body of
diode D1 lies fl at and in contact with the pc-board’s surface.
Input/Output
Models 78SR-3.3/2 78SR-5/2
Output Voltage 3.3Vdc 5.0Vdc
Rated Output Current 2.0A 2.0A
Output Voltage Accuracy ±2% ±2%
Input Voltage Range ➀ ➁ 8.0-32Vdc 8.0-32Vdc
Line Regulation (100% load) ±0.35% ±0.35%
Load Regulation (0-100% load) ±0.2% ±0.2%
Quiescent Current (mAdc) 25 typ., 30 max 20 typ., 35max
Input Current vs. Input Voltage See Effi ciency Curves
Effi ciency See Effi ciency Curves
Transient Response See Performance Curves
Input & Output Noise See Performance Curves
Output Short Circuit Protection ➀ Continuous
Input/Output Isolation None
Overvoltage Protection None
Undervoltage Protection None
Environmental
Models 78SR-3.3/2 78SR-5/2
Operating Temperature –40 to +70°C
Storage Temperature –40 to +85°C
Cooling ③ Free Air Convection
Humidity (Non-condensing) 0 to 85%
Physical
Mechanical See Mechanical Specifi cations
Package Open-frame SIP
Pins 0.025” (0.64mm) square,
tin-plated bronze
Weight 0.15 ounces (4.2g)
Pin Soldering +260°C for 5 seconds
Absolute Maximum Ratings ➁
Input Voltage: +36Vdc
Operating Temperature +85°C
Output Current 3.0 Amps
➀ 78SR Series regulators can withstand a continuous short-circuit across their
output terminals. However, extended short-circuit operation will decrease the
unit’s long-term reliability.
➁ These are stress ratings only; Exposure of devices to any of these conditions
may adversely affect long-term reliability. Proper operation under conditions
other than those listed in the Performance/Functional Specifi cations Table is not
implied.
③ See derating chart for more information.
Performance/Functional Specifi cations
Typical at TA = +25°C & VIN = 12V, unless otherwise noted
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com/dpm
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B02 Page 3 of 5
Noise and Ripple - 10% and 100% Load, 20 MHz Bandwidth
78SR-3.3/2 Vin = 12V
,
ILOAD = 2.0A
Typical Performance Curves TA = +25°C, VIN as indicated
Transient Response - 90% Load Step
78SR-5/2 Vin = 12V
,
ILOAD = 2.0A
78SR-3.3/2 Vin = 24V
,
ILOAD = 2.0A
78SR-5/2 Vin = 24V
,
ILOAD = 2.0A
78SR-5/2 100% to 10% Load Ste
p
78SR-3.3/2 10% to 100% Load Ste
p
78SR-5/2 10% to 100% Load Ste
p
78SR-3.3/2 100% to 10% Load Ste
p
78SR-3.3/2 Vin = 12V, ILOAD = 0.2A
78SR-5/2 Vin = 12V
,
ILOAD = 0.2A
78SR-3.3/2 10% to 100% Load Step
78SR-5/2 10% to 100% Load Ste
p
Vin = 12V Vin = 24V Vin = 12V
Vin = 12V Vin = 24V Vin = 12V
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com/dpm
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B02 Page 4 of 5
78SR-3.3/2-C Input Current 78SR-5/2-C Input Current
INPUT VOLTAGE
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30 35
2.0A LOAD
0.5A LOAD
1.0A LOAD
INPUT CURRENT (AMPS)
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30 35
INPUT CURRENT (AMPS)
INPUT VOLTAGE
2.0A LOAD
1.0A LOAD
0.5A LOAD
55%
60%
65%
70%
75%
80%
85%
90%
95%
100%
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
Vin = 8V
Vin = 12V
Vin = 15V
Vin = 24V
Vin = 28V
Vin = 32V
EFFICIENCY (%)
LOAD CURRENT (AMPS)
55%
60%
65%
70%
75%
80%
85%
90%
95%
100%
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
Vin = 8V
Vin = 12V
Vin = 15V
Vin = 24V
Vin = 28V
Vin = 32V
EFFICIENCY (%)
LOAD CURRENT (AMPS)
1.25
1.50
1.75
2.00
8 121524283236
60ºC
OUTPUT CURRENT (AMPS)
INPUT VOLTAGE
65ºC
70ºC
Thermal Derating Curve
78SR-3.3/2-C Effi ciency 78SR-5/2-C Effi ciency
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifi cations are subject to change without
notice. © 2009 Murata Power Solutions, Inc.
USA: Mansfi eld (MA), Tel: (508) 339-3000, email: sales@murata-ps.com
Canada: Toronto, Tel: (866) 740-1232, email: toronto@murata-ps.com
UK: Milton Keynes, Tel: +44 (0)1908 615232, email: mk@murata-ps.com
France: Montigny Le Bretonneux, Tel: +33 (0)1 34 60 01 01, email: france@murata-ps.com
Germany: München, Tel: +49 (0)89-544334-0, email: munich@murata-ps.com
Japan: Tokyo, Tel: 81-3-3779-1031, email: japan@murata-ps.com
Kyoto, Tel: 81-75-955-7269, email: japan@murata-ps.com
China: Shanghai, Tel: +86 215 027 3678, email: shanghai@murata-ps.com
Guangzhou, Tel: +86 208 221 8066, email: guangzhou@murata-ps.com
Singapore: Parkway Centre, Tel: +65 6348 9096, email: singapore@murata-ps.com
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfi eld, MA 02048-1151 U.S.A.
Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
www.murata-ps.com email: sales@murata-ps.com ISO 9001 and 14001 REGISTERED
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
06/01/09
www.murata-ps.com/dpm
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Effi ciency,
Synchronous Switching Regulators
MPM_78SR-2A_B02 Page 5 of 5
MECHANICAL DIMENSIONS: Inches (mm)
TOLERANCES: 2 PL DEC ±0.02 (±0.51)
3 PL DEC ±0.010 (±0.254)
Horizontal Package
(H Pin Option)
0.30 (7.6) min.
0.280
(7.1)
PC-Board Hole:
0.037 - 0.043
(0.94 - 1.09) Dia.
Pins: 0.025 (0.64) sq.
0.100 (2.54)
centers
OUTPUT (+VOUT)
GND
INPUT (+VIN)
Standard Package
0.85
(21.6)
0.80
(20.3)
OUTPUT (+VOUT)
PC-Board Hole:
0.037 - 0.043
(0.94 - 1.09) Dia.
GND
INPUT (+VIN)
0.095
(2.4)
Pins: 0.025 (0.64) sq.
0.100 (2.54)
centers
0.15
(3.8) Min.
0.16
(4.1)
0.23
(5.7)
0.07
(1.8)
$!4%,32#
$!4%,32#
123
L1
L1
123
L1
L1
L1
D1
D1
