78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Efficiency, Synchronous Switching Regulators
FEATURES
Up to 95% efficiency– 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 profile, horizontal mount SIP No external Input/Output filter 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
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-efficiency, 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 rectifier buck regulator topology, provides for efficiencies 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 efficient 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-efficiency upgrades for many 78HT2, 78SR1, 78ST1, and PT5100 series switchers. Their higher efficiency ensures significantly lower heat generation and provides increased run time in battery-powered applications, making these regulators ideal for today’s low power “green” applications.
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 filter 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 Efficiency Curves as a guide to select an appropriate slow-blow fuse.
Ordering Information
Part No. 78SR-3.3/2-C 78SR-5/2-C 78SRH-3.3/2-C 78SRH-5/2-C Output Voltage 3.3Vdc 5.0Vdc 3.3Vdc 5.0Vdc Output Current 2.0A 2.0A 2.0A 2.0A Input Voltage 8.0-32Vdc 8.0-32Vdc 8.0-32Vdc 8.0-32Vdc
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MPM_78SR-2A_B01 Page 1 of 5
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Efficiency, Synchronous Switching Regulators
Performance/Functional Specifications
Typical at TA = +25°C & VIN = 12V, unless otherwise noted Input/Output Models Output Voltage Rated Output Current Output Voltage Accuracy Input Voltage Range Line Regulation (100% load) Load Regulation (0-100% load) Quiescent Current (mAdc) Input Current vs. Input Voltage Efficiency Transient Response Input & Output Noise Output Short Circuit Protection Input/Output Isolation Overvoltage Protection Undervoltage Protection Environmental Models Operating Temperature Storage Temperature Cooling Humidity (Non-condensing) Physical Mechanical Package Pins Weight Pin Soldering Absolute Maximum Ratings Input Voltage: Operating Temperature Output Current +36Vdc +85°C 3.0 Amps See Mechanical Specifications Open-frame SIP 0.025” (0.64mm) square, tin-plated bronze 0.15 ounces (4.2g) +260°C for 5 seconds 78SR-3.3/2 78SR-5/2 –40 to +70°C –40 to +85°C Free Air Convection 0 to 85% 78SR-3.3/2 3.3Vdc 2.0A ±2% 8.0-32Vdc ±0.35% ±0.2% 17 typ., 30 max 78SR-5/2 5.0Vdc 2.0A ±2% 8.0-32Vdc ±0.35% ±0.2% 20 typ., 35max See Efficiency Curves See Efficiency Curves See Performance Curves See Performance Curves Continuous None None None
TECHNICAL NOTES (continued)
3. Input-Output Isolation: 78SR regulators’ internal input and output circuits 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 Specifications 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 pincompatible replacements for TO-220 style LM78xx linear regulators which are installed with their metal tabs or heat sinks laying flat 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 flat and in contact with the pc-board’s surface.
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. 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 Specifications Table is not implied. See derating chart for more information.
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MPM_78SR-2A_B01 Page 2 of 5
78SR 2 Amp Series
Typical Performance Curves TA = +25°C, VIN as indicated Noise and Ripple - 10% and 100% Load, 20 MHz Bandwidth
78SR-3.3/2 Vin = 12V, ILOAD = 0.2A 78SR-3.3/2 Vin = 12V, ILOAD = 2.0A
2 Amp, 3.3V & 5V Output, High Efficiency, Synchronous Switching Regulators
78SR-3.3/2 Vin = 24V, ILOAD = 2.0A
78SR-5/2
Vin = 12V, ILOAD = 0.2A
78SR-5/2
Vin = 12V, ILOAD = 2.0A
78SR-5/2
Vin = 24V, ILOAD = 2.0A
Transient Response - 90% Load Step
78SR-3.3/2 10% to 100% Load Step Vin = 12V 78SR-3.3/2 10% to 100% Load Step Vin = 24V 78SR-3.3/2 100% to 10% Load Step Vin = 12V
78SR-5/2
10% to 100% Load Step Vin = 12V
78SR-5/2
10% to 100% Load Step Vin = 24V
78SR-5/2
100% to 10% Load Step Vin = 12V
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MPM_78SR-2A_B01 Page 3 of 5
78SR 2 Amp Series
2 Amp, 3.3V & 5V Output, High Efficiency, Synchronous Switching Regulators
78SR-3.3/2-C Input Current
1.0
78SR-5/2-C Input Current
1.0 2.0A LOAD
INPUT CURRENT (AMPS)
2.0A LOAD
INPUT CURRENT (AMPS)
0.8 0.6
0.8 0.6 1.0A LOAD 0.4 0.2 0.0 0.5A LOAD
1.0A LOAD
0.4
0.5A LOAD
0.2 0.0 0 5 10 15 20 25 30 35
0
5
10
15
20
25
30
35
INPUT VOLTAGE
INPUT VOLTAGE
78SR-3.3/2-C Efficiency
100% 95% 90%
78SR-5/2-C Efficiency
100% 95% 90%
EFFICIENCY (%)
EFFICIENCY (%)
85% 80% 75% 70% 65% 60% 55% 0.25 0.50 0.75 1.00
85%
Vin = 8V
80%
Vin = 8V Vin = 12V Vin = 15V Vin = 24V Vin = 28V Vin = 32V
1.25 1.50 1.75 2.00
Vin = 12V
75%
Vin = 15V
70%
Vin = 24V
65%
Vin = 28V
60%
Vin = 32V
55% 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
LOAD CURRENT (AMPS)
LOAD CURRENT (AMPS)
Thermal Derating Curve
2.00 60ºC 65ºC 1.75 70ºC
OUTPUT CURRENT (AMPS)
1.50
1.25 8 12 15 24 28 INPUT VOLTAGE 32 36
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MPM_78SR-2A_B01 Page 4 of 5
78SR 2 Amp Series
MECHANICAL DIMENSIONS: Inches (mm) TOLERANCES: 2 PL DEC ±0.02 (±0.51) 3 PL DEC ±0.010 (±0.254)
2 Amp, 3.3V & 5V Output, High Efficiency, Synchronous Switching Regulators
Standard Package
0.16 (4.1) 0.80 (20.3)
D1
Pins: 0.025 (0.64) sq. 0.100 (2.54) centers PC-Board Hole: 0.037 - 0.043 (0.94 - 1.09) Dia. 0.095 (2.4)
L1 L1
0.85 (21.6)
1 0.15 (3.8) Min. 0.23 (5.7) INPUT (+VIN)
2
3
OUTPUT (+VOUT)
GND
Horizontal Package (H Pin Option)
0.07 (1.8)
L1
L1
L1
1 0.30 (7.6) min. 2 3 Pins: 0.025 (0.64) sq. 0.100 (2.54) centers PC-Board Hole: 0.037 - 0.043 (0.94 - 1.09) Dia.
0.280 (7.1)
D1
INPUT (+VIN) GND OUTPUT (+VOUT)
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Murata Power Solutions, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A. Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
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07/03/08
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. Specifications are subject to change without notice. © 2008 Murata Power Solutions, Inc.
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MPM_78SR-2A_B01 Page 5 of 5
