NSC LM2675M-5.0, LM2675M-12, LM2675N-ADJ, LM2675N-5.0, LM2675N-3.3 Datasheet
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September 1998
LM2675
SIMPLE SWITCHER® Power Converter High Efficiency
1A Step-Down Voltage Regulator
General Description
The LM2675 series of regulators are monolithic integrated circuits built with a LMDMOS process. These regulators provide all the active functions for a step-down (buck) switching regulator, capable of driving a 1A load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5.0V, 12V, and an adjustable output version.
Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation (Patent Nos. 5,382,918 and 5,514,947) and a fixed frequency oscillator.
The LM2675 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Because of its very high efficiency (>90%), the copper traces on the printed circuit board are the only heat sinking needed.
A family of standard inductors for use with the LM2675 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies using these advanced ICs. Also included in the datasheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies.
Other features include a guaranteed ±1.5% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring typically 50 µA stand-by current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions.
To simplify the LM2675 buck regulator design procedure, there exists computer design software, LM267X Made Simple version 1.0.
Features
nEfficiency up to 96%
nAvailable in SO-8 and 8-pin DIP packages
nComputer Design Software LM267X Made Simple
nSimple and easy to design with
nRequires only 5 external components
nUses readily available standard inductors
n3.3V, 5.0V, 12V, and adjustable output versions
nAdjustable version output voltage range: 1.21V to 37V
n±1.5% max output voltage tolerance over line and load conditions
nGuaranteed 1A output load current
n0.25Ω DMOS Output Switch
nWide input voltage range: 8V to 40V
n260 kHz fixed frequency internal oscillator
nTTL shutdown capability, low power standby mode
nThermal shutdown and current limit protection
Typical Applications
nSimple High Efficiency (>90%) Step-Down (Buck) Regulator
nEfficient Pre-Regulator for Linear Regulators
nPositive-to-Negative Converter
Typical Application
DS012803-1
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
Windows® is a registered trademark of Microsoft Corporation.
Regulator Voltage Down-Step 1A Efficiency High Converter Power SWITCHER SIMPLE LM2675
© 1998 National Semiconductor Corporation |
DS012803 |
www.national.com |
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Supply Voltage |
45V |
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−0.1V ≤ VSH ≤ 6V |
ON/OFF |
Pin Voltage |
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Switch Voltage to Ground |
−1V |
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Boost Pin Voltage |
VSW + 8V |
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Feedback Pin Voltage |
−0.3V ≤ VFB ≤ 14V |
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ESD Susceptibility |
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Human Body Model (Note 2) |
2 kV |
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Power Dissipation |
Internally Limited |
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Storage Temperature Range |
−65ÊC to +150ÊC |
Lead Temperature |
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M Package |
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Vapor Phase (60s) |
+215ÊC |
Infrared (15s) |
+220ÊC |
N Package (Soldering, 10s) |
+260ÊC |
Maximum Junction Temperature |
+150ÊC |
Operating Ratings
Supply Voltage |
6.5V to 40V |
Junction Temperature Range |
−40ÊC ≤ TJ ≤ +125ÊC |
Electrical Characteristics Specifications with standard type face are for TJ = 25ÊC, and those with bold type face apply over full Operating Temperature Range.
LM2675-3.3
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 4) |
(Note 5) |
(Note 5) |
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SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) |
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VOUT |
Output Voltage |
VIN = 8V to 40V, ILOAD = 20 mA to 1A |
3.3 |
3.251/3.201 |
3.350/3.399 |
V |
VOUT |
Output Voltage |
VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA |
3.3 |
3.251/3.201 |
3.350/3.399 |
V |
η |
Efficiency |
VIN = 12V, ILOAD = 1A |
86 |
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LM2675-5.0
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 4) |
(Note 5) |
(Note 5) |
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SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) |
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VOUT |
Output Voltage |
VIN = 8V to 40V, ILOAD = 20 mA to 1A |
5.0 |
4.925/4.850 |
5.075/5.150 |
V |
VOUT |
Output Voltage |
VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA |
5.0 |
4.925/4.850 |
5.075/5.150 |
V |
η |
Efficiency |
VIN = 12V, ILOAD = 1A |
90 |
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LM2675-12
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 4) |
(Note 5) |
(Note 5) |
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SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) |
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VOUT |
Output Voltage |
VIN = 15V to 40V, ILOAD = 20 mA to 1A |
12 |
11.82/11.64 |
12.18/12.36 |
V |
η |
Efficiency |
VIN = 24V, ILOAD = 1A |
94 |
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% |
LM2675-ADJ
Symbol |
Parameter |
Conditions |
Typ |
Min |
Max |
Units |
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(Note 4) |
(Note 5) |
(Note 5) |
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SYSTEM PARAMETERS Test Circuit Figure 3 (Note 3) |
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VFB |
Feedback |
VIN = 8V to 40V, ILOAD = 20 mA to 1A |
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Voltage |
VOUT Programmed for 5V |
1.210 |
1.192/1.174 |
1.228/1.246 |
V |
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(see Circuit of Figure 3) |
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VFB |
Feedback |
VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA |
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Voltage |
VOUT Programmed for 5V |
1.210 |
1.192/1.174 |
1.228/1.246 |
V |
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(see Circuit of Figure 3) |
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η |
Efficiency |
VIN = 12V, ILOAD = 1A |
90 |
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% |
www.national.com |
2 |
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with bold type face apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable versions and VIN = 24V for the 12V version, and ILOAD = 100 mA.
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Conditions |
Typ |
Min |
Max |
Units |
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DEVICE PARAMETERS |
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IQ |
Quiescent Current |
VFEEDBACK = 8V |
2.5 |
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3.6 |
mA |
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For 3.3V, 5.0V, and ADJ Versions |
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VFEEDBACK = 15V |
2.5 |
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mA |
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For 12V Versions |
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ISTBY |
Standby Quiescent |
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Pin = 0V |
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ON/OFF |
50 |
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100/150 |
µA |
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Current |
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ICL |
Current Limit |
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1.55 |
1.25/1.2 |
2.1/2.2 |
A |
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IL |
Output Leakage Current |
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Pin = 0V |
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VIN = 40V, ON/OFF |
1 |
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25 |
µA |
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VSWITCH = 0V |
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VSWITCH = −1V, ON/OFF |
Pin = 0V |
6 |
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15 |
mA |
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RDS(ON) |
Switch On-Resistance |
ISWITCH = 1A |
0.25 |
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0.30/0.50 |
Ω |
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fO |
Oscillator Frequency |
Measured at Switch Pin |
260 |
225 |
275 |
kHz |
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D |
Maximum Duty Cycle |
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95 |
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% |
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Minimum Duty Cycle |
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0 |
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% |
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IBIAS |
Feedback Bias |
VFEEDBACK = 1.3V |
85 |
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nA |
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Current |
ADJ Version Only |
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VS/D |
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ON/OFF |
Pin |
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1.4 |
0.8 |
2.0 |
V |
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Voltage Thesholds |
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IS/D |
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ON/OFF |
Pin Current |
ON/OFF Pin = 0V |
20 |
7 |
37 |
µA |
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θJA |
Thermal Resistance |
N Package, Junction to Ambient (Note 6) |
95 |
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ÊC/W |
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M Package, Junction to Ambient (Note 6) |
105 |
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Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 3: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2675 is used as shown in Figures 2, 3 test circuits, system performance will be as specified by the system parameters section of the Electrical Characteristics.
Note 4: Typical numbers are at 25ÊC and represent the most likely norm.
Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 6: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will lower thermal resistance further. See Application Information section in the application note accompanying this datasheet and the thermal model in LM267X Made Simple software.
3 |
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Connection Diagram and Ordering Information
8-Lead Package
Top View
DS012803-2
* No Connections
For Surface Mount Package
Order Number
LM2675M-3.3, LM2675M-5.0,
LM2675M-12 or LM2675M-ADJ
See NSC Package Number M08A
For DIP Package
Order Number
LM2675N-3.3, LM2675N-5.0,
LM2675N-12 or LM2675N-ADJ
See NSC Package Number N08E
Typical Performance Characteristics
Normalized |
Line Regulation |
Efficiency |
Output Voltage |
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DS012803-4 |
DS012803-5 |
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DS012803-3 |
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Drain-to-Source |
Switch Current Limit |
Operating |
Resistance |
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Quiescent Current |
DS012803-7
DS012803-6 |
DS012803-8 |
www.national.com |
4 |
Typical Performance Characteristics (Continued)
Standby |
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ON/OFF Threshold |
ON/OFF Pin |
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Quiescent Current |
Voltage |
Current (Sourcing) |
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DS012803-9 |
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DS012803-10 |
DS012803-11 |
Switching Frequency |
Feedback Pin |
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Bias Current |
Peak Switch Current |
DS012803-12
DS012803-13 |
DS012803-14 |
Dropout Voltage Ð 3.3V Option |
Dropout Voltage Ð 5.0V Option |
DS012803-15 |
DS012803-16 |
5 |
www.national.com |
Block Diagram
DS012803-17
* Active Inductor Patent Number 5,514,947
² Active Capacitor Patent Number 5,382,918
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FIGURE 1. |
Typical Performance Characteristics (Circuit of Figure 2) |
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Continuous Mode Switching Waveforms |
Discontinuous Mode Switching Waveforms |
VIN = 20V, VOUT = 5V, ILOAD = 1A |
VIN = 20V, VOUT = 5V, ILOAD = 300 mA |
L = 47 µH, C OUT = 68 µF, C OUTESR = 50 mΩ |
L = 15 µH, C OUT = 68 µF (2x), C OUTESR = 25 mΩ |
DS012803-18 |
DS012803-19 |
A: VSW Pin Voltage, 10 V/div. |
A: VSW Pin Voltage, 10 V/div. |
B: Inductor Current, 0.5 A/div |
B: Inductor Current, 0.5 A/div |
C: Output Ripple Voltage, 20 mV/div AC-Coupled |
C: Output Ripple Voltage, 20 mV/div AC-Coupled |
Horizontal Time Base: 1 µs/div |
Horizontal Time Base: 1 µs/div |
www.national.com |
6 |
Typical Performance Characteristics
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 1A
L = 47 µH, C OUT = 68 µF, C OUTESR = 50 mΩ
(Circuit of Figure 2) (Continued)
Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V,
L = 47 µH, C OUT = 68 µF, C OUTESR = 50 mΩ
DS012803-20
DS012803-21
A: Output Voltage, 100 mV/div, AC-Coupled.
B: Load Current: 200 mA to 1A Load Pulse
A: Output Voltage, 100 mV/div, AC-Coupled.
B: Load Current: 100 mA to 400 mA Load Pulse
Horizontal Time Base: 50 µs/div
Horizontal Time Base: 200 µs/div
Test Circuit and Layout Guidelines
DS012803-22
CIN - 22 µF, 50V Tantalum, Sprague ª199D Seriesº
COUT - 47 µF, 25V Tantalum, Sprague ª595D Seriesº
D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F
L1 - 68 µH Sumida #RCR110D-680L
CB - 0.01 µF, 50V Ceramic
FIGURE 2. Standard Test Circuits and Layout Guides
Fixed Output Voltage Versions
7 |
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