NSC LM2596SX-3.3, LM2596SX-12, LM2596S-ADJ, LM2596S-5.0, LM2596S-3.3 Datasheet
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December 1997
LM2596
SIMPLE SWITCHER® Power Converter 150 kHz
3A Step-Down Voltage Regulator
General Description
The LM2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 3A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, and an adjustable output version.
Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation², and a fixed-frequency oscillator.
The LM2596 series operates at a switching frequency of 150 kHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Available in a standard 5-lead TO-220 package with several different lead bend options, and a 5-lead TO-263 surface mount package.
A standard series of inductors are available from several different manufacturers optimized for use with the LM2596 series. This feature greatly simplifies the design of switch-mode power supplies.
Other features include a guaranteed ±4% tolerance on output voltage under specified input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 80 µA standby current. Self protection features include a two stage frequency reducing current limit for the output switch and an over temperature shutdown for complete protection under fault conditions.
Features
n3.3V, 5V, 12V, and adjustable output versions
nAdjustable version output voltage range, 1.2V to 37V
±4% max over line and load conditions
nAvailable in TO-220 and TO-263 packages
nGuaranteed 3A output load current
nInput voltage range up to 40V
nRequires only 4 external components
nExcellent line and load regulation specifications
n150 kHz fixed frequency internal oscillator
nTTL shutdown capability
nLow power standby mode, IQ typically 80 µA
nHigh efficiency
nUses readily available standard inductors
nThermal shutdown and current limit protection
Applications
nSimple high-efficiency step-down (buck) regulator
nOn-card switching regulators
nPositive to negative converter
Note: ²Patent Number 5,382,918.
Typical Application (Fixed Output Voltage Versions)
DS012583-1
SIMPLE SWITCHER® and Switchers Made Simple® are registered trademarks of National Semiconductor Corporation.
Regulator Voltage Down-Step 3A kHz 150 Converter Power SWITCHER SIMPLE LM2596
© 1999 National Semiconductor Corporation |
DS012583 |
www.national.com |
Connection Diagrams and Ordering Information
Bent and Staggered Leads, Through Hole |
Surface Mount Package |
Package |
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5-Lead TO-220 (T) |
5-Lead TO-263 (S) |
DS012583-2 |
DS012583-3 |
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Order Number LM2596T-3.3, LM2596T-5.0, |
Order Number LM2596S-3.3, LM2596S-5.0, |
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LM2596S-12 or LM2596S-ADJ |
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LM2596T-12 or LM2596T-ADJ |
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See NS Package Number TS5B |
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See NS Package Number T05D |
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www.national.com |
2 |
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Maximum Supply Voltage |
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45V |
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ON |
/OFF Pin Input Voltage |
−0.3 |
≤ V ≤ +25V |
Feedback Pin Voltage |
−0.3 |
≤ V ≤+25V |
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Output Voltage to Ground |
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(Steady State) |
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−1V |
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Power Dissipation |
Internally limited |
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Storage Temperature Range |
−65ÊC to +150ÊC |
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ESD Susceptibility |
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Human Body Model (Note 2) |
2 kV |
Lead Temperature |
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S Package |
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Vapor Phase (60 sec.) |
+215ÊC |
Infrared (10 sec.) |
+245ÊC |
T Package (Soldering, 10 sec.) |
+260ÊC |
Maximum Junction Temperature |
+150ÊC |
Operating Conditions
Temperature Range |
−40ÊC ≤ TJ ≤ +125ÊC |
Supply Voltage |
4.5V to 40V |
LM2596-3.3
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
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LM2596-3.3 |
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Typ |
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Limit |
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(Note 3) |
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(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
4.75V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A |
3.3 |
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V |
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3.168/3.135 |
V(min) |
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3.432/3.465 |
V(max) |
η |
Efficiency |
VIN = 12V, ILOAD = 3A |
73 |
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% |
LM2596-5.0
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
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LM2596-5.0 |
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Conditions |
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Typ |
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Limit |
(Limits) |
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(Note 3) |
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(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
7V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A |
5.0 |
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V |
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4.800/4.750 |
V(min) |
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5.200/5.250 |
V(max) |
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η |
Efficiency |
VIN = 12V, ILOAD = 3A |
80 |
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% |
LM2596-12
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
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LM2596-12 |
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Conditions |
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Typ |
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Limit |
(Limits) |
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(Note 3) |
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(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
15V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A |
12.0 |
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V |
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11.52/11.40 |
V(min) |
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12.48/12.60 |
V(max) |
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η |
Efficiency |
VIN = 12V, ILOAD = 3A |
90 |
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% |
3 |
www.national.com |
LM2596-ADJ
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
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LM2596-ADJ |
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Conditions |
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Typ |
Limit |
(Limits) |
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(Note 3) |
(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VFB |
Feedback Voltage |
4.5V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A |
1.230 |
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V |
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VOUT programmed for 3V. Circuit of Figure 1 |
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1.193/1.180 |
V(min) |
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1.267/1.280 |
V(max) |
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η |
Efficiency |
VIN = 12V, VOUT = 3V, ILOAD = 3A |
73 |
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All Output Voltage Versions Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD = 500 mA
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LM2596-XX |
Units |
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Symbol |
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Parameter |
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Conditions |
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Typ |
Limit |
(Limits) |
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(Note 3) |
(Note 4) |
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DEVICE PARAMETERS |
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Ib |
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Feedback Bias Current |
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Adjustable Version Only, VFB = 1.3V |
10 |
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nA |
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50/100 |
nA (max) |
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fO |
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Oscillator Frequency |
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(Note 6) |
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150 |
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kHz |
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127/110 |
kHz(min) |
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173/173 |
kHz(max) |
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VSAT |
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Saturation Voltage |
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IOUT = 3A (Notes 7, 8) |
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1.16 |
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V |
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1.4/1.5 |
V(max) |
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DC |
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Max Duty Cycle (ON) |
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(Note 8) |
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100 |
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% |
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Min Duty Cycle (OFF) |
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(Note 9) |
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0 |
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ICL |
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Current Limit |
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Peak Current (Notes 7, 8) |
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4.5 |
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A |
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3.6/3.4 |
A(min) |
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6.9/7.5 |
A(max) |
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IL |
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Output Leakage Current |
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Output = 0V (Notes 7, 9) |
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50 |
µA(max) |
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Output = −1V (Note 10) |
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2 |
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mA |
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30 |
mA(max) |
IQ |
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Quiescent Current |
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(Note 9) |
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5 |
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mA |
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10 |
mA(max) |
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ISTBY |
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Standby Quiescent |
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ON/OFF pin = 5V (OFF) |
(Note 10) |
80 |
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µA |
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Current |
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200/250 |
µA(max) |
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θJC |
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Thermal Resistance |
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TO-220 or TO-263 Package, Junction to Case |
2 |
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ÊC/W |
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θJA |
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TO-220 Package, Junction to Ambient (Note 11) |
50 |
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ÊC/W |
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θJA |
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TO-263 Package, Junction to Ambient (Note 12) |
50 |
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ÊC/W |
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θJA |
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TO-263 Package, Junction to Ambient (Note 13) |
30 |
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ÊC/W |
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θJA |
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TO-263 Package, Junction to Ambient (Note 14) |
20 |
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ÊC/W |
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ON/OFF CONTROL Test Circuit Figure 1 |
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ON |
/OFF Pin Logic Input |
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1.3 |
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V |
VIH |
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Threshold Voltage |
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Low (Regulator ON) |
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0.6 |
V(max) |
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VIL |
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High (Regulator OFF) |
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2.0 |
V(min) |
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4 |
All Output Voltage Versions
Electrical Characteristics (Continued)
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD = 500 mA
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LM2596-XX |
Units |
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Symbol |
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Parameter |
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Conditions |
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Typ |
Limit |
(Limits) |
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(Note 3) |
(Note 4) |
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ON/OFF CONTROL Test Circuit Figure 1 |
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IH |
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ON |
/OFF Pin Input Current |
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VLOGIC = 2.5V (Regulator OFF) |
5 |
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µA |
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15 |
µA(max) |
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IL |
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VLOGIC = 0.5V (Regulator ON) |
0.02 |
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µA |
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5 |
µA(max) |
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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 do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 25ÊC and represent the most likely norm.
Note 4: 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 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. When the LM2596 is used as shown in the Figure 1 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.
Note 6: The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the severity of current overload.
Note 7: No diode, inductor or capacitor connected to output pin.
Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force the output transistor switch OFF.
Note 10: VIN = 40V.
Note 11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads soldered to a printed circuit board with (1 oz.) copper area of approximately 1 in2.
Note 12: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in2 of (1 oz.) copper area.
Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in2 of (1 oz.) copper area.
Note 14: Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in2 of (1 oz.) copper area on the LM2596S side of the board, and approximately 16 in2 of copper on the other side of the p-c board. See Application Information in this data sheet and the thermal model in Switchers Made Simple™ version 4.3 software.
Typical Performance Characteristics (Circuit of Figure 1)
Normalized |
Line Regulation |
Efficiency |
Output Voltage |
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DS012583-5 |
DS012583-6 |
DS012583-4
5 |
www.national.com |
Typical Performance Characteristics (Circuit of Figure 1) (Continued)
Switch Saturation |
Switch Current Limit |
Dropout Voltage |
Voltage |
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DS012583-8 |
DS012583-9 |
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DS012583-7 |
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Operating |
Shutdown |
Minimum Operating |
Quiescent Current |
Quiescent Current |
Supply Voltage |
DS012583-10 |
DS012583-11 |
DS012583-12 |
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ON /OFF Threshold |
ON /OFF Pin |
Switching Frequency |
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Voltage |
Current (Sinking) |
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DS012583-15
DS012583-13 |
DS012583-14 |
www.national.com |
6 |
Typical Performance Characteristics (Circuit of Figure 1) (Continued)
Feedback Pin
Bias Current
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DS012583-16 |
Typical Performance Characteristics |
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Continuous Mode Switching Waveforms |
Discontinuous Mode Switching Waveforms |
VIN = 20V, VOUT = 5V, ILOAD = 2A |
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L = 32 µH, C OUT = 220 µF, C OUT ESR = 50 mΩ |
VIN = 20V, VOUT = 5V, ILOAD = 500 mA |
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L = 10 µH, C OUT = 330 µF, C OUT ESR = 45 mΩ |
DS012583-17
A:Output Pin Voltage, 10V/div.
B:Inductor Current 1A/div.
C:Output Ripple Voltage, 50 mV/div.
Horizontal Time Base: 2 µs/div.
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 500 mA to 2A
L = 32 µH, C OUT = 220 µF, C OUT ESR = 50 mΩ
DS012583-19
A:Output Voltage, 100 mV/div. (AC)
B:500 mA to 2A Load Pulse
Horizontal Time Base: 100 µs/div.
DS012583-18
A:Output Pin Voltage, 10V/div.
B:Inductor Current 0.5A/div.
C:Output Ripple Voltage, 100 mV/div.
Horizontal Time Base: 2 µs/div.
Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 500 mA to 2A
L = 10 µH, C OUT = 330 µF, C OUT ESR = 45 mΩ
DS012583-20
A:Output Voltage, 100 mV/div. (AC)
B:500 mA to 2A Load Pulse
Horizontal Time Base: 200 µs/div.
7 |
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Test Circuit and Layout Guidelines
Fixed Output Voltage Versions
DS012583-22
CIN |
Ð 470 µF, 50V, Aluminum Electrolytic Nichicon ªPL Seriesº |
COUT |
Ð 220 µF, 25V Aluminum Electrolytic, Nichicon ªPL Seriesº |
D1 Ð 5A, 40V Schottky Rectifier, 1N5825
L1 Ð 68 µH, L38
Adjustable Output Voltage Versions
DS012583-23
where VREF = 1.23V
Select R1 to be approximately 1 kΩ, use a 1% resistor for best stability.
CIN |
Ð 470 µF, 50V, Aluminum Electrolytic Nichicon ªPL Seriesº |
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COUT |
Ð 220 µF, 35V Aluminum Electrolytic, Nichicon ªPL Seriesº |
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D1 Ð 5A, 40V Schottky Rectifier, 1N5825 |
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L1 |
Ð 68 µH, L38 |
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R1 |
Ð 1 k Ω, 1% |
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CFF |
Ð See Application Information Section |
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FIGURE 1. Standard Test Circuits and Layout Guides |
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As in any switching regulator, layout is very important. Rap- |
If open core inductors are used, special care must be |
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idly switching currents associated with wiring inductance can |
taken as to the location and positioning of this type of induc- |
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generate voltage transients which can cause problems. For |
tor. Allowing the inductor flux to intersect sensitive feedback, |
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minimal inductance and ground loops, the wires indicated by |
lC groundpath and COUT wiring can cause problems. |
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heavy lines should be wide printed circuit traces and |
When using the adjustable version, special care must be |
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should be kept as short as possible. For best results, ex- |
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taken as to the location of the feedback resistors and the as- |
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ternal |
components should be located as close to the |
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sociated wiring. Physically locate both resistors near the IC, |
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switcher lC as possible using ground plane construction or |
and route the wiring away from the inductor, especially an |
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single point grounding. |
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open core type of inductor. (See application section for more |
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information.) |
www.national.com |
8 |
LM2596 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version) |
EXAMPLE (Fixed Output Voltage Version) |
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Given: |
Given: |
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VOUT = Regulated Output Voltage (3.3V, 5V or 12V) |
VOUT = 5V |
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VIN(max) = Maximum DC Input Voltage |
VIN(max) = 12V |
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ILOAD(max) = Maximum Load Current |
ILOAD(max) = 3A |
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1. Inductor Selection (L1) |
1. Inductor Selection (L1) |
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A. Select the correct inductor value selection guide from Fig- |
A. Use the inductor selection guide for the 5V version shown |
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ures Figure 4, Figure 5, or Figure 6. (Output voltages of 3.3V, |
in Figure 5. |
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5V, or 12V respectively.) For all other voltages, see the de- |
B. From the inductor value selection guide shown in Figure 5, |
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sign procedure for the adjustable version. |
the inductance region intersected by the 12V horizontal line |
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B. From the inductor value selection guide, identify the induc- |
and the 3A vertical line is 33 µH, and the inductor code is |
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tance region intersected by the Maximum Input Voltage line |
L40. |
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and the Maximum Load Current line. Each region is identified |
C. The inductance value required is 33 µH. From the table in |
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by an inductance value and an inductor code (LXX). |
Figure 8, go to the L40 line and choose an inductor part num- |
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C. Select an appropriate inductor from the four manufactur- |
ber from any of the four manufacturers shown. (In most in- |
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er's part numbers listed in Figure 8. |
stance, both through hole and surface mount inductors are |
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available.) |
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2. Output Capacitor Selection (COUT) |
2. Output Capacitor Selection (COUT) |
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A. In the majority of applications, low ESR (Equivalent Series |
A. See section on output capacitors in application infor- |
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Resistance) electrolytic capacitors between 82 µF and |
mation section. |
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820 µF and low ESR solid tantalum capacitors between |
B. From the quick design component selection table shown |
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10 µF and 470 µF provide the best results. This capacitor |
in Figure 2, locate the 5V output voltage section. In the load |
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should be located close to the IC using short capacitor leads |
current column, choose the load current line that is closest to |
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and short copper traces. Do not use capacitors larger than |
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the current needed in your application, for this example, use |
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820 µF . |
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the 3A line. In the maximum input voltage column, select the |
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For additional information, see section on output capaci- |
line that covers the input voltage needed in your application, |
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tors in application information section. |
in this example, use the 15V line. Continuing on this line are |
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B. To simplify the capacitor selection procedure, refer to the |
recommended inductors and capacitors that will provide the |
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quick design component selection table shown in Figure 2. |
best overall performance. |
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This table contains different input voltages, output voltages, |
The capacitor list contains both through hole electrolytic and |
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and load currents, and lists various inductors and output ca- |
surface mount tantalum capacitors from four different capaci- |
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pacitors that will provide the best design solutions. |
tor manufacturers. It is recommended that both the manufac- |
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C. The capacitor voltage rating for electrolytic capacitors |
turers and the manufacturer's series that are listed in the |
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should be at least 1.5 times greater than the output voltage, |
table be used. |
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and often much higher voltage ratings are needed to satisfy |
In this example aluminum electrolytic capacitors from several |
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the low ESR requirements for low output ripple voltage. |
different manufacturers are available with the range of ESR |
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D. For computer aided design software, see Switchers Made |
numbers needed. |
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Simple™ version 4.3 or later. |
330 µF |
35V |
Panasonic HFQ Series |
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330 µF |
35V |
Nichicon PL Series |
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C. For a 5V output, a capacitor voltage rating at least 7.5V or |
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more is needed. But even a low ESR, switching grade, |
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220 µF 10V aluminum electrolytic capacitor would exhibit ap- |
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proximately 225 mΩ of ESR (see the curve in Figure 14 for |
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the ESR vs voltage rating). This amount of ESR would result |
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in relatively high output ripple voltage. To reduce the ripple to |
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1% of the output voltage, or less, a capacitor with a higher |
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value or with a higher voltage rating (lower ESR) should be |
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selected. A 16V or 25V capacitor will reduce the ripple volt- |
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age by approximately half. |
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9 |
www.national.com |
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