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LM2575
Micrel, Inc.
LM2575
52kHz Simple 1A Buck Regulator
General Description
The LM2575 series of monolithic integrated circuits provide all the active functions for a step-down (buck) switching regulator. Fixed versions are available with a 3.3V, 5V, 12V, fixed output. Adjustable versions have an output voltage range from 1.23V to 37V. Both versions are capable of driving a 1A load with excellent line and load regulation. These regulators are simple to use because they require a minimum number of external components and include internal frequency compensation and a fixed-frequency oscillator. The LM2575 series offers a high efficiency replacement for popular three-terminal adjustable linear regulators. It substantially reduces the size of the heat sink, and in many cases no heat sink is required. A standard series of inductors available from several different manufacturers are ideal for use with the LM2575 series. This feature greatly simplifies the design of switch-mode power supplies. The feedback voltage is guaranteed to 2% tolerance for adjustable versions, and the output voltage is guaranteed to 3% for fixed versions, within specified input voltages and output load conditions. The oscillator frequency is guaranteed to 10%. External shutdown is included, featuring less than 200A standby current. The output switch includes cycle-bycycle current limiting and thermal shutdown for full protection under fault conditions.
Features
* 3.3V, 5V, 12V, and adjustable output versions * Voltage over specified line and load conditions: Fixed version: 3% max. output voltage Adjustable version: 2% max. feedback voltage * Guaranteed 1A output current * Wide input voltage range: 4V to 40V * Wide output voltage range 1.23V to 37V * Requires only 4 external components * 52kHz fixed frequency internal oscillator * Low power standby mode IQ typically <200A * 80% efficiency (adjustable version typically >80%) * Uses readily available standard inductors * Thermal shutdown and current limit protection * 100% electrical thermal limit burn-in
Applications
Simple high-efficiency step-down (buck) regulator Efficient pre-regulator for linear regulators On-card switching regulators Positive to negative converter (inverting Buck-Boost) Isolated Flyback Converter using minimum number of external components * Negative Boost Converter * * * * *
Typical Applications
870 20
7V-40V Unregulated DC Input
+VIN + CIN 100F
LM2575-5.0 Output L1 2 330H 3 5 Gnd On/Off D1 1N5822
1
4
Feedback
+5V, 1A Regulated Output + COUT 330F
7V-40V Unregulated DC Input
1
4 LM2575
Feedback
+VIN + CIN 100F
3 5 Gnd On/Off
Output L1 2 330H D1 1N5822
+5V, 1A Regulated Output + COUT 330F R2 3.09k R1 1k
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package R2 VOUT = 1.23 1 + R1
(
)
Fixed Regulator in Typical Application
Adjustable Regulator in Fixed Output Application
Micrel, Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
April 2005
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M9999-042205
LM2575
Micrel, Inc.
Ordering Information
Standard Part Number Pb-Free Contact Factory Contact Factory Contact Factory Contact Factory LM2575YWM* LM2575-3.3YWM LM2575-5.0YWM LM2575-12YWM LM2575WT*/**

Temperature Range -40C to +85 C -40C to +85 C -40C to +85 C -40C to +85 C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package 16-pin Plastic DIP 16-pin Plastic DIP 16-pin Plastic DIP 16-pin Plastic DIP 24-pin Wide SOIC 24-pin Wide SOIC 24-pin Wide SOIC 24-pin Wide SOIC 5-lead TO-220 5-lead TO-220 5-lead TO-220 5-lead TO-220 5-lead TO-263 5-lead TO-263 5-lead TO-263 5-lead TO-263
LM2575BN* LM2575-3.3BN LM2575-5.0BN LM2575-12BN LM2575BWM* LM2575-3.3BWM LM2575-5.0BWM LM2575-12BWM LM2575BT*
LM2575-3.3BT LM2575-5.0BT LM2575-12BT LM2575BU*
LM2575-3.3WT** LM2575-5.0WT** LM2575-12WT** LM2575WU*/** LM2575-3.3WU** LM2575-5.0WU** LM2575-12WU**
LM2575-3.3BU LM2575-5.0BU LM2575-12BU
* Adjustable output regulators. **Pb-Free RoHS compliant with "hot-melting solder" exemption. Contact factory for bent or staggered leads option.
Pin Configurations
5-LEAD TO-220 (T)
GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN GND
5-LEAD TO-263 (U)
5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN
24-LEAD SOIC (WM)
16-LEAD DIP (N)
NC NC OUTPUT NC GND NC FB NC 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VIN NC GND GND GND GND NC ON/OFF
PWR GND NC NC NC NC NC FB SIG GND NC ON/OFF NC PWR GND
1 2 3 4 5 6 7 8 9 10 11 12
24 23 22 21 20 19 18 17 16 15 14 13
NC NC NC NC NC NC OUTPUT OUTPUT NC VIN VIN NC
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Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Maximum Supply Voltage ON/OFF Pin Input Voltage Output Voltage to Ground (Steady State) Power Dissipation Storage Temperature Range Minimum ESD Rating C = 100pF, R = 1.5k FB Pin Lead Temperature (soldering, 10 sec.) Maximum Junction Temperature 45V -0.3V V +40V -1V Internally Limited -65C to +150C 2 kV 1 kV 260C 150C
Operating Ratings
Temperature Range Supply Voltage -40C TJ +125C 40V
Electrical Characteristics
Specifications with standard typeface are for TJ = 25C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V, and ILOAD = 200mA. LM2575 Parameter Conditions Typ Limit (Note 2) Units (Limits)
Symbol
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 VOUT Feedback Voltage VIN = 12V , ILOAD = 0.2A VOUT = 5V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 5V VIN = 12V, ILOAD = 1A, VOUT = 5V VIN = 12V , ILOAD = 0.2A VOUT = 3.3V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 3.3V VIN = 12V, ILOAD = 1A VIN = 12V , ILOAD = 0.2A VOUT = 5V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 5V VIN = 12V, ILOAD = 1A VIN = 25V , ILOAD = 0.2A VOUT = 12V 0.2A ILOAD 1A, 15V VIN 40V VOUT = 12V VIN = 25V, ILOAD = 1A 1.230 1.217 1.243 1.230 1.193/1.180 1.267/1.280 82 V V(min) V(max) V V(min) V(max) %
VOUT
Feedback Voltage LM2575 Efficiency
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 3.3 3.234 3.366 3.3 3.168/3.135 3.432/3.465 75 V V(min) V(max) V V(min) V(max) %
VOUT
Output Voltage LM2575-3.3 Efficiency
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 5.0 4.900 5.100 5.0 4.800/4.750 5.200/5.250 82 V V(min) V(max) V V(min) V(max) %
VOUT
Output Voltage LM2575-5.0 Efficiency
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 12 11.760 12.240 12 11.520/11.400 12.480/12.600 88 V V(min) V(max) V V(min) V(max) %
VOUT
Output Voltage LM2575-12 Efficiency
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LM2575
Micrel, Inc.
Electrical Characteristics (continued)
LM2575 Symbol Parameter Conditions Typ Limit (Note 2) Units (Limits)
DEVICE PARAMETERS, ADJUSTABLE REGULATOR IB fO Feedback Bias Current VOUT = 5V 50 100/500 nA
DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS Oscillator Frequency 52 47/42 58/63 Saturation Voltage Max Duty Cycle (ON) Current Limit IOUT = 1A (Note 4) (Note 5) Peak Current, tON 3s (Note 4) 0.9 1.2/1.4 98 93 ICL 2.2 1.7/1.3 3.0/3.2 2 7.5 30 5 10 Standby Quiescent Current Thermal Resistance ON/OFF Pin = 5V (OFF) T Package, Junction to Ambient (Note 7) T Package, Junction to Ambient (Note 8) T Package, Junction to Case N Package, Junction to Ambient (Note 9) WM Package, Junction to Amb. (Note 9) 50 200 65 45 2 85 100 kHz kHz (min) kHz (max) V V(max) % %(min) A A(min) A(max) mA(max) mA mA(max) mA mA(max) A A(max) C/W
VSAT DC
IL
Output Leakage Current
VIN = 40V, (Note 6), (Note 6)
Output = 0V Output = -1V Output = -1V
IQ ISTBY JA JA JC JA JA
Quiescent Current
(Note 6)
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LM2575
LM2575 Symbol Parameter Conditions Typ Limit (Note 2)
Micrel, Inc.
Units (Limits)
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 VIH VIL IIH IIL
Note 1:
ON/OFF Pin Logic Input Level ON /OFF Pin Logic Current
VOUT = 0V VOUT = 5V ON /OFF Pin = 5V (OFF) ON/OFF Pin = 0V (ON)
1.4 1.2 4
2.2/2.4 1.0/0.8 30
V(min) V(max) A A(max) A A(max)
0.01 10
Absolute Maximum Rating 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. 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 extreme are guaranteed via testing. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM2575/LM1575 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical Characteristics. Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output. Feedback (pin 4) removed from output and connected to 0V. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2" leads in a socket, or on PC board with minimum copper area. Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4" leads soldered to PC board containing approximately 4 square inches of copper area surrounding the leads. Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower thermal resistance further.
Note 2: Note 3:
Note 4: Note 5: Note 6: Note 7: Note 8: Note 9:
Typical Performance Characteristics
Normalized Feedback Voltage*
NORMALIZED FEEDBACK VOLTAGE (mV)
Feedback Voltage vs Duty Cycle*
20
FEEDBACK VOLTAGE CHANGE (mV)
25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 VIN = 12V ILOAD = 200mA Normalized to TJ = 25C
15 10 5 0 -5 -10 -15 -20 0 20 40
ILOAD = 200 mA
VIN = 40V
VIN = 7V
25 50 75 100 125 150
60
80
100
JUNCTION TEMPERATURE (C)
DUTY CYCLE (%)
* Adjustable version only
April 2005
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M9999-042205
LM2575
Micrel, Inc.
(Circuit of Figure 1)
Typical Performance Characteristics (continued)
Supply Current vs. Duty Cycle
Supply Current
20 18
SUPPLY CURRENT (mA)
Standby Quiescent Current
STANDBY QUIESCENT CURRENT (A)
SUPPLY CURRENT (mA)
16 14 12 10 8 6 4 0 10 20 30
Measured at Ground Pin TJ = 25C VOUT = 5V
20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 VIN from 7V to 40V 0 20 40 60 80 100 ILOAD = 200 mA
200
VIN = 40V
150 VON/OFF = 5V VIN = 12V 50
100
ILOAD to 1A
40
50
60
0
0 -75 -50 -25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (C)
INPUT VOLTAGE (V)
DUTY CYCLE (%)
Current Limit
3 VI N = 25V
SATURATION VOLTAGE (V) OUTPUT CURRENT (A)
Switch Saturation Voltage
1.2 100 95 1.0 -55C -40C 0.8 25C
EFFICIENCY (%)
Efficiency
VOUT = 12V
1A
90 85 80 75 70 65 60 0 0.2 0.4 0.6 0.8 1.0 0 5 10 15 20 25 30
INPUT VOLTAGE (V)
2
200 mA
200 mA
1
1A VOUT = 3V
0.6 125C 150C 0.4
SWITCH CURRENT (A)
0 -75 -50 -25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (C)
35 40
Minimum Operating Voltage
NORMALIZED FEEDBACK VOLTAGE (mV)
Line Regulation
Normalized to V IN = 10V VOUT = 5V ILOAD = 500mA TJ = 25
STANDBY QUIESCENT CURRENT (A)
Feedback Pin Current
100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150
5.0 4.5 4.0
INPUT VOLTAGE (V)
14 12 10 8 6 4 2 0 -2 -4 -6 0
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 VOUT = 1.23V ILOAD = 200 mA 25 50 75 100 125 150
5
10
15
20
25
30
JUNCTION TEMPERATURE (C)
INPUT VOLTAGE (V)
JUNCTION TEMPERATURE (C)
Normalized Output Voltage
100
OUTPUT VOLTAGE CHANGE (mV)
Oscillator Frequency
+8 +6
NORMALIZED FREQUENCY (%)
Dropout Voltage
2.0
INPUT-OUTPUT DIFFERENTIAL (V)
75 50 25 0 -25 -50 -75
VIN = 12V ILOAD = 200mA Normalized to TJ = 25C
Normalized at 25C 1.5 ILOAD = 1A
VOUT = 5% R IND = 0.2
+4 +2 0 -2 -4 --6 VIN = 40V
1.0 ILOAD = 200 mA
0.5
-100 -75 -50 -25 0
25 50 75 100 125 150
VIN = 12V -8 -75 -50 -25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (C)
0 -75 -50 -25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (C)
JUNCTION TEMPERATURE (C)
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April 2005
LM2575
Micrel, Inc.
Typical Performance Characteristics (Circuit of Figure 1)
Load Transient Response Switching Waveforms
+100mV Output Voltage Change 0 -100mV
A
10V 0
B
1A 0
C 1.0A Output Current 0.5A 0 V OUT = 5V D 100S/div.
1A .5A 0
V OUT = 5V VIN = 20V A: Output pin voltage 10V/div B: Output pin current 1A/div C: Inductor current 0.5A/div D: Output ripple voltage 20 mV/div. AC coupled
Test Circuits and Layout Guidelines
FEEDBACK +VIN 4
Horizontal Time Base: 5s/div
LM2575
1 7V - 40V UNREGULATED DC INPUT + 100 F C IN GND 3 ON/OFF 5 2
OUTPUT
L1 330 H D1 MBR360 +
VOUT 5.00V C OUT 470F R2 R1 L O A D
C IN -- 100F, 75V Aluminum Electrolytic C OUT -- 470F, 15V Aluminum Electrolytic D1 -- Schottky, MBR360 L1 -- 330H, 415-0926 (AIE) R1 -- 1k, 0.01% R2 -- 3.065k, 0.01% 5-pin TO-220 socket--2936 (Loranger Mfg. Co.) 4-pin TO-3 socket--8112-AG7 (Augat Inc.)
FEEDBACK +VIN 4
LM2575-5.0
1 7V - 40V UNREGULATED DC INPUT + 100 F C IN GND 3 ON/OFF 5 2
OUTPUT
L1 330 H D1 MBR360 +
VOUT 5.00V C OUT 220F L O A D
C IN -- 100F, 75V Aluminum Electrolytic C OUT -- 330F, 15V Aluminum Electrolytic D1 -- Schottky, MBR360 L1 -- 330H, 415-0926 (AIE) 5-pin TO-220 socket--2936 (Loranger Mfg. Co.) 4-pin TO-3 socket--8112-AG7 (Augat Inc.)
Note: Pin numbers are for TO-220 Package
Figure 1.
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transients which can cause problems. For minimal stray inductance and ground loops, the length of the leads indicated by heavy lines should be kept as short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results.
Block Diagrams
VIN FEEDBACK
1 4
3.1k
INTERNAL REGULATOR
ON/OFF
5
ON/OFF
VIN
1
INTERNAL REGULATOR
ON/OFF
5
ON/OFF
FIXED GAIN ERROR AMP
FIXED GAIN ERROR AMP COMPARATOR 1 AMP SWITCH FEEDBACK
+
1.0k
4
+ + -
COMPARATOR
1 AMP SWITCH
-
+ -
DRIVER
DRIVER
2
1.23V BAND-GAP REFERENCE
OUTPUT 1.23V BAND-GAP REFERENCE
2
OUTPUT
52 kHz OSCILLATOR
RESET
THERMAL SHUTDOWN
CURRENT LIMIT
3
GND
52 kHz OSCILLATOR
RESET
THERMAL SHUTDOWN
CURRENT LIMIT
3
GND
Note: Pin numbers are for the TO-220 package
Fixed Regulator April 2005 7
Adjustable Regulator
M9999-042205
LM2575
Micrel, Inc.
Package Information
0.780 MAX (19.812) PIN 1 0.030-0.110 RAD (0.762-2.794)
.2500.005 (6.3500.127)
0.0250.015 (0.6350.381) 0.1300.005 (3.3020.127) 0.040 TYP (1.016)
0.020 (0.508)
0.290-0.320 (7.336-8.128)
0-10 0.020 MIN (0.508) 0.125 MIN (3.175) 0.009-0.015 (0.229-0.381) 0.0180.003 (0.4570.076) 0.1000.010 (2.5400.254) +0.025 -0.015 +0.635 8.255 -0.381 0.325
(
)
16-Pin DIP (N)
PIN 1
0.301 (7.645) 0.297 (7.544)
DIMENSIONS: INCHES (MM)
0.027 (0.686) 0.031 (0.787)
0.050 (1.270) TYP
0.016 (0.046) TYP
0.094 (2.388) 0.090 (2.286)
0.609 (15.469) 0.605 (15.367)
7 TYP 0.015 R (0.381) 0.015 (0.381) SEATING MIN PLANE
0.103 (2.616) 0.099 (2.515)
0.297 (7.544) 0.293 (7.442)
0.022 (0.559) 0.018 (0.457) 5 TYP 10 TYP
0.330 (8.382) 0.326 (8.280) 0.032 (0.813) TYP 0.408 (10.363) 0.404 (10.262)
24-Pin Wide SOP (WM)
M9999-042205
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April 2005
LM2575
0.150 D 0.005 (3.81 D 0.13) 0.400 0.015 (10.16 0.38) 0.108 0.005 (2.74 0.13) 0.241 0.017 (6.12 0.43) 0.177 0.008 (4.50 0.20) 0.050 0.005 (1.27 0.13)
Micrel, Inc.
0.578 0.018 (14.68 0.46)
SEATING PLANE
7 Typ. 0.550 0.010 (13.97 0.25)
0.067 0.005 (1.70 0.127) 0.268 REF (6.81 REF)
0.032 0.005 (0.81 0.13)
0.018 0.008 (0.46 0.20)
0.103 0.013 (2.620.33)
Dimensions: inch (mm)
5-Lead TO-220 (T)
0.4050.005 0.065 0.010 202 0.0500.005
0.176 0.005 0.060 0.005
0.3600.005 0.6000.025 SEATING PLANE 0.004 +0.004 -0.008
0.0670.005 DIM. = INCH
0.032 0.003
8 MAX 0.015 0.002
0.100 0.01
5-Lead TO-263 (T)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 474-1000
WEB
http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 1999 Micrel Incorporated
April 2005
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M9999-042205

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