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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 switchmode 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-by-cycle current limiting and thermal shutdown for full protection under fault conditions. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
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
7V-40V Unregulated DC Input 1 4 Feedback +5V, 1A Regulated Output + COUT 330F
7V-40V Unregulated DC Input 1 4 LM2575 Feedback +5V, 1A Regulated Output + COUT 330F R2 3.09k R1 1k
+VIN + CIN 100F
LM2575-5.0 Output L1 2 330H 3 5 Gnd On/Off D1 1N5822
+VIN + CIN 100F
Output L1 2 330H D1 1N5822
3 5 Gnd On/Off
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package VOUT = 1.23 1 + R2 R1
(
)
Fixed Regulation in Typical Application
Adjustable Regulation 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
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Micrel, Inc.
LM2575
Ordering Information
Part Number Standard 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 LM2575BU* LM2575-3.3BU LM2575-5.0BU LM2575-12BU
Notes: * **
Pb-Free / RoHS Compliant Contact Factory Contact Factory LM2575-5.0YN LM2575-12YN LM2575YWM* LM2575-3.3YWM LM2575-5.0YWM LM2575-12YWM LM2575WT*/**

Temperature Range -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 to +85C -40 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-Pin TO-220 5-Pin TO-220 5-Pin TO-220 5-Pin TO-220 5-Pin TO-263 5-Pin TO-263 5-Pin TO-263 5-Pin TO-263
LM2575-3.3WT** LM2575-5.0WT** LM2575-12WT** LM2575WU*/** LM2575-3.3WU** LM2575-5.0WU** LM2575-12WU**
LM2575-12BT
Adjustable output regulators. RoHS compliant with "high-melting solder" exemption. Contact factory for bent or staggered leads option.
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LM2575
Pin Configuration
5 ON/OFF 4 FB 3 GND 2 OUT 1 VIN
5-Pin TO-220 (T)
5 4 3 2 1
5-Pin TO-263 (U)
ON/OFF FB GND OUT VIN
TAB
TAB
PWR GND NC NC NC
1 2 3 4 5 6 7 8 9
24 NC 23 NC 22 NC 21 NC 20 NC 19 NC 18 OUT 17 OUT 16 NC 15 VIN 14 VIN 13 NC
24-Pin Wide SOIC (WM)
NC 1 NC 2 OUT 3 NC 4 GND 5 NC 6 FB 7 NC 8
16 VIN 15 NC 14 GND 13 GND 12 GND 11 GND 10 NC 9 ON/OFF
NC NC FB SIG GND NC
ON/OFF 10 NC 11 PWR GND 12
16-Pin Plastic DIP (N)
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LM2575
Absolute Maximum Ratings(1)
Maximum Supply Voltage (VIN) ......................................45V ON/OFF Pin Input Voltage. ......................-0.3V V +40V Output Voltage to Ground (Steady State) ......................-1V Power Dissipation .....................................Internally Limited Maximum Junction Temperature................................ 150C Lead Temperature (soldering, 10 sec.)...................... 260C Storage Temperature (Ts) .........................-65C to +150C Minimum ESD Rating C = 100pF, R = 1.5k.............................................. 2kV FB Pin ...................................................................... 1kV
Operating Ratings
Supply Voltage (VIN).......................................................40V Junction Temperature Range (TJ).......-40C TJ +125C
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 Limit (Note 2) Units (Limits)
Symbol Parameter Condition SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1
Typ
Feedback Voltage VOUT
VIN = 12V , ILOAD = 0.2A VOUT = 5V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 5V
1.230 1.217 1.243 1.230 1.193/1.180 1.267/1.280 82 3.3 3.234 3.366 3.3 3.168/3.135 3.432/3.465 75 5.0 4.900 5.100 5.0 4.800/4.750 5.200/5.250 82 12 11.760 12.240 12 11.520/11.400 12.480/12.600 88
Feedback Voltage LM2575
Efficiency VIN = 12V, ILOAD = 1A, VOUT = 5V SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage VOUT VIN = 12V , ILOAD = 0.2A VOUT = 3.3V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 3.3V
V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) %
Output Voltage LM2575-3.3
Efficiency VIN = 12V, ILOAD = 1A SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage VOUT VIN = 12V , ILOAD = 0.2A VOUT = 5V 0.2A ILOAD 1A, 8V VIN 40V VOUT = 5V
Output Voltage LM2575-5.0
Efficiency VIN = 12V, ILOAD = 1A SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage VOUT VIN = 25V , ILOAD = 0.2A VOUT = 12V 0.2A ILOAD 1A, 15V VIN 40V VOUT = 12V VIN = 25V, ILOAD = 1A
Output Voltage LM2575-12
Efficiency
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LM2575 Limit (Note 2)
LM2575
Symbol Parameter Condition DEVICE PARAMETERS, ADJUSTABLE REGULATOR
Typ
Units (Limits)
IB Feedback Bias Current VOUT = 5V DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fO Oscillator Frequency
50 52
100/500
nA kHz kHz(min) kHz(max) V V(max) % %(max) A A(min) A(max) mA(max) mA mA(max) mA mA(max) A A(max) C/W
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 2.2 1.7/1.3 3.0/3.2 2 75 30 5 10 Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50 200 65 45 2 85 100 1.4 1.2 4 30 ON /OFF Pin = 0V (ON) 0.01 10 2.2/2.4 1.0/0.8
VSAT DC ICL
IL
Output Leakage Current
VIN = 40V, (Note 6), (Note 6) (Note 6)
Output = 0V Output = -1V Output = -1V
IQ ISTBY
Quiescent Current
T Package, Junction to Ambient (Note 7) JA Thermal Resistance T Package, Junction to Ambient (Note 8) JA JC T Package, Junction to Case N Package, Junction to Ambient (Note 9) JA WM Package, Junction to Ambient (Note 9) JA ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 VIH VIL IIH IIL
Notes:
ON/OFF Pin Logic Input Level ON/OFF Pin Logic Current
VOUT = 0V VOUT = 5V ON /OFF Pin = 5V (OFF)
V(min) V(max) A A(max) A A(max)
1. 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. 2. All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are100% production tested. All limits at temperature extreme are guaranteed via testing. 3. 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. 4. Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output. 5. Feedback (pin 4) removed from output and connected to 0V. 6. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. 7. Junction to ambient thermal resistance (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/2" leads in a socket, or on PC board with minimum copper area. 8. Junction to ambient thermal resistance (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/4" leads soldered to PC board containing approximately 4 square inches of copper area surrounding the leads. 9. Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower thermal resistance further.
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LM2575
Test Circuits and Layout Guidelines
FEEDBACK +VIN 1 7V - 40V U N R E G U L A TE D + DC INPUT 100F C IN G ND 4 OU TPU T 5 2 L1 330H 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.)
LM2575
3 ON/OFF
FEEDBACK +VIN 1 7V - 40V U N R E G U L A TE D + DC INPUT 100F C IN
LM2575-5.0
3 ON/OFF 5
4 OU TPU T 2 L1 330H 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.)
G ND
Not e: 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 transient switch 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.
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LM2575
Typical Characteristics (circuit of Figure 1)
Supply Current
SUP PLY CURRE NT (mA ) S TA N D B Y Q U I E S C E N T C U R R E N T ( A )
Supply Current vs. Duty Cycle
20.0
S U P P LY C U R R E N T ( m A )
Standby Quiescent Current
200 VIN = 40V
20 18 16 14 12 10 8 6 4 0 10 20 30
Measured at Ground Pin TJ VOUT = 5V
17.5 15.0 12.5 10.0 7.5 5.0 2.0 VIN from 7V to 40V 0 20 40 60 80 100 I L O AD= 200 mA
150 VON/OFF= 5V VIN= 12V 50
100
I LO AD to 1A
40
50
60
0
0 -75 -50 -25 0 25 50 75 100 125150
INPUT VOLTAGE ( V)
D U TY C YC L E ( % )
Current Limit
O U TPU T C U R R EN T ( A)
Switch Saturation Voltage
SATU R ATI O N VO LTAG E ( V)
Efficiency
100 95 VOUT = 12V
EFFI CI ENCY ( % )
3 VIN = 25V
1.2
1.0 -55 C -40 C 0.8 25 C
90 85 80 75 70 65 1A VOUT = 3V 200 mA
1A
2
200 mA
1
0.6 125 C 150 C 0.4
0 -75 -50 -25 0 25 50 75 100125 150
0
0.2
0.4
0.6
0.8
1.0
60
0
5
10 15 20 25 30 35 40
INPUT VOLTAGE ( V)
SW I TC H C U R R EN T ( A)
N O R M ALI ZED FEED BAC K VO LTAG E ( m V)
5.0 4.5
INPUT VOLTAGE ( V)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 VO U T = 1.23V IL OAD= 200 mA 25 50 75 100125150
14 V 12 Normalized to IN = 10V VOUT = 5V 10 I = 500mA 8 LO AD TJ = 25 6 4 2 0 -2 -4 -6 0 5 10 15 20 25 30
S TA N D B Y Q U I E S C E N T C U R R E N T ( A )
Minimum Operating Voltage
Line Regulation
Feedback Pin Current
100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125150
INPUT VOL TAGE ( V)
INPUT- OUTPUT DIFFERENTIAL ( V)
O UTPUT VO LTAG E CHANG E ( m V)
Normalized Output Voltage
NO RM ALI ZED FREQ UENCY ( % )
Oscillator Frequency
+8 +6 +4 +2 0 -2 -4 --6 VIN = 40V Normalized at 25 C 2.0
Dropout Voltage
I LO AD= 1A VOUT = 5% RIND = 0. 2
100 75 50 25 0 -25 -50 -75
VIN = 12V I LO AD = 200mA Normalized to J = 25 C T
1.5
1.0 I LO AD = 200 mA
0.5
-100 -75 -50 -25 0
25 50 75 100125150
VIN = 12V -8 -75 -50 -25 0 25 50 75 100125150
0 -75 -50 -25 0 25 50 75 100125150
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LM2575
Typical Characteristics (continued)
N O R M ALI ZED FEED BAC K VO LTAG E ( m V) FE E D B A C K V O LTA G E C H A N G E ( m V )
Normalized Feedback Voltage*
25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 VIN = 12V IL O AD= 200mA Normalized to J = 25 C T
20 15 10 5 0 -5 -10 -15 -20 0
Feedback Voltage vs Duty Cycle*
I LO AD = 200 mA
VIN = 40V
VIN = 7V
25 50 75 100125150
20
40
60
80
100
D U TY C YC LE ( % )
* Adjustable version only
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LM2575
Functional Characteristics (circuit of Figure 1)
Load Transient Response
Switching Waveforms
Output Voltage Change
+100mV 0 -100mV
A
10V 0
B
1A 0
C
1A .5A
1.0A Output Current 0.5A 0 V OUT = 5V 100s/div.
D
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 Horizontal Time Base: 5s/div
Functional Diagrams
V IN
1 4
3.1k FIXED GAIN ERROR AMP
INTERNAL REGULATOR
ON/OFF
5
ON/OFF
FB
+
1.0k
COMPARATOR
1 AMP SWITCH DRIVER
-
+ -
2
THERMAL SHUTDOWN CURRENT LIMIT
OUT
1.23V BAND-GAP REFERENCE
52 kHz OSCILLATOR
RESET
3
GND
Note: Pin numbers are for the TO-220 package
Fixed Regulator
VIN
1
FIXED GAIN ERROR AMP
INTERNAL REGULATOR
ON/OFF
5
ON/OFF
FB
4
+ + -
COMPARATOR
1 AMP SWITCH DRIVER
2
THERMAL SHUTDOWN CURRENT LIMIT
OUT
1.23V BAND-GAP REFERENCE
52 kHz OSCILLATOR
RESET
3
GND
Adjustable Regulator
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LM2575
Package Information
0.780 MAX (19.812) PIN 1 .2500.005 (6.3500.127) 0.030-0.110 RAD (0.762-2.794)
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) 0.1000.010 (2.5400.254) 0.125 MIN (3.175) 0.009-0.015 (0.229-0.381) 0.0180.003 (0.4570.076) +0.025 -0.015 +0.635 8.255 -0.381 0.325
(
)
16-Pin Plastic DIP (N)
24-Pin Wide SOIC (WM)
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LM2575
5-Pin TO-220 (T)
5-Pin TO-263 (T)
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LM2575
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
The 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) 2000 Micrel, Incorporated.
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