Features. 7V 40V Unregulated DC Input 1 +V IN + C IN

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1 LM76 khz Simple A Buck Regulator General Description The LM76 series of monolithic integrated circuits provide all the active functions for a step-down (buck) switching regulator. Fixed versions are available with a.v, V, or V fixed output. Adjustable versions have an output voltage range from.v to 7V. Both versions are capable of driving a A 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 LM76 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 LM76 series. This feature greatly simplifies the design of switch-mode power supplies. The feedback voltage is guaranteed to ±% tolerance for adjustable versions, and the output voltage is guaranteed to ±% for fixed versions, within specified input voltages and output load conditions. The oscillator frequency is guaranteed to ±%. External shutdown is included, featuring less than µa standby current. The output switch includes cycle-bycycle current limiting and thermal shutdown for full protection under fault conditions. Features.V, V, V, and adjustable output versions Voltage over specified line and load conditions: Fixed version: ±% max. output voltage Adjustable version: ±% max. feedback voltage Guaranteed A output current Wide input voltage range: V to V Wide output voltage range.v to 7V Requires only external components khz fixed frequency internal oscillator Low power standby mode I Q typically < µa 8% efficiency (adjustable version typically > 8%) Uses readily available standard inductors Thermal shutdown and current limit protection % 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 V Unregulated DC Input C IN µf Gnd LM7-. On/Off Feedback Output L µh D N8 V, A Regulated Output C OUT µf 7V V Unregulated DC Input C IN µf Gnd LM7 On/Off Feedback Output L µh D N8 C OUT µf V, A Regulated Output R.9k R k Note: Pin numbers are for TO- Package Note: Pin numbers are for TO- Package ( ) V R OUT =. R Fixed Regulator in Typical Application Adjustable Regulator in Fixed Output Application 8 Fortune Drive San Jose, CA 9 USA tel (8) 9-8 fax (8) 7- August M B

2 Ordering Information Part Number Temperature Standard RoHS Compliant** Range Package LM76BT* LM76WT* C to 8 C TO-- LM76-.BT LM76-.WT C to 8 C TO-- LM76-.BT LM76-.WT C to 8 C TO-- LM76-BT LM76-WT C to 8 C TO-- LM76BU* LM76WU* C to 8 C TO-6- LM76-.BU LM76-.WU C to 8 C TO-6- LM76-.BU LM76-.WU C to 8 C TO-6- LM76-BU LM76-WU C to 8 C TO-6- * Adjustable output regulators. **RoHS compliant with "hot-melting solder" exemption. Contact factory for bent or staggered leads option. Pin Configurations GND -LEAD TO- (T) - ON/OFF - FEEDBACK - GROUND - OUTPUT - VIN GND -LEAD TO-6 (U) - ON/OFF - FEEDBACK - GROUND - OUTPUT - VIN M B August

3 Absolute Maximum Ratings (Note ) Maximum Supply Voltage V ON/OFF Pin Input Voltage.V V V Output Voltage to Ground (Steady State) V Power Dissipation Internally Limited Storage Temperature Range 6 C to C Minimum ESD Rating C = pf, R =.kω kv FB Pin kv Lead Temperature (soldering, sec.) 6 C Maximum Junction Temperature C Operating Ratings Temperature Range Supply Voltage C T J C V Electrical Characteristics Specifications with standard typeface are for T J = C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, = V, and I LOAD = ma. LM76 Symbol Parameter Conditions Typ Limit Units (Note ) (Limits) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note ) Test Circuit Figure Feedback Voltage = V, I LOAD =.A. V = V.7 V(min). V(max) Feedback Voltage.A I LOAD A, 8V V. V LM76 = V.9/.8 V(min).67/.8 V(max) η Efficiency = V, I LOAD = A, = V 8 % SYSTEM PARAMETERS,.V REGULATORS (Note ) Test Circuit Figure Output Voltage = V, I LOAD =.A. V =.V. V(min).66 V(max) Output Voltage.A I LOAD A, 6V V. V LM76-. =.V.68/. V(min)./.6 V(max) η Efficiency = V, I LOAD = A 7 % SYSTEM PARAMETERS, V REGULATORS (Note ) Test Circuit Figure Output Voltage = V, I LOAD =.A. V = V.9 V(min). V(max) Output Voltage.A I LOAD A, 8V V. V LM76-. = V.8/.7 V(min)./. V(max) η Efficiency = V, I LOAD = A 8 % SYSTEM PARAMETERS, V REGULATORS (Note ) Test Circuit Figure Output Voltage = V, I LOAD =.A V = V.76 V(min). V(max) Output Voltage.A I LOAD A, V V V LMLM76- = V./. V(min).8/.6 V(max) η Efficiency = V, I LOAD = A 88 % August M B

4 Electrical Characteristics (continued) LM76 Units Symbol Parameter Conditions Typ Limit (Limits) (Note ) DEVICE PARAMETERS, ADJUSTABLE REGULATOR I B Feedback Bias Current = V / na DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS f O Oscillator Frequency khz 7/ khz (min) 8/6 khz (max) V SAT Saturation Voltage I OUT = A (Note ). V.8/. V(max) DC Max Duty Cycle (ON) (Note ) 98 % 9 %(min) I CL Current Limit Peak Current, t ON µs (Note ).8 A./. A(min) 6.9/7. A(max) I L Output Leakage Current = V, (Note 6), Output = V ma(max) Output = V 7. ma (Note 6) Output = V ma(max) I Q Quiescent Current (Note 6) ma ma(max) I STBY Standby Quiescent ON/OFF Pin = V (OFF) µa Current µa(max) θ JA Thermal Resistance T,U Package, Junction to Ambient (Note 7) 6 C/W θ JA T,U Package, Junction to Ambient (Note 8) θ JC T,U Package, Junction to Case M B August

5 Electrical Characteristics (continued) LM76 Units Symbol Parameter Conditions Typ Limit (Limits) (Note ) ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure V IH ON/OFF Pin Logic = V../. V(min) V IL Input Level = V../.8 V(max) I IH ON /OFF Pin Logic ON /OFF Pin = V (OFF) µa Current µa(max) I IL ON/OFF Pin = V (ON). µa µa(max) Note : 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. Note : All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are % production tested. All limits at temperature extreme are guaranteed via testing. Note : External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM76/LM76 is used as shown in Figure test circuit, system performance will be shown in system parameters section of Electrical Characteristics. Note : Output (pin ) sourcing current. No diode, inductor or capacitor connected to output. Note : Feedback (pin ) removed from output and connected to V. Note 6: Feedback (pin ) removed from output and connected to V to force the output transistor OFF. Note 7: Junction to ambient thermal resistance (no external heat sink) for the -lead TO- package mounted vertically, with /" leads in a socket, or on PC board with minimum copper area. Note 8: Junction to ambient thermal resistance (no external heat sink) for the -lead TO- package mounted vertically, with /" leads soldered to PC board containing approximately square inches of copper area surrounding the leads. Note 9: Junction to ambient thermal resistance with approximately square inch of pc board copper surrounding the leads. Additional copper will lower thermal resistance further. Typical Performance Characteristics NORMALIZED FEEDBACK VOLTAGE (mv) Normalized Feedback Voltage* = V I LOAD = ma Normalized to T J = C FEEDBACK VOLTAGE CHANGE (mv) Feedback Voltage vs Duty Cycle* ILOAD = ma VIN = 7V VIN = V DUTY CYCLE (%) * Adjustable version only August M B

6 Typical Performance Characteristics (continued) (Circuit of Figure ) Supply Current Supply Current vs. Duty Cycle Standby Quiescent Current SUPPLY CURRENT (ma) Measured at 8 Ground Pin T J = C 6 = V 8 I LOAD to A 6 6 SUPPLY CURRENT (ma) I LOAD = ma.. from 7V to V 6 8 STANDBY QUIESCENT CURRENT (µa) -7 = V V ON/OFF = V = V INPUT VOLTAGE (V) DUTY CYCLE (%) OUTPUT CURRENT (A) Current Limit VI N = V SATURATION VOLTAGE (V). Switch Saturation Voltage. - C - C.8 C.6 C C EFFICIENCY (%) Efficiency = V A ma ma A = V SWITCH CURRENT (A) INPUT VOLTAGE (V) Minimum Operating Voltage Line Regulation Feedback Pin Current INPUT VOLTAGE (V) =.V. I LOAD = ma NORMALIZED FEEDBACK VOLTAGE (mv) Normalized to = V V OUT = V I 8 LOAD = ma T J = INPUT VOLTAGE (V) STANDBY QUIESCENT CURRENT (µa) OUTPUT VOLTAGE CHANGE (mv) Normalized Output Voltage VIN = V ILOAD = ma Normalized to TJ = C NORMALIZED FREQUENCY (%) Oscillator Frequency 8 Normalized at C 6 - = V = V INPUT-OUTPUT DIFFERENTIAL (V).... Dropout Voltage ILOAD = A I LOAD = ma VOUT = % RIND =.Ω M B 6 August

7 Typical Performance Characteristics (Circuit of Figure ) Load Transient Response mv Output Voltage Change -mv A Output Current A A µs/div. A B C D V A A A A Switching Waveforms µs/div. = V = V A: Output pin voltage V/div B: Output pin current A/div C: Inductor current A/div D: Output ripple voltage mv/div., AC coupled Horizontal Time Base: µs/div August 7 M B

8 Test Circuits and Layout Guidelines FEEDBACK 7V - V UNREGULATED DC INPUT µf C IN LM7 GND ON/OFF OUTPUT L µh D MBR6 C OUT 7µF R R.V L O A D C IN µf, 7V Aluminum Electrolytic C OUT 7µF, V Aluminum Electrolytic D Schottky, MBR6 L µh, -96 (AIE) R k,.% R.6k,.% -pin TO- socket 96 (Loranger Mfg. Co.) -pin TO- socket 8-AG7 (Augat Inc.) FEEDBACK 7V - V UNREGULATED DC INPUT µf C IN LM7-. GND ON/OFF OUTPUT L µh D DQ6 C OUT µf.v L O A D C IN µf, 7V Aluminum Electrolytic C OUT µf, V Aluminum Electrolytic D Schottky, DQ6 L µh, -96 (AIE) -pin TO- socket 96 (Loranger Mfg. Co.) -pin TO- socket 8-AG7 (Augat Inc.) Note: Pin numbers are for TO- Package Figure. 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 INTERNAL REGULATOR ON/OFF ON/OFF INTERNAL REGULATOR ON/OFF ON/OFF FEED- BACK.k.k - FIXED GAIN ERROR AMP - COMPARATOR DRIVER AMP SWITCH OUTPUT FEED- BACK - FIXED GAIN ERROR AMP - COMPARATOR DRIVER AMP SWITCH OUTPUT.V BAND-GAP REFERENCE khz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT GND.V BAND-GAP REFERENCE khz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT GND Note: Pin numbers are for the TO- package Fixed Regulator Adjustable Regulator M B 8 August

9 Package Information.8 ±. (.7 ±.). D ±. (.8 D ±.). ±. (.6 ±.8). ±.7 (6. ±.).77 ±.8 (. ±.). ±. (.7 ±.).78 ±.8 (.68 ±.6) SEATING PLANE. ±. (.97 ±.) 7 Typ..67 ±. (.7 ±.7).68 REF (6.8 REF). ±. (.8 ±.).8 ±.8 (.6 ±.). ±. (.6±.) Dimensions: inch (mm) -Lead TO- (T).6 ±. ±.±..±..76 ±..6 ±..6±..6±. SEATING.. PLANE.8.67±.. ±. DIM. = INCH 8 MAX. ±.. ±. -Lead TO-6 (U) MICREL INC. 8 FORTUNE DRIVE SAN JOSE, CA 9 USA TEL (8) 9-8 FAX (8) 7- WEB 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. Micrel, Incorporated. August 9 M B