MIC4575. Features. General Description. Applications. Typical Application. 200kHz Simple 1A Buck Regulator

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1 00kHz Simple 1A Buck Regulator General Description The is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 00kHz duplicates the pinout and function of the 5kHz LM575. The higher switching frequency may allow up to a :1 reduction in output filter inductor size. The is available in., and 5 fixed output versions or a 1. to 0 adjustable output version. Both versions are capable of driving a 1A load with excellent line and load regulation. The feedback voltage is guaranteed to ±% tolerance for adjustable versions, and the output voltage is guaranteed to ±% for fixed versions, within specified voltages and load conditions. The oscillator frequency is guaranteed to ±10%. In shutdown mode, the regulator draws less than 00µA standby current. The regulator performs cycle-by-cycle current limiting and thermal shutdown for protection under fault conditions. This series of simple switch-mode regulators requires a minimum number of external components and can operate using a standard series of inductors. Frequency compensation is provided internally. The is available in TO-0 (T) and TO-6 (U) packages for the industrial temperature range. Data sheets and support documentation can be found on Micrel s web site at Features Fixed 00kHz operation., 5, and adjustable output versions oltage over specified line and load conditions: Fixed version: ±% max. output voltage Adjustable version: ±% max. feedback voltage Guaranteed 1A switch current Wide to input voltage range Wide 1. to 0 output voltage range Requires minimum external components < 00µA typical shutdown mode 75% efficiency (adjustable version > 75% typical) Standard inductors and capacitors are5% of typical LM575 values Thermal shutdown Overcurrent 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) Battery charger Negative boost converter Step-down 6 to. for Intel Pentium and similar microprocessors Typical Application Shutdown Enable 8 to C1 150µF SHDN SW -5.0_T FB GND L1 68µH D1 1N /1A C 0µF 16 Fixed Regulator Adjustable Regulator Pentium is a registered trademark of Intel Corporation Micrel Inc. 180 Fortune Drive San Jose, CA 9511 USA tel +1 (08) fax + 1 (08) July M

2 Ordering Information Part Number Standard RoHS Compliant* oltage Temperature Range Package -.BT -.WT. 0 to +85 C 5-Pin TO-0-5.0BT -5.0WT to +85 C 5-Pin TO-0 BT WT Adj. 0 to +85 C 5-Pin TO-0 -.BU -.WU. 0 to +85 C 5-Pin TO-6-5.0BU -5.0WU to +85 C 5-Pin TO-6 BU WU Adj. 0 to +85 C 5-Pin TO-6 * RoHS compliant with high-melting solder exemption. Pin Configuration TAB 5 SHDN FB GND SW 1 IN 5-Pin TO-0 (T) 5-Pin TO-6 (U) Pin Description Pin Number Pin Name Pin Function 1 IN Supply oltage (Input): Unregulated + to +0 supply voltage. SW Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode., TAB GND Ground. FB Feedback (Input): Output voltage feedback to regulator. Connect to output of supply for fixed versions. Connect to 1. tap of resistive divider for adjustable versions. 5 SHDN Shutdown (Input): Logic low enables regulator. Logic high (>.) shuts down regulator. July 009 M

3 Absolute Maximum Ratings Supply oltage ( ) (1)...+0 Shutdown oltage ( SHDN ) to +6 Output Switch ( SW )... 1 Storage Temperature (T s ) C to 150 C ESD () Operating Ratings Supply oltage ( )...+ Junction Temperature (T J ) C Package Thermal Resistance TO-0, TO-6 (θ JA )...65 C/W TO-0, TO-6 (θ JC )... C/W Electrical Characteristics () = 1; I LOAD = 00mA; T J = 5 C, bold values indicate 0 C< T J < +85 C, unless noted. Parameter Condition Min Typ Max Units [Adjustable] Feedback oltage Feedback oltage 8, 0.A I LOAD 1A Efficiency I LOAD = 1A, OUT = 5 77 % Feedback Bias Current Output oltage...66 Output oltage 6, 0.A I LOAD 1A Efficiency I LOAD = 1A 7 % -5.0 Output oltage Output oltage 8, 0.A I LOAD 1A Efficiency I LOAD = 1A 77 % / -. / -5.0 Oscillator Frequency khz Saturation oltage I OUT = 1A Maximum Duty Cycle (On) FB connected to % Current Limit Peak Current, t ON µs Output Leakage Current =, FB connected to 0 Output = 0 Output = Quiescent Current 5 10 ma Standby Quiescent Current SHDN = 5 (regulator off) µa SHDN Input Logic Level OUT = 0 (regulator off).. SHDN Input Current na na A A ma ma 1. OUT =. or 5 (regulator on) SHDN = 5 (regulator off) SHDN = 0 (regulator on) 10 Notes: 1. The is not guaranteed to survive a short circuit to ground for input voltage above.. Devices are ESD sensitive. Handling precautions recommended µa µa July 009 M

4 Functional Diagram Block Diagram with External Components Fixed Step-Down Regulator Block Diagram with External Components Adjustable Step-Down Regulator July 009 M

5 Functional Description The is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the block diagrams. Supply oltage The operates from a + to + unregulated input. Highest efficiency operation is from a supply voltage around +15. Enable/Shutdown The shutdown (SHDN) input is TTL compatible. Ground the input if unused. A logic-low enables the regulator. A logic-high shuts down the internal regulator which reduces the current to typically 50µA. Feedback Fixed versions of the regulator have an internal resistive divider from the feedback (FB) pin. Connect FB directly to the output line. Adjustable versions require an external resistive voltage divider from the output voltage to ground, connected from the1. tap to FB. Duty Cycle Control A fixed-gain error amplifier compares the feedback signal with a 1. bandgap voltage reference. The resulting error amplifier output voltage is compared to a 00kHz sawtooth waveform to produce a voltage controlled variable duty cycle output. A higher feedback voltage increases the error amplifier output voltage. A higher error amplifier voltage (comparator inverting input) causes the comparator to detect only the peaks of the sawtooth, reducing the duty cycle of the comparator output. A lower feedback voltage increases the duty cycle. Output Switching When the internal switch is on, an increasing current flows from the supply, through external storage inductor L1, to output capacitor C OUT and the load. Energy is stored in the inductor as the current increases with time. When the internal switch is turned off, the collapse of the magnetic field in L1 forces current to flow through fast recovery diode D1, charging C OUT. Output Capacitor External output capacitor C OUT provides stabilization and reduces ripple. Return Paths During the on portion of the cycle, the output capacitor and load currents return to the supply ground. During the off portion of the cycle, current is being supplied to the output capacitor and load by storage inductor L1, which means that D1 is part of the high-current return path. July M

6 Application Information The applications circuits that follow have been constructed and tested. Refer to Application Note 15 for additional information, including efficiency graphs and manufacturer s addresses and telephone numbers for most circuits. For a mathematical approach to component selection and circuit design, refer to Application Note 1. Figure. 6 to./1a Buck Converter Low-Profile Surface Mount Figure 1. 6 to./1a Buck Converter Through Hole Figure 5. 8 to 5/1A Buck Converter Low-Profile Surface Mount 16 to C1 68µF 6 Figure. 8 to 5/1A Buck Converter Through Hole 5 SHDN SW BT FB GND 1 L1 150µH MBR160 R 1.0k R1 1.50k 1/1A C 0µF 16 Figure to 1/1A Buck Converter Low-Profile Surface Mount C1 Nichicon C Nichicon D1 Motorola MBR160 L1 Sumida Figure. 16 to 1/1A Buck Converter Through Hole Note : Surface-mount component. Figure 7. 6 to./1a Buck Converter Lower-Cost Surface Mount July M

7 Figure 8. 8 to 5/1A Buck Converter Lower-Cost Surface Mount Figure to 5/0.A Buck-Boost Converter Through Hole Figure to 1/1A Buck Converter Lower-Cost Surface Mount Figure to 5/0.A Buck-Boost Converter Through Hole 8 to 18 C1 µf SHDN SW BU FB GND T1 68µH L1 1µH 1 D1 MBRS10LT C 0µF 10 R.01k R1 1.00K C 00pF OUT 5/1A 5m P-P C 0µF 10 C1 AX C AX C AX D1 Motorola MBRS10LT T1 Coiltronics L1 Coilcraft DO1608C-10 Figure 1. Low Output-Noise Regulator (5m Output Ripple ) July M

8 8 to 18 C1 µf SHDN SW BU FB GND D1 MBRS10LT T1 68µH 1 R.01k R1 1.00K C 00pF + OUT /+I OUT 5/0.5A C 0µF 10 C5 0µF 10 L1 D MBRS10LT C 0µF 10 C1 AX C AX C AX C5 AX D1 Motorola MBRS10LT D Motorola MBRS10LT T1 Coiltronics +I + I A DC % then I 0% then I (1 DC) - OUT /-I OUT -5/0.5A at 15 Load Regulation 5% Figure 1. Split ±5 Supply Figure 1. Adjustable (0 1) Output-oltage Regulator 5 SHDN U1 SW L1 68µH OUT 1/1A to 15 C1 150µF 5 1 BT FB GND D1 1N R1 9 U LM58 R 1.00k C 0µF 16 R 1k C1 C D1 L1 U Motorola 1N5819 National LM58 Figure 15. Low Output-oltage Regulator (1) July M

9 Figure 16. 1A Battery Charger (6 8 cells) D 8 to C1 150µF SHDN SW -BT FB GND U1 Micrel BT U National LM58 U Micrel LM01CIZ-1. C1 Nichicon C Nichicon D1 Motorola 1N5819 D Motorola 1N5819 D Motorola 1N18 L1 Coiltronics R1 KRL SP-1-A1-0R100J Q1 Siliconix NLL / R7 1k R6 k C 1000pF 1N18 1 D1 1N5819 C 0.01µF L1 68µH DZ1 1N5 1 UA 1/LM58 R1 0.1 C R 0µF R 1.1k R 10k 7 Q1 NLL 8 5 UB 1/ LM58 6 D 1N5819 R5 10k R1 10k I OUT 0.1A to 1A -8 Cells BATT U LM01CIZ-1. Figure A 1A ariable-current Battery Charger July M

10 Figure 18. 1A Battery Charger ( 8 Cells) Figure 19. Remote-Sensing Regulator July M

11 Figure to Split ±1/100mA Supply Figure 1. 1A Battery Charger July M

12 Figure. Improved Adjustable Output-oltage Regulator (0 1) Figure. Switchable Battery-Pack Charger July M

13 Figure. Lithium-Ion Battery Charger with End-of-Charge Flag Figure 5. Low Output-Noise Regulator (<1m) July M

14 Package Information 5-Pin TO-0 (T) 5-Pin TO-6 (U) July M

15 MICREL, INC. 180 FORTUNE DRIE SAN JOSE, CA 9511 USA TEL +1 (08) FAX +1 (08) WEB 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 Micrel, Incorporated. July M

16 Mouser Electronics Authorized Distributor Click to iew Pricing, Inventory, Delivery & Lifecycle Information: Microchip: -5.0WU WT -.WU WU -5.0WT -.WT -.WU- TR -5.0WU-TR WU-TR