Features MIC BN FB. Fixed Regulator

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1 MIC44 200kHz Simple 0.A Buck Regulator General Description The MIC44 is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 200kHz MIC44 duplicates the pinout and function of the 2kHz LM24. The higher switching frequency may allow up to a 2: reduction in output filter inductor size. The MIC44 is available in.v, and V fixed output versions or a.2v to 20V adjustable output version. Both versions are capable of driving a 0.A load with excellent line and load regulation. The feedback voltage is guaranteed to ±2% 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 ±0%. In shutdown mode, the regulator draws less than 200µA 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 MIC44 is available in the DIP (N) package and is rated over the industrial temperature range. Data sheets and support documentation can be found on Micrel s web site at Features Fixed 200kHz operation.v, V, and adjustable output versions Voltage over specified line and load conditions: Fixed version: ±% max. output voltage Adjustable version: ±2% max. feedback voltage Guaranteed 0.A switch current Wide 4V to 24V input voltage range Wide.2V to 20V output voltage range Requires minimum external components < 200µA typical shutdown mode % efficiency (adjustable version > % typ.) Standard inductors and capacitors are 2% of typical LM24 values Thermal shutdown Overcurrent protection 00% electrical thermal limit burn-in Applications Simple high-efficiency step-down (buck) regulator Efficient preregulator for linear regulators On-card switching regulators Positive-to-negative converter (inverting buck-boost) Isolated flyback converter using minimum external components Negative boost converter Typical Application Enable 8V to 24V C 4µF V MIC44-.0BN 2 4 L 00µH D N89.0V/0.A 6V Fixed Regulator 280 Fortune Drive San Jose, CA 9 USA tel + (408) fax + (408) June 200 M

2 Ordering Information Part Number Temperature Standard Pb-Free Voltage Range Package MIC44-.BN MIC44-.YN.V 40 C to +8 C 8-pin DIP MIC44-.0BN MIC44-.0YN.0V 40 C to +8 C 8-pin DIP MIC44BN MIC44YN Adjustable 40 C to +8 C 8-pin DIP Pin Configuration 8 NC SGND 2 SW SHDN 6 NC PGND 4 8-Pin DIP (N) Pin Description Pin Number Pin Name Pin Function Feedback (Input): Output voltage feedback to regulator. Connect to output of supply for fixed versions. Connect to.2v tap of resistive divider for adjustable versions. 2 SGND Signal Ground. SHDN (Input): Logic low enables regulator. Logic high (> 2.4V) shuts down regulator. 4 PGND Power Ground. VIN Supply Voltage (Input): Unregulated +4V to +24V supply voltage. SW Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. 6, 8 NC Not internally connected. Solder to printed circuit for maximum heat transfer. M June 200

3 Absolute Maximum Ratings (Note ) Supply Voltage ( ), Note...+40V (V SHDN )... 0.V to +6V Output Switch (V SW ) steady state... V Junction Temperature (T J ) C Storage Temperature... 6 C to +0 C ESD Rating, Note Electrical Characteristics (Note 4) =2V; I LOAD = 00mA; T A = 2 C, bold values indicate 40 C T A +8 C; unless noted Parameter Condition Min Typ Max Units MIC44 [Adjustable] Feedback Voltage V Feedback Voltage 8V 24V, 0.A I LOAD 0.A V V Efficiency I LOAD = 0.A, V OUT = V % Feedback Bias Current 0 00 na 00 na MIC44-. Output Voltage V Output Voltage 6V 24V, 0.A I LOAD 0.A V..46 V Efficiency 2 % MIC44-.0 Output Voltage V Output Voltage 8V 24V, 0.A I LOAD 0.A V V Efficiency % MIC44 / -. / -.0 Operating Ratings (Note 2) Oscillator Frequency khz Saturation Voltage I OUT = 0.A. V. V Maximum Duty Cycle (On) connected to 0V 90 9 % Current Limit Peak Current, t ON µs A A Output Leakage Current = 24V, connected to 6V Output = 0V 0 2 ma Output = V. ma Quiescent Current 0 ma Standby Quiescent Current SHDN = V (regulator off) µa SHDN Input Logic Level V OUT = 0V (regulator off) V 2.4 V V OUT =.V or V (regulator on).2.0 V 0.8 V SHDN Input Current SHDN = V (regulator off) 4 0 µa SHDN = 0V (regulator on) µa Note. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note. Devices are ESD sensitive. Handling precautions recommended. Note 4. Specification for packaged product only. Note. The MIC44 is not guaranteed to survive a short circuit to ground for input voltage above 24V. Supply Voltage ( ) V Package Thermal Resistance θ JA Plastic DIP... 0 C/W June 200 M

4 Block Diagrams +24V max. C IN Enable SHDN Internal Regulator 200kHz Oscillator Thermal Current Limit Comparator Driver 0.A Switch SW D L V OUT Error Amp..2V Bandgap R C OUT MIC44-x.x R2 GND Block Diagram with External Components Fixed Step-Down Regulator +24V max. C IN Enable SHDN Internal Regulator 200kHz Oscillator Thermal Current Limit V OUT V REF R R2 + R R2 V OUT V REF Comparator Driver 0.A Switch SW D L V OUT Error Amp..2V Bandgap R C OUT MIC44 [Adjustable] GND R2 Block Diagram with External Components Adjustable Step-Down Regulator M June 200

5 Functional Description The MIC44 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the block diagrams. Supply Voltage The MIC44 operates from a +4V to +24V unregulated input. Highest efficiency operation is from a supply voltage below +V. Enable/ 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 0µA. Feedback Fixed versions of the regulator have an internal resistive divider from the feedback () pin. Connect directly to the output line. Adjustable versions require an external resistive voltage divider from the output voltage to ground, connected from the.2v tap to. Duty Cycle Control A fixed-gain error amplifier compares the feedback signal with a.2v bandgap voltage reference. The resulting error amplifier output voltage is compared to a 200kHz 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 L, 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 L forces current to flow through fast recovery diode D, 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 L, which means that D is part of the high-current return path. June 200 M

6 Applications Information The applications circuits that follow have been constructed and tested. Refer to Application Note 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 4. 6V to 24V C 4µF V MIC44-.BN 2 4 L 00µH D N89.V/0.A 6V 8V to 24V C 4µF V MIC44-.0BN 2 4 L 00µH D N89.0V/0.A 6V C Nichicon UPLV40MEH, ESR = 0.4Ω Nichicon UPL2MPH, ESR = 0.6Ω D Motorola N89 L Sumida RCH8-0K, DCR = 0.28Ω Figure. 6V 24V to.v/0.a Buck Converter Through Hole C Nichicon UPLJ40MEH, ESR = 0.4Ω Nichicon UPL2MPH, ESR = 0.6Ω D Motorola N89 L Sumida RCH8-0K, DCR = 0.28Ω Figure 2. 8V 24V to V/0.A Buck Converter Through Hole 6V to 24V C µf 6V MIC44BN 2 4 L 220µH MBR60 R2.0k % R.0k % 2V/0.A 6V C Nichicon UPLJ0MEH, ESR = 0.Ω Nichicon UPL2MPH, ESR = 0.6Ω D Motorola MBR60 L Sumida RCH06-22K, DCR = 0.8Ω Figure. 6V 24V to 2V/0.A Buck Converter Through Hole M June 200

7 Package Information PIN DIMENSIONS: INCH (MM) 0.80 (9.6) 0.0 (9.40) 0. (.4) 0.2 (.8) 0.2 (6.48) 0.24 (6.22) 0.00 (.62) 0.0 (0.0) 0.00 (0.24) 0.08 (0.) 0.00 (2.4) 0.0 (.0) 0.0 (0.92) 8-Pin DIP (N) 0.80 (9.6) 0.20 (8.) MICREL INC. 280 FORTUNE DRIVE SAN JOSE, CA 9 USA TEL + (408) FAX + (408) 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. 200 Micrel, Incorporated. June 200 M