Features MIC WT FB GND. Fixed Regulator MIC4576WT FB GND. Adjustable Regulator

Transcription

1 MIC76 MIC76 00kHz Simple A Buck Regulator General Description The MIC76 is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 00kHz MIC76 duplicates the pinout and function of the khz LM76. The higher switching frequency may allow up to a : reduction in output filter inductor size. The MIC76 is available in.v, and V fixed output versions or a.v to V adjustable output version. Both versions are capable of driving a A 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 ±0%. 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 MIC76 is available in TO-0 (T) and TO-6 (U) packages for the industrial temperature range. Features Fixed 00kHz operation.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 switch current Wide V to 6V input voltage range Wide.V to V output voltage range Requires minimum external components < 00µA typical shutdown mode 7% efficiency (adjustable version > 7% typical) Standard inductors are % of typical LM76 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) Battery Charger Negative boost converter Step-down to.v for Intel Pentium and similar microprocessors Typical Applications Enable 8V to 6V C 6V MIC76-.0WT µh D MBR60 V/A C Fixed Regulator Enable to 6V C 6V MIC76WT 68µH MBR60 R.0k % R.0k % V/A C Adjustable Regulator 80 Fortune Drive San Jose, CA 9 USA tel + (08) fax + (08) March 006 MIC76

2 MIC76 Ordering Information Standard Part Number RoHS Compliant Part Number* Voltage Temperature Range Package MIC76-.BT MIC76-.WT.V 0ºC to +8ºC TO-0- MIC76-.0BT MIC76-.0WT.0V 0ºC to +8ºC TO-0- MIC76BT MIC76WT ADJ. 0ºC to +8ºC TO-0- MIC76-.BU MIC76-.WU.V 0ºC to +8ºC TO-6- MIC76-.0BU MIC76-.0WU.0V 0ºC to +8ºC TO-6- MIC76BU MIC76WU ADJ. 0ºC to +8ºC TO-6- * RoHS compliant with "high-melting solder" exemption. Pin Configuration TAB SHDN SW -Pin TO-0 (T) TAB SHDN SW -Pin TO-6 (U) Pin Description Pin Number Pin Name Pin Function Supply Voltage (Input): Unregulated +V to +6V supply voltage. SW Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode., TAB Ground Feedback (Input): Output voltage feedback to regulator. Connect to output of supply for fixed versions. Connect to.v tap of resistive divider for adjustable versions. SHDN (Input): Logic low enables regulator. Logic high (>.V) shuts down regulator. MIC76 March 006

3 MIC76 Absolute Maximum Ratings Supply Voltage ( )...+0V Voltage (V SHDN )... 0.V to +6V Output Switch (V SW ), Steady State... V Feedback Voltage (V ) [Adjustable]...+.8V Storage Temperature... 6 C to +0 C Operating Ratings Supply Voltage ( )...+6V Junction Temperature C Package Thermal Resistance TO-0, TO-6 (θ JA )... 6 C/W TO-0, TO-6 (θ JC )... C/W Electrical Characteristics = V; I LOAD = 00mA; T J = C, bold values indicate 0 C T J +8 C; unless noted. Parameter Condition Min Typ Max Units MIC76 [Adjustable] Feedback Voltage.7.0. V Feedback Voltage 8V 6V, 0.A I LOAD A V V Efficiency I LOAD = A, Note 77 % Maximum Duty Cycle (On) V =.0V 90 9 % Output Leakage Current = 6V, V =.V output = 0V 0 ma output = V 7. ma Quiescent Current V =.V 0 ma Feedback Bias Current 0 00 na 00 na MIC76-. Output Voltage...66 V Output Voltage 6V 6V, 0.A I LOAD A.68.. V..6 V Efficiency I LOAD = A 7 % Maximum Duty Cycle (On) V =.V 90 9 % Output Leakage Current = 6V, V =.0V output = 0V 0 ma output = V 7. ma Quiescent Current V =.0V 0 ma MIC76-.0 Output Voltage V Output Voltage 8V 6V, 0.A I LOAD A V.70.0 V Efficiency I LOAD = A 77 % Maximum Duty Cycle (On) V =.0V 90 9 % Output Leakage Current = 6V, V = 6.0V output = 0V 0 ma output = V 7. ma Quiescent Current V = 6.0V 0 ma March 006 MIC76

4 MIC76 Parameter Condition Min Typ Max Units MIC76 / -. / -.0 Oscillator Frequency khz Saturation Voltage I OUT = A.7. V. V Current Limit peak current, t ON µs; V = 0V A. 8. A Standby Quiescent Current V SHDN = V (regulator off), V = 0V 0 00 µa SHDN Input Logic Level V OUT = 0V (regulator off).. V. V V OUT =.V or V (regulator on)..0 V 0.8 V SHDN Input Current V SHDN = V (regulator off) 0 µa V SHDN = 0V (regulator on) µa General Note: Devices are ESD protected, however, handling precautions are recommended. Note : V OUT = V MIC76 March 006

5 MIC76 Block Diagrams +6V max. C IN Enable SHDN Internal Regulator 00kHz Oscillator Thermal Current Limit Comparator Driver A Switch SW D V OUT Error Amp..V Bandgap R C OUT MIC76-x.x R Block Diagram with External Components Fixed Step-Down Regulator +6V max. C IN Enable SHDN Internal Regulator 00kHz Oscillator Thermal Current Limit Comparator Driver A Switch SW D V OUT Error Amp..V Bandgap R C OUT MIC76 [Adjustable] R Block Diagram with External Components Adjustable Step-Down Regulator March 006 MIC76

6 MIC76 Functional Description The MIC76 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the block diagrams. Supply Voltage The MIC76 operates from a +V to +6V unregulated input. Highest efficiency operation is from a supply voltage around +V. Enable/ The shutdown (SHDN) input is TTL compatible. Ground the input if unused. A logic-low enables the regulator. A logichigh 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.v tap to. Duty Cycle Control A fixed-gain error amplifier compares the feedback signal with a.v 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. 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. 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, 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 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, which means that D is part of the high-current return path. For a mathematical approach to component selection and circuit design, refer to Application Note. 6V to V C V MIC76-.BT µh D N8.V/A C 6V to 6V C 6V MIC76-.BT µh D MBR60.V/A C C Nichicon UPV7MPH, ESR = 0.06Ω C Nichicon UPCMPH, ESR = 0.07Ω D Motorola N8 Coiltronics PLC--000, DCR = 0.06Ω Bi HM77-000, DCR = 0.0Ω, Note Figure. 6V V to.v/a Buck Converter C Nichicon UPJ7MRH, ESR = 0.09Ω C Nichicon UPC0MPH, ESR = 0.07Ω D Motorola MBR60 Coiltronics PLC--000 DCR = 0.06 Bi HM77-000, DCR = 0.0Ω, Note Figure. 6V 6V to.v/a Buck Converter Note : Surface-mount component. MIC76 6 March 006

7 MIC76 8V to V C V MIC76-.0BT µh D N8 V/A C 8V to 6V C 6V MIC76-.0BT µh D MBR60 V/A C C Nichicon UPJ7MPH, ESR = 0.06Ω C Nichicon UPC0MPH, ESR = 0.07Ω D Motorola MBR8 Coiltronics PLC--000, DCR = 0.06 Bi HM77-000, DCR = 0.0Ω, Note Figure. 8V V to V/A Buck Converter C Nichicon UPJ7MRH, ESR = 0.09Ω C Nichicon UPC0MPH, ESR = 0.07Ω D Motorola MBR60 Coiltronics PLSC--000, DCR = 0.06 Bi HM77-000, DCR = 0.0Ω, Note Figure. 8V 6V to V/A Buck Converter to 6V C 6V MIC76BT 68µH MBR60 R.0k % R.0k % V/A C C Nichicon UPJ7MPH, ESR = 0.09Ω C Nichicon UPC0MPH, ESR = 0.07Ω D Motorola MBR60 Bi HM , DCR = 0.08Ω Figure. 6V to V/A Buck Converter 8V to 6V U MIC76-.0BT µh D MBR60 R 0K R 0.Ω C V OUT V/A C 6V C 0.0µF U 8 U LM8 C 6V SHDN MIC76-.0BT SW L µh D MBR60 R 0.Ω C C, C Nichicon UPJ7MRH, ESR = 0.09Ω C, C Nichicon UPC0MPH, ESR = 0.07Ω D, D Motorola MBR60, L Coiltronics PLC--000, DCR = 0.06 R, R KRL SP--A-0R00J U National LM8 Figure 6. Parallel Switching Regulators Note : Surface-mount component. March MIC76

8 MIC76 Package Information 0.08 ±0.00 (.7 ±0.) 0.00 ±0.0 (0.6 ±0.8) 0.0 D ±0.00 (.8 D ±0.) 0. ±0.07 (6. ±0.) 0.77 ±0.008 (.0 ±0.0) 0.00 ±0.00 (.7 ±0.) 0.78 ±0.08 (.68 ±0.6) SEATING PLANE 0.0 ±0.00 (.97 ±0.) 7 Typ ±0.00 (.70 ±0.7) 0.68 REF (6.8 REF) 0.0 ±0.00 (0.8 ±0.) 0.08 ±0.008 (0.6 ±0.0) 0.0 ±0.0 (.6±0.) Dimensions: inch (mm) -Pin TO-0 (T) 0.06 ± ± 0.0 ± ± ± ± ± ±0.0 SEATING PLANE ± ±0.00 DIM. = INCH 8 MAX 0.00 ± ±0.00 -Pin TO-6 (U) MICREL INC. 80 FORTUNE DRIVE SAN JOSE, CA 9 USA TEL + (08) FAX + (08) WEB This information furnished by Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not 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 Pr Micrel for any damages resulting from such use or sale. 00 MIC76 8 March 006