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MIC5157 Datasheet(PDF) 7 Page - Micrel Semiconductor |
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MIC5157 Datasheet(HTML) 7 Page - Micrel Semiconductor |
7 / 13 page August 2005 7 MIC5156/5157/5158 MIC5156/5157/5158 Micrel, Inc. Functional Description A Super LDO Regulator is a complete regulator built around Micrel’s Super LDO Regulator Controller. Refer to Block Diagrams MIC5156, MIC5157, and MIC5158. Version Differences The MIC5156 requires an external voltage for MOSFET gate drive and is available in 3.3V fixed output, 5V fixed output, or adjustable output versions. With 8-pins, the MIC5156 is the smallest of the Super LDO Regulator Controllers. The MIC5157 and MIC5158 each have an internal charge pump which provides MOSFET gate drive voltage. The MIC5157 has a selectable fixed output of 3.3V, 5V, or 12V. The MIC5158 may be configured for a fixed 5V or adjustable output. Enable (EN) With at least 3.0V on VDD, applying a TTL low to EN places the controller in shutdown mode. A TTL high on EN enables the internal bias circuit which powers all internal circuitry. EN must be pulled high if unused. The voltage applied to EN may be as high as 36V. The controller draws less than 1µA in shutdown mode. Gate Enhancement The Super LDO Regulator Controller manages the gate- 1.235V Bandgap Reference VCP Clamp Internal Bias Error Amp 75mV 35mV EA S (Source) ILIMIT Comparator D (Drain) [ ILIMIT] G (Gate) VCP VDD VOUT Comparator to all internal blocks GND Regulated +3.6V Output +5V Input Q1 IRFZ44 RS 3mΩ 1µF 16.6V 32k 10k 5V FB Oscillator Charge Pump Tripler C1+ C1– C2+ C2– 0.1µF 0.1µF C1 C2 C3 FLAG 19.1k 10.0k EN Enable Shutdown CL Block Diagram MIC5158 Block Diagram with External Components Adjustable Power Supply, 3.6V Configuration to-source enhancement voltage for an external N-channel MOSFET(regulatorpasselement)placedbetweenthesupply and the load. The gate-to-source voltage may vary from 1V to 16V depending upon the supply and load conditions. Because the source voltage (output) approaches the drain voltage (input) when the regulator is in dropout and the MOSFET is fully enhanced, an additional higher supply voltage is required to produce the necessary gate-to-source enhancement. This higher gate drive voltage is provided by an external gate drive supply (MIC5156) or by an internal charge pump (MIC5157 and MIC5158). Gate Drive Supply Voltage (MIC5156 only) The gate drive supply voltage must not be more than 14V above the supply voltage (VP – VDD < 14V). The minimum necessary gate drive supply voltage is: VP = VOUT + VGS + 1 where: VP = gate drive supply voltage VOUT = regulator output voltage VGS = gate-to-source voltage for full MOSFET gate enhancement The error amplifier uses the gate drive supply voltage to drive the gate of the external MOSFET. The error amplifier output can swing to within 1V of VP. |
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Similar Description - MIC5157 |
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