1. What is the MIC3385?

️· It's a 600mA PWM power supply with a unique power-saving feature.
️· It has a "LOWQ" mode, which is a light-load mode. When activated (LOWQ pin pulled low), it shuts down the main PWM regulator and switches to an LDO (Low Dropout Regulator) to regulate the output. This dramatically reduces quiescent current (the current the chip itself draws when not supplying power).

2. Key Features and Benefits

️· High Efficiency: PWM mode provides efficient power delivery for higher current loads.
️· Ultra-Low Quiescent Current: LOWQ mode reduces quiescent current to just 18µA, maximizing battery life in light-load conditions.
️· Clean Output: LOWQ mode provides a clean, low-noise output.
️· Smooth Transition: The transition between PWM and LDO modes is seamless, minimizing output voltage fluctuations.
️· Versatility: Suitable for a wide range of portable applications.

3. Operating Modes

️· LOWQ Mode (Light Load):
- LOWQ pin is pulled low.
- PWM regulator shuts down.
- Output is regulated by the LDO.
- Output current is limited to 60mA.
- Quiescent current is 18µA.
️· PWM Mode (High Load):
- LOWQ pin is pulled high.
- PWM regulator is active.
- Output current can reach 600mA.
- The LDO shuts off.

4. Important Components & Design Considerations

️· Input Capacitor: A 1µF ceramic capacitor (X5R or X7R dielectric) is essential to stabilize the input voltage.
️· Output Capacitor: 10µF output capacitor recommended. A small 10nF is also recommended.
️· Layout: Careful PCB layout is critical for stability and performance. Keep high-current traces short and wide.
️· Compensation: The MIC3385 has internal Type III compensation.
️· Bypass Components: Small capacitors for the LDO standby output are suggested, to mitigate transient effects.

5. Bill of Materials (BOM)

The datasheet includes a BOM listing common components used in a typical application circuit.

Summary Table

Feature	Description
Device	MIC3385
Type	600mA PWM Power Supply with LDO Standby
Quiescent Current (LOWQ Mode)	18µA
Output Current (PWM Mode)	Up to 600mA
LDO Output Current Limit	60mA
Operating Modes	PWM, LOWQ (LDO Standby)

Key Takeaway: The MIC3385 is designed to extend battery life in portable applications by combining efficient power delivery with a low-power standby mode, providing a good balance of performance and power efficiency. Proper component selection and PCB layout are crucial for achieving optimal results.