This reference design demonstrates an ultra-small power supply solution (8.5 mm2 total) for an efficient and low-noise rail in portable personal electronic devices, such as wearables, smart watches, smartphones, headsets, headphones, earbuds, and camera modules. A low dropout (LDO) linear regulator follows a DC/DC converter to deliver the same low-noise performance of an LDO with the high efficiency of a DC/DC converter. The overall no load input current (also known as switching IQ) of only 8 µA maintains higher efficiency than an LDO-only based design, while the near 100-µV output noise cleanly powers the sensitive load better than a DC/DC-only design. This design guide documents and compares the critical performance characteristics, such as efficiency, IQ, ripple, and so forth, of all three design types: LDO only, DC/DC only, and LDO after DC/DC.
- Solution size of 8.5 mm2 and height below 0.65 mm
- No load input current (switching IQ) of 8 µA
- Near 100-µV output noise (10 Hz to 100 kHz)
- Simple output voltage adjustment down to 0.5 VOUT
- 2.6-V to 5.5-V VIN range for 1.2 VOUT
- 300-mA LDO output current (1 A at DC/DC output)