Hello,
I'm building a DIY device based on ESP32, with E-Ink screen, that will also do WiFi communication. Maybe I'll later switch to ZigBee or other protocol based on IEEE 802.15.4.
The device should last a few months on two NiMH batteries, and it will spend the most of its life being idle (deep sleeping).
For this, I'm searching for a boost or buck-boost voltage regulator with a low quiescent current. I'll be using Panasonic Eneloop due to their low self-discharge characteristics.
Requirements:
- up to 300mA output current for powering ESP32 with peripherals. The most power demanding is the WiFi communication, so the rest seems negligible.
- works also in cold temperatures:
- voltage of NiMH battery gets low at low (freezing) temperatures, and at the end of discharge curve, when the device should signal battery replacement, the voltage is in range between 1.1V and 1.05V (and lower, that I don't necessarily care about this very tail),
- fully charged NiMH has a potential to reach 1.45V and the device should handle this without being damaged, and also it should be compatible with Alkaline batteries with 1.5V at full charge,
- the preferred compact option - 2x NiMH powering (compatible with Alkaline) - works with input voltage as low as 2.1V, and up to 3V,
- rather not option, but maybe yes if there's a strong reason - 3x NiMH powering (compatible with Alkaline) - works with input voltage as low as 3.15V, and up to 4.5V.
From the research I've done, I've collected following regulators, that match input voltage requirements:
| Name | Type | Vin - startup | V - in - operating | NiMH count | V - output | Max output current | Quiescent Current |
|---|---|---|---|---|---|---|---|
| LTC3129-1 | buck-boost | 2.42V | 1.92V to 15V | 3 to many | 3.3V, 5V, other | 200mA | 1.3 µA |
| LTC3246 | buck-boost | 2.7V | 2.7V – 38V | 3 to many | 3,3V, 5V, other | 500mA | 20μA Operating, 1.5μA in shutdown |
| MAX756 | boost | 1.1V | 0.7V to 1.8V | 1 | 3.3V, 5V, other | 300mA (3.3V), 200mA (5V) | 60µA, 20µA in shutdown |
| MCP1623 | boost | 0.65V | 0.35V to ≤ Vout | 1 to 2 | 3.3V, 5V, other | 175mA (2.4V in, 3.3V out), peak 475mA | 19µA |
| MCP1640 | boost | 0.65V | 0.35V to ≤ Vout | 1 to 2 | 3.3V, other | 350mA (2.4V in, 3.3V out), peak 800mA | 19µA |
| MT3608 | boost | 2V | 2V - 24V | 2 (for 3.3V output) | up to 28V | 4A (?) | 100μA typical, 200μA max, 0.1μA in shutdown |
| TPS61021A | boost | 0.9V | 0.5V to 4.4V | 1 to 2 (for 3.3V output) | 1.8V - 4.0V | 1.5A | 17µA, 0.5μA in shutdown |
| TPS6120x | boost | 0.5V | 0.3V to 5.5V | 1 to 2 (for 3.3V output) | 1.8V - 5.5V | 300mA (3.3V), 600mA (5V) | 55μA, 1μA in shutdown |
| TPS63001 | buck-boost | 1.9V | 1.8V to 5.5V | 2 to 3 | 1.2V - 5.5V | 800mA (boosting to 3.3V) | 50μA, 0.1μA in shutdown |
| TPS63020 | buck-boost | 1.9V | 1.8V to 5.5V | 2 to 3 | 1.2V - 5.5V | 2A (V-in > 2.5V, V-out 3.3V) | 25µA, 0.1μA in shutdown |
From discovered regulators, MCP1640 and TPS61021A seem the most interesting to me, as these can go up to 300mA (or more) output current, and have very low quiescent current. After those go TPS63020, and then TPS6120x, TPS63001 and MAX756.
What would you recommend to go with?
What's the most common voltage regulator, that you have a good experience with?