# Battery voltage regulation

Hello all,

I am in the stressful part of my project where I am kind of starting to be hopeless about this,

I am trying to regulate the voltage from a Li Ion battery (fully charged voltage is 4.2V and to completely discharge the battery the voltage drops to 2.7V before cutting off all the voltage and current). The thing is that I want to power my 3.3V and 1.8V devices with the voltage from the battery.

I am recharging the battery with a BQ24075 and the output voltage to my system is directly powered from the unregulated battery voltage so I am trying to look for a device that does step down voltage conversion (when the battery is between 4.2V and 3.3V or so) and also boost up voltage conversion (when battery is below 3.3V)

I know that I could use a step up converter to 5V and another device to step down the 5V to 3.3V but I want an IC that can handle both tasks, I already have many other devices in my design so I am trying to save some space and current consumption.

I will appreciate all the help.

To be honest I am very confused of what you actually want. You talk about 3.3Volt, 1.8Volt, then again about 5Volt and 3.3Volt. What do you actually want to achieve?

You need a buck-boost module instead of a buck or boost module. You can get assembled ones from ebay (search for dc dc step up down, then read the specs to confirm ). You can see on the boards that these will have two inductors.

Why do you need to regulate that voltage at all? If you're running at 8mhz, it's all within spec, and a buck-boost converter would lower efficiency... If I'm running off a LiPo, I would run directly off the battery, at the battery voltage.

This is what you need. You donâ€™t mention what current draw you require though

3.3V Step up/Down Module

MarkDerbyshire:
This is what you need. You don't mention what current draw you require though

3.3V Step up/Down Module

The current draw would be minimum 20mA and maximum 100mA.

Mikeb1970:
To be honest I am very confused of what you actually want. You talk about 3.3Volt, 1.8Volt, then again about 5Volt and 3.3Volt. What do you actually want to achieve?

Power 3.3V devices, that's why I need to regulate the battery voltage to 3.3V at all given cases.

Many devices have wide operating range - ATMega328p (main chip of Arduino Uno) works from 1.8 to 5.5 V. Maybe your 3V3 modules would be happy with unregulated voltage?