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  • Dr. Tobias Weltner
  • Jul 23, 2025

PB0A I2C Production Setup

Using PB0A I2C Interface In Power-Management Applications

PB0A provides great opportunities to control and fine-tune the power management functions via a microcontroller and its I2C interface.

For this to be successful, a few caveats need to be addressed. The PB0A basic I2C functionality was addressed earlier in a test setup and isn’t repeated here. Please review the introduction when needed.

In this article, PB0A production use is discussed.

Overview

For production use, there are two challenges:

  • Microcontroller Required:
    Since IP5306 has no built-in memory, it cannot store adjusted settings, nor can you “pre-program” the chip to your needs. Instead, your project must contain a microcontroller: each time IP5306 enables its power output, the microcontroller needs to re-configure the chip via I2C.
  • TTL Logic Levels: Your microcontroller and the IP5306 chip used by PB0A must use the same voltages for logic levels in order to successufully communicate via I2C. Since the IP5306 is powered by the LiIon battery (voltage range: 2.8-4.2V), your microcontroller cannot directly interface with IP5306. Instead, a level shifter must be used. If you use a 3.3V microcontroller, then it needs to be a special level shifter that accepts higher as well as lower voltages on the HV side since 3.3V are somewhere in the middle of the range of the battery voltage. If you use a 5V microcontroller, any I2C compatible level shifter will do.

Circuit Design Considerations

In this example, the microcontoller will be an affordable and small ESP32-C3 SuperMini.

Level Shifter

Since IP5306 communicates via I2C at 400kHz (“fast” I2C), a sufficiently fast I2C compatible level shifter is required.

Special Challenge: 3.3V Microcontroller

Since ESP32-C3 SuperMini is a 3.3V microcontroller, the voltage crossing challenge applies: on the high voltage side of the level shifter, the battery voltage can be anywhere in a range of 2.8-4.2V. On the low voltage side is the 3.3V microcontroller supply. So when the battery is in its last 25% of capacity, its voltage will be lower than the microcontroller voltage.

This is a serious problem for most level shifters, especially when chip-based: they require LV<=HV. So when the voltage on the HV side (battery) drops below the voltage on the LV side (microcontroller), they no longer work correctly.

  • A simple workaround is the use of MOSFET-based level shifters such as BSS138-based level shifters. Even though such level shifters have the same LV<=HV requirement, due to the body diode inside the MOSFET, they typically keep working even when LV>HV.

    Using any normal level shifter - including MOSFET types - with LV>HV is unsupported and not guaranteed to work. It typically works, and this is good enough for hobbyist projects. For more reliable operation, use galvanically isolated level shifters, i.e. based on ISO1540/ISO1640

  • Or eliminate the voltage crossing challenge altogether by making sure the microcontroller voltage is strictly below or above battery voltage at all times, i.e. by using 1.6V or 5V microcontrollers instead of 3.3V.

Powering the Microcontroller

The microcontroller needs to re-configure PB0A whenever it enables its power output. The simplest way to achieve this is to power the microcontroller via its 5V pin directly off the PB0A power output.

This way, whenever the power output is enabled, the microcontroller starts, and whenever the power output is disabled, the microcontroller is turned off.

This has a number of advantages:

  • The microcontroller runs only when needed and does not consume power when PB0A is in standby.
  • If you use the microcontroller just for PB0A configuration, you can send it to deep sleep once the configuration is done.
  • If you use PB0A to provide portable power to your microcontroller project, the microcontroller can run as long as needed. The microcontroller can even turn off the PB0A power supply via I2C, which effectively is an elegant way of powering down your portable device.

Schematics

Here is the parts list:

Wiring

The required connections can be seen here:

Level Shifter

Note that the level shifter “translates” four lines.

Strictly speaking, only the two I2C lines are required, but since the level shifter has four channels, two additional lines are translated for added opportunities:

  • I2C: the original I2C lines SDA and SCK/SCL
  • IRQ: the interrupt line that signals the state of PB0A (optional, not required)
  • GPIO: the *PB0A built-in GPIO on pin K. This way, the microcontroller can simulate push button presses, i.e. to turn off the power supply (optional, can also be achieved via I2C)

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(content created Jul 23, 2025)

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