Post History

Powering ADC using Buck Boost Converter

**Basic Explanation of my System:**

The proposed design is a battery-powered wearable device that integrates advanced sensing and power management features. The system operates primarily from a single-cell Li-ion battery (3.7 V nominal) and includes a USB Type-C interface for charging and external power supply.

The device uses a battery charger with power-path management ( [BQ24075](https://www.ti.com/lit/ds/symlink/bq24075.pdf)) to ensure seamless operation:

When USB power is connected, the system is powered directly from the USB input while simultaneously charging the battery.
When USB is disconnected, the system automatically switches to battery power without interruption.
A [fuel gauge IC](https://www.analog.com/media/en/technical-documentation/data-sheets/max17048-max17049.pdf) monitors battery health parameters such as voltage, state of charge (SOC), and remaining capacity, reporting these to the microcontroller via I²C.

The system includes an electrochemical front end ([AD5941](https://www.analog.com/media/en/technical-documentation/data-sheets/ad5940-5941.pdf)) with a 16-bit ADC for high-precision sensor measurements.

Sensor signals are routed through a multiplexer (MUX) to the [AD5941](https://www.analog.com/media/en/technical-documentation/data-sheets/ad5940-5941.pdf), which interfaces with an STM32 microcontroller development board for data acquisition and processing.

**My Question**

Initially, I considered using the [ADM7155](https://www.analog.com/media/en/technical-documentation/data-sheets/adm7155.pdf) low-noise LDO to power the ADC. However, given the system’s 3.7 V Li-ion battery, the limited headroom and dropout voltage of the [ADM7155](https://www.analog.com/media/en/technical-documentation/data-sheets/adm7155.pdf) present a challenge, especially as the battery discharges.

To address this, I decided to use a buck-boost converter, specifically the [ADP2504](https://www.analog.com/media/en/technical-documentation/data-sheets/adp2503_2504.pdf), which can maintain a stable output voltage across the full battery discharge range and during USB power input. This ensures reliable operation for both the ADC and the microcontroller.

For powering the [AD5941](https://www.analog.com/media/en/technical-documentation/data-sheets/ad5940-5941.pdf), my plan is to supply DVDD directly from the [ADP2504](https://www.analog.com/media/en/technical-documentation/data-sheets/adp2503_2504.pdf) output and derive AVDD from DVDD using a ferrite bead for isolation, along with appropriate decoupling capacitors. This approach minimizes noise coupling between digital and analog domains while maintaining a compact and efficient power architecture.

Could you confirm if this is an optimal solution for powering the [AD5941](https://www.analog.com/media/en/technical-documentation/data-sheets/ad5940-5941.pdf) in a wearable application.

Or may I know you have any suggestions for better circuit /IC options