Scheme

Voltage control

LM51772 gives the ability to control the output voltage in two ways simultaneously: I2C and external(ATRK or DTRK). To achieve a small error, we could set a rough voltage with I2C, then fine-tune it with ATRK. The DAC signal should be attenuated and shifted to near FB, 0.8V

The goal is to manipulate the ATRK lower than 0.8V. So, adding 750mV and choosing a gain 20mV/V.

Modelling with tools.analog.com

AnalogDevices has an instrument for designing, so it's simple to generate new schematic:

Looks fine. Let's export and model in LTSpice

Modelling with LTSpice

DC sweep 0-2.5 Vin

Achieved range in simulation from 753 to 796 mV. ATRK step - 12uV, Vout step - 0.5mV

Average current control

Average current control has another architecture, so we have two options:

• 10/20mA steps via I2C. The desired step is 1mA.
• External ISET with a resistor.

 Instead of a resistor, we'll use a DAC with a FET, stabilising the current in the ISET net. 

External DACs

Added DACS on the board just in case something goes wrong with the built-in STM32.

PCB

Simply put everything on the board

This board connects the Nucleo board with the LM51772EVM. We're almost ready to test everything together!