The nominal output voltage of the converter can be adjusted using the VREF_TRIM command. See the VREF_TRIM command description for the format of this command as used in the TPS4022 device . The adjustment range is between -20% and +10% from the nominal output voltage. The VREF_TRIM command is typically used to trim the final output voltage of the converter without relying on high precision resistors being used in Figure 8-1. The resolution of the adjustment is 2 mV. The combination of margining and VREF_TRIM is limited to the range between –30% and +10% from the nominal output voltage. Exceeding this range is not supported.

The TPS4022 device operates in three states that determine the actual output voltage:

• No output margin
• Margin high
• Margin low

These output states are set using the OPERATION command. The FB pin reference voltage is calculated as follows in each of these states.

No margin voltage:

Equation 8.

Margin high voltage state:

Equation 9.

Margin low state:

Equation 10.

where

• V_FB is the FB pin voltage
• VREF_TRIM is the offset voltage in volts to be applied to the output voltage
• VREF_MARGIN_HIGH is the requested margin high voltage
• VREF_MARGIN_LOW is the requested margin low voltage