XRP7704 Datasheet, PDF (18/31 Pages) Exar Corporation – Quad-Output Digital PWM Buck Controller

REV 1.1.0
XRP7704
Quad-Output Digital PWM Buck Controller
Output Voltage Setting and Monitoring
The Output Voltage setting is controlled by the SET_VOUT_TARGET_CHx register. This register allows the user
to set the output voltage with a resolution of 50mV for output voltages between 0 and 2.5V and with a resolution
of 100mV for output voltages between 2.6V and 5.1V. Output voltages higher than 5.1V can be achieved by
adding an external voltage divider network. The output voltage of a particular channel can be read back using the
READ_VOUTx register.
Output Voltage from 0.9V to 5.1V
Per the equation below, for values between 0.9V and 5.1V the output voltage is equal to the binary number stored
in the SET_VOUT_TARGET_CHx register multiplied by 50mV. When programming an output voltage from 2.6V
to 5.1V, odd binary values should be avoided. As a result, the set resolution for an output voltage higher than
2.5V is 100mV.
Output VOUT Higher Than 5.1V
To set the output voltage higher than 5.1V, the user needs to add an external voltage divider. The resistors used
in the voltage divider should be below 10kΩ. The SET_VOUT_TARGET_CHx register should be set to 0x32
which is equivalent to an output voltage of 2.5V without the external divider network. The output voltage regulation
in this case might exceed 2% due to extra error from the resistor divider. R1 and R2 follow the definition below.
External divider network for high output voltage
Output Voltage Lower Than 0.9V
The XRP7704 can be programmed to regulate an output voltage lower than 0.9V. However, in this case the
specification of +-2% output voltage accuracy may be exceeded.
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