SLUSAQ4G October 2011 – September 2022 TPS40422
PRODUCTION DATA
The TPS4022 device sets the output voltage in a way that is very similar to a traditional analog controller by using a voltage divider from the output to the FB (feedback) pin. The output voltage must be divided down to the nominal reference voltage of 600 mV. Figure 8-1 shows the typical connections for the controller. The device senses the voltage at the load by using the unity gain differential voltage sense amplifier. This functionality provides better load regulation for output voltages lower than 5-V nominal (see the Section 7.5 table for the maximum output voltage specification for the differential sense amplifier). For output voltages above this level, connect the output voltage directly to the junction of R1 and C1, leave DIFFO1 open, and do not connect the VSNS1 pin to the output voltage. The differential amplifier may also be used elsewhere in the overall system as a voltage buffer, provided the electrical specifications are not exceeded.
The components shown in Figure 8-1 that determine the nominal output voltage are R1 and R2. In most cases, choose a value for R to ensure the feedback compensation values (R3, R4, C1, C2 and C3) come close to readily available standard values. A value for R2 is then calculated in Equation 1.
where
There is no DIFFO2 pin. In dual-output mode, VSNS2 and GSNS2 are connected to the load for channel 2 and the device uses the DIFFO2 signal internally to provide voltage monitoring. Connect the output directly to the junction of R1 and C1 for channel 2 to set the output voltage and for feedback.
The DIFFO1 pin operates at voltages up to (VBP6–0.2 V). If the voltage between the VSNS1 and GSNS1 pins is higher than (VBP6–0.2 V) during any condition, the output voltage moves out of regulation because the DIFFO1 voltage is limited by BP6. To prevent this from happening, the BP6 voltage must be pre-biased before the PWM turns on, and (VBP6–0.2 V) must remain higher than the voltage between the VSNS1 and GSNS1 pins until the PWM turns off.
The feedback voltage can be changed to a value between –30% and +10% from the nominal 600 mV using PMBus commands. This adjustment allows the output voltage to vary by the same percentage. See the Section 8.5.1 section for more details.