ZHCSGE0B June 2017 – January 2019 TPS53681
PRODUCTION DATA.
The basic mechanism for current sharing is to sense the average phase current, then adjust the pulse width of each phase to equalize the current in each phase as shown in Figure 10. The PWM comparator (not shown) starts a pulse when the feedback voltage meets the reference. The VIN voltage charges Ct(on) through Rt(on). The pulse terminates when the voltage at Ct(on) matches the on-time reference, which normally equals the DAC voltage (VDAC).
The circuit operates in the following fashion. First assume that the 1-µs averaged value from each phase current are equal. In this case, the PWM modulator terminates at VDAC, and the normal pulse width is delivered to the system. If instead, I1 > IAVG, then an offset is subtracted from VDAC, and the pulse width for Phase 1 is shortened to reduce the phase current in Phase 1 for balancing. If I1 < IAVG, then a longer pulse is generated to increase the phase current in Phase 1 to achieve current balancing.