SLVS875C January 2009 – November 2014 TPS54332
The TPS54332 implements current mode control that uses the COMP pin voltage to turn off the high-side MOSFET on a cycle-by-cycle basis. Every cycle, the switch current and the COMP pin voltage are compared; when the peak inductor current intersects the COMP pin voltage, the high-side switch is turned off. During overcurrent conditions that pull the output voltage low, the error amplifier responds by driving the COMP pin high, causing the switch current to increase. The COMP pin has a maximum clamp internally, which limit the output current.
The TPS54332 provides robust protection during short circuits. There is potential for overcurrent runaway in the output inductor during a short circuit at the output. The TPS54332 solves this issue by increasing the off-time during short circuit conditions by lowering the switching frequency. The switching frequency is divided by 8, 4, 2, and 1 as the voltage ramps from 0 V to 0.8 V on VSENSE pin. The relationship between the switching frequency and the VSENSE pin voltage is shown in Table 2.
|SWITCHING FREQUENCY||VSENSE PIN VOLTAGE|
|1 MHz||VSENSE ≥ 0.6 V|
|1 MHz / 2||0.6 V > VSENSE ≥ 0.4 V|
|1 MHz / 4||0.4 V > VSENSE ≥ 0.2 V|
|1 MHz / 8||0.2 V > VSENSE|