ZHCSGR8A September 2017 – July 2018 TPS63710
PRODUCTION DATA.
The converter operates with a fixed-frequency, pulse-width-modulated control. In the OFF-time, the rectifier switch (RECT) and the high-side switch (HSD) are turned on to charge CCP to the input voltage. As well, the inductor current ramps down, continuing to charge the output capacitor. During the ON-time, the low-side switch (LSD) is closed and HSD and RECT are opened. CCP inverts the supply voltage onto SW, and the inductor current is ramped up. The LC output filter filters the SW voltage, just like in a step-down converter. Charging the CCP capacitor during the OFF-time limits the maximum duty cycle. The upper limit of the duty cycle is 70% to allow charging the CCP capacitor in the remaining 30%.
Lower negative voltages require higher positive supply voltages. For an output voltage of -1.8 V, a minimum input voltage of 4.5 V is sufficient while for an output voltage of -3.3 V, the input voltage has to be above 6 V. See Figure 36 to Figure 38 for the relation of input voltage, output voltage and temperature vs output current.
For high input voltages and, in absolute value, small output voltages, the device operates with its minimum on-time (ton,min) to generate the duty cycle required for this VIN and VOUT ratio. This means that, for such cases, the switching frequency is lower than fS.