ZHCSJE4B September 2017 – February 2019 TPS61085A-Q1
PRODUCTION DATA.
The boost converter has an adjustable soft start to prevent high inrush current during start-up. To minimize the inrush current during start-up an external capacitor connected to the soft-start pin SS is used to slowly ramp up the internal current limit of the boost converter when charged with a constant current. When the EN pin is pulled high, the soft-start capacitor (CSS) is immediately charged to 0.3 V. The capacitor is then charged at a constant current of 10 µA typically until the output of the boost converter VS has reached its power good threshold (90% of VS nominal value). During this time, the SS voltage directly controls the peak inductor current, starting with 0 A at VSS = 0.3 V up to the full current limit at VSS ≈ 800 mV. The maximum load current is available after the soft start is completed. The larger the capacitor the slower the ramp of the current limit and the longer the soft-start time. A 100-nF capacitor is usually sufficient for most of the applications. When the EN pin is pulled low, the soft-start capacitor is discharged to ground.