The 10A45 use a switched capacitorcharge pump to boost VIN to a regulated output voltage. Regulationis achieved by sensing the output voltage through an internalresistor divider and modulating the charge pump output currentbased on the error signal. A 2-phase nonoverlapping clock activatesthe charge pump switches. The flying capacitor is charged from VINon the first phase of the clock. On the second phase of the clockit is stacked in series with VIN and connected to VOUT. Thissequence of charging and discharging the flying capacitor continuesat a free running frequency of 1.2MHz (typ).
In shutdown mode all circuitry isturned off and the 10A45 draw only leakage current from the VINsupply. Furthermore, VOUT is disconnected from VIN. The EN pin is aCMOS input with a threshold voltage of approximately 0.8V. The10A45 is in shutdown when a logic low is applied to the EN pin.Since the EN pin is high impedance CMOS input it should never beallowed to float. To ensure that its state is defined it mustalways be driven with a valid logic level.
Short-CircuitProtection
The 10A45 have built-in short-circuitcurrent limiting. At short-circuit condition, it will automaticallylimit the output current to approximately 300mA.
Soft-Start
The 10A45 have built-in soft-startcircuitry to prevent excessive current flow at VIN during start-up.The soft-start time is preprogrammed to approximately 2.5ms, so thestart-up current will be primarily dependent upon the outputcapacitor.
