The TPS40042 DC/DC controller is designed to operate with an input source between a 3.0 V and 5.5 V. To reduce the number of external components, a number of operating parameters are fixed internally. The operating frequency for example, is internally set at 600 kHz.
One of three short circuit threshold levels may be selected by the addition of an external resistor from the COMP pin to circuit ground (no resistor is the default setting). During power on, and before the internal soft start commands the output voltage to rise, the TPS40042 enters a calibration cycle, measures the current out of the COMP pin, and selects an internal SCP threshold voltage. At the end of the 1.5-ms calibration time, the output voltage is allowed to enter soft-start.
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