SNVSCW3 November 2024 LM644A2-Q1
PRODUCTION DATA
The LM644A2-Q1 uses VCC as the internal power supply. VCC is, in turn, powered from VIN or VOSNS1/BIAS. After the device is active power comes from VIN, if BIAS is less than approximately 3.1V. Power comes from BIAS, if BIAS is more than 3.1V. VCC is typically 3V to 3.3V under most conditions, but can be lower if VIN is very low. To prevent unsafe operation, VCC has a UVLO that prevents switching if the internal voltage is too low. See VCC_UVLO and VCC_UVLO_HYST . During start-up, VCC momentarily exceeds the normal operating voltage until VCC_UVLO is exceeded, then drops to the normal operating voltage. These UVLO values, when combined with the dropout of the LDO when powering the LM644A2-Q1, are used to derive minimum input operating voltage.