JAJSIO5B July 2019 – February 2020 LMR36506-Q1
ADVANCE INFORMATION for pre-production products; subject to change without notice.
The LMR36506-Q1 uses the VCC pin for all the internal power supply. The VCC pin draws power either from the VIN (for adjustable output variants) or the VOUT/BIAS (for fixed output variants). In fixed output variants, once the LMR36506-Q1 is active, the VCC continues to draw power from the input voltage, VIN, when the VOUT/BIAS voltage measures less than 3.15 V (during start-up and other transient conditions) or from the VOUT/BIAS itself when VOUT/BIAS measures is more than 3.15 V (once the device has reached steady state). VCC typically measures 3.3 V under most conditions. To prevent unsafe operation, VCC has an undervoltage lockout, which prevents switching if the internal voltage is too low. See VVCC_UVLO and VVCC_UVLO_HYST in the Electrical Characteristics table. During start-up, VCC momentarily exceeds the normal operating voltage until VCC_UVLO_HYST is exceeded, then drops to the normal operating voltage. Note that these undervoltage lockout values, when combined with the LDO dropout and while powering the LMR36506-Q1, are used to derive the minimum rising operating voltage and the subsequent falling threshold.