SBVS382A December 2020 – March 2023 TLV766-Q1
PRODUCTION DATA
If the input voltage is lower than the set MID_OUT voltage plus the specified VDO(MID_OUT) dropout voltage, but all other conditions are met for normal operation, the device operates in VMID_OUT dropout mode. When the device operates in this mode while VMID_OUT voltage is still higher than VOUT(nom) + VDO(OUT), then VOUT is still in regulation however VMID_OUT voltage is in its dropout mode. In VMID_OUT dropout mode, VMID_OUT voltage tracks the input voltage and during this mode, the transient performance of VMID_OUT voltage becomes significantly degraded because the MID_OUT pass transistor is in the ohmic or triode region, and acts as a switch. Also VMID_OUT line or load transients can result in large VMID_OUT voltage deviations.
The device enters VDO(OUT) dropout mode when the input voltage is lower than the set MID_OUT voltage and VMID_OUT is lower than VOUT(nom) + VDO(OUT). In VOUT dropout mode, VOUT voltage tracks VMID_OUT voltage which in return tracks the input voltage. During this mode, the transient performance of both VMID_OUT and VOUT voltages becomes significantly degraded because the pass transistors are in the ohmic or triode region and acting as switches. Also line or load transients can result in large VMID_OUT and VOUT voltages deviations.
When the device is in a steady dropout state (defined as when the device is in dropout, VIN < VOUT(NOM) + VDO, directly after being in a normal regulation state, but not during start-up), the pass transistor is driven into the ohmic or triode region. When the input voltage returns to a value greater than or equal to the nominal output voltage plus the dropout voltage (VOUT(NOM) + VDO), the output voltage can overshoot for a short period of time while the device pulls the pass transistor back into the linear region.