9.2.6 Regulator with Early Warning and Auxiliary Output
The LP2951 can be used to build a Regulator with early warning and auxiliary output as Figure 48 shows. it has below features:
- Early warning flag on low input voltage
- Main output latches off at lower input voltages
- Battery backup on auxiliary output
- Operation: VOUT of regulator 1 is programmed one diode drop above 5 V. Its error flag becomes active when VIN ≤ 5.7 V. When VIN drops below 5.3 V, the error flag of regulator 2 becomes active and via Q1 latches the main output off. When VIN again exceeds 5.7 V regulator 1 is back in regulation and the early warning signal rises, unlatching regulator 2 via D3.
Figure 48. Regulator With Early Warning and Auxiliary Output