LT8616
Production
The LT8616 is a high efficiency, high speed, dual synchronous monolithic step-down switching regulator that consumes only 6.5μA of quiescent current with...
Datasheet
LT8616 on Analog.com
LT3973
Production
The LT3973 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 42V, and consumes only 2.5μA of...
Datasheet
LT3973 on Analog.com
Simulation: Using your LT8616 test-bench schematic, LT8616 is powered by a modified 12V supply that ramps from 12V to 0V after a 3ms delay (to allow start-up and stabilization). The PG1 and PG2 signals are pulled up to a separate 3.3V supply with 100k resistors. PG1 and PG2 both go high around 732us, as expected. As the 12V supply begins to ramp down, PG1 (5V out) goes low when Vin reaches ~4.95V, and PG2 (3.3V) goes low when Vin reaches 3.34V. Here is the problem: Both PG1 & PG2 are pulled low as Vin ramps down to 0V.
Real world: LT8616 Output1 configured for 5.5V, output 2 configured for 5.0V. PG1 & PG2 are pulled-up to a battery-backed 3.3V/3.0V supply, which powers the MCU. As the DC input supply is ramped down to 0V, the PG signals go low at the appropriate points. HOWEVER, as the input supply drops below ~3V, the PG signals cease to be pulled low, giving the MCU the false impression that the LT8616 outputs are 'good', when they clearly are not. This created problems.
It appears that the LT8616 simulation has an error in how it handles the PG outputs vs the input supply voltage. Can you please correct this?
