LT8616 PG Signal - LTspice vs Real World

Question

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?

MarkusHP · Accepted Answer

Hello, 
 as the part is specced to operate from 3.4V onwards all behaviour when Vin is lower is 'undefined'. And your MCU should also be noticed when VIN is out of spec, not only the derived voltages from Vin, Agree? All designs have to be verified with real hardware, not by LTSpice simulations alone. This would put too much burden/repsonsibility on the models.)

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LT8616 PG Signal - LTspice vs Real World