Dear ADI engineer.
We are designing a power supply system using the LTC2924.
OUT1-4 are all High, and the four surrounding Power supply ICs are running. A voltage of about 0.9V is input to all IN1-4.
However, the Done signal does not go low. The figure below shows the waveforms of DONE and TMR at that time.
Fig1. TMR & DONE wave
The circuit conditions are as follows.
- VCC=5V, GND=0V,
- The DONE & FAULT pin is pulled up to 1.8V with 4.7kΩ.
- A 0.015uF capacitor is connected between GND on the TMR pin.
- The HYS/CFG pin is pulled down with 49.9kΩ.
- PGT pin is connected to GND.
When simulating with LTspice, the DONE signal was low.
Fig2. TMR & DONE
We are in trouble because we do not know the cause.
Please consider what you can think of.