LT8705A, LTC4000 operation error

If the LT8705A internal LDO has to get its power from a high voltage, the internal LDO will dissipate a lot of power and heat. Try suppling EXTVCC with a voltage of 10V. If the IC is already damaged, you will have to replace the LT8705A first.

Thank you for answer.

I replaced the IC chip because it seemed to be damaged.

After replacing the IC chip, I took a measurement and it still generates a lot of heat.

When the diode resistance value (R11) of the GATE power terminal is changed from 4 ohm to 500 ohm, the current is 10 mA and no heat is generated.
(Current value when resistance value is 4 ohm: 50mA)

I think I've found the part that causes the heat, but I'm still not sure what's causing it. However, in this case, the SS pin voltage remains at 0.5V.

Can I get some help on this issue?

A current draw of 50mA is easily within the range of normal operation. Internal LDO power dissipation:  (36V - 6V) * 50mA = 1.5W. If you supplied EXTVCC with a 10V supply, power dissipation in the LDO would be:  (10V - 6V) * 50mA = 0.2W. If the LT8705A doesn't have an excellent thermal path to dissipate the heat, it would easily get too hot with 1.5W of dissipation.

hello.
What is the difference between lt8705 and lt8705a?
Can I use the lt8705a on the demoboard dc2924a circuit?
thank you.

The LT8705A has some improvements mainly when transitioning from one mode to another. Functionally the parts are interchangeable.

Thank you for answer!

Thank you for answer!