Control circuit for Hot swap controller [duplicate]

I’m working on a 48 V (60 V max) BLDC logic board, and I’m using an LM5069 hot-swap controller for the logic board. I need to control the UVLO/EN pin so the user can turn the system ON using a momentary push-button, and the MCU can turn it OFF later. The UVLO/EN is connected to voltage divider as well for undervoltage shutdown. As per LM5069 datasheet - if the UVLO/EN is pulled to ground it will get shutdown and if the voltage is above 2.5V, it will Turn ON.

What the circuit is intended to do - Power-up (Battery Connected)

• When battery is connected, I want LM5069 to remain OFF.

• The user presses SW1, which pulls the node to GND → this should bring UVLO high through the transistor network and turn LM5069 ON.

• Once LM5069 turns ON, the downstream DC-DC generates logic power, and the MCU becomes active.

System running

• The MCU has a control signal PWR_KILL_SIG which drives Q1.

• When MCU pulls this low, Q1 should pull the node low and shut down the system by disabling UVLO.

• The same physical switch (SW1) is also going to controller and pulled by with 3.3K to 3.3V and used for other MCU functions like → Bluetooth activation. (When MCU is active and switch is intentionally pressed after power up only then MCU should detect the switch press otherwise it should be isolated from the R45 node. Can we add diode in between?)

• But pressing it while ON should not interrupt power, since LM5069 gate is already ON.

1. Is this the right way to control LM5069 UVLO with a momentary switch + MCU override?
2. Any risk of false triggering due to switch bounce or noise at 48 V?
3. I need very low standby current draw from 48V when system is shutdown (less than < 1mA)

posted 3 months ago

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Embedded_geek‭

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