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LTM4664 Input Power

I need one channel to be powered on all the time from standby power primary source (5V). Other three channels will be powered later from main channel of primary source (12V) . Is it possible to have separate input power for each channel? Internal structure shows that this channels are independent to each other, but there is internal CLK signal between channels. I have doubt that unpowered channel shunt CLKOUT signal from powered channel. Thank you,

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  • Hi Pavel, 

    Sorry for the delay. I assume you are talking about the LTM4644 quad output buck uModule regulator. Yes this should be possible, the stages are independent (only connected GND, and Clock signals propagated internally. Note that when there is no CLKIN signal to one of the channels the operating frequency of that channel will still be 1MHz, as each has a 162k from FREQ pin to ground which sets this default operating frequency. So you could have channel 4 powered by 5Vin and come up first, it will by default operate at 1MHz. Then channels 1,2,3 which are powered by 12Vin can come up later and still operating at 1MHz. 

    Thanks. 

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  • Hi Pavel, 

    Sorry for the delay. I assume you are talking about the LTM4644 quad output buck uModule regulator. Yes this should be possible, the stages are independent (only connected GND, and Clock signals propagated internally. Note that when there is no CLKIN signal to one of the channels the operating frequency of that channel will still be 1MHz, as each has a 162k from FREQ pin to ground which sets this default operating frequency. So you could have channel 4 powered by 5Vin and come up first, it will by default operate at 1MHz. Then channels 1,2,3 which are powered by 12Vin can come up later and still operating at 1MHz. 

    Thanks. 

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