This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMR23630 Frequency Foldback

Other Parts Discussed in Thread: LMR23630

Hi,

We got a question from customer about LMR23630.
Could you help us?

[Question]
- When the IC is synchronized external clock, does the frequency foldback function be enabled?
  They want fixed frequency in sychronized operation, even if the IC is in low dropout condition.

Best Regards,
tateo

  • Hello Yamashiro-san,

    This is a good question. It looks like there is a forced PWM option of this part (LMR23630AF) for constant frequency operation.
    I will forward this to the applications engineer of this part to confirm the operation when external clock is used.

    Do you know the customer Vin range, Vout, and external clock they would like to use?

    Regards,
    Denislav
  • Hello again, 

    I found an EVM with the LMR23630A on it (not the FPWM version). 

    It looks like the frequency foldback in dropout is active with the external sync ON.

    This maximizes the VIN range of the part for output regulation, but the trade-off is reduced frequency. 

    I assume the FPWM option behaves the same way, but I will let the applications engineer on this device comment. I have forwarded this question to him. 

    Here are a couple of snapshots:

    Not in dropout yet: SW follows the SYNC signal:

    Here is the regulator in dropout (notice the lower input voltage). The SW frequency is not locked to the external sync anymore and operates at lower frequency:

    Cheers, 
    Denislav

  • Thank you for your support.
    It is automotive application. Battery voltage might be drop in cranking condition. And they use external clock for avoiding AM band.
    Please let me know if you get the information of FPWM.

    Best Regards,
    tateo

  • Hello Yamashiro-san, 

    I confirmed with the applications engineer on that part that the FPWM version of the device has the same behavior. 

    Cheers, 
    Denislav

  • Hi Tateo,
    The cold crank is an abornarm condition and will not last for a long time. So pls check with ctm if the frequency foldback is acceptable in dropout. also the frequency foldback is designed to achieve low dropout at low VIN. without this function, the dropout voltage will be larger.