LMR43610-Q1: LMR43610-Q1 Cold Start question

Hi  Hongjia,

        Thanks for your reply. as you say, Can I comprehend that the IC can't work below 3.6 including cold start？ But as SPEC in the datasheet. it describes that the IC supports 3-VIN for automotive cold crank

Hi Yuming,

As I mentioned, if the device has start up and Vin drops afterwards, the device can still work with Vin=3V. The typical cold crank pulse is that battery drops from normal voltage like 12V to a low voltage like 3V. If the low voltage is equal or larger than 3V, the device can still operate. Hope it clarifies.

Regards,

Hongjia

Hi  hongjia,

        Thanks for your reply, I understand your mean. I just want to know one condition,if the VIN drop to 3.2V, what will happen to the VOUT

Hi Yuming,

If Vin drops to 3.2V, Vo will drop as well and try to follow Vin with maximum duty cycle. In this case here Vo=3.2V*Ton_max/(Ton_max+Toff)=3.2V*9us/(9us+65ns)=3.18V. 

Regards,

Hongjia

hi  hongjia,

      Thank you for your reply. as your formula, the Ton_max is 9 us, it corresponds to the FSW=111KHz, but the Toff corresponds to the FSW=2.2MHz,so it doesn't suit for the FSW=2.2MHz, Am I right? so as far as i'm concerned as the Ton_max is 0.45us . So am I right?