LTM4613 Simulation to reduce Quiescent Current

Question

Hi, 
 PFA 
 LTM4613_Tracking.rar My VIN range for LTM4613 is 22V- 34V. In such a case I expect power loss during low current operation due to quiescent current. In order to avoid the loss i use an LTC3245 charge pump to generate 5V for powering DRVcc. 
 1. Is the current rating of LTC3245 sufficient to handle DRVcc of two LTM4613.??(max avg considered is 140mA). Simulation shows 560mA pulse current 
 2. How should I power LTC6908HS6-1?? from INTVCC of 5.5V or can I power from LTC3245?? Will the noise output of create huge jitters at output of LTC6908HS6-1?? 
 3. Is it mandatory to use Tracking mode?? Can i have independent Soft Start for 3.6V LTM4613?? if so what design change i should consider??

yanliang · Accepted Answer

1. Io of LTC3245 go up to 250mA, should be sufficient to drive two DRVCC of LTM4613 
 2. It should be ok to power up LTC6908 from LTC3245. The LTC3245 datasheet shows Vout ripple around 20-30mV for low noise mode. You can add more cap at V+ pin of LTC6908. 
 3. Tracking node is not mandatory. Add a capacitor to TRACK/SS pin of LTM4613 can set LTM4613 to soft start. The capacitance value will set the soft start time)

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LTM4613 Simulation to reduce Quiescent Current