Tool/software:
Hello,
I didn't find in the datasheet what maximum value we can use for Cdvtdt.
I noticed on the eval board that using Cdvdt =22uF and Cout = 0F, the component cannot start and FLT is asserted after 6,6s (tSU_TMR).
From my understanding, the maximum Cdvdt would be defined by Tss < tSU_TMR using TPS1685_CALC_v2.xlsx excel sheet, but there is an additional delay between ↑SWEN and Vout starting to rise.
I also didn't find the specification for this delay in the datasheet, is this possible to know this value ? I can measure it but I don't know if it will vary from differents devices.
The last thing I see is to charge 4800uF using Cdvdt = 4,7uF with Vin = 30V the calculation sheet give me 2,938s.
Actual value is 4380uF measured so it should be faster to charge. I measure 3,2s on the scope.
Is this due to the tolerance of Cdvdt only and I should take this tolerance as margin or there is other factor from the efuse ?
The efuse is working good for our application with 4u7 but I need this information in case we need to increase the output capacitance or lower the current.
Bellow is the capture of the scope and I have attached the calculation sheet.
I also have disabled the 2nd efuse on the eval board and changed UVLO OVLO bridge divider according to our spec.
Vin = 30V 2A lab power supply
output capacitance 4800uF 100V aluminium
Regards,
Erwan
