Hi Sun,

Thanks for using the e2e forum.

You mentioned the VDD_OUT is 0V. This would also mean that the initial DC power supply has 0V, as there is a direct path from input to output in a boost topology.
Even if the device is inactive, the output voltage should follow the input voltage.
Can you double check if the power supply can support the initial current requirement and does not reach its current limit?

The schematic structure looks okay to me. The output capacitance in the picture is 0.1uF, which is very small, but you mentioned there is additional capacitance later on, so I will assume these caps are just not in this schematic picture.
An additional check would be the loop compensation to see if the device runs stable. To calculate this, feel free to use our quickstart calculation tool:
https://www.ti.com/tool/download/LM3478-88-BOOST-CALC

Best regards,
Niklas

Oh, thank you for your rapid reply.

1.Can you double check if the power supply can support the initial current requirement and does not reach its current limit?

-------- how much does the chip LM3478 need initial current when start？I probably set power supply limit current  to 1A.

2.The output capacitance in the picture is 0.1uF, which is very small, but you mentioned there is additional capacitance later on, so I will assume these caps are just not in this schematic picture.

---- you are right that these caps are just not in this schematic picture. By the way, how much the chip needs the volume of capacitor at least? 

An additional check would be the loop compensation to see if the device runs stable. To calculate this, feel free to use our quickstart calculation.

-------Firstly ,thank you again.Although I checked the calculation and filled in the content, I don't know whether the result is right or the chip can work well according to these parameters  . Secondly, i want to know if the same loop compensation parameter can support the wide input range 6-23V. ie. is it suitable to use the same resistor and capacitor value of loop compensation while the chip can work normally in so widely input range?

LM3478-88_Quickstart_Calculator_Boost_V1_0_0.xlsx

Hi Sun,

Thanks for the feedback.
The LM3478 device has an internal softstart of 4ms fixed. Therefore it is not possible to increase softstart time to reduce the inrush current upon startup.
However, another way of limiting the current is via the overcurrent protection set via the sense resistor (R1).
Right now it is set to 5mOhm, which would create a current limit of 30A. This means the power supply will break down long before the OCP is triggered by the LM3478 device.
I would strongly recommend to increase this sense resistance so it triggers earlier than the current limit of the power supply.

You mentioned earlier the device will operate with 200mA typical load. If this is the main operation mode, I would recommend to the design the application for these load conditions and select a sense resistor accordingly.

Best regards,
Niklas

hi, dear.

I love you for your high efficiency.

You mentioned earlier the device will operate with 200mA typical load. If this is the main operation mode, I would recommend to the design the application for these load conditions and select a sense resistor accordingly.

---------------I am glad to follow your suggestion

But after refreshing the value according to the quickstart calculation,  there is another problem that once powering the board, can the chip still have the ability of supplying 1.5 or 2A to charge these capacitors in a few seconds?

Thank you!