Dear EngineerZone comunity,
I have problem with low power DC-DC convertor LT8361.
I use schematic - "450kHz, 5V to 60V Input, 80V Boost Converter" page23 for the positive 5V to 96V converter and
schematic - "450kHz, 4.5V to 12V Input, –150V Output, Automotive LiDAR APD Bias Power Supply" page28 for the negative 5V to -96V converter.
Both schematics give 96V +/- 1% with loading (4.7K) and without.
The problem is current consumption without loading.
Positive voltage converter usually has few microamps and run 10 - 50 kHz depend to inductor value,
but sometimes after power on it has 20mA and run 450 kHz. After connect/disconnect load it return to microamps.
Negative voltage convertor always has 20mA and 450kH (instead of microamps and few kHz in LTspice).
What I need change in schematic for correct start with microamps and lower frequency?
I can send more oscilloscope pictures if necessary.
Thank in advance
This is inductor voltage for the positive voltage convertor.
Please post your specs. it appears you are changing the output of both converters to +/- 96V. What is the load current you need?
page23 R2=16.9K and page28 R2=8.45K
I need power 4 ICs HV2701 with Vpp and Vnn current 5.5mA, so I need 22mA.
Switch is changing 5% of time and average current less then 2mA.
I have not problem with maximum current, but I want to understand how LT8631 work.
It looks for me LT8631 sometimes work not in the "Burst mode"
R2 = 16.9K and 8.45K
I need 22mA load current max and 2mA average
I need max current 22mA and 2mA average current
Make sure the Sync pin is grounded, for Burst mode operation.
Your inductance value for both converters should be set at about 4.7uH in order to maintain the switch current below 2A at 22mA load, with 5V input.
Then, when the load is removed, the frequency should slow down for both converters, but a little more for the negative, since it has lower switch voltage than the positive.