Hi, I have used TPS40200 switcher IC for my power supply requirement. Following is the configuration:
Vinput = 7.5V to 6.0V
Vout = 5V @ 150mA Max
With the TPS output of 5V, I am driving a transformer based isolated power supply section for analog section, which is rated as below: +/-5V analog @ 130mA max. The supply to analog section is controlled through digital section, which enables the supply to analog section at desired and fixed interval.
The problem I have observed is: The moment i turn on the supply to analog section, TPS40200 goes into shut down mode permamnently. This happens only if the load is connected on +/-5V analog section. If no load connected, it works well. I have tried with a load of as low as 1mA. I have checked the current through the transformer during startup, it is shooting up for about 3-5uSec duration.
I have tried with replacing the current sense resistor of 20mOhm at present to a short, but the result was still the same.
Please suggest a possible solution to this problem.
I have tried a solution, and it is as below in the SCH. I would also like to know the consequences of this option, and any other suggestion possible.
In the above picture, R76 before L2 is added to limit the current to the supply section. Though it is dissipative, but it still gives the desired output, at the cost of efficiency. By doing so, my board works well. Please suggest pros and cons of using such configuration.
Also, please tell me, what will be the difference if I put the resistor before L2 inductor/ after L2 and before capacitor C2/ after C2 and C40, and before the power supply plane and feedback to the switcher IC?
Awaiting your response at the earliest.
Thanks,
Kapil