Shawn_Gibson
Get around INNOswitch-CH Current Sense Limit

I am designing a 5V 4Amp Charger using the Inno Switch 2025. The problem is that the
chip has a limit of 2 amps flowing from GND (PIN 15) to IS (PIN16). I have designed a splitter to
bypass 2 amps of total current. I have added a jpg of my idea.
I calculated the internal sense resistor from the datasheet saying 0.033V at 2 amps.
Will this work, or will the Innoswitch be mislead because not ALL of the secondary current
is not flowing thru it's internal sense resistor?
Thanks
Shawn

P.S. If this will not work, how would you use this part INNO2025K to
create a 5V, 4 AMP circuit.

Hello,

Thank you for considering Power Integrations for your power supply application.

For your application, if you do not need any CC function, you could put a short between the IS and GND pins of the IC and the internal current sense function will be bypassed. It does however help to keep this function as it provides overload protection.

Given that the IC will not allow more than 2A, you can connect a resistor across the IS and GND pins such that the voltage that develops between the IS and GND pins is around 33mV at the overload current level would be the right way if you need overload protection.

You can approximate the internal resistance between the IS and GND pins as 15mOhm ( 33mV for 2.2A of current). So if you add a 15mOhm resistor externally between the IS and GND pins, the CC point will be now 4.4A which is higher than your rated load of 4A and should provide you overload protection. If you need any change in this further, you can adjust the external resistor value.

Hope this helps.

Best Regards

Sarek,
Thank you for your reply. I will try the 15mOhm resistor across GND and IS.
Sincerely,
Shawn