LTC4125 - DC2770A-B-KIT - PTH1

Hi,

I am using the DC2770A-B evaluation kit with the aim of recharging coin batteries with charging currents at 10 mA or 25 mA and a distance between the TX and RX coils of 10 mm.

The transmitter is set to guarantee optimum power search, but for the purpose of my work I would like to disable it. For this reason, I applied an input voltage of 1 V to IMON and I applied an adjustable voltage (0 -1) V with an r pull-up on pin PTH1, in order to manually manage the voltage on the coil.

Please let feel free to suggest and advise me, and let me know if you think that these changes are reasonable.

Also, from the datasheet I don't understand how the PTH1 pin works either with or without an applied voltage. In the tests carried out forcing this operation, the power is transmitted correctly. The problem is that the LED indicating the status of the transmitter is off as if it indicated a fault condition. I don't understand why and which fault condition is activated. NTC also does not return voltage (I think it is due to transistor Q1, activating when I apply a voltage of 1V on IMON and NTC goes to ground).

Since I don't need to use optimum power search, I wanted to ask you how I could modify the circuit further to take up as little space as possible. For example if there are components that can be removed. The features that interest me of the LTC4125 integrated are: the AutoResonant driver, Pulse Width Threshold, NTC and the Resonance Feedback Voltage.

I am attaching the circuit diagram of the transmitter with the proposed modification.

Thanks,

Andrea