ben5243
Member level 3
Hi,
I'm working on a battery charger using an LTC4020 controller and one of the inputs allows scaling of the charging current.
The RNG/SS pin is described as follows:
Later in the datasheet, they recommend this method for controlling the voltage on the pin from an active servo capable of only sinking current:
I have done what's shows in the schematic but it does not work correctly. Here is my PCB schematic:
The RNG signal is from a DAC and outputs the correct voltage (0-1V) When it is set to 1.0V, the inverting input of the op-amp (Pin 4) has 1.0V, but the non-inverting input (and the RNG/SS pin) have about 0.2V
Is there is a reason this circuit is not working for me? When I remove R34, the charger works correctly at full current, but I need to throttle the current down.
I'm working on a battery charger using an LTC4020 controller and one of the inputs allows scaling of the charging current.
The RNG/SS pin is described as follows:
Later in the datasheet, they recommend this method for controlling the voltage on the pin from an active servo capable of only sinking current:
I have done what's shows in the schematic but it does not work correctly. Here is my PCB schematic:
The RNG signal is from a DAC and outputs the correct voltage (0-1V) When it is set to 1.0V, the inverting input of the op-amp (Pin 4) has 1.0V, but the non-inverting input (and the RNG/SS pin) have about 0.2V
Is there is a reason this circuit is not working for me? When I remove R34, the charger works correctly at full current, but I need to throttle the current down.