Hi,
I have the EVM for the TPS92630, I am using a buck converter before the device which is generating a 7.5Vout. The current capability of the Buck is 4A, so it should be able to drive the EVM comfortably, based on what I can see is a maximum of 1A for the 3 channels, or at least a typical. Should be enough.....
I am trying to use a signal generator to see the affect of different duty cycle and also frequency on the PWM of the chip/LED string on the Channel 1 (PWM1), tried the others as well, but PWM1 has some jumpers as well so you can disenable individual LED's which is quite a neat feature.
Reading the datasheet, it seems to imply that the PWM pins are tolerant to Vbatt (or transients), so have the signal generator set to a slow frequency (less 40Hz) 10Volts (Have tried lower as well) and varying the duty cycle.
The thing is the PWM1 seems to reset, or trigger a fault....which needs the jumper to be placed back, and turn off and on the Power Supply, I think the problem might be the frequency, duty cycle I am using, as the light don't seem to be illuminating. I know the signal generator is working as have used on Enable pin, LED illuminate beautifully...using a frequency around 30 Hz so I can see this is happening. I am wondering if the frequency is too low, and the voltage on the PWM must be lower than the Vbatt from the Switcher (7.5V) to work. Just not sure.
Is there a table (looked through datasheet) that shows what you should expect from different frequency, Duty Cycles for different dimming ? Trying to figure out how to evaluate, this feature, do you have some simple methods you could suggest for evaluation purposes ?
M,
