Hello,
I'm thinking about abandoning my current DC/DC buck regulator IC and trying to find a better one in TI's porfolio as most of my parts in my product are already TI with the exception of this one. The reason I'm considering abandoning the current IC I'm using is because I'm seeing the input voltage drop severely as the regulator turns on.
I am inputting 5.7 to 6.7 volts to the regulator and expecting ~3.55V out. There is about 400-500uF of capacitance on the 3.3V rail total. The input voltage will be coming from a battery pack. The issue is that when I enable the regulator and it powers up there is a huge current draw on the battery that drops the battery voltage (which is the input voltage to the regulator) over 1 volt. This is problem because I have a voltage supervisor chip from TI monitoring the battery voltage and if it sees it hit my low threshold, say 5.7V, it shuts the device down. Unfortunately this voltage drop at power up keeps triggering my supervisor chip and locking the product out/disabling the regulator. I've attached a screenshot below showing this:
This screenshot shows the top trace which is the input voltage and the bottom trace is my 3.3V rail. The huge dip triggers my voltage supervisors and disables the 3.3V regulator. For the sake of this example I got it to work by hooking up a power supply and inputting a higher voltage than normal so the dips were still above my lower threshold and the device would stay on. Whether I use my battery or a lab supply directly connected to the regulator input I see the same thing. I've added 200uF of input capacitance to the regulator already and it hasn't helped all that much. In fact, this screenshot was taken with the 200uFs attached to V_in of the regulator.
I'm wondering if soft starting a regulator could fix this? Does anyone have any advice? Does TI have a better regulator part that would allow me to overcome this issue?
My load is only 50-100mA with maybe a 200mA pulsed requirement when I kick off an A/D converter so there isn't a large current requirement. I'm shooting for a small regulator circuit that doesn't take up much real estate and doesn't use huge inductor (basically the same thing everyone says lol) but it is a small handheld device so a small buck circuit with a small inductor is ideal.
Anyways, any advice or comments would be greatly appreciated as I'm leaning towards substantially changing my design here.
Thanks!
