Other Parts Discussed in Thread: TPS61236P
I am trying to get 3A at 5V from the TPS61236EVM-676 Evaluation Module. However, the output voltage drops substantially even under very light loads. Here are the test conditions:
Unprotected Li-Ion battery supply at 3.56V without load (20A discharge rate capability)
Battery connected to Vin and J3 GND using both pins on each jumper.
Load is a 1.8 Ohm 100W resistor (5%) connected to both pins of Vout and J8 GND
Output voltage is sagging to 2.6V (instead of 5V as expected)
Output current is 1.3A, but TPS61236EVM makes a weird, soft clicking sound approximately 20 times per second when current is being measured
Input voltage drops to 3.39V when load is attached
TPS61236EVM is enabled/started without load attached, and then load is connected
Expected to get 5V at 2.78A with that load, but it's not even close on either
Similar setup to test #1, but load is replaced with an e-load. The e-load shows 5.02V with no current, but when current is increased the voltage drops immediately. By the time the current reaches 1A or 1.5A, the e-load shows the voltage dropped to about 4.6V and eventually cuts off. E-load is added to circuit after enabling the TPS61236EVM with the jumper at J4.
I have measured the resistor at R1 to ensure it really is 0 ohm and that the constant current feature is therefore disabled. That doesn't seem to be the problem.
I suspect the cause has something to do with the soft start feature, but I'm confused as to why this doesn't work "out of the box". Do I need additional resistors or capacitors at the output to ensure the soft start is successful? The odd clicking sound is also referred to in another thread on this forum, so I know I'm not going crazy. Maybe it's cutting off and restarting over and over? If so, what would cause this to happen?
Basically, I'm looking to get a stable 5V 3A from a Li Ion battery that has more than enough discharge capacity, in theory. Any help or guidance you can offer would be greatly appreciated!!