TPS55289Q1EVM: Output auto-disables when switching large load current in boost mode.

Tool/software:

Hello, 

I am encountering some issues when trying to test the TPS55289Q1EVM eval board. I have connected to the board using the USB2ANY adapter and am controlling it using the TPS55289-Q1 gui as specified in the user manual. The input is attached to an adjustable bench power supply, and the leads are attached to a load resistor. 

So far, the board works with a light load (100mW) across a range of inputs/outputs. The problem is that with 5V input, 20V output, and 47ohm dummy load the gui automatically disables the output shortly after I enable it. I believe this scenario is within the safe operating regions of the chip, and should not be related to overcurrent or thermal shutdown issues. A similar problem occurs with other boost conversions like 9-20 and 12-20: with the 47ohm load, the gui disables output when shortly after I enable it.

For all of these scenarios, the output stays enabled when I set the output to a lower voltage (15V). I am able to then gradually increase the output voltage in the GUI until it reaches 20V. However, the chip shuts down if my increase is not gradual enough. 

Some scope readings: 

1. output: 5V input to 17V output set directly on gui. 


2. output voltage: 5V input to 16V output (note that output stays enabled)


3. 5V in. After being on for some time at a 18V, I increased the output voltage to 19V. The output remained enabled


4. 5V in. After being on for some time at 19.5V, I increased the output voltage to 20V. The output disabled shortly after. 

Is there an explanation for this behavior? Any help would be greatly appreciated. 
Thank you!