LM5170EVM-BIDIR: LM5170 boost mode issue

Hi Eddie,

Thank you for posting.  It's better if you send me a photo picture of board so I can quickly check if the jumper is used correctly.  The list is harder to follow.

J14, J15, J19 are not needed, and J31 is not clear: where does the 5V come from?  The EVM's 5V rail or external 5V?  

Anyway, I think you did not follow the User Guide nor read the datasheet circuit breaker section.  The circuit breaker only operates when the 48V-port has a voltage at least 10V higher than the 12V-port voltage. You just have a load, then the breaker cannot be turned on.  Also, in the User Guide section 3.2, the second step is:

2. Turn on the HV-PS power supply and HV-E-Load.

This HV_PS is to turn on the circuit breaker at the beginning. Once the boost operates, this supply can be removed.  You do not have a supply there, so this won't work.

In order to run the EVM as a regular boost converter, you need to do the following: 

1. Solder a copper strip (able to conductor at least 60A) to the two exposed pads beside D3 on the back side, to bypass the circuit breaker. 

2. Solder an 100k resistor to R4 (below J1).  This is to provide an onboard UVLO control.  Once the input is supplied, the circuit will automatically start.

3. Remove all jumper caps, then re-apply to close the following jumpers.

Either J1 (2,3) or J1 (1,2) should work for boost mode.

J3 (1,2)  To disable the fault detection because it if 48V-port is just a load.

J4 (1,2)

J5 (2,3)

Either J21 (1,2), or J21(2,3), both should work for boost mode.

Either J25 (1,2),  or J30 (1,2), but not both, to enable the CH-2

J28 (2,3)

J29 (1,2)

J34 (1,2)

J35 (1,2)

J36 (1,2)

J37 (1,2)

If you want to run buck, change to the following jumper positions: J1 (1,2);  J21 (1,2); J28 (1,2). 

Hope this clarifies.

Thanks,

Youhao