LM5069EVM-627: LM5069EVM-627

Francisco Tamez

Part Number: LM5069EVM-627
Other Parts Discussed in Thread: LM5069,

Hi,

I am testing the circuit for the LM5069 using the eval board: LM5069EVM-627. Since I require 40V outputs instead, I replaced the OVLO and UVLO resistors R1-R4 to operate on the 40V range. I used the TI XLS calculator (Option B) for that purpose, which seem it is working under no load when I measure the output using a DVM. Due to the spec, the output is clamped to 30V from what I can measure, so my question is, how do I remove this restriction to have a 40V output without affecting the circuit operation? Also, I notice that if I load the clamped output (while input is 40V) by connecting a 30 Ohm load, the voltage goes to 0V. However, with only the Vout capacitors installed on the board as the only load, I can measure the clamped output of 30V. Why does that happen?

Thanks

Francisco Tamez

over 7 years ago

0 Brian Daugherty over 7 years ago

TI__Expert 5940 points

Francisco,

Remove Z2, the 33v gate zener. This clamps Vout to 33v - Vplateau or ~ 30V. If you use 40v and have a load, Vds will be 10v and the power limit engine will engage and time out the C8, shutting down. If you still want a clamp, use a zener > 43v.

Brian

0 Francisco Tamez over 7 years ago in reply to Brian Daugherty

Prodigy 60 points

Hi Brian. Thanks for your prompt response. Let me try it before I close this issue. Have a nice weekend.

0 Francisco Tamez over 7 years ago in reply to Brian Daugherty

Prodigy 60 points

Good Morning Brian,

I removed Z2, but no voltage at the output. DO I need the zener (>43V) at the gate to make the circuit operational. The development board has D2 and R6 installed, however, the schematic drawing shows them as optional. Do I also remove them?

Thanks

Francisco

Power management

Power management forum

LM5069EVM-627: LM5069EVM-627