LM5069: Startup Failure

Isao Takigasaki

Part Number: LM5069

My customer found start-up failure that VOUT is not reached to target voltage.
Could you provide the cause which can be expected?

Vin=24V and current limit is 12A. The schematic and waveforms are shown in below.

Yellow(Ch1) : VIN(Pin#2)
Blue(Ch2) : OUT(pin#9)
Pink(Ch3) : PGD(Pin#8)
Green(Ch4) : Load Current

The followings are waveform in failure case and the case to succeed to start up.

Yellow(Ch1) : VIN(Pin#2)
Blue(Ch2) : OUT(pin#9)
Pink(Ch3) : TIMER(Pin#6)
Green(Ch4) : GATE(Pin#10)

0 Rakesh over 5 years ago

Hi Isao,

Can you please share filled-up design sheet for review. It is available under the LM5069 product folder.

Can you also capture the above test waveforms long with the input current to check whether the device is under overload fault or not.?

Best Regards, Rakesh

0 Isao Takigasaki over 5 years ago in reply to Rakesh

Hi,

PLS see the spread sheet to be filled up.

The customer is checking the overload fault.

Best Regards, Taki

0 Rakesh over 5 years ago in reply to Isao Takigasaki

Hi Isao,

Thanks for the design sheet. The timer cap needs to be reduced to improve the FET SOA margin. Please find the attached modified design sheet.

Is there any other load during startup other than Cout. Looking forward for the test waveform.

Best Regards, Rakesh

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