LM5175: HDRV2 no working

Hello Josef,

Please share your schematic.

How many boards did you check? Did you try to exchange the IC?

N413.09PB1 Dokumentace (1).PDF

Hello, yes, I testing more pieces - all is same. Now, I connect MODE pin to VCC and HDRV2 working good from low and midle charging current, but no work for full charging current. On SS PIN is still 1.2V. 

Hello Josef,

Thank you very much for the schematic and layout.

Please share input and output voltage range as well as the output current range. Then I can check the schematic in more detail.

Input voltage - car power net, 12 or 24V. Output voltage 9S battery - 18-36V. Output current - 2A.

Hello Josef,

Ok, MODE set to high means that the device always works in CCM.

As the converter seem not to operate in DCM, I wonder if the FB voltage gets too high because of the external circuitry you have applied there. Please measure the current you are getting compared to the current you are setting. As well measure the FB voltage (if possible with a scope).

Does your HW-reg signal account for the FB inaccuracy of +/- 1.5%?

Hello Brigitte,

in PDF is measuremnt. FB accuracy is ok for this application. 

J.

N413_HDRV2_measurement_200807.pdf

Hello, if I using mosfet: PSMN012-60YS (in my original circuit) is situacion better HDRV2 work. But i can using BSC039N06NS (better EMI) and for this transitor is this problem HDRV2 not work..

Josef

Hello Josef,

What is the difference between the 2 pictures in your pdf, other than the voltage on HDRV2?

Would it be possible that you measure the 2 switch nodes?

Please check what happens if you replace the gate resistors with 0 ohm. It is possible that the higher gate charge of the BSC039N06NS needs higher current to get on. Why do you need such high resistance gate resistors. We do not recommend more than some ohm.

Hello Brigitte!

Diffference between pictures in pdf is output current value (red line). HDRV2 work good for output current set 0 to cca. 1,4A and for higgest current HDRV2 not work. PGOOD pin is in HIGH all time.

L1-L4 are not resistors - they are ferrite beads - for better EMI, they have DC resistance very low.

Measurement is attached Green line - HDRV2 Blue line - LDRV2 Red line - output current. First picture with PSMN and second picture with BSC.

I mean that if problem is wiht FB line PGOOD pin is set to LOW - i have PGOOD pin set to HIGH for all time.

Josef

HDRV2_LDRV2_measurement_200811.pdf

Hello Josef,

The signals on L1 to L4 are not DC, but switching signals which have high frequency range, so please check if the problem is gone if you replace the beads with 0R resistors.

Please measure the switch nodes.

Do you mean HDRV2 is not working because it is not going to 40V?

Yes signal on L1 and L4 is cca. 300kHz - in prototype i have now ferrite beads: datasheet.octopart.com/MI1206K310R-10-Laird-datasheet-14357335.pdf
and imedance on 300kHz is lower than one ohm.. But if I shorting ferrite beads on LDRV2 -> HDRV2 work good in full range of output current.

But work good only in CCM mode (mode pin connect to VCC) and not work in DCM mode.

Yeas i mean HDRV2 not work because on HDRV2 is only outpout voltage - high side mosfet can not be switch on and diode D5 heating.

Josef

Hello Josef,

What happens if you are shorting all ferrite beads?

Good moorning Brigitte,

If I shorting all ferrite beads is situacion same - work normal in CCM mode and HDRV2 not work in DCM mode. But this is not problem for me - CCM mode is ok for this aplication. Have you any idea why HDRV2 dont work with ferrite beads on LDRV2? This is important for me - ferrite beads has good efect on radiated EMI and our customer need FCC15 certification, without ferrite beads this will be hard work for me. :-)

Josef