asus rog strix x470,IR 3555M pin out

[Davemack69]

Hi
I'm new to forum.
I've got a faulty vrm section on a asus rog strix x470 motherboard. The vrm controller is a 6+2, on boot I'm only getting a output on the soc section of the vrm so only 2 phases.
I've been trying to find pin out of a IR3555 twin mosfet.
I've found pinouts for ir3553 40A but apparently the ir 3555 is different.
Hopefully this will help me figure out why I have no output on the 6 phase part of vrm.
Thanks in advance.
Dave.

[Bozog]

Re: asus rog strix x470,IR 3555M pin out

The IR35201 datasheets shows a typical application with IR3555 powerstages, doesn't help with the pinout I know but I'm going to guess you can use the IR3553 datasheet since I have seen boards with a pad layout for the full size IR3555 with only an IR3553 size chip fitted.

[Bozog]

Re: asus rog strix x470,IR 3555M pin out

Like this

[Davemack69]

Re: asus rog strix x470,IR 3555M pin out

From the looks of what's on the board and taking voltage measurements the pin out is different.
The vcc ie pin 3 on ir3553 is definitely not vcc on the ir3555m.
I think pin 3 on ir3555 is current sense.
Apparently the controller looks at the pmw pin on the ir3555m and if there's voltage there it enables the output.
I'm thinking maybe the 6 phase mosfets have no power or there's a output being held low so they are not enabled.
I've found a schematic of typical use of ir3555m and it's different from ir3553.

[Davemack69]

Re: asus rog strix x470,IR 3555M pin out

https://imgur.com/a/Ga3AyBp

[Bozog]

Re: asus rog strix x470,IR 3555M pin out

MSI GTX 1080 Ti Lightning Z uses IR3555, schematic and board photo with pin numbers available.

[Davemack69]

Re: asus rog strix x470,IR 3555M pin out

Thank you I can see pin 3 is not vcc as on 3553.
I'll continue my efforts tonight

[Davemack69]

Re: asus rog strix x470,IR 3555M pin out

Little update, I've got vcc on all mosfets.
I suppose I need to check Isen, Vren, Tsen now see if all of these voltages are OK
The ir35201 splits the phases 6+2