Can't configure the TCPP01-M12 to 2.5W (500mA)

[POLessard]

Hi,

I have follow the DS12900 Rev 7 Figure 21 (Schematic example for USB Type-C at 2.5W with TCPP01-M12) and still can draw more that 1.5A from USB PD source, the voltage seen on CC1 is close to 1.4V (which corresponds to 3A capability). Not sure what is wrong/missing in the circuit;

 

[Peter BENSCH]

The 1.4V on CC1 is actually consistent with a 3A Type-C advertisement, so that part does not look wrong.

My main suggestion is to check the USB-PD negotiation and the sink configuration, because the TCPP01-M12 does not limit the load current to 1.5A by itself. It mainly provides CC protection, VBUS OVP, and gate control.

You should check:

• requested PDO/current in firmware
• /DB pin state
• VCC supply
• whether there is any separate current-limit stage on VBUS

So the likely issue is not the schematic in fig. 21, but rather the system current limiting / PD contract configuration.

Regards
/Peter