Hi team,
When I set PP3 as a power source on 988DKEVM, the system couldn't work.
When I set PP1 as a power source on 988DKEVM, the system could work.
The reason is PP3 and PP4 only could be power sink in 988DKEVM?
Jason
Hi Alan,
I try to set up as external power path, but it can't work.
If you open the the PP3 switch as output and change PP1 source to PP3, the circuit couldn't work.
Could you please double check this, thanks.
Jason
Hi Jason,
Are you brining 20V into the barrel jack? from what I can see, you are looking to have the following supported:
5V, 3A
9V, 3A
15V, 3A,
20V, 5A
Since the EVM only support up to 3A using the internal power path, you are looking to use the external power path.
If I am correct with the above, I would setup PP1 Switch Config to Source Only, then also setup the PDO 1,2,and 3 (5V, 9V, and 15V) to use PP1 (since they only need up to 3A, and use PP3 for PDO 4 (20V,5A). The issue with the way you have it is that if you try to put 20V on the barrel jack and set all PDOs to use the external power path, there will always be 20V on the Vbus, which will not work. This is because you will be disabling the variable regulator that is set up to work with the internal power paths.
Also, I see that you have Bank 1 set up. not sure what this is for and does not look like it is needed.
Regards,
Alan
Hi Alan,
I don't understand, according to datasheet TPS65988DK internal path can support up to 5A. why you said only 3A?
I don't know why I need to use internal path for PDO1~3, and external PDO path for PDO4. if I only tune the PDO 4 to 20V/3A, it doesn't work too.
Do you try the FW you provide to me on EVM board and it can work?
for my customer application, they only need to use external path, they don't want to use internal.
Jason
Hi Jason,
yes, the datasheet for the TPS65988DK sows the internal power path is 5A. The EVM has a limit of 3A. that is why I was suggesting using the internal up to 3A, then for 20V, 5A, setup the external. anyway, as you want your 4 PDOs set up for the external power path, and you indicated you want to use the variable output regulator that is on the EVM, this is what I suggest you do:
1. when you set up the external power path, the PA_PP_EXT_Enable trace enables the external power path, but it also disables the variable output regulators. You will need to keep this from happening. For PA_PP_EXT (PP3) you will need to remove Q17. This will keep the regulator on.
2. The external power path, by default, is set up to be sink only. You will need to remove Q3, which will eliminate the reverse current protection circuit, but still allow the external power path to be enabled.
3. Jumper J11 pin 1 to pin 5 to allow the output of the variable regulator to go to the external power path.
4. if you need PB_PP_EXT (PP4) you will need to remove the appropriate parts for that path.
