TPS25750EVM: Can TPS25750EVM sink more than 5A?

Hi Chuck-san,

Thank you for your support.
My customer tried sinking current from PPHV (20V) then he can sink up to 3A.
He uses 60W PD adapter, so it is a reasonable result for TPS25750.

It seems BQ25731 limits the sink current from SYS_PWR.
Do you know how to adjust BQ25731 to sink more than 5A from SYS_PWR?

Best Regards,
Yaita

Hi Yaita-san,

Chuck is out of office until Wednesday. He will follow up with you later this week.

Thanks,

Emma

Hi Emma-san,

OK. I will wait for the feedback.

Best Regards,
Yaita

Yaita,

I am going to pass this question onto the charger team.  They know this part better than I do.

Chuck

Yaita,

I did notice that you have the master port of the TPS25750 connected to the MCU.  The TPS 25750 does not support multi-master busses, so this may be an issue if you plan to reprogram the BQ25731 with the MCU.

Hi Yaita-san,

We are passing this question to the battery charger team to follow up with you. 

Thanks,

Emma

BQ25731 can sink more than 5A current, just set the IIN_HOST register for input current limit. With 5mohm current sense, the max input current can reach 10A max.

Hi 

BQ25731 datasheet shows the default value of IIN_HOST is 0010_0000 (I2C address=0Fh), it is 3200mA input current.
I believe 3200mA is sufficient because the input voltage of BQ25731 is 20V in this case.
BQ25731 operates buck converter as the following.
20V -> BQ25731 -> 4.2V(SYS_PWR)

Do you know why BQ25731 limits the sink current ~5A from SYS_PWR (4.2V) with TPS25750EVM?

Best Regards,
Yaita

Hi Tiger-san,

My customer set real Li-ion battery as you referred however he couldn't charge the battery more than 4.5A.



Do you know why the charge current is limited?

Best Regards,
Yaita

Try to disable BQ25731 IINDPM by setting ChargeOption1(0x00) bit 1=0. 

Hi Tiger-san,

Could you tell me how to disable BQ25731 IINDPM by setting ChargeOption1(0x00) bit 1=0 with TPS25750 Application Customization Tool?
Regarding TPS25750EVM, I believe TPS25750 Application Customization Tool manages the BQ25731.

This inquiry is not for BQ25731 only but TPS25750EVM with TPS25750 Application Customization Tool.

Best Regards,
Yaita

The USB PD spec does not allow the system to draw more than 5A from the type C connector. Could you isolate the BQ25731 and use BQStudio/EV2400 to access to the I2C bus?

Hi Tiger-san,

Yes, I understand "USB PD spec does not allow the system to draw more than 5A from the type C connector".
In this situation, BQ25731 operates buck converter as the following so it isn't required to draw more than 5A from the type-C connector.
It seems BQ25731 limits the sink current ~5A from SYS_PWR (4.2V).
20V -> BQ25731 -> 4.2V(SYS_PWR)

My customer has TPS25750EVM only so he can't isolate BQ25731.
I would like to know how to sink more than 5A from SYS_PWR with TPS25750 Application Customization Tool.
In other words, I would like to know if TPS25750EVM supports the requirement above.

Best Regards,
Yaita

Sorry, I am new to TPS25750EVM. Maybe, Chuck can comment?

Chuck-san,

Could you support the issue?
The inquiry hasn't been resolved for about one month and my customer is waiting for TI engineer's opinion.

Please let me know if you need additional information or has something unclear.

Best Regards,
Yaita

Chuck-san,

I understand "USB PD spec does not allow the system to draw more than 5A from the type C connector".
In this situation, BQ25731 operates buck converter as the following so it isn't required to draw more than 5A from the type-C connector.
20V -> BQ25731 -> 4.2V(SYS_PWR)

Could you check if TPS25750EVM can sink more than 5A from SYS_PWR?
In other words, could you check if TPS25750EVM can charge more than 5A?

Best Regards,
Yaita

Chuck-san,

Does TI have evaluated if TPS25750EVM can sink more than 5A when battery charging voltage is 4.2V in the application configuration tool?
If so, could you please share the result?

My customer hasn't achieved yet so we need TI support to solve this problem.
I posted the content in the first post of this thread. 

Best Regards,
Yaita

Yaita-san,

I am going to transfer this support over to the TPS25731 team because the issue appears to relate to the Charger that I am not an expert at supporting.

Chuch-san,

Is there any possibility of solving this problem?
I want TI to check if TPS25750EVM can sink more than 5A from SYS_PWR when battery charging voltage is 4.2V and want TI to suggest a workaround.
If it isn't possible, please let me know.
I have to inform my customer of the contents.

Best Regards,
Yaita

Chuck-san,

Is there any update?

Best Regards,
Yaita

Yaita,

You can update the charge current register for the BQ25831 to change the charge current after the PDO has been negotiated by the TPS25750

Chuck-san,

My customer directly read ChargeCurrent register of BQ25731 when he set battery charging current=7.04A with TPS25750EVM, then he confirmed the register value is the following.
03h=0d
02h=c0
=> 7.04A (4096mA+2048mA+512mA+256mA+128mA)



So, the issue isn't related to ChargeCurrent register of BQ25731 because it is set correctly.
Could you look into the issue again?

Best Regards,
Yaita

Chuck-san,

Could you please continue to investigate the cause of TPS25750EVM can't sink more than 5A?
My customer strongly desires it and wants to know the issue belongs to hardware or software.
From the beginning, they have a plan to develop their power bank application (charging ~10A for 1 cell Li-ion battery ) with TPS25750 and BQ25731 so he bought TPS25750EVM.
Regarding charge termination, TPS25750EVM doesn't support the function however he considers their own solution now.

They have no choice but to stop their development if they can't know the root cause of the issue.

Best Regards,
Yaita

Yaita,

The EVM has active circuitry included that will prevent the charger from Sinking more than 5A to be compliant to type C/PD.

The BQ25231 EVM can be used to sink up to 16A of current for reference.

Chuck

Chuck-san,

>The EVM has active circuitry included that will prevent the charger from Sinking more than 5A to be compliant to type C/PD.
Does it belong to hardware of TPS25750EVM?
Could you let me know the detail about it?

Best Regards,
Yaita

Yaita,

I need to draw out this system in more detail and give this some thought.  It may be possible to override the charge current VIA I2C as long as the type C port is not utalized.

I will get back to you with a proposal early next week.  This is a complex option that will involve a fair amount of work with the TYPS25750 Host interface to use.

Chuck-san,

Thank you for your continuous support.
I will wait for your feedback.

Best Regards,
Yaita

Yaita,

Can you detail the changes that have been made to the EVM for your experiment?

I see that come connectors and the 12V buck have been changed in the picture, but I want to make sure that I know where you are starting from

Chuck-san,

The changes are the following.

- removed the jumper J5
- removed D2, D3 then shorted the line
- removed the jumper J1 and external 3.3V is supplied to VIN_3V3
- changed CELL_BATPRESZ resistors (R27, R28) to meet the following


If you need additional information or has something unclear, please let me know.

Best Regards,
Yaita

Yaita,

This is clear.  The modifications should allow you to charge, but I need to review the schematic completely with the charger team to be sure.

Chuck

Chuck-san,

I appreciate your continuous support.
I will wait for your team's feedback.

Best Regards,
Yaita

Yaita,

From what I can see in the schematic, they should be able to update the input ILIM register of the BQ25731 and change the supported charging current.  If this is not working, then I will have to reach out to our charger team for further explanation.

Regards,

Chuck

Chuck-san,

My customer increased the value of IIN_HOST Register (0F/0Eh) as the following however it shows no improvement.
2d00(=4500mA) -> 3f00(=6300mA)

He also confirmed ChargerStatus Register (21/20h) and it shows "8200" when the sink current is restricted.
Note) He confirmed the register shows "8400" when e-load sink lower current than 4.5A.
Do you know what the Reserved bit indicates?



Best Regards,
Yaita

Yaita,

I will discuss this with the BQ charger team and see what they suggest.

Chuck-san,

My customer could increase the sink current from 4.6A to 5.4A when he changed ChargeOption0 Register (0x01) from 0x05 to 0x07.
The changed bit is PWM_FREQ.



Why 800kHz is set as default although L=4.7uH in TPS25750EVM?
BQ25731 datasheet shows 400kHz is recommended with L=4.7uH.
In any case, he hasn't been able to get the expected sink current yet.
Do you have any updates?

Best Regards,
Yaita

Yaita,

I will look into the register setting.  It was provided by the BQ charger team.  We are reviewing these configurations for the next GUI update, so it may be possible to change them depending on what the charger team says.

We are working on debugging a potential issue that would cause the TPS25750 to update the charge current register at in appropriate times.  I expect to have some results by Wednesday next week.

Regards,

Chuck

Hi Chuck-san,

Please tell me if you have any updates.

Best regards,
Yaita

Yaita-san,

Has the customer checked the VINDPM register?  I don't have the spec in front of me, but if it is set incorrectly, it may cause the issue that you are seeing.

Regards,

Chuck

Chuck-san,

My customer confirmed the following value for VINDPM Register(0B/0Ah).
0Bh: 02h
0Ah: 00h

Is the value set incorrectly?

Best Regards,
Yaita

Yaita,

For the BQ25731, the way that we are about to recommend calculating VINDPM is as follows:

VINDPM = (975/1000)*VSINK_PDO – 3200 

For your case, VSINK_PDO is the input voltage that you are applying to the charger.  All values are in mV.

Regards,

Chuck

Chuck-san,

My customer changed VINDPM Register(0B/0Ah) as the following however the result is the same, it shows no improvement.
0Bh: 02h -> 3F
0Ah: 00h -> C0
The input voltage that is applied to BQ25731 is 20000mV so he set above (=16320mV).
Note) He also changed ChargeOption0 Register (01h) 0x05 to 0x07 however the result is the same too.

I would like to know the background of changing VINDPM Register.
The function of VINDPM Register is the following but the input voltage doesn't show dropping from 20V. 
-----------------------------------------------
If the input voltage drops more than the InputVoltage register allows, the device enters VINDPM and reduces the charge current.
-----------------------------------------------

Best Regards,
Yaita

Yaita,

I am temporarily passing this thread over to the BQ25731 Apps team.  I am out of my depth on this specific issue.

Chuck-san,

I will wait for your team's feedback.

Best Regards,
Yaita

Set VINDPM to a low voltage threshold, this effectively disabled the VINDPM.

If the input voltage did not drop, it is not related to VINDPM. 

I am confused.
My customer confirmed the following value for VINDPM Register(0B/0Ah) from the beginning. I believe it is set to the low voltage threshold as you said.
0Bh: 02h
0Ah: 00h

We changed the value because I just heard VINDPM is recommended to be set to follow the calculation.
VINDPM = (975/1000)*VSINK_PDO – 3200