BQ25790: Question about BQ25790

Hi Jimmy,

The schematic looks okay.  I need more info What is the issue?  Is the charger crashing the USB bus at power up?  If so, then using the ILIM_HIZ resistor divider to lower input current limit.  Is the charger's D+/D- communication for the first 2 seconds after power up causing issues for other D+/D- comms?  If so, then delay D+/D- comms from other devices until after the first 2 seconds. 

Regards,

Jeff

Hi Jeff：

1. From which register to identify whether there is external USB charging;

2. The charging chip BQ25790 cannot recognize the type of charger;

Hi Jeff：

Two questions need your help:

1. How to use 9V HVDC / 12 HVDC mode? Whether the chip automatically detects the voltage to set or requires CPU to set;

2. Function of external ship FET: in the case of ship mode, which circuits work and which do not work.

Hi Jeff：

Thank you. Now we find another problem, that is, although the charging current and input current I set are both 3a, the actual current measured from the charging line is only about 1.3A.

What is the possible reason for this?

Hi Jeff:

Yes, the bit default is 1. Now I set it to 0, and the current can be increased to about 1.9a, but it still cannot reach the 3A output of the charger.

I also set the maximum charging current and input current of 3a in the register.

Is there any other place to control?

Five kinds of chargers and three charging wires are tried. It is found that different combinations have different results. Some combinations will fail to recognize the charger type. Even if the DCP charger type is recognized, the charging current will be different. Some can reach 2.8A, and some are only 1.5A.

There is a USB cable inserted into the computer, which cannot be recognized as a U disk. Five kinds of charging heads are recognized as SDP, with a 500mA charging current.

Hi Jimmy,

What do the status and fault registers report?  Is the charger in VINDPM, meaning the input voltage is dipping to the VINDPM threshold and then reducing input current?  Is the charger in thermal regulation?  

Regards,

Jeff

Hi Jeff：

Here are the values of registers printed by two different chargers.

There were some problems before. Customer use BQ24179

Charger A:

-ibus_adc=1271000

-get ichg_curr=3000000

-input current limit=3000000

-input_v_lim=0x24

-chrg_stat_0=0x4f

-chrg_stat_1=0x67

-chrg_stat_2=0x1

-chrg_stat_3=0x0

-chrg_stat_4=0x0

-chrg_flag_0=0x0

-chrg_flag_1=0x0

-chrg_flag_2=0x0

-chrg_flag_3=0x0

-chrg_ctrl_0=0xa2

-chrg_ctrl_0=0xa2

-chrg_ctrl_1=0x80

-chrg_ctrl_2=0x40

-chrg_ctrl_3=0x12

-chrg_ctrl_4=0x0

-chrg_ctrl_5=0x14

-fault_status_0=0x0

-fault_status_1=0x0

-fault_flag_0=0x0

-fault_flag_1=0x0

-ibat_adc=484000

-ibus_adc=1281000

Charger B

get ichg_curr=3000000

input current limit=3000000

input_v_lim=0x24

chrg_stat_0=0x4f

chrg_stat_1=0x67

chrg_stat_2=0x1

chrg_stat_3=0x0

chrg_stat_4=0x0

chrg_flag_0=0x0

chrg_flag_1=0x0

chrg_flag_2=0x0

chrg_flag_3=0x0

chrg_ctrl_0=0xa2

chrg_ctrl_0=0xa2

chrg_ctrl_1=0x80

chrg_ctrl_2=0x40

chrg_ctrl_3=0x12

chrg_ctrl_4=0x0

chrg_ctrl_5=0x14

fault_status_0=0x0

fault_status_1=0x0

fault_flag_0=0x0

fault_flag_1=0x0

ibat_adc=1016000

ibus_adc=2672000

Hi Jimmy,

Both chargers are reporting VINDPM, which means the input current is pulling the voltage at VBUS down to the VINDPM threshold.  If input_v_ilim above =0x24 is that threshold, then the input voltage is being pulled down to 3.6V.  Is the connection from power supply to charger, highly resistive?

Regards,

Jeff