BQ24780S: can not charge

Tommy Tzeng

Part Number: BQ24780S

Hi Sir,

When the system power load increases, the Charger IC cannot be charged
The conditions are as follows
Adapter: 19V, 7.89A

when Rac seting 0.01Ohm and on Rac voltage as below:
1. At 40% system loading, 37.8mV, the battery can be charged 0.5A
2. At 60% system loading, 45mV, the battery can be charged 0.5A
3. At 100% system loading, 58.1mV, the battery cannot be charged

there any errors in the setting of the attached theschematic? Is the schematic correct? please kindly let us learn from you and suggestion to us.

MG4U_DVT_DC BOARD_0518-1430.pdf

over 4 years ago

0 Tiger Zhou over 4 years ago

TI__Mastermind 32595 points

Hi, Tommy,

There is an input current register 0x3F, its default value is 4.096A. From schematic, the ILIM pin is limit to 3.05A. You may run into input current limit, thus limiting your charge current.

Datasheet 7.6.11, "The total input current, from a wall cube or other DC source, is the sum of the system supply current and the
current required by the charger. When the input current exceeds the set input current limit, the bq24780S device
decreases the charge current to provide priority to system load. As the system current rises, the available charge
current drops linearly to 0."

0 James Liu2 over 4 years ago in reply to Tiger Zhou

Prodigy 50 points

Hi Tiger:

I am ESVS James Liu

The schematic is my company project

The BQ24780S register setting

0x12H 8108

0x3BH C210

0x38H 0384

0x37H 1A40

0x3CH 4A54

0x3DH 8120

0x3AH 0020

0x14H 0200

0x15H 41A0

0x39H 2600

0x3FH 1E80 7808mA

The Rac is 58.1mV , So input current is 5.81A < 7.8A

Can you help me?

0 Tiger Zhou over 4 years ago in reply to James Liu2

TI__Mastermind 32595 points

Hi, James,

Please check your battery voltage as well. Does this happen at fully-charged battery or low-charged battery? If fully-charged, the charge current may terminate when max charge voltage is reached.