BQ25703A: The heat output of the BQ25703A BATFET increases as the system load current increases.

Huigen Jiang

Part Number: BQ25703A

Hi TI,

I use TI's BQ25703A chip to charge the lithium iron battery (12V/5Ah).

When the main power is turned off, the lithium iron battery (12V/5Ah) is discharged through the BATFET (P-MOSFET).

As the system load current increases to 9A, and then the system load current is increased, the BATFET P-MOSFET will slowly heat up .

My design requirement is to ensure that the temperature of the BATFET is within the acceptable range when the maximum discharge current of the lithium iron battery is 12.5A.

May I ask what causes this BATFET heating situation?

Regards

thanks

Jiang Huigen

over 5 years ago

0 Tiger Zhou over 5 years ago

TI__Mastermind 33445 points

The main loss is conduction loss, suggest monitoring BATDRV voltage at the same time.

0 Huigen Jiang over 5 years ago in reply to Tiger Zhou

Prodigy 60 points

Hi Tiger Zhou，

The PMOS model of BATFET is changed to SiRA99DP,

RDS(on) max=0.0017Ω at VGS = -10 V , RDS(on) max=0.00265Ω at VGS = -4.5 V,

the loss from RDS(on) should be within the acceptable range, so that the loss of the body diode cannot be judged.

Under low load conditions, BATDRV#=2.672V, VSYS=13.19V, Vgs=-10.518V,

as the load current increases, the BATDRV# voltage drops, Vgs> -10V.

Can you describe the voltage passed to loss and monitor BATDRV in more detail?

Regards

thanks

Jiang Huigen

0 Tiger Zhou over 5 years ago in reply to Huigen Jiang

TI__Mastermind 33445 points

BATDRV voltage looks okay. Just make sure the BATFET voltage drop is within range. The power loss is equal to the multiplication of voltage drop and conduction current.

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BQ25703A: The heat output of the BQ25703A BATFET increases as the system load current increases.