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Part Number: BQ2057T
Refer to the circuit shown in Fig.1 of SLUS025F and change to the following parts.・ Q1: 2SA2097・ C1: 10uF × 2・ RT1: 10kΩ・ RT2: 39kΩ・ Rsns, R1, C2 unchanged・ Battery Rated capacity: 2800mAh Nominal voltage: 7.2V Charging voltage: 8.2V Charging current: MAX.1400mA1. What are the conditions for turning off Q1?2. Does Q1 fit this mechanism?3.I am trying to change Rsns to 0.1Ω. Does Q1 work properly?
please tell me!
The BQ2057T is and older device with a large number of external parts. Can you change to another device?
A more integrated device to consider is the BQ24004, 05, or 06.
Bill Johns, Applications Engineer
Texas Instruments Inc
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In reply to Bill Johns:
I can't change the device.Please answer my question on this device.
In reply to user6251399:
TS input -- Battery Temp
・ RT1: 10kΩ・ RT2: 39kΩ
Voltage at TS needs to be between 30% and 60% of VCC for normal operation. The RT1 and RT2 value alone will be a little high of this point.
1. What are the conditions for turning off Q1?---This would be any conditions that disables charge or charge complete.2. Does Q1 fit this mechanism?---We have not evaluated the 2SA2097, it look similar to FZT788B. But you will need to evaluate performance.3.I am trying to change Rsns to 0.1Ω. Does Q1 work properly?---With Rsns at 0.2 ohms the charge current is 500mA, 0.1 ohm will be 1A. this should work. The device is a linear regulator and will have high power dissipation in Q1. Increasing charge current will increase power dissipation. This needs to be take into consideration.
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