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© 2021 ROHM Co., Ltd.
No. 64UG016E Rev.001
MAY.2021
User’s Guide
BD71631QWZ-EVK-001
About the current of the external resistor that generated by the FB terminal and FBRE terminal
Nch FET is built in between the VFBG terminal and the GND terminal.
When the VIN terminal is connected, the Nch FET turns on and current flows from the battery to the external resistor.
When the VIN terminal is disconnected, the Nch FET turns off and no current flows from the battery to the external resistor.
If the VFBRE terminal is connected to GND and recharging is disabled , the internal Nch FET will be turned off when charging is
completed even if VIN is connected.
2.
Charge current, Termination current setting
The charging current I
CHG
can be set by the following formula using the external resistor RICHG1.
𝐼
𝐶𝐻𝐺
= (500000 RICHG1 [Ω]
⁄
)
[mA]
The charging current can be set up to 300 mA (VIN ≥ 4 V, VIN-VOUT ≥ 1 V), 100 mA (VIN ≥ 4 V, VIN-VOUT ≥ 0.3 V), and 30 mA (2.9
V ≤ VIN ≤ 5.5 V, VIN-VOUT ≥ 0.3V). There is a limit to the voltage between VIN and VOUT in the usage range of the charging
current.
The termination current I
TERM
can be set by the following equation using the external resistor RITERM.
The termination current can be set from 50 μA to 10 mA.
𝐼
𝑇𝐸𝑅𝑀
= (50000 RITERM [Ω]
⁄
)
[mA]
ICHG
RICHG1
RITERM
ITERM
Figure 6. Resistor setting of I
CHG
and I
TERM
3.
Charge Current vs Battery Temperature
It is possible to monitor the temperature of the battery using NTC thermistor.
The charging current is controlled by the battery temperature, as shown in the temperature profile in Figure 7.
It is set by the NTC thermistor and pull-up resistor in Figure 8.
The component constants can be set according to the voltage of the NTC terminal at each temperature.
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