Q: When using the DS2715 to charge a 9V 300mAH NIMH battery, the input power is 12VDC. We do not plan on using temperature detection. When the 12VDC is connected, the internal relay uses the 12VDC supply to charge. If the 12VDC is removed, the relay is disconnected. For our application, can we use a linear application circuit (as shown in Fig. 6 in the datasheet)? What is the purpose of Q2 at the Rt pin? Can we remove it? What is the largest discharge current?
A:
- Yes, please use Fig. 6. If you do not need temperature detection, you can use a fixed 10K resistor to connect to the THM1 pin.
- Q2 has two functions: In the absence of an external power supply, the Q2 is not connected. Under this condition, Rt is floating and the device is in suspend mode. For a detailed description of suspend mode, refer to pages 9 and 10 in the datasheet. When a power supply input is available, Q2 conducts to connect Rt to GND through a 86K resistor to set the quick charge time. Regarding the resistor selection, please refer to the Timeout Selection section on page 11 of the datasheet. Please design the section based on the connections in Fig. 6.
- In discharge mode, Vch is driven to low and the largest discharge current is determined by the load.