Register Settings of RT9467 when its Parallel Charging with Switching Capacitor


In portable device applications, designers usually parallel switching capacitor chargers with a switching charger to enhance charging efficiency and reduce charging time. This application note provides the register control settings of the RT9467 when the system transitions from battery charging with a switching charger to using switching capacitor chargers. Note that users must follow this application note for the charging process.

1 Charging System Structure

Figure 1 presents a simplified block diagram of the charging system. In this charge system, a smart capacitor divider charger is used to detect the USB BC1.2 standard of the adapter, and the PD controller is used to communicate with the adapter by the PD protocol. Once the smart wall adapter is detected, the AP will control both the switching charger and smart capacitor divider charger to achieve a high current charging period. These devices can communicate with the AP through an I2C serial interface.

Technical Document Image Preview

Figure 1. Function Block Diagram of the Charging System

The charge profile of a high-capacity battery using the RT9467 and a capacitor divider charger is shown in Figure 2. In order to achieve the charge profile, the RT9467 is required to dominate the pre-charge, fast charge when the battery voltage is lower than the system startup voltage, constant voltage, and termination periods, respectively. The capacitor divider charger is used to achieve the fast charge period. To shorten the constant voltage period, the capacitor divider charger is controlled to reduce the charge current by ramp steps.

Technical Document Image Preview

Figure 2. Charge Profile Using the RT9467 and Smart Capacitor Divider Charger

2 RT9467 Software Notice

When the RT9467 starts up, it sets the system voltage before the capacitor divider charger enters the fast charge period. Especially, setting the RT9467 MIVR to 13.4V causes the RT9467 to stop switching, as shown in Figure 4. In this moment, only Q1 and Q2 are turned off, while QRB remains on, as shown in Figure 3. Therefore, when VBUS is plugged out in the fast charge period by the capacitor divider charger, both VBUS and PMID discharge at the same time to prevent VDS from exceeding the clamping voltage of the QRB MOS when VBUS voltage changes drastically. After VBUS is plugged out, VBUS is lower than the VBUS_INSERT of the smart capacitor divider charger. Set the RT9467 MIVR to 4.4V (default) and wait for VBUS to be plugged in again.

The host must set the RT9467 registers step by step. The programming steps are shown as below:

1. Write REG0x06 = 0xFF (after the system wakes up, set MIVR to 13.4V)

2. Write REG0x06 = 0x0B (when VBUS < VBUS_INSERT, set MIVR to 4.4V (default))

Technical Document Image Preview

Figure 3. Circuit Diagram of RT9467

Technical Document Image Preview

Figure 4. System Control Flow Chart

3 Conclusion

In conclusion, the information provided in this application note includes the necessary settings when the RT9467 in parallel with a switching capacitor. By setting the MIVR voltage higher than the VBUS voltage when the system is charging with the switching capacitor, the RT9467 will turn on QRB (the MOS between VMID and VBUS) and stop switching. This setting meets the requirements of fast charging systems and prevents the VMID-VBUS voltage from exceeding the QRB's AMR when the system is charging with the switching capacitor.

The above summary concludes the contents covered in this application note. To stay informed with more information about our products, please subscribe to our newsletter.

4 Appendix

Functional Register Description

I2C Slave Address: 1011011(5BH)

R/W: Read and write

RWC: Read and write, also automatically cleared by particular conditions

Register Address: 0x06, Register Name: CHG_CTRL6






Control 6






Reset Value






Input MIVR threshold setting
0000000: 3.9V
0000001: 4V
0000010: 4.1V
0000011: 4.2V
0000100: 4.3V
0000101: 4.4V (default)
0000110: 4.5V

0011110: 6.9V
0011111: 7V

0110010: 8.9V
0110011: 9V

1010000: 11.9V
1010001: 12V

1011111: 13.4V
1100000 to 1111111: 13.4V

Next Steps
Richtek Newsletter Subscribe Richtek Newsletter
Download Download PDF