Auxiliary Power Strategy

With the requests of low current consumption in standby mode and ship mode, this design uses the auxiliary power strategy shown in Figure 2-2.

Figure 2-2 Auxiliary Power Strategy.

The design has a 100-V Input, 0.5-A, ultra-low I_Q synchronous Buck DC/DC converter LM5163 with a low I_Q LDO TLV704 as the main power source when the system is working in normal mode. The BQ76952 regulator is configured to 5-V output which is the power source when the system is working in standby mode. The series diode on the BQ76952 regulator output makes sure all power is from the DC/DC converter in normal mode preventing the BQ76952 regulator circuits from overheating, so DC/DC output should be designed a little higher than 5 V, BQ76952 regulator output. Detailed component design guidance is available from the LM5163 and LM5164 converter quickstart design tool. When the system experiences a serious cell under voltage and must enter ship mode, the MCU will configure the BQ76952 device to enter shutdown mode through an I2C command or RST_SHUT PIN and turn off LM5163 output through the EN PIN, which configures the system to very low current consumption mode. This design supports both charger attach and system detect wake up functions. Both methods wake up the BQ76952 device and enable normal 5-V regulator output, then the MCU is powered on and will enable the LM5163 through the EN PIN. The whole system then returns to normal mode.