TIDUF14 October 2022
Figure 2-1 shows the system diagram.
The design uses the high-accuracy battery monitor and protector bq76952 from TI to monitor each cell voltage, pack current and temperature data, and protect the battery pack from all unusual situations, including: COV, CUV, OT, overcurrent in charge and discharge and short-circuit discharge. There is a lower-power MSP430™ MCU MSP430FR2155 which communicates with the monitor, deal with all system control strategy, and upload all the requested information to the system side. This design supports isolated RS-485 communication with a three-channel digital isolator ISO7731 and a RS-485 transceiver THVD1400 for better flexibility. An isolated CAN transceiver is also present to test auxiliary power circuit performance. Five pairs of N-Channel MOSFETs are driven by a dual-channel 5-A sink and source current low-side driver (UCC27524) for fast MOSFET turn on and off. Another low side driver, the UCC27517, is used to drive pre-discharge MOSFET on and off. This design uses a 100-V input, 0.5-A, ultra-low IQ synchronous Buck DC/DC converter LM5163 to step down battery voltage to power MOSFET drivers. A fly-buck converter TPS54308 is used to generate a non-isolated 3.3 V to power MSU and an isolated 5 V to power isolated communication transceivers. A low IQ LDO TPS7A24 makes the isolated output voltage stable. A ±1%, 10-kΩ linear thermistor with positive temperature coefficient and 0603 package TMP61 is utilized to monitor the MOSFET temperature and measured by the MCU ADC.