SLUAA16A August   2020  – October 2023 BQ79600-Q1

 

  1.   1
  2.   BQ79600-Q1 Design Recommendations
  3.   Trademarks
  4. 1Circuit Design
    1. 1.1 Power Supply (BAT, CVDD, DVDD, VIO pins)
    2. 1.2 Inhibit Output (INH pin)
    3. 1.3 Communication to Host (MOSI/RX, MISO/TX, nCS, SCLK, nUART/SPI (SPI_RDY) pins)
    4. 1.4 Fault Output (NFAULT pin)
    5. 1.5 Communication to Battery Monitor Device (COMHP, COMHN, COMLP, COMLN pins)
  5. 2Layout Guidelines
    1. 2.1 Ground Planes
    2. 2.2 Bypass Capacitors for Power Supplies and References
    3. 2.3 UART/SPI Communication
    4. 2.4 Daisy Chain Communication
  6. 3Daisy Chain Signal Integrity
    1. 3.1 Daisy Chain Receiver Threshold
    2. 3.2 Common and Differential Mode Noise
    3. 3.3 BCI Performance
    4. 3.4 Radiated Emissions Performance
  7. 4Summary
  8. 5References
  9. 6Revision History

1.3 Communication to Host (MOSI/RX, MISO/TX, nCS, SCLK, nUART/SPI (SPI_RDY) pins)

The BQ79600-Q1 supports communication to the host microcontroller through either UART interface or SPI interface using MOSI/RX, MISO/TX, nCS, SCLK and nUART/SPI (SPI_RDY) pins. The circuit configuration required to use each of these communication interfaces is described in this section.

Note:

MISO/TX pin is pulled high by the BQ79600-Q1 device when idle (nCS = HIGH). Therefore, the SPI interface cannot be shared with other slave devices. Use another SPI interface in the MCU for other slave devices.

nUART/SPI (SPI_RDY) pin is a digital I/O pin with 2 functions:

  1. This pin is used to select SPI or UART interface. To use the UART interface, connect this pin to GND. To use the SPI interface, connect this pin to VIO through a 10-100 KΩ pull-up resistor and connect this pin to a GPIO pin from the microcontroller.
  2. When SPI mode is selected, this pin has an additional function. After device initialization in SPI mode, this pin is an output signal from the BQ79600-Q1 that indicates to the host when data is ready to be read or written.

nCS pin is a digital input used as the active low chip select pin for SPI interface. In SPI mode, connect this pin to VIO with 10-100 KΩ pull-up resistor and to the nCS pin from the SPI master microcontroller. The BQ79600-Q1 device uses specific signal patterns received on MOSI/RX pin called "pings" that are used to change the power state of the device. In SPI mode, the pings are only valid if nCS is held low. To avoid unintended pings to be read by the device, nCS signal cannot be hardwired to GND when SPI interface is used. In UART mode, connect this pin to GND.

SCLK pin is the clock input for SPI interface. If SPI mode is selected, connect this pin to GND with a 10-100 KΩ pull-down resistor and connect to the SPI SCLK pin on the MCU. In UART mode, connect directly to GND.

MISO/TX pin is the SPI master input slave output or the UART transmitter output. Connect this pin to VIO with a 10-100 KΩ pull-up resistor at MCU side. If SPI interface is used, connect this pin to the SPI MISO pin on the MCU. If UART interface is used, connect to the UART RX pin on the MCU.

MOSI/RX pin is the SPI master output slave input or the UART receiver input. Connect this pin to VIO with a 10-100 KΩ pull-up resistor. Don't leave it unconnected. If SPI interface is used, connect this pin to the SPI MOSI pin on the MCU. If UART interface is used, connect to the UART TX pin on the MCU.

Figure 1-3 shows the recommended design when the host MCU uses UART interface to communicate to BQ79600-Q1 device. For recommended design when SPI interface is used for communication between the host MCU and BQ79600-Q1 see Figure 1-4.

GUID-20200820-CA0I-CXJH-1VR9-VJ4RWFT0MS69-low.png Figure 1-3 UART Interface Used
GUID-20200820-CA0I-V570-SXKS-LZ7PNTR0XK2B-low.png Figure 1-4 SPI Interface Used
Table 1-3 SPI/UART Design Considerations
Pin SPI Mode UART Mode
MOSI/RX Connect to VIO with a 10-100 KΩ pull-up resistor and to the MCU's SPI SIMO pin. Connect to VIO with a 10-100 KΩ pull-up resistor and to the MCU's UART TX pin.
MISO/TX Pull-up to VIO with a 10-100 KΩ resistor on the MCU side. Connect to the MCU's SPI SOMI pin. Do not connect other slave devices on the SPI bus since MISO line is pulled high by the BQ79600-Q1 device when idle. Pull-up to VIO with a 10-100 KΩ resistor on the MCU side. Connect to the MCU's UART RX pin.
SCLK Connect to GND with a 10-100 KΩ pull-down resistor and to the MCU's SPI SCLK pin. Connect to GND.
nCS Connect to VIO with 10-100 KΩ pull-up resistor and to the MCU's SPI nCS pin. Connect to GND.
nUART/SPI (SPI _RDY) Connect to VIO with 10-100 KΩ pull-up resistor and to a GPIO pin on the MCU. Connect to GND.