Higher than 5-series cell packs may be supported by daisy-chaining multiple devices. Each device ensures OV, UV, OW, OTC, OTD, UTC, and UTD protections of its directly monitored cells, while any fault conditions automatically disable the global CHG and/or DSG FET driver.
Upper devices do not provide OCC, OCD1, OCD2, or SCD protections, as these are based on pack current. For the BQ77915 device used on the upper stack, the SRP and SRN pins should be shorted to prevent false detection.
To configure higher-cell packs, follow this procedure:
- Each device must have a connection on at least each of its three lowest cell input pins.
- It is highly recommended to connect higher cell count to the upper devices (for example, for a 7-series configuration, connect four cells on the upper device and three cells on the bottom device). This is to provide stronger CTRx signal to the bottom device.
- Ensure that each device’s CCFG pin is configured appropriately for its specific number of cells (that is, three, four, or five cells).
- Connect the upper CHG pins with an RCTRx to the immediate lower device CTRC pin.
- Connect the upper DSG pins with an RCTRx to the immediate lower device CTRD pin.
- All upper devices should have their SRP and SRN pins shorted to their VSS pins.
- Connect the upper CBI pins with an RCB to the immediate lower device CBO pin.
- Connect the upper LPWR pins with an RHIB to the immediate lower device PRES pin.
- Connect the upper OCDP pins with a 10-MΩ resistor to VSS. Use the lower OCDP pin to program the OCD1/2 delay.
Figure 9-14 10-Series Configuration with Internal Cell Balancing and HIBERNATE Mode Enabled