JAJSRJ8 データシート

JAJSRJ8B September 2019 – October 2023 BQ75614-Q1

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8.3.2.2.1.2 CB and Current Sense Channel Measurements

One slot, the CB MUX output slot, is assigned in the AUX ADC round robin cycle for the CB channels (differential CB_n–1 – CB_n, where n = 1 to 16) and current sense (differential SRP – SRN)channel measurement because these channels are multiplexed to a single input to the AUX ADC multiplexer. For a single CB or current sense channel measurement, it takes multiple round robin cycles because the device has to wait for the AAF settling time as well.

Because of the need to wait for the AAF to settle, the AUX ADC would only measure CB and current sense channels that are active and are selected by the MCU; inactive or unselected channels are skipped.

Active CB channels are determined by the ACTIVE_CELL[NUM_CELL3:0] setting. These bits set the highest active channel number. For example, when a 14S is connected to the device, the MCU sets the ACTIVE_CELL[NUM_CELL3:0] to 14S, the device assumes CB channels 1 through 14 are active; CB channels 15 and 16 are inactive and will be skipped by the AUX ADC.

MCU can control which CB and current sense channels to be measured through the AUX ADC. The ADC_CTRL2[AUX_CELL_SEL4:0] gives the options to run through all the active CB channel and current sense channels or to lock to a single CB channels or lock to the current sense channel.Figure 8-9 shows the example of how the AUXCELL slot is implemented with different [AUX_CELL_SEL4:0] setting.

It is recommend to run AUX ADC in continuous mode and all AUX ADC to measure through all the active CB channel once. This enables the device to reduce the common mode error in AUX ADC measurement. MCU shall perform this procedure before running ADC comparison related diagnostic or locking to a single CB or current sense channel measurement.

There is no post-ADC LPF in the AUX ADC path. When the AUX ADC measurements are used during diagnostics, the AUX CELL (CB channel) measurements are compared against the Main ADC prefiltered measurements. While the device performs VCELL (from Main ADC) to AUX CELL (from AUX ADC) measurement comparison internally. See Section 8.3.6.4 for more details.

The device makes the CB or current sense channel measurement available to read only when the [AUX_CELL_SEL4:0] bits are set to lock on a single CB (must be active) or current sense channel. The measurement is reported in the AUX_CELL_HI (high-byte) and AUX_CELL_LO (low-byte) registers. The result registers will be updated after the AAF settling time is passed. For any other conditions, including lock to an inactive CB channel, the result registers remain with the default value 0x8000.

Figure 8-9 CB MUX Output Slot with Different [AUX_CELL_SEL4:0] Setting

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8.3.2.2.1.2 CB and Current Sense Channel Measurements