BQ76PL536APAP datasheet(15/60 Pages) TI

15 / 60 page

0.1

BAT

1 kW

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bq76PL536A

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SLUSAD3A – JUNE 2011 – REVISED AUGUST 2012

3 to 6 Series Cell Configuration

When fewer than 6 cells are used, the most-positive cell voltage of the series string should be connected to the

BAT1/BAT2 pins, through the RC input network shown in the Reference Schematic section. Unused VCx inputs

should be connected to the next VCx input down until an input connected to a cell is reached – i.e., in a four cell

stack, VC6 connects to VC5, which connects to VC4.

The internal multiplexer control can be set to scan only the inputs which are connected to cells, thereby speeding

up conversions slightly. The multiplexer is controlled by the ADC_CONTROL[CN2:0] bits.

Figure 4. Connecting < 6 Cells (4 Shown)

Cell Voltage Measurements

Converting the returned cell measurement value to a dc voltage (in mV) is done using the following formula (all

values are in decimal).

mV = (REGMSB × 256 + REGLSB) × 6250 / 16383

Example:

Cell_1 == 3.35 V (3350 mV);

After conversion, REG_03 == 0x22; REG_04 == 0x4d

0x22 × 0x100 + 0x4d = 0x224d (8781.)

8781 × 6250 / 16,383 = 3349.89 mV

≈ 3.35 V

GPAI or VBAT Measurements

The bq76PL536A features a differential input to the ADC from two external pins, GPAI+ and GPAI–. The ADC

GPAI result register can be configured (via the FUNCTION_CONFIG[GPAI_SRC] to provide a measurement of

the voltage on these two pins, or of the brick voltage present between the BATx pins and VC0.

In the bq76PL536A device, the VBAT measurement is taken from the BATx pin to the VC0 pin, and is a separate

input to the ADC mux. Because this is a separate input to the ADC, certain common system faults, such as a

broken cell wire, can be easily detected using the bq76PL536A and simple firmware techniques.

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