BQ76PL455APFCT datasheet(25/125 Pages) TI1

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SLUSCL0A – SEPTEMBER 2016 – REVISED OCTOBER 2016

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7.3.3.4 VSENSE Input Channels

The VSENSE input channels measure the voltages of individual cells in the range of 1 V-to-4.95 V. Each input

should connect to an external low-pass filter (LPF) to reduce noise at the input, and a Zener diode to provide

protection to the device during random hot-plug cell connection. Typical values for the LPF range from 100

Ω to

1 k

Ω, and 0.1 µF to 1 µF. Values outside this range may degrade accuracy due to system-level noise or from

excessive IR loss in the series resistor.

Tie up unused inputs to the highest-connected cell. For example, in a 14-cell system, tied to VSENSE14 are

unused inputs VSENSE15 and VSENSE16. Channels are used from lowest to highest, with VSENSE0

connected to the (–) terminal of the bottom cell.

The values returned from an ADC conversion for these channels convert to volts by:

VCELL = [(2 × VREF) / 65535] × READ_ADC_VALUE

(1)

A number of factors affect total channel measurement accuracy, including, but not limited to, variations due to IR

reflow, board-level stresses, any current leakage in external components, and the method of sampling. It is highly

recommended that the end user perform GAIN and OFFSET calibration as described in the Application and

Implementation section.

7.3.3.5 AUXn Input Channels

The AUXn input channels are used to measure external analog voltages from approximately 0 V to 5 V. A typical

use for these channels is to measure temperature using thermistors. These channels require a simple external

low-pass filter to reduce high frequency noise for best operation. The RC values correspond to the user's

application requirements.

The values returned from an ADC conversion for these channels convert to volts by:

VAUX = [(2 × VREF) / 65535] × READ_ADC_VALUE

(2)

7.3.3.6 VMODULE Measurement Result Conversion to Voltage

VMODULE is the voltage measured from the TOP pin to GND. The value scales by 25 with an internal resistor

voltage divider. Setting TSTCONFIG[MODULE_MON_EN] enables measuring of VMODULE voltage. Enable or

disable the measurement to aid with self-testing. When set to 0, the channel should measure close to 0 V.

The values returned from an ADC conversion for this channel converts to volts by:

VMODULE = ([(2 × VREF) / 65535] × READ_ADC_VALUE) × 25

(3)

7.3.3.7 Digital Die Temperature Measurement

The temperature of the digital die may be measured as a part of the normal ADC measurement sequence by

setting bit CHANNELS[CMD_TSEL]. The reported result is the voltage from the temperature sensor, not the

actual temperature.

No averaging is ever performed on this channel, but the timing will appear as if the requested oversampling was

performed.

FAULT_SYS[INT_TEMP_FAULT] is continuously updated based on the currently stored measurement result and

threshold. To allow clearing of the fault, sample the temperature within a normal operating range.

Conversion formula:

Internal Digital Die Temperature °C = (VADC – 2.287) × 131.944

(4)

7.3.3.7.1

Automatic Temperature Sampling

After initialization is complete, an internal timer will cause the digital-die temperature sensor sampling to be

scheduled once per second. No oversampling is performed. If a command cycle occurs that samples the digital

die temperature sensor, the timer resets. A command will interrupt an automatic temperature sample, but if the

command does not sample the digital die temperature, the automatic temperature sample will occur as soon as

the command completes. This can cause sample values to appear to change without a sample request.

BQ76PL455APFCT Datasheet(PDF) 25 Page - Texas Instruments

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