BQ76PL455APFCT datasheet(112/125 Pages) TI1

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bq76PL455A

SLUSCL0A – SEPTEMBER 2016 – REVISED OCTOBER 2016

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Initialization Set Up (continued)

8.3.2 Device Setup/User Configuration Summary

An abbreviated version of starting up a stack of devices is described. Many more details are available in the

bq76PL455A-Q1 Software Design Reference (SLVA617), including validated communications sequences.

1. Set an address for each device in the stack, using GPIO pins or Auto-Addressing.

(a) Make sure all devices are awake and are ready to receive the Auto-Address Enable command.

(b) Turn on the downstream communications drivers on all devices in the chain.

(d) Send out new addresses to all possible bq76PL455A device addresses, in incrementing order starting at

zero.

(e) Read back the value stored in the Device Address register from each newly addressed device, starting at

address zero and proceeding sequentially. The last bq76PL455A to respond successfully is the last

device in the serial chain. Steps d and e may be shortened if the range of possible devices is known in

advance. Limit the number addressed to the expected quantity.

(f) Turn off the high-side communications receiver on the last (top-most) device in the chain.

(g) Turn off the single-ended transmitter on all but the lowest device in the chain.

(h) Starting at the top of the stack of devices, clear all existing faults. It is important to start clearing faults

from the top of the stack to prevent faults from higher units from re-enabling faults as they propagate

down the stack.

2. Configure the AFE (Channel Selections and Fault Thresholds)

Prior to reading voltages from daisy-chain networked devices, the AFE on each of the stacked devices

should be properly configured to scan the desired channels at the desired timing. Once each device has

been properly configured, reading voltages from each device can begin.

The following listed steps should be performed as a group for each stacked device, starting from the top

device, continuing through, and ending with the bottom-most device of the stack. Generally, this configuration

is done in advance during factory initialization and test and the desired configuration parameters are stored

in EEPROM on each device.

(a) Configure GPIO pins as required by your design

(b) Configure the initial sampling delay

(d) Configure the oversampling rate

(e) Select number of cells and desired channels to sample

(f) Set overvoltage and undervoltage thresholds

(g) Check and clear faults, which may have occurred because of the configuration.

3. Reading Voltages from Daisy-Chain Networked Devices

When bq76PL455A devices are networked, wherein each device monitors a section of a stack of cells, it is

important to try to capture the voltages of each sub-stack as synchronously as possible. This snapshot can

be obtained if all devices in the stack are sampling in parallel.

Summary of Steps for Reading Voltages from Daisy-Chain Networked Devices

Broadcast a Sample and Send command to all devices in the network: this causes all devices to start

sampling in parallel, and, once the sampling is complete, the devices will respond in sequence, starting

at the highest address with the sampled data. Alternatively, the following two-step process could be

employed to similar effect:

(a) Broadcast a trigger to all devices in the network to start sampling the selected cell and auxiliary channels

and temperature.

(b) Query each device individually in sequence for the data collected during the last snapshot read.

BQ76PL455APFCT Datasheet(PDF) 112 Page - Texas Instruments

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