BQ28Z560-R1 datasheet(12/60 Pages) TI1

12 / 60 page

bq28z560-R1

SLUSBD3 – APRIL 2013

www.ti.com

GENERAL DESCRIPTION

The bq28z560-R1 accurately predicts the battery capacity and other operational characteristics of a single Li-Ion

based rechargeable cell, while also providing a state-of-the-art protection function against short circuit,

overcurrent, and overvoltage. The device can be integrated by a system processor to provide cell information,

such

state-of-charge

(SOC),

Remaining

Capacity,

and

Full

Charge

Capacity

(FCC).

NOTE

FORMATTING CONVENTIONS IN THIS DOCUMENT:

Commands:

Italics

with

parentheses

and

breaking

spaces;

for

example,

RemainingCapacity()

Data Flash: Italics, bold, and breaking spaces; for example, Design Capacity

Data Flash Bits: Italics and bold; for example, [NR]

Modes and States: All capitals; for example, SEALED mode

DATA ACQUISITION

Cell Voltage

The bq28z560-R1 samples the single cell voltage from the BAT input terminal. The cell voltage is sampled and

updated every 1 s in NORMAL mode. To ensure accurate cell measurement, the VSS ground connection of the

bq28z560-R1 should be connected to the negative terminal of the single cell and not to the positive side of the

sense resistor.

Charge Measurement

The device samples the charge into and out of the single cell using a low-value sense resistor. The resistor

(typically 5 m

Ω to 20 mΩ) is connected between SRP and SRN to form a differential input to an integrating ADC

(coulomb counter). Charge activity is detected when VSR = VSRP – VSRN is positive and discharge activity is

detected when VSR = VSRP – VSRN is negative. This data is integrated over a period of time using an internal

counter, and updates RemainingCapacity with charge and discharge amounts every 1 s in NORMAL mode.

Current Measurement

The device has a FIFO buffer, which uses the last four coulomb counter readings to calculate the current. The

current is updated every 1 s in NORMAL mode.

CELL DETECTION

Internal Short Detection

The device can detect an internal battery short by setting the [SE_ISD] bit in Pack Configuration Register B. The

bq28z560-R1 compares the self-discharge current calculated based on StateOfCharge() in RELAX mode and

AverageCurrent() measured in the system. The self-discharge is measured at 1-hour intervals. When the battery

SelfDischargeCurrent() is less than a predefined ISD Current threshold, the ISD flag bit is set high.

Tab Disconnection Detection

The bq28z560-R1 detects tab disconnection by change in StateOfHealth(). This feature is enabled by setting the

[SE_TDD] bit in Pack Configuration Register B. The [TDD] bit is set in the flag register when the ratio of current

StateOfHealth() divided by the previous StateOfHealth() reported is less than TDD SOH percent.

TEMPERATURE MEASUREMENT AND THE TS INPUT

The bq28z560-R1 measures external temperature via the TS pin in order to supply battery temperature status

information to the gas gauging algorithm and charger-control sections of the gauge. Alternatively, the gauge can

also measure internal temperature via its on-chip temperature sensor. Refer to the Pack Configuration[TEMPS]

control bit.

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