5.2.12 Delta Voltage

5.2.13 Default Ra and Ra Tables

5.3 DETAILED DESCRIPTION OF DEDICATED PINS

5.3.1

The Operation Configuration Register

5.3.2

Pin Function Code Descriptions

5.3.3

BAT_LOW Pin

bq27500

bq27501

System-Side Impedance Track™ Fuel Gauge

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SLUS785D – SEPTEMBER 2007 – REVISED APRIL 2008

The bq27500/1 stores the maximum difference of Voltage( ) during short load spikes and normal load, so

the Impedance Track™ algorithm can calculate remaining capacity for pulsed loads. It is not

recommended to change this value.

These tables contain encoded data and, with the exception of the Default Ra Tables, are automatically

updated during device operation. No user changes should be made except for reading/writing the values

from a pre-learned pack (part of the process for creating golden image files).

Some bq27500/1 pins are configured via the Operation Configuration data flash register, as indicated in

Table 5-3. This register is programmed/read via the methods described in Section 4.2.1, Accessing the

Data Flash. The register is located at subclass = 64, offset = 0.

Table 5-3. Operation Configuration Bit Definition

Operation

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

Cfg

High byte

RESCAP

–

–

PFC_CFG1

PFC_CFG0

IWAKE

RSNS1

RSNS0

Low byte

–

IDSELEN

SLEEP

RMFCC

BATL_POL

BATG_POL

–

TEMPS

RESCAP = No-load rate of compensation is applied to the reserve capacity calculation. True when set. Default is 0.

PFC_CFG1/PFC_CFG0 = Pin function code (PFC) mode selection: PFC 0, 1, or 2 selected by 0/0, 0/1, or 1/0, respectively.

Default is PFC 1 (0/1).

IWAKE/RSNS1/RSNS0 = These bits configure the current wake function (see Table 5-4). Default is 0/0/1.

IDSELEN = Enables cell profile selection feature. True when set. Default is 1.

SLEEP = The fuel gauge can enter sleep, if operating conditions allow. True when set. Default is 1.

RMFCC = RM is updated with the value from FCC, on valid charge termination. True when set. Default is 1.

BATL_POL = BAT_LOW pin is active-high. True when set. Default is 1.

BATG_POL = BAT_GD pin is active-low. True when cleared. Default is 0.

TEMPS = Selects external thermistor for Temperature( ) measurements. True when set. Default is 1.

The bq27500/1 has three possible pin-function variations that can be selected in accordance with the

circuit architecture of the end application. Each variation has been assigned a pin function code, or PFC.

When the PFC is set to 0, only the bq27500/1 measures battery temperature under discharge and

relaxation conditions. The charger does not receive any information from the bq27500/1 about the

temperature readings, and therefore operates open-loop with respect to battery temperature.

A PFC of 1 is like a PFC of 0, except temperature is also monitored during battery charging. If charging

temperature falls outside of the preset range defined in data flash, a charger can be disabled via the

BAT_GD pin until cell temperature recovers. See Section 5.6.2, Charge Inhibit, for additional details.

Finally when the PFC is set to 2, the battery thermistor can be shared between the fuel gauge and the

charger. The charger has full usage of the thermistor during battery charging. The fuel gauge uses the

thermistor exclusively during discharge and battery relaxation.

The PFC is specified in Operation Configuration [PFC_CFG1, PFC_CFG0]. The default is PFC = 1.

The BAT_LOW pin provides a system processor with an electrical indicator of battery status. The signaling

on the BAT_LOW pin follows the status of the [SOC1] bit in the Flags( ) register. Note that the polarity of

the BAT_LOW pin can be inverted via the [BATL_POL] bit of Operation Configuration.

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FUNCTIONAL DESCRIPTION

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