6295CV View Datasheet(PDF) - Intersil

Part Name

Description

Manufacturer

6295CV

Low Voltage Fuel Gauge

Intersil 

ISL6295

enabled, it is updated every 0.5s by adding the contents of

the assigned result register value to the previous

accumulated value. The accumulators are listed below with

their assigned source registers:

ABBR.

DCAIres

CCA

TA

GPADA

ACCUMULATOR NAME

SOURCE

Discharge Current Accumulator Ires (Sign bit = 1)

Charge Current Accumulator Ires (Sign bit = 0)

Temperature Accumulator

ITres or ETres

GPAD Accumulator

GPADres

The measurement resolution of the accumulated value is

equal to that selected for the associated conversion, up to a

converter resolution of 15-bits. If a 15-bit A/D value is being

accumulated, then the accumulator resolution in microvolt

seconds is:

Accumulator LSB (µVs) = (VREF/215) µV * 0.5s

When the 170mV reference is selected, this value equates

to 2.59µVs per LSB.

CHARGE/DISCHARGE ACCUMULATORS

The DCA accumulator is intended to accumulate discharge

current, and the CCA accumulator is intended to accumulate

charge current. Both accumulators use the Ires register as

its source. For this reason, the lres register should be

programmed for current measurement by selecting the SR

pin as the multiplexed ADC input source.

During charging, the voltage at the SR pin will be negative.

This translates to a positive voltage measurement with the

sign bit set to ‘0’. Whenever the sign bit equals ‘0’, the

measured result will be added to the CCA register contents

and the sum is returned to CCA. In this way, total charge

current is accumulated in the CCA.

Similarly, during discharge, a positive voltage will exist at the

SR pin. In this case, the conversion will result in the sign bit

being set to ‘1’ in the Ires register, indicating a negative

value or discharge current condition. Under this condition,

the DCA register will be updated with the discharge current

measured during that conversion.

The value stored in the DCA or CCA register can be

interpreted as illustrated in the following example. Using a

20mΩ sense resistor, the LSB can expressed in units of

current as follows:

Accumulator LSB (µAs) = Voltage LSB/RSENSE

= 129.5µAs

The “Accum” bit in the AccumCtrl register must be enabled for

accumulation to occur in both the CCA and DCA registers.

CHARGE/DISCHARGE TIME COUNTERS

The Charge Time Counter (CTC) will increment at the rate of

2 counts every second as long as a negative voltage is

measured at the SR pin. The CTC can thereby maintain a

time count representing the total time that charge current

has flowed into the battery.

The Discharge Time Counter (DTC) will increment at the rate

of 2 counts every second as long as a positive voltage is

measured at the SR pin. The DTC can thereby maintain a

time count representing the total time that discharge current

has flowed from the battery.

Power Modes

The ISL6295 has five operational power modes: Power-on

Reset, Run, Sample, Sample-Sleep, and Shelf-Sleep. Each

consumes power according to the configuration settings as

described below:

POWER-ON RESET

When power is first applied to the V input, the ISL6295

automatically executes a Power-on Reset sequence. The

device is held in a RESET state while the voltage is below

the minimum operating threshold, VPOR. When the voltage

on the VP pin rises above the VPOR threshold, the ISL6295

will initialize itself by loading the internal counters, data and

control registers with default values pre-written into the non-

volatile EEPROM memory. Please refer to “Register

Initialization” and “Factory Register Initialization” sections for

a detailed description of the register initialization operation.

When this is complete, the ISL6295 will enter the Run Mode.

RUN MODE

During Run mode, the ISL6295 performs continuous A/D

conversion cycles per the programming of the A/D

conversion cycle described in the “A/D Conversion Cycle”

section. During each cycle, one to eight conversions are

performed, and the respective accumulators/time counters

are updated at 0.5s interval using the most recent A/D

conversion results.

Run Mode is entered following a Power-on Reset when the

pack voltage (VPACK) applied to the VP pin rises above the

VPOR threshold. Run Mode can also be entered from the

Sample, Sample-Sleep, and Shelf-Sleep modes as to be

described.

The ISL6295 will remain in RUN mode as long as the pack

voltage is above the VPOR threshold and Sample, Sample-

Sleep, and Shelf-Sleep modes are not active.

SAMPLE MODE

In Sample Mode, A/D measurements are not continuously

performed as in Run Mode. Instead, they are performed at a

user selectable rate. The purpose of Sample Mode is to

reduce power consumption during periods of low rate

change (charge or discharge). The power advantage of

Sample Mode comes from the reduction in frequency of A/D

measurements. The accumulation counters and timers will

continue to run at the rate of 0.5s per update.

Sample Mode is entered by programming the "Samp" bit to

‘1’ in the A/D Configuration register. The ISL6295 will remain

8

FN9074.0

October 25, 2005

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