intersil ISL6295 DATA SHEET

ISL6295

Data Sheet November 10, 2005

Low Voltage Fuel Gauge

The ISL6295 is a cost-effective, highly accurate IC that measures, stores, and reports all of the critical parameters required for rechargeable battery monitoring with a minimum of external components. It precisely measures charge/ discharge current as well as voltage and temperature of a battery pack. In addition, the ISL6295 accurately accumulates both charge and discharge current as independent parameters. Temperature history can also be maintained for calculating self-discharge effects.

The ISL6295 integrates a highly accurate 16-bit (15-bit plus sign) integrating A/D converter that performs calibrated current measurement to within ±0.5% error. On-chip counters precisely track battery charge/discharge and temperature history. Also included are an on-chip voltage regulation circuit, non-crystal time base, and on-chip temperature sensor. The operating voltage range of the ISL6295 is optimized to allow a direct interface to a single cell Li-Ion/Li-Poly pack. 256 bytes of general-purpose nonvolatile EEPROM storage are provided to store factory programmed, measured, and user defined parameters.

Efficient communication is provided through an industry standard SMBus/I

C™ compatible 2-wire communications interface. This interface allows the host to determine accurate battery status for effective system power management and for communication to the end user. A battery management solution utilizing the ISL6295 delivers both space and total system component cost savings for a wide variety of battery operated applications.

Ordering Information

PAR T

NUMBER

ISL6295CV 6295CV -20°C to 85 8 Ld TSSOP M8.173

ISL6295CV-T 6295CV -20°C to 85 8 Ld TSSOP M8.173

ISL6295CVZ (Note)

ISL6295CVZ-T (Note)

NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/ JEDEC J STD-020.

PAR T

MARKING

6295CVZ -20°C to 85 8 Ld TSSOP

TEMP

RANGE (°C) PACKAGE

(Pb-free)

PKG.

DWG. #

M8.173

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Features

• Measures, maintains, and reports all critical rechargeable battery parameters with high accuracy

• Supports Lithium Ion and Lithium Polymer battery packs

• Current measurement with 16-bit (15-bit plus sign) integrating A/D accurate to less than ±0.5% error

• Calibrated temperature measurement accurate to within ±3°C absolute using on-chip temp sensor or external thermistor

• Accumulation of charge current, discharge current, temperature, and voltage in independent 32-bit registers

• 256-byte nonvolatile EEPROM stores factory programmed, measured, and user-defined parameters

• In-system offset calibration compensates for offset error in current measurement

• Industry standard SMBus/I

C™ compatible 2-wire

communications interface

- SMBus V1.1 with PEC/CRC-8 communication

• -20°C to +85°C operating temperature range

• NTC pin can be configured as a thermistor input or GPIO

• GPAD pin can be configured as an independent A/D input or GPIO

• Flexible power operating modes allow low-power monitoring of battery conditions during system full operating and standby conditions:

- Run: Continuous Conversion; 85µA typ.

- Sample: Sample interval from 0.5-64s @ 45µA typ.

- Sample-Sleep: Sample interval from 0.5-138s min. @

20µA typ.

• Shelf-Sleep mode reduces power consumption to pack storage conditions to 300nA typ., with automatic wake-up upon pack insertion.

• Pb-free plus anneal available (RoHS compliant)

Applications

• Notebook PC, PDAs, Hand Held Devices

Pinout

ISL6295 (TSSOP)

TOP VIEW

GPAD/IO1

SCL

SDA

GND

NTC/IO0

ROSC

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

1-888-INTERSIL or 1-888-468-3774

| Intersil (and design) is a registered trademark of Intersil Americas Inc.

All other trademarks mentioned are the property of their respective owners.

ISL6295

Absolute Maximum Ratings

Supply Voltage VP. . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 10V

Input Voltage or IO Voltage . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 7V

Recommended Operating Conditions

Ambient Temperature Range. . . . . . . . . . . . . . . . . . . . -20°C to 85°C

Operating Supply Voltage (VP Pin) . . . . . . . . . . . . . . . . . 2.8V to 7V

CAUTION: Stress above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.

NOTE:

is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.

1. θ

Electrical Specifications Typical Values Are Tested at V

Are Guaranteed Under the Recommended Operating Conditions., Unless Otherwise Noted.

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS

DC CHARACTERISTICS

Supply Voltage V

Supply Current Run Mode I

Supply Current Sample Mode I

Supply Current Sample - Sleep Mode I

Supply Current Shelf Sleep Mode I

Input Low Voltage IO0, IO1 V

Input High Voltage IO0, IO1 V

GPIO Input Low Current Pull-up mode I

Leakage Current IO pin programmed as outputs or inputs without pullup

Output low voltage for IO0, IO1 V

Output high voltage for IO0 configured as push-pull

Thermistor Output Current I

Input Low Voltage for SMBus pins V

Input High Voltage for SMBus pins V

Output Low Voltage for SMBus pins V

Output High Voltage for SMBus pins V

Input leakage current SMBus pins I

AC CHARACTERISTICS (T

Internal main oscillator frequency f

Internal auxiliary oscillator frequency f

Accumulator Time Base Accuracy (internal 2Hz clock)

Internal A/D operating clock f

= -20°C to +85°C; VP = 3.0V to 7.0V; ROSC = 221kΩ ± 0.1%)

DDINS

DDSLP

DDSSLP

IL-IO0PU

OL-IO

OH-IO

IL-SMB

IH-SMB

OL-SMBIPULLUP

OH-SMB

LEAK-SMB

L-IO

NTC

AUX

ACC

A/D

For SMBus and register access 2.8 7.0 V

For EEPROM write 3.3 7.0 V

For guaranteed analog parametrics 3.0 7.0 V

A/D Active (Note 1) 85 120 µA

A/D Inactive (Notes 1, 2) 45 85 µA

Sample -Sleep Mode (Note 1) 20 40 µA

Shelf Sleep Mode (Note 1) 400 800 nA

IOL = 0.5mA 0.4 V

IOH = 100µA2.1 V

ROSC = 221kΩ ± 0.1% 8 13 16 µA

(Note 3) 2.1 5.5 V

ROSC = 221kΩ ± 0.1% 130.8 131.5 132.2 kHz

During Run and Sample mode (Note 3)

During Sample-Sleep mode (Note 3) -10 +10 %

(Note 3) f

= 5V and ambient temperature is at 25°C, All Maximum and Minimum Values

= 4mA 0.4 V

Thermal Information

Thermal Resistance (Typical, Note 1) θ

TSSOP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Maximum Junction Temperature (Plastic Package) . . . . . . . . 120°C

Maximum Storage Temperature Range. . . . . . . . . . . -35°C to 120°C

Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300°C

0.6 V

2.4 V

7 µA

1 600 nA

0.8 V

2.0 5.5 V

-5.0 +5.0 µA

118 131 144 kHz

-0.6 +0.6 %

/4 kHz

(°C/W)

Power-on-Reset Threshold V

Delay to entry of Shelf-Sleep mode t

POR

SHELF

Voltage at VP 2.4 2.75 V

(Shent = 1 or VP < VPtrip) and (SDA and SCL go low)

10 ms

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Electrical Specifications Typical Values Are Tested at V

Are Guaranteed Under the Recommended Operating Conditions., Unless Otherwise Noted. (Continued)

= 5V and ambient temperature is at 25°C, All Maximum and Minimum Values

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS

A/D CONVERTER CHARACTERISTICS (TA = -20°C to +85°C; VP = 3.0V to 7.0V, Note 3, 4)

A/D Converter Resolution N Magnitude only (Note 5) 8 15 bits

A/D Conversion Measurement Time tconv N-bit + sign 2

A/D Converter Input Voltage Range (internal)

Internal Temperature Accuracy T

Calibrated Voltage Measurement Gain Error

ADIN

ACC

VGAIN

Differential -152 +152 mV

Single-Ended 0 309 mV

-3 3 °K

Max deviation over supply voltage and temperature range (assumed

A/D

0.60 %

(N+1)

ideal under the calibration condition)

Calibrated Current Measurement Gain Error (with ideal ZTC current sense resistor)

Calibrated Temperature Measurement Gain Error (internal sensor)

IGAIN

TEMP

Max deviation over supply voltage and temperature range (assumed ideal under the calibration condition)

Max deviation over supply voltage and temperature range (assumed

0.50 %

0.60 %

ideal under the calibration condition)

Calibrated ADC Offset Error E

VOFFSET

Max deviation over supply voltage and temperature range (assumed ideal under the calibration condition)

= 170mV 0.30 %

REF

= 340mV 0.15 %

REF

Integrated Nonlinearity Error E

INL

0.01 %

NOTES:

1. Does not include current consumption due to external loading on pins. No EEPROM access.

2. Sample mode current is specified during an A/D inactive cycle. Sample mode average current can be calculated using the formula: Average Sample Mode Supply Current = (IDDRUN + (n-1)*IDDINS)/Ns; where Ns is the programmed sample rate.

3. Guaranteed by characterization or correlation to other test.

4. The max calibrated gain and offset errors are based on a 15-bit calibration procedure to generate the calibration factors. These calibration factors are then applied to correct the ADC results.

5. Voltage is internal at A/D converter inputs. VSR is measured directly. VP and GPAD inputs are measured using internal level-translation circuitry that scales the input voltage range appropriately for the converter.

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Cell +

Cell -

CELL CONNECTION

PLACE THERMAL FUSE NEXT TO Q1 ON PCB LAYOUT

R1 1K

C1 100nF

U2 MM3077D

2 3

VDD

VSS

ISL6295

V-

COUT

DOUT

Q1 SI6880E

R2 1K

6 7

Note: Connect NTC pin to ground if thermister is not used

FIGURE 1. ISL6295 APPLICATIONS SCHEMATIC

RT1 THERMISTOR

100nFC31.0nF

221K 0.1%

2 6 5 1 7

U1 ISL6295

VP NTC ROSC GPAD GND

0.020 1%

SCL

SDA

3 4

CMSZDA5V6

680

B+

Functional Pin Descriptions

GPAD/IO1 (Pin 1)

General purpose A/D input or general purpose input/output pin. Grounded if not used.

VP (Pin 2)

Cell input connection for the positive terminal of the Li-Ion cell. Connects to the positive terminal of 1-cell series packs. VP serves as the power supply input for the ISL6295.

SCL (Pin 3)

SMBus/I2C™ clock line connection

SDA (Pin 4)

SMBus/I2C™ data line connection

ROSC (Pin 5)

External bias resistor. 221kΩ (±0.1%) oscillator reference setting resistor connected between this pin and GND.

NTC/IO0 (Pin 6)

Connection for an external temperature sensor using a thermistor. Can also be configured as an open drain general purpose input/output pin. Grounded if not used.

GND (Pin 7)

Analog and digital ground

Theory of Operation

The ISL6295 contains a complete analog "front-end" for battery monitoring as well as digital logic for control, measurement accumulation, timing, and communications. Major functions within the ISL6295 include:

• Voltage Regulator

• Precision Time Base

• Temperature Sensor

• 256 Byte NV-EEPROM

• 32 Byte general purpose SRAM

• Analog-to-Digital (A/D) Converter

• 32-bit Accumulators/Timers

•SMBus/I

Figure 2 is a block diagram of the internal circuitry of the ISL6295. Figure 1 is a schematic diagram that depicts the ISL6295 in a typical single cell Lithium-ion application. The function of each of the blocks listed above is summarized in the following sections.

C™ Communications Interface

SR (Pin 8)

Current measurement A/D input. Connects to the other terminal of a grounded current sense resistor.

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DIGITAL SECTION

32-BIT

ACCUMULATORS/

TIMERS

REGISTERS

CONTROL

AND

STATUS

GPAD/IO1NTC/IO0

FIGURE 2. BLOCK DIAGRAM

SDA

SCL

256

EEPROM

COMM

INTERFACE

Internal Voltage Regulator

The ISL6295 incorporates an internal voltage regulator that supports 1-cell series lithium pack configurations. The internal regulator draws power directly from the VP input. No other external components are required to regulate circuit voltage.

Precision Time Base

The integrated precision time base is a highly accurate RC oscillator that provides precise timing for the sigma-delta A/D and for the on-chip elapsed time counters without the need for an external crystal. This time base is trimmed during manufacturing to a nominal frequency of 131.072kHz.

Temperature Sensor

An integrated temperature sensor is provided that can eliminate the need for an external thermistor. As an option, a connection is provided for an external thermistor for applications where the battery pack is physically located at a distance from the ISL6295.

EEPROM

256 bytes of EEPROM memory is incorporated for storage of non-volatile parameters such as cell models for use with Intersil’s host driver firmware. An an initialization block with values that are loaded into ISL6295 registers following a power on condition. Included in this block is 16 bytes for battery ID information.

RAM

32 bytes of general purpose RAM memory are provided for storage of temporary parameters.

ANALOG SECTION

VOLTAGE

REFERENCE AND

TEMP SENSOR

16-BIT SIGMA-DELTA INTEGRATING

A/D CONVERTER

RUN

OSCILLATOR

SLEEP

OSCILLATOR

VOLTAGE

REGULATOR

ANALOG

INPUT MUX

ROSC GND

A/D Converter

The ISL6295 incorporates an integrating sigma-delta A/D converter together with an analog MUX that has inputs for charge and discharge currents, pack voltage, GPAD voltage, the on-chip temperature sensor, and an off-chip thermistor. The converter can be programmed to perform a conversion with magnitude resolution of 8- to 15-bits while using either a single 170mV or 340mV reference.

32-Bit Accumulator/Timers

The ISL6295 incorporates four 32-bit accumulators and four 32-bit elapsed time counters. The Discharge Current Accumulator (DCA) and the Charge Current Accumulator (CCA) are intended to record discharge and charge capacity values. The Discharge Time Counter (DTC) and the Charge Time Counter (CTC) are intended to maintain the total discharge time and charge time. Accumulated charge and discharge values can be used to determine state of charge of the battery as well as cycle count information. With information provided by the elapsed time counters, average charge and discharge currents over an extended period of time can be calculated.

SMBus/I2C™ Communications Interface

This communications port for the ISL6295 is a 2-wire industry-standard SMBus/I status, and data is read or written from the host system via this interface.

C™ interface. All commands,

A/D and Accumulator/Timer Operation

A/D CONVERSION CYCLE

When the A/D converter is enabled and active, it repeatedly performs a cycle of 1 to 8 conversions as programmed by

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the user through 8 A/D control registers. These registers determine the input source, conversion resolution, reference voltage, and sequence of conversions during an A/D conversion cycle. During the cycle, the A/D logic accesses each register in sequence and performs the conversion specified by the bits within the registers. Each register contains an enable bit, a resolution field, a select bit for single-ended (340mV reference) or differential (170mV reference) conversion, and a select field for the analog input multiplexer. The result from each conversion is stored in one of eight corresponding 16-bit result registers.

If the “Enable” bit is set within a control register, a conversion will be performed. If it is disabled, that conversion will be skipped and the logic will move on to the next register. In this manner, the user can specify a sequence of conversions that will be performed during each A/D cycle.

As stated above, the input source for each of the registers is programmable. The 3-bit MUX field within each control register selects one of seven possible input sources for the A/D conversion. The list of input sources is as follows:

• Charge/discharge Current (Voltage from SR pin to GND)

• Internal temperature sensor

• External thermistor (Constant current source on NTC pin)

• Battery pack voltage

• Reserved

• General purpose A/D voltage

• ADC offset (Conversion performed with ADC input internally shorted to ground) to determine offset error associated with the converter

However, the accumulator/timer functions are “hard-wired” to specific A/D result registers. For this reason, the control/ result registers are given names which indicate their primary intended usage:

A/D

CONTROL REGISTER

0 Ictrl Ires Battery Pack Current

1 ITctrl ITres Internal Temperature Sensor

2 ETctrl ETres External Temperature

3 VPctrl VPres Battery Pack Voltage

4 Reserved

5 GPADctrl GPADres General Purpose A/D Input

6 OFFSctrl OFFSres Internal ADC offset voltage

7 AUXctrl AUXres Any

RESULT

INTENDED

INPUT SOURCE

(via sense resistor)

Sensor

(with input grounded)

The 3-bit “resolution” field in each A/D control register determines the magnitude resolution of the conversion, from a minimum of 8-bits to a maximum of 15-bits. The time required to complete the conversion is a function of the number of bits of resolution selected. The conversion time can be calculated as follows:

= 30.52µs * 2

ADC

(N+1)

where “N” is the number of bits of magnitude resolution selected

The “Ref” bit selects either a differential or single-ended conversion. For differential conversions, the 170mV reference is used. For single-ended conversion the 340mV reference is selected. Single-ended conversions would be used for measurements of pack voltage while a differential conversion is required for current measurement.

The value of the LSB in the result register is as follows:

For single-ended conversion, A/D LSB = 340 mV/2

= 10.38µV

For differential conversion, A/D LSB = 170 mV/2

= 5.19µV

For both differential and single-ended conversions, the result value is given in sign-magnitude format (i.e. a sign bit and 15 magnitude bits). When N less than 15 is selected, the conversion result is padded with trailing zeroes. Note that

15 14 0

S Magnitude

the single-ended reference should not be used for a negative measurement. Though the sign-magnitude value presented may still look valid, the accumulator will not be able to interpret the result for proper accumulation.

CURRENT MEASUREMENT

Charge and discharge currents are measured using a 5 to 600mΩ sense resistor that is connected between the SR and GND pins. The sense resistor value chosen must accommodate the system’s lowest and highest expected charge and discharge currents, including suspend and standby currents, while maintaining a voltage of no more than +

152mV presented at the SR pin.

In order to perform charge and discharge current measurements, the Ictrl register must be programmed with the SR pin as the analog input source. If charge and discharge accumulation is desired, the Ictrl and corresponding Ires registers should be used to select current measurement since the DCA, DTC, CCA, and CTC registers are updated by the measurement results from the Ires register.

When a 20mΩ sense resistor is used, the value of the LSB in units of current is:

5.19µV/20mΩ = 259.5µA

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Ictrl programming in a typical application is as follows:

BIT(s) NAME VALUE FUNCTION

7 EN 1 ENABLES A/D CONVERSION

6-4 Res 111 Selects 15-bit resolution

3 Ref 0 Selects 170mV Reference

2-0 Sel 000 Selects VSR as ADC input

VOLTAGE MEASUREMENTS

An analog multiplexer and divider network is provided to support measurement of battery pack voltages. The A/D control registers VPctrl and GPADctrl are used to specify the measurement to be made. In typical applications, voltage measurement a pack level is done using the 340mV reference and a 10-bit magnitude resolution.

The value of the LSB in a pack voltage measurement using the 340mV reference voltage and 15 bit resolution is given by the formula:

LSB = 10.2V/215 = 311.3µV

PAC K

VPctrl programming in a typical application is as follows:

BIT(s) NAME VALUE FUNCTION

7 En 1 Enables A/D conversion

6-4 Res 010 Selects 10-bit resolution

3 Ref 1 Selects 340mV Reference

2-0 Sel 011 Selects Vpack (VP) as ADC input

The input source fields for the VPctrl, and GPADctrl registers must be programmed to select the pack voltage VP and the general purpose A/D input voltage GPAD in order for these registers to control their intended measurements.

The measurable input range for VP is from 2.8V to 7V. The measurable input range for GPAD is from 0V to 6.2V.

TEMPERATURE MEASUREMENTS

A/D input channels are provided for temperature measurement using either the internal temperature sensor or an external thermistor.

Defined within the ITctrl register is settings for the reference utilized and the resolution desired for measurement of temperature using the internal temperature sensor. Due to the voltage output range of the temperature sensor, the 340mV reference must be selected.

The temperature measurement given by the internal temperature sensor is derived using the following equation:

IT(°C) = (ITres – 22421)/78.95 °C

Typically, 10-bit resolution is selected, which results in the following temperature measurement resolution:

IT(∆) = 0.405°C/LSB

For temperature measurement using an external sensor, the NTC pin sources a current of 12.5µA. For proper operation, an industry standard 10kΩ at 25°C negative temperature coefficient (NTC) device with a proper resistance range should be connected between the NTC and GND pins. The NTC reference output is only enabled during an external temperature measurement in order to minimize power consumption.

Defined within the ETctrl register are settings for the reference utilized and the resolution desired for measurement of temperature using the external temperature sensor. The accuracy of temperature measurement using the external thermistor is directly determined by the characteristic of the NTC device used. It is suggested that temperature measurements be thoroughly characterized to extract the best-fit equation for temperature determination.

Internal to the ISL6295, a voltage inverter is provided to translate the NTC voltage to a PTC voltage so that a larger A/D conversion result would correspond to a higher temperature reading. The actual voltage presented to the ADC is as follows:

= V

ADC

where V

- V

REF

NTC

is the reference voltage selected.

For typical NTC devices, the 340mV reference should be used to cover the expected operational temperature range of the battery pack. For a NTC with a 10kΩ resistance at 25°C, the voltage at the NTC pin will be 125mV, which corresponds to an ADC input of (340-125)mV = 215mV. The expected conversion result would be 215/340 * 2

= 20721.

OFFSET COMPENSATION

The host software can perform offset compensation by using an offset measurement value read from the ISL6295. When the offset calibration is enabled within the OFFSctrl register, the converter input is internally shorted to ground and an A/D conversion is performed at the specified resolution. The offset value is stored in the OFFSres register.

ACCUMULATION/TIMING

Each of the four 32-bit accumulator registers is assigned a fixed “source” A/D result register. When the accumulator is

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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. ACCUMULATOR NAME SOURCE

DCAIres Discharge Current Accumulator Ires (Sign bit = 1)

CCA Charge Current Accumulator Ires (Sign bit = 0)

TA Temperature Accumulator ITres or ETres

GPA D A G PAD Acc u m ulato r GPA D r e s

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) = (V

/215) µV * 0.5s

REF

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/R

SENSE

= 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, V on the VP pin rises above the V

POR

will initialize itself by loading the internal counters, data and control registers with default values pre-written into the nonvolatile 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 (V V

threshold. Run Mode can also be entered from the

POR

) applied to the VP pin rises above the

PAC K

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 V

threshold and Sample, Sample-

POR

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

. When the voltage

POR

threshold, the ISL6295

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