MAXIM DS2784 User Manual

www.maxim-ic.com

1-Cell Stand-Alone Fuel Gauge IC with

Li+ Protector and SHA-1 Authentication

DS2784

GENERAL DESCRIPTION

The DS2784 operates from 2.5V to 4.6V for integration
in battery packs using a single lithium-ion (Li+) or Li+
polymer cell. Available capacity is reported in mAh and
as a percentage. Safe operation is ensured with the
included Li+ protection function and SHA-1-based
challenge-response authentication.

Precision measurements of voltage, temperature, and
current, along with cell characteristics and application
parameters are used to estimate capacity. The
available capacity registers report a conservative
estimate of the amount of charge that can be removed
given the current temperature and discharge rate.

In addition to the nonvolatile (NV) storage for cell
compensation and application parameters, 16 bytes of
EEPROM memory is made available for the exclusive
use of the host system and/or pack manufacturer. This
facilitates battery lot and date tracking or NV storage of
system or battery usage statistics.

A 1-Wire

®

interface provides serial communication at
16kbps or 143kbps to access data registers, control
registers, and user memory. Additionally, 1-Wire
communication enables challenge-response pack
authentication using SHA-1 as the hash algorithm in a
hash-based message authentication code (HMAC)
authentication protocol.

APPLICATIONS

Smartphones/PDAs

FEATURES

 Precision Voltage, Temperature, and Current

Measurement System

 Available Capacity Estimated from Coulomb

Count, Discharge Rate, Temperature, and Cell
Characteristics

 Estimates Cell Aging Using Learn Cycles
 Uses Low-Cost Sense Resistor
 Allows for Calibration of Gain and

Temperature Coefficient

 Li+ Safety Circuitry—Overvoltage,

Undervoltage, Overcurrent, Short-Circuit
Protection

 Programmable Safety Thresholds for

Overvoltage and Overcurrent

 Authentication Using SHA-1 Algorithm and

64-Bit Secret

 32-Byte Parameter EEPROM
 16-Byte User EEPROM
 Dallas 1-Wire Interface with 64-Bit Unique ID
 Tiny, Pb-Free, 14-Pin TDFN Package Embeds

Easily in Battery Packs Using Thin Prismatic
Cells

PIN CONFIGURATION

Digital Still and Video Cameras
Cordless VOIP Phones
Portable GPS Navigation

Modes and commands are capitalized for clarity.

1-Wire is a registered trademark of Dallas Semiconductor, a wholly
owned subsidiary of Maxim Integrated Products, Inc.

ORDERING INFORMATION

PART TEMP RANGE TOP MARK PIN PACKAGE

DS2784G+ -40°C to +85°C DS2784 14 TDFN (3mm x 5mm)
DS2784G+T&R -40°C to +85°C DS2784 14 TDFN (3mm x 5mm)

+ Denotes a lead-free package.
T&R = tape and reel

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

ABSOLUTE MAXIMUM RATINGS

Voltage Range on PLS Pin Relative to VSS -0.3V to +18V
Voltage Range on CP Pin Relative to V
Voltage Range on DC Pin Relative to V
Voltage Range on CC Pin Relative to V
Voltage Range on All Other Pins Relative to V
Maximum Voltage Range on V

Pin Relative to VDD V

IN

-0.3V to +12V

SS

-0.3V to (CP + 0.3V)

SS

V

SS

-0.3V to +6.0V

SS

- 0.3V to CP + 0.3V

DD

+ 0.3V

DD

Continuous Sink Current, PIO, DQ 20mA
Continuous Sink Current, CC, DC 10mA
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature (10s) See IPC/JEDEC J-STD-020

*This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation

sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.

ELECTRICAL CHARACTERISTICS

(VDD = 2.5V to 4.6V, TA = -20°C to +70°C, unless otherwise noted. Typical values are at TA = +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage VDD (Note 1) 2.5 4.6 V

I

Sleep mode 1 4

DD0

Sleep mode, V
0°C to +50°C

Active mode 85 125

Active mode during SHA
computation

Supply Current

I

I

I

DD1

DD2

DD3

Temperature Accuracy -3 +3
Temperature Resolution 0.125
Temperature Range -128.000 +127.875

4.0 ≤ V
V

Voltage Accuracy, VIN

IN

2.5 ≤ V
V

IN

≤ 4.6,

IN

≤ VDD + 0.3V

≤ 4.6V,

IN

≤ VDD + 0.3V
Voltage Resolution, VIN 4.88 mV
Voltage Range, VIN 0 4.99 V
Input Resistance, VIN 15

Current Resolution 1.56

= 2.5V

DD

0.4 1.5

300 500

-30 30

-50 +50

μA

μA

o

C

mV

MΩ

μV

Current Full Scale -51.2 +51.2 mV

Current Gain Error -1 +1

Current Offset (Notes 2, 3, 4) -15 +25

Accumulated Current Offset (Notes 2, 3, 4) -360 0

% full
scale

μV

μVh/day

0ºC ≤ TA ≤ +50ºC -2 +2

Time Base Error

%

-3 +3

CP Output Voltage VCP ICC + I

CP Startup Time t

Output High: CC, DC

Output Low: CC V

Output Low: DC V

V
V

SCP

OHCC

OHDC

OLCC

OLDC

CE = 0, DE = 0,
C

CP

IOH = -100µA (Note 5) V

IOL = 100µA VDD + 0.1 V

IOL = 100µA 0.1 V

= 0.9µA 8.50 9.25 10.00 V

DC

= 0.1µF, Active mode

200 ms

- 0.4 V

CP

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DQ, PIO Voltage Range -0.3 +5.5 V

DQ, PIO Input-Logic High VIH 1.5 V

DQ, PIO Input-Logic Low VIL 0.6 V

DQ, PIO Output-Logic Low VOL IOL = 4mA 0.4 V

DQ, PIO Pullup Current IPU

DQ, PIO Pulldown Current IPD

Sleep mode,
V

= VDD - 0.4V

PIN

Active mode,
V

= 0.4V

PIN

0.2

0.2

μA

μA

DQ Input Capacitance CDQ 50 pF

DQ Sleep Timeout t

PIO, DQ Wake Debounce t

DQ < VIL 2 9 s

SLEEP

Sleep mode 100 ms

WDB

SHA-1 COMPUTATION TIMING

Computation Time t

30 ms

SHA

ELECTRICAL CHARACTERISTICS: Protection Circuit

(VDD = 2.5V to 4.6V, TA = 0°C to +50°C, unless otherwise noted. Typical values are at TA = +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Overvoltage Detect VOV

Charge-Enable Voltage VCE Relative to VOV -75 -100 -125 mV

Undervoltage Detect VUV 2.40 2.45 2.50 V

Overcurrent Detect: Charge V

Overcurrent Detect: Discharge V

COC

DOC

Short-Circuit Current Detect VSC

VOV = 11000b 4.457 4.482 4.507

V

= 00011b 4.252 4.277 4.302

OV

OC = 11b -57 -72 -87

OC = 00b -15.5 -23.5 -31.5

OC = 11b 76 96 116

OC = 00b 23.5 35.5 47.5

SC = 1b 240 300 360 mV

SC = 0b 120 150 180 mV

V

mV

mV

Overvoltage Delay t

Undervoltage Delay t

Overcurrent Delay t

Short-Circuit Delay t

(Note 6) 425 1150 ms

OVD

(Notes 6, 7) 84 680 ms

UVD

8 10 12 ms

OCD

80 120 160

SCD

μs

Test Threshold VTP COC, DOC conditions 0.3 0.8 1.5 V

Test Current I

PLS Pulldown Current I

SC, COC, DOC condition 10 20 40

TST

Sleep mode 30 200 600

PPD

μA

μA

VUV condition,

PLS

= 1V

PLS

= 2V

= 15V,

2.5 5.0 10.00 mA

= 4.2V,

Recovery Current IRC

max: V
V

DD

min: V
V

DD

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

EEPROM RELIABILITY SPECIFICATION

(VDD = 2.5V to 5.5V, TA = -20°C to +70°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

EEPROM Copy Time t

EEPROM Copy Endurance N

10 ms

EEC

TA = +50°C 50,000 cycles

EEC

ELECTRICAL CHARACTERISTICS: 1-Wire Interface, Standard

(VDD = 2.5V to 5.5V, TA = -20°C to +70°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Time Slot t

Recovery Time t

Write-0 Low Time t

Write-1 Low Time t

Read-Data Valid t

Reset-Time High t

Reset-Time Low t

Presence-Detect High t

Presence-Detect Low t

60 120

SLOT

1

REC

60 120

LOW0

1 15

LOW1

15

RDV

480

RSTH

480 960

RSTL

15 60

PDH

60 240

PDL

ELECTRICAL CHARACTERISTICS: 1-Wire Interface, Overdrive

(VDD = 2.5V to 5.5V, TA = -20°C to +70°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

μs

μs

μs

μs

μs

μs

μs

μs

μs

Time Slot t

Recovery Time t

Write-0 Low Time t

Write-1 Low Time t

Read-Data Valid t

Reset-Time High t

Reset-Time Low t

Presence-Detect High t

Presence-Detect Low t

6 16

SLOT

1

REC

6 16

LOW0

1 2

LOW1

2

RDV

48

RSTH

48 80

RSTL

2 6

PDH

8 24

PDL

Note 1: All voltages are referenced to V
Note 2: Factory-calibrated accuracy. Higher accuracy can be achieved by in-system calibration by the user.
Note 3: Accumulation bias and offset bias registers set to 00h. NBEN bit set to 0.
Note 4: Parameters guaranteed by design.
Note 5: CP pin externally driven to 10V.
Note 6: Overvoltage and undervoltage delays (t

Note 7: t

Active mode.

MIN determined by stepping the voltage on VIN from VUV + 250mV to VUV - 250mV.

UVD

.

SS

, t

) are reduced to 0s if the OV or UV condition is detected within 100ms of entering

OVD

UVD

μs

μs

μs

μs

μs

μs

μs

μs

μs

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

TYPICAL OPERATING CIRCUIT

PIN DESCRIPTION

PIN NAME FUNCTION

1 VDD Power-Supply Input. Chip supply input. Bypass with 0.1µF to VSS.
2 CTG Connect to Ground
3 VSS Device Ground. Chip ground and battery-side sense resistor input.

4 VIN

5, 9, 10 N.C. No Connection

6 PLS

7 CC Charge Control. Charge FET control output.
8 DC Discharge Control. Discharge FET control output.

11 DQ

12 SNS

13 CP Charge Pump Output. Bypass with 0.1µF to VSS.
14 PIO Programmable I/O Pin. Can be configured as wake input.

PAD PAD Exposed Pad. Connect to V

Battery Voltage-Sense Input. Connect to positive cell terminal through decoupling
network.

Pack Plus Terminal-Sense Input. Used to detect the removal of short-circuit, discharge
overcurrent, and charge overcurrent conditions.

Data Input/Output. Serial data I/O, includes weak pulldown to detect battery disconnect
and can be configured as wake input.
Sense Resistor Connection. Pack minus terminal and pack-side sense resistor sense
input.

or float.

SS

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

DETAILED DESCRIPTION

The DS2784 functions as an accurate fuel gauge, Li+ protector, and SHA-1-based authentication token. The fuel
gauge provides accurate estimates of remaining capacity and reports timely voltage, temperature, and current­measurement data. Capacity estimates are calculated from a piecewise-linear model of the battery performance
over load and temperature, and system parameters for full and empty conditions. The algorithm parameters are
user programmable and can be modified in pack. Critical capacity and aging data are periodically saved to
EEPROM in case of loss of power due to a short circuit or deep depletion.

The Li+ protection function ensures safe, high-performance operation. nFET protection switches are driven with a
9V charge pump that increase gate drive as the cell voltage decreases. The high-side topology preserves the
ground path for serial communication while eliminating the parasitic charge path formed when the fuel gauge IC is
located inside the protection FETs in a low-side configuration. The thresholds for overvoltage, overcurrent, and
short-circuit current are user programmable for easy customization to each cell and application.

The 32-bit wide SHA-1 engine with 64-bit secret and 64-bit challenge words resists brute force and other attacks
with financial-level HMAC security. The challenge of managing secrets in the supply chain is addressed with the
compute next secret feature. The unique serial number or ROM ID can be used to assign a unique secret to each
battery.

BLOCK DIAGRAM

VOLTAGE

(VIN - VSSA)

TEMPERATURE

10-Bit + sign

ADC/MUX

VIN

LITHIUM ION

PROTECTOR

UV, CD

POWER MODE

Control

PLS

CC

DC

CP

VDD

FET DRIVERS

CHARGE

PUMP

VDD_INT

FuelPack™
FuelPack™

Algorithm

ALGORITHM

Control and

Status Registers

32 Byte

Parameter

EEPROM

16 Byte User

EEPROM

CURRENT

(VSS - SNS)

PRECISION

ANALOG

OSCILLATOR

PIO Logic

1-Wire Interface

15-Bit + sign

ADC

VREF

WKP, WKD

Pin Drivers

and Pwr

Switch

Control

SNS

VSS

PIO

DQ

DS2784

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

POWER MODES

The DS2784 has two power modes: Active and Sleep. On initial power-up, the DS2784 defaults to Active mode. In
Active mode, the DS2784 is fully functional with measurements and capacity estimation registers continuously
updated. The protector circuit monitors the battery voltages and current for unsafe conditions. The protection FET
gate drivers are enabled when conditions are deemed safe. Also, the SHA-1 authentication function is available in
Active mode. When a SHA-1 computation is performed, the supply current increases to I
the DS2784 conserves power by disabling measurement and capacity estimation functions, but preserves register
contents. Gate drive to the protection FETs is disabled in Sleep. And the SHA-1 authentication feature is not
operational.

Sleep mode is entered under two different conditions: bus low and undervoltage. An enable bit makes entry into
Sleep optional for each condition. Sleep mode is not entered if a charger is connected (V
charge current of 1.6mV / R
connection and V

≥ VUV or a low to high transition on DQ.

IN

The bus-low condition, where the DQ pin is low for t
1-Wire bus pullup voltage, V

is measured from SNS to VSS. The DS2784 exits Sleep mode upon charger

SNS

, indicates pack removal or system shutdown in which the

SLEEP

, is not present. The power mode (PMOD) bit must be set to enter Sleep when a

PULLUP

bus-low condition occurs. After the DS2784 enters Sleep due to a bus-low condition, it is assumed that no charge
or discharge current will flow and that coulomb counting is unnecessary.

The second condition to enter Sleep is an undervoltage condition, which reduces battery drain due to the DS2784
supply current and prevents over discharging the cell. The DS2784 transitions to Sleep if the V
than V
that is, with DQ either high or low for t

(2.45V typical) and the undervoltage enable (UVEN) bit is set. The 1-Wire bus must be in a static state,

UV

. The DS2784 transitions from UVEN Sleep to Active mode when DQ

SLEEP

changes logic state.
The DS2784 has the “power switch” capability for waking the device and enabling the protection FETs when the

host system is powered down. A simple dry-contact switch on the PIO pin or DQ pin can be used to wake up the
battery pack. The power switch function is enabled using the PSPIO and PSDQ configuration bits in the control
register. When PSPIO or PSDQ is set and a Sleep condition is satisfied, the PIO and DQ pins pull high weakly,
then become armed to detect a low-going transition. A 100ms debounce period filters out glitches that can be
caused when a sleeping battery is inserted into a system.

DD3

for t

PLS

. In Sleep mode,

SHA

> VDD + 50mV) or if a

voltage is less

IN

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

Figure 1. Sleep Mode State Diagram

CONTROL REGISTER FORMAT

All control register bits are read and write accessible. The control register is recalled from parameter EEPROM
memory at power-up. Register bit values can be modified in shadow RAM after power-up. Power-up default values
are saved using the Copy Data command.

ADDRESS 60h

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

NBEN UVEN PMOD RNAOP 0 PSPIO PSDQ X

NBEN—Negative Blanking Enable. A value of 1 enables blanking of negative current values up to 25μV. A value of

0 disables blanking of negative currents. The power-up default of NBEN = 0.

UVEN—Undervoltage Enable. A value of 1 allows the DS2784 to enter Sleep mode when the voltage register value

is less than V

and DQ is stable at either logic level for t

UV

. A value of 0 disables transitions to Sleep mode in an

SLEEP

undervoltage condition.

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

PMOD—Power Mode Enable. A value of 1 allows the DS2784 to enter Sleep mode when DQ is low for t

SLEEP

. A

value of 0 disables DQ related transitions to Sleep mode.

RNAOP—Read Net Address Op Code. A value of 0 selects 33h as the op code value for the Read Net Address

command. A value of 1 selects 39h as the Read Net Address opcode value.

0—Reserved bit, must be programmed to 0 for proper operation.

PSPIO—Power-Switch PIO Enable. A value of 1 enables the PIO pin as a power-switch input. A value of 0 disables

the power-switch input function on PIO pin. This control is independent of the PSDQ state.

PSDQ—Power-Switch DQ Enable. A value of 1 enables the DQ pin as a power-switch input. A value of 0 disables

the power-switch input function on DQ pin. This control is independent of the PSPIO state.

X—Reserved Bit.

Li+ PROTECTION CIRCUITRY

During Active mode, the DS2784 constantly monitors SNS, VIN, and V
(overcharge), undervoltage (overdischarge), and excessive charge and discharge currents (overcurrent, short
circuit). Table 1 summarizes the conditions that activate the protection circuit, the response of the DS2784, and the
thresholds that release the DS2784 from a protection state.

Table 1. Li+ Protection Conditions and DS2784 Responses

CONDITION

THRESHOLD DELAY RESPONSE

Overvoltage V

Undervoltage VIN < V

Overcurrent, Charge V

Overcurrent, Discharge V

Short Circuit V

Note 1: All voltages are with respect to V
Note 2: CC pin driven to V

Note 3: If V

Note 4: With test current I
Note 5: With test current I

< VUV when charger connection is detected, release is delayed until VIN ≥ VUV. The recovery charge path provides an internal

IN

current limit (I

OLCC

) to safely charge the battery.

RC

TST

TST

> V

IN

OV

UV

< V

SNS

COC

> V

SNS

DOC

> V

SNS

SC

.

(VDD) for CC off response. DC pin driven to V

flowing from PLS to V

flowing from V

SS

to PLS (pullup on PLS).

DD

Overvoltage. If the voltage on V

delay (t

), the CC pin is driven low to shut off the external-charge FET, and the OV flag in the protection register

OVD

exceeds the overvoltage threshold (VOV) for a period longer than overvoltage

IN

is set. The DC output remains high during overvoltage to allow discharging. When V
threshold, V
V

< VCE if a discharge condition persists with V

IN

, the DS2784 turns the charge FET on by driving CC high. The DS2784 drives CC high before

CE

Undervoltage. If V

(t

), the DS2784 shuts off the charge and discharge FETs and sets the UV flag in the protection register. If UVEN

UVD

drops below the undervoltage threshold (VUV) for a period longer than undervoltage delay

IN

is set, the DS2784 also enters Sleep mode. The DS2784 provides a current-limited recovery charge path (I
PLS to V
0 ≤ V

DD

monitoring V

to gently charge severely depleted cells. The recovery charge path is enabled when

DD

< (VOV - 100mV). Once VDD reaches 2.45V (typ), the DS2784 returns to normal operation and begins

. Once V

IN

> VUV, the DS2784 transitions from Sleep to Active mode and the CC and DC outputs are

IN

driven high to turn on the charge and discharge FETs.

9 of 37

ACTIVATION

t

OVD

t

UVD

t

OCD

t

OCD

t

SCD

(pulldown on PLS) enabled.

SS

≥ 1.2mV and VIN < VOV.

SNS

CC Off, DC Off,

CC Off, DC Off

OLDC

to protect the battery from overvoltage

PLS

(2)

CC Off

Sleep Mode

DC Off

DC Off

(VSS) for DC off response.

RELEASE THRESHOLD

VIN < VCE or (V

and V

< VOV)

IN

> V

V

PLS

(charger connected)

< VDD - V

V

PLS

(charger removed)

> VDD - V

V

PLS

(load removed)

> VDD - V

V

PLS

(load removed)

falls below the charge enable

IN

> 1.2mV

SNS

(3)

IN

TP

TP

TP

(4)

(5)

(5)

RC

) from

DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

Overcurrent, Charge Direction (COC). Charge current develops a negative voltage on V

V

is less than the charge overcurrent threshold (V

SNS

) for a period longer than overcurrent delay (t

COC

with respect to VSS. If

SNS

OCD

), the
DS2784 shuts off both external FETs and sets the COC flag in the protection register. The charge current path is
not re-established until the voltage on the PLS pin drops below V
(I

) from PLS to VSS to pull PLS down in order to detect the removal of the offending charge current source.

TST

- VTP. The DS2784 provides a pulldown current

DD

Overcurrent, Discharge Direction (DOC). Discharge current develops a positive voltage on V

V

SS

. If V

exceeds the discharge overcurrent threshold (V

SNS

) for a period longer than t

DOC

, the DS2784 shuts off

OCD

with respect to

SNS

the external discharge FET and sets the DOC flag in the protection register. The discharge current path is not re­established until the voltage on PLS rises above V

- VTP. The DS2784 provides a test current (I

DD

) from VDD to

TST

PLS to pull PLS up in order to detect the removal of the offending low-impedance load.

Short Circuit. If V

exceeds short-circuit threshold VSC for a period longer than short-circuit delay (t

SNS

SCD

), the
DS2784 shuts off the external discharge FET and sets the DOC flag in the protection register. The discharge
current path is not re-established until the voltage on PLS rises above V
current of value (I

) from VDD to PLS to pull PLS up in order to detect the removal of the short circuit.

TST

- VTP. The DS2784 provides a test

DD

Figure 2. Li+ Protection Circuitry Example Waveforms

Summary. All the protection conditions previously described are logic ANDed to affect the CC and DC outputs.

CC = (Overvoltage) AND (Undervoltage) AND (Overcurrent, Charge Direction)

AND (Protection Register Bit CE)

DC = (Undervoltage) AND (Overcurrent, Either Direction) AND (Short Circuit)

AND (Protection Register Bit DE )

PROTECTION REGISTER FORMAT

The protection register reports events detected by the Li+ safety circuit on bits 2 to 7. Bits 0 and 1 are used to
disable the charge and discharge FET gate drivers. Bits 2 to 7 are set by internal hardware only. Bits 2 and 3 are

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

cleared by hardware only. Bits 4 to 7 are cleared by writing the register with a 0 in the bit position of interest. Writing
a 1 to bits 4 to 7 has no effect on the register. Bits 0 and 1 are set on power-up and a transition from Sleep to
Active modes. While in Active mode, these bits can be cleared to disable the FET gate drive of either or both FETs.
Setting these bits only turns on the FETs if there are no protection faults.

ADDRESS 00h

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

OV

UV COC DOC CC DC CE DE

OV—Overvoltage Flag. OV is set to indicate that an overvoltage condition has been detected. The voltage on V

has persisted above the V

threshold for tOV. OV remains set until written to a 0 or cleared by a power-on reset or

OV

IN

transition to Sleep mode.

UV—Undervoltage Flag. UV is a read-only mirror of the UVF flag located in the status register. UVF is set to

indicate that V

IN

< V

. The UVF bit must be written to 0 to clear UV and UVF.

UV

COC—Charge Overcurrent Flag. COC is set to indicate that an overcurrent condition has occurred during a charge.

The sense-resistor voltage has persisted above the V

threshold for tOC. COC remains set until written to a 0,

COC

cleared by a power-on reset, or transition to Sleep mode.

DOC—Discharge Overcurrent Flag. DOC is set to indicate that an overcurrent condition has occurred during a

discharge. The sense-resistor voltage has persisted above the V

threshold for tOC. DOC remains set until written

DOC

to a 0, cleared by a power-on reset, or transition to Sleep mode.

CC—Charge Control Flag. CC indicates the logic state of the CC pin driver. CC flag is set to indicate CC high. CC

flag is cleared to indicate CC low. CC flag is read only.

DC—Discharge Control Flag. DC indicates the logic state of the DC pin driver. DC flag is set to indicate DC high.

DC flag is cleared to indicate DC low. DC flag is read only.

CE—Charge Enable Bit. CE must be set to allow the CC pin to drive the charge FET to the on state. CE acts as an

enable input to the safety circuit. If all safety conditions are met AND CE is set, the CC pin drives to V

. If CE is

CP

cleared, the CC pin is driven low to disable the charge FET.

DE—Discharge Enable Bit. DE must be set to allow the DC pin to drive the discharge FET to the on state. DE acts

as an enable input to the safety circuit. If all safety conditions are met AND DE is set, the DC pin drives to V

CP

. If

DE is cleared, the DC pin is driven low to disable the charge FET.

PROTECTOR THRESHOLD REGISTER FORMAT

The 8-bit threshold register consists of bit fields for setting the overvoltage threshold, charge overcurrent threshold,
discharge overcurrent threshold, and short-circuit threshold for the protection circuit.

ADDRESS 7Fh

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

VOV4 VOV3 VOV2 VOV1 VOV0 SC0 OC1 OC0

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DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication

Table 2. VOV Threshold

VOV BIT FIELD VOV VOV BIT FIELD VOV

0 0 0 0 0 4.248 1 0 0 0 0 4.404

0 0 0 0 1 4.258 1 0 0 0 1 4.414

0 0 0 1 0 4.268 1 0 0 1 0 4.424

0 0 0 1 1 4.277 1 0 0 1 1 4.434

0 0 1 0 0 4.287 1 0 1 0 0 4.443

0 0 1 0 1 4.297 1 0 1 0 1 4.453

0 0 1 1 0 4.307 1 0 1 1 0 4.463

0 0 1 1 1 4.316 1 0 1 1 1 4.473

0 1 0 0 0 4.326 1 1 0 0 0 4.482

0 1 0 0 1 4.336 1 1 0 0 1 4.492

0 1 0 1 0 4.346 1 1 0 1 0 4.502

0 1 0 1 1 4.356 1 1 0 1 1 4.512

0 1 1 0 0 4.365 1 1 1 0 0 4.522

0 1 1 0 1 4.375 1 1 1 0 1 4.531

0 1 1 1 0 4.385 1 1 1 1 0 4.541

0 1 1 1 1 4.395 1 1 1 1 1 4.551

Table 3. COC, DOC Threshold

OC[1:0] BIT FIELD V

0 0 -23.5 35.5

0 1 -36 48

1 0 -48 72

1 1 -72 96

(mV) V

COC

DOC

(mV)

Table 4. SC Threshold

SC0 BIT FIELD V

0 150

1 300

SC

(mV)

VOLTAGE MEASUREMENT

Battery voltage is measured every 440ms on the VIN pin with respect to VSS. Measurements have a 0 to 4.99V
range and a 4.88mV resolution. The value is stored in the voltage register in two’s complement form and is updated
every 440ms. Voltages above the maximum register value are reported at the maximum value; voltages below the
minimum register value are reported at the minimum value.

VOLTAGE REGISTER FORMAT

MSB—ADDRESS 0Ch LSB—ADDRESS 0Dh

9

S 2

28 27 26 25 24 23 22 21 20 X X X X X

MSb LSb MSb LSb

“S”: Sign Bit(s), “X”: Reserved

Units: 4.886mV

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