Rainbow Electronics DS2784 User Manual
Ds2784, General description, Applications
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REV:
092507
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
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.
DS2784
1-Cell Stand-Alone Fuel Gauge IC
with
Li+ Protector and SHA-1 Authentication
www.maxim-ic.com
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
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
Document Outline
- The model is constructed with all points normalized to the fully charged state at +40°C. All values are stored in the cell parameter EEPROM block. The +40°C full value is stored in µVhr with an LSB of 6.25µVhr. The +40°C active empty value is stored as a percentage of +40°C full with a resolution of 2-10. Standby empty at +40°C is, by definition, zero and, therefore, no storage is required. The slopes (derivatives) of the 4 segments for each model curve are stored in the cell parameter EEPROM block as ppm/°C. The breakpoint temperatures of each segment are stored there also (see Application Note 3584: Storing Battery Fuel Gauge Parameters in DS2780 for more details on how values are stored). An example of data stored in this manner is shown in Table 6.
- This command is structured the same as the compute MAC without ROM ID, except that the ROM ID is included in the message block. With the ROM ID unique to each DS2784 included in the MAC computation, the MAC is unique to each token. See White Paper 4: Glossary of 1-Wire SHA-1 Terms, for more information. See Figure 9 for command timing.