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DS2764A-DS2764B-DS2764BE
High-Precision Li+ Battery Monitor with 2-Wire Interface
GENERAL DESCRIPTION The DS2764 high-precision Li+ battery monitor is a
data-acquisition, information-storage, and safety-protection device tailored for cost-sensitive battery
pack applications. This low-power device integrates precise temperature, voltage, and current
measurement, nonvolatile (NV) data storage, and Li+ protection into the small footprint of either a TSSOP
package or flip-chip package. The DS2764 is a key component in applications requiring remaining
capacity estimation, safety monitoring, and battery-specific data storage.
PIN CONFIGURATIONS
FEATURES Li+ Safety Circuit Overvoltage Protection Overcurrent/Short-Circuit Protection
Undervoltage Protection
0V Battery Recovery Charge Available in Two Configurations: Internal 25m� Sense Resistor External User-Selectable Sense Resistor
Current Measurement 12-Bit Bidirectional Measurement
Internal Sense Resistor Configuration: 0.625mA LSB and ±1.9A Dynamic Range
External Sense Resistor Configuration:
15.625�V LSB and ±64mV Dynamic Range
Current Accumulation: Internal Sense Resistor: 0.25mAhr LSB
External Sense Resistor: 6.25�Vhr LSB
Voltage Measurement with 4.88mV Resolution Temperature Measurement Using Integrated
Sensor with 0.125°C Resolution 40 Bytes of Lockable EEPROM Option for Unique 64-bit ID Industry 2-Wire Interface with Programmable
Slave Address Low-Power Consumption: Active Current: 60�A typ, 90�A max
Sleep Current: 1�A typ, 2�A max
APPLICATIONS PDAs Cell Phones/Smartphones
Digital Cameras
ORDERING INFORMATION Selector Guide appears at end of data sheet, for additional
options.
DS2764
High-Precision Li+ Battery Monitor
with 2-Wire InterfaceDS2764 High-Precision Li+ Battery Monitor with 2-Wire Interface
ABSOLUTE MAXIMUM RATINGS Voltage Range on PLS and CC Pins, Relative to VSS -0.3V to +18V
Voltage Range on Any Other Pin, Relative to VSS -0.3V to +6V
Continuous Internal Sense Resistor Current �2.5A
Pulsed Internal Sense Resistor Current �50A for <100µs/s, <1000 pulsesOperating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature See IPC/JEDEC J-STD-020A Specification
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device.
RECOMMENDED DC OPERATING CONDITIONS (2.5V � VDD � 5.5V, TA = -20°C to +70°C.)
DC ELECTRICAL CHARACTERISTICS (2.5V � VDD � 5.5V, TA = -20°C to +70°C.)
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
ELECTRICAL CHARACTERISTICS: PROTECTION CIRCUITRY (2.5V � VDD � 5.5V, TA = 0°C to +50°C.)
ELECTRICAL CHARACTERISTICS: TEMPERATURE, VOLTAGE, CURRENT (2.5V � VDD � 5.5V, TA = -20°C to +50°C.)
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
ELECTRICAL CHARACTERISTICS: 2-WIRE INTERFACE (2.5V � VDD � 5.5V, TA = -20�C to +70�C.)
EEPROM RELIABILITY SPECIFICATION (2.5V � VDD � 5.5V, TA = -20�C to +70�C.)
Note 1: All voltages are referenced to VSS.
Note 2: See the Selector Guide section to determine the corresponding part number for each VOV value.
Note 3: Internal current-sense resistor configuration.
Note 4: External current-sense resistor configuration.
Note 5: Self-heating due to output pin loading and sense resistor power dissipation can alter the reading from ambient conditions.
Note 6: Compensation of the internal sense resistor value for initial tolerance and temperature coefficient of -20°C to +70°C can reduce
the maximum reportable magnitude to 1.9A.
Note 7: Current offset error null to ±1 LSB typically requires 3.5s in-system calibration by user.
Note 8: Current gain error specification applies to gain error in converting the voltage difference at IS1 and IS2, and excludes any error
remaining after the DS2764 compensates for the internal sense resistor’s temperature coefficient of 3700ppm/�C to an accuracy
of �500ppm/�C. The DS2764 does not compensate for external sense resistor characteristics, and any error terms arising from
the use of an external sense resistor should be taken into account when calculating total current measurement error.
Note 9: Accuracy at time of shipment from Dallas Semiconductor is 3% max. Flip-chip board mounting processes may cause the
current gain error to widen to as much as 10% for flip chip devices with the internal sense resistor option. Contact factory for
on-board recalibration procedure for flip chip devices with the internal sense resistor option to improve accuracy.
Note 10: Typical value for tERR1 is specified at 3.6V and +25°C, max value is specified for 0°C to +50°C. Max value for tERR2 is specified
for -20°C to +70°C.
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
Note 14: The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW) of the SCL signal.
Note 15: This device internally provides a hold time of at least 300 ns for the SDA signal (referred to the VIHmin of the SCL
signal) to bridge the undefined region of the falling edge of SCL.
Note 16: Filters on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
Note 17: CB� total capacitance of one bus line in pF.
Figure 1. I2C Bus Timing Diagram C is a trademark of Philips Corp. Purchase of IC components from Maxim Integrated Products, Inc., or one of its sublicensed Associated
Companies, conveys a license under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system 2
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
PIN DESCRIPTION DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
Figure 2. Block Diagram
DETAILED DESCRIPTION The DS2764 high-precision Li+ battery monitor is a data-acquisition, information-storage, and safety-protection device tailored for cost-sensitive battery pack applications. This low-power device integrates precise temperature,
voltage, and current measurement, nonvolatile (NV) data storage, and Li+ protection into the small footprint of either a TSSOP package or flip-chip package. The DS2764 is a key component in applications including remaining
capacity estimation, safety monitoring, and battery-specific data storage.
Through its 2-Wire interface, the DS2764 gives the host system read/write access to status and control registers, instrumentation registers, and general-purpose data storage. The 7-bit slave address is field programmable, thus allowing up to 128 devices to be distinctly addressed by the host system.
The DS2764 is capable of performing temperature, voltage, and current measurement to a resolution sufficient to support process monitoring applications such as battery charge control, remaining capacity estimation, and safety
monitoring. Temperature is measured using an on-chip sensor, eliminating the need for a separate thermistor.
Bidirectional current measurement and accumulation are accomplished using either an internal 25m� sense
resistor or an external device.
EEPROM memory is provided to save important battery data in true NV memory that is unaffected by severe
battery depletion, accidental shorts, or ESD events. 40 bytes are partitioned into two 16-byte blocks and one 8-byte block. Each block can be individually locked or write protected to provide additional security for unchanging battery
data. The lock operation is permanent and thus converts rewritable EEPROM to read only memory. Devices ordered with the unique 64-bit ID option do not have access to the 8 byte block, only the two 16 byte blocks of
EEPROM are available.
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
Figure 3. Application Example DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
POWER MODES The DS2764 has two power modes: active and sleep. While in active mode, the DS2764 continually measures current, voltage, and temperature to provide data to the host system and to support current accumulation and Li+
safety monitoring. In sleep mode, the DS2764 ceases these activities. The DS2764 enters sleep mode when any of the following conditions occurs: The PMOD bit in the Status Register has been set to 1 and both SCL and SDA are low for longer than 2.1s (pack disconnection). The voltage on VIN drops below undervoltage threshold VUV for tUVD (cell depletion).
The DS2764 returns to active mode when any of the following occurs: The PMOD bit has been set to 1 and either the SDA or SCL line is pulled high (pack connection). The PS pin is pulled low (power switch). The voltage on PLS becomes greater than the voltage on VDD (charger connection).
The DS2764 defaults to active mode when power is first applied.
Li+ PROTECTION CIRCUITRY During active mode, the DS2764 constantly monitors cell voltage and current to protect the battery from overcharge (overvoltage), overdischarge (undervoltage), and excessive charge and discharge currents (overcurrent, short
circuit). Conditions and DS2764 responses are described in the following sections and summarized in Table 1 and Figure 4.
Table 1. Li+ Protection Conditions and DS2764 Responses VIS = VIS1 - VIS2. Logic high = VPLS for CC and VDD for DC. All voltages are with respect to VSS. ISNS references current delivered from pin SNS.
Note 1: If VDD < 2.2V, release is delayed until the recovery charge current passed from PLS to VDD charges the battery and allows VDD to
exceed 2.2V.
Note 2: For the internal sense resistor configuration, the overcurrent thresholds are expressed in terms of current: ISNS > IOC for charge
direction and ISNS < -IOC for discharge direction.
Note 3: With test current ITST flowing from PLS to VSS (pulldown on PLS).
Note 4: With test current ITST flowing from VDD to PLS (pullup on PLS).
Overvoltage. If the cell voltage on VIN exceeds the overvoltage threshold, VOV, for a period longer than overvoltage delay, tOVD, the DS2764 shuts off the external charge FET and sets the OV flag in the protection register. When the
cell voltage falls below charge enable threshold VCE, the DS2764 turns the charge FET back on (unless another
protection condition prevents it). Discharging remains enabled during overvoltage, and the DS2764 re-enables the charge FET before VIN < VCE if a discharge current of -80mA (VIS ≤ -2mV) or less is detected.
Undervoltage. If the voltage of the cell drops below undervoltage threshold, VUV, for a period longer than
undervoltage delay, tUVD, the DS2764 shuts off the charge and discharge FETs, sets the UV flag in the protection
register, and enters sleep mode. The DS2764 provides a recovery charge path from PLS to VDD to power the DS2764 by the charger when the cell is severely depleted. Once the DS2764 regains power it will enter active
DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface
Overcurrent, Charge Direction. The voltage difference between the IS1 pin and the IS2 pin (VIS = VIS1 - VIS2) is the filtered voltage drop across the current-sense resistor. If VIS exceeds overcurrent threshold VOC for a period longer
than overcurrent delay tOCD, the DS2764 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 VDD - VTP. The
DS2764 provides a test current of value ITST from PLS to VSS to pull PLS down to detect the removal of the offending charge current source.
Overcurrent, Discharge Direction. If VIS is less than -VOC for a period longer than tOCD, the DS2764 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 VDD - VTP. The DS2764 provides a test current of value ITST from VDD to PLS to pull PLS up to detect the removal of the offending low-impedance load.
Short Circuit. If the voltage on the SNS pin with respect to VSS exceeds short-circuit threshold VSC for a period longer than short-circuit delay tSCD, the DS2764 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 VDD - VTP. The DS2764 provides a test current of value ITST from VDD to PLS to pull PLS up to detect the removal of the short
circuit.
Figure 4. Li+ Protection Circuitry Example Waveforms
Summary. All of the protection conditions described above are OR’ed together to affect the CC and DC outputs. DC = (Undervoltage) or (Overcurrent, Either Direction) or (Short Circuit) or (Protection Register Bit DE = 0)
or (Sleep Mode)
CC = (Overvoltage and VIS ≥ -2mV) or (Undervoltage) or (Overcurrent, Charge Direction) or (Protection
Register bit CE = 0) or (Sleep Mode)
Soft Startup. The discharge protection FET is turned on slowly when the DS2764 enters Active mode from Sleep. The soft startup reduces the inrush current that normally occurs when a battery pack is inserted into an un-powered
host system. Soft Startup does not reduce inrush currents if the DS2764 is already in Active mode when the battery pack is connected to the un-powered system.
