Rev 1; 3/09 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Features The DS2775–DS2778 report available capacity for rechargeable lithium-ion (Li+) and Li+ polymer (Li-Poly) batteries in mAh and as a percentage of full. Safe operation is ensured by the integrated Li+ protector. The DS2776/DS2778 support SHA-1-based challengeresponse authentication in addition to all other DS2775/ DS2777 features.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication ABSOLUTE MAXIMUM RATINGS Continuous Sink Current, PIO, DQ......................................20mA Continuous Sink Current, CC, DC.......................................10mA Operating Temperature Range ...........................-20°C to +70°C Storage Temperature Range .............................-55°C to +125°C Soldering Temperature...........................
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication (VDD = +4.0V to +9.2V, TA = -20°C to +70°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN DQ, PIO, SDA Output Logic-Low VOL I OL = 4mA DQ, PIO Pullup Current I PU Sleep mode, VPIN = (VDD - 0.4V) 30 DQ, PIO, SDA, SCL Pulldown Current I PD Active mode, V PIN = 0.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication EEPROM RELIABILITY SPECIFICATION (VDD = +4.0V to +9.2V, TA = -20°C to +70°C, unless otherwise noted.) PARAMETER SYMBOL EEPROM Copy Time tEEC EEPROM Copy Endurance NEEC CONDITIONS TA = +50°C MIN TYP MAX UNITS 10 ms 50,000 Cycles ELECTRICAL CHARACTERISTICS: 1-Wire INTERFACE, STANDARD (DS2775/DS2776 ONLY) (VDD = +4.0V to +9.2V, TA = -20°C to +70°C.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication (VDD = +4.0V to +9.2V, TA = -20°C to +70°C.) PARAMETER SYMBOL SCL Clock Frequency f SCL Bus-Free Time Between a STOP and START Condition tBUF Hold Time (Repeated) START Condition tHD:STA CONDITIONS (Note 4) (Note 5) MIN 0 TYP MAX UNITS 400 kHz 1.3 μs 0.6 μs Low Period of SCL Clock tLOW 1.3 μs High Period of SCL Clock tHIGH 0.6 μs Setup Time for a Repeated START Condition t SU:STA 0.
Typical Operating Characteristics (TA = +25°C, unless otherwise noted.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication CURRENT MEASUREMENT ACCURACY 6 1 5 -25 0 LSB (1.5625μV) +25°C 25 DS2775/6/7/8 toc09 2 DS2775/6/7/8 toc08 -20°C 1kΩ RESISTOR FROM PLS TO PK+ IRC (mA) ACCURACY (μV) 75 7 DS2775/6/7/8 toc07 125 CURRENT MEASUREMENT OFFSET vs. TEMPERATURE IRC vs. VDD 4 3 +70°C -1 -2 2 -3 1 -4 -75 -125 -0.052 0 -0.032 -0.012 0.008 VSNS (mV) 0.028 0.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication DS2775/DS2776/DS2777/DS2778 Block Diagram VOLTAGE POWER-MODE CONTROL PLS DC CURRENT 15-BIT + SIGN ADC SNS PRECISION ANALOG OSCILLATOR VREF VSS TEMPERATURE CONTROL AND STATUS REGISTERS PIO LOGIC CHARGE PUMP 32-BYTE PARAMETER EEPROM VOLTAGE REGULATOR COMMUNICATION INTERFACE PIN DRIVERS AND POWER SWITCH CONTROL 16-BYTE USER EEPROM VB DS2775–DS2778 VB INTERNAL FuelPack is a trademark of Maxim Integrated Pr
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication PK+ 1kΩ 1kΩ PLS 150Ω DATA CC SRC DC 1kΩ VDD VIN2 DQ VB CP 0.47μF VSS OVD SNS 0.1μF 1kΩ VIN1 DS2775 DS2776 PIO 5.1V 150Ω 1kΩ 0.1μF SRC RSNS PK- DS2777/DS2778 Typical Application Circuit PK+ 1kΩ 1kΩ PLS 150Ω SDA SDA SCL SCL 150Ω 5.1V CC 5.1V 0.1μF SRC DC 1kΩ VIN1 DS2777 DS2778 CP 0.47μF VSS SNS 1kΩ VDD VIN2 PIO VB 150Ω 1kΩ 0.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Detailed Description The DS2775–DS2778 function as an accurate fuel gauge, Li+ protector, and SHA-1-based authentication token (SHA-1-based authentication available only on the DS2776/DS2778). The fuel gauge provides accurate estimates of remaining capacity and reports timely voltage, temperature, and current measurement data.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication RISING EDGE ON DQ SLEEP PSPIO = 0 PSDQ = 0 ACTIVE PMOD = 0 UVEN = 0 RISING EDGE ON SDA OR SCL DS2775/DS2776/DS2777/DS2778 ACTIVE PMOD = 0 UVEN = 0 SLEEP PSPIO = 0 PSDQ = X CHARGER DETECT CHARGER DETECT VIN1 OR VIN2 < VUV PULL DQ LOW ACTIVE PMOD = 0 UVEN = 1 VIN1 OR VIN2 < VUV SLEEP PSPIO = 0 PSDQ = 1 ACTIVE PMOD = 0 UVEN = 1 RISING EDGE ON SDA OR SCL SLEEP PSPIO = 0 PSDQ = X CHARGER DETECT CHARGER DETECT
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Table 1. Li+ Protection Conditions and DS2775/DS2776 Responses ACTIVATION CONDITION RELEASE THRESHOLD THRESHOLD DELAY RESPONSE Overvoltage (OV) (Note 1) VCELL > VOV tOVD CC Off Both VCELL < VCE or (VSNS 1.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Overcurrent, Charge Direction (COC) Charge current develops a negative voltage on VSNS with respect to VSS. If VSNS is less than the charge overcurrent threshold, VCOC, for a period longer than overcurrent delay, tOCD, the DS2775–DS2778 shut off both external FETs and set the COC flag in the Protection register. The charge current path is not reestablished until the voltage on the PLS pin drops below (VDD - VTP).
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Temperature Measurement The DS2775–DS2778 use an integrated temperature sensor to measure battery temperature with a resolution of 0.125°C. Temperature measurements are updated every 440ms and placed in the Temperature register in two’s complement form.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Current Blanking Every 1024th conversion, the ADC measures its input offset to facilitate offset correction. Offset correction occurs approximately once per hour. The resulting correction factor is applied to the subsequent 1023 measurements. During the offset correction conversion, the ADC does not measure the sense resistor signal.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication FRSGAIN value is provided to preserve the factory calibration value only and is not used to calibrate the current measurement. The 16-bit FRSGAIN value is readable from addresses B0h and B1h. Sense-Resistor Temperature Compensation The DS2775–DS2778 can temperature compensate the current-sense resistor to correct for variation in a sense resistor’s value over temperature.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Modeling Cell Characteristics In some designs a systematic error or an application preference requires the application of an arbitrary bias to the current accumulation process. The Current Accumulation Bias register (CAB) allows a user-programmed constant positive or negative polarity bias to be included in the current accumulation process.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication VOLTAGE (R) TEMPERATURE (R) FULL FULL(T) (R) ACTIVE EMPTY AE(T) (R) STANDBY EMPTY SE(T) (R) CAPACITY LOOKUP CURRENT (R) ACCUMULATED CURRENT (ACR) (RW) AVAILABLE CAPACITY CALCULATION ACR HOUSEKEEPING AGE ESTIMATOR AVERAGE CURRENT (R) LEARN FUNCTION REMAINING ACTIVE-ABSOLUTE CAPACITY (RAAC) mAh (R) REMAINING STANDBY-ABSOLUTE CAPACITY (RSAC) mAh (R) REMAINING ACTIVE-RELATIVE C
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication SEGMENT 3 SEGMENT 2 SEGMENT 4 DS2775/DS2776/DS2777/DS2778 SEGMENT 1 SEGMENT 5 100% FULL DERIVATIVE (ppm/°C) CELL CHARACTERIZATION DATA CHARACTERIZATION ACTIVE EMPTY TBP12 STANDBY EMPTY TBP23 TBP34 +40°C Figure 14. Cell Model Example Diagram read from the Current register.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication 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 four segments for each model curve are stored in the cell parameter EEPROM block as ppm/°C.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Active-Empty Voltage (VAE) VAE stores the voltage threshold used to detect the active-empty point. The value is stored in 1 byte with units of 19.5mV and can range from 0 to 4.978V. VAE is stored as an average of the cell’s voltages. VAE is located in the parameter EEPROM block. See the Modeling Cell Characteristics section for more information.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication count-based estimation is reset after a learn cycle. The cycle-count-based estimation is used only in the absence of a learn cycle. ACR Housekeeping The ACR value is adjusted occasionally to maintain the coulomb count within the model curve boundaries. When the battery is charged to full (CHGTF set), the ACR is set equal to the age-scaled full lookup value at the present temperature.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication 214 213 212 211 LSB—ADDRESS 03h 210 29 28 MSb 27 LSb 26 25 24 23 22 21 MSb 20 LSb UNITS: 1.6mAh Figure 16. Remaining Active Absolute Capacity (RAAC) [mAh] The RAAC register reports the capacity available under the current temperature conditions to the the active-empty point in absolute units of milliamps/hour (mAh). RAAC is 16 bits.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Protection, Status, and Control Registers Protection Register Format The Protection register reports events detected by the Li+ safety circuit on bits [7:2]. Bits 0 and 1 are used to disable the charge and discharge FET gate drivers. Bits [7:2] are set by internal hardware only. Bits 2 and 3 are cleared by hardware only.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication The Status register contains bits that report the device status. All bits are set internally. The CHGTF, AEF, SEF, and LEARNF bits are read-only. The UVF and PORF bits can be cleared by writing a 0 to the bit locations. Status Register (01h) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 CHGTF AEF SEF LEARNF X UVF PORF X Bit 7: Charge-Termination Flag (CHGTF).
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication 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 by using the Copy Data command.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication The 8-bit Overvoltage Threshold register (VOV) sets the overvoltage threshold for the protection circuitry. An overvoltage condition is detected if either of the voltages on VIN1 or VIN2 exceeds the OV threshold for tOVD. The LSB of the VOV register is 2 x 5V/1024 = 31.25mV. The VOV set point can be calculated by the following formula.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Overcurrent Thresholds The overcurrent thresholds are set in the upper nibble of the RSGAIN register. The OC1 and OC0 bits set the overcurrent thresholds for the charge and discharge thresholds. The short-circuit threshold is set by the SC0 bit (see Tables 6 and 7, respectively, for overcurrent and short-circuit threshold values).
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication The EEPROM register provides access control of the EEPROM blocks. EEPROM blocks can be locked to prevent alteration of data within the block. Locking a block disables write access to the block. Once a block is locked, it cannot be unlocked. Read access to EEPROM blocks is unaffected by the lock/unlock status.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Memory The DS2775–DS2778 have a 256-byte linear memory space with registers for instrumentation, status, and control, as well as EEPROM memory blocks to store parameters and user information. Byte addresses designated as “reserved” typically return FFh when read. These bytes should not be written. Several byte registers are paired into 2-byte registers to store 16-bit values.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication ADDRESS (HEX) ADDRESS (HEX) DESCRIPTION DESCRIPTION 60h Control Register 71h AE Segment 3 Slope Register 61h Accumulation Bias Register (AB) 72h AE Segment 2 Slope Register 62h Aging Capacity Register MSB (AC) 73h AE Segment 1 Slope Register 63h Aging Capacity Register LSB (AC) 74h SE Segment 4 Slope Register 64h Charge Voltage Register (VCHG) 75h SE Segment 3 Slope Register 65h Minimum Charge Cu
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Table 9.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication DS2776/DS2778 Authentication Commands Write Challenge [0Ch] This command writes the 64-bit challenge to the DS2776/DS2778. The LSB of the 64-bit data argument can begin immediately after the MSB of the command has been completed. If more than 8 bytes are written, the final value in the Challenge register is indeterminate.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Table 11. Secret Management Function Commands COMMAND HEX FUNCTION Clear Secret 5Ah Clears the 64-bit secret to 0000 0000 0000 0000h. Compute Next Secret without ROM ID 30h Generates new global secret. Compute Next Secret with ROM ID 33h Generates new unique secret. Lock Secret 60h Sets lock bit to prevent changes to the secret. the new secret value to EEPROM.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Hardware Configuration Because the 1-Wire bus has only a single line, it is important that each device on the bus be able to drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must connect to the bus with open-drain or three-state output drivers. The DS2775/ DS2776 use an open-drain output driver as part of the bidirectional interface circuitry shown in Figure 24.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Match Net Address [55h] This command allows the bus master to specifically address one DS2775/DS2776 on the 1-Wire bus. Only the addressed DS2775/DS2776 responds to any subsequent function command. All other slave devices ignore the function command and wait for a reset pulse. This command can be used with one or more slave devices on the bus.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication no effect. The Lock command is permanent; a locked block can never be written again. Table 12. All Function Commands COMMAND HEX DESCRIPTION Write Challenge 0Ch Writes 64-bit challenge for SHA-1 processing. Required immediately prior to all Compute MAC and Compute Next Secret commands.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication tSHA 1-Wire RESET WAIT FOR MAC COMPUTATION SKIP-ROM COMMAND PRESENCE PULSE COMPUTE MAC COMMAND UP TO 160 READ TIME SLOTS (READ 20-BYTE MAC) 8 WRITE-ZERO TIME SLOTS Figure 25. Compute MAC Command 1-Wire RESET SKIP-ROM COMMAND PRESENCE PULSE tSHA tEEC WAIT FOR MAC COMPUTATION WAIT FOR EEPROM PROGRAMMING COMPUTE NEXT SECRET COMMAND Figure 26.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication DS2775/DS2776/DS2777/DS2778 tEEC 1-Wire RESET SKIP-ROM COMMAND CLEAR/LOCK SECRET COMMAND OR SET/CLEAR OVERDRIVE COMMAND WAIT FOR EEPROM COPY TIME PRESENCE PULSE Figure 28. Clear/Lock Secret, Set/Clear Overdrive Commands tRSTL tRSTH tPDH tPDL PK+ DQ PK- LINE TYPE LEGEND: BUS MASTER ACTIVE LOW DS2775/DS2776 ACTIVE LOW RESISTOR PULLUP Figure 29.
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Write Time Slots A write time slot is initiated when the bus master pulls the 1-Wire bus from a logic-high (inactive) level to a logic-low level. There are two types of write time slots: write-one and write-zero. All write time slots must be tSLOT in duration with a 1µs minimum recovery time, tREC, between cycles.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication DS2775/DS2776/DS2777/DS2778 WRITE-ZERO SLOT WRITE-ONE SLOT tSLOT tSLOT tLOW0 tLOW1 tREC VPULLUP GND DEVICE SAMPLE WINDOW MIN TYP MAX > 1μs MIN DEVICE SAMPLE WINDOW TYP MAX MODE: STANDARD 15μs 15μs 30μs 15μs 15μs 30μs OVERDRIVE 2μs 1μs 3μs 2μs 1μs 3μs READ-ZERO SLOT tSLOT VPULLUP tRDV READ-ONE SLOT tSLOT tREC tRDV GND > 1μs MASTER SAMPLE WINDOW MASTER SAMPLE WINDOW MODE: STANDARD 15μs 15μ
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Data Order A byte of data consists of 8 bits ordered MSb first. The LSb of each byte is followed by the acknowledge bit. The DS2777/DS2778 registers composed of multibyte values are ordered MSB first. The MSB of multibyte registers is stored on even data memory addresses. selects a read transaction, with the subsequent bytes being read from the slave by the master.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication KEY S DESCRIPTION KEY DESCRIPTION START Bit Sr Repeated START SAddr Slave Address (7-bit) W R/W Bit = 0 FCmd Function Command Byte R R/W Bit = 1 P STOP bit MAddr Data Memory Address Byte Data Byte Written by Master Data Data Byte Returned by Slave A Acknowledge Bit (Master) A Acknowledge Bit (Slave) N Not Acknowledge (Master) N Not Acknowledge (Slave) assumed by the DS2777/DS2778 beginning wi
DS2775/DS2776/DS2777/DS2778 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication Table 15. Function Commands FUNCTION COMMAND TARGET EEPROM BLOCK FCmd VALUE 0 42h 1 44h 0 B2h 1 B4h Copy Data Recall Data 0 63h 1 66h — 39h Lock Read ROM ID DESCRIPTION This command copies the shadow RAM to the target EEPROM block. Copy data commands that target locked blocks are ignored.
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication REVISION NUMBER REVISION DATE 0 10/08 1 3/09 DESCRIPTION PAGES CHANGED Initial release. — Corrected values in the VOV Register Programmability table (Table 5). 27 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
