DS2780 Maxim Integrated Products, DS2780 Datasheet

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... GENERAL DESCRIPTION The DS2780 measures voltage, temperature and current, and estimates available rechargeable Lithium Ion and Lithium Ion Polymer batteries. Cell characteristics parameters used in the calculations are stored in on- chip EEPROM. The available capacity registers report a conservative estimate of the amount of ...

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... < V SLEEP IL V (Note 1) SLEEP SYMBOL CONDITIONS T LSB T ERR V LSB ERR I LSB DS2780 Stand-Alone Fuel Gauge IC -0.3V to +6.0V -0.3V to VDD+0.3 -40°C to +85°C -55°C to +125°C = +25°C) A MIN TYP MAX +2.5 +5.5 -0.3 +5.5 = +25°C.) A MIN TYP MAX 65 95 105 1 3 1.5 0.6 0.4 0.2 0.7 x VDD 0 ...

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... RSTH t RSTL t PDH t PDL SYMBOL CONDITIONS t SLOT t REC t LOW0 t LOW1 t RDV t RSTH t RSTL t PDH t PDL DS2780 Stand-Alone Fuel Gauge IC MIN TYP MAX UNITS % Full- ±1 Scale - 7.82 + 12.5 µV µVhr/ - 188 + 0 day ±1 ±2 % ±3 MIN TYP MAX UNITS 60 120 ...

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... Programmable I/O Pin. Can be configured as input or output to monitor or control user- 8 PIO defined external circuitry. Output driver is open drain. This pin has an weak internal pulldown (I SYMBOL CONDITIONS t EEC +50°C EEC A FUNCTION ). DS2780 Stand-Alone Fuel Gauge IC = +25°C.) A MIN TYP MAX UNITS 10 ms 50,000 cycles ) for sensing PD ...

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... SNS DETAILED DESCRIPTION The DS2780 operates directly from 2.5V to 5.5V and supports single cell Lithium-ion battery packs. As shown in Figure 2, the DS2780 accommodates multicell applications by adding a voltage regulator for VDD and voltage divider for VIN. Nonvolatile storage is provided for cell compensation and application parameters. Host side development of fuel-gauging algorithms is eliminated ...

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... PMOD SLEEP was high when UVEN SLEEP was entered, then the DS2780 is prepared to receive a 1-Wire reset from the master. In the first two cases with DQ low during SLEEP, the DS2780 does not respond to the first rising edge of DQ with a presence pulse. ...

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... CURRENT MEASUREMENT In the ACTIVE mode of operation, the DS2780 continually measures the current flow into and out of the battery by measuring the voltage drop across a low-value current-sense resistor, R SNS and VSS is ±51.2mV. The input linearly converts peak signal amplitudes up to 102.4mV as long as the continuous signal level (average over the conversion cycle period) does not exceed ± ...

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... CURRENT MEASUREMENT CALIBRATION The DS2780’s current measurement gain can be adjusted through the RSGAIN register, which is factory-calibrated to meet the data sheet specified accuracy. RSGAIN is user accessible and can be reprogrammed after module or pack manufacture to improve the current measurement accuracy. Adjusting RSGAIN can correct for variation in an external sense resistor’ ...

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... SENSE RESISTOR TEMPERATURE COMPENSATION The DS2780 is capable of temperature compensating the current sense resistor to correct for variation in a sense resistor’s value over temperature. The DS2780 is factory programmed with the sense resistor temperature coefficient, RSTC, set to zero, which turns off the temperature compensation function. RSTC is user accessible and can be reprogrammed after module or pack manufacture to improve the current accuracy when using a high temperature coefficient current-sense resistor ...

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... The AB can be used to account for currents that do not flow through the sense resistor, estimate currents too small to measure, estimate battery self-discharge or correct for static offset of the individual DS2780 device. The AB register allows a user programmed constant positive or negative polarity bias to be included in the current accumulation process. The user-programmed two’ ...

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... AN131 is used to store cell characteristics in the DS2780. Full and empty points are retrieved in a lookup process which re-traces a piece-wise linear model. Three model curves are stored: Full, Active Empty and Standby Empty. Each model curve is constructed with 4 line segments and spans from 0° ...

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... Full: The Full curve defines how the full point of a given cell depends on temperature for a given charge termination. The charge termination method used in the application is used to determine the table values. The DS2780 reconstructs the Full line from cell characteristic table values to determine the Full capacity of the battery at each temperature. Reconstruction occurs in one-degree temperature increments. ...

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... IMIN is located in the Parameter EEPROM block. Termination Current: 50mA Standby Empty (V, I): 3.0V, 4mA 0°C +10°C +20°C 0.927 0.951 0.974 0.051 0.040 0.022 0.013 0.0067 0.0038 FULL(T) Lookup Function AE(T) SE( DS2780 Stand-Alone Fuel Gauge IC +30°C +40°C 0.991 1.0 0.012 0.008 0.001 0 ...

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... AS, however caution should exercised when writing AS to ensure that the cumulative aging estimate is not over written with an incorrect value. Usually, writing AS by the host is not necessary because AS is automatically saved to EEPROM on a periodic basis by the DS2780. (See the Memory section for details.) The EEPROM stored value recalled on power-up. ...

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... RESULT REGISTERS The DS2780 processes measurement and cell characteristics on a 3.5s interval and yields seven result registers. The result registers are sufficient for direct display to the user in most applications. The host system can produce customized values for system use, or user display by combining measurement, result and User EEPROM values. ...

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... RSRC [%] = 100%* (ACR[mVh] - SE(T) * FULL40[mVh]) / STATUS REGISTER The STATUS register contains bits which report the device status. The bits can be set internally by the DS2780. The CHGTF, AEF, SEF, LEARNF and VER bits are read only bits which can be cleared by hardware. The UVF and PORF bits can only be cleared via the 1-Wire interface ...

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... Activates PIO pin open-drain output driver, forcing the PIO pin low 1: Disables the output driver, allowing the PIO pin to be pulled high or used as an input Power-up and SLEEP mode default: 1 (PIO pin is hi-Z) Note: PIO pin has weak pulldown DS2780 Stand-Alone Fuel Gauge IC SLEEP SLEEP ...

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... Read Only MEMORY The DS2780 has 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” return undefined data when read. Reserved bytes should not be written. Several byte registers are paired into two- byte registers in order to store 16-bit values ...

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... FETs. In this manner protection device is triggered, the DS2780 cannot lose more that 4% of charge or discharge data. Table 2. MEMORY MAP ADDRESS (HEX) 00 Reserved STATUS - Status Register 01 RAAC - Remaining Active Absolute Capacity MSB 02 03 RAAC - Remaining Active Absolute Capacity LSB ...

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... Each DS2780 has a unique, factory-programmed 1-Wire net address that is 64 bits in length. The first eight bits are the 1-Wire family code (32h for DS2780). The next 48 bits are a unique serial number. The last eight bits are a cyclic redundancy check (CRC) of the first 56 bits (see Figure 17). The 64-bit net address and the 1-Wire I/O circuitry built into the device enable the DS2780 to communicate through the 1-Wire protocol detailed in the 1-Wire Bus System section of this data sheet ...

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... To facilitate this, each device attached to the 1-Wire bus must connect to the bus with open-drain or tri-state output drivers. The DS2780 uses an open-drain output driver as part of the bidirectional interface circuitry shown in Figure 19 bidirectional pin is not available on the bus master, separate output and input pins can be connected together ...

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... DS2780 is accessed. After successfully executing a Match Net Address command or Search Net Address command, an internal flag is set in the DS2780. When the flag is set, the DS2780 can be repeatedly accessed through the Resume command function. Accessing another device on the bus clears the flag, thus preventing two or more devices from simultaneously responding to the Resume command function ...

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... EEPROM to the shadow. See the Memory section for more details. Write Data [6Ch, XX]. This command writes data to the DS2780 starting at memory address XX. The LSb of the data to be stored at address XX can be written immediately after the MSb of address has been entered. Because the address is automatically incremented after the MSb of each byte is written, the LSb to be stored at address can be written immediately after the MSb to be stored at address XX ...

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... EEPROM Copy Data block containing address XX Recalls EEPROM Recall Data block containing address XX to RAM Permanently locks the block of EEPROM Lock containing address XX DS2780 Stand-Alone Fuel Gauge IC BUS STATE COMMAND AFTER PROTOCOL COMMAND PROTOCOL 69h, XX Master Rx 6Ch, XX Master Tx 48h, XX Master Reset ...

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... DS2780 Tx BIT 1 MASTER Tx BIT 1 BIT BIT 1 MATCH ? MATCH ? YES YES DS2780 Tx BIT 63 BIT 63 DS2780 Tx BIT 63 MASTER Tx BIT 63 BIT 63 MATCH ? DS2780 Stand-Alone Fuel Gauge IC CCh NO A5h NO SKIP RESUME YES YES RESUME NO CLEAR RESUME FLAG SET ? YES MASTER TX MASTER TX FUNCTION FUNCTION ...

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... A read-time slot is initiated when the bus master pulls the 1-Wire bus line from a logic-high level to a logic-low level. The bus master must keep the bus line low for at least 1ms and then release it to allow the DS2780 to present valid data. The bus master can then sample the data t slot, the DS2780 releases the bus line and allows pulled high by the external pullup resistor ...

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... DS2780 active low t SLOT t LOW0 t REC DS2780 Sample Window TYP MAX >1ms 30ms 1ms 3ms t SLOT >1ms Master Sample Window DS2780 Stand-Alone Fuel Gauge IC WRITE 1 SLOT t SLOT t LOW1 DS2780 Sample Window MIN TYP 15ms 15ms 30ms 2ms 1ms 3ms READ 1 SLOT t SLOT t ...