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| DS2720 Efficient, Addressable Single-Cell Rechargeable Lithium Protection IC www.maxim-ic.com FEATURES Rechargeable Lithium-Ion (Li+) Safety Circuit - Overvoltage Protection - Overcurrent/Short-Circuit Protection - Undervoltage Protection - Overtemperature Protection Controls High-Side N-Channel Power MOSFETs Driven from 9V Charge Pump System Power Management and Control Feature Support Eight Bytes of Lockable EEPROM Dallas 1-Wire(R) Interface with Unique 64-Bit Device Address 8-Pin mSOP Package Low Power Consumption: - Active Current: 12.5mA typ - Sleep Current: 1.5mA typ PIN CONFIGURATION PLS PS DQ VSS 1 2 3 4 8 7 6 5 CP DC CC VDD DS2720U mSOP PIN DESCRIPTION PLS PS DQ VSS VDD CP CC DC Battery-Pack Positive Terminal Input Power-Switch Sense Input Data Input/Output Device Ground Power-Supply Input Reservoir Capacitor Charge Control Output Discharge Control Output DESCRIPTION The DS2720 single-cell rechargeable Li+ protection IC provides electronic safety functions required for rechargeable Li+ applications including protecting the battery during charge, protection of the circuit from damage during periods of excess current flow and maximization of battery life by limiting the level of cell depletion. Protection is facilitated by electronically disconnecting the charge and discharge conduction path with switching devices such as low-cost N-channel power MOSFETs. Since the DS2720 provides high-side drive to external N-channel protection MOSFETs from a 9V charge pump, superior on-resistance performance results compared to common low-side protector circuits using the same FETs. The FET on-resistance actually decreases as the battery discharges. Adding to the uniqueness of the DS2720 is the ability of the system to control the FETs from either the data interface or a dedicated input thereby eliminating the power-switch control redundancy of rechargeable Li+ battery systems. Through its 1-Wire interface, the DS2720 gives the host system read/write access to status and control registers, instrumentation registers, and general-purpose data storage. Each device has a factoryprogrammed 64-bit net address that allows it to be individually addressed by the host system. 1-Wire is a registered trademark of Dallas Semiconductor. 1 of 21 112602 DS2720 Two types of user-memory are provided on the DS2720 for battery information storage: EEPROM and lockable EEPROM. EEPROM memory saves important battery data in true nonvolatile (NV) memory that is unaffected by severe battery depletion, accidental shorts, or ESD events. Lockable EEPROM becomes ROM when locked to provide additional security for unchanging battery data. ORDERING INFORMATION PART DS2720AU DS2720AU/T&R DS2720BU DS2720BU/T&R DS2720CU DS2720CU/T&R DESCRIPTION DS2720 in 8-Lead mSOP in Bulk with VOVA = 4.275V DS2720 in 8-Lead mSOP in Tape-and-Reel with VOVA = 4.275V DS2720 in 8-Lead mSOP in Bulk with VOVB = 4.35V DS2720 in 8-Lead mSOP in Tape-and-Reel with VOVB = 4.35V DS2720 in 8-Lead mSOP in Bulk with VOVC = 4.30V DS2720 in 8-Lead mSOP in Tape-and-Reel with VOVC = 4.30V 2 of 21 DS2720 Figure 1. BLOCK DIAGRAM DQ PS 1-WIRE INTERFACE AND CONTROL TEMP SENSOR (Tdevice) 64-BIT ROM LOCKABLE EEPROM STATUS/CONTROL + TMAX + OUTPUT BUFFER CP CC VDD VOV VCE + + DELAY tOVD S R Q ++ Q VUV VSS (1) ++ DELAY tUVD L O G I C S R DC + RTST (2) VOC + DELAY tOCD + PLS VCH VSC + ++ DELAY tSCD 1) Normally open, closed to enable test current, ITST 2) Normally open, closed to enable test current, ITST, and recovery charge (See Rechargeable Li+ Protection Circuitry section for more information.) 3 of 21 DS2720 Table 1. DETAILED PIN DESCRIPTION SYMBOL PLS DESCRIPTION Battery-Pack Positive Terminal Input. The device monitors the state of the battery pack's positive terminal through this pin in order to detect events such as the attachment of a charger or the removal of a short circuit. Connect PLS to the pack positive terminal through a 100W resistor. Power-Switch Sense Input. The device wakes up from sleep mode when it senses the closure of a switch to VSS on this pin. PS has a high-impedance internal pullup. Data Input/Out. 1-Wire data line. Open-drain output driver. Connect this pin to the DATA terminal of the battery pack. DQ has an internal 0.5mA pull-down. Device Ground. Connect directly to the negative terminal of the battery cell. Power Supply Input. Connect VDD to the positive terminal of the battery cell through a decoupling network. Charge Pump Output. The internal charge pump regulates CP to 9V which supplies the ON state drive to the protection FETs. Connect a 0.1mF reservoir capacitor from CP to VSS. Charge Protection Control Output. Controls an external N-channel high-side charge protection FET. Discharge Protection Control Output. Controls an external N-channel high-side discharge protection FET. PS DQ VSS VDD CP CC DC Figure 2. APPLICATION EXAMPLE 102 102 PACK+ 100 102 1k 1k DS2720 330 PLS PS DQ 330 VSS CP DC CC VDD 104 104 10 PS DATA 1-CELL Li+ PACK- 4 of 21 DS2720 POWER MODES The DS2720 has two power modes: active and sleep. While in active mode, the DS2720 continuously performs safety monitoring. In sleep mode, the DS2720 ceases monitoring activities and drives both the charge and discharge protection FETs to an "off state". Upon returning to the active mode from the sleep mode, DS2720 resumes safety monitoring and conditionally turns on the protection FETs. Table 2. POWER MODE TRANSITION CONDITIONS Active (R) Sleep VDD < VUV Sleep (R) Active(1) PS pulled to VSS or VPLS > VDD + VCH (1) DS2720 does not transition to Active Mode if VDD < VSC. RECHARGEABLE Li+ PROTECTION CIRCUITRY During active mode, the DS2720 constantly monitors cell voltage and voltage drop across the FETs to protect the battery from overcharge (overvoltage), overdischarge (undervoltage), and excessive discharge currents (overcurrent, short circuit). Conditions and DS2720 responses are described in the sections below and summarized in Table 3 and Figure 3. Table 3. PROTECTION CONDITIONS AND DS2720 RESPONSES CONDITION NAME Overvoltage Undervoltage ACTIVATION THRESHOLD DELAY RESPONSE VDD > VOV VSC < VDD < VUV VDD < VSC or (while in active mode) VDD < VCE VDD - VPLS > VOC VDD < VSC Tdevice > TMAX tOCD tSCD tOVD(1) tUVD CC = VOLCC CC = VOLCC DC = VOLDC RTST enabled(2) CC = VOLCC DC = VOLCC CC = VOLCC DC = VOLDC CC = VOLCC DC = VOLDC RELEASE THRESHOLD VDD < VCE or VDD - VPLS > VOC VPLS > VDD + VCH and VDD > VUV (charger connected) VDD VCE VPLS > VDD - VOC(3) VPLS > VDD - VOC(3) Tdevice < TMAX Recovery Charge Overcurrent Short Circuit Overtemperature All voltages are with respect to VSS. (1) During transition from sleep to active, tOVD = 0. (2) Recovery charge current is limited by RTST and forward voltage of blocking diode, which prevents discharging through RTST when recovery charge enabled. (3) With test current ITST flowing from VDD to PLS (pullup on PLS). 5 of 21 DS2720 Overvoltage. If the cell voltage sensed at VDD exceeds overvoltage threshold VOV for a period longer than overvoltage delay tOVD, the DS2720 shuts off the external charge FET and sets the OV flag in the protection register. Discharging remains enabled during overvoltage. The charge FET is re-enabled (unless another protection condition prevents it), when the cell voltage falls below charge enable threshold VCE, or a discharge causes VDD - VPLS > VOC. Undervoltage. If the cell voltage sensed at VDD drops below undervoltage threshold VUV for a period longer than undervoltage delay tUVD, the DS2720 shuts off the charge and discharge FETs, sets the UV flag in the protection register, and enters sleep mode. The DS2720 turns on both the charge and discharge FETs after the cell voltage rises above VUV and a charger is present. Short Circuit. If the cell voltage sensed at VDD drops below depletion threshold VSC for a period of tSCD, the DS2720 shuts off the charge and discharge FETs and sets the DOC flag in the protection register. The current path through the charge and discharge FETs is not re-established until the voltage on PLS rises above VDD - VOC. The DS2720 provides a test current through internal resistor RTST from VDD to PLS to pull up PLS when VDD rises above VSC. The test current allows the DS2720 to detect the removal of the offending low-impedance load. Additionally, a recovery charge path through RTST from PLS to VDD is enabled. Overcurrent. If the voltage across the protection FETs (VDD - VPLS) is greater than VOC for a period longer than tOCD, the DS2720 shuts off the external charge and discharge FETs and sets the DOC flag in the protection register. The current path is not re-established until the voltage on PLS rises above VDD VOC. The DS2720 provides a test current through internal resistor RTST from VDD to PLS to detect the removal of the offending low-impedance load. Overtemperature. If the device temperature exceeds TMAX, the DS2720 immediately shuts off the external discharge and charge FETs. The FETs are not turned back on until the cell temperature drops below TMAX AND the host resets the OT bit. 6 of 21 DS2720 Figure 3. Li+ PROTECTION CIRCUITRY EXAMPLE WAVEFORMS VDD VOV VCE VUV VSC VPLS - VDD VCH 0 -VOC RECOVERY CHARGED THROUGH CHARGE ICELL DISCHARGE 0 -IOC -ISC VOHCP CC tOVD tON tUVD tON tUVD tOCD tON tUVD VOLCC VOHCP DC POWER MODE OVERCURRENT OR SHORT TEST RECOVERY CHARGE tSCD tUVD VOLDC ACTIVE SLEEP ACTIVE INACTIVE ENABLED DISABLED SHORT-CIRCUIT EVENT OVERVOLTAGE UNDERVOLTAGE EVENT EVENT OVERCURRENT EVENT UNDERVOLTAGE EVENT SEVERE DEPLETION Notes: IOC = Current that produces a voltage drop across FETs equal to VOC threshold. ISC = Current drawn from the battery during short-circuit event. (Collapses the cell terminal voltage to VSC.) Above example assumes FET on-resistance values such that the overcurrent threshold, VOC, is reached before the short-circuit threshold, VSC. 7 of 21 DS2720 MEMORY The DS27xx family of products is organized into a 256-byte linear address space with registers for instrumentation, status, and control in the lower 32 bytes, with lockable EEPROM memory occupying portions of the remaining address space. All EEPROM memory is general purpose except address 31h, which should be written with the default values for the status register. EEPROM memory is shadowed by RAM to eliminate programming delays between writes and to allow the data to be verified by the host system before being copied to EEPROM. All reads and writes to/from EEPROM memory in fact access the shadow RAM. In unlocked EEPROM blocks, the write data command updates shadow RAM. In locked EEPROM blocks, the write data command is ignored. The copy data command copies the contents of shadow RAM to EEPROM in an unlocked block of EEPROM but has no effect on locked blocks. The recall data command copies the contents of a block of EEPROM to shadow RAM regardless of whether the block is locked or not. Table 4. MEMORY MAP ADDRESS (hex) 00 01 02-06 07 08 09-1F 20-23 24-2F 30-33 34-FF (1) DESCRIPTION Protection Register Status Register Reserved EEPROM Register Special Feature Register Reserved EEPROM, Block 0 Reserved EEPROM, Block 1 (31 = Status Register Initialization) Reserved READ/WRITE R/W R -- R R/W -- R/W (1) -- R/W (1) -- Each EEPROM block is read/write until locked by the LOCK command, after which it is read-only. PROTECTION REGISTER The protection register consists of flags that indicate protection circuit status and switches that give conditional control over the charging and discharging paths. Bits OV, UV, and DOC are set when corresponding protection conditions occur and remain set until cleared by the host system. The format of the protection register is shown in Figure 4. The function of each bit is described in detail in the following paragraphs. Figure 4. PROTECTION REGISTER FORMAT Address 00 Bit 7 OV Bit 6 UV Bit 5 0 Bit 4 DOC Bit 3 CC Bit 2 DC Bit 1 CE Bit 0 DE 8 of 21 DS2720 OV--Overvoltage Flag. When set to 1, this bit indicates the battery pack has experienced an overvoltage condition. This bit does not clear itself after the overvoltage state is corrected, and thus must be reset by the host system. A reset of this bit should be issued after the battery voltage falls below VCE in order to detect future events. The OV bit is a volatile R/W bit, initialized to 0 upon power-on-reset (POR). UV--Undervoltage Flag. When set to 1, this bit indicates the battery pack has experienced an undervoltage condition. This bit does not clear itself after the undervoltage state is corrected, and thus should be reset by the host system in order to detect future events. The UV bit is a volatile R/W bit, initialized to 1 upon POR. DOC--Overcurrent Flag. When set to 1, this bit indicates the battery pack has experienced an overcurrent (or short-circuit) condition. This bit does not clear itself after the over/shortcurrent state is corrected, and thus should be reset by the host system in order to detect future events. The DOC bit is a volatile R/W bit, initialized to 1 upon POR. CC--CC Pin Mirror. This read-only bit mirrors the state of the CC output pin. The CC bit is a 1 when the CC pin is driven high (VOHCC). The CC bit is a 0 when the CC pin is driven low (VOLCC). DC--DC Pin Mirror. This read-only bit mirrors the state of the DC output pin. The DC bit is a 1 when the DC pin is driven high (VOHDC). The DC bit is a 0 when the DC pin is driven low (VOLDC). CE--Charge Enable. Writing a 0 to this bit disables charging (CC output low, external charge FET off) regardless of cell or pack conditions. Writing a 1 to this bit enables charging, subject to override by the presence of any protection conditions. The DS2720 automatically sets this bit to 1 when it transitions from sleep mode to active mode. The CE bit is a volatile R/W bit, initialized to 1 upon POR. DE--Discharge Enable. Writing a 0 to this bit disables discharging (DC output low, external discharge FET off) regardless of cell or pack conditions. Writing a 1 to this bit enables discharging, subject to override by the presence of any protection conditions. The DS2720 automatically sets this bit to 1 when it transitions from sleep mode to active mode. The DE bit is a volatile R/W bit, initialized to 1 upon POR. STATUS REGISTER The default values for the status register bits are stored in lockable EEPROM in the corresponding bits of address 31h. A recall data command for EEPROM block 1 recalls the default values into the status register bits. The format of the status register is shown in Figure 5. The function of each bit is described in detail in the following paragraphs. Figure 5. STATUS REGISTER FORMAT Address 01 Bit 7 X Bit 6 X Bit 5 0 Bit 4 RNAOP Bit 3 0 Bit 2 X Bit 1 X Bit 0 X 9 of 21 DS2720 BIT 5--This bit is read only. The value of this bit is set by bit 5 of address 31h and is factory set to 0. The value of address 31h bit 5 must not be changed. RNAOP--Read Net Address Opcode. A value of 0 in this bit sets the opcode for the read net address command to 33h, while a 1 sets the opcode to 39h. This bit is read-only. The desired default value should be set in bit 4 of address 31h. The factory default for RNAOP is 0. BIT 3--This bit is read only. The value of this bit is set by bit 3 of address 31h and is factory set to 0. The value of address 31h bit 3 must not be changed. X--Reserved Bits. EEPROM REGISTER The format of the EEPROM register is shown in Figure 6. The function of each bit is described in detail in the following paragraphs. Figure 6. EEPROM REGISTER FORMAT Address 07 Bit 7 EEC Bit 6 LOCK Bit 5 X Bit 4 X Bit 3 X Bit 2 X Bit 1 BL1 Bit 0 BL0 EEC--EEPROM Copy Flag. A 1 in this read-only bit indicates that a copy data command is in progress. While this bit is high, writes to EEPROM addresses are ignored. A 0 in this bit indicates that data can be written to unlocked EEPROM blocks if the DS2720 is in the active mode of operation. LOCK--EEPROM Lock Enable. When this bit is 0, the lock command is ignored. Writing a 1 to this bit enables the lock command. After the lock command is executed, the LOCK bit is reset to 0. The LOCK bit is a volatile R/W bit, initialized to 0 upon POR. BL1--EEPROM Block 1 Lock Flag. A 1 in this read-only bit indicates that EEPROM block 1 (addresses 30 to 33h) is locked (read-only) while a 0 indicates block 1 is unlocked (read/write). BL0--EEPROM Block 0 Lock Flag. A 1 in this read-only bit indicates that EEPROM block 0 (addresses 20 to 23h) is locked (read-only) while a 0 indicates block 0 is unlocked (read/write). X--Reserved Bits. 10 of 21 DS2720 SPECIAL FEATURE REGISTER The format of the special feature register is shown in Figure 7. The function of each bit is described in detail in the following paragraphs. Figure 7. SPECIAL FEATURE REGISTER FORMAT Address 08 Bit 7 PSF Bit 6 X Bit 5 X Bit 4 X Bit 3 X Bit 2 X Bit 1 X Bit 0 OT PSF-- PS Flag. This bit is reset to 0 when the DS2720 detects the PS pin is pulled to VSS. This bit does not set itself to a 1 after the PS pin returns to a high logic level, and thus must be set by the host system to detect future events. This bit is initialized to a 1 upon POR. OT--Overtemperature Flag. When set to 1, this bit indicates the battery pack has experienced an overtemperature condition. This bit does not clear itself after the overtemperature state is corrected, and thus must be reset by the host system after the temperature decreases below TMAX to re-enable the charge and discharge FETs. Writing a 1 to this bit disables the FETs, but this is not recommended. The OT bit is a volatile R/W bit, initialized to 0 upon POR. X--Reserved Bits. PS INPUT PIN The PS pin is internally pulled to VDD through a high-value resistance. PS is continuously monitored for a low-impedance connection to VSS. Connecting PS to VSS wakes up the DS2720 if it was in sleep mode. If the DS2720 was in active mode, PS has no effect. 1-WIRE BUS SYSTEM The 1-Wire bus is a system that has a single bus master and one or more slaves. A multidrop bus is a 1Wire bus with multiple slaves. A single-drop bus has only one slave device. In all instances, the DS2720 is a slave device. The bus master is typically a microprocessor in the host system. The discussion of this bus system consists of four topics: 64-bit net address, hardware configuration, transaction sequence, and 1-Wire signaling. 64-BIT NET ADDRESS Each DS2720 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 (31h for DS2720). The next 48 bits are a unique serial number. The last eight bits are a CRC of the first 56 bits (see Figure 8). The 64-bit net address and the 1-Wire I/O circuitry built into the device enable the DS2720 to communicate through the 1-Wire protocol detailed in the 1-Wire Bus System section of this data sheet. 11 of 21 DS2720 Figure 8. 1-WIRE NET ADDRESS FORMAT 8-Bit CRC MSb 48-Bit Serial Number 8-Bit Family Code (31h) LSb CRC GENERATION The DS2720 has an 8-bit cyclic redundancy check (CRC) stored in the most significant byte of its 1-Wire net address. To ensure error-free transmission of the address, the host system can compute a CRC value from the first 56 bits of the address and compare it to the CRC from the DS2720. The host system is responsible for verifying the CRC value and taking action as a result. The DS2720 does not compare CRC values and does not prevent a command sequence from proceeding as a result of a CRC mismatch. Proper use of the CRC can result in a communication channel with a very high level of integrity. The CRC can be generated by the host using a circuit consisting of a shift register and XOR gates as shown in Figure 9, or it can be generated in software. Additional information about the Dallas 1-Wire CRC is available in Application Note 27, Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Touch Memory Products. In the circuit in Figure 9, the shift register bits are initialized to 0. Then, starting with the least significant bit of the family code, one bit at a time is shifted in. After the 8th bit of the family code has been entered, then the serial number is entered. After the 48th bit of the serial number has been entered, the shift register contains the CRC value. Figure 9. 1-WIRE CRC GENERATION BLOCK DIAGRAM INPUT MSb XOR XOR LSb XOR 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 tri-state output drivers. The DS2720 uses an open-drain output driver as part of the bidirectional interface circuitry shown in Figure 10. If a bidirectional pin is not available on the bus master, separate output and input pins can be connected together. The 1-Wire bus must have a pullup resistor at the bus-master end of the bus. For short line lengths, the value of this resistor should be approximately 5kW. The idle state for the 1-Wire bus is high. If, for any reason, a bus transaction must be suspended, the bus must be left in the idle state in order to properly resume the transaction later. If the bus is left low for more than 120ms, slave devices on the bus begin to interpret the low period as a reset pulse, effectively terminating the transaction. 12 of 21 DS2720 Figure 10. 1-WIRE BUS INTERFACE CIRCUITRY BUS MASTER +VPULLUP (2.0V TO 5.5V) 4.7kW Rx 0.5mA (typ) Rx = RECEIVE Tx = TRANSMIT Rx DS2720 1-WIRE PORT Tx Tx 100W MOSFET TRANSACTION SEQUENCE The protocol for accessing the DS2720 through the 1-Wire port is as follows: Initialization Net Address Command Function Command Transaction/Data The sections that follow describe each of these steps in detail. All transactions of the 1-Wire bus begin with an initialization sequence consisting of a reset pulse transmitted by the bus master followed by a presence pulse simultaneously transmitted by the DS2720 and any other slaves on the bus. The presence pulse tells the bus master that one or more devices are on the bus and ready to operate. For more details, see the 1-Wire Signaling section. NET ADDRESS COMMANDS Once the bus master has detected the presence of one or more slaves, it can issue one of the ROM commands described in the following paragraphs. The name of each net address command is followed by the 8-bit opcode for that command in square brackets. Figure 11 presents a transaction flowchart of the ROM commands. Read Net Address [33h or 39h]. This command allows the bus master to read the DS2720's 1-Wire net address. This command can only be used if there is a single slave on the bus. If more than one slave is present, a data collision occurs when all slaves try to transmit at the same time (open drain produces a wired-AND result). The RNAOP bit in the status register selects the opcode for this command, with RNAOP = 0 indicating 33h and RNAOP = 1 indicating 39h. Match Net Address [55h]. This command allows the bus master to specifically address one DS2720 on the 1-Wire bus. Only the addressed DS2720 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. 13 of 21 DS2720 Skip Net Address [CCh]. This command saves time when there is only one 1-Wire device on the bus by allowing the bus master to issue a function command without specifying the address of the slave. If more than one slave device is present on the bus, a subsequent function command can cause a data collision when all slaves transmit data at the same time. Search Net Address [F0h]. This command allows the bus master to use a process of elimination to identify the 1-Wire net addresses of all slave devices on the bus. The search process involves the repetition of a simple three-step routine: read a bit, read the complement of the bit, then write the desired value of that bit. The bus master performs this simple three-step routine on each bit location of the net address. After one complete pass through all 64 bits, the bus master knows the address of one device. The remaining devices can then be identified on additional iterations of the process. See Chapter 5 of the Book of DS19xx iButton(R) Standards for a comprehensive discussion of a net address search, including an actual example. Resume Command [A5H]. In a typical application the DS2720 can be accessed several times to complete control adjustment. To maximize data throughput in a multidrop environment, the resume command has been implemented. This function checks the status of an internal flag. If it is set, it directly transfers control in similar fashion to the skip net address command. The only way to set the internal flag is through successfully executing the match net address or search net address. Once the flag has been set, the device can be repeatedly accessed through the resume command. Accessing another device on the bus clears the flag, thus preventing two or more devices from simultaneously responding to the resume command function. FUNCTION COMMANDS After successfully completing one of the net address commands, the bus master can access the features of the DS2720 with any of the function commands described in the following paragraphs. The name of each function is followed by the 8-bit opcode for that command in square brackets. The function commands are summarized in Table 5. Read Data [69h, XX]. This command reads data from the DS2720 starting at memory address XX. The LSb of the data in address XX is available to be read immediately after the MSb of the address has been entered. Because the address is automatically incremented after the MSb of each byte is received, the LSb of the data at address XX + 1 is available to be read immediately after the MSb of the data at address XX. If the bus master continues to read beyond address FFh, data is read starting at memory address 00 and the address is automatically incremented until a reset pulse occurs. Addresses labeled "Reserved" in the memory map contain undefined data. The read data command can be terminated by the bus master with a reset pulse at any bit boundary. Write Data [6Ch, XX]. This command writes data to the DS2720 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 XX + 1 can be written immediately after the MSb to be stored at address XX. If the bus master continues to write beyond address FFh, the data starting at address 00 is overwritten. Writes to read-only addresses, reserved addresses and locked EEPROM blocks are ignored. Incomplete bytes are not written. Writes to unlocked EEPROM blocks are to shadow RAM rather than EEPROM. See the Memory section for more details. Copy Data [48h, XX]. This command copies the contents of shadow RAM to EEPROM for the 4-byte EEPROM block containing address XX. Copy data commands that address locked blocks are ignored. While the copy data command is executing, the EEC bit in the EEPROM register is set to 1 and writes to iButton is a registered trademark of Dallas Semiconductor. 14 of 21 DS2720 EEPROM addresses are ignored. Reads and writes to non-EEPROM addresses can still occur while the copy is in progress. The copy data command takes tEEC time to execute, starting on the next falling edge after the address is transmitted. The copy data command is ignored by the DS2720 while in the sleep mode. Recall Data [B8h, XX]. This command recalls the contents of the 4-byte EEPROM block containing address XX to shadow RAM. Lock [6Ah, XX]. This command locks (write-protects) the 4-byte block of EEPROM memory containing memory address XX. The LOCK bit in the EEPROM register must be set to l before the lock command is executed. To help prevent unintentional locks, one must issue the lock command immediately after setting the LOCK bit (EEPROM register, address 07h, bit 06) to a 1. If the LOCK bit is 0 or if setting the lock bit to 1 does not immediately precede the lock command, the lock command has no effect. The lock command is permanent; a locked block can never be written again. The lock command is ignored by the DS2720 while in the sleep mode. Table 5. FUNCTION COMMANDS COMMAND DESCRIPTION COMMAND PROTOCOL BUS STATE AFTER COMMAND PROTOCOL BUS DATA Read Data Write Data Copy Data Recall Data Lock Reads data from memory starting at address XX Writes data to memory starting at address XX Copies shadow RAM data to EEPROM block containing address XX Recalls EEPROM block containing address XX to RAM Permanently locks the block of EEPROM containing address XX 69h, XX 6Ch, XX 48h, XX B8h, XX 6Ch, 07h, 4Xh 6Ah, XX Master Rx Master Tx Master Reset Master Reset Master Reset Up to 256 bytes of data Up to 256 bytes of data None None None 15 of 21 DS2720 Figure 11. NET ADDRESS COMMAND FLOW CHART MASTER Tx RESET PULSE DS2720 Tx PRESENCE PULSE MASTER Tx NET ADDRESS COMMAND 33h/39h READ NO 55h MATCH NO F0h SEARCH NO CCh SKIP NO YES DS2720 Tx FAMILY CODE 1 BYTE YES MASTER Tx BIT 0 YES DS2720 Tx BIT 0 DS2720 Tx BIT 0 MASTER Tx BIT 0 YES A5h RESUME NO DS2720 Tx SERIAL NUMBER 6 BYTES BIT 0 MATCH ? DS2720 Tx CRC 1 BYTE NO NO BIT 0 MATCH ? YES RESUME FLAG SET? NO YES MASTER Tx BIT 1 YES DS2720 Tx BIT 1 DS2720 Tx BIT 1 MASTER Tx BIT 1 CLEAR RESUME FLAG YES CLEAR RESUME FLAG BIT 1 MATCH ? NO NO BIT 1 MATCH ? MASTER Tx FUNCTION COMMAND YES YES MASTER Tx BIT 63 DS2720 Tx BIT 63 DS2720 Tx BIT 63 MASTER Tx BIT 63 YES BIT 63 MATCH ? Set Resume Flag NO MASTER Tx FUNCTION COMMAND CLEAR RESUME FLAG 16 of 21 DS2720 I/O SIGNALING The 1-Wire bus requires strict signaling protocols to insure data integrity. The four protocols used by the DS2720 are the initialization sequence (reset pulse followed by presence pulse), write 0, write 1, and read data. All of these types of signaling except the presence pulse are initiated by the bus master. The initialization sequence required to begin any communication with the DS2720 is shown in Figure 12. A presence pulse following a reset pulse indicates the DS2720 is ready to accept a net address command. The bus master transmits (Tx) a reset pulse for tRSTL. The bus master then releases the line and goes into receive mode (Rx). The 1-Wire bus line is then pulled high by the pullup resistor. After detecting the rising edge on the DQ pin, the DS2720 waits for tPDH and then transmits the presence pulse for tPDL. Figure 12. 1-WIRE INITIALIZATION SEQUENCE tRSTL tPDH DQ VSS LINE TYPE LEGEND: BUS MASTER ACTIVE LOW BOTH BUS MASTER AND DS2720 ACTIVE LOW DS2720 ACTIVE LOW RESISTOR PULLUP tRSTH tPDL VDQ 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 1 and write 0. All write-time slots must be tSLOT (60ms to 120ms) in duration with a 1ms minimum recovery time, tREC, between cycles. The DS2720 samples the 1-Wire bus line between 15ms and 60ms after the line falls. If the line is high when sampled, a write 1 occurs. If the line is low when sampled, a write 0 occurs (see Figure 13). For the bus master to generate a write 1 time slot, the bus line must be pulled low and then released, allowing the line to be pulled high within 15ms after the start of the write time slot. For the host to generate a write 0 time slot, the bus line must be pulled low and held low for the duration of the write-time slot. READ-TIME SLOTS 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 DS2720 to present valid data. The bus master can then sample the data tRDV (15ms) from the start of the read-time slot. By the end of the read-time slot, the DS2720 releases the bus line and allows it to be pulled high by the external pullup resistor. All read-time slots must be tSLOT (60ms to 120ms) in duration with a 1ms minimum recovery time, tREC, between cycles. See Figure 13 for more information. 17 of 21 DS2720 Figure 13. 1-WIRE WRITE- AND READ-TIME SLOTS WRITE 0 SLOT WRITE 1 SLOT tSLOT tLOW0 tREC DQ tLOW1 tSLOT VDQ VSS DS2720 SAMPLE WINDOW MIN TYP MAX 15ms 15ms 30ms >1ms 15ms DS2720 SAMPLE WINDOW MIN TYP MAX 15ms 30ms READ 0 SLOT READ 1 SLOT tSLOT tREC tSLOT VDQ DQ VSS MASTER SAMPLE WINDOW >1ms MASTER SAMPLE WINDOW tRDV LINE TYPE LEGEND: BUS MASTER ACTIVE LOW BOTH BUS MASTER AND DS2720 ACTIVE LOW tRDV DS2720 ACTIVE LOW RESISTOR PULLUP 18 of 21 DS2720 ABSOLUTE MAXIMUM RATINGS* Voltage on PLS, Relative to VSS Voltage on CC, DC, and CP Pins, Relative to VSS Voltage on any Other Pin, Relative to VSS Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +18V -0.3V to +12V -0.3V to +6V -40C to +85C -55C to +125C See IPC/JEDEC-STD-020A * 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. RECOMMENDED DC OPERATING CONDITIONS PARAMETER Supply Voltage Data Pin SYMBOL VDD DQ CONDITIONS (-20C to +70C, 2.5V VDD 5.5V) MIN 2.5 -0.3 TYP MAX 5.5 5.5 UNITS V V NOTES 1 1 DC ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL Active Current Sleep Mode Current Input Logic High: DQ Input Logic High: PS Input Logic Low: DQ Input Logic Low: PS Output Logic High: CC, DC Output Logic Low: CC Output Logic Low: DC Output Logic Low: DQ DQ Input Pulldown Current PS Pullup Current CC Pulldown Resistance DC Pulldown Resistance IACTIVE ISLEEP VIH1 VIH2 VIL1 VIL2 VOHCP VOLCC VOLDC VOL1 IPD IPS RCCPD RDCPD CONDITIONS DQ = VDD 0C TA 50C DQ = VDD DQ = 0V, PS floating (-20C to +70C, 2.5V VDD 4.5V) MIN TYP MAX UNITS mA mA mA NOTES 12.5 20 25 2 2 1.5 1.5 VDD 0.2V 2.5 V V 0.4 0.2 V V V V V V mA 1 1, 6 1 1 1 1 1, 7 1 RLOAD > 10MW RLOAD > 10MW RLOAD > 10MW VPLS 10V IOL = 4mA VDQ = 0.4V VPS = 0.4V 8.5 9.0 VDD VPLS 9.5 VDD + 0.1 VPLS + 0.1 0.4 0.1 0.5 100 1.2 12 2.5 nA 4 16 kW kW 19 of 21 DS2720 ELECTRICAL CHARACTERISTICS: PROTECTION CIRCUITRY PARAMETER Overvoltage Detect Charge Enable Undervoltage Detect Overtemperature Detect Overcurrent Detect Short-Circuit Detect Overvoltage Delay Undervoltage Delay Overcurrent Delay Short-Circuit Delay Test Resistance, ITST Active Test Resistance, Recovery Charging Charger Detect Voltage SYMBOL VOVA VOVB VOVC VCE VUV TMAX VOC VSC tOVD tUVD tOCD tSCD RTST1 RTST2 VCH MIN 4.250 4.325 4.275 Typ 75mV Typ 120mV 70 140 2.0 0.75 90 12 50 3 TYP 4.275 4.350 4.300 (0C to +50C, 2.5V VDD 4.5V) MAX 4.300 4.375 4.325 Typ + 75mV Typ + 120mV 110 260 2.6 1.25 160 20 150 11 UNITS NOTES V V V C mV V s ms ms ms 1, 3 1, 3 1, 3 3 1, 3 1 3 3 3 5 5 VOV/1.022 VOV/1.55 90 200 2.3 1.0 125 16 100 kW kW mV 5 20 60 15 120 ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE PARAMETER Time Slot Recovery Time Write 0 Low Time Write 1 Low Time Read Data Valid Reset Time High Reset Time Low Presence Detect High Presence Detect Low Active Transition to CC/DC Engage DQ Capacitance SYMBOL tSLOT tREC tLOW0 tLOW1 tRDV tRSTH tRSTL tPDH tPDL MIN 60 1 60 1 TYP (-20C to +70C, 2.5V VDD 5.5V) MAX 120 UNITS ms ms ms ms ms ms ms ms ms NOTES 120 15 15 960 60 240 100 25 480 480 15 60 tON CDQ ms pF 4 20 of 21 DS2720 EEPROM RELIABILITY SPECIFICATION: PARAMETER SYMBOL MIN (-20C to +70C, 2.5V VDD 5.5V) TYP MAX UNITS NOTES Copy to EEPROM Time EEPROM Copy Endurance EEPROM Data Retention tEEC NEEC tEEDR 1 25,000 4 5 ms cycles years NOTES 1. 2. 3. 4. 5. 6. 7. 8. All voltages are referenced to VSS. Specified with no resistive load on CC, DC, or CP. Contact the factory for different voltage trip points and delay periods. Typical load capacitance on CC, DC is 1000pF CP (charge pump reservoir cap) = 0.1mF. DC load total on CC, DC, CP > 10MW. RTST = |VPLS - VDD| / I measured, with VPLS = 3.2V, VDD = 3.6V when test current, ITST, active for RTST1 ; and VPLS = 4.0V, VDD = 2.5V when recovery charging for RTST2. Maximum high-to-low fall time is 5ms. Internal 10V clamp on DC pin limits DC output logic low when PLS > 10V Short-circuit delay tested with VDD ramped from 3.1V to 1.9V in 5ms. Delay measured from VDD = 2.5V to DC pin fall to 7V from VOHCP. 21 of 21 |
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