LTC4110

LTC4110 Battery Backup System Manager FEATURES n DESCRIPTION The LTC®4110 is a complete single chip, high efficiency, flyback battery charge and discharge manager with automatic switchover between the input supply and the backup battery or super capacitor. The IC provides four modes of operation: battery backup, battery charge, battery calibration and shutdown. Battery backup and battery charge are automatic standalone modes, while the optional calibration mode requires a CPU host to communicate over an SMBus. During calibration the flyback charger is used in reverse to discharge the battery with a programmable constant current into the system load eliminating heat generation. Three status outputs can be individually reconfigured over the SMBus to become GPIOs. User programmable overdischarge protection is provided. The SHDN pin isolates the battery to support shipping the product with a charged battery installed. Multiple LTC4110s can be combined to form a redundant battery backup system or increase the number of battery packs to achieve longer backup run times. The LTC4110 is available in a low profile (0.75mm), 38-pin 5mm × 7mm QFN package. The QFN features an exposed metal die mount pad for optimum thermal performance. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. n n n n n n n n n n n n n Complete Backup Battery Manager for Li-Ion/ Polymer, Lead Acid, NiMH/NiCd Batteries and Super Capacitors Charge and Discharge Battery with Voltages Above and Below the Input Supply Voltage “No Heat” Battery Calibration Discharge Using System Load Automatic Battery Backup with Input Supply Removal Using PowerPath™ Control Standalone for Li-Ion/Polymer, SLA, and Supercaps Optional SMBus/I2C Support Allows Battery Capacity Calibration Operation with Host Over- and Under-Battery Voltage Protection Adjustable Battery Float Voltage Precision Charge Voltage ±0.5% Programmable Charge/Calibration Current Up to 3A with ±3% Accuracy Optional Temperature Qualified Charging Wide Backup Battery Supply Range: 2.7V to 19V Wide Input Supply Range: 4.5V to 19V 38-Lead (5mm × 7mm) QFN Package APPLICATIONS n n n n Backup Battery Systems Server Memory Backup Medical Equipment High Reliability Systems TYPICAL APPLICATION Battery Backup System Manager SYSTEM LOAD DCIN 0V OFF ON ON BACKUP LOAD (DCOUT) CURRENT FLOW LTC4110 BATTERY BACKUP SYSTEM MANAGER BATTERY HOST CPU INID UVLO SET POINT DCDIV BATID LTC4110 CHGFET DCHFET I2C BUS 4110 TA01b Server Backup System (In Backup Mode) SYSTEM LOAD (DC/DC, ETC.) BACKUP LOAD (MEMORY, ETC.) CURRENT FLOW BATTERY 4110 F01 4110fa 1 LTC4110 ABSOLUTE MAXIMUM RATINGS (Note 1) PIN CONFIGURATION TOP VIEW CHGFET DCHFET 31 BAT 30 SELC 29 ISENSE 28 SGND 27 CSN 39 26 CSP 25 ITH 24 ICHG 23 ICAL 22 IPCC 21 THB 20 THA 13 14 15 16 17 18 19 VCAL TIMER VDIS VCHG ACPb TYPE VREF DCOUT BATID INID VDD NC DCIN, BAT, DCOUT, DCDIV, SHDN to GND ....................................................... –0.3V to 20V Input Voltage (CLP CLN) ...............–0.3V to DCIN + 0.3V , Input Voltage (CSP CSN) ................–0.3V to BAT + 0.3V , Input Voltage (GPIO1, GPIO2, GPIO3, SELC, SELA, TYPE, VCHG, THA, THB, ISENSE, ACPDLY, SDA, SCL) .... –0.3V to 7V Input Voltage (VCAL, VDIS) ....................... –0.3V to 1.35V Output Voltage (ACPb, GPIO1, GPIO2, GPIO3) ................ –0.3V to 7V CLP-CLN, CSP-CSN ..................................................±1V Operating Temperature Range (Note 2)....–40°C to 85°C Junction Temperature (Note 3) ............................. 105°C Storage Temperature Range QFN Package......................................–65°C to 125°C 38 37 36 35 34 33 32 DCIN 1 CLN 2 CLP 3 ACPDLY 4 DCDIV 5 SHDN 6 SDA 7 SCL 8 GPI01 9 GPI02 10 GPI03 11 SELA 12 UHF PACKAGE 38-LEAD (5mm 7mm) PLASTIC QFN TJMAX = 100°C, θJA = 34°C/W EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LTC4110EUHF#PBF LEAD BASED FINISH LTC4110EUHF TAPE AND REEL LTC4110EUHF#TRPBF TAPE AND REEL LTC4110EUHF#TR PART MARKING 4110 PART MARKING 4110 PACKAGE DESCRIPTION 38-Lead (5mm × 7mm) Plastic QFN PACKAGE DESCRIPTION 38-Lead (5mm × 7mm) Plastic QFN TEMPERATURE RANGE –40°C to 85°C TEMPERATURE RANGE –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 4110fa 2 LTC4110 ELECTRICAL CHARACTERISTICS SYMBOL Power Input DCIN DCOUT VBAT ISPLY IBIDL IBBU IBSD VUVI VUVD VUVH VDD VDD(MIN) VFTOL Operating Voltage Range Operating Voltage Range Operating Voltage Range Supply Current (IDCIN + IDCOUT) in Idle Mode (Note 4) Battery Current in Idle Mode (Notes 4 and 5) Battery Current in Backup Mode (Note 5) Battery Current in Shutdown (Note 5) Undervoltage Lockout Exit Threshold Undervoltage Lockout Entry Threshold Undervoltage Lockout Hysteresis Output Voltage Output Voltage Charge Float Voltage Accuracy No Load IDD = –10mA l l The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified, VDCIN = VDCOUT = VDCDIV = 12V, VBAT = 8.4V, GND = SGND = CLP = CLN = SHDN = 0V and RVREF = 49.9k. All currents into device pins are positive and all currents out of device pins are negative. All voltages are referenced to GND, unless otherwise specified. PARAMETER CONDITIONS Charge or Calibration Modes Charge or Calibration Modes Backup Mode Backup Mode l l l l MIN 4.5 4.5 2.7 2.7 TYP MAX 19 19 19 19 UNITS V V V V mA μA mA μA V V mV 2 30 VDCIN = 0 VSHDN = VBAT , VDCIN = 0 VDCIN Increasing VDCIN Decreasing l l 3 45 3 45 4.45 4.1 2 20 3.7 3.4 4 3.7 400 4.5 4.25 –0.5 –0.8 –1 –2 4.75 VDD Regulator 5 V V 0.5 0.8 1 2 % % % % Charging Performance 4.20V for Li-Ion. 2.35V for Lead Acid (Note 8) VCHG = GND –5°C < TA < 85°C (Note10) l –40°C < TA < 85°C 0.3V and –0.3V for Li-Ion Batteries, 0.15V and –0.15V for Lead Acid Batteries (Note 8) VCSP – VCSN =100mV VBAT ≥ 3.1V –40°C < TA < 85°C VBAT ≥ 3.3V (Note 8), VCSP – VCSN = 10mV; Li-Ion and NiMH/NiCd Batteries Only VBAT ≤ 3.3 (Note 8), VCSP – VCSN = 10mV; Li-Ion and NiMH/NiCd Batteries Only ISKVA ISRCA ISKCA IVCHG VBC VBCH VAR VARH Voltage Error Amplifier Sink Current at ITH Pin VITH = 2V Current Error Amplifier Source Current at ITH Pin VCHG Pin Bias Current Bulk Charge Threshold Voltage; VBAT Increasing (Note 8) Bulk Charge Threshold Voltage Hysteresis; VBAT Decreasing (Note 8) Auto Recharge Threshold Voltage; VBAT Decreasing Auto Recharge Threshold Hysteresis Voltage; VBAT Increasing VITH = 2V l VFATOL Charge Float Voltage Adjust Accuracy IBTOL Bulk Charge Current Accuracy (Note 7) –3 l 3 5 30 40 96 –24 24 % % % % μA μA μA –5 –30 –40 IPTOL Preconditioning and Wake-Up Current Accuracy (Note 7) Current Error Amplifier Sink Current at ITH Pin VITH = 2V VCHG = 1.25V Li-Ion, VCHG = GND NiMH/NiCd Li-Ion, VCHG = GND NiMH/NiCd Standard Li-Ion Only; Specified as Percentage of Float Voltage Standard Li-Ion Only; Specified as Percentage of Float Voltage 93 –100 2.80 0.84 100 3.00 0.90 85 40 95 2 97 3.20 0.96 nA V V mV mV % % 4110fa 3 LTC4110 ELECTRICAL CHARACTERISTICS SYMBOL VBOV PARAMETER Battery Overvoltage Threshold; VBAT Increasing Battery Overvoltage Threshold Hysteresis; VBAT Increasing. Reference Pin Voltage Range Programmed Timer Accuracy Time Between Receiving Valid ChargingCurrent() and ChargingVoltage() Commands. Wake-Up Timer. Calibration Cut-Off Default Voltage Accuracy; VBAT Decreasing 2.75V for Li-Ion, 1.93V for Lead Acid, VCAL = GND (Note 8), 0.95V for NiMH/NiCd CTIMER = 47nF The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified, VDCIN = VDCOUT = VDCDIV = 12V, VBAT = 8.4V, GND = SGND = CLP = CLN = SHDN = 0V and RVREF = 49.9k. All currents into device pins are positive and all currents out of device pins are negative. All voltages are referenced to GND, unless otherwise specified. CONDITIONS All Li-Ion, Lead Acid as Percentage of Float Voltage NiMH/NiCd (Note 8) All Li-Ion, Lead Acid as Percentage of Float Voltage NiMH/NiCd (Note 8) l l l MIN 105 1.80 TYP 107.5 1.85 2 40 MAX 110 1.90 UNITS % V % mV VBOVH VREF FTMR tTIMEOUT 1.208 –15 140 1.220 0 175 1.232 15 210 V % sec Calibration Performance VCTOL VCTOLH l –1.1 –1.3 85 50 40 1.1 1.3 % % mV mV mV Calibration Cut-Off Default Voltage Hysteresis; Li-Ion VBAT Increasing. (Note 8) Lead Acid NiMH/NiCd Calibration Cut-Off Voltage Adjust Accuracy Calibration Current Accuracy (Note 7) VCAL Pin Leakage Current Back-Drive Current Limit Threshold ±400mV for Li-Ion, ±300mV for Lead Acid, ±200mV for NiMH/NiCd (Note 8) VCSP – VCSN = –100mV VCAL = 1.25V VCLP – VCLN Decreasing VCLN = VDCIN l l l VCATOL IFTOL IVCAL IBDT IBDH VOVP VOVPH –1.5 –5 –100 7 10 1 1.5 5 100 13 % % nA mV mV Back-Drive Current Limit Threshold Hysteresis VCLP – VCLN Increasing VCLN = VDCIN Calibration Mode Input Overvoltage Comparator DCDIV Pin Threshold Calibration Mode Input Overvoltage Comparator DCDIV Pin Hysteresis AC Present Comparator DCDIV Pin Threshold AC Present Comparator DCDIV Pin Hysteresis AC Present Comparator DCDIV Pin Input Bias Current VDCDIV Rising VDCDIV Falling l 1.4 1.5 100 1.6 V mV AC Present and Discharge Cut-Off Comparators VAC VACH IAC tAC VDTOL VDTOLH VDCDIV Falling VDCDIV Rising VDCDIV = 1.25V l 1.196 1.22 50 1.244 100 V mV nA ACPb Pin Externally Programmed Falling Delay CACPDLY = 100nF RVREF = 49.9k, , VDCDIV Stepped From 1.17V to 1.30V Discharge Cut-Off Default Voltage Accuracy; VBAT Decreasing Discharge Cut-Off Default Voltage Hysteresis; VBAT Increasing (Note 8) Discharge Cut-Off Voltage Adjust Accuracy VDIS Pin Bias Current 2.75V for Li-Ion, 1.93V for Lead Acid, VDIS = GND, 0.95V for NiMH/NiCd Li-Ion Lead acid NiMH/NiCd ±400mV for Li-Ion, ±300mV for Lead Acid, ±200mV for NiMH/NiCd VDIS = 1.25V l l 8 –1.5 10 12 1.5 ms % mV mV mV 85 50 40 2 –100 2 100 VDATOL IVDIS % nA 4110fa 4 LTC4110 ELECTRICAL CHARACTERISTICS SYMBOL VFR VREV VGON VGOFF VFO PARAMETER Forward Regulation Voltage (VDCIN -VDCOUT , VBAT -VDCOUT) Reverse Voltage Turn-Off Voltage (VDCIN-VDCOUT, VBAT -VDCOUT) “ON” Gate Clamping Voltage (VDCIN -VINID , VBAT -VBATID ) The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified, VDCIN = VDCOUT = VDCDIV = 12V, VBAT = 8.4V, GND = SGND = CLP = CLN = SHDN = 0V and RVREF = 49.9k. All currents into device pins are positive and all currents out of device pins are negative. All voltages are referenced to GND, unless otherwise specified. CONDITIONS 2.7V ≤ VDCIN ≤ 19V 2.7V ≤ VDCIN ≤ 19V IINID , IBATID = 1μA l l MIN 10 –30 7 TYP 20 –18 8.3 MAX 32 –8 9.7 0.25 UNITS mV mV V V mV Input and Battery Ideal Diodes and Switches “OFF” Gate Voltage (VDCIN -VINID, VBAT -VBATID) IINID, IBATID = –10μA VSHDN = 0V and VDCIN (Shutdown) BATID Fast-On Voltage Comparator Threshold INID Pin Delay Times IBATID > 500μA CINID = 10nF DCIN is Switched Between 12.2V and 11.8V From DCOUT – VGOFF to DCOUT –6V From DCOUT – VGON to DCOUT –1.5V CBATID = 2.5nF BAT is Switched Between 12.2V and 11.8V From DCOUT – VGOFF to DCOUT –6V From DCOUT – VGON to DCOUT –1.5V ICHGFET, IDCHFET = –1mA ICHGFET, IDCHFET = 1mA VDCIN = VDCDIV = VDCOUT = 0V (Shutdown Mode), VDCIN = VDCDIV = 0V (Backup Mode) ICHGFET , IDCHFET = 1μA CLOAD = 1.6nF 10% to 90% , CLOAD = 1.6nF 10% to 90% , l 45 100 tIIDON tIIDOFF Turn “ON” Turn “OFF” BATID Pin Delay Times 450 8 700 20 μs μs tBIDON tBIDOFF VOHF VOLF VOLFX Turn “ON” Turn “OFF” CHGFET, DCHFET High CHGFET, DCHFET Low CHGFET, DCHFET in Shutdown and Backup Modes CHGFET, DCHFET Transition Times Rise Time Fall Time PWM Oscillator Switching Frequency SafetySignal Decoder SafetySignal Trip (RES_COLD/RES_OR) SafetySignal Decoder SafetySignal Trip (RES_IDEAL/RES_COLD) SafetySignal Decoder SafetySignal Trip (RES_HOT/RES_IDEAL) SafetySignal Decoder SafetySignal Trip (RES_UR/RES_HOT) THB Pin Hot Threshold Voltage THB Pin Hot Threshold Hysteresis Voltage THB Pin Battery Removal Threshold Voltage 15 8 4.5 4.75 60 20 5.25 50 100 μs μs V mV mV PWM Flyback Converter tR tF FPWM SSOR 35 15 255 300 65 65 340 ns ns kHz SafetySignal Decoder and Thermistor Interface RTHA = 1130Ω ±1%, CTH = 1nF (Note 6) RTHB l = 54.9k ±1%. Smart Batteries and Li-Ion Only RTHA = 1130Ω ±1%, CTH = 1nF (Note 6) RTHB l = 54.9k ±1% Smart Batteries and Li-Ion Only RTHA = 1130Ω ±1%, CTH = 1nF (Note 6) RTHB l = 54.9k ±1% Smart Batteries and Li-Ion Only RTHA = 1130Ω ±1%, CTH = 1nF (Note 6) RTHB l = 54.9k ±1% Smart Batteries and Li-Ion Only VTHB Decreasing; Lead Acid Only VTHB Increasing; Lead Acid Only VTHB Increasing; Lead Acid Only l l 95 100 105 k SSCLD 28.5 30 31.5 k SSIDL 2.85 3 3.15 k SSHOT 425 0.28 • VTHA 0.90 • VTHA 500 0.30 • VTHA 50 0.94 • VTHA 575 0.36 • VTHA 0.96 • VTHA Ω V mV V VHOT VHOTH VREM 4110fa 5 LTC4110 ELECTRICAL CHARACTERISTICS SYMBOL VREMH PARAMETER THB Pin Battery Removal Threshold Hysteresis Voltage SCL/SDA Input Pins Low Voltage SCL/SDA Input Pins High Voltage SDA Output Pin Low Voltage ACPb, GPIO1,2,3 Output Pins Low Voltage ACPb, GPIO1,2,3 Output Pins Open Leakage Current GPIO Input Low Voltage GPIO Input High Voltage SHDN Input Pin Low Voltage SHDN Input Pin High Voltage SHDN Input Pin Pull-Up Current Logic Reset Duration After Power-Up From Zero SCL Serial Clock High Period SCL Serial Clock Low Period Timeout Period SDA/SCL Fall Time Start Condition Set-Up Time Start Condition Hold Time SDA to SCL Falling-Edge Hold Time, Slave Clocking in Data CLOAD = 250pF RPU = 9.31k , VSHDN = 2.4V VDCIN Transition From 0V to 5V in 1V between the CLP and CLN pins may damage the device. ACPDLY (Pin 4): ACPb Delay Control Pin. A capacitor connected from ACPDLY to GND and a resistor from VREF to GND programs delay in the ACPb pin high-to-low transition. Open if minimum delay is desired. DCDIV (Pin 5): AC Present Detection Input. Backup operation is invoked when the system power voltage, divided by an external resistor divider, falls below the threshold of this pin. SHDN (Pin 6): Active High Shutdown/Reset Control Logic Input. Forces micropower shutdown mode if high when DCIN supply is removed. Forces all registers to reset if high when DCIN supply is present. Normally tied to ground. Internal pin pull-up current. SDA (Pin 7): SMBus Bidirectional Data Signal. Connect to VDD when not in use. SCL (Pin 8): SMBus Clock Signal Input From SMBus Host. Connect to VDD when not in use. GPIO1 (Pin 9): General Purpose I/O or Charge Status Pin. A logic-level I/O bit port that is configurable as a host-driven input/output port or as a battery charge status output (CHGb) with an open-drain N-MOSFET that is asserted low when any smart battery or Li-Ion battery is in any phase of charging or when lead acid battery charge current is >C/x where: C x= •5 ICHG (See C/x Charge Termination section for more details). If the No SMBus option is selected with the SELA pin, the GPIO1 pin defaults as battery charge status. Refer to Table 5a. GPIO2 (Pin 10): General Purpose I/O Pin. A logic-level I/O bit port that is configurable as a host-driven input/output port or as a battery undervoltage status output (BKUP_FLTb) with an open-drain N-MOSFET that is asserted low only while in backup mode if the battery’s average cell voltage drops below voltage programmed by the VDIS pin. If the No SMBus option is selected with the SELA pin, then the GPIO2 pin defaults as battery undervoltage status. Refer to Table 5c. GPIO3 (Pin 11): General Purpose I/O Pin. A logic-level I/O bit port that is configurable as a host-driven input/output port or as a calibration complete status output (CAL_COMPLETEb) with an open-drain N-MOSFET that is asserted low when calibration has been completed. If the SELA pin is programmed for no SMBus use then the status output is charge fault (CHGFLTb) instead of calibration complete. Refer to Table 5e. SELA (Pin 12): SMBus Address Selection Input. Selects the LTC4110 SMBus address to facilitate redundant backup systems when standard batteries are used. Connect to GND for 12h, VDD for 28h and the VREF pin for 20h. When a smart battery is selected by the TYPE pin, the SELA pin must be connected to GND to select address 12h. If the SMBus is not used or to force all GPIOs to status mode upon power-up, connect pin to a typically 0.5 • VREF voltage from VREF pin resistor divider. The SMBus address, if used, will be 12h. 4110fa 8 LTC4110 PIN FUNCTIONS ACPb (Pin 13): AC Present Status Digital Output. OpenDrain N-MOSFET output is asserted low when the main supply is present as detected by the DCDIV pin and internal DCIN UVLO. VDIS (Pin 14): Battery Discharge Voltage Limit During Backup Program Input. Battery threshold voltage at which backup mode will terminate by turning off the isolation P-MOSFET with the BATID pin. Adjustable from external resistor string biased from VREF pin. For default threshold connect to GND pin. VCAL (Pin 15): Battery Voltage Limit During Calibration Program Input. Battery threshold voltage at which calibration will terminate. Adjustable from external resistor string biased from VREF pin. For default threshold connect to GND pin. VCHG (Pin 16): Battery Float Voltage Program Input. Trims the float voltage during charging. Programmed from external resistor string biased from VREF pin. Connect to GND for default float voltage. VREF (Pin 17): Voltage Reference Output and Timing Programming Input. Provides a typical virtual reference of 1.220V (VREF) for an external resistor divider tied between this pin and GND that programs the VCHG, VCAL and VDIS pin functions. Total resistance from VREF to GND, along with the capacitor on the timer pin, programs the charge time. Voltage reference output remains active in all modes except shutdown. Load current must be between 10μA and 25μA. TIMER (Pin 18): Charge Timing Input. A capacitor connected between TIMER and GND along with the resistance connected from VREF to GND programs the charge time intervals. TYPE (Pin 19): Refer to Table 8. THA (Pin 20): SafetySignal Force/Sense Pin to Smart Battery and Force Pin to Lead Acid Battery Thermistor. See description of operation for more detail. The maximum allowed combined capacitance on THA, THB and SafetySignal is 1nF For lead acid battery applications the . maximum capacitance on the THA pin is 50pF . THB (Pin 21): SafetySignal Force/Sense Pin to Smart Battery and Sense Pin to Lead Acid Battery Thermistor. See description of operation for more detail. The maximum allowed combined capacitance on THA, THB and SafetySignal is 1nF . IPCC (Pin 22): Battery Preconditioning Charge Current Program Input. Programs the battery current during preconditioning or wakeup charging. Programmed from external resistor to GND. ICAL (Pin 23): Battery Discharge Current During Calibration Program Input. Programs the constant discharge current at the battery during calibration. Programmed from external resistor to GND. ICHG (Pin 24): Battery Current During Charge Program Input. Programs the battery current while constant-current bulk charging. Programmed from external resistor to GND. ITH (Pin 25): Control Signal of the Current Mode PWM. AC compensates control loop. Higher ITH voltage corresponds to higher charging current. CSP (Pin 26): Current Sense Positive Input. This pin and the CSN pin measure voltage across the external current sense resistor to control battery current during charging and calibration. CSN (Pin 27): Current Sense Negative Input. This pin and the CSP pin measure voltage across the external current sense resistor to control battery current during charging and calibration. SGND (Pin 28): Signal Ground Reference Input. This pin should be Kelvin connected to the flyback current sense resistor and to the battery return. ISENSE (Pin 29): Current Sense Input. Senses current in the flyback transformer by monitoring voltage across the external current sense resistor. This pin should be Kelvinconnected to the resistor. SELC (Pin 30): Refer to Table 8. 4110fa 9 LTC4110 PIN FUNCTIONS BAT (Pin 31): Battery Voltage Sense Input. This pin is used to monitor the battery and control charging voltage through an internal resistor divider connected to this pin that is disconnected in shutdown mode. Also provides a control input for battery ideal diode functions. Pin should be Kelvinconnected to battery to avoid voltage drop errors. DCHFET (Pin 32): Drives the Gate of an External N-MOSFET. Used to drive energy into the battery side of the high efficiency switch mode converter during low loss calibration discharge of the battery. Provides synchronous rectification during battery charging. CHGFET (Pin 33): Drives the Gate of an External NMOSFET. Used to drive energy into the supply side of the high efficiency switch mode converter during battery charging. Provides synchronous rectification during low loss calibration mode. VDD (Pin 34): Bypass Capacitor Connection for Internal VDD Regulator. Bypass at pin with 100nF low ESR capacitor to GND. BATID (Pin 35): Drives the Gate of the Battery P-MOSFET Ideal Diode. Controls low loss ideal diode between the battery and backup load when in backup mode. When not in backup mode, the P-MOSFET is turned off to prevent battery power from back driving into main power. NC (Pin 36): No Connect. DCOUT (Pin 37): System Power Output Voltage Monitor Input. Provides a control input for supply input ideal diode and battery ideal diode functions. Also supplies power to the IC. Bypass at pin with 100nF low ESR capacitor to GND. INID (Pin 38): Drives the Gate of the Supply Input P-MOSFET Ideal Diode. Controls low loss ideal diode between the supply input and backup load when not in backup mode. Exposed Pad (Pin 39): Ground. The Exposed Pad must be soldered to the PCB. 4110fa 10 LTC4110 BLOCK DIAGRAM 37 DCOUT INID 38 DCIN 1 SUPPLY INPUT BATTERY PowerPath CONTROLLER 36 NC 35 BATID 31 BAT CA PRECISION VOLTAGE DIVIDER CHG/DCH SWITCH CURRENT SELECTION 22 IPCC EA CLP 3 CLN 2 DCDIV 5 VREF 17 VCHG 16 VCAL 15 VDIS 14 SELC 30 PROGRAMMING CURRENT TYPE 19 SHDN 6 UVLO SDA 7 SCL 8 SELA 12 THA 20 THB 21 SMBus INTERFACE AND CONTROL 13 ACPb TIMER/ CONTROLLER 9 GPIO1 THERMISTOR INTERFACE 10 GPIO2 11 GPIO3 OSC 29 ISENSE 28 SGND 18 TIMER 4 ACPDLY VDD 34 VDD REGULATOR NUMBER OF CELLS 1.220 CURRENT SWITCH ÷10 + – VOLTAGE REFERENCE ANALOG COMPARATORS AND SWITCHES PWM LOGIC 32 DCHFET + – GND 39 27 CSN 26 CSP + – 24 ICHG 23 ICAL 25 ITH 33 CHGFET 4110 BD 4110fa 11 LTC4110 OPERATION OVERVIEW In the typical application, the LTC4110 is placed in series with main power supply that powers all or part of the system, which must include the device(s) or system that needs battery backup. The LTC4110 has four modes of operation: • Battery Backup Mode • Battery Charge Mode • Battery Calibration Mode • Shutdown Mode The LTC4110 provides complete PowerPath control for the battery backed up load switching automatically from the main power supply to the battery when battery backup mode is required. Low loss ideal diode FET switches are used to connect the main supply or the battery to the backup load which permit multiple LTC4110’s to work together in a scalable fashion to permit longer backup times, redundancy and/or higher load currents. In battery charge mode, power is drawn from the main supply by a high efficiency synchronous flyback charger. The LTC4110 maintains the state of charge (SOC) of the battery at all times so the battery is ready at all times. Use of a flyback converter permits charging of batteries who’s termination voltage can be greater than the main supply voltage, while at the same time providing high DC isolation to minimize parasitic drain on the battery. Testing, maintenance support and capacity verification of the battery is supported through the LTC4110’s calibration mode. In calibration mode, the same synchronous flyback used to charge the battery is Table 1. LTC4110 Battery Pack Charge Mode Capabilities BATTERY TYPE Li-Ion/Polymer Standard Battery Smart Battery Yes Yes CHEMISTRY Nickel No Yes SLA/Lead Acid Yes Yes Adj. Up to 12 Hours Unlimited MAXIMUM CHARGE TIME (SLA EXCLUDED) also used in reverse to allow safe controlled discharge of the battery back into the main supply eliminating wasted heat and energy. The product will not need to provide any additional thermal management to support this mode. Shutdown mode disconnects the battery from the load to preserve capacity and permits shipping the product with an energized battery installed at the factory, eliminating battery installation at the site. The LTC4110 supports optional control and monitoring of all activities by a host including faults over the industry standard SMBus, which is a variation of the I2C bus. However no host is required as the LTC4110 is fully functional in a standalone mode. Combining all these functions into a single IC reduces circuit area compared to presently available solutions. The LTC4110 is designed to work with both standard battery and smart battery configurations. Smart batteries are standard batteries with industry standard gas gauge electronics built in offering accurate SOC information for the host. Furthermore, being intimate with all aspects of the battery, it also has the ability to control the charge process. Smart batteries use the SMBus as the communication bus for data exchange and charge control. For more information about smart batteries, see www. sbs-forum.org for specifications or contact Linear Technology Applications. It is important to know that the LTC4110 uses the TYPE pin to learn what type of battery it will be working with. The TYPE pin setting globally affects all of the operating modes, options including GPIO and control ranges. Table 1 and Table 2 give you a complete breakdown of all the battery types supported relative to the TYPE pin settings Table 2. LTC4110 Battery Pack Charge Voltage Capabilities CHEMISTRY Lead Acid Li-Ion/Polymer NiMH/NiCd Super Caps VCELL FULL CHARGE 2.35V 4.2V N/A 2.5V, 2.7V or 3V VCELL ADJ. RANGE ±0.15V ±0.3V N/A Yes SERIES CELL COUNT 2, 3, 5 and 6 1, 2, 3 and 4 4, 6, 9 and 10 2 to 7 NOMINAL STACK VOLTAGE (V) 4, 6, 10 and 12 3.6, 7.2, 10.8 and 14.4 4.8, 7.2, 10.8 and 12 5 to 18 4110fa 12 LTC4110 OPERATION and ranges. It should be noted that even if the LTC4110 TYPE pin is not set to a smart battery mode, any SMBus commands sent by a host or a smart battery are still acted upon. For SuperCap support, see the Applications Information section. BATTERY BACKUP MODE Figure 1 shows the LTC4110 in backup mode and the corresponding PowerPath enabled. The LTC4110 use the DCDIV pin to typically monitor the DCIN voltage through an external resistor divider. The DCDIV pin sets the backup mode threshold voltage and senses the need to enter backup mode. DCDIV can alternately be driven with other signals such as logic. When the DCDIV pin voltage drops below the AC present threshold voltage (see VAC) backup mode is entered. Backup mode is also entered whenever the internal undervoltage lockout, UVLO, senses that DCIN (VUVD) or DCOUT has fallen to excessively low voltages. In backup mode the battery P-MOSFET ideal diode is enabled to backup the load from the battery. The supply input P-MOSFET ideal diode isolates the main supply input from the load and the flyback switcher N-MOSFETs are inhibited from turning on. Also, after the threshold is passed, hysteresis (VACH) is switched in. When the supply is returning and the AC present threshold voltage plus the hysteresis voltage is reached on the DCDIV pin, both of the battery P-MOSFETs are rapidly switched off (tdDOFF) and the supply input P-MOSFET ideal diode provides the load current. When forward biased, the ideal diodes regulate their forward voltage drop to 20mV typical (VFR) when the SYSTEM LOAD DCIN 0V OFF ON ON BACKUP LOAD (DCOUT) CURRENT FLOW MOSFET is sufficiently sized. If the voltage input falls and results in a forward voltage below 20mV, then the ideal diode will begin turning off at a slow rate. Should the ideal diode see a –18mV typical (VREV) or lower reverse voltage, the ideal diode will turn off quickly (tdDOFF). While in backup, the battery’s average cell voltage is monitored to protect the battery from excessive discharge. If the cell voltage drops below the value programmed by the VDIS pin (Li-Ion default = 2.75V/cell, NiMH/NiCd default = 0.95V/cell, lead acid default = 1.93V/cell), the battery P-MOSFETs are rapidly turned off and the battery is disconnected from the load. If DCIN is above UVLO, the load and the LTC4110 will be powered from the supply input. If DCIN is below UVLO, the LTC4110 enters the micropower shutdown mode (see the Shutdown Mode section for more details). Also, the SMBus accessible BKUP_FLT fault bit is set and maintained as long as sufficient battery voltage is present (VBAT ≥ 2.7V). This fault bit can be read after DCIN returns to a voltage level exceeding the internal UVLO threshold (see VUVI) and DCOUT has regained sufficient voltage (see DCOUT) to provide internal power. If the GPIO2 port is programmed as the BKUP_FLTb status output after DCIN returns, it will be forced low to represent an inverted BKUP_FLT bit. When DCIN returns, as sensed by the UVLO, the shutdown mode is automatically cancelled and normal operation can resume, however, the BKUP_FLT bit remains set until either the SHDN pin is set high (all registers reset) or register bits POR_RESET or BUFLT_RST are set. See the Shutdown Mode section for details. During backup, the external thermistor network is monitored for battery presence. BATTERY CHARGE MODE Figure 2 shows the charge path to charge a battery. Current is pulled from the supply input to charge the battery. At the same time, the input supply provides power to both the system load and the backup load. The battery is isolated from the load at all times so it cannot affect charger terminations algorithms. If we ignore battery chemistry for a moment, as far as the LTC4110 charger is concerned, there are only two basic charge modes. When the TYPE pin selects a standard battery mode, charge termination is controlled by the LTC4110 4110fa BATTERY INID UVLO SET POINT DCDIV BATID LTC4110 CHGFET DCHFET 4110 F01 Figure 1. Backup Mode Operation 13 LTC4110 OPERATION SYSTEM LOAD BACKUP LOAD DCIN ON OFF OFF CURRENT FLOW BATTERY current sense resistor (RSNS(BAT)) and CSP/CSN pin resistors. The constant voltage (float voltage) is programmed to one of four values (4.2V, 8.4V, 12.6V, 16.8V) depending on the number of series cells using the SELC pin and can be adjusted ±0.3V/cell with the VCHG pin. If adjusted, the auto recharge threshold and overvoltage threshold will track proportionally. The charge cycle begins when the supply input is present as sensed by the DCDIV pin and DCIN above UVLO, the battery cell voltage is below the auto recharge threshold (95% of the programmed float voltage; see VAR), thermistor temperature is within ideal limits, COLD, under range (see SafetySignal Decoder section) or is optioned out and the register bit CHARGE_INHIBIT is cleared (see Tables 6 and 7 for register details). Soft-start ramps the charge current at a rate set by the capacitor on the ITH pin. When charging begins, the programmable timer initiates timing and the CHGb (GPIO1 pin) status output is pulled LOW. An external capacitor on the TIMER pin, along with the current set by the total series resistance connected to the VREF pin, sets the total charge time. If the battery voltage is less than the 3.0V/cell bulk charge threshold (VBC), the charger will begin with a preconditioning trickle charge current. The trickle current is programmed by the resistor (RPCC) from the IPCC pin to ground. During preconditioning trickle charging, if the battery voltage stays below the bulk charge threshold (VBC) 25% of the programmed bulk charge time, the battery may be defective and the charge sequence will be terminated immediately. To indicate this fault, the CHGb (GPIO1 pin) becomes high impedance, the CHG_STATE_0 and CHG_STATE_1 register bits will be set low and CHG_FLT register bit will be set high. Charge is terminated and the timer reset until the fault is cleared by the RESET_TO_ZERO or POR_RESET SMBus write commands, SHDN pin toggle or the battery removed and replaced. Removing the supply input will not clear the fault if the battery is present. If the battery voltage exceeds 107.5% (VBOV) of the programmed float voltage during any stage of charge, the charger pauses until the voltage drops below the hysteresis (VBOVH). The timer is not stopped and no fault is indicated. 4110fa INID LTC4110 BATID CHGFET DCHFET 4110 F02 Figure 2. Charge Mode Operation for the battery chemistry selected. Specifically the TIMER pin becomes active and used to detect faults conditions or terminate the charge cycle itself as needed. Smart battery SMBus charge control commands are still honored if any are sent at any time. A smart battery can safely function in a standard battery mode if identical in chemistry and voltage configuration as the standard battery. When the TYPE pin selects a smart battery mode, this simply disables the TIMER pin and its function in charge termination. The smart battery is able to restart or terminate a charge cycle at any time using charge commands over the SMBus. This mode also enables smart battery wake-up and watchdog functions based on tTIMEOUT per the smart battery standards. However it is not recommended to use a standard battery with a LTC4110 configured for smart battery mode operation. You can shorten battery life, damage or destroy the battery. In the extreme case this can cause an explosion since no charge termination mechanisms are active. The following sections explain detailed operation for each charge mode as selected by the TYPE pin. STANDARD LI-ION/POLYMER BATTERY CHARGE MODE The charger is programmed for standard Li-Ion batteries by connecting the TYPE pin to GND. During Li-Ion charging, the LTC4110 operates as a high efficiency, synchronous, PWM flyback battery charger with constant-current and constant float voltage regions of operation. The constantcharge current is programmed by the combination of a resistor (RCHG) from the ICHG pin to ground, a battery 14 LTC4110 OPERATION PWM STOPPED (BATTERY OVP) 14 ANY CHARGE STATE 8 STOP CHARGE (OVERTEMPERATURE) 15 RESUME CHARGE STATE 9 2 BULK CHARGE 3 RESET 10 ANY CHARGE STATE 7, 12, 13 11 (BATTERY NEEDS RECHARGE) 5 (PRE-CONDITIONING FAULT) 1 PRE-CONDITIONING CHARGE STOP CHARGE 4 (BATTERY FULL) TOP-OFF CHARGE 4110 F03 6 (BULK TIME FAULT) Figure 3. Standard Li-Ion Charge State Diagram (Does Not Include Calibration) # 1 Or Logic Event (T = True, F = False) [Notes] RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT = F & VBAT < VBC RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT=F & ChargingVoltage() ≠ 0 & ChargingCurrent() ≠ 0 VBAT > VBC C/5 = T Timer/4(Top Off = done [Battery is full] Timer/4(PreCond) = done before VBAT > VBC Timer(Bulk) = done before C/5 = T Or 8 9 10 Or Or Or Or 11 Or 12 Or Or Or 13 14 15 RESET_TO_ZERO = T [See ChargeMode()] CHARGE_INHIBIT=T [See ChargeMode()] RES_HOT = T & RES_UR = F [See ChargeStatus()] RES_HOT = F [See ChargeStatus()] DCDIV pin = F RES_OR = T [Bat Removed, See ChargeStatus()] SHDN pin = T VUVD = T POR_RESET = T [See ChargeMode()] VAR = T [AutoRestart] ChargingVoltage() & ChargingCurrent() ≠ 0 AlarmWarning() command is sent by Smart Battery over SMBus with any of the following bits set to True: OVER_CHARGED_ALARM TERMINATE_CHARGE_ALARM Reserved ALARM OVER_TEMPERATURE_ALARM ChargingVoltage() or ChargingCurrent() = 0 sent VBOV = T [Battery Overvoltage] VBOV = F Notes and/or Actions (T = True, F = False) IPPC & Timer/4(PreCond) = Started & CHG = T & ALARM_INHIBITED = F (RES_OR = F = Bat Inserted -> See ChargeStatus() ) (POR_RESET -> See ChargeMode() IPPC = Off & ICHG = On & Timer/4(PreCond) = Stopped & Timer(Bulk) = Started. Timer(Bulk) = Stopped & Timer/4(Top Off) = Started ICHG = Off & CHG = F (Typical Full State) IPPC = Off & CHG_FLT = T & CHG = F ICHG = Off & CHG_FLT = T & CHG = F ICHG or IPPC = Off & All Timers = Reset & CHG_FLT = F & CHG = F ICHG or IPPC = Off & CHG_FLT = T, Timers paused. , ICHG or IPPC = On & CHG_FLT = F Timers resume. ICHG or IPPC = Off & All Timers = Reset & ALARM_INHIBITED = F & CHG_FLT = F & CHG = F & CHARGE_INHIBITED = F 2 3 4 5 6 7 (The battery needs another charge cycle or Smart Battery has requested to start another cycle.) ICHG or IPPC = Off & All Timers = Reset & CHG = F & ALARM_INHIBITED = T (ALARM_INHIBITED bit is found in ChargeStatus()) ICHG or IPPC = Off & CHG = F PWM stopped. Timers remain running. PWM restarted. Note: For all charge states, VCHG is always active. 4110fa 15 LTC4110 OPERATION When the battery voltage exceeds the bulk charge threshold (VBC), the charger begins the bulk charge portion of the charge cycle. As the battery accepts charge, the voltage increases. Constant-current charge continues until the battery approaches the constant voltage. At this time, the charge current will begin to drop, signaling the beginning of the constant-voltage portion of the charge cycle. The charger will maintain the constant voltage across the battery until either C/x is reached or 100% of the programmed bulk charge time has elapsed during bulk charge. When the current drops to approximately 20% of the full-scale charge current, an internal C/x comparator will initiate the start of the top-off stage. The top-off stage charges for 25% of the total programmed bulk charge time. When the time elapses, charge is terminated and CHGb (GPIO1 pin) is forced to a high impedance state and CHG_STATE_0 and CHG_STATE_1 register bits will be set low. Should the total bulk charge time elapse before C/x is reached, charge is terminated and a CHG_FLT fault is indicated until cleared by the RESET_TO_ZERO or POR_RESET SMBus write commands, SHDN pin toggle or the battery removed and replaced. Fault conditions are not cleared when the supply input is removed if the battery has sufficient voltage. An optional external thermistor network is sampled at regular intervals to monitor battery temperature and to detect battery presence. If the thermistor temperature is hot (see the SafetySignal Decoder section), the charge timer is paused, charge current is halted, CHG_FLTb (GPIO3 pin) is forced low and the CHG_FLT bit will be set high. CHGb (GPIO1 pin) , CHG_STATE_0 and CHG_STATE_1 register bits will not be affected. When the thermistor value returns to an acceptable value, charging resumes, CHG_FLTb (GPIO3 pin) returns to high impedance and the CHG_FLT bit will be reset low. An open thermistor indicates absence of a battery. To defeat the temperature monitoring function, replace the thermistor with a resistor to indicate ideal battery temperature. When a thermistor is not used, the resistor circuit must be routed through the battery connector if battery presence detection is required. After a charge cycle has ended without fault, the charge cycle is automatically restarted if the average battery cell voltage falls below the auto recharge threshold. At any time charging can be forced to stop by pulling the SHDN pin high or setting the CHARGE_INHIBIT bit high through the SMBus. SMART BATTERY CHARGE MODE This section explains operation for smart batteries with a SMBus interface. Smart Li-Ion is selected by connecting the TYPE pin to the VDD pin and smart Nickel (NiMH/NiCd) is selected by connecting the TYPE pin to the VREF pin. The LTC4110 only implements a subset of smart battery charger commands; the actual charging algorithm is determined by LTC4110 through external resistors even if the battery is “smart.” The LTC4110 operates as a high efficiency, synchronous, PWM flyback battery charger with constant current and constant float voltage regions of operation. The constantcharge current is programmed by the combination of a resistor (RCHG) from the ICHG pin to ground, a battery current sense resistor (RSNS(BAT)) and CSP/CSN pin resistors. For Li-Ion the constant voltage (float voltage) is programmed to one of four values (4.2V, 8.4V, 12.6V, 16.8V) depending on the number of series cells using the SELC pin and can be adjusted ±0.3V/cell with the VCHG pin. For nickel batteries the constant-voltage function is not used, however, a non-zero value is still required to be written to the ChargingVoltage() register. The internal auto recharge function is inhibited for smart batteries. If the battery voltage exceeds 107.5% (VBOV) of the programmed float voltage during any stage of charge, the charger pauses until the voltage drops below the hysteresis (VBOVH). The timer is not stopped and no fault is indicated. This function is disabled when nickel based smart batteries are used. There are four states associated with smart battery charge mode, namely: • SMBus Wake-Up Charge State • SMBus Preconditioning Charge State • SMBus Bulk Charge State • SMBus OFF State These states are explained in the following four sections. 4110fa 16 LTC4110 OPERATION PWM STOPPED (BATTERY OVP) 11 ANY CHARGE STATE 8 OFF (OVERTEMPERATURE) 12 RESUME CURRENT STATE 9 WAKE UP CHARGE 2 PRE-CONDITIONING CHARGE 3 BULK CHARGE 1 RESET 10 ANY CHARGE STATE 4, 7, 13, 14 OFF 4 (BATTERY FULL) 5 (BAD BATTERY) 6 (BATTERY RECHARGE REQUEST) 4110 F04 Figure 4. Smart Battery Charge State Diagram (Does Not Include Calibration) # 1 Or Logic Event (T = True, F = False) [Notes] RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT = F & RES_HOT = F RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT = F & RES_HOT = T & RES_UR = T ChargingVoltage() & ChargingCurrent() ≠ 0 sent VBAT > VBC ChargingVoltage() or ChargingCurrent() = 0 sent Timer/4(Pre-Charge) = Done before VBAT > VBC ChargingVoltage() & ChargingCurrent() ≠ 0 sent & RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT = F TTIMEOUT = Done (Dead Battery or Loss of SMBus) RES_HOT = T & RES_UR = F [See ChargeStatus()] RES_HOT = F [See ChargeStatus()] Or Or Or Or 11 12 13 Or 14 Or Or Or DCDIV pin = F RES_OR = T [Bat Removed, See ChargeStatus()] SHDN pin = T VUVD = T POR_RESET = T [See ChargeMode()] VBOV = T [Battery Overvoltage] VBOV = F RESET_TO_ZERO = T [See ChargeMode()] CHARGE_INHIBIT = T [See ChargeMode()] AlarmWarning() command is sent by Smart Battery over SMBus with any of the following bits set to True: OVER_CHARGED_ALARM TERMINATE_CHARGE_ALARM Reserved ALARM OVER_TEMPERATURE_ALARM Timer/4(Pre-Charge) = Started & TTIMEOUT disabled & ALARM_ INHIBITED = F IPPC = Off, ICHG = On, Timer/4(Pre-Charge) = Stopped & Timer(SMBus) = Started ICHG = Off & All Timers = Reset & CHG = F IPPC = Off & All Timers = Reset & CHG = F IPPC = On & Timer/4(Pre-Charge) = Started & CHG = T & ALARM_INHIBITED = F ICHG = Off & All Timers Reset & CHG = F ICHG or IPPC = Off & CHG_FLT = T, Timer = Paused. , ICHG or IPPC = On & CHG_FLT = F Timer = Resume. ICHG or IPPC = Off & All Timers = Reset & CHG_FLT = F & CHG = F & ALARM_INHIBITED = F & CHARGE_INHIBITED = F Notes and/or Actions (T = True, F = False) IPPC = On (Constant Current only) & TTIMEOUT = Started & CHG = T 2 3 4 5 6 7 8 9 10 PWM stopped. Timers remain running. PWM restarted. ICHG or IPPC = Off & All Timers = Reset & CHG_FLT = F & CHG = F ICHG or IPPC = Off. & All Timers = Reset & CHG = F & ALARM_INHIBITED = T (ALARM_INHIBITED bit is found in ChargeStatus()) Note: VCHG is active in all charge states except for nickel batteries which operate in constant current mode. 4110fa 17 LTC4110 OPERATION SMBUS WAKE-UP CHARGE STATE The battery will be charged with a fixed “wake-up” current regardless of previous ChargingCurrent() and ChargingVoltage() register values during wake-up charging. The current is identical to the preconditioning charge current which is programmed with an external resistor through the IPCC pin. The wake-up timer has the same period as tTIMEOUT , typically 175sec (see tTIMEOUT). The following conditions must be met to allow wake-up charge of the battery: • The SafetySignal must be RES_COLD, RES_IDEAL, or RES_UR. • AC must be present. This is qualified by DCDIV > VAC + VACH and DCIN above UVLO. • Wake-up charge initiates if a battery does not write non-zero values to ChargingCurrent() and CharginVoltage() registers when AC power is applied and a battery is present or when AC is present and a battery is subsequently connected. The following conditions will terminate the wake-up charge state and end charge attempts, unless otherwise noted. • The tTIMEOUT period is reached (see tTIMEOUT) when the SafetySignal is RES_COLD or RES_UR. The state machine will go to the SMBus OFF state. The CHG_FLT bit is not set. • The SafetySignal is registering RES_HOT. The state machine will go to the SMBus OFF state. • The SafetySignal is registering RES_OR. The state machine will go to the reset state. • The LTC4110 will leave the wake-up charge state and go into the SMBus preconditioning charge state if the ChargingCurrent() AND ChargingVoltage() registers have been written to non-zero values. • The AC power is no longer present (DCDIV < VAC or DCIN below UVLO). The state machine will go to the reset state. • The ALARM_INHIBITED becomes set in the ChargerStatus() register. The state machine will go to the SMBus OFF state. • CHARGE_INHIBIT is set in the BBuControl() register. Charge is stopped, however, the wake-up timer is not paused. Clearing CHARGE_INHIBIT will enable the LTC4110 to resume charging. • There is insufficient DCIN voltage to charge the battery as determined by the internal UVLO. This causes the state machine to enter the reset state and stop all charge activity. The LTC4110 will resume wake-up charging when there is sufficient DCIN voltage to charge the battery. • The CAL_START bit in the BBuControl() register is set. Charge is stopped and the LTC4110 enters the calibration state. • Writing a zero value to either the ChargingVoltage() or ChargingCurrent() register. The state machine will go to the SMBus OFF state. • RESET_TO_ZERO is set in the BBuControl() register. Charge is stopped; the SMBus OFF State is entered. SMBUS PRECONDITIONING CHARGE STATE During the SMBus preconditioning charge state, the charger will be operating in the preconditioning charge current limit. The following conditions must be met in order to allow SMBus preconditioning charge to start: • The ChargingVoltage() AND ChargingCurrent() registers must be written to non-zero values. The LTC4110 will not directly report the status of these registers. The battery needs only write one pair of ChargingVoltage() and ChargingCurrent() registers to stay in this state. The tTIMEOUT timer is not operational in SMBus preconditioning charge state. • The SafetySignal must be RES_COLD, RES_IDEAL, or RES_UR. • AC must be present and sufficient. This is qualified by DCDIV > VAC + VACH and DCIN > UVLO. The following conditions will affect the SMBus preconditioning charge state as specified below: • The SafetySignal is registering RES_HOT. Charge is stopped; the SMBus OFF state is entered. 4110fa 18 LTC4110 OPERATION • • • The SafetySignal is registering RES_OR. Charge is stopped. The LTC4110 enters the reset state. The AC power is no longer present (DCDIV < VAC or DCIN < UVLO). The LTC4110 enters the reset state. ALARM_INHIBITED is set in the ChargerStatus() register. Charge is stopped. The LTC4110 enters the SMBus OFF state. CHARGE_INHIBIT is set in the BBuControl() register. Charge is stopped, however, the T/4 timer is not paused. Clearing CHARGE_INHIBIT will enable the LTC4110 to resume charge. RESET_TO_ZERO is set in the BBuControl() register. Charge is stopped. The LTC4110 enters the SMBus OFF state. Writing a zero value to ChargeVoltage() or ChargeCurrent() register. Charge is stopped. The LTC4110 enters the SMBus OFF state. If the battery voltage exceeds the bulk charge threshold, the LTC4110 will enter the SMBus bulk charge state. If the T/4 timeout occurs, charge is stopped and the LTC4110 enters the SMBus OFF state. The CAL_START bit in the BBuControl() register is set. Charge is stopped and the LTC4110 enters the calibration mode. • The ChargeCurrent() AND ChargeVoltage() registers have not been written for tTIMEOUT. Charge is stopped and the LTC4110 enters the SMBus OFF state. • The SafetySignal is registering RES_OR. Charge is stopped and the LTC4110 enters the reset state. • The SafetySignal is registering RES_HOT. Charge is stopped and the LTC4110 enters the SMBus OFF state. • The AC power is no longer present (DCDIV < VAC or DCIN < UVLO). Charge is stopped and the LTC4110 enters the reset state. • ALARM_INHIBITED is set in the ChargerStatus() register. Charge is stopped and the LTC4110 enters the SMBus OFF state. • CHARGE_INHIBIT is set in the BBuControl() register. Charge is stopped. Clearing CHARGE_INHIBIT will enable the LTC4110 to resume charge. The tTIMEOUT timer does not pause when CHARGE_INHIBIT is set. • RESET_TO_ZERO is set in the BBuControl() register. The LTC4110 enters the SMBus OFF state. • Writing a zero value to the ChargeVoltage() or to the ChargeCurrent() register. Charge is stopped and the LTC4110 enters the SMBus OFF state. • The CAL_START bit in the BBuControl() register is set. Charge is stopped and the LTC4110 enters the calibration mode. SMBus OFF STATE This state is different from the reset state in that all charge is disallowed regardless of the value of the thermistor. The following conditions will affect the SMBus OFF state as specified below: • The ChargeCurrent() AND ChargeVoltage() registers have both been written to non-zero values, the battery thermistor is registering RES_COLD, RES_ IDEAL or RES_UR and CHARGE_INHIBT is clear. The LTC4110 enters the SMBus preconditioning charge state. • • • • • • SMBus BULK CHARGE STATE The charger will be operating in the bulk charge current limit during the SMBus bulk charge state. The following conditions must be met in order to allow SMBus bulk charge to start: • The ChargeVoltage() AND ChargeCurrent() registers must be written to non-zero values. The LTC4110 will not directly report the status of these registers. • The SafetySignal must be RES_COLD, RES_IDEAL, or RES_UR. • AC must be present and sufficient. This is qualified by DCDIV > VAC + VACH and DCIN > UVLO. The following conditions will affect the SMBus bulk charge state as specified below: 4110fa 19 LTC4110 OPERATION • The CAL_START bit in the BBuControl() register is set. The LTC4110 enters the calibration state. • The battery thermistor is registering RES_OR. The LTC4110 enters the reset state. LEAD ACID BATTERY CHARGE MODE The charger is programmed for lead acid batteries by connecting the TYPE pin to a voltage derived from the VREF pin resistor divider of nominally 0.5 • VREF . During charge, the LTC4110 operates as a high efficiency, synchronous, PWM flyback battery charger with constant current and constant float voltage regions of operation. The constantcharge current is programmed by the combination of a resistor (RCHG) from the ICHG pin to ground, a battery current sense resistor (RSNS) and CSP/CSN pin resistors. The float voltage is programmed to one of four values (4.7V, 7.05V, 11.75V, 14.1V) depending on the number of series cells (2, 3, 5 or 6) using the SELC pin and can be adjusted ±0.15V/cell with the VCHG pin. A new charge cycle begins with the charger in the bulk charge current limited state. In this state, the charger is a current source providing a constant charge rate and the CHGb (GPIO1 pin) is forced low. No time limits are placed upon lead acid battery charge. The charger monitors the battery voltage and as it reaches the float voltage the charger begins its float charge. While in float, the charge current diminishes as the battery accepts charge. Float voltage temperature compensation and temperature fault monitoring, if desired, are accomplished with an external thermistor network. Charge is active when the supply input is present as sensed by the DCDIV pin and DCIN above UVLO, thermistor temperature is ideal according to the thermistor monitor circuit (see SafetySignal Decoder) and the charge register bit CHARGE_INHIBIT is cleared. Soft-start ramps the charge current at a rate set by the capacitor on the ITH pin. When charge begins, the CHGb (GPIO1 pin) status output is forced to GND. At any time charge can be forced to stop by pulling the SHDN pin high or setting the CHARGE_INHIBIT bit high through the SMBus. If the battery voltage exceeds 107.5% (VBOV) of the programmed float voltage during any stage of charge, the charger pauses until the voltage drops below the hysteresis (VBOVH). No fault is indicated. An optional external NTC thermistor network can be used to provide an adjustable negative TC for the float voltage, monitor battery temperature and to detect battery presence. If the thermistor value indicates a hot temperature, voltage falling to VHOT on THB pin, charge current is halted, CHG_FLTb (GPIO3 pin) is forced low and the CHG_FLT bit will be set high. CHGb (GPIO1 pin) and CHG_STATE_0 and CHG_STATE_1 register bits will not be affected. When the thermistor value returns to ideal when the voltage exceeds VHOT +VHOTH on THB pin, charge resumes CHG_FLTb (GPIO3 pin) returns to high impedance and the CHG_FLT bit will be reset low. An open thermistor indicates an over-range which is considered absence of a battery. Low temperature is not monitored. However, since battery removal detection looks at the thermistor for a high resistance (VREM on THB pin), extremely cold temperatures may result in an indication of battery absence. To defeat the temperature monitoring register, replace the thermistor with a resistor to indicate normal battery temperature. When a thermistor is not used the resistor circuit must be routed through the battery connector if battery presence detection is required. BATTERY CALIBRATION MODE Figure 6 shows the LTC4110 in battery calibration mode and the corresponding PowerPath enabled. During calibration, the host CPU can calibrate a gas gauge or verify the battery’s ability to support a load by use of a low heat producing method. Calibration requires a host to communicate over a SMBus. In the low heat method, a synchronous PWM flyback charger is used in reverse to discharge the battery with a programmable constant-current into the system load thereby saving space and eliminating heat generation compared with resistive loads. Protection circuits prevent accidental overdrive back into the power source if the system load is insufficient. The constant-charge current is programmed by the combination of a resistor (RCAL) from the ICAL pin to ground, a battery current sense resistor (RSNS(BAT)) and CSP/CSN pin resistors. Calibration is initiated by setting the CAL_START bit in the BBuControl() register. The CAL_ON bit in the BBuStatus() register will 4110fa 20 LTC4110 OPERATION PWM STOPPED (BATTERY OVP) 7 ANY CHARGE STATE 5 STOP (OVERTEMPERATURE) 8 RESUME CHARGE STATE 6 RESET 4 ANY CHARGE STATE 2 9 1 CHARGE 3 STOP 4110 F05 Figure 5. SLA Charge State Diagram (Does Not Include Calibration) # 1 2 Or 3 Or Or 4 Or Or Or Or 5 6 7 8 9 Or Or Or Logic Event (T = True, F = False) [Notes] RES_OR = F & DCDIV pin = T & SHDN pin = F & CHARGE_INHIBITED = F & CHG_FLT = F VAR = T [AutoRestart] ChargingVoltage() & ChargingCurrent() ≠ 0 sent ChargingVoltage() or ChargingCurrent() = 0 sent RESET_TO_ZERO = T [See ChargeMode()] CHARGE_INHIBIT = T [See ChargeMode()] DCDIV pin = F RES_OR = T [Bat Removed, See ChargeStatus()] SHDN pin = T VUVD = T POR_RESET = T [See ChargeMode()] RES_HOT = T & RES_UR = F [See ChargeStatus()] RES_HOT = F [See ChargeStatus()] VBOV = T VBOV = F AlarmWarning() command is sent by Smart Battery over SMBus with any of the following bits set to True: OVER_CHARGED_ALARM TERMINATE_CHARGE_ALARM Reserved ALARM OVER_TEMPERATURE_ALARM Notes and/or Actions (T = True, F = False) ICHG = On & CHG = T ALARM_INHIBITED = F ICHG = Off & CHG = F ICHG = Off & CHG = F & CHARGE_INHIBITED = F & ALARM_INHIBITED = F ICHG = Off & CHG_FLT = T ICHG = On & CHG_FLT = F PWM stopped. Timers remain running. PWM restarted. ICHG = Off & CHG = F & ALARM_INHIBITED = T (ALARM_INHIBITED bit is found in ChargeStatus()) Note: For all charge states, VCHG is always active be set to indicate calibration in progress. Soft-start ramps the discharge current at a rate set by the capacitor on the ITH pin (typically 10ms with 0.1μF capacitor). A limit to how far the battery cell voltage will be discharged during calibration can be programmed with the VCAL pin (Li-Ion default = 2.75V/cell, lead acid default = 1.93V/cell, Smart NiMH/NiCd default = 0.95V/cell). When the limit is reached calibration is terminated, the CAL_COMPLETE bit in the BBuStatus() register is set, the CAL_ON bit in the BBuStatus() register will be cleared and the charge mode is automatically entered to begin recharging the battery. If the GPIO3 is configured as a calibration complete status output (CAL_COMPLETEb), it will be forced low until reset by the CAL_RESET write bit. Calibration is inhibited during backup or shutdown modes. Calibration is also inhibited when a thermistor is sensed absent. During calibration, user-programmable supply back-drive protections are provided. These protections prevent a reversal of current into the main supply and/or possibly raising the supply voltage to unsafe levels should the 4110fa 21 LTC4110 OPERATION system load not be adequate to absorb the current. The primary protection is accomplished with an external current sense resistor (RCL), connected between the CLP and CLN pins, through which the system load current flows. When the voltage across the resistor reaches 10mV (IBDT) or less, representing a low forward current, calibration mode is terminated. The current protection can be completely disabled by connecting both CLP and CLN pins to GND. As an alternative where RCL sensing is not an option for the application, a secondary method is accomplished by monitoring the supply voltage through the DCDIV pin. Once the DCDIV pin voltage goes above VOVP, calibration mode is terminated. In either case, the CAL_FLT register is set high and the charge mode is automatically entered to begin recharging the battery. Both of these protections are automatically disabled when not in calibration. However, in calibration, one or the other of these two protective methods should be used. You can optionally do both. Failure to implement any form of protection can result in destructive voltages being generated in the application. If the calibration cycle fails due to loss of the main power source a fault condition results that sets the CAL_FLT register bit and backup mode is entered. An optional external thermistor network is sampled at regular intervals to monitor battery temperature and to detect battery presence. If the thermistor value indicates a temperature outside of ideal limits (hot or over-range) the calibration current is halted and the CAL_FLT bit will be set high. When the thermistor value returns to an acceptable value (under-range, cold or ideal), charge mode is automatically entered to begin recharging the battery. Calibration can be restarted by clearing the CAL_FLT bit and sending another CAL_START command. An open thermistor (over-range) indicates absence of a battery. To defeat the temperature monitoring function, replace the thermistor with a resistor to indicate ideal battery temperature. When a thermistor is not used, the resistor circuit must be routed through the battery connector if battery presence detection is required. If the battery should be removed during calibration, calibration will terminate and the CAL_FLT read bit will be set high. SYSTEM LOAD BACKUP LOAD DCIN ON OFF OFF CURRENT FLOW BATTERY INID LTC4110 BATID CHGFET DCHFET 4110 F06 Figure 6. Calibration Mode Operation The CAL_FLT bit can be cleared by writing a one to the CAL_RESET or POR_RESET registers, or by forcing the SHDN pin high. The CAL_FLT bit is not cleared by removing and reapplying the supply input if the battery has maintained sufficient voltage (VBAT ≥ 2.7V). Calibration can start only if the CAL_FLT bit in the BBuStatus() register is clear. Once the LTC4110 is in calibration state, the following events will stop calibration: • BKDRV is sensed. The CAL_FLT bit is set. • A HOT thermistor is sensed. The CAL_FLT bit is set. • Loss of battery presence is sensed. The CAL_FLT bit is set. • The calibration cutoff threshold has been reached. The CAL_COMPLETE bit is set. The LTC4110 will start charging based upon the TYPE and SELA pins. • An OVER_TEMP_ALARM, RESERVED_ALARM, or TERMINATE_DISCHARGE_ALARM bit in the AlarmWarning() register is set. The CAL_FLT bit is set. The LTC4110 will start charging. • Loss of AC presence. The CAL_FLT bit is set. SHUTDOWN MODE The LTC4110 can be forced into either a micropower shutdown state or an all logic register reset state with the SHDN pin. 4110fa 22 LTC4110 OPERATION RESUME STATE 7 8 (CALIBRATION FAULT) RESET 1 ANY STATE 6, 9 4 (CALIBRATION COMPLETED) CALIBRATION RUNNING 3 CALIBRATION START 2 NO CALIBRATION MODE? YES 5 (BATTERY IS DEAD) 4110 F07 Figure 7. Calibration State Diagram # 1 2 3 4 5 6 Logic Event (T = True, F = False) [Notes] RES_OR = F & DCDIV pin = T & SHDN pin = F & CAL_FLT = F & CAL_START = T RES_OR = F & DCDIV pin = T & SHDN pin = F & CAL_FLT = F & CAL_START = T [Calibration Automatically Started] VBAT < VCAL [Battery has reached Discharge] VBAT < VCAL [Battery is Discharged] AlarmWarning() command is sent by Smart Battery over SMBus with any of the following bits set to True: OVER_TEMP_ALARM or Reserved ALARM or TERMINATED_DISCHARGE_ALARM] CAL_RESET = T Or Or Or 9 Or Or Or RES_HOT = T & RES_UR = F [See ChargeStatus()] RES_OR = T [Bat Removed, See ChargeStatus()] VOVP = T [Output Over-Voltage condition sensed)] IBDT = T [Output Back Drive Current condition sensed)] DCDIV pin = F SHDN pin = T VUVD = T POR_RESET = T [See ChargeMode()] Notes and/or Actions (T = True, F = False) CAL_COMPLETE = F (Calibration started while in Reset {Idle or Cold Power-Up}) ICHG or IPPC = Off & All Timers = Reset & CAL_COMPLETE = F (Calibration was initiated while in any mode other than Reset.) ICAL = ON & CAL_ON = T ICAL = Off & CAL_ON = F & CAL_COMPLETE = T (Normal Calibration Cycle) CAL_COMPLETE = T (Battery is already discharged. Cancel Calibration.) ICAL = Off & CAL_ON = F & ALARM_INHIBITED = T (ALARM_INHIBITED bit is found in ChargeStatus()) ICAL = Off & CAL_ON = F & CAL_COMPLETE = F & CAL_FLT = F ICAL = Off & CAL_ON = F & CAL_FLT = T 7 8 ICAL = Off & CAL_ON = F & ALARM_INHIBITED = F & CHARGE_INHIBITED = F REGISTER RESET STATE The SHDN pin will reset all logic registers when taken high, but only if DCIN is present as determined by DCDIV > VAC + VACH and DCIN above UVLO. Micropower shutdown state will not be entered, but the LTC4110 will be idle and not able to enter charge or calibration modes. If SHDN is switched low then normal operation will resume. While in register reset state, charge and calibration modes are inhibited, and all registers including the backup fault bit register are set to their default states and the internal timer is reset. The status pin ACPb is active, but GPIO1, GPIO2 and GPIO3 are reset to their default states. The SMBus is enabled, however, it is not able to communicate with the LTC4110. The DCIN to DCOUT PowerPath controller is functional and the VDD and VREF pin voltages remain. MICROPOWER SHUTDOWN STATE If the SHDN pin remains high when DCIN is removed as detected by the undervoltage lockout UVLO (see VUVD), micropower shutdown is entered, battery backup mode is inhibited and all registers are reset. During this condition, the level of the SHDN pin is ignored and has no effect. 4110fa 23 LTC4110 OPERATION The micropower shutdown state will be maintained if the DCIN supply is removed and sufficient battery voltage is present (VBAT ≥ 2.7V). When DCIN is reapplied as detected by the UVLO (see VUVI), regardless of the level of the SHDN pin, the shutdown state is automatically cancelled. Register reset state is cancelled until DCIN is reapplied as determined by the DCDIV pin. 5V IISD LTC4110 + RCSP1 + VSNS – RCSN1 RSNS(BAT) RCSN2 CSP RCSP2 + – CSN VICHG = RICHG/(RCSP1 + RCSP2)*VSNS INPUT CURRENT AMPLIFIER ICHG + – CURRENT LOOP EA RICHG BAT VFB + – + – VOLTAGE LOOP EA BANDGAP + + – REFERENCE VOLTAGE ADJUSTED BY VCHG PIN + – SHDN SHUTDOWN 4110 F08 4110 F09 ITH Figure 8. Shutdown Control Input + In shutdown; charge, calibration and backup modes are inhibited, all registers are set to their default states (with exception of the backup fault bit register), the internal timer is reset and oscillator disabled, the status pins; ACPb, GPIO1, GPIO2 and GPIO3 are a high impedance and the LTC4110 is put into a micropower state. While in shutdown the SMBus is disabled and the SDA and SCL pins are high impedance. In addition, the shutdown state will disconnect loads from the battery to prevent its discharge as follows: • The BATID pin is forced to the battery voltage to turn off the battery P-MOSFETs for isolation of the load from the battery • The CHGFET and DCHFET pins are forced to GND to turn off the flyback switcher N-MOSFETs • Current into the BAT pin is minimized. Also the VDD and VREF pin voltages will fall to zero. While in shutdown, the LTC4110 will draw a small current from battery (IBSD) if the DCIN supply is absent. If the SHDN pin is open an internal weak pull-up current (IISD) pulls the pin voltage up thereby entering the shutdown state. PWM OPERATION A conceptual diagram of the LTC4110 PWM engine is shown in Figure 9. Figure 9. LTC4110 PWM Engine The voltage across the external current programming resistor RSNS(BAT) is averaged by the RC network connected to the CSP and CSN pins and then amplified by a ratio of RICHG/(RCSP1 + RCSP2). This amplified voltage is compared with the bandgap reference through the current loop error amplifier to adjust the ITH pin which sets the current comparator threshold to maintain a constant charging current. Once the battery voltage rises to close to the programmed float voltage, the voltage loop error amplifier gradually pulls the ITH pin low, reduces the charging current and maintain a constant voltage charging. C/x CHARGE TERMINATION LTC4110 monitors the charging current through the voltage on the ICHG pin, once the current drops below 20% of the bulk charging current, an internal C/x comparator is tripped, and the LTC4110 will enter top-off charge stage if standard Li-Ion battery mode is selected or release the GPI01 pin if no-host SLA battery mode is selected. The actual x value depends on the programmed charging current and the C rate of the battery. x= C ICHG •5 4110fa 24 LTC4110 OPERATION Where: C = C rate of the battery ICHG = Programmed charging current For Example, if we charge a 3Ah battery with 1A current, then x = 15. SAFETYSIGNAL DECODER Table 3. SafetySignal State Ranges (Except SLA) SafetySignal CHARGE RESISTANCE 0Ω to 500Ω 500Ω to 3k 3kΩ to 30k 30k to 100k Above 100k CSS RSafetySignal LATCH RTHB 54.9k THB RTHA 1.13k THA MUX VINT THA_SELB + – HI_REF TH_HI VINT REF LO_REF SafetySignal CONTROL RES_OR RES_COLD RES_HOT RES_UR + – TH_LO THB_SELB CHARGE STATUS BITS RES_UR, RES_HOT, BATTERY_PRESENT RES_HOT, BATTERY_PRESENT BATTERY_PRESENT RES_COLD, BATTERY_PRESENT RES_OR, RES_COLD DESCRIPTION Under range Hot Ideal Cold Overrange 4110 F10 Figure 10. Battery Safety Decoder (Except SLA) Note: The under range detection scheme is a very important feature of the LTC4110. The RTHA/RSafetySignal divider trip point of 0.307 • 4.75V = 1.46V is well above the 0.047 • VDD = 140mV threshold of a system using a 10k pull-up. A system using a 10k pull-up would not be able to resolve the important under range to a hot transition point with a modest 100mV of ground offset between battery and SafetySignal detection circuitry. Such offsets are anticipated when charging at normal current levels. Table 4. SafetySignal for SLA (7.256k Between THA and THB) SafetySignal CHARGE RESISTANCE 0Ω to 3.1k 3.1k to 114k 114k CHARGE STATUS BITS RES_HOT, BATTERY_PRESENT BATTERY_PRESENT RES_COLD, RES_OR DESCRIPTION Hot Ideal Battery Removal then RES_C0LD ≥ RES_IDEAL threshold, RES_IDEAL ≥ RES_HOT threshold, and finally the RES_HOT ≥ RES_UR threshold. Once the SafetySignal range is determined, the lower value thresholds are not sampled. The SafetySignal decoder block uses the previously determined SafetySignal value to provide the appropriate adjustment in threshold to add hysteresis. The RTHB resistor value is used to measure the RES_OR ≥ RES_COLD and RES_COLD ≥ RES_IDEAL thresholds by connecting the THB pin to an internal voltage and measuring the voltage resultant on the THA pin. The RTHA resistor value is used to measure the RES_IDEAL ≥ RES_HOT and RES_HOT ≥ RES_UR thresholds by connecting the THA pin to the internal voltage and measuring the resultant voltage on the THB pin. The SafetySignal impedance is interpreted according to Table 3. When the DCIN supply is present, a full sampling of the SafetySignal is performed every 27ms. When the supply is absent, a low power limited sampling of the SafetySignal is performed every 218ms. A full sampling of the thermistor state is performed only if a change of battery presence is detected when the supply is not present. GPIO AND STATUS FUNCTIONS All of the GPIO pins are open drain with N-MOSFET drivers capable of sinking current sufficient to drive an LED (see VOL). The pins are not capable of sourcing any current and instead enter a Hi-Z mode when the output is not low. An external pull-up will be required to create any high output logic state. 4110fa This decoder measures the resistance of the SafetySignal and features high noise immunity at critical trip points. The SafetySignal decoder is shown in Figure 10. The value of RTHA is 1.13k and RTHB is 54.9k. SafetySignal sensing is accomplished by a state machine that reconfigures the switches of Figure 10 using THA_SELB and THB_SELB, a selectable reference generator, and two comparators. The state machine successively samples the SafetySignal value starting with the RES_OR ≥ RES_COLD threshold, 25 LTC4110 OPERATION The three I/O outputs, GPIO1, GPIO2 and GPIO3 are digital I/O pins with two modes of operation. 1) General Purpose I/O 2) Status Reporting A host can set the mode of each I/O pin with each I/O pin’s setting independent of the others such that any combination of status reporting or bit I/O can be implemented. Only a UVLO or a SHDN event will change the GPIO_n_EN bits back to default values. If you enable a GPIO pin to report status output, it overrides the GPIO_n_OUT setting. In addition, the LTC4110 supports a special power up mode of status reporting on all 3 IO pins for standalone applications where it is assumed “no host” exists. This power up status mode is enabled if the SELA pin is set to 0.5 • VREF voltage as developed from VREF pin resistor divider. This mode does not actually disable the SMBus in any way and if a host does exist in this power up mode, the host can reprogram the I/O settings at any time. All GPIO pins operate as digital inputs at all times regardless of the pin settings with pin state reported on the GPIO_n_IN bits in the BBuStatus() register. However to actually read digital input data from an external device, you must disable the GPIO_n_EN bit. Otherwise the input will simply reflect the output state assuming external powered pull-ups exist. Table 5a. GPIO1 Modes HOST PROGRAMMED BIT SETTINGS GPIO_1_EN 0 1 1 1 GPIO_1_OUT 0 X 0 1 GPIO_1_CHG 0 1 0 0 Digital Input Status Output Digital Output Digital Output Input Data CHGb 0 1 GPIO_1_IN With Pull-Up With Pull-Up With Pull-Up GPIO_1 MODE DATA NOTE There are a total of 5 status signals possible. CHGb, C/xb, BKUP-FLTb, CHG_FLTb, and CAL_COMPLETEb. Each of these signals is asserted low on the output when they are true. CHGb is an asserted low signal when either CHG_STATE_0 or CHG_STATE_1 is set to one. C/xb is asserted low signal when C/x state in the charge cycle is reached. This status signal is only available if the TYPE pin is set to SLA mode and replaces the CHGb status output. BKUP_FLTb is asserted low when the BKUP_FLT bit is set to one in the BBuStatus() register. BKUP_FLT is a sticky bit that is designed to be cleared primarily through the setting of the BUFLT_RST bit in the BBuControl() register. The value of this bit does not inhibit charging or calibration functions. CHG_FLTb is asserted low when the CHG_FLT bit is set to one in the BBuStatus() register. CAL_COMPLETEb bit is asserted low when the conditions of successful calibration cycle are met. CAL_COMPLETEb status output can be used as an interrupt to a host for the purpose of help implementing a simple gas gauge function or capacity verification function with a standard battery. However, if the LTC4110 is set up in no host mode, CAL_COMPLETEb as a status signal is not considered usable since it is assumed there is no host to enable calibration mode. Therefore the CHG_FLTb signal is substituted for CAL_COMPLETEb as the status output signal. Table 5 describes the specific modes and status signal options of each GPIO pin. Table 5b. GPIO1 Power Up Mode (SELA = 0.5 • VREF) FORCED BIT SETTINGS GPIO_1_EN 1 1 GPIO_1_OUT X X GPIO_1_CHG 1 1 0 1 Status Output Status Output CHGb C/xb With Pull-Up With Pull-Up TYPE = SLA GPIO_1 MODE DATA NOTE 4110fa 26 LTC4110 OPERATION Table 5c. GPIO2 Modes HOST PROGRAMMED BIT SETTINGS GPIO_2_EN 0 1 1 1 GPIO_2_OUT 0 X 0 1 GPIO_2_BUFLT 0 1 0 0 Digital Input Status Output Digital Output Digital Output Input Data BKUP_FLTb 0 1 GPIO_2_IN With Pull-Up With Pull-Up With Pull-Up GPIO_2 MODE DATA NOTE Table 5d. GPIO2 Power Up Mode (SELA = 0.5 • VREF) FORCED BIT SETTINGS GPIO_2_EN 1 GPIO_2_OUT X GPIO_2_ BUFLT 1 Status Output BKUP_FLTb With Pull-Up GPIO_2 MODE DATA NOTE Table 5e. GPIO3 Modes HOST PROGRAMMED BIT SETTINGS GPIO_3_EN 0 1 1 1 GPIO_3_OUT 0 X 0 1 GPIO_3_CAL 0 1 0 0 Digital Input Status Output Digital Output Digital Output Input Data CAL_COMPLETEb 0 1 GPIO_3_IN With Pull-Up With Pull-Up With Pull-Up GPIO_3 MODE DATA NOTE Table 5f. GPIO3 Power Up Mode (SELA = 0.5 • VREF) FORCED BIT SETTINGS GPIO_3_EN 1 GPIO_3_OUT X GPIO_3_ CAL 1 Status Output CHG_FLTb With Pull-Up GPIO_3 MODE DATA NOTE SMBUS INTERFACE All communications over the SMBus are interpreted by the SMBus interface block. The SMBus interface is a SMBus slave device. All internal LTC4110 registers may be updated and accessed through the SMBus interface as required. The SMBus protocol is a derivative of the I2C-BusTM. (For a complete description of the bus protocol requirements, reference “The I2C-Bus and How to Use It, V1.0” by Philips®, and “System Management Bus Specification, Version 1.1,” from the SMBus organization). See Table 6: Register Command Set Description and Table 7: Summary of Supported SMBus Functions, for complete details. All data is clocked into the shift register on the rising edge of SCL. All data is clocked out of the shift register on the falling edge of SCL. Detection of an SMBus Stop condition, or power-on reset will reset the SMBus interface to an initial state at any time. The LTC4110 command set is interpreted by the SMBus interface and passed onto the charger controller block as control signals or updates to internal registers. Smart battery charge commands are 4110fa 27 LTC4110 OPERATION processed to allow compliance with smart battery charge and discharge termination and protection control. However, there is no actual value processing of the voltage or current charge commands. IC will acknowledge all smart battery write commands, but process only a subset of them. Full SMBus error and reset handling is supported. The SMBus remains functional during backup mode, but not in SHDN mode. The LTC4110 SMBus address can be changed when standard batteries are used to facilitate redundant backup systems. Connect SELA pin to GND for 12h, VDD for 28h and VREF for 20h. When a smart battery is selected by the TYPE pin the SELA pin must be connected to GND to select address 12h. Note: Although there are only 7 address bits for SMBus, the above addresses shown follow the smart battery convention of including the Read/Write bit as part of the address value. The Read/Write bit becomes the LSB of the SMBus address with the Read/Write bit value assumed to be a 0 value. If multiple LTC4110s with smart batteries are to be used, each LTC4110 must be SMBus isolated from all other LTC4110s so the main bus or host bus can only see one LTC4110 and its corresponding smart battery at a time. Failure to do so will cause multiple LTC4110s and smart batteries responding to a single host query resulting in errors. There are multiple channel SMBus multiplexer ICs such as the LTC4305 and LTC4306 to help implement the required isolation. Furthermore, if a given SMBus is high in SMBus device count or long in length, you may want to consider using SMBus accelerators. The above ICs listed support that option. If the SMBus is not used or to force all GPIOs to status mode upon power-up, connect SELA to a typically 0.5 • VREF voltage from VREF pin resistor divider. The SMBus address then, if used, will be 12h. Pull-ups are required on the SDA and SCL pin such that when they are not being used, they are in a default high state that means no bus activity. The pull-up voltage need only be high enough to satisfy the logic high threshold. Tying the pins low is a valid state on the SMBus that means anything but the bus is free. This state will force the LTC4110’s internal SMBus state machine to reset itself because it thinks the SMBus is hung. The LTC4110 does not support or respond to the following SMBus V1.1 timing specifications: a) TTIMEOUT (This is not to be confused with the LTC4110’s tTIMEOUT specification.) b) TLOW:SEXT c) TLOW:MEXT The above specifications have to do with detecting bus hangs or SMBus devices that are taking too long to reply using clock stretching and slowing down the SMBus bandwidth. The LTC4110 is a slave only device that does not do any clock stretching and works all the way up to maximum 100kHz bus speed. It will not hang the bus. The design will always reset its SMBus interface upon receiving an SMBus Start Bit or a Stop Bit regardless of the prior state of the bus. 4110fa 28 LTC4110 OPERATION Table 6. Register Command Set Descriptions (XxxxXxxx() – Register Byte, XXXXXXXX – Status Bit) LABEL AC_PRESENT BATTERY_PRESENT DESCRIPTION Set to 1 when sufficient input voltage (DCDIV > VAC + VACH and DCIN above UVLO) available and switches load from battery to main supply. Zero indicates backup mode engaged. BATTERY_PRESENT is set if a battery is present, otherwise it is cleared. The LTC4110 uses the SafetySignal to determine battery presence. If the LTC4110 detects a RES_OR condition, the BATTERY_PRESENT bit is cleared immediately. The LTC4110 will not set the BATTERY_PRESENT bit until it successfully samples the SafetySignal twice and does not detect a RES_OR condition on either sampling. If AC is not present (DCDIV < VAC or DCIN below UVLO), this bit may not be set for up to one-half second after the battery is connected to the SafetySignal. The ChargingCurrent() and ChargingVoltage() register values are immediately cleared whenever this bit is cleared. Charging will never be allowed if this bit is cleared. ALARM_INHIBITED bit is set if a valid AlarmWarning() message has been received and charging is inhibited as a result. This bit is cleared if POR_RESET is set, both ChargingVoltage() and ChargingCurrent() are rewritten to the LTC4110, the power is removed (DCDIV < VAC or DCIN below UVLO), the SHDN pin is set high, or if a battery is removed. Set to 1 when NTC pin is below 500Ω typical. This bit is never set when TYPE pin selects SLA battery.. The RES_HOT bit is set only when the SafetySignal resistance is less than 3kΩ (3.1kΩ for SLA) typical, which indicates a hot battery. The RES_HOT bit will be set whenever the RES_UR bit is set. The RES_COLD bit is set only when the SafetySignal resistance value is greater than 30kΩ typical. The SafetySignal indicates a cold battery. The RES_COLD bit will be set whenever the RES_OR bit is set. This bit is the same as RES_OR for SLA. The RES_OR bit is set when the SafetySignal resistance value is above 100kΩ (114kΩ for SLA) typical. The SafetySiganl indicates an open circuit. The LTC4110 always reports itself as a Level 2 Smart Battery Charger. Indicates charge inhibited is enabled when set to a one. This is a duplicate of the CHARGE_INHIBIT bit in the BBuStatus() register. LTC4110 only monitors for zero or non-zero values. A value of zero will stop the charger. A non-zero value here, and for ChargingVoltage(), will restart the charger. LTC4110 only monitors for zero or non-zero values. A value of zero will stop the charger. A non-zero value here, and for ChargingCurrent(), will restart the charger. ChargerStatus() – Read Only. The SMBus host uses this command to read the LTC4110’s charge status bits. ALARM_INHIBITED RES_UR RES_HOT RES_COLD RES_OR LEVEL:3/LEVEL:2 CHARGE_INHIBITED ChargingCurrent() – Write Only. The battery, system host or other master device sends the desired charging current to the LTC4110. ChargingCurrent() ChargingVoltage() – Write Only. The Battery, System Host or other master device sends the desired charging voltage to the LTC4110. ChargingVoltage() AlarmWarning() – Write Only. The Smart Battery, acting as a bus master device, sends the AlarmWarning() message to the LTC4110 to notify it that one or more alarm conditions exist. Alarm indications are encoded as bit fields in the battery’s status register, which is then sent to the LTC4110 by this function. Only the OVER_CHARGED_ALARM, TERMINATE_CHARGE_ALARM,RESERVED_ALARM, OVER_TEMP_ALARM and TERMINATE_DISCHARGE_ALARM bits are supported by the LTC4110. The ALARM_INHIBITED bit in the ChargerStatus() register indicates whether a charging process or a calibration process was halted by a write to this register. OVER_CHARGED_ALARM TERMINATE_CHARGE_ALARM RESERVED_ALARM Set to one indicates battery has been overcharged and stops charge. Setting this bit will only stop a charging process (default = zero). Set to one indicates battery requesting charge termination. Setting this bit will only stop a charging process (default = zero). Set to one for reserved alarm condition. Setting this bit will stop both a calibration process and a charging process (default = zero). 4110fa 29 LTC4110 OPERATION LABEL OVER_TEMP_ALARM DESCRIPTION Set to one indicates battery is temperature is out of range. Setting this bit will stop both a calibration process and a charging process (default = zero). TERMINATE_DISCHARGE_ALARM Set to one indicates battery requesting discharge termination. Smart battery only. Setting this bit will only stop a calibration process (default = zero). BBuStatus() – Read Only. The SMBus host uses this command to read the LTC4110’s status bits. CAL_ON CAL_COMPLETE BKUP_ON GPIO_1_IN GPIO_2_IN GPIO_3_IN CHG_FLT BKUP_FLT Set to one indicates calibration in progress to discharge the battery. Set to one indicates calibration process is complete. Can be used as a battery capacity indicator. Bit is cleared by CAL_RESET. This bit is available as a status signal output on the GPIO3 pin. Set to one verifies backup mode is active Shows logic state of general purpose I/O Pin #1. This is always enabled. Shows logic state of general purpose I/O Pin #2. This is always enabled. Shows logic state of general purpose I/O Pin #3. This is always enabled. Set to one indicates battery charge fault. Set to one indicates battery cell voltage < VDIS . This bit state is retained as long as sufficient VBAT is applied. This bit is available as a status signal output on the GPIO2 port. This bit remains until either the SHDN pin is cycled or register bits POR_RESET or BUFLT_RST are set when DCOUT returns. Set to one indicates a calibration fault. Calibration terminated early. Combined with CHG_STATE_1 indicates phase of charging. 00 = Off, 01 = precharge, 10 = bulk charge, 11 = top off charge See CHG_STATE_0 Indicates charge inhibited is enabled when set to a one. This as a duplicate of CHARGE_INHIBIT bit in the ChargerStatus() register. Set to one starts a discharge based calibration of battery (default = self cleared to zero-off) Set to one clears the CAL_FLT as well as the CAL COMPLETE and CAL_ON status bits. If calibration is in progress, it will also stop the calibration process (default = self cleared to zero-off) Set to one enables GPIO1 pin as an output (default = set to one if programming SMBus not used by connecting SELA pin to 0.5VREF, otherwise default = set to zero/GPIO1 high-Z ) Set to one enables GPIO2 pin as an output (default = set to one if programming SMBus not used by connecting SELA pin to 0.5VREF, otherwise default = set to zero/ GPIO2 high-Z) Set to one enables GPIO3 pin as an output (default = set to one if programming SMBus not used by connecting SELA pin to 0.5VREF, otherwise default = set to zero/ GPIO3 high-Z) Programmable logic bit whose state will be reflected on the GPIO1 pin if the GPIO_1_CHG bit is cleared (default = set to zero/GPIO1 pulled low) Programmable logic bit whose state will be reflected on the GPIO2 pin if the GPIO_2_BUFLT bit is cleared (default = set to zero/GPIO2 pulled low). Programmable logic bit whose state will be reflected on the GPIO3 pin if the GPIO_3_CALCOM bit is cleared (default = set to zero/GPIO3 pulled low) CAL_FLT CHG_STATE_0 CHG_STATE_1 CHARGE_INHIBITED BBuControl() – Write Only. The SMBus host uses this command to control the LTC4110. CAL_START CAL_RESET GPIO_1_EN GPIO_2_EN GPIO_3_EN GPIO_1_OUT GPIO_2_OUT GPIO_3_OUT 4110fa 30 LTC4110 OPERATION LABEL GPIO_1_CHG DESCRIPTION Set to one sends an inverted CHG_ON (internal register, set to 1 when either CHG_STATE_0 or CHG_STATE_1 is set to 1) status signal out to the GPIO1 pin. If this bit is set, the value of CHG_ON overrides the value of the GPIO_1_ OUT bit state. Pin must be output enabled with GPIO_1_EN bit (default = set to zero/off) Set to one sends an inverted BKUP_FLT status signal out to the GPIO2 pin. If this bit is set, the value of BKUP_FLT overrides the value of the GPIO_2_OUT bit state. Pin must be output enabled with GPIO_2_EN bit (default = set to zero/off) Set to one sends an inverted CAL_COMPLETE signal out to the GPIO3 pin. If this bit is set, the value of CAL_ COMPLETE overrides the value of the GPIO_3_OUT bit state. Pin must be output enabled with GPIO_3_EN bit (default = set to zero/off) Set to one resets all faults and timers in charge and forces the ChargingCurrent() and ChargingVoltage() to zero values. Clears Alarm_Warning() register. Does not affect BBuControl() register. Bit clears to zero automatically after the command is executed (default = cleared to zero-no reset) Resets LTC4110 to power-on default values. Setting the bit to a one will activate POR_RESET. POR_RESET performs a total chip wide reset like the SHDN pin function without the chip actually shutting down. This includes clearing any bits in registers. The bit clears itself automatically after the command is executed (default = cleared/no reset) Resets the BKUP_FLT bit. The bit clears itself automatically after the command is executed (default = cleared). Disables charging of battery. Set to one halts charge current while holding the charger state and pausing all battery charge timers without changing the ChargingCurrent() and ChargingVoltage() values. Charge may be enabled by clearing this bit. This bit is automatically cleared when power is reapplied or when a battery is re-inserted (default = cleared to zero-off) GPIO_2_BUFLT GPIO_3_CALCOM RESET_TO_ZERO POR_RESET BUFLT_RST CHARGE_INHIBIT 4110fa 31 LTC4110 OPERATION Table 7. Summary of Supported SMBus Functions Function ChargerStatus( ) Access SMBus Address 7’b0001_ 001 Command Code 8'h13 Data Type Status AC_PRESENT D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 POLLING_ENABLED 0 ERROR 0 0 0 0 CHARGE_INHIBITED 1/0 4110fa D0 CHARGE_INHIBITED 1/0 CHARGE_INHIBIT CURRENT_NOTREG 1 0 0 FULLY_DISCHARGED CHG_STATE_0 BATTERY_PRESENT ALARM_INHIBITED Read ChargingCurrent( ) Write ChargingVoltage( ) Write AlarmWarning( ) 7’b0001_ 001 8'h16 7’b0001_ 001 8'h15 7’b0001_ 001 8'h14 Return Value Value Permitted Values Value Permitted Values Control 1/0 1/0 0 1/0 1/0 1/0 1/0 1/0 Note 1 0 0 0 0 Unsigned Integer Representing Current in mA Note 2 Unsigned Integer Representing Voltage in mV TERMINATE_DISCHARGE_ALARM REMAINING_CAPACITY_ALARM TERMINATE_CHARGE_ALARM REMAINING_TIME_ALRAM OVER_CHARGED_ALARM OVER_TEMP_ALARM RESERVED_ALARM Write BBuStatus( ) 7’b0001_ 001 8'h3D Permitted Values Status 1/0 1/0 1/0 1/0 1/0 0 0 0 0 0 0 CAL_COMPLETE FULLY_CHARGED DISCHARGING INITIALIZED RESERVED CHG_STATE_1 POR_RESET GPIO_1_IN GPIO_2_IN GPIO_3_IN BKUP_FLT BKUP_ON CAL__ON Reserved Reserved Reserved VOLTAGE_NOTRES LEVEL:3/LEVEL:2 CURRENT_OR VOLTAGE_OR POWER_FAIL RES_COLD RES_HOT RES_UR RES_OR Read BBuControl() [ChargerMode()] 7’b0001_ 001 8'h12 Return Values Control 1/0 1/0 1/0 0 0 1/0 1/0 1/0 1 1/0 1/0 1/0 1/0 1/0 GPIO_3_CALCOM RESET_TO_ZERO GPIO_2_BUFLT GPIO_1_CHG GPIO_1_OUT GPIO_2_OUT GPIO_3_OUT CAL_RESET CAL_START GPIO_1_EN GPIO_2_EN GPIO_3_EN Write Permitted Values 1/0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 0 1/0 1/0 1/0 1/0 1/0 1/0 1/0 Note 1: IC only looks for a zero (off) or a non-zero (on) value. Actual charge current is set by the ICHG pin. Note 2: IC only looks for a zero (off)or a non-zero (on) value. Actual charge voltage is set by the VCHG pin. 32 BUFLT_RST Reserved Reserved 0 CHG_FLT CAL_FLT LTC4110 APPLICATIONS INFORMATION The first configuration option to set for the LTC4110 is the type and cell count of the battery you wish to use. Pins TYPE and SELC are use to set this configuration. Please note NiMH and NiCd batteries are only supported in the smart battery configuration. The three state input pins SELA, SELC and TYPE should NOT be changed while power is applied to the IC unless in shutdown mode. Such action will result in unpredictable behavior from the LTC4110. SUPERCAPS Table 8 shows all of the options with the exception of SuperCaps. SuperCaps are supported by using standard Li-ion or SLA modes in combination with the adjusting the charge voltage with the VCHG pin. As far as the LTC4110 is concerned, it is still working with a Li-ion or SLA battery and will follow all the charge states as required for that chemistry. Table 9 shows the required configuration based on the desired cap voltage and series cell count. Other per cell voltages can be obtained by adjusting the VCHG pin as required. When the LTC4110 is configured to charge a super cap, if TYPE pin is tied to 0.5VREF, use the bulk charge current equation (see the Programming Charging/Calibration Current section for details) to set the charging current. If TYPE pin is tied to GND, then the charging current will equal to preconditioning charge current when the cap voltage is below the bulk charge threshold (as listed in Table 9) and bulk charge current when the voltage is above the threshold. Simply tie the IPCC pin to ICHG pin if these two currents need to be the same. If the capacitor is too small (