LTC4010_15 LINER
Document overview
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Technical content
DescripTion
High Efficiency Standalone Nickel Battery Charger The L TC®4010 provides a complete, cost-effective nickel battery fast charge solution in a small package using few external components. A 550kHz PWM current source controller and all necessary charge initiation, monitoring and termination control circuitry are included. The L TC4010 automatically senses the presence of a DC adapter and battery insertion or removal. When an external DC source is not present, the L TC4010 enters shutdown and supply current drawn from an installed battery drops to the lowest possible level. Heavily discharged batteries are precharged with a trickle current. The L TC4010 can simultaneously use both –∆V and ∆T/∆t fast charge ter- mination techniques and can detect various battery faults. If necessary, a top-off charge is automatically applied to NiMH batteries after fast charging is completed. The IC will also resume charging if the battery self-discharges after a full charge cycle. All L TC4010 charging operations are qualified by actual charge time and maximum average cell voltage. Charging may also be gated by minimum and maximum temperature limits. NiMH or NiCd fast charge termination parameters are pin selectable. L, L T , L TC, L TM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 2A NiMH Battery Charger
FeaTures
applicaTions
n Integrated or Standalone Battery Charger n Portable Instruments or Consumer Products n Battery-Powered Diagnostics and Control n Back-Up Battery Management n Complete NiMH/NiCd Charger for 1 to 16 Cells n No Microcontroller or Firmware Required n 550kHz PWM Current Source Controller n No Audible Noise with Ceramic Capacitors n Wide Input Voltage Range: 5.5V to 34V n Programmable Charge Current: 5% Accuracy n Automatic T rickle Precharge n –∆V Fast Charge Termination n Optional ∆T/∆t Fast Charge Termination n Optional Temperature Qualification n Automatic NiMH Top-Off Charge n Programmable Timer n Automatic Recharge n Multiple Status Outputs n Micropower Shutdown n 16-Lead Thermally Enhanced TSSOP Package 2A NiMH Charge Cycle at 1C FAULT CHRG READY V CC TGATE VCDIV VCELL VTEMP L TC4010 TIMER INTVDD GND CHEM SENSE BAT FROM ADAPTER 47µH TO SYSTEM LOAD 0.05/uni03A9 2-CELL NiMH PACK WITH 10k NTC
4010 TA01a
49.9k 10k 10k 0.1µF 68nF 10µF 33nF 10µF BGATE PGND TIME (MINUTES)
1.25 SINGLE CELL VOL TAGE (V)
BATTERY TEMPERATURE (°C) 1.30 1.40 1.45 1.50 1.60
4010 TA01b
1.35 1.55 40 10020 60 80 SINGLE CELL VOL TAGE CHARGE CURRRENT BATTERY TEMPERATURE TOP OFF
FAULT, CHRG, VCELL, VCDIV, SENSE, Operating Ambient Temperature Range (Note 1)
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC Supply VCC Input Voltage Range l 4.5 34 V ISHDN Shutdown Quiescent Current (Note 8) V CC = BAT = 4.8V 5 10 µA IQ Quiescent Current Waiting to Charge (Pause) l 3 5 mA ICC Operating Current Fast Charge State, No Gate Load l 5 9 mA VUVLO Undervoltage Threshold Voltage V CC Increasing l 3.85 4.2 4.45 V VUV(HYST) Undervoltage Hysteresis Voltage 170 mV VSHDNI Shutdown Threshold Voltage VCC – BAT , VCC Increasing l 45 65 90 mV VSHDND Shutdown Threshold Voltage VCC – BAT , VCC Decreasing l 15 35 60 mV VCE Charge Enable Threshold Voltage V CC – BAT , VCC Increasing l 400 510 600 mV INTVDD Regulator VDD Output Voltage No Load l 4.5 5 5.5 V IDD Short-Circuit Current (Note 5) INTVDD = 0V l –100 –50 –10 mA INTVDD(MIN) Output Voltage VCC = 4.5V , IDD = –10mA l 3.85 V (Note 4) The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V , BAT = 4.8V , GND = PGND = 0V , unless otherwise noted. pin conFiguraTion FE PACKAGE 16-LEAD PLASTIC TSSOP TOP VIEW FAULT CHRG CHEM GND V TEMP VCELL VCDIV TIMER READY V CC TGATE PGND BGATE INTV DD BAT SENSE TJMAX = 125°C, qJA = 38°C/W EXPOSED PAD (PIN 17) IS GND. MUST BE SOLDERED TO PCB TO OBTAIN SPECIFIED THERMAL RESISTANCE orDer inForMaTion LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L TC4010CFE#PBF L TC4010CFE#TRPBF 4010CFE 16-Lead Plastic TSSOP 0°C to 85°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE L TC4010CFE L TC4010CFE#TR 4010CFE 16-Lead Plastic TSSOP 0°C to 85°C Consult L TC 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/
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS PWM Current Source VFS BAT – SENSE Full-Scale Regulation Voltage (Fast Charge) 0.3V < BAT < VCC – 0.3V (Note 8) BAT = 4.8V l 100 100 105 105 mV mV V PC BAT – SENSE Precharge Regulation Voltage 0.3V < BAT < V CC – 0.3V (Note 8) BAT = 4.8V l mV mV V TC BAT – SENSE Top-Off Charge Regulation Voltage 0.3V < BAT < V CC – 0.3V (Note 8) BAT = 4.8V l 6.5 6.5 13.5 13.5 mV mV LI BAT – SENSE Line Regulation 5.5V < VCC < 25V , Fast Charge ±0.3 mV IBAT BAT Input Bias Current 0.3V < BAT < VCC – 0.1V –2 2 mA ISENSE SENSE Input Bias Current SENSE = BAT 50 150 µA IOFF Input Bias Current, (VCELL = 0V) SENSE BAT l l µA µA f TYP Typical Switching Frequency l 460 550 640 kHz fMIN Minimum Switching Frequency l 20 30 kHz DCMAX Maximum Duty Cycle 98 99 % VOL(TG) TGATE Output Voltage Low CC – TGATE) (Note 6) VCC > 9V , No Load VCC < 7V , No Load l l VCC – 0.5 5.6 VCC 8.75 V V VOH(TG) TGATE Output Voltage High VCC – TGATE, No Load l 0 50 mV tR(TG) TGATE Rise Time CLOAD = 3nF , 10% to 90% 35 100 ns tF(TG) TGATE Fall Time CLOAD = 3nF , 10% to 90% 45 100 ns VOL(BG) BGATE Output Voltage Low No Load l 0 50 mV VOH(BG) BGATE Output Voltage High No Load l INTVDD – 0.075 INTVDD V tR(BG) BGATE Rise Time CLOAD = 1.6nF , 10% to 90% 30 80 ns tF(BG) BGATE Fall Time CLOAD = 1.6nF , 10% to 90% 15 80 ns ADC Inputs ILEAK Analog Channel Leakage 0V < VCELL < 2V ±100 nA Charger Thresholds V BP Battery Present Threshold Voltage l 320 350 370 mV VBOV Battery Overvoltage l 1.815 1.95 2.085 V VMFC Minimum Fast Charge Voltage l 850 900 950 mV VFCBF Fast Charge Battery Fault Voltage l 1.17 1.22 1.27 V ∆VTERM –∆V Termination CHEM OPEN (NiCd) CHEM = 0V (NiMH) l l mV mV V AR Automatic Recharge Voltage VCELL Decreasing l 1.260 1.325 1.390 V ∆TTERM ∆T Termination (Note 7) CHEM = 3.3V (NiCd) CHEM = 0V (NiMH) l l 1.3 0.5 2.7 1.5 °C/min °C/min T MIN Minimum Charging Temperature (Note 7) V TEMP Increasing l 0 5 9 °C TMAXI Maximum Charge Initiation Temperature (Note 7) V TEMP Decreasing, Not Charging l 41.5 45 47 °C TMAXC Maximum Charging Temperature (Note 7) V TEMP Decreasing, Charging l 57 60 63 °C VTEMP(D) VTEMP Disable Threshold Voltage l 2.8 3.3 V VTEMP(P) Pause Threshold Voltage l 130 280 mV elecTrical characTerisTics The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V , BAT = 4.8V , GND = PGND = 0V , unless otherwise noted.
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The L TC4010E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the 0°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Operating junction temperature T J (in °C) is calculated from the ambient temperature TA and the total continuous package power dissipation PD (in watts) by the formula: TJ = TA + qJA • PD Refer to the Applications Information section for details. This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V , BAT = 4.8V , GND = PGND = 0V , unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Charger Timing ∆tTIMER Internal Time Base Error l –10 10 % ∆tMAX Programmable Timer Error RTIMER = 49.9k l –20 20 % Status and Chemistry Select V OL Output Voltage Low (ILOAD = 10mA) V CDIV All Other Status Outputs l l 435 300 700 600 mV mV I LKG Output Leakage Current All Status Outputs Inactive, VOUT = VCC l –10 10 µA IIH(VCDIV) Input Current High VCDIV = VBAT (Shutdown) l –1 1 µA VIL Input Voltage Low CHEM (NiMH) l 900 mV VIH Input Voltage High CHEM (NiCd) l 2.85 V IIL Input Current Low CHEM = GND l –20 –5 µA IIH Input Current High CHEM = 3.3V l –20 20 µA when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. Note 4: All current into device pins are positive. All current out of device pins are negative. All voltages are referenced to GND, unless otherwise specified. Note 5: Output current may be limited by internal power dissipation. Refer to the Applications Information section for details. Note 6: Either TGATE V OH may apply for 7.5V < VCC < 9V . Note 7: These limits apply specifically to the thermistor network shown in Figure 5 in the Applications Information section with a b of 3750 and are guaranteed by specific V TEMP voltage measurements during test. Note 8: These limits are guaranteed by correlation to wafer level measurements. TIME (MINUTES) SINGLE CELL VOL TAGE (V) BATTERY TEMPERATURE (°C) 1.50 1.55 1.60
4010 G01
1.45 1.40 20 40 80 1.35 1.30 1.65 CHARGE CURRENT BATTERY TEMPERATURE SINGLE CELL VOL TAGE TIME (MINUTES) SINGLE CELL VOL TAGE (V) BATTERY TEMPERATURE (°C) 1.60 1.65 1.70
4010 G02
1.55 1.50 10 20 40 1.45 1.35 1.40 1.75 CHARGE CURRENT BATTERY TEMPERATURE SINGLE CELL VOL TAGE
4 SERIES NiCd 1300mAhr
NiCd Charge Cycle at 1C NiCd Charge Cycle at 2C Typical perForMance characTerisTics
Typical perForMance characTerisTics TIME (MINUTES)
1.30 SINGLE CELL VOL TAGE (V)
BATTERY TEMPEATURE (°C) 1.40 1.50 1.60 1.45 1.45 1.55 120
4010 G03
0 20 40 80 100 140 16060 180 200 CHARGE CURRENT TOP OFF BATTERY TEMPERATURE SINGLE CELL VOL TAGE 0.5A
4 SERIES NiMH 2100mAhr
AA CELLS CHARGED AT 0.5C TEMPERATURE (°C) –50 –30
320 VOLTAGE (mV)
–10 30 50
4010 G04
TEMPERATURE (°C) –50
850 VOLTAGE (mV)
–10 30 50
4010 G05
–30 10 70 90 TEMPERATURE (°C) –50 –30 1.275 VOLTAGE (V)1.315 1.375 –10 30 50
4010 G06
1.295 1.355 1.335 10 70 90 TEMPERATURE (°C) –50
1.85 VOLTAGE (V)
1.87 1.91 1.93 1.95 2.05 1.99 –10 30 50
4010 G07
1.89 2.01 2.03 1.97 –30 10 70 90 TEMPERATURE (°C) –50 –30 –25 VOLTAGE (mV) –15 –10 30 50
4010 G08
–20 –10 10 70 90 NiMH NiCd TEMPERATURE (°C) –50 TIMING ERROR (%, p30s)
4010 G09
–10 –30 –10 30 –15 –20 50 70 90 RTIMER = 49.9k TEMPERATURE (°C) CURRENT ERROR(%)
4010 G10
–50 10–30 –10 30 50 70 90 TEMPERATURE (°C) –30 100 1000
4010 G11
FREQUENCY (kHz) –50 90–10 30 50 70 BAT = 4.8V VCC = 12V MINIMUM (LOW DROPOUT) Automatic Recharge Threshold Voltage (per Cell) Battery Overvoltage Threshold Voltage (per Cell) –∆V Termination Voltage (per Cell) Programmable Timer Accuracy Charge Current Accuracy PWM Switching Frequency NiMH Charge Cycle at 0.5C Battery Present Threshold Voltage (per Cell) Minimum Fast Charge Threshold Voltage (per Cell)
Typical perForMance characTerisTics BATTERY VOLTAGE (V) 1 1.5 EFFICIENCY (%) 2 3 3.5
4010 G12
2.5 4 4.5 DCIN = 5.5V IOUT = 2A BATTERY VOLTAGE (V) EFFICIENCY (%) 100
4010 G13
DCIN = 20V IOUT = 2A 200µs/DIV VOLTAGE (V) AMPS (A)
4010 G14
VCC (V) CURRENT ERROR (%) 10 14 18 22
4010 G15
50°C 25°C 0°C BAT = 4.8V BATTERY VOLTAGE (V) CURRENT ERROR (%) 4 8
4010 G16
50°C 25°C 0°C VCC = 20V TEMPERATURE (°C) –50 –30 CURRENT (µA)4 –10 30 50
4010 G17
TEMPERATURE (°C) –50 CURRENT (µA) –30 –10 10 30 BAT
4010 G18
TEMPERATURE (°C) –50 –30 3.95 VOLTAGE (V)4.15 4.45 –10 30 50
4010 G19
4.05 4.35 4.25 10 70 90 TEMPERATURE (°C) –50 –30 VOLTAGE (mV) 100 –10 30 50
4010 G20
Fast Charge Current Output Regulation Shutdown Quiescent Current PWM Input Bias Current (OFF) Undervoltage Lockout Threshold Voltage Shutdown Threshold Voltage CC – BAT) Charger Efficiency Charger Efficiency Charger Soft-Start
Typical perForMance characTerisTics TEMPERATURE (°C) –50
400 VOLTAGE (mV)
–30 –10 10 30
4010 G21
TEMPERATURE (°C) –50 –30 2.8 VOLTAGE (V)3.0 3.3 –10 30 50
4010 G22
2.9 3.2 3.1 10 70 90 TEMPERATURE (°C) –50 210 230 270 10 50
4010 G23
–30 –10 30 70 90 150 130 250VOLTAGE (mV) TEMPERATURE (°C) –50 –30 4.5 VOLTAGE (V)4.9 5.5 –10 30 50
4010 G24
4.7 5.3 5.1 10 70 90 NO LOAD TEMPERATURE (°C) –50 CURRENT (mA) –40 –35 –30 10 50
4010 G25
–45 –50 –30 –10 30 70 90 –55 –60 INTVDD Voltage INTVDD Short-Circuit Current Charge Enable Threshold Voltage (VCC – BAT) Thermistor Disable Threshold Voltage Pause Threshold Voltage pin FuncTions FAULT (Pin 1): Active-Low Fault Indicator Output. The L TC4010 indicates various battery and internal fault condi- tions by connecting this pin to GND. Refer to the Operation and Applications Information sections for further details. This output is capable of driving an LED and should be left floating if not used. FAULT is an open-drain output to GND with an operating voltage range of GND to V CC. CHRG (Pin 2): Active-Low Charge Indicator Output. The L TC4010 indicates it is providing charge to the battery by connecting this pin to GND. Refer to the Operation and Applications Information sections for further details. This output is capable of driving an LED and should be left floating if not used. CHRG is an open-drain output to GND with an operating voltage range of GND to V CC. CHEM (Pin 3): Battery Chemistry Selection Input. This pin should be wired to GND to select NiMH fast charge termination parameters. If a voltage greater than 2.85V is applied to this pin, or it is left floating, NiCd parameters are used. Refer to the Applications Information section for further details. Operating voltage range is GND to 3.3V .
GND (Pin 4): Ground. This pin provides a single-point ground for internal references and other critical analog circuits. V TEMP (Pin 5): Battery Temperature Input. An external 10k NTC thermistor may be connected between V TEMP and GND to provide temperature-based charge qualification and additional fast charge termination control. Charging may also be paused by connecting the V TEMP pin to GND. Refer to the Operation and Applications Information sec- tions for complete details on external thermistor networks and charge control. If this pin is not used it should be wired to GND through 10k. Operating voltage range is GND to 3.3V . V CELL (Pin 6): Average Single-Cell Voltage Input. An external voltage divider between BAT and VCDIV is attached to this pin to monitor the average single-cell voltage of the bat- tery pack. The L TC4010 uses this information to protect against catastrophic battery overvoltage and to control the charging state. Refer to the Applications Information section for further details on the external divider network. Operating voltage range is GND to BAT . V CDIV (Pin 7): Average Cell Voltage Resistor Divider Termi- nation. The L TC4010 connects this pin to GND provided the charger is not in shutdown. VCDIV is an open-drain output to GND with an operating voltage range of GND to BAT . TIMER (Pin 8): Charge Timer Input. A resistor connected between TIMER and GND programs charge cycle timing limits. Refer to the Applications Information section for complete details. Operating voltage range is GND to 1V . SENSE (Pin 9): Charge Current Sense Input. An external resistor between this input and BAT is used to program charge current. Refer to the Applications Information section for complete details on programming charge current. Operating voltage ranges from (BAT – 50mV) to (BAT + 200mV). BAT (Pin 10): Battery Pack Connection. The L TC4010 uses the voltage on this pin to control current sourced from V CC to the battery during charging. Allowable operating voltage range is GND to VCC. INTVDD (Pin 11): Internal 5V Regulator Output. This pin provides a means of bypassing the internal 5V regulator used to power the BGATE output driver . Typically, power should not be drawn from this pin by the application circuit. Refer to the Application Information section for additional details. BGATE (Pin 12): External Synchronous N-channel MOSFET Gate Control Output. This output provides gate drive to an optional external NMOS power transistor switch used for synchronous rectification to increase efficiency in the step-down DC/DC converter . Operating voltage is GND to INTV DD. BGATE should be left floating if not used. PGND (Pin 13): Power Ground. This pin provides a return for switching currents generated by internal L TC4010 cir- cuits. Externally, PGND and GND should be wired together using a very low impedance connection. Refer to PCB Layout Considerations in the Applications Information section for additional grounding details. TGATE (Pin 14): External P-channel MOSFET Gate Control Output. This output provides gate drive to an external PMOS power transistor switch used in the DC/DC converter . Op- erating voltage range varies as a function of V CC. Refer to the Electrical Characteristics table for specific voltages. VCC (Pin 15): Power Input. External diodes normally connect either the DC input power supply or the battery to this pin. Refer to the Applications Information section for further details. Suggested applied voltage range is GND to 34V . READY (Pin 16): Active-Low Ready-to-Charge Output. The L TC4010 connects this pin to GND if proper operating voltages for charging are present. Refer to the Operation section for complete details on charge qualification. This output is capable of driving an LED and should be left floating if not used. READY is an open-drain output to GND with an operating voltage range of GND to V CC. Exposed Pad (Pin 17): This pin provides enhanced thermal properties for the TSSOP . It must be soldered to the PCB copper ground to obtain optimum thermal performance.
2 CHRG
1 FAULT
8 TIMER
4010 F01
Figure 1. L TC4010 State Diagram
The L TC4010 remains in micropower shutdown until VCC (Pin 15) is driven above BAT (Pin 10). In shutdown all status and PWM outputs and internally generated supply voltages are inactive. Current consumption from V CC and BAT is reduced to a very low level. Charge Qualification State Once VCC is greater than BAT , the L TC4010 exits micropower shutdown, enables its own internal supplies and switches VCDIV to GND to allow measurement of the average single- cell voltage. The IC also verifies that VCC is at or above 4.2V , VCC is 510mV above BAT and VCELL is between 350mV and 1.95V . If VCELL is below 350mV , no charging will occur , and if VCELL is above 1.95V , the fault state is entered, which is described in more detail below. Once adequate voltage conditions exist for charging, READY is asserted. If the voltage between V TEMP and GND is below 200mV , the L TC4010 is paused. If VTEMP is above 200mV but below 2.85V , the L TC4010 verifies that the sensed temperature is between 5°C and 45°C. If these temperature limits are not met or if its own die temperature is too high, the L TC4010 will indicate a fault and not allow charging to begin. If V TEMP is greater than 2.85V , battery temperature related charge qualification, monitoring and termination are disabled. Once charging is fully qualified, precharge begins (unless the L TC4010 is paused). In that case, the V TEMP pin is monitored for further control. The charge status indicators and PWM outputs remain inactive until charging begins. Charge Monitoring The L TC4010 continues to monitor important voltage and temperature parameters during all charging states. If V CC drops to the BAT voltage or lower , charging stops and the shutdown state is entered. If V CC drops below 4.25V or VCELL drops below 350mV , charging stops and the L TC4010 returns to the charge qualification state. If VCELL exceeds 1.95V , charging stops and the IC enters the fault state. If an external thermistor indicates sensed temperature is beyond a range of 5°C to 60°C, or the internal die temperature exceeds a resonable value, charging is suspended, the charge timer is paused and the L TC4010 indicates a fault condition. Normal charging resumes from the previous state when the sensed temperature returns to a satisfactory range. In addition, other battery faults are detected during specific charging states as described below. Precharge State If the initial voltage on V CELL is below 900mV , the L TC4010 enters the precharge state and enables the PWM current source to trickle charge using one-fifth the programmed charge current. The CHRG status output is active during precharge. The precharge state duration is limited to t MAX/12 minutes, where tMAX is the maximum fast charge period programmed with the TIMER pin. If sufficient VCELL voltage cannot be developed in this length of time, the fault state is entered, otherwise fast charge begins. Fast Charge State If adequate average single-cell voltage exists, the L TC4010 enters the fast charge state and begins charging at the programmed current set by the external current sense resistor connected between the SENSE and BAT pins. The CHRG status output is active during fast charge. If V CELL is initially above 1.325V , voltage-based termination processing begins immediately. Otherwise –∆V termination is disabled for a stabilization period of t MAX/12. In that case, the L TC4010 makes another fault check at tMAX/12, requiring the average cell voltage to be above 1.22V . This ensures the battery pack is accepting a fast charge. If V CELL is not above this voltage threshold, the fault state is entered. Fast charge state duration is limited to tMAX and the fault state is entered if this limit is exceeded. operaTion (Refer to Figure 1)
operaTion (Refer to Figure 1) Charge Termination Fast charge termination parameters are dependent upon the battery chemistry selected with the CHEM pin. Volt- age-based termination (–∆V) is always active after the initial voltage stabilization period. If an external thermistor network is present, chemistry-specific limits for ∆T/∆t (rate of temperature rise) are also used in the termination algo- rithm. Temperature-based termination, if enabled, becomes active as soon as the fast charge state is entered. Successful charge termination requires a charge rate between C/2 and 2C. Lower rates may not produce the battery voltage and temperature profile required for charge termination. Top-Off Charge State If NiMH fast charge termination occurs because the ∆T/∆t limit is exceeded after an initial period of t MAX/12 has expired, the L TC4010 enters the top-off charge state. Top-off charge is implemented by sourcing one-tenth the programmed charge current for t MAX/3 minutes to ensure that 100% charge has been delivered to the battery. The CHRG status output is active during the top-off state. If NiCd cells have been selected with the CHEM pin, the L TC4010 never enters the top-off state. Automatic Recharge State Once charging is complete, the automatic recharge state is entered to address the self-discharge characteristics of nickel chemistry cells. The charge status output is inactive during automatic recharge, but V CDIV remains switched to GND to monitor the average cell voltage. If the V CELL voltage drops below 1.325V without falling below 350mV , the charge timer is reset and a new fast charge cycle is initiated. The internal termination algorithms of the L TC4010 are adjusted when a fast charge cycle is initiated from auto- matic recharge, because the battery should be almost fully charged. Voltage-based termination is enabled immediately and the NiMH ∆T/∆t limit is fixed at a battery temperature rise of 1°C/minute. Fault State As discussed previously, the L TC4010 enters the fault state based on detection of invalid battery voltages during vari- ous charging phases. The IC also monitors the regulation of the PWM control loop and will enter the fault state if this is not within acceptable limits. Once in the fault state, the battery must be removed or DC input power must be cycled in order to initiate further charging. In the fault state, the FAULT output is active, the READY output is inactive, charging stops and the charge indicator output is inactive. The V CDIV output remains connected to GND to allow detection of battery removal. Note that the L TC4010 also uses the FAULT output to indi- cate that charging is suspended due to invalid battery or internal die temperatures. However , the IC does not enter the fault state in these cases and normal operation will resume when all temperatures return to acceptable levels. Refer to the Status Outputs section for more detail. Insertion and Removal of Batteries The L TC4010 automatically senses the insertion or removal of a battery by monitoring the V CELL pin voltage. Should this voltage fall below 350mV , the IC considers the bat- tery to be absent. Removing and then inserting a battery causes the L TC4010 to initiate a completely new charge cycle beginning with charge qualification. External Pause Control After charging is initiated, the V TEMP pin may be used to pause operation at any time. When the voltage between VTEMP and GND drops below 200mV , the charge timer pauses, fast charge termination algorithms are inhibited and the PWM outputs are disabled. The status and V CDIV outputs all remain active. Normal function is fully restored from the previous state when pause ends.
Figure 2. L TC4010 PWM Control Loop
9 SENSE
12 BGATE
14 TGATE
4010 F02
VCELL resistor divider , as previously discussed. Table 1. L TC4010 Status Pins BGATE outputs have internally clamped voltage swings.
the average current through R SENSE. The I TH output of the error amplifier is a scaled control current for the input of the PWM comparator CC. The ITH • R3 product sets a peak current threshold for CC such that the desired aver- age current through R SENSE is maintained. The current comparator output does this by switching the state of the SR latch at the appropriate time. At the beginning of each oscillator cycle, the PWM clock sets the SR latch and the external P-channel MOSFET is switched on (N-channel MOSFET switched off) to refresh the current carried by the external inductor . The inductor current and voltage drop across R SENSE begin to rise linearly. During normal operation, the PFET is turned off (NFET on) during the cycle by CC when the voltage difference across R SENSE reaches the peak value set by the output of EA. The inductor current then ramps down linearly until the next rising PWM clock edge. This closes the loop and maintains the desired average charge current in the external inductor . Low Dropout Charging After charging is initiated, the L TC4010 does not require that V CC remain at least 500mV above BAT because situ- ations exist where low dropout charging might occur . In one instance, parasitic series resistance may limit PWM headroom (between V CC and BAT) as 100% charge is reached. A second case can arise when the DC adapter selected by the end user is not capable of delivering the current programmed by R SENSE, causing the output volt- age of the adapter to collapse. While in low dropout, the L TC4010 PWM runs near 100% duty cycle with a frequency that may not be constant and can be less than 550kHz. The charge current will drop below the programmed value to avoid generating audible noise, so the actual charge delivered to the battery may depend primarily on the L TC4010 charge timer . Internal Die Temperature The L TC4010 provides internal overtemperature detection to protect against electrical overstress, primarily at the FET driver outputs. If the die temperature rises above this thermal limit, the L TC4010 stops switching and indicates a fault as previously discussed. operaTion (Refer to Figure 1)
The external DC power source should be connected to the charging system and the VCC pin through a power diode acting as an input rectifier . This prevents catastrophic system damage in the event of an input short to ground or reverse-voltage polarity at the DC input. The L TC4010 automatically senses when this input drives the V CC pin above BAT . The open-circuit voltage of the DC source should be between 5.5V and 34V , depending on the num- ber of cells being charged. In order to avoid low dropout operation, ensure 100% capacity at charge termination, and allow reliable detection of battery insertion, removal or overvoltage, the following equation can be used to determine the minimum full-load voltage that should be produced at V CC when the external DC power source is connected. VCC(MIN) = (n • 2V) + 0.3V where n is the number of series cells in the battery pack. The L TC4010 will properly charge over a wide range of V CC and BAT voltage combinations. Operating the L TC4010 in low dropout or with VCC much greater than BAT will force the PWM frequency to be much less than 550kHz. The L TC4010 disables charging and sets a fault if a large V CC to BAT differential would cause generation of audible noise. Load Control Proper load current control is an important consideration when fast charging nickel cells. This control ensures that the system load remains powered at all times, but that normal system operation and associated load transients do not adversely affect fast charge termination. The input protecton detailed in the previous paragraph is an integral part of the necessary load control. The battery should also be connected to the raw system supply by some rectifying means, thus forming a switch that selects the battery for system power only if an external DC source is not present. Battery Chemistry Selection The desired battery chemistry is selected by program- ming the CHEM pin to the proper voltage. If it is wired to GND, a set of parameters specific to charging NiMH applicaTions inForMaTion cells is selected. When CHEM is left floating, charging is optimized for NiCd cells. The various charging parameters are detailed in Table 2. Programming Charge Current Charge current is programmed using the following equation: R mV ISENSE PROG = 100 RSENSE is an external resistor connected between the SENSE and BAT pins. A 1% resistor with a low temperature coefficient and sufficient power dissipation capability to avoid self-heating effects is recommended. Charge rate should be between approximately C/2 and 2C. Inductor Value Selection For many applications, 10µH represents an optimum value for the inductor the PWM uses to generate charge current. For applications with I PROG of 1.5A or greater running from an external DC source of 15V or less, values between 5µH and 7.5µH can often be selected. For wider operating conditions the following equation can be used as a guide for selecting the minimum inductor value. L > 6.5 • 10 –6 • VDCIN • RSENSE, L ≥ 4.7µH Actual part selection should account for both manufacturing tolerance and temperature coefficient to ensure this mini- mum. A good initial selection can be made by multiplying the calculated minimum by 1.4 and rounding up or down to the nearest standard inductance value. Ultimately, there is no substitute for bench evaluation of the selected inductor in the target application, which can also be affected by other environmental factors such as ambient operating temperature. Using inductor values lower than recommended by the equation shown above can result in a fault condition at the start of precharge or top-off charge. Programming Maximum Charge Times Connecting the appropriate resistor between the TIMER pin and GND programs the maximum duration of various
- –30 10 6 Some typical timing values are detailed in Table 3. RTIMER should not be less than 15k. The actual time limits used by the L TC4010 have a resolution of approximately ±30 seconds in addition to the tolerances given the Electrical Characteristics table. If the timer ends without a valid –∆V or ∆T/∆t charge termination, the charger enters the fault state. The maximum time period is approximately 4.3 hours. Cell Voltage Network Design An external resistor network is required to provide the average single-cell voltage to the V CELL pin of the L TC4010. applicaTions inForMaTion The proper circuit for multicell packs is shown in Figure 3. The ratio of R2 to R1 should be a factor of (n – 1), where n is the number of series cells in the battery pack. The value of R1 should be between 1k and 100k. This range limits the sensing error caused by V CELL leakage current and prevents the ON resistance of the internal NFET be- tween V CDIV and GND from causing a significant error in the VCELL voltage. The external resistor network is also used to detect battery insertion and removal. The filter
Figure 3. Multiple Cell Voltage Divider
4010 F03
Table 2. L TC4010 Charging Parameters Table 3. L TC4010 Time Limit Programming Examples
battery from a severe overcharge. ceramic bypass capacitor of 0.1µF is recommended. temperature is not exceeded under all operating conditions. normal operating conditions. Figure 4. Single-Cell Monitor Network
1 CELL
4010 F04
Figure 5. External NTC Thermistor Network
4010 F05
Temperature sensing is optional in L TC4010 applications.
strate some of the proper configurations of the L TC4010. encountered in low cost NiCd fast charge applications. as no external temperature information is available. full-featured 2A L TC4010 application is shown in Figure 7. pin selects the NiMH charge termination parameter set. Figure 6. Minimum 1 Amp L TC4010 Application
4010 F06
Figure 7. Full-Featured 2 Amp L TC4010 Application
4010 F07
Figure 8. L TC4010 with MCU Interface
4010 F08
battery continues to power the system during charging. P-channel MOSFET in this application. by the L TC4010 during a typical charge cycle. when the L TC4010 completes charge qualification. starts a precharge cycle because VCELL is less than 900mV . bring the average cell voltage to 900mV . Figure 9. Charging Waveforms Example
4010 F09
status outputs continue to indicate charging is in progress. be an increase greater than 1°C per minute. minutes with the CHRG output continuously asserted. the battery in the absence of an input power source. and providing temperature information. needs. Charging parallel cells is not recommended. PCB design priority list will help ensure proper topology. Layout the PCB using this specific order . Figure 10. NiCd Battery Pack with Time Limit Control
4010 F10
Figure 11. NiMH Battery Pack Indicating Number of Cells
4010 F11
- Input capacitors should be placed as close as possible
side of the PCB from the switching FETs. needed to support the programmed charge current. that current sense traces to the L TC4010 are not long. not at the sense resistor location.
- Output capacitor ground connections must feed into
ground before tying back into system ground. or any internal ground plane should be single-point. point to make the connection. ductance, which further improves EMI performance. Kelvin connection from R SENSE to SENSE and BAT . See Figure 13 for an example. Figure 12. High Speed Switching Path
4010 F12
Figure 13. Kelvin Sensing of Charge Current
4010 F13
FE16 (BC) TSSOP 0204 0.09 – 0.20 (.0035 – .0079) 0o – 8o 0.25 REF 0.50 – 0.75 (.020 – .030) 4.30 – 4.50* (.169 – .177) 1 3 4 5 6 7 8 10 9 4.90 – 5.10* (.193 – .201) 16 1514 13 12 11 1.10 (.0433) MAX 0.05 – 0.15 (.002 – .006) 0.65 (.0256) BSC 2.94 (.116) 0.195 – 0.30 (.0077 – .0118) TYP 2RECOMMENDED SOLDER PAD LAYOUT 0.45 p0.05
0.65 BSC
4.50 p0.10 6.60 p0.10 1.05 p0.10 2.94 (.116) 3.58 (.141) 3.58 (.141) MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE SEE NOTE 4 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT 6.40 (.252) BSC 16-Lead Plastic TSSOP (4.4mm) (Reference L TC DWG # 05-08-1663) Exposed Pad Variation BC
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However , no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER B 01/10 Changes to Typical Application Updated Order Information Section Changes to Electrical Characteristics Changes to Pin Functions (V TEMP, Pin 5) Changes to Operation Section Changes to Applications Information Changes to Figures 6, 7, 8 2, 3 10, 11 14, 15, 16, 17, 19, 20 17, 18 (Revision history begins at Rev B)
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com LINEAR TECHNOLOGY CORPORATION 2005 LT 0110 REV B • PRINTED IN USA relaTeD parTs PART NUMBER DESCRIPTION COMMENTS L T®1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.5A Charge Current for Li-Ion, NiCd and NiMH Batteries L T1511 3A Constant-Voltage/Constant-Current Battery Charger High Efficiency, Minimum External Components to Fast Charge Lithium, NiMH and NiCd Batteries L T1513 SEPIC Constant- or Programmable-Current/Constant- Voltage Battery Charger Charger Input Voltage May be Higher , Equal to or Lower than Battery Voltage, 500kHz Switching Frequency L TC1760 Smart Battery System Manager Autonomous Power Management and Battery Charging for T wo Smart Batteries, SMBus Rev 1.1 Compliant L TC1960 Dual Battery Charger/Selector with SPI 11-Bit V-DAC, 0.8% Voltage Accuracy, 10-Bit I-DAC, 5% Current Accuracy L TC4008 High Efficiency, Programmable Voltage/Current Battery Charger Constant-Current/Constant-Voltage Switching Regulator , Resistor Voltage/Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator Outputs L TC4011 High Efficiency Standalone Nickel Battery Charger Complete NiMH/NiCd Charger in a 20-Pin TSSOP Package, PowerPath TM Control, Constant-Current Switching Regulator L TC4060 Standalone Linear NiMH/NiCd Fast Charger Complete NiMH/NiCd Charger in a Small Leaded or Leadless 16-Pin Package, No Sense Resistor or Blocking Diode Required L TC4100 Smart Battery Charger Controller Level 2 Charger Operates with or without MCU Host, SMBus Rev. 1.1 Compliant L TC4150 Coulomb Counter/Battery Gas Gauge High Side Sense of Charge Quantity and Polarity in a 10-Pin MSOP L TC4412 Low Loss PowerPath Controller Very Low Loss Replacement for Power Supply ORing Diodes Using Minimal External Components, V IN(MAX) = 28V L TC4412HV 36V , Low Loss PowerPath Controller in ThinSOT Very Low Loss Replacement for Power Supply ORing Diodes, VIN(MAX) = 36V L TC4413 Dual, 2.6A Ideal Diode in 3mm × 3mm DFN 2.5V ≤ VIN ≤ 5.5V , Ideal Diode ORing or Load Sharing, Low Reverse Leakage Current L TC4414 36V , Low Loss PowerPath Controller for Large PFETs Higher Gate Drive for Larger Q G PFETs, VIN(MAX) = 36V , 8-Pin MSOP Package PowerPath is a trademark of Linear Technology Corporation.