LTC4010 LINEAR | Alldatasheet

Document overview

  • Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
  • PDF pages: 20

Technical content

High Efficiency Standalone Nickel Battery Charger ■ Complete NiMH/NiCd Charger for 1 to 16 Cells ■ No Microcontroller or Firmware Required ■ 550kHz PWM Current Source Controller ■ No Audible Noise with Ceramic Capacitors ■ Wide Input Voltage Range: 5.5V to 34V ■ Programmable Charge Current: 5% Accuracy ■ Automatic Trickle Precharge ■ –∆V Fast Charge Termination ■ Optional ∆T/∆t Fast Charge Termination ■ Optional Temperature Qualification ■ Automatic NiMH Top-Off Charge ■ Programmable Maximum Charging Durations ■ Automatic Recharge ■ Multiple Status Outputs ■ Micropower Shutdown ■ 16-Lead Thermally Enhanced TSSOP Package ■ Integrated or Standalone Battery Charger ■ Portable Instruments or Consumer Products ■ Battery-Powered Diagnostics and Control ■ Back-Up Battery Management , LTC and LT are registered trademarks of Linear Technology Corporation. The LTC 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 LTC4010 automatically senses the presence of a DC adapter and battery insertion or removal. When an exter- nal DC source is not present, the LTC4010 enters shut- down and supply current drawn from an installed battery drops to the lowest possible level. Heavily discharged batteries are precharged with a trickle current. The LTC4010 can simultaneously use both –∆V and ∆T/∆t fast charge termination 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 LTC4010 charging operations are qualified by actual charge time and maximum average cell voltage. Charging may also be gated by minimum and maximum tempera- ture limits. NiMH or NiCd fast charge termination param- eters are pin selectable. FEATURES DESCRIPTIO U APPLICATIO SU TYPICAL APPLICATIO U 2A NiMH Battery Charger TIME (MINUTES) 1.0 AVERAGE CELL VOLTAGE (V) CELL CASE TEMPERATURE (°C) 1.2 1.4 1.6 1.8 2.2 10 20 30 40

4011 TA01b

2.0 TOP OFF CHARGE Typical NiMH Charge at 1.25C FAULT CHRG READY V CC TGATE VCDIV VCELL VTEMP LTC4010 TIMER INTVDD GND CHEM SENSE BAT FROM ADAPTER 5.5V TO 34V 10µH TO SYSTEM LOAD 0.05Ω 2-CELL NiMH PACK WITH 10k NTC

4010 TA01a

R 49.9k 10k 10k 0.1µF 68nF 10µF 33nF 10µF BGATE PGND Electrical Specifications Subject to Change

(Note 1) FAULT, CHRG, VCELL, VCDIV, BAT Operating Ambient Temperature Range LTC4010EFE TJMAX = 125°C, θJA = 38°C/W EXPOSED PAD (PIN 17) IS GND. MUST BE SOLDERED TO PCB TO OBTAIN SPECIFIED THERMAL RESISTANCE ABSOLUTE MAXIMUM RATINGSW WW U PACKAGE/ORDER INFORMATIONW UU The ● 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. Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCC Supply VCC Input Voltage Range ● 4.5 34 V ISHDN Shutdown Quiescent Current V CC = BAT = 4.8V ● 51 0 µA IQ Quiescent Current Waiting to Charge (Pause) ● 3 4.5 mA ICC Operating Current Fast Charge State, No Gate Load ● 57 m A VUVLO Undervoltage Threshold Voltage V CC Increasing ● 4.15 4.25 4.35 V VUV(HYST) Undervoltage Hysteresis Voltage 170 mV VSHDNI Shutdown Threshold Voltage DCIN – V CC, DCIN Increasing ● 45 65 90 mV VSHDND Shutdown Threshold Voltage DCIN – V CC, DCIN Decreasing ● 15 25 38 mV VCE Charge Enable Threshold Voltage V CC – BAT, VCC Increasing ● 455 545 mV INTVDD Regulator VDD Output Voltage No Load ● 4.5 5 5.5 V IDD Short-Circuit Current (Note 5) INTV DD = 0V ● 28 50 100 mA INTVDD(MIN) Output Voltage V CC = 4.5V, IDD = –10mA ● 3.85 V PWM Current Source VFS BAT – SENSE Full-Scale Regulation 0.3V < BAT < V CC – 0.1V, 0°C < TA < 50°C ● 95 100 105 mV Voltage (Fast Charge) VPC BAT – SENSE Precharge Regulation 0.3V < BAT < V CC – 0.1V, 0°C < TA < 50°C ● 17 20 23 mV Voltage VTC BAT – SENSE Top-Off Charge 0.3V < BAT < V CC – 0.1V, 0°C < TA < 50°C ● 7.5 10 12.5 mV Regulation Voltage FE PACKAGE 16-LEAD PLASTIC TSSOP TOP VIEW FAULT CHRG CHEM GND V TEMP VCELL VCDIV TIMER READY VCC TGATE PGND BGATE INTV DD BAT SENSE

The ● 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 ∆VLI BAT – SENSE Line Regulation 5.5V < V CC < 34V, Fast Charge ● 1 TBD mV IBAT BAT Input Bias Current 0.3V < BAT < V CC – 0.1V –2 0 2 mA ISENSE SENSE Input Bias Current SENSE = BAT 50 150 µA IOFF Input Bias Current SENSE or BAT, V CELL = 0V ● –1 0 1 µA fTYP Typical Switching Frequency ● 485 550 615 kHz fMIN Minimum Switching Frequency ● 20 30 kHz DCMAX Maximum Duty Cycle 98 99 % VOL(TG) TGATE Output Voltage Low (Note 6) V CC ≥ 9V, No Load (VCC – TGATE) ● 5.35 6.3 8.75 V VCC ≤ 7.5V, No Load ● 50 mV VOH(TG) TGATE Output Voltage High V CC – TGATE, No Load ● 05 0 m V tR(TG) TGATE Rise Time C LOAD = 3nF, 10% to 90% 35 50 ns tF(TG) TGATE Fall Time C LOAD = 3nF, 10% to 90% 45 100 ns VOL(BG) BGATE Output Voltage Low No Load ● 05 0 m V VOH(BG) BGATE Output Voltage High No Load ● INTVDD INTVDD V – 0.05 tR(BG) BGATE Rise Time C LOAD = 1.6nF, 10% to 90% 30 65 ns tF(BG) BGATE Fall Time C LOAD = 1.6nF, 10% to 90% 10 25 ns ADC Inputs ILEAK Analog Channel Leakage 0V < V CELL < 2V, 0V < VTEMP < 2V ±100 nA Charger Thresholds VBP Battery Present Threshold Voltage ● 340 350 360 mV VBOV Battery Overvoltage ● 1.9 1.95 2 V VMFC Minimum Fast Charge Voltage ● 875 900 925 mV VFCBF Fast Charge Battery Fault Voltage ● 1.17 1.22 1.27 V ∆VV(TERM) –∆V Termination CHEM = Open (NiCd) ● 18 20 22.0 mV CHEM = 0V (NiMH) ● 8.5 10 11.5 mV VAR Automatic Recharge Voltage V CELL Decreasing ● 1.275 1.325 1.375 V ∆VT(TERM) ∆T Termination (Note 7) CHEM = Open (NiCd) ● 1.84 2 2.16 °C/MIN CHEM = 0V (NiMH) ● 0.86 1 1.14 °C/MIN VT(MIN) Minimum Charging Temperature V TEMP Increasing ● 357 °C (Note 7) VT(MAXI) Maximum Charge Initiation V TEMP Decreasing, Not Charging ● 43 45 47 °C Temperature (Note 7) VT(MAXC) Maximum Charging Temperature V TEMP Decreasing, Charging ● 58 60 62 °C (Note 7) VTEMP(D) VTEMP Disable Threshold Voltage ● 2.85 3.3 V VTEMP(P) Pause Threshold Voltage ● 160 280 mV Charger Timing ∆tTIMER Internal Time Base Error ● –10 10 % ∆tMAX Programmable Timer Error R TIMER = 49.9k ● –15 15 %

The ● 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: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC4010E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40 °C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Operating junction temperature TJ (in °C) is calculated from the ambient temperature TA and the total continuous package power dissipation PD (in watts) by the formula: TJ = TA + θJA • 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 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 specified output may apply for 7.5V < V CC < 9V. Note 7: These limits apply specifically to the thermistor network shown in Figure 5 in the Applications Information section and are guaranteed by specific V TEMP voltage measurements during test. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Status and Chemistry Select VOL Output Voltage Low All Status Outputs and V CDIV, ILOAD = 10mA ● 300 600 mV ILKG Output Leakage Current All Status Outputs Inactive, V OUT = VCC ● –10 10 µA IIH(VCDIV) Input Current High V CDIV = VBAT (Shutdown) ● –1 1 µA VIL Input Voltage Low CHEM (NiMH) ● 900 mV VIH Input Voltage High CHEM (NiCd) ● 2.85 V IIL Input Current Low CHEM = GND ● –20 –5 µA IIH Input Current High CHEM = 3.3V ● –20 20 µA

TYPICAL PERFOR A CE CHARACTERISTICS UW Typical NiMH Charge Cycle at 1C NiCd Charge at 2C NiMH Charge at 0.6C Charger Efficiency at DCIN = 20V, IOUT = 2A Charge Current Accuracy Charger Soft-Start Fast Charge Current Line Regulation PowerPath Switching Fast Charge Current Output Regulation TIME (MINUTES) CELL VOLTAGE (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 VOLTAGE BATTERY VOLTAGE (V) EFFICIENCY (%) 100

4010 G04

TEMPERATURE (°C) –12 CURRENT ERROR (%) –10 10 20 30 40

4010 G05

VCC = 12V BAT = 4.8V 200µs/DIV VOLTAGE (V)

4010 G06

VCC (V) CURRENT ERROR (%) 10 14 18 22

4010 G07

50°C 25°C 0°C BAT = 4.8V BAT (V) CURRENT ERROR (%) 4 8

4010 G08

50°C 25°C 0°C VCC = 20V VOLTAGE (V)

4010 G09

100µs/DIV DC674A WITH 1kΩ SYSTEM LOAD AND 20kΩ DCIN SHUNT, CHARGER PAUSED VCC INFET DCIN DCIN OPEN

FAULT (Pin 1): Active-Low Fault Indicator Output. The LTC4010 indicates various battery and internal fault con- ditions by connecting this pin to GND. Refer to the Opera- tion 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 LTC4010 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. VTEMP (Pin 5): Battery Temperature Input. An external 10k NTC thermistor may be connected between V TEMP and GND to provide temperature-based charge qualifica- tion and additional fast charge termination control. Charg- ing may also be paused by connecting the V TEMP pin to GND. Refer to the Operation and Applications Informa- tion sections for complete details on external thermistor networks and charge control. If this pin is not used it should be wired to INTV DD through 56k. Operating volt- age range is GND to 3.3V. VCELL (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 battery pack. The LTC4010 uses this information to pro- tect against catastrophic battery overvoltage and to con- trol 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 Ter- mination. The LTC4010 connects this pin to GND provided the charger is not in shutdown. V CDIV 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 LTC4010 uses the voltage on this pin to control current sourced from V CC to the battery during charging. Allowable operating volt- age range is GND to V CC. 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 LTC4010 circuits. Externally, PGND and GND should be wired together using a very low impedance connection. Refer to PCB Layout Considerations in the Applications Informa- tion 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 con- verter. Operating 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 con- nect either the DC input power supply or the battery to this pin. Refer to the Applications Information section for fur- ther details. Suggested applied voltage range is GND to 34V. UUUPI FU CTIO S READY (Pin 16): Active-Low Ready-to-Charge Output. The LTC4010 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. BLOCK DIAGRA W CHARGER STATE CONTROL LOGIC THERMISTOR INTERFACE A/D CONVERTER BATTERY DETECTOR VOLTAGE REGULATOR UVLO AND SHUTDOWN PWM CHARGE TIMER VOLTAGE REFERENCE INTERNAL VOLTAGE REGULATOR VTEMP CHEM

2 CHRG

1 FAULT

8 TIMER

Figure 1. LTC4010 State Diagram

4010 F01

BAT is reduced to a very low level. and PWM outputs remain inactive until charging begins.

beyond a range of 5°C to 60°C, or the internal die tempera- ture exceeds a resonable value, charging is suspended, the charge timer is paused and the LTC4010 indicates a fault condition. Normal charging resumes from the previ- ous state when the sensed temperature returns to a satis- factory 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 LTC4010 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 LTC4010 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, cell voltage processing begins immediately. Otherwise –∆V termination is disabled for a stabilization period of tMAX/12. In that case, the LTC4010 makes another fault check at tMAX/12, requiring the aver- age 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 t MAX and the fault state is entered if this limit is exceeded. 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 algorithm. Temperature-based termination, if enabled, becomes active as soon as the fast charge state is entered. (Refer to Figure 1) Top-Off Charge State If NiMH fast charge termination occurs because the ∆T/∆t limit is exceeded after an initial period of tMAX/12 has ex- pired, the LTC4010 enters the top-off charge state. Top-off charge is implemented by sourcing one-tenth the pro- grammed charge current for tMAX/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 LTC4010 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 LTC4010 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 immedi- ately and the NiMH ∆T/∆t limit is fixed at a battery temperature rise of 1°C/minute. Fault State As discussed previously, the LTC4010 enters the fault state based on detection of invalid battery voltages during various charging phases. The IC also monitors the regu- lation 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 LTC4010 also uses the FAULT output to indicate 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

levels. Refer to the Status Outputs section for more detail. moval of a battery by monitoring the V CELL pin voltage. charge cycle beginning with charge qualification. from the previous state when pause ends. nate the VCELL resistor divider, as previously discussed. BGATE outputs have internally clamped voltage swings. and BAT that ranges from 10mV to 100mV. Table 1. LTC4010 Status Pins

9 SENSE

12 BGATE

14 TGATE

4010 F02

current threshold for CC such that the desired average current through RSENSE is maintained. The current com- parator 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 RSENSE 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 LTC4010 does not require that V CC remain at least 500mV above BAT because situations exist where low dropout charging might occur. OPERATIOU 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 LTC4010 PWM runs near 100% duty cycle with a fre- quency that may not be constant and can be less than 550kHz. The charge current will drop below the pro- grammed value to avoid generating audible noise, so the actual charge delivered to the battery may depend prima- rily on the LTC4010 charge timer. Internal Die Temperature The LTC4010 provides internal overtemperature detec- tion to protect against electrical overstress, primarily at the FET driver outputs. If the die temperature rises above this thermal limit, the LTC4010 stops switching and indicates a fault as previously discussed. APPLICATIO S I FOR ATIOWU UU External DC Source 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 reverse-voltage polarity at the DC input. The LTC4010 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 number 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 LTC4010 will properly charge over a wide range of VCC and BAT voltage combinations. Operating the LTC4010 in low dropout or with VCC much greater than BAT will force the PWM frequency to be much less than 550kHz. The LTC4010 disables charging and sets a fault if a large VCC to BAT differential would cause generation of audible noise. Load Control Proper current load 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

avoid self-heating effects is recommended.

  • –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 LTC4010 have a resolution of approximately ±30 seconds in addition to the tolerances given the Electrical Characteristics table. The maximum time period is ap- proximately 4.3 hours.

Table 2. LTC4010 Charging Parameters Table 3. LTC4010 Time Limit Programming Examples

average single-cell voltage to the VCELL pin of the LTC4010. The proper circuit for multicell packs is shown in Figure 3. best with a 1% 10k NTC thermistor with a β of 3750. rejecting PWM switching noise. Figure 4. Single-Cell Monitor Network Figure 3. Multiple Cell Voltage Divider

4010 F03

1 CELL

4010 F04

Figure 5. External NTC Thermistor Network

4010 F05

Temperature sensing is optional in LTC4010 applications. battery from a severe overcharge.

figures strictly for reference only. no external temperature information is available. charge termination parameter set. under normal operating conditions. Figure 6. Minimum LTC4010 Application

4010 F06

state is monitored on the three LTC4010 status outputs. Charging of NiMH batteries is selected in this example. However, NiCd parameters could be chosen as well. battery continues to power the system during charging. from any type of post regulator operating from the battery. from the load with a rectifier or switch during charging. of the P-channel MOSFET in this application. by the LTC4010 during a typical charge cycle. Figure 7. Full-Featured 2A LTC4010 Application

4010 F07

Figure 9. Charging Waveforms Example Figure 8. LTC4010 with MCU Interface

4010 F08

4010 F09

when the LTC4010 completes charge qualification. starts a precharge cycle because VCELL is less than 900mV. bring the average cell voltage to 900mV. be an increase of 1°C per minute. minutes with the CHRG output continuously asserted. from the battery in the absence of an input power source. turned to an acceptable range. and providing temperature information. Figure 10. NiCd Battery Pack with Time Limit Control

4010 F10

Figure 11. NiMH Battery Pack Indicating Number of Cells

4010 F11

Figure 12. For maximum efficiency, the switch node rise out the PCB using this specific order.

  1. Input capacitors should be placed as close as possible
  2. Place the LTC4010 close to the switching FET gate

opposite side of the PCB from the switching FETs.

  1. Place the inductor input as close as possible to the

needed to support the programmed charge current.

  1. Place the charge current sense resistor immediately

current sense traces to the LTC4010 are not long. not at the sense resistor location.

  1. Place output capacitors next to the sense resisitor
  2. Output capacitor ground connections must feed into

ground before tying back into system ground.

  1. Connection of switching ground to system ground, or

point to make the connection.

  1. Route analog ground as a trace tied back to the

analog ground to system ground.

  1. A good rule of thumb for via count in a given high
  2. If possible, place all the parts listed above on the same
  3. Copper fills or pours are good for all power connec-

inductance, which further improves EMI performance.

  1. For best current programming accuracy, provide a

See Figure 13 for an example.

  1. It is important to minimize parasitic capacitance on

Information furnished by Linear Technology Corporation is believed to be accurate and reliable. tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

0.65 BSC

  1. CONTROLLING DIMENSION: MILLIMETERS
  2. RECOMMENDED MINIMUM PCB METAL SIZE

Figure 13. Kelvin Sensing of Charge CurrentFigure 12. High Speed Switching Path

4010 F12

4010 F13

© LINEAR TECHNOLOGY CORPORATION 2005 LT/TP 0205 1K • PRINTED IN THE USA PART NUMBER DESCRIPTION COMMENTS LT 1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.5A Charge Current for Li-Ion, NiCd and NiMH Batteries LT1511 3A Constant-Voltage/Constant-Current Battery Charger High Efficiency, Minimum External Components to Fast Charge Lithium, NiMH and NiCd Batteries LT1513 SEPIC Constant- or Programmable-Current/Constant- Charger Input Voltage May be Higher, Equal to or Lower Than Voltage Battery Charger Battery Voltage, 500kHz Switching Frequency LTC1760 Smart Battery System Manager Autonomous Power Management and Battery Charging for Two Smart Batteries, SMBus Rev 1.1 Compliant LTC1960 Dual Battery Charger/Selector with SPI 11-Bit V-DAC, 0.8% Voltage Accuracy, 10-Bit I-DAC, 5% Current Accuracy LTC4008 High Efficiency, Programmable Voltage/Current Battery Constant-Current/Constant-Voltage Switching Regulator, Resistor Charger Voltage/Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator Outputs LTC4011 High Efficiency Standalone Nickel Battery Charger Complete NiMH/NiCd Charger in a 20-Pin TSSOP Package, PowerPath TM Contol, Constant-Current Switching Regulator LTC4060 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 LTC4100 Smart Battery Charger Controller Level 2 Charger Operates with or without MCU Host, SMBus Rev. 1.1 Compliant LTC4150 Coulomb Counter/Battery Gas Gauge High Side Sense of Charge Quantity and Polarity in a 10-Pin MSOP LTC4412 Low Loss PowerPath Controller Very Low Loss Replacement for Power Supply ORing Diodes Using Minimal External Components LTC4413 Dual, 2.6A Ideal Diode in 3mm × 3mm DFN 2.5V ≤ VIN ≤ 5.5V, Ideal Diode ORing or Load Sharing, Low Reverse Leakage Current PowerPath is a trademark of Linear Technology Corporation. RELATED PARTS Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com