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LTC4011

4011fa

High Efficiency Standalone

Nickel Battery Charger

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Complete NiMH/NiCd Charger for 1 to 16 Cells

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No Microcontroller or Firmware Required

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550kHz Synchronous PWM Current Source Controller

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No Audible Noise with Ceramic Capacitors

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PowerPath

Control Support

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Programmable Charge Current: 5% Accuracy

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Wide Input Voltage Range: 4.5V to 34V

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Automatic Trickle Precharge

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–∆V Fast Charge Termination

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Optional ∆T/∆t Fast Charge Termination

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Automatic NiMH Top-Off Charge

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Programmable Timer

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Automatic Recharge

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Multiple Status Outputs

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Micropower Shutdown

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20-Lead Thermally Enhanced TSSOP Package

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Integrated or Standalone Battery Charger

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Portable Instruments or Consumer Products

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Battery-Powered Diagnostics and Control

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Back-Up Battery Management

The LTC

4011 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 LTC4011 automatically senses the presence of a DC

adapter and battery insertion or removal. Heavily dis-

charged batteries are precharged with a trickle current.

The LTC4011 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 automati-

cally 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 LTC4011 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.

Integrated PowerPath control support ensures that the

system remains powered at all times without allowing load

transients to adversely affect charge termination.

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

2A NiMH Battery Charger

2A NiMH Charge Cycle at 1C

, 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.

Summary of content (24 pages)

PAGE 1
LTC4011 High Efficiency Standalone Nickel Battery Charger U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Complete NiMH/NiCd Charger for 1 to 16 Cells No Microcontroller or Firmware Required 550kHz Synchronous PWM Current Source Controller No Audible Noise with Ceramic Capacitors PowerPathTM Control Support Programmable Charge Current: 5% Accuracy Wide Input Voltage Range: 4.
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LTC4011 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) VCC (Input Supply) to GND ....................... –0.3V to 36V DCIN to GND ............................................ –0.3V to 36V FAULT, CHRG, VCELL, VCDIV, SENSE, BAT, TOC or READY to GND .......................... –0.3V to VCC + 0.3V SENSE to BAT ...................................................... ±0.3V CHEM, VTEMP or TIMER to GND .............. –0.3V to 3.5V PGND to GND .......................................
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LTC4011 ELECTRICAL CHARACTERISTICS 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 PWM Current Source VFS BAT – SENSE Full-Scale Regulation Voltage (Fast Charge) 0.3V < BAT < VCC – 0.3V (Note 5) BAT = 4.8V ● 95 95 100 100 105 105 mV mV VPC BAT – SENSE Precharge Regulation Voltage 0.3V < BAT < VCC – 0.
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LTC4011 ELECTRICAL CHARACTERISTICS 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 Charger Timing ∆tTIMER Internal Time Base Error ● –10 10 % ∆tMAX Programmable Timer Error RTIMER = 49.
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LTC4011 U W TYPICAL PERFOR A CE CHARACTERISTICS NiCd Charge Cycle at 1C NiMH Charge Cycle at 0.
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LTC4011 U W TYPICAL PERFOR A CE CHARACTERISTICS Programmable Timer Accuracy Charger Efficiency at IOUT = 2A Fast Charge Current Output Regulation Charge Current Accuracy Charger Soft-Start INFET Forward Regulation Voltage PWM Switching Frequency Fast Charge Current Line Regulation INFET OFF Delay 4011fa 6
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LTC4011 U W TYPICAL PERFOR A CE CHARACTERISTICS PowerPath Switching Shutdown Quiescent Current PWM Input Bias (OFF) Undervoltage Lockout Threshold Voltage Shutdown Threshold Voltage (DCIN – VCC) Charge Enable Threshold Voltage (VCC – BAT) Thermistor Disable Threshold Voltage Pause Threshold Voltage 4011fa 7
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LTC4011 U W TYPICAL PERFOR A CE CHARACTERISTICS INTVDD Voltage INTVDD Short-Circuit Current U U U PI FU CTIO S DCIN (Pin 1): DC Power Sense Input. The LTC4011 senses voltage on this pin to determine when an external DC power source is present. This input should be isolated from VCC by a blocking diode or PowerPath FET. Refer to the Applications Information section for complete details. Operating voltage range is GND to 34V. FAULT (Pin 2): Active-Low Fault Indicator Output.
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LTC4011 U U U PI FU CTIO S VCDIV (Pin 9): Average Cell Voltage Resistor Divider Termination. The LTC4011 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 10): 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.
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LTC4011 W BLOCK DIAGRA 1 2 3 4 7 8 FET DIODE FAULT READY CHRG VCC UVLO AND SHUTDOWN CHEM 5 GND 6 INFET DCIN TGATE THERMISTOR INTERFACE PGND VRT VTEMP VCELL A/D CONVERTER CHARGER STATE CONTROL LOGIC BGATE PWM BAT SENSE 20 19 18 17 16 15 12 11 BATTERY DETECTOR 9 10 VCDIV TIMER INTVDD VOLTAGE REGULATOR TOC CHARGE TIMER VOLTAGE REFERENCE 14 13 INTERNAL VOLTAGE REGULATOR 4011 BD U OPERATIO Figure 1.
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LTC4011 U OPERATIO (Refer to Figure 1) Shutdown State The LTC4011 remains in micropower shutdown until DCIN (Pin 1) is driven above VCC (Pin 18). In shutdown all status and PWM outputs and internally generated terminations or supply voltages are inactive. Current consumption from VCC and BAT is reduced to a very low level. internal thermal limit, charging is suspended, the charge timer is paused and the LTC4011 indicates a fault condition.
PAGE 12
LTC4011 U OPERATIO 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 expired, the LTC4011 enters the top-off charge state. Top-off charge is implemented by sourcing one-tenth the programmed charge current for tMAX/3 minutes to ensure that 100% charge has been delivered to the battery. The CHRG and TOC status outputs are active during the top-off state.
PAGE 13
LTC4011 U OPERATIO PWM Current Source Controller An integral part of the LTC4011 is the PWM current source controller. The charger uses a synchronous step-down architecture to produce high efficiency and limited thermal dissipation. The nominal operating frequency of 550kHz allows use of a smaller external filter components. The TGATE and BGATE outputs have internally clamped voltage swings.
PAGE 14
LTC4011 U W U U APPLICATIO S I FOR ATIO External DC Source The external DC power source should be connected to the charging system and the VCC pin through either a power diode or P-channel MOSFET. This prevents catastrophic system damage in the event of an input short to ground or reverse-voltage polarity at the DC input. The LTC4011 automatically senses when this input is present. The opencircuit voltage of the DC source should be between 4.5V and 34V, depending on the number of cells being charged.
PAGE 15
LTC4011 U W U U APPLICATIO S I FOR ATIO Table 2. LTC4011 Charging Parameters STATE CHEM PIN BAT CHEMISTRY TIMER PC FC TMIN TMAX ICHRG TERMINATION CONDITION Both tMAX/12 5°C 45°C IPROG/5 Open NiCd tMAX 5°C 60°C IPROG Timer Expires –20mV per Cell or 2°C/Minute GND NiMH tMAX 5°C 60°C IPROG 1.5°C/Minute for First tMAX/12 Minutes if Initial VCELL < 1.325V –10mV per Cell or 1°C/Minute After tMAX/12 Minutes or if Initial VCELL > 1.
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LTC4011 U W U U APPLICATIO S I FOR ATIO 12 9 8 BAT VCDIV 1 CELL 10k 10k VCELL 33nF 4011 F04 Figure 4. Single-Cell Monitor Network The LTC4011 is designed to work best with a 5% 10K NTC thermistor with a β near 3750, such as the Siemens/ EPCOS B57620C103J062. In this case, the values for the external network are given by: R1 = 9.76k R2 = 28k R3 = 0Ω However, the LTC4011 will operate with other NTC thermistors having different nominal values or exponential temperature coefficients.
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LTC4011 U W U U APPLICATIO S I FOR ATIO greatly increase internal power dissipation at elevated VCC voltages. A minimum ceramic bypass capacitor of 0.1µF is recommended. Calculating Average Power Dissipation The user should ensure that the maximum rated IC junction temperature is not exceeded under all operating conditions. The thermal resistance of the LTC4011 package (θJA) is 38°C/W, provided the exposed metal pad is properly soldered to the PCB.
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LTC4011 U W U U APPLICATIO S I FOR ATIO Figure 6. Minimum 1A LTC4011 Application Figure 7. 3A NiMH Charger with Full PowerPath Control and installed battery, while a pair of red LEDs indicates charging. A yellow LED indicates fault conditions. The grounded CHEM pin selects the NiMH charge termination parameter set. While the LTC4011 is a complete, standalone solution, Figure 9 shows that it can also be interfaced to a host microprocessor.
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LTC4011 U W U U APPLICATIO S I FOR ATIO Figure 8. Full-Featured 2A LTC4011 Application Figure 9.
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LTC4011 U W U U APPLICATIO S I FOR ATIO Unlike all of the other applications discussed so far, the battery continues to power the system during charging. The MCU could be powered directly from the battery or from any type of post regulator operating from the battery. In this configuration, the LTC4011 relies expressly on the ability of the host MCU to know when load transients will be encountered.
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LTC4011 U W U U APPLICATIO S I FOR ATIO Figure 10. Charging Waveforms Example TIMER CHEM VTEMP 10 4 7 NC 66.5k + 10k NTC BATTERY PACK 1200mAhr NiCd CELLS – CHEM VTEMP VCELL 4 7 8 10k NTC + R2 BATTERY PACK 1500mAhr NiMH CELLS 4011 F11 – 4011 F12 Figure 11. NiCd Battery Pack with Time Limit Control Figure 12. NiMH Battery Pack Indicating Number of Cells cells.
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LTC4011 U W U U APPLICATIO S I FOR ATIO FETs must be on the same layer of copper as the input capacitors. Vias should not be used to make these connections. 2. Place the LTC4011 close to the switching FET gate terminals, keeping the connecting traces short to produce clean drive signals. This rule also applies to IC supply and ground pins that connect to the switching FET source pins. The IC can be placed on the opposite side of the PCB from the switching FETs. 3.
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LTC4011 U PACKAGE DESCRIPTIO FE Package 20-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation CB 6.40 – 6.60* (.252 – .260) 3.86 (.152) 3.86 (.152) 20 1918 17 16 15 14 13 12 11 6.60 ±0.10 2.74 (.108) 4.50 ±0.10 6.40 2.74 (.252) (.108) BSC SEE NOTE 4 0.45 ±0.05 1.05 ±0.10 0.65 BSC 1 2 3 4 5 6 7 8 9 10 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.25 REF 0.50 – 0.75 (.020 – .030) NOTE: 1.
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LTC4011 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT 1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.