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LTC4011

4011fb

Typical applicaTion

FeaTures DescripTion

High Efﬁciency Standalone

Nickel Battery Charger

applicaTions

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

PowerPath™ Control Support

Programmable Charge Current: 5% Accuracy

Wide Input Voltage Range: 4.5V to 34V

Automatic Trickle Precharge

–∆V Fast Charge Termination

Optional ∆T/∆t Fast Charge Termination

Automatic NiMH Top-Off Charge

Programmable Timer

Automatic Recharge

Multiple Status Outputs

Micropower Shutdown

20-Lead Thermally Enhanced TSSOP Package

Integrated or Standalone Battery Charger

Portable Instruments or Consumer Products

Battery-Powered Diagnostics and Control

Back-Up Battery Management

L, LT, LTC, LTM, Linear Technology and the Linear logo 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.

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

discharged batteries are precharged with a trickle cur

rent. 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

automatically applied to NiMH batteries after fast charg

ing 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 temperature

limits. NiMH or NiCd fast charge termination parameters

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.

2A NiMH Battery Charger

2A NiMH Charge Cycle at 1C

0.1µF

10µF

4.7µH

10µF

0.033µF 0.068µF

FAULT

INFET

CHRG

FROM

ADAPTER

TOC

READY

Summary of content (26 pages)

PAGE 1
LTC4011 High Efficiency Standalone Nickel Battery Charger Features n n n n n n n n n n n n n n n n Description 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 PowerPath™ Control Support Programmable Charge Current: 5% Accuracy Wide Input Voltage Range: 4.
PAGE 2
LTC4011 Absolute Maximum Ratings Pin Configuration (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..........................................................±0.
PAGE 3
LTC4011 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. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 3.075 3 3.3 l 3.525 3.6 V V l –9 Thermistor Termination VRT Output Voltage IRT Short-Circuit Current RL = 10k VRT = 0V –1 mA PWM Current Source VFS BAT – SENSE Full-Scale Regulation Voltage (Fast Charge) 0.
PAGE 4
LTC4011 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. SYMBOL PARAMETER CONDITIONS TMAXC Maximum Fast Charge Temperature (Note 8) VTEMP Decreasing, Fast Charge MIN TYP MAX l 57 60 63 VTEMP(D) VTEMP(P) UNITS °C VTEMP Disable Threshold Voltage l 2.8 3.
PAGE 5
LTC4011 Typical Performance Characteristics NiCd Charge Cycle at 1C NiMH Charge Cycle at 0.
PAGE 6
LTC4011 Typical Performance 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 Time 4011fb
PAGE 7
LTC4011 Typical Performance Characteristics PowerPath Switching PWM Input Bias Current (OFF) CURRENT (µA) CURRENT (µA) Shutdown Quiescent Current 100µs/DIV Undervoltage Lockout Threshold Voltage Thermistor Disable Threshold Voltage Shutdown Threshold Voltage (DCIN – VCC) Charge Enable Threshold Voltage (VCC – BAT) Pause Threshold Voltage 4011fb
PAGE 8
LTC4011 Typical Performance Characteristics INTVDD Voltage INTVDD Short-Circuit Current Pin Functions 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.
PAGE 9
LTC4011 Pin Functions 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.
PAGE 10
LTC4011 Block Diagram 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 INTERNAL VOLTAGE REGULATOR 14 13 4011 BD 4011fb 10
PAGE 11
LTC4011 Operation Figure 1.
PAGE 12
LTC4011 Operation (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.
PAGE 13
LTC4011 Operation 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 14
LTC4011 Operation 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 15
LTC4011 Applications Information External DC Source Battery Chemistry Selection 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 open-circuit voltage of the DC source should be between 4.
PAGE 16
LTC4011 Applications Information Table 2. LTC4011 Charging Parameters STATE CHEM PIN BAT CHEMISTRY TIMER TMIN TMAX ICHRG Both tMAX/12 5°C 45°C IPROG/5 PC FC TERMINATION CONDITION Timer Expires Open NiCd tMAX 5°C 60°C IPROG –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.
PAGE 17
LTC4011 Applications Information is recommended for rejecting PWM switching noise. The value of C1 should be chosen to yield a 1st order lowpass frequency of less than 500Hz. In the case of a single cell, the external application circuit shown in Figure 4 is recommended to provide the necessary noise filtering and missing battery detection. Thermistor Network Design The network for proper temperature sensing using a thermistor with a negative temperature coefficient (NTC) is shown in Figure 5.
PAGE 18
LTC4011 Applications Information operations. However, this practice is not recommended for NiMH cells charged well above or below their 1C rate, because fast charge termination based solely on voltage inflection may not be adequate to protect the battery from a severe overcharge. A resistor between 10k and 20k may be used to connect VTEMP to VRT if the pause function is still desired.
PAGE 19
LTC4011 Applications Information FROM ADAPTER 12V 10µF INFET FAULT CHRG TOC READY 10µH 10µF 0.1µF Figure 6. Minimum 1A LTC4011 Application FROM ADAPTER 12V 20µF FAULT CHRG TOC READY 4.7µH 20µF 0.1µF 0.033µF 0.068µF Figure 7. 3A NiMH Charger with Full PowerPath Control A full-featured 2A LTC4011 application is shown in Figure 8. FET-based PowerPath allows for maximum input voltage range from the DC adapter.
PAGE 20
LTC4011 Applications Information While the LTC4011 is a complete, standalone solution, Figure 9 shows that it can also be interfaced to a host microprocessor. The host MCU can control the charger directly with an open-drain I/O port connected to the VTEMP pin, if that port is low leakage and can tolerate at least 2V. The charger state is monitored on the four LTC4011 status outputs. Charging of NiMH batteries is selected in this example. However, NiCd (CHEM → VRT) parameters could be chosen as well.
PAGE 21
LTC4011 Applications Information 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.
PAGE 22
LTC4011 Applications Information READY (PAUSE) CHRG TOC 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 4011 F11 Figure 11. NiCd Battery Pack with Time Limit Control A second possibility is to configure an LTC4011-based charger to accept battery packs with varying numbers of cells.
PAGE 23
LTC4011 Applications Information 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. Place the inductor input as close as possible to the drain of the switching FETs.
PAGE 24
LTC4011 Package Description 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.
PAGE 25
LTC4011 Revision History (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 01/10 Changes to Typical Application 1 Updated Order Information Section 2 Changes to Electrical Characteristics 2, 3, 4 Changes to Operation Section 12, 13, 14 Changes to Applications Information 15, 16, 19, 21, 22 Changes to Figures 6, 7, 8, 9 19, 20 4011fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
PAGE 26
LTC4011 Related Parts PART NUMBER DESCRIPTION COMMENTS LT 1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.