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LTC4060

4060f

Standalone Linear NiMH/NiCd

Fast Battery Charger

■

Complete Fast Charger Controller for Single,

2-, 3- or 4-Series Cell NiMH/NiCd Batteries

■

No Firmware or Microcontroller Required

■

Termination by –∆V, Maximum Voltage or

Maximum Time

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No Sense Resistor or Blocking Diode Required

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Automatic Recharge Keeps Batteries Charged

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Programmable Fast Charge Current: 0.4A to 2A

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Accurate Charge Current: ±5% at 2A

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Fast Charge Current Programmable Beyond 2A with

External Sense Resistor

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Automatic Detection of Battery

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Precharge for Heavily Discharged Batteries

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Optional Temperature Qualified Charging

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Charge and AC Present Status Outputs Can Drive LED

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Automatic Sleep Mode with Input Supply Removal

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Negligible Battery Drain in Sleep Mode: <1µA

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Manual Shutdown

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Input Supply Range: 4.5V to 10V

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Available in 16-Lead DFN and TSSOP Packages

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Portable Computers, Cellular Phones and PDAs

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Medical Equipment

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Charging Docks and Cradles

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Portable Consumer Electronics

, LTC and LT are registered trademarks of Linear Technology Corporation.

2-Cell, 2A Standalone NiMH Fast Charger with

Optional Thermistor and Charge Indicator

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

The LTC

4060 is a complete fast charging system for NiMH

or NiCd batteries. Just a few external components are

needed to design a standalone linear charging system.

An external PNP transistor provides charge current that is

user programmable with a resistor. A small external capaci-

tor sets the maximum charge time. No external current

sense resistor is needed, and no blocking diode is required.

The IC automatically senses the DC input supply and bat-

tery insertion or removal. Heavily discharged batteries are

initially charged at a C/5 rate before a fast charge is applied.

Fast charge is terminated using the –∆V detection method.

Backup termination consists of a programmable timer and

battery overvoltage detector. An optional external NTC ther-

mistor can be used for temperature-based qualification of

charging. An optional programmable recharge feature au-

tomatically recharges batteries after discharge.

Manual shutdown is accomplished with the SHDN pin, while

removing input power automatically puts the LTC4060 into

sleep mode. During shutdown or sleep mode, battery drain

is <1µA.

The LTC4060 is available in both low profile (0.75mm) 16-

pin 5mm × 3mm DFN and 16-lead TSSOP packages. Both

feature exposed metal die mount pads for optimum ther-

mal performance.

2-Cell NiMH Charging Profile

LTC4060

GND

SHDN

CHRG

NTC

PROG

ARCT

SEL0

SEL1

ACP

SENSE

DRIVE

BAT

TIMER

CHEM

PAUSE

330Ω

698Ω

NTC

1.5nF

4060 TA01

NiMH

BATTERY

“CHARGE”

CHARGE TIME (MINUTES)

3.10

BATTERY VOLTAGE (V)

3.20

3.30

3.40

10 20 30 40

4060 TA01b

–∆V

TERMINATION

Summary of content (20 pages)

PAGE 1
LTC4060 Standalone Linear NiMH/NiCd Fast Battery Charger U FEATURES DESCRIPTIO ■ The LTC®4060 is a complete fast charging system for NiMH or NiCd batteries. Just a few external components are needed to design a standalone linear charging system.
PAGE 2
LTC4060 W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) VCC to GND ............................................... –0.3V to 11V Input Voltage SHDN, NTC, SEL0, SEL1, PROG, ARCT, BAT, CHEM, TIMER, PAUSE ...... –0.3V to VCC + 0.3V Output Voltage CHRG, ACP, DRIVE ................... –0.3V to VCC + 0.3V Output Current (SENSE) ...................................... –2.2A Short-Circuit Duration (DRIVE) ...................... Indefinite Operating Ambient Temperature Range (Note 2) ..................................
PAGE 3
LTC4060 ELECTRICAL CHARACTERISTICS The ● indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VBAT = 2.8V, GND = 0V unless otherwise specified. All currents into the device pins are positive and all currents out of the device pins are negative. All voltages are referenced to GND unless otherwise specified.
PAGE 4
LTC4060 ELECTRICAL CHARACTERISTICS The ● indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VBAT = 2.8V, GND = 0V unless otherwise specified. All currents into the device pins are positive and all currents out of the device pins are negative. All voltages are referenced to GND unless otherwise specified.
PAGE 5
LTC4060 U W TYPICAL PERFOR A CE CHARACTERISTICS NiMH Battery Charging Characteristics at 1C Rate 1.70 NiCd Battery Charging Characteristics at 1C Rate 1.7 TA = 25°C NiMH Battery Charging Characteristics at C/2 Rate 1.60 TA = 25°C –∆V TERMINATION –∆V TERMINATION 1.55 1.65 1.60 CELL VOTLAGE (V) CELL VOLTAGE (V) –∆V TERMINATION CELL VOLTAGE (V) TA = 25°C 1.6 1.5 1.50 1.45 1.40 1.55 1.35 1.
PAGE 6
LTC4060 U U U PI FU CTIO S DRIVE (Pin 1): Base Drive Output for the External PNP Pass Transistor. Provides a controlled sink current that drives the base of the PNP. This pin has current limit protection for the LTC4060. BAT (Pin 2): Battery Voltage Sense Input Pin. The LTC4060 uses the voltage on this pin to monitor battery voltage and control the battery current during charging.
PAGE 7
LTC4060 W BLOCK DIAGRA 14 VCC VOLTAGE REFERENCE UVLO R1 31.5Ω I I/5 IOSC 1.5V CURRENT DIVIDER SEL0 SEL1 R2 0.
PAGE 8
LTC4060 U OPERATIO The LTC4060 is a complete linear fast charging system for NiMH or NiCd batteries. Operation can be understood by referring to the Block Diagram, State Diagram (Figure 1) and application circuit (Figure 2). While in the unpowered sleep mode, the battery is disconnected from any internal loading. The sleep mode is exited and the shutdown mode is entered when VCC rises above the UVLO (Undervoltage Lock Out) exit threshold.
PAGE 9
LTC4060 U OPERATIO The charge current is set with an external current programming resistor connected between the PROG pin and GND. In the Block Diagram, amplifier A1 will cause a virtual 1.5V to appear on the PROG pin and thus, all of the programming resistor’s current will flow through the N-channel FET to the current divider.
PAGE 10
LTC4060 U OPERATIO applied to the SHDN pin, shutdown ends and charge qualification is entered. If the internal die temperature becomes excessive, charging stops and the part enters the shutdown state. Once in the shutdown state charge qualification can be reinitiated only when the die temperature drops to normal and then by removing and replacing the battery or toggling the SHDN pin low to high or removing and reapplying power to the charger.
PAGE 11
LTC4060 U OPERATIO charging begins at the maximum current set by the external programming resistor connected between the PROG pin and GND. If an external thermistor indicates sensed temperature is beyond a range of 5°C to 55°C charging is suspended, the charge timer is paused and the CHRG status output remains low. Normal charging resumes from the previous state when the sensed temperature rises above 5°C or falls below 45°C. Voltage-based termination (–∆V) is then reset and immediately enabled.
PAGE 12
LTC4060 U OPERATIO Battery Chemistry Selection Insertion and Removal of Batteries The desired battery chemistry is selected by programming the CHEM pin to the proper voltage. When wired to GND, a set of parameters specific to charging NiMH cells is selected. When CHEM is connected to VCC, charging is optimized for NiCd cells. The various charging parameters are detailed in Table 2. The LTC4060 automatically senses the insertion or removal of a battery by monitoring the VCELL pin voltage.
PAGE 13
LTC4060 U W U U APPLICATIO S I FOR ATIO resistor to the PROG pin can also be used to program current. Note that this will alter the timer periods unless alternate TIMER pin capacitors are also programmed through an analog switch. The PROG pin provides a reference voltage of 1.5V (VPROG) that may be tapped for system use. Current loading on PROG is multiplied by 930 and appears as increased IMAX. This may be compensated by adjustment of RPROG. Total PROG pin current must be limited to 2.
PAGE 14
LTC4060 U W U U APPLICATIO S I FOR ATIO temperature) at approximately 0°C (5°C – 5°C hysteresis at VCC = 5V) and then resume when the thermistor falls below 27k (rising temperature) which will be approximately 5°C (VNTC = VCLD = 0.86 • VCC typ). Many thermistors with an RCOLD to RHOT ratio of approximately 7 will work. For lower power dissipation higher values of thermistor resistance can be used. The Murata NTH4G series offers resistances of up to 100k at 25°C.
PAGE 15
LTC4060 U W U U APPLICATIO S I FOR ATIO charging (the DRIVE pin is internally switched to the BAT pin). Most transistors will meet this requirement as well. With low supply voltages, the PNP saturation voltage (VCESAT) becomes important. The VCESAT must be less than the minimum supply voltage minus the maximum voltage drop across the internal current sense resistor and bond wires (approximately 0.08Ω) and maximum battery voltage presented to the charger accounting for wire I • R drops.
PAGE 16
LTC4060 U TYPICAL APPLICATIO S Full Featured 2A Charger Application Power Path Control Figure 2 shows an application that utilizes the optional temperature sensing and optional externally programmable automatic recharge features. It also has LEDs to indicate charging status and the presence of sufficient input supply voltage. Proper power path control is an important consideration when fast charging nickel cells.
PAGE 17
LTC4060 U TYPICAL APPLICATIO S Trickle Charge resistance and mismatches in the two sense resistor’s value will cause charge current variability to increase in proportion to the extension in current. Resistor RISET should be connected directly to the LTC4060 to reduce errors. The total current sense resistor, bond wire and lead frame resistance is approximately 0.08Ω (T.C. ≅ 3500ppm/ °C).
PAGE 18
LTC4060 U TYPICAL APPLICATIO S Reverse Input Voltage Protection In some applications protection from reverse supply voltage is desired. If the supply voltage is high enough, a series blocking diode can be used. In other cases, where the voltage drop must be kept very low, a P-channel FET as shown in Figure 6 can be used. * VIN 14 LTC4060 VCC 4060 F06 *DRAIN BULK DIODE OF MOSFET Figure 6.
PAGE 19
LTC4060 U PACKAGE DESCRIPTIO DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 0.65 ±0.05 3.50 ±0.05 1.65 ±0.05 2.20 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 3.00 ±0.10 (2 SIDES) 9 0.40 ± 0.10 16 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHC16) DFN 1103 8 0.200 REF 1 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 4.40 ±0.
PAGE 20
LTC4060 U PACKAGE DESCRIPTIO FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BC 4.90 – 5.10* (.193 – .201) 3.58 (.141) 3.58 (.141) 16 1514 13 12 1110 6.60 ±0.10 9 2.94 (.116) 4.50 ±0.10 6.40 2.94 (.252) (.116) BSC SEE NOTE 4 0.45 ±0.05 1.05 ±0.10 0.65 BSC 1 2 3 4 5 6 7 8 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.25 REF 1.10 (.0433) MAX 0° – 8° 0.65 (.0256) BSC 0.50 – 0.75 (.020 – .030) NOTE: 1.