LINEAR TECHNOLOGY LTC4060 Technical data

FEATURES

■

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

■

No Sense Resistor or Blocking Diode Required

■

Automatic Recharge Keeps Batteries Charged

■

Programmable Fast Charge Current: 0.4A to 2A

■

Accurate Charge Current: ±5% at 2A

■

Fast Charge Current Programmable Beyond 2A with
External Sense Resistor

■

Automatic Detection of Battery

■

Precharge for Heavily Discharged Batteries

■

Optional Temperature Qualified Charging

■

Charge and AC Present Status Outputs Can Drive LED

■

Automatic Sleep Mode with Input Supply Removal

■

Negligible Battery Drain in Sleep Mode: <1µA

■

Manual Shutdown

■

Input Supply Range: 4.5V to 10V

■

Available in 16-Lead DFN and TSSOP Packages

U

APPLICATIO S

■

Portable Computers, Cellular Phones and PDAs

■

Medical Equipment

■

Charging Docks and Cradles

■

Portable Consumer Electronics

LTC4060

Standalone Linear NiMH/NiCd

Fast Battery Charger

U

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.

An external PNP transistor provides charge current that is
user programmable with a resistor. A small external capaci­tor 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 bat­tery 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 ther­mistor can be used for temperature-based qualification of
charging. An optional programmable recharge feature au­tomatically 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) 16­pin 5mm × 3mm DFN and 16-lead TSSOP packages. Both
feature exposed metal die mount pads for optimum ther­mal performance.

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

TYPICAL APPLICATIO

2-Cell, 2A Standalone NiMH Fast Charger with

Optional Thermistor and Charge Indicator

330Ω

“CHARGE”

NTC

698Ω

SHDN

CHRG

NTC

PROG

ARCT

SEL0

SEL1

U

V

IN =

V

CC

SENSE

LTC4060

PAUSE

GND

5V

ACP

DRIVE

BAT

TIMER

CHEM

1.5nF

4060 TA01

+

NiMH
BATTERY

2-Cell NiMH Charging Profile

3.40

–∆V

TERMINATION

3.30

3.20

BATTERY VOLTAGE (V)

3.10
0

10 20 30 40

CHARGE TIME (MINUTES)

50

60

4060 TA01b

4060f

1

LTC4060

WW

W

U

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

U

W

U

PACKAGE/ORDER INFORMATION

TOP VIEW

DRIVE

1

BAT

2

SENSE

3

TIMER

4

SHDN

5

PAUSE

6

PROG

7

ARCT

8

DHC16 PACKAGE

16-LEAD (5mm × 3mm) PLASTIC DFN

T

= 125°C, θJA = 37°C/W

JMAX

EXPOSED PAD (PIN 17) IS GND

MUST BE SOLDERED TO PCB TO OBTAIN

= 37°C/W OTHERWISE θJA = 140°C

θ

JA

16

GND

15

CHRG

14

V

CC

ACP

13

17

CHEM

12

NTC

11

SEL1

10

SEL0

9

ORDER PART

NUMBER

LTC4060EDHC

DHC PART

MARKING

4060

Operating Ambient Temperature Range

(Note 2) ............................................. – 40°C to 85°C

Operating Junction Temperature (Note 3) ........... 125°C

Storage Temperature Range

TSSOP Package ............................... – 65°C to 150°C

DFN Package .................................... –65°C to 125°C

Lead Temperature (Soldering, 10 sec)

TSSOP Package ................................................ 300°C

TOP VIEW

1

DRIVE

2

BAT

3

SENSE

4

TIMER

SHDN

PAUSE

PROG

ARCT

16-LEAD PLASTIC TSSOP

T

JMAX

EXPOSED PAD (PIN 17) IS GND

MUST BE SOLDERED TO PCB TO OBTAIN

θJA = 37°C/W OTHERWISE θJA = 135°C

17

5

6

7

8

FE PACKAGE

= 125°C, θJA = 37°C/W

GND

16

CHRG

15

V

14

CC

ACP

13

CHEM

12

NTC

11

SEL1

10

SEL0

9

ORDER PART

NUMBER

LTC4060EFE

FE PART

MARKING

4060EFE

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, V

The ● indicates specifications which apply over the full operating

= 2.8V, GND = 0V unless otherwise specified. All

BAT

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.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VCC Supply

V

I

I

I

I

V

V

CC

SD

BSD

BSL

CC

UVI1

UVD1

Operating Voltage Range (Note 4) ● 4.50 10 V

VCC Supply Current (Note 9) I

= 2mA (R

PROG

PAUSE = V

CC

= 698Ω), 2.9 4.3 mA

PROG

VCC Supply Shutdown Current SHDN = 0V 250 325 µA

Battery Pin Leakage Current in Shutdown (Note 5) V

Battery Pin Leakage Current in Sleep (Note 6) VCC = 0V, V

= 2.8V, SHDN = 0V –1 0 1 µA

BAT

= 5.6V –1 0 1 µA

BAT

Undervoltage Lockout Exit Threshold SEL0 = 0, SEL1 = 0 and SEL0 = VCC, ● 4.25 4.36 4.47 V

SEL1 = 0, V

Increasing

CC

Undervoltage Lockout Entry Threshold SEL0 = 0, SEL1 = 0 and SEL0 = VCC, ● 4.15 4.26 4.37 V

SEL1 = 0, V

Decreasing

CC

4060f

2

LTC4060

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

The ● indicates specifications which apply over the full operating

= 25°C. VCC = 5V, V

A

= 2.8V, GND = 0V unless otherwise specified. All

BAT

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.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

UVI2

V

UVD2

V

UVI3

V

UVD3

V

UVH

Charging Performance

I

FCH

I

FCL

I

PCH

I

PCL

I

BRD

V

BR

V

BRH

V

BOV

V

BOVH

V

FCQ

V

FCQH

V

IDT

V

IDTH

V

MDV

V

PROG

V

ART

V

ARDT

V

ARH

V

ARDEF

V

ARDIS

I

ARL

V

CLD

V

CLDH

V

HTI

Undervoltage Lockout Exit Threshold SEL0 = 0, SEL1 = VCC, VCC Increasing ● 6.67 6.81 6.95 V

Undervoltage Lockout Entry Threshold SEL0 = 0, SEL1 = VCC, VCC Decreasing ● 6.57 6.71 6.85 V

Undervoltage Lockout Exit Threshold SEL0 = VCC, SEL1 = VCC, VCC Increasing ● 8.28 8.47 8.65 V

Undervoltage Lockout Entry Threshold SEL0 = VCC, SEL1 = VCC, VCC Decreasing ● 8.18 8.37 8.55 V

Undervoltage Lockout Hysteresis For All SEL0, SEL1 Options 100 mV

High Fast Charge Current (Notes 7, 10) R

Low Fast Charge Current (Note 7) R

High Precharge Current (Note 7) R

Low Precharge Current (Note 7) R

Battery Removal Detection Bias Current 4.5V < VCC < 10V, V

Battery Removal Threshold Voltage (Note 8) V

Battery Removal Threshold Hysteresis Voltage V

= 698Ω, 5V < VCC < 10V ● 1.9 2 2.1 A

PROG

= 3480Ω, 4.5V < VCC < 10V ● 0.35 0.4 0.45 A

PROG

= 698Ω, 4.5V < VCC < 10V 320 400 480 mA

PROG

= 3480Ω, 4.5V < VCC < 10V 40 80 120 mA

PROG

= VCC – 0.4V ● –450 –300 –160 µA

BAT

Increasing, 4.5V < VCC < 10V ● 1.95 2.05 2.15 V

CELL

Decreasing 50 mV

CELL

(Note 8)

Battery Overvoltage Threshold (Note 8) V

Battery Overvoltage Threshold Hysteresis (Note 8) V

Fast Charge Qualification Threshold Voltage V

Increasing, 4.5V < VCC < 10V ● 1.85 1.95 2.05 V

CELL

Decreasing 50 mV

CELL

Increasing, 4.5V < VCC < 10V 840 900 960 mV

CELL

(Note 8)

Fast Charge Qualification Threshold Hysteresis V

Decreasing 50 mV

CELL

Voltage (Note 8)

Initial Delay Hold-Off Threshold Voltage (Note 8) V

Initial Delay Hold-Off Threshold Hysteresis Voltage V

Increasing, 4.5V < VCC < 10V 1.24 1.3 1.36 V

CELL

Decreasing 50 mV

CELL

(Note 8)

–∆V Termination (Note 8) CHEM = VCC (NiCd) ● 11 16 21 mV

CHEM = 0V (NiMH)

Program Pin Voltage 4.5V < VCC < 10V, R

= 635Ω ● 1.45 1.5 1.54 V

PROG

● 5814mV

and 3480Ω

Automatic Recharge Programmed Threshold V
Voltage Accuracy (Note 8) 4.5V < V

Automatic Recharge Default Threshold Voltage V
Accuracy (Note 8) 4.5V < V

Automatic Recharge Threshold Voltage Hysteresis V

Decreasing, V

CELL

CELL

CELL

< 10V

CC

Decreasing, V

< 10V

CC

Increasing 50 mV

= 1.1V, ● 1.065 1.1 1.135 V

ARCT

= VCC, ● 1.235 1.3 1.365 V

ARCT

(Note 8)

Automatic Recharge Pin Default Enable Threshold V

CC

V

CC

Voltage – 0.8 – 0.2

Automatic Recharge Pin Disable Threshold 250 650 mV
Voltage

Automatic Recharge Pin Pull-Down Current V

NTC Pin Cold Threshold Voltage V

NTC Pin Cold Threshold Hysteresis Voltage V

NTC Pin Hot Charge Initiation Threshold Voltage V

= 1.3V ● 0.15 1.5 µA

ARCT

Decreasing, 4.5V < VCC < 10V ● 0.83 • 0.86 • 0.89 • V

NTC

Increasing 150 mV

NTC

Decreasing, 4.5V < VCC < 10V ● 0.47 • 0.5 • 0.53 • V

NTC

V

CC

V

CC

V

CC

V

CC

V

CC

V

CC

4060f

V

3

LTC4060

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

The ● indicates specifications which apply over the full operating

= 25°C. VCC = 5V, V

A

= 2.8V, GND = 0V unless otherwise specified. All

BAT

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.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

HTIH

V

HTC

V

HTCH

V

NDIS

I

NL

t

ACC

Output Drivers

I

DRV

R

DRV

V

OL

I

OH

Control Inputs

V

IT

V

ITH

I

IPD

I

IPU

NTC Pin Hot Charge Initiation Hysteresis Voltage V

NTC Pin Hot Charge Cutoff Threshold Voltage V

NTC Pin Hot Charge Cutoff Hysteresis Voltage V

Increasing 100 mV

NTC

Decreasing, 4.5V ≤ VCC ≤ 10V ● 0.37 • 0.4 • 0.43 • V

NTC

Increasing 100 mV

NTC

V

CC

V

CC

V

CC

NTC Pin Disable Threshold Voltage 25 250 mV

NTC Pin Pull-Down Current V

Timer Accuracy R

Drive Pin Sink Current V

Drive Pin Resistance to V

CC

ACP, CHRG Output Pins Low Voltage I

ACP, CHRG Output Pins High Leakage Current Outputs Inactive, V

= 2.5V ● 0.15 1.5 µA

NTC

= 698Ω, C

PROG

= 3480Ω, C

R

PROG

= 4V ● 40 70 120 mA

DRIVE

V

= 4V, Not Charging 4700 Ω

DRIVE

= I

ACP

= 10mA 0.8 V

CHRG

= 1.2nF and –15 0 15 %

TIMER

= 470pF

TIMER

= V

CHRG

ACP

= V

CC

–2 2 µA

SHDN, SEL0, SEL1, CHEM, PAUSE Pins Digital VCC = 10V 350 650 mV
Input Threshold Voltage

SHDN, SEL0, SEL1, CHEM, PAUSE Pins Digital 50 mV
Input Hysteresis Voltage

SHDN, SEL0, SEL1, CHEM Pins Digital Input VCC = 10V, VIN = V

CC

0.4 2 µA

Pull-Down Current

PAUSE Pin Digital Input Pull-Up Current VIN = GND –2 –0.4 µA

Note 1: Absolute Maximum Ratings only indicate limits for survivability.
Operating the device beyond these limits may result in permanent damage.
Continuous or extended application of these maximum levels may
adversely affect device reliability.

Note 2: The LTC4060 is guaranteed to meet performance specifications
from 0°C to 70°C ambient temperature range and 0°C to 85°C junction
temperature range. Specifications over the –40°C to 85°C operating
ambient temperature range are assured by design, characterization and
correlation with statistical process controls.

Note 3: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Overtempera­ture protection is activated at a temperature of approximately 145°C,
which is above the specified maximum operating junction temperature.
Continuous operation above the specified maximum operation temperature
may result in device degradation or failure. Operating junction temperature

(in °C) is calculated from the ambient temperature TA and the average

T

J

power dissipation P

TJ = TA + θ

Note 4: Short duration drops below the minimum V

(in watts) by the formula:

D

• P

JA

D

specification of

CC

several microseconds or less are ignored by the undervoltage detection
circuit.

Note 5: Assumes that the external PNP pass transistor has negligible B-C
reverse leakage current when the collector is biased at 2.8V (V
charged cells in series) and the base is biased at V

CC

.

BAT

for two

Note 6: Assumes that the external PNP pass transistor has negligible B-E
reverse leakage current when the emitter is biased at 0V (V
base is biased at 5.6V (V

for four charged cells in series).

BAT

) and the

CC

Note 7: The charge current specified is the regulated current through the
internal current sense resistor that flows into the external PNP pass
transistor’s emitter. Actual battery charging current is slightly less and
depends upon PNP alpha.

Note 8: Given as a per cell voltage (V

/Number of Cells).

BAT

Note 9: Supply current includes the current programming resistor current
of 2mA. The charger is paused and not charging the battery.

Note 10: The minimum V

supply is set at 5V during this test to

CC

compensate for voltage drops due to test socket contact resistance and 2A
of current. This ensures that the supply voltage delivered to the device
under test does not fall below the UVLO entry threshold. Specification at
the minimum V

of 4.5V is assured by design and characterization.

CC

4060f

4

UW

TEMPERATURE (°C)

–50

0.5

1.0

1.7

25 75

4060 G09

0

–0.5

–25 0

50 100 125

–1.0

–1.5

1.5

ERROR (%)

VCC = 10V

VCC = 4.5V

R

PROG

= 3480Ω

C

TIMER

= 470pF

R

PROG

= 698Ω

C

TIMER

= 1.2nF

TYPICAL PERFOR A CE CHARACTERISTICS

LTC4060

NiMH Battery Charging
Characteristics at 1C Rate

1.70
TA = 25°C

–∆V TERMINATION

1.65

1.60

CELL VOLTAGE (V)

1.55

0

10 20 30 40

CHARGE TIME (MINUTES)

NiCd Battery Charging
Characteristics at C/2 Rate

1.65

1.60

–∆V TERMINATION

1.55

1.50

CELL VOTLAGE (V)

1.45

NiCd Battery Charging
Characteristics at 1C Rate

1.7
TA = 25°C

–∆V TERMINATION

1.6

1.5

CELL VOLTAGE (V)

1.4
0

50

60

4060 G01

10 20 30 40

CHARGE TIME (MINUTES)

I

vs Temperature and

FCH

50

60

4060 G02

Supply Voltage

2.010

2.005

(A)

2.000

FCH

I

1.995

VCC = 10V

VCC = 4.5V

NiMH Battery Charging
Characteristics at C/2 Rate

1.60
TA = 25°C

1.55

1.50

1.45

CELL VOTLAGE (V)

1.40

1.35

020

I

–∆V TERMINATION

60

40

CHARGE TIME (MINUTES)

vs Temperature and

FCL

Supply Voltage

402

401

(mA)

400

FCL

I

399

80

VCC = 10V

VCC = 4.5V

100

120

140

4060 G03

1.40

–260

(µA)

–300

BRD

I

–340

020

–50

60

40

CHARGE TIME (MINUTES)

I

vs Temperature and

BRD

Supply Voltage

VCC = 10V

–25 0 25 50

TEMPERATURE (°C)

80

100

120

4060 G04

VCC = 4.5V

75 100 125

4060 G07

140

1.990
–50

–25 0 25 50

V

MDV

Supply Voltage

18

16

14

12

(mV)

MDV

10

V

8

6

4

–50

–25 0

TEMPERATURE (°C)

75 100 125

vs Temperature and

NiCd

4.5V ≤ V

4.5V ≤ V

TEMPERATURE (°C)

≤ 10V

CC

NiMH

≤ 10V

CC

50 100 125

25 75

4060 G05

4060 G08

398

–50

–25 0 25 50

t

vs Temperature and

ACC

Supply Voltage

TEMPERATURE (°C)

75 100 125

4060 G06

4060f

5

LTC4060

U

UU

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. An internal
resistor divider is connected to this pin which is discon­nected when in shutdown or when no power is applied to
VCC.

SENSE (Pin 3): Charge Current Sense Node Input. Current
from V
tor and reappears at the SENSE pin to supply current to the
external PNP emitter. The PNP collector provides charge
current directly to the battery.

TIMER (Pin 4): Charge Timer Input. A capacitor connected
between TIMER and GND along with a resistor connected
from PROG to GND programs the charge cycle timing
limits.

SHDN (Pin 5): Active Low Shutdown Control Logic Input.
When pulled low, charging stops and the LTC4060 supply
current is minimized.

PAUSE (Pin 6): Pause Enable Logic Input. The charger can
be paused, turning off the charge current, disabling termi­nation and stopping the timer when this pin is high. A low
level will resume the charging process.

PROG (Pin 7): Charge Current Programming Input. Pro­vides a virtual reference of 1.5V for an external resistor
(R

PROG

battery charge current. The fast charge current will be 930
times the current through this resistor. This voltage is also
usable as system voltage reference.

passes through the internal current sense resis-

CC

) tied between this pin and GND that programs the

SEL0, SEL1 (Pins 9, 10): Number of Cells Selection Logic
Input. For single cell, connect both pins to GND. For two
cells, connect SEL1 to GND and SEL0 to V
cells, SEL1 connects to V
cells, connect both pins to V

NTC (Pin 11): Battery Temperature Input. An external NTC
thermistor network may be connected to NTC to provide
temperature-based charge qualification. Connecting NTC
to GND inhibits this function.

CHEM (Pin 12): Battery Chemistry Selection Logic Input.
When connected to a high level NiCd fast charge –∆V
termination parameters are used. A low level selects NiMH
parameters.

ACP (Pin 13): Open-Drain Power Supply Status Output.
When V
old, the ACP pin will pull to ground. Otherwise the pin is
high impedance. This output is capable of driving an LED.

VCC (Pin 14): Power Input. This pin can be bypassed to
ground with a capacitance of 1µF.

CHRG (Pin 15): Open-Drain Charge Indicator Status Out­put. The LTC4060 indicates it is providing charge to the
battery by driving this pin to GND. If charging is paused or
suspended due to abnormal battery temperature, the pin
remains pulled to GND. Otherwise the pin is high imped­ance. This output can drive an LED.

GND (Pin 16): Ground. This pin provides a ground for the
internal voltage reference and other circuits. All voltage
thresholds are referenced to this pin.

Exposed Pad (Pin 17): Thermal Connection. Internally
connected to GND. Solder to PCB ground for optimum
thermal performance.

is greater than the undervoltage lockout thresh-

CC

and SEL0 to GND. For four

CC

.

CC

For three

CC.

ARCT (Pin 8): Autorecharge Threshold Programming
Input. When the average cell voltage falls below this
threshold, charging is reinitiated. The voltage on this pin
is conveniently derived by using two series PROG pin
resistors and connecting to their common. Connecting
ARCT to VCC invokes a default threshold of 1.3V. Connect­ing ARCT to GND inhibits autorecharge.

6

4060f

BLOCK DIAGRA

VOLTAGE

REFERENCE

1.5V

PROG

R

PROG

7

NTC

11

CHRG

15

ACP

13

SHDN

5

PAUSE

6

W

I

OSC

+

–

THERMISTOR

I

I/5

A1

INTERFACE

CURRENT

DIVIDER

I I/5

R1

31.5Ω

–

V

CC

COLD

HOT

CUTOFF

CHARGER STATE

CONTROL LOGIC

I

OSC

14

A2

V

CC

+

R2

0.03Ω

SUPPLY GOOD

OUTPUT DRIVER

CURRENT LIMIT

OVERTEMPERATURE

DETECT

AND

IC

UVLO

A/D

CONVERTER

BATTERY

DETECTOR

SEL0

SEL1

SENSE

DRIVE

I

BRD

BAT

LTC4060

3

1

2

+

GND
16, 17

12

CHEM

10

SEL1

SEL0

9

OSCILLATOR

TIMER

4

C

TIMER

AUTORECHARGE

DETECTOR

ARCT

8

4060 BD

4060f

7

LTC4060

OPERATIO

U

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. The UVLO thresholds are depen­dent upon the number of series cells programmed by the
SEL0 and SEL1 pins. When shutdown occurs the ACP pin
goes from a high to low impedance state. The shutdown
mode is exited and the charge qualification mode entered

SUPPLY

GOOD

LOW OR NO

SUPPLY

SLEEP

(ACP = 0)

when all of the following conditions are met: 1) there is no
manual shutdown command from SHDN, 2) the battery
overvoltage detector does not detect a battery overvolt­age, 3) the battery removal detector detects a battery in
place, 4) pause is inactive and 5) the IC’s junction tempera­ture is normal. Once in the charge qualification mode the
thermistor interface monitors an optional thermistor net­work to determine if the battery temperature is within
charging limits. If the temperature is found within limits
charging can begin. While charging, the CHRG pin pulls to
GND which can drive an LED.

MANUAL

SHUTDOWN

(SHDN = 0)

BATTERY REMOVED,

SHUTDOWN

BATTERY OVERVOLTAGE,
CHARGE PERIOD TIMED
OUT OR IC TOO HOT

< AUTORECHARGE

V

CELL

THRESHOLD

AUTOMATIC

RECHARGE

–∆V TERMINATION

ADEQUATE SUPPLY
AND CHARGER ENABLED

CHARGE

QUALIFICATION

BATTERY PRESENT AND
TEMPERATURE GOOD
(OPTIONAL)

PRECHARGE

/5)

(I

MAX

ADEQUATE V
TEMPERATURE GOOD
(OPTIONAL)

FAST CHARGE

)

(I

MAX

4060 F01

CELL

AND

8

Figure 1. LTC4060 Basic State Diagram

4060f

OPERATIO

LTC4060

U

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. The current divider is controlled
by the charger state control logic to produce a voltage
across R1, appropriate either for precharge (I/5) or for fast
charge (I), depending on the cell voltage. The current di­vider also produces a constant current I
with an external capacitor tied to the TIMER pin, sets the
Oscillator’s clock frequency. During charging, the external
PNP transistor’s collector will provide the battery charge
current. The PNP’s emitter current flows into the SENSE
pin and through the internal current sense resistor R2
(0.03Ω). This current is slightly more than the collector
current since it includes the base current. Amplifier A2 and
the output driver will drive the base of the external PNP
through the DRIVE pin to force the same reference voltage
that appears across R1 to appear across the R2. The pre­cision ratio between R1 and R2, along with the current
programming resistor, accurately determines the charge
current.

When charging begins, the charger state control logic will
enable precharge of the battery. When the cell voltage
exceeds the fast charge qualification threshold, fast charge
begins. If the cell voltage exceeds the initial delay hold off
threshold voltage just prior to precharge, then the A/D
converter immediately monitors for a –∆V event to
terminate charging while in fast charge. Otherwise, the
fast charge voltage stabilization hold off period must
expire before the A/D converter monitors for a –∆V event
from which to terminate charging. The –∆V magnitude for
termination is selected for either NiMH or NiCd by the
CHEM pin. Should the battery temperature become too hot
or too cold, charging will be suspended by the charger
state control logic until the temperature enters normal
limits. A termination timer puts the charger into shutdown
mode if the programmed time has expired. After charging
has ended, the optional autorecharge detector function
monitors for the battery voltage to drop to either a default
or externally programmed cell voltage before automati­cally restarting a charge cycle.

, that along

OSC

The SHDN pin can be used to return the charger to a
shutdown and reset state. The PAUSE pin can be used to
pause the charge current and internal clocks for any
interval desired.

Fault conditions, such as overheating of the IC due to
excessive PNP base current drive, are monitored and
limited by the IC overtemperature detection and output
driver and current limit blocks.

When either VCC is removed or manual shutdown is
entered, the charger will draw only tiny leakage currents
from the battery, thus maximizing standby time. With V
removed, the external PNP’s base is connected to the
battery by the charger. In manual shutdown, the base is
connected to VCC by the charger.

Undervoltage Lockout

An internal undervoltage lockout circuit (UVLO) monitors
the input voltage and keeps the charger in the inactive
sleep mode until VCC rises above the undervoltage exit
threshold. The ACP pin is high impedance while in the
sleep mode and becomes low impedance to ground when
in the active mode. The threshold is dependent upon the
number of series cells selected by the SEL0 and SEL1 pins
(see V
table). The UVLO circuit has a built-in hysteresis of 100mV.
The thresholds are chosen to provide a minimum voltage
drop of approximately 600mV between minimum V
BAT at a battery cell voltage of 1.8V. This helps to protect
against excessive saturation in the external power PNP
when the supply voltage is near its minimum. While
inactive the LTC4060 reduces battery current to just a
negligible leakage current (I

Manual Shutdown Control

The LTC4060 can be forced into a low quiescent current
shutdown while VCC is present by applying a low level to
the SHDN pin. In manual shutdown, charging is inhibited,
the internal timer is reset and oscillator disabled, CHRG
status output is high impedance and ACP continues to
provide the correct status. The LTC4060 will draw low cur­rent from the supply (ISD), and only a negligible leakage
current is applied to the battery (I

UVI1-3

and V

in the Electrical Characteristics

UVD1-3

).

BSL

). If a high level is

BSD

CC

CC

and

4060f

9

LTC4060

OPERATIO

U

applied to the SHDN pin, shutdown ends and charge quali­fication is entered.

Charge Qualification

After exiting the sleep or shutdown modes the LTC4060
will check for the presence of a battery and for proper
battery temperature (if a thermistor is used) before initiat­ing charging.

When V
a battery is assumed to be present. Should V
above 1.95V (V

CELL

(V

/Number of Cells) is below 2.05V (VBR),

BAT

) for a time greater than the battery

BOV

CELL

rise

overvoltage event delay shown in the far right column of
Table 1, then a battery overvoltage condition is detected
and charging stops. Once stopped in this way, qualifica­tion can be reinitiated after V
(V

BOV

– V

) only by removing and replacing the battery

BOVH

has fallen below 1.9V

CELL

(or replacing the battery if the overvoltage condition is a
result of battery removal), toggling the SHDN pin low to
high or removing and reapplying power to the charger.

If the NTC pin voltage is above the temperature disable
threshold (V

), the LTC4060 verifies that the ther-

NDIS

mistor temperature is between 5°C and 45°C. Charging
will not initiate until these temperature limits are met.

The LTC4060 continues to qualify important voltage and
temperature parameters during all charging states. If V

CC

drops below the undervoltage lockout threshold, sleep
mode 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.

Precharge

The state that is entered when qualified charging begins is
precharge. The CHRG status output is set low and remains
low during both precharge and fast charge. If the voltage
on V

is below the 900mV (V

CELL

) fast charge qualifica-

FCQ

tion voltage, the LTC4060 charges using one-fifth the
maximum programmed charge current. The cell voltage is
continuously checked to determine when the battery is
ready to accept a fast charge. Until this voltage reaches
V

, the LTC4060 remains in precharge.

FCQ

If an external thermistor indicates that the sensed tem­perature is beyond a range of 5°C to 45°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.

Fast Charge

When the average cell voltage exceeds V

, the LTC4060

FCQ

transitions from the precharge to the fast charge state and

Table 1. LTC4060 Time Limit Programming Examples

TYPICAL BATTERY CHARGE BATTERY AUTOMATIC

FAST VOLTAGE TIME VOLTAGE RECHARGE UVLO EXIT, BATTERY

FAST CHARGE STABILIZATION LIMIT SAMPLING ENTRY INSERTION/REMOVAL/OVERVOLTAGE,

CHARGE RATE HOLD OFF (t

CURRENT R

2A 698Ω 1nF 1.5 4.6 to 5.7 1.1 15 15 to 31 175 to 260

2A 698Ω 1.5nF 1 6.9 to 8.4 1.6 23 23 to 46 260 to 390

2A 698Ω 1.8nF 0.75 8.4 to 10.3 2 28 28 to 56 320 to 480

2A 698Ω 2.7nF 0.5 12.6 to 15.4 3 42 42 to 84 480 to 720

400mA 3480Ω 180pF 1.5 4.2 to 5.2 1 14 14 to 28 160 to 240

400mA 3480Ω 270pF 1 6.3 to 7.7 1.5 21 21 to 42 240 to 360

400mA 3480Ω 390pF 0.75 8.9 to 11 2.1 30 30 to 60 340 to 510

400mA 3480Ω 560pF 0.5 12.6 to 15.4 3 42 42 to 84 480 to 720

PROGCTIMER

(C) (MINUTES) (HOURS) (SECONDS) (SECONDS) THERMISTOR EVENT DELAYS (ms)

) INTERVAL DELAY FAST CHARGE ENTRY AND

MAX

10

4060f

OPERATIO

LTC4060

U

charging begins at the maximum current set by the
exter

nal 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. If voltage-based termina­tion was imminent when the temperature limits were
exceeded, charge termination will occur.

Charge Termination

Once fast charge begins and after an initial battery voltage
stabilization hold-off period shown in Table 1, voltage­based termination (–∆V) is enabled. This period is used to
prevent falsely terminating on a –∆V event that can occur
almost immediately after initiating charging on some
heavily discharged or stored batteries. However, if V
was measured to be above 1.3V (V
to the precharge cycle, then a mostly charged battery is
assumed and voltage-based termination (–∆V) is enabled
without delay.

An internal 1.5mV resolution A/D converter measures the
cell voltage after each battery voltage sampling interval
indicated in Table 1. The peak cell voltage is stored and
compared to the current cell voltage. When the cell voltage
has dropped by at least V
CHEM pin) from the peak for four consecutive battery
voltage sampling intervals, charging is terminated.

Back-up termination is provided by the charge time limiter,
whose time limit is indicated in Table 1, and by a battery
overvoltage detector. Once terminated by back-up termi­nation, charge qualification can be reinitiated only by remov­ing and replacing the battery or toggling the SHDN pin low
to high or removing and reapplying power to the charger.

Automatic Recharge

Once charging is complete, the optional programmable
automatic recharge state can be entered. This state, if

(magnitude selected by the

MDV

) immediately prior

IDT

CELL

enabled, will automatically restart the charger from the
charge qualification state without user intervention when­ever the battery cell voltage drops below a set level. With
the advent of low memory effect NiMH and improved NiCd
cells an automatic recharge feature is practical and elimi­nates the need for very slow trickle charging.

The CHRG status output is high impedance in the auto­matic recharge state until charging begins. If the V
voltage drops below the voltage set on the ARCT pin for at
least the automatic recharge entry delay time as shown in
Table 1, the charge qualification state is entered and
charging will begin anew in fast charge. An easy way of
setting the voltage on the ARCT pin is by using two series
current programming resistors and connecting their com­mon to the ARCT pin as shown in Figure 2. The PROG pin
will provide a constant 1.5V (V
voltage range of the ARCT pin is approximately 0.8V to

1.6V. A preprogrammed recharge threshold of 1.3V (V
is selected when the ARCT pin is connected to V
(V
pin is connected to ground (V

Pause

After charging is initiated, the PAUSE pin may be used to
pause operation at any time. Whenever the voltage on the
PAUSE pin is a logic high, the charge timer and all other
timers pause, charging is stopped and the fast charge ter­mination algorithm is inhibited. The CHRG status output
remains at GND. If voltage-based termination was immi­nent before pause, charge termination will occur. Otherwise,
when pause ends, the charge timer and all other timers
resume timing, charging restarts and voltage-based termi­nation (–∆V) is reset and immediately enabled. If the bat­tery is removed while the PAUSE pin is a logic high, then
battery removal is detected and shutdown is entered. If the
battery is replaced while the PAUSE pin is a logic high, it
will not be detected until pause is turned off.

For pause periods or a series of periods where the battery
capacity could be significantly depleted, consider using
shutdown instead of pause to avoid having the safety timer
expire before the battery can be fully charged. Shutdown
resets the safety timer.

). Automatic recharge is disabled when the ARCT

ARDEF

). The programmable

PROG

).

ARDIS

CELL

ARDT

)

CC

4060f

11

LTC4060

OPERATIO

U

Battery Chemistry Selection

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.

Cell Selection

The number of series cells is selected using the SEL0 and
SEL1 pins. For one cell, both pins connect to GND. For two
cells, SEL0 connects to VCC and SEL1 to GND. For three
cells, SEL0 connects to GND and SEL1 to VCC. For four
cells, both connect to VCC.

Table 2. LTC4060 Charging Parameters

STATE CHEM CHARGE TIME LIMIT T

Precharge Both t

Fast Charge NiCd t

NiMH t

MAX

MAX

MAX

MIN

5°C45°CI

5°C55°CI

5°C55°CI

T

MAX

Insertion and Removal of Batteries

The LTC4060 automatically senses the insertion or re­moval of a battery by monitoring the V

pin voltage.

CELL

Either the charge current, or if not charging then an
internal pull-up current (I

), will pull V

BRD

up when the

CELL

battery is removed. When this voltage rises above 2.05V
(VBR) for a time greater than the battery removal event
delay shown in Table 1, the LTC4060 considers the battery
to be absent. Inserting a battery, causing V
below both VBR and 1.95V (V

) for a period longer than

BOV

CELL

to fall

the battery insertion event delay shown in Table 1, results
in the LTC4060 recognizing a battery present and initiates
a completely new charge cycle beginning with charge
qualification. All battery currents are inhibited while in
shutdown.

I

CHRG

MAX

MAX

MAX

TYPICAL TERMINATION CONDITION

/5 V

≥ 0.9V

CELL

–16mV Per Cell After Initial t

–8mV Per Cell After Initial t

MAX

MAX

/12 Delay

/12 Delay

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APPLICATIO S I FOR ATIO

Programming Charge Current

The battery charge current is set with an external program
resistor connected from the PROG pin to GND. The for­mula for the battery fast charge current or I

II

=

MAX PROG

()

•

⎜
⎝

R

⎛

=

.

15

PROG

⎞

V

•930

930

⎟
⎠

or

R

PROG

where R

1395

=

I

MAX

is the total resistance from the PROG pin to

PROG

ground. For example, if 1A of fast charge current is
required:

R

PROG

1395

==

A

1

k

14. 1% Resistor

MAX

is:

Under precharge conditions, the current is reduced to
20% of the fast charge value (I

).The LTC4060 is

MAX

designed for a maximum current of 2A. This translates to
a maximum PROG pin current of 2.15mA and a minimum
program resistor of 698Ω. Reduced accuracy at low
current limits the useful fast charge current to a minimum
of approximately 200mA. Errors in the charge current can
be statistically approximated as follows:

One Sigma Error ≅ 7mA

For best stability over temperature and time, 1% metal­film resistors are recommended. Capacitance on the PROG
pin should be limited to about 75pF to insure adequate AC
phase margin for its amplifier.

Different charge currents can be programmed by various
means such as by switching in different program resis­tors. A voltage DAC connected through a resistor to the
PROG pin or a current DAC connected in parallel with a

12

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APPLICATIO S I FOR ATIO

LTC4060

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 (V

PROG

)
that may be tapped for system use. Current loading on
PROG is multiplied by 930 and appears as increased I
This may be compensated by adjustment of R

PROG

MAX.

. Total
PROG pin current must be limited to 2.3mA otherwise
absolute maximum ratings will be exceeded. When the
LTC4060 is in the shutdown mode, the PROG pin is forced
to ground potential to save power.

Programming the Timer

All LTC4060 internal timing is derived from the internal
oscillator that is programmed with an external capacitor at
the TIMER pin. The time periods shown in Table 1 scale
directly with the timer period. The programmable safety
timer is used to put a time limit on the entire charge cycle
for the case when charging has not otherwise terminated.

The time limit is programmed by an external capacitor at
the TIMER pin and is also dependent on the current set by
the programming resistor connected to the PROG pin. The
time limit is determined by the following equation:

t

(Hours) = 1.567 • 106 • R

MAX

CF

TIMER

()

=

.• • ()

t Hours

()

MAX

6

R

PROG

PROG

(Ω) • C

Ω1 567 10

TIMER

(F)

Some typical timing values are detailed in Table 1. The
timer begins at the start of a charge cycle. After the time­out occurs, the charge current stops and the CHRG output
assumes a high impedance state to indicate that the
charging has stopped.

Excessively short time-out periods may not allow enough
time for the battery to receive full charge or may result in
premature –∆V termination due to too short a battery
voltage stabilization hold-off period. Excessively long time­out periods may indicate too low a charge current which
may not allow voltage-based termination (–∆V) to work
properly. Time-out limits of less than 0.75 hour for faster
2C charge rates, or more than 3.5 hours for slower C/2

charge rates, are generally not recommended. Consult the
battery manufacturer for recommended periods.

An external timing source can also be used to drive the
TIMER pin for precise or programmed control. The high
level must be between 2.5V and V

and the low level must

CC

be between 0V and 0.25V. Also, the driving source must be
able to overdrive the internal current source and sink
which is 5% of the current through R

PROG

.

Battery Temperature Sensing

Temperature sensing is optional in LTC4060 applications.
To disable temperature qualification of all charging opera­tions, the NTC pin must be wired to ground. A circuit for
temperature sensing using a thermistor with a negative
temperature coefficient (NTC) is shown in Figure 2. Inter­nally derived VCC proportional voltages (V

CLD

, V

HTI

, V

HTC

)
are compared to the voltage on the NTC input pin to test the
temperature thresholds. The battery temperature is mea­sured by placing the thermistor close to the battery pack.
In Figure 2, a common 10k NTC thermistor such as a
Murata NTH4G series NTH4G39A103F can be used. R

HOT

should be a 1% resistor with a value equal to the value of
the chosen NTC thermistor at 45°C (V

NTC

= V

= 0.5 • V

HTI

CC

typ). Another temperature may be chosen to suit the
battery requirements. The LTC4060 will not initiate a
charge cycle or continue with a precharge if the value of the
thermistor falls below 4.42k which is a temperature rising
to approximately 45°C. However, once fast charging is in
progress, it will not be stopped until the thermistor drops
below 3k which is a temperature rising to approximately
55°C (V

NTC

= V

= 0.4 • VCC typ). Once reaching this

HTC

charge cutoff threshold, charging is suspended until the
value of the thermistor rises above approximately 4.8k
(falling temperature) or approximately 43°C (45°C – 2°C
hysteresis at V

= 5V) and then charging is resumed.

CC

Hysteresis avoids possible oscillation about the trip points.
Note that the comparator hysteresis voltages are constant
and when VCC increases the signal level from the ther­mistor increases thus making the temperature hysteresis
look smaller.

During suspension the charge current is turned off and the
safety timer is frozen. The LTC4060 is also designed to
suspend when the thermistor rises above 34k (falling

4060f

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LTC4060

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APPLICATIO S I FOR ATIO

temperature) at approximately 0°C (5°C – 5°C hysteresis
at V
below 27k (rising temperature) which will be approxi­mately 5°C (V

Many thermistors with an R
mately 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.

It is important that the thermistor be placed in close
contact with the battery and away from the external PNP
pass transistor to avoid excessive temperature errors on
the sensed battery temperature. Furthermore, since VCC is
a high current path into the LTC4060, it is essential to
minimize voltage drops between the VCC supply pin and
the top of R
VCC pin.

Power Requirements

The DC power input to the VCC pin must always be within
proper limits while charging a battery. Voltages beyond
the absolute maximum ratings may damage the charger
and voltages falling below the UVLO entry thresholds, as
programmed by the SEL0 and SEL1 pins, will likely cause
the charger to enter the shutdown state (when the UVLO
exit threshold is exceeded charging will begin anew). While
the LTC4060 is designed to reject 60Hz or 120Hz supply
ripple, certain precautions are required. The instantaneous
ripple voltage must always be within the above mentioned
limits. Ripple voltage seen across the collector-base junc­tion of the external PNP pass transistor will slightly modu­late its beta and hence its base current. Since the emitter
current is precisely regulated by the LTC4060, any modu­lation of base current will appear at the collector. This
slightly modulated battery charge current into a battery
will usually produce an insignificant modulation voltage at
the battery. However, if excessive wire impedance to the
battery from the PNP exists, then it may be helpful to Kelvin
connect the BAT pin to a convenient point closest to the
battery to reduce ripple magnitude entering the LTC4060’s
battery monitoring circuits. The battery ground imped­ance should also be managed to limit ripple voltage at the
BAT pin. Excessive ripple into the BAT pin may cause the
charger to deviate from specified performance.

= 5V) and then resume when the thermistor falls

CC

= V

NTC

by Kelvin connecting R

HOT

= 0.86 • VCC typ).

CLD

to R

COLD

ratio of approxi-

HOT

directly to the

HOT

VCC Bypass Capacitor

A 1µF capacitor located close to the LTC4060 will usually
provide adequate input bypassing. However, caution must
be exercised when using multilayer ceramic capacitors.
Because of the self-resonance and high Q characteristics
of some types of ceramic capacitors, along with wiring
inductance, high voltage transients can be generated
under some conditions such as connecting or disconnect­ing a supply input to a hot power source. To reduce the Q
and prevent these transients from exceeding the absolute
maximum voltage rating, consider adding about 1Ω of
resistance in series with the ceramic input capacitor.

BAT Bypass Capacitor

This optional capacitor, connected between BAT and GND,
can be used to help filter excessive contact bounce during
the battery monitoring or charging process. The value will
depend upon the contact bounce open duration, but is typi­cally 10µF. Another purpose of this capacitor is to bypass
transient battery load events that might otherwise disrupt
monitoring or charging. Should the battery connections not
be subject to excessive contact bounce or excessive bat­tery voltage transients, then no BAT pin capacitor is re­quired. The same caution mentioned above for the VCC by­pass capacitor applies.

External PNP Transistor

The external PNP pass transistor must have adequate beta
and breakdown voltages, low saturation voltage and suf­ficient power dissipation capability that may include heat
sinking.

To provide 2A of charge current with the minimum avail­able base current drive of 40mA (I
minimum PNP beta of 50.

The transistor’s collector to emitter breakdown voltage
must be high enough to withstand the difference between
the maximum supply voltage and minimum battery volt­age. Almost any transistor will meet this requirement.
Additionally, when no power is supplied to the charger
(V

= 0V and V

IN

breakdown voltage must be high enough to prevent a
leakage path at the maximum battery voltage while not

= 0V), the transistor’s emitter to base

SENSE

min) requires a

DRV

14

4060f

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APPLICATIO S I FOR ATIO

LTC4060

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
(V

) becomes important. The V

CESAT

CESAT

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.

V

CESAT

(V) < V

DD(MIN)

– (I

BAT(MAX)

• 0.08Ω + V

BAT(MAX)

)

For example, if it were desired to have a programmed
charge current of 2A with a minimum supply voltage of

4.75V and a maximum battery voltage of 3.6V (2 series
cells at 1.8V each), then the minimum operating V

V

(V) = 4.75 – (2 • 0.08 + 3.6) = 0.99V

CESAT

CESAT

is:

If the PNP transistor cannot achieve the saturation voltage
required, base current will dramatically increase. This is to
be avoided for a number of reasons: DRIVE pin current
may reach current limit resulting in the LTC4060 charac­teristics going out of specifications, excessive power
dissipation may force the IC into thermal shutdown, or the
battery could discharge because some of the current from
the DRIVE pin could be pulled from the battery through the
forward biased PNP collector base junction.

The actual battery fast charge current (I

) is slightly less

BAT

than the regulated charge current because the charger
senses the emitter current and the battery charge current
will be reduced by the base current. In terms of β (IC/IB)
I

can be calculated as follows:

BAT

⎛

⎞

IA I

() •=

BAT PROG

If β = 100 then I

930

is 1% low. The 1% loss can be easily

BAT

compensated for by increasing I

β

⎜

⎟

+

1

β

⎝

⎠

by 1%.

PROG

Another important factor to consider when choosing the
PNP pass transistor is its power handling capability. The
transistor’s data sheet will usually give the maximum rated
power dissipation at a given ambient temperature with a

power derating for elevated temperature operation. The
maximum power dissipation of the PNP when charging is:

P

D(MAX)

V

DD(MAX)

(W) = I

MAX(VDD(MAX)

is the maximum supply voltage and V

– V

BAT(MIN)

)

BAT(MIN)

is
the minimum battery voltage when discharged, but not
less than 0.9V/cell since less than 0.9V/cell invokes
precharge current levels.

Thermal Considerations

Internal overtemperature protection is provided to prevent
excessive LTC4060 die temperature during a fault condi­tion. If the internal die temperature exceeds approximately
145°C, charging stops and the part enters the shutdown
state. The faults can be generated from insuffient heat
sinking, a shorted DRIVE pin or from excessive DRIVE pin
current to the base of an external PNP transistor if it’s in
deep saturation from a very low VCE. Once in the shutdown
state, charge qualification can be reinitiated only by re­moving and replacing the battery or toggling the SHDN pin
low to high or removing and reapplying power to the
charger. This protection is not designed to prevent over­heating of the PNP pass transistor. Indirectly though, self­heating of the PNP thermally conducting to the LTC4060
can result in the IC’s junction temperature rising above
145°C, thus cutting off the PNP’s base current. This action
will limit the PNP’s junction temperature to some tempera­ture well above 145°C. The user should insure that the
maximum rated junction temperature is not exceeded
under any normal operating condition. See Package/Order
Information for the θJA of the LTC4060 Exposed Pad
packages. The actual thermal resistance in the application
will vary depending on forced air cooling, use of the
Exposed Pad and other heat sinking means, especially the
amount of copper on the PCB to which the LTC4060 is
attached. The majority of the power dissipated within the
LTC4060 is in the current sense resitor and DRIVE pin
driver as given below:

PD = (I

TJ = TA + θJA • P

)2 • 0.08 + I

BAT

(VCC – VEB)

DRIVE

D

VEB is the emitter to base voltage of the external PNP.

4060f

15

LTC4060

TYPICAL APPLICATIO S

U

Full Featured 2A Charger Application

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.

The PROG pin has a total resistance of 691Ω to ground
that programs the fast-charge current at the PNP’s emitter
to 2.02A (2A at the collector for beta of 100). The ARCT pin
voltage is programmed to 1.25V. When the battery cell
voltage falls below this automatic recharge will begin.
Optional capacitor C

filters excessive contact bounce.

BAT

This circuit can be modified to charge a 4A-Hr battery at a
C/2 rate simply by doubling the C

R

4.42k

“CHARGE”

TIMER

HOT

R

NTC

10k

capacitance.

R

LED

330Ω

5

SHDN

15

CHRG

11

NTC

7

PROG

R

PROG

115Ω

R

ARCT

576Ω

8

ARCT

9

SEL0

10

SEL1

V

5V

IN =

14

V

CC

SENSE

DRIVE

LTC4060

TIMER

PAUSE

GND

16

ACP

BAT

CHEM

Power Path Control

Proper power path control is an important consideration
when fast charging nickel cells. This control ensures the
system load remains powered at all times, but that normal
system operation and associated load transients do not
adversely affect the charging procedure. Figure 3 illus­trates a 1A charger with power path control. When VIN is
applied the forward biased Schottky diode will power the
load while the P-channel FET will disconnect the battery
from the load. When VIN is removed, the FET will turn-on
to provide a low loss switch from the battery to the load,
and the diode will isolate V
presense of V

R

LED

330Ω

MJD210

4060 F02

“AC”

C

TIMER

1.5nF

13

3

1

2

4

12

6

IN

.

C

BAT

10µF

+

. The ACP output signals the

IN

2-CELL
NiMH
BATTERY

16

R

330Ω

“CHARGE”

R

PROG

1400Ω

Figure 2. Full Featured 2A Charger Application

V

5V

IN =

LED

V

SHDN

CHRG

NTC

PROG

ARCT

SEL0

SEL1

CC

ACP

SENSE

DRIVE

LTC4060

BAT

TIMER

CHEM

PAUSE

GND

16

5

15

11

7

8

9

10

R

AC

10k

13

3

1

2

4

12

6

FZT948

ACP

C

TIMER

820pF

+

2-CELL
NiMH
BATTERY

*DRAIN SOURCE DIODE OF MOSFET

Figure 3. 1A Charger Application with Power Path Control

B220A

FDG312P

*

C
10µF

4060 F03

TO LOAD

LOAD

4060f

TYPICAL APPLICATIO S

LTC4060

U

Trickle Charge

The trickle charge function is normally not required due to
the automatic recharge feature. However, the LTC4060
does provide a modest pull-up current (I

) as part of its

BRD

battery removal detection method. If additional current is
required for trickle charge or to support battery removal
detection with current loads greater than I

, then the

BRD

simple circuit of Figure 4 will facilitate that. The diode
insures no reverse discharge current when V

is removed

IN

and the resistor sets the trickle current.

Extending Charge Current

Extending the charge current beyond 2A can be accom­plished by paralleling an external current sense resistor,
R

with the internal current sense resistor as shown in

ISET,

Figure 5. Bond wire, lead frame and PCB interconnect

V

IN

14

V

CC

LTC4060

SENSE

DRIVE

BAT

3

1

2

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 R

ISET

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). The formula for extended fast charge current is:

II

MAX EXT MAX

for R

ISET

=+

()

AA

•.

==

2153

= 0.16Ω and R

⎛

•

1

⎜
⎝

PROG

.

008

R

ISET

= 698Ω.

⎞
⎟

⎠

Adequate PNP beta is required to meet the DRIVE pin
capability and the increased PNP power dissipation will
require additional heat sinking.

1N4001

3.3k

+

2-CELL
NiMH
BATTERY

4060 F04

Figure 4. Adding Trickle Charge

V

IN

14

V

CC

0.08Ω

SENSE

DRIVE

LTC4060

Figure 5. Extended Charge Current Operation

BAT

R

ISET

0.16Ω

3

1

2

+

2-CELL
NiMH
BATTERY

4060 F05

4060f

17

LTC4060

TYPICAL APPLICATIO S

U

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.

*

LTC4060

V

IN

*DRAIN BULK DIODE OF MOSFET

Figure 6. Low Loss Reverse Input Voltage Protection

14

V

CC

4060 F06

18

4060f

PACKAGE DESCRIPTIO

LTC4060

U

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 SIDES)2.20 ±0.05

4.40 ±0.05
(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

5.00 ±0.10
(2 SIDES)

PIN 1

TOP MARK

(SEE NOTE 6)

0.200 REF

NOTE:

1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC
PACKAGE OUTLINE MO-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE

0.25 ± 0.05

0.50 BSC

PACKAGE
OUTLINE

3.00 ±0.10
(2 SIDES)

0.75 ±0.05

R = 0.20

1.65 ± 0.10
(2 SIDES)

0.00 – 0.05

TYP

R = 0.115

TYP

0.25 ± 0.05

0.50 BSC

4.40 ±0.10
(2 SIDES)

BOTTOM VIEW—EXPOSED PAD

169

18

0.40 ± 0.10

PIN 1
NOTCH

(DHC16) DFN 1103

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 represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

4060f

19

LTC4060

PACKAGE DESCRIPTIO

U

FE Package

16-Lead Plastic TSSOP (4.4mm)

(Reference LTC DWG # 05-08-1663)

Exposed Pad Variation BC

3.58

(.141)

4.90 – 5.10*
(.193 – .201)

3.58

(.141)

16 1514 13 12 11

10 9

6.60 ±0.10

4.50 ±0.10

RECOMMENDED SOLDER PAD LAYOUT

0.09 – 0.20

(.0035 – .0079)

NOTE:

1. CONTROLLING DIMENSION: MILLIMETERS

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE

SEE NOTE 4

0.65 BSC

4.30 – 4.50*
(.169 – .177)

0.50 – 0.75

(.020 – .030)

MILLIMETERS

(INCHES)

2.94

(.116)

0.45 ±0.05

1.05 ±0.10

1345678

2

0.25
REF

0° – 8°

0.65

(.0256)

BSC

0.195 – 0.30

(.0077 – .0118)

TYP

4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT

*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE

2.94

(.116)

1.10

(.0433)

MAX

0.05 – 0.15

(.002 – .006)

FE16 (BC) TSSOP 0204

6.40

(.252)

BSC

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ThinSOT and PowerPath are trademarks of Linear Technology Corporation.

Linear Technology Corporation

20

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear.com

Charger Detection and Programmable Timer, Input Power Good Indication

≤ 180mA

CHRG

±0.8% Charging Voltage Accuracy

More Efficiently

4060f

LT/TP 0904 1K • PRINTED IN THE USA

© LINEAR TECHNOLOGY CORPORATION 2004