LTC1729CS8-8.2 - Linear Technology

LTC1729 Series

■

Built-In Termination: 3-Hour Time-Out

■

C/10 Detection with Status Indicator

■

Trickle Charge Preconditioning If Cell <2.7V

■

Charging Enabled When 0°C < T < 50°C

■

Automatic Charger Present Detection

■

Automatic Battery Present Detection

■

1- or 2-Cell, 4.1V/Cell or 4.2V/Cell Options

■

Precision Internal 0.2% Voltage Feedback Divider

■

Compatible with LT1505/LT1510/LT1511/

LT1512/LT1513/LT1769

■

Small Footprint/Low Profile

The LTC

1729 series is a family of smart

termination

controllers for lithium-ion battery chargers. These ICs

provide trickle charge preconditioning, temperature charge

qualification, time or charge current termination, auto-

matic charger and battery detection and status output.

Combining the LTC1729 series part with the LT

1510

(1.5A), LT1769 (2A), LT1511 (3A) and LT1505 (>4A)

step-down chargers is a simple operation. Connecting six

pins from the LTC1729 series part to the step-down

chargers completes the integration. The LTC1729 termi-

nation controllers are also compatible with step-down/

step-up (SEPIC) chargers, including the LT1512 (2A switch)

and LT1513 (3A switch).

The LTC1729 series is available in the 8-pin MSOP and SO

packages.

■

Cellular Phones

■

PDAs

■

Cradle Chargers

■

Camcorders

Figure 1. 500kHz Li-Ion Cell Phone Charger (0.8A)

Li-Ion Battery Charger

Termination Controllers

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

OVP

BAT

SENSE

GND

STATUS

NTC

SENSE

OVP

GND

BOOST

PROG

BAT

LTC1729-4.2

LT1510-5

1µF

0.22µF

L1**

10µH

0.1µF

1729 F01

OPTION: TIE RESISTOR TO STATUS FOR

CHARGE TERMINATION AT

LOW CHARGING CURRENT

* TOKIN OR MARCON SURFACE MOUNT

** COILTRONICS TP3-100, 10µH, 2.2mm HEIGHT

(0.8A CHARGING CURRENT)

COILTRONICS TP1 SERIES, 10µH, 1.8mm

HEIGHT (<0.5A CHARGING CURRENT)

*** PANASONIC EEFCD1B220

†

LUMEX SML-LX0805GW-TR

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE

NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

0.1µF

1µF

OUT

***

22µF4.2V

200Ω

300Ω6.19k

10µF

MBRM120T3 INPUT POWER

8.2V TO 20V

†

CHARGE STATUS

MBRM120T3

MMBD914L

1.4k

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

LTC1729 Series

LTC1729CMS8-4.1

LTC1729CMS8-4.2

LTC1729CMS8-8.2

LTC1729CMS8-8.4

JMAX

= 150°C, θ

= 150°C/W

ORDER PART

NUMBER

......................................................................... 30V

SENSE, V

BAT

, NTC .................................... –0.3V to 15V

............................................................. –0.3V to 15V

OVP ............................................................ –0.3V to 5V

(Note 1)

Consult factory for Industrial and Military grade parts.

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 8V

OVP

BAT

SENSE

GND

STATUS

NTC

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

JMAX

= 150°C, θ

= 200°C/ W

MS8 PART MARKING

LTLY

LTJH

LTLZ

LTJG

TOP VIEW

OVP

BAT

SENSE

GND

STATUS

NTC

S8 PACKAGE

8-LEAD PLASTIC SO

LTC1729CS8-4.1

LTC1729CS8-4.2

LTC1729CS8-8.2

LTC1729CS8-8.4

ORDER PART

NUMBER

S8 PART MARKING

STATUS .................................................... –0.3V to 30V

Operating Temperature Range .................... 0°C to 70°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

LTC1729-4.1/LTC1729-4.2

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

DC CHARACTERISTICS

Supply Current V

= 5V (Below UVLO) ●1512 µA

= 8V, V

BAT

> 4.5V, No Bat ●1.0 1.4 2.0 mA

= 8V, V

BAT

= 2.5V Trickle 10 17 21 mA

= 8V, V

BAT

= 3.5V Charge ●0.5 3.0 5.0 mA

LKOH

Undervoltage Lockout High ●5.5 6.5 7.5 V

LKOL

Undervoltage Lockout Low ●5.0 6.0 7.0 V

VBAT

BAT

Current V

= 5V (Below UVLO), V

BAT

= 4.2V ●–1 –0.1 1 µA

= 8V, V

BAT

= 4.25V No Bat ●40 73 120 µA

= 8V, V

BAT

= 2.5V Trickle –19 –12 –9.5 mA

= 8V, V

BAT

= 3.5V Charge ●–2.7 –1.3 –0.5 mA

CLAMP

BAT

Clamp No Bat (External 200µA Pull-Up on V

BAT

)●4.25 4.5 4.75 V

MAX

High V

BAT

Threshold High Going Threshold ●4.25 4.51 4.75 V

Low Going Threshold ●4.25 4.50 4.75 V

MIN

Low V

BAT

Threshold High Going Threshold ●2.55 2.7 2.85 V

Low Going Threshold ●2.45 2.6 2.75 V

SENSE

SENSE Pin Current Charge State, V

SENSE

= 3V ●85 100 115 µA

C10

SENSE Pin C/10 Offset Charge State, V

C10

= (V

BAT

– V

SENSE

)●±1±2.5 mV

172941

172942

172982

172984

ABSOLUTE AXI U RATI GS

WWWU

PACKAGE/ORDER I FOR ATIO

ELECTRICAL CHARACTERISTICS

LTC1729 Series

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 8V

LTC1729-4.1/LTC1729-4.2

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

NTC

NTC Pin Current V

NTC

= 1V ●90 100 110 µA

NTC-RESET

Thermistor Pin Reset Threshold ●0.160 0.206 0.240 V

NTC-HOT

Thermistor Pin Hot Hold Threshold High Going Threshold ●0.460 0.486 0.510 V

Low Going Threshold ●0.380 0.405 0.430 V

NTC-COLD

Thermistor Pin Cold Hold Threshold High Going Threshold ●2.70 2.79 2.90 V

Low Going Threshold ●2.10 2.23 2.35 V

OVP

OVP Pin Voltage V

BAT

= 4.1V or V

BAT

= 4.2V ●2.455 2.465 2.475 V

2.460 2.465 2.470 V

OL-ST

Output Low Voltage-STATUS Pin I

= 3mA ●0.5 0.9 1.2 V

OL-VC

Output Low Voltage-V

Pin I

= 1mA ●0.35 0.6 0.75 V

SOFT

Status Soft Pull-Down Current V

STATUS

= 4.5V ●40 50 65 µA

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 12V

LTC1729-8.2/LTC1729-8.4

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

DC CHARACTERISTICS

Supply Current V

= 9V (Below UVLO) ●1612 µA

= 12V, V

BAT

> 9V, No Bat ●1.0 1.4 2.0 mA

= 12V, V

BAT

= 5V Trickle 10 17 21 mA

= 12V, V

BAT

= 7V Charge ●0.5 3.0 5.0 mA

LKOH

Undervoltage Lockout High ●9.5 10.4 11.4 V

LKOL

Undervoltage Lockout Low ●8.5 9.6 10.5 V

VBAT

BAT

Current V

= 9V (Below UVLO), V

BAT

= 8.4V ●–1 –0.1 1 µA

= 12V, V

BAT

= 8.5V No Bat ●60 95 140 µA

= 12V, V

BAT

= 5V Trickle –19 –12 –9.5 mA

= 12V, V

BAT

= 7V Charge ●–2.7 –1.3 –0.5 mA

CLAMP

BAT

Clamp No Bat (External 200µA Pull-Up on V

BAT

)●8.5 9 9.5 V

MAX

High V

BAT

Threshold High Going Threshold ●8.5 9.013 9.5 V

Low Going Threshold ●8.5 9 9.5 V

MIN

Low V

BAT

Threshold High Going Threshold ●5.1 5.4 5.7 V

Low Going Threshold ●4.9 5.2 5.5 V

SENSE

SENSE Pin Current Charge State, V

SENSE

= 7V ●85 100 115 µA

C10

SENSE Pin C/10 Offset Charge State, V

C10

= (V

BAT

– V

SENSE

)●±1±2.5 mV

NTC

NTC Pin Current V

NTC

= 1V ●90 100 110 µA

NTC-RESET

Thermistor Pin Reset Threshold ●0.160 0.206 0.240 V

NTC-HOT

Thermistor Pin Hot Hold Threshold High Going Threshold ●0.460 0.486 0.510 V

Low Going Threshold ●0.380 0.405 0.430 V

NTC-COLD

Thermistor Pin Cold Hold Threshold High Going Threshold ●2.70 2.79 2.90 V

Low Going Threshold ●2.10 2.23 2.35 V

OVP

OVP Pin Voltage V

BAT

= 8.2V or V

BAT

= 8.4V ●2.455 2.465 2.475 V

2.460 2.465 2.470 V

OL-ST

Output Low Voltage-STATUS Pin I

= 3mA ●0.5 0.9 1.2 V

OL-VC

Output Low Voltage-V

Pin I

= 1mA ●0.35 0.6 0.75 V

SOFT

Status Soft Pull-Down Current V

STATUS

= 4.5V ●40 50 65 µA

LTC1729 Series

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired. Note 2: V

= 8V for LTC1729-4.1/LTC1729-4.2; V

= 12V for

LTC1729-8.2/LTC1729-8.4

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

AC CHARACTERISTICS

TIMER1 Timer for Trickle-Charge Preconditioning ●0.869 1 1.305 Hr

TIMER2 Timer for Charging ●2.61 3 3.55 Hr

TIMER3 Timer for V

MAX

Filter ●0.764 0.859 1.043 sec

TIMER4 Timer for V

C/10

Filter ●3.055 3.5 4.17 sec

OSC

Oscillator Period ●6.66 7.63 9.09 µs

ELECTRICAL CHARACTERISTICS

TYPICAL PERFOR A CE CHARACTERISTICS

IVBAT vs Temperature (4.2V Version)

TEMPERATURE (°C)

1729 G01

25 50 100

VBAT

(mA)

BAT

= 2.5V

TEMPERATURE (°C)

1729 G02

25 50 100

VBAT

(mA)

BAT

= 5V

(V)

018 26

1729 G03

10 14 22 30

VBAT

(mA)

BAT

= 3.5V

BAT

= 2.5V

IVBAT vs Temperature (8.4V Version) IVBAT vs VCC (4.2V Version)

IVBAT vs VCC (8.4V Version) ICC vs VCC (8.4V Version)

(V)

VBAT

(mA)

14 18 22 26

1729 G04

BAT

= 5V

BAT

= 7V

ICC vs VCC (4.2V Version)

VCC (V)

ICC (mA)

10 14 18 22

1729 G05

26 30

12 VBAT = 2.5V

VBAT = 3.5V

(V)

(mA)

14 18 22 26

1729 G06

BAT

= 5V

BAT

= 7V

LTC1729 Series

OVP (Pin 1): Connection to an Internal Precision Resistor

Divider Used as a Voltage Feedback Monitor for Constant-

Voltage Mode Charging.

BAT (Pin 2): Input to Battery Monitor Circuits and OVP

Resistor Divider. The battery monitor circuits activate

trickle charge preconditioning, battery present detection

and C/10 current detection. This pin is in a high impedance

state when V

is below the undervoltage lockout thresh-

old. During trickle charge preconditioning and charging

the BAT pin sources 12mA and 1.3mA respectively. The

current sources are clamped from driving the BAT pin

above 4.5V/cell with an internal pull-down transistor.

In the No Bat, Done and Pause states or the Hold and Reset

modes, the current sources are turned off, leaving only the

55k OVP divider as a load on the BAT pin. Most chargers

have a 200µA current source that will compensate for this

50µA to 80µA load.

SENSE (Pin 3): Input to C/10 Current Detection Circuit.

This pin sinks 100µA during the Charge state which is used

to program the C/10 current threshold.

GND (Pin 4): Ground.

NTC (Pin 5): Input to the NTC Thermistor Monitoring

Circuits. When the voltage on this pin is above 2.79V

(cold) or below 0.405V (hot), the state machine is locked

in the present state and the timer is stopped. This is called

the Hold mode. While in the Hold mode, the charger is

turned off via the V

pin and the current sources on BAT

and SENSE pins are turned off. The STATUS pin is not

affected.

If the NTC pin is below 0.2V, the state machine is forced

in the reset mode with all the timers cleared to zero. The

current sources on the BAT pin and SENSE pin are

disabled leaving the 55k OVP divider. The STATUS pin is

pulled low in the Reset mode.

There is a 100µA current source on the NTC pin to bias the

NTC thermistor. This current source is active when the V

is greater than the undervoltage lockout threshold.

STATUS (Pin 6): Open-Drain Output for C/10 Charge

Termination Detection Circuit. When in the Charge state,

this pin is pulled low. Once the charge current drops below

the C/10 current threshold for three seconds, the pull-

down transistor is disabled, and a 50µA pull-down current

sink remains activated until the 1- or 3-hour time-out or

the battery or wall adapter is removed.

(Pin 7): Open-Drain Output for Turning Off the Charger.

When this pin is open circuit, the charger is active.

Normally this pin allows the charger to be active for three

hours.

(Pin 8): Input Supply. For 4.1V or 4.2V single cell

operation, V

should be between 8V and 28V with the IC

turning off when V

drops below 6V. For 2-cell applica-

tions, the undervoltage lockout is 10.4V with a minimum

of 12V. Removing the wall adapter will trigger an

undervoltage lockout and put the IC in a high impedance

condition. When the supply is connected, the IC is initial-

ized in the Reset mode with the state machine forced in the

Charge state with all the timers set to zero.

PI FU CTIO S

LTC1729 Series

BLOCK DIAGRA

BAT

OVP 1

NTC 5

SENSE

STATUS

100µA

1729 F02

–

COMP1

–

COMP4

UVLO

2.465V

2.79V

100µA

1.3mA

12mA

4.5V/CELL

CLAMP

–

COMP2

4.5V/CELL

–

COMP3

VMIN

VMAX

C/10

HOLD

RESET

2.7V/CELL

–

COMP5

0.405V

–

COMP6

0.2V

LOGIC

AND

TIMER

UVLO

50µA

Figure 2. Block Diagram

LTC1729 Series

Overview

The LTC1729 is a charge termination controller for the

LT1505/LT1510/LT1511/LT1512/LT1513/LT1769 con-

stant-voltage/constant-current battery charger family.

Table 1 details these chargers. The primary function of this

IC is to stop the charger after three hours of constant-

voltage/constant-current charging. The secondary func-

tion of this controller includes an indication when the

charge current (during constant-voltage mode) drops

below a user-selected threshold. A 500kHz Li-Ion cell

phone charger is shown in Figure 1. The LTC1729 requires

only six external components when combined with the

standard LT1510 application. The LTC1729 provides a

complete and tiny solution for cellular phones and other

portable applications.

Table 1. Battery Chargers

LT1505 4A Step-Down Charger with Input Current Limit

LT1510 1.5A Step-Down Charger

LT1510-5 1.5A 500kHz Step-Down Charger

LT1511 3A Step-Down Charger with Input Current Limit

LT1512 2A Switch SEPIC Charger

LT1513 3A Switch SEPIC Charger

LT1769 2A Step-Down Charger with Input Current Limit

Block Diagram

Figure 2 shows the block diagram of the LTC1729. The IC

consists of six comparators, a resistive divider, a UVLO

block and a logic and timer block.

100µA

50µA

1729 F03

–

COMP1

STATUS

CHARGE

LED

LTC1729

SENSE

BAT

–

200Ω

20mV

IBIAS

20mV R1

0.2Ω

CHARGING

CURRENT

1µF3-SEC

FILTER

LOGIC

AND

TIMERS

Figure 3. C/10 Detection Circuit

Comparator COMP1 is used to indicate C/10 charge cur-

rent threshold. (“C” is a term used to indicate the Ampere-

hour capacity of a cell.) Figure 3 details the C/10 detection

circuit. The resistor and capacitor on the SENSE pin filter

the signal from the 0.2Ω current sense resistor R1. The

100µA current sink on the SENSE pin develops 20mV

across the 200Ω resistor R2. This sets a 20mV offset on

COMP1 that sense resistor R1 must equal before C/10

current is indicated. The C/10 is not recognized by the logic

until it passes through a 3-second digital filter.

For cases where there are multiple batteries to be charged,

the LTC1729 detects when a battery is removed and resets

the timers for the next charge cycle. The battery present

detection is the primary function of comparator COMP2.

When the battery is disconnected from the LTC1729, the

voltage at the BAT pin will begin ramping upward. This is

due to a current source inside the charger or an external

pull-up resistor. Once the voltage on the BAT pin exceeds

the 4.5V/cell limit, COMP2 signals a V

MAX

= true to the

logic and turns on a transistor that clamps the voltage.

There is the possibility of an overvoltage transient at the

charging terminals. This occurs if the battery protection

circuit, which is often included in the battery pack, opens

the connection to the battery during high current charging

(constant-current mode). This is a result of energy storage

in the inductor. COMP2 senses the overvoltage and clamps

the V

pin, reducing the duty cycle of the charger. If the

battery protection circuit quickly returns battery connec-

tion to the charger (in less than one second), then the

LTC1729 continues charging without resetting the timers.

APPLICATIO S I FOR ATIO

WUUU

LTC1729 Series

MAX

= 1V

MIN

= 0V

4.5V/CELL

BATTERY CLAMP

PULL-DOWN

MAX

= 0V

MIN

= 0V

2.7V/CELL

NORMAL CHARGE

BATTERY VOLTAGE

MAX

= 0V

MIN

= 1V TRICKLE CHARGE

PRECONDITIONING

1729 F04

HOLD MODE

2.79V

THERMISTOR VOLTAGE

HOLD MODE

0.2V

RESET MODE

NORMAL CHARGE

0.405V

1729 F05

When the input supply is removed in step-down charger

designs, the V

pin does not drop to 0V, but is held to a

diode drop below the battery voltage. This is due to the

internal parasitic diode from the SW pin to the V

pin that

is present in the LT1510, LT1511, LT1769, and the body

diode of the top MOSFET in the LT1505 charger. Remov-

ing the input supply will result in the V

pin dropping

below the UVLO threshold, thus shutting down the LTC1729

and minimizing battery drain. Once the input supply is

connected, the LTC1729 resets the timers and begins

another charge cycle. There is a disconnect transistor that

will remove the OVP resistor divider from the battery when

the V

voltage drops below the UVLO threshold.

If external circuitry is connected directly to the V

pin and

the input power is removed, battery current will flow

through the charger’s internal parasitic diode (SW pin to

pin), discharging the battery and possibly damaging

the charger if currents greater than 1A are present. If

external circuitry is used, connect it directly to the input

power source (which is the anode of the input Schottky

diode).

The logic and timer block consists of a state machine,

oscillator and counter. The state machine will be dis-

cussed in detail in the next section. The oscillator is

internally trimmed to 131kHz. The counter is composed of

a chain of 25 flip-flops that includes self-test circuitry.

Figure 4. BAT Voltage Operating Range Figure 5. NTC Voltage Operating Range

For a battery that has been deeply discharged, the LTC1729

provides a 12mA start-up current. This preconditioning

trickle charge begins when the battery voltage drops

below 2.7V/cell. Comparator COMP3 is used to determine

when this condition exists. The battery operating range is

summarized in Figure 4.

With a 10k negative TC thermistor connected to the NTC

pin, the LTC1729 will disable charging if the temperature

is not in the 0°C to 50°C range. A thermistor must be

present at this pin, or if the temperature qualification

feature is not used, a 10k resistor must be used in its place.

This pin should not be left open. The NTC thermistor

monitoring circuits consist of COMP4, COMP5 and COMP6.

The NTC pin voltage range is shown in Figure 5.

Comparators COMP4 and COMP5 signal the logic when

the temperature is below 0°C or above 50°C. The 100µA

bias current through the 10kΩ thermistor will generate

2.79V at 0°C and 0.405V at 50°C. The voltage hysteresis

on COMP4 and COMP5 is designed to give 10°C of

temperature hysteresis. If the voltage on the NTC pin

drops below 0.2V, the comparator COMP6 generates a

reset to the logic and timer block.

To provide accurate charge voltages, the internal resistor

divider is trimmed to provide a precise ±0.2% voltage of

2.465V at the OVP pin for the four battery voltage options

of 4.1V, 4.2V, 8.2V and 8.4V.

APPLICATIO S I FOR ATIO

WUUU

LTC1729 Series

State Machine

The state machine is responsible for the following items:

1. When to start and stop the charger. The internal timer

must be initialized every time a new battery is installed

or when the input supply is applied.

2. When a battery is installed, the state machine must

determine if it is a new battery or if the previous battery

has been reinstalled.

3. When a deeply discharged battery is installed, trickle

charge conditioning must take place before the full

charge current.

The state machine diagram is shown in Figure 6. Note that

the Charge state includes the Precondition state, the

charger “ON” state and the Reset mode.

Reset and Hold are the two modes that will cause the

charger to stop charging (V

pin pulled low) and ignore the

state machine. The Reset mode clears all the timers and

forces the state machine to begin in the Charge state

(STATUS pin pulled low). This mode is only activated

momentarily at power-up or when the NTC pin is below the

Reset threshold. The other interrupt condition is called the

Hold mode. When the voltage on the NTC pin is above

2.79V (cold) or below 0.405V (hot), the state machine is

locked in the present state until the NTC pin voltage returns

to the proper range. While in the Hold mode, the charging

is disabled and the timers are frozen.

The charger is enabled only during the charger “ON” state.

There are three ways that the state machine can exit the

charger “ON” state. The first is for a 3-hour time-out which

is denoted as the time > t

MAX

transition to the Done state.

APPLICATIO S I FOR ATIO

WUUU

RESET MODE

BAT

= 0

STATUS = PULL-DOWN

= PULL-DOWN

PAUSE

BAT

= 0

STATUS = PULL-DOWN

= PULL-DOWN

DONE

BAT

= 0

STATUS = OPEN

= PULL-DOWN

NO BAT

BAT

= 0

STATUS = OPEN

= PULL-DOWN

HOLD MODE

BAT

= 0

STATUS = PREVIOUS STATUS

= PULL-DOWN

PRECONDITION

BAT

= 12mA

STATUS = PULL-DOWN

= PULL-DOWN

MAX

= 1HR

BAT

< V

MIN

BAT

> V

MIN

BAT

> V

MAX

TIME > t

MAX

1729 F06

NOTE: FOR STATUS

PULL-DOWN = HARD:

FOR CURRENT > C/10

PULL-DOWN = 50µA:

FOR CURRENT < C/10 FOR 3SEC

BAT

< V

MAX

FOR MORE THAN 1SEC

BAT

< V

MAX

FOR MORE THAN 1SEC

BAT

> V

MAX

FOR MORE THAN 1SEC

BAT

> V

MAX

FOR MORE THAN 1SEC

NTC

> 2.79V OR

NTC

< 0.405V V

NTC

< 2.79V AND

NTC

> 0.405V

BAT

> V

MIN

BAT

< V

MIN

CHARGER “ON”

BAT

= 1.3mA

STATUS = PULL-DOWN

= OPEN

MAX

= 3HR

CHARGE

Figure 6. State Diagram

LTC1729 Series

Status Output Pin

The STATUS pin is designed to provide an indication that

the battery is charging. Once the current drops below the

C/10 threshold, the battery is close to being fully charged.

The LTC1729 turns off the hard pull-down once the

C/10 comparator is active for more than three seconds.

The 50µA soft pull down remains in effect until the 3-hour

time-out is completed or the input power is removed.

By using two different value pull-up resistors, a micropro-

cessor can detect three states from this pin (charging,

C/10 and stop charging). See Figure 7.

Second, if the battery is removed from the charger, the

MAX

signal is activated as mentioned in the Block Dia-

gram section. This causes the state machine to make the

BAT

> V

MAX

transition to the Pause state. The third way to

exit the charger “ON” state is with a V

BAT

< V

MIN

transition

to the Precondition state. The battery will need to drop

below 2.6V/cell to be less than V

MIN

. This is not a likely

scenario.

Once in the Pause state, there are two ways to proceed.

The first is to go to the No Bat state. This requires that the

BAT

remain greater than V

MAX

for more than one

second. From these conditions, the LTC1729 interprets

that a battery has been removed. If the voltage on the BAT

pin stays less than V

MAX

for more than one second, then

the state machine returns to the Charge state (Precondi-

tion and charger “ON”). This is interpreted as a momentary

open caused by the battery pack protection circuitry or

loose contact.

The Done state can only proceed to the No Bat state. From

outside the LTC1729 this transition is undetectable. The

requirement for this transition is for the BAT pin voltage to

exceed V

MAX

for more than one second. The IC now

assumes that the battery has been removed.

From the No Bat state, there is only one possible transition.

The No Bat state can move to the Charge state if the voltage

on the BAT pin remains less than V

MAX

for one second. The

LTC1729 will now work on the assumption that a new

battery has been installed.

Although the Precondition and Charger “ON” both reside

in the Charge state, there are differences between these

states. The main purpose of the Precondition state is to

slowly bring a heavily discharged battery up to a minimum

level before full charge current begins. The Precondition

state uses a 12mA current source to trickle charge the

battery with a 1-hour time-out transition to the Done state.

The Charger “ON” state enables the external charger and

the time-out is increased to three hours. For the entire

time in the Precondition state, the STATUS pin uses a hard

pull-down. In the Charger “ON” state the STATUS pin uses

two types of pull-down: hard pull-down and soft 50µA

pull-down.

APPLICATIO S I FOR ATIO

WUUU

200k

STATUS

1729 F07

LTC1729

OUT

µPROCESSOR

Figure 7. Microprocessor Interface

When the LTC1729 is in charge mode, the STATUS pin is

pulled down by an internal N-channel MOSFET. To detect

this mode, force the digital output pin, OUT, high and

measure the voltage at the STATUS pin. The N-channel

MOSFET will pull the pin low even with a 3k pull-up resis-

tor. Once the charge current drops to 10% of the full-scale

current (C/10), the N-channel MOSFET is turned off and a

50µA current source is connected to the STATUS pin. The

IN pin will then be pulled high by the 3k pull-up. By forcing

the OUT pin into a high impedance state, the current

source will pull the pin low through the 200k resistor.

When the internal timer has expired, the STATUS pin will

change to high impedance state and the 200k resistor will

then pull the pin high to indicate the charging has stopped.

Terminate at C/10 Current

Charging can also be terminated using C/10 detection

before the 3-hour time-out. By connecting the low side of

the NTC thermistor to the STATUS pin instead of ground,

LTC1729 Series

APPLICATIO S I FOR ATIO

WUUU

Figure 8. Terminate Charging at C/10

Figure 9. Modify C/10 Indication to Create Charging Indicator

OVP

BAT

SENSE

GND

OVP

BAT

SENSE

STATUS

NTC

LTC1729-4.2

1µF

0.1µF

1729 F08

10k NTC THERMISTOR

NTHS1206N02 VISHAY/DALE

200Ω

100µA

1729 F09

–

COMP1

LTC1729

SENSE

BIAS

BAT

–

SENSE

RESISTOR

CHARGE

CURRENT

the NTC pin will float to 5V as soon as the Status pull-down

is open. This will force the state machine into the Hold

mode. The V

pin is pulled low which turns off the charger.

This circuit is shown in Figure 8.

In order to restart the charging process for a new battery,

the NTC pin will need to be momentarily brought below

0.2V or the V

pin brought below the UVLO threshold.

The automatic battery detection features are disabled

during the Hold mode.

Using Status as a Charging Indicator

In many applications circuits shown in this data sheet, the

STATUS pin is used to indicate when C/10 has occurred

(charge current has dropped to 10% of the full charge

current). This C/10 number is not fixed, but is set by an

external resistor connected to the LTC1729 SENSE pin. A

100µA bias current through this resistor develops a volt-

age which is compared with the voltage across the charge

current sense resistor. When these voltages are equal, the

open-drain STATUS pin turns off. Connecting an LED to

the STATUS pin will give a visual indication during the

precondition trickle charge and the portion of the main

charge before C/10 has occurred.

By reducing the LTC1729 SENSE pin resistor to 0Ω, the

STATUS pin function can be changed to a

charging indica-

tor

(Figure 9). The LED on the STATUS pin will always go

off after the 3-hour charge cycle is completed, regardless

of the C/10 circuitry.

LTC1729 Series

Wide Input Voltage Range 1A Charger

OVP

BAT

SENSE

GND

STATUS

NTC

S/S

GND V

LTC1729-8.4

BOOST

CAP

GND

CAP

–

OSC

OUT

LTC1044

LT1512

0.33µF

22µF

×2

Si9925

0.1Ω

29.4k

1/2 BAT85S

10µF

12.4k

L1**

1µF

1729 TA01

* TOKIN CERAMIC 1E225ZY5U-C203-F

** L1, L2 ARE TWO 10µH INDUCTORS: SUMIDA CDRH6D38-100

R8:10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE

NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

470Ω

C2*

4.7µF

100Ω

R4 39Ω

L2**

22µF

ON/OFF

10µF

0.1µF

MBRS340

3V TO 28V

0.1Ω

PULL-UP

47k

8.4V

220k

TYPICAL APPLICATIO S

STATUS

NTC

LTC1729

2.2k 0.1µF

TO V

12V

10k

AMBER LEDPNP: MMBT3906

2k4.7k

47k

GREEN LED

CONDITION

NO WALL ADAPTER

CHARGING (I

BAT

> C/10)

CHARGING (I

BAT

< C/10)

TIMER EXPIRED

AMBER

OFF

GREEN

OFF

1729 TA03

Using STATUS Pin to Indicate Charge Status

LTC1729 Series

4A, 2-Cell Lithium-Ion Battery Charger

TYPICAL APPLICATIO S

CLN

CLP

INFET

SYNC

SHDN

FLAG

CAP

COMP1

GBIAS

TGATE

BGATE

PROG

3 CELL

4.2V

4.1V

AGND

PGND

SYSTEM

LOAD

BAT2 BAT SENSE SPIN

PROG

4.93k

PROG

1µF

BOOST BOOSTC

OVP

BAT

SENSE

GND

STATUS

NTC

LTC1729-8.4

LT1505

47µF

35V

OPTION: TIE RESISTOR TO STATUS FOR

CHARGE TERMINATION AT

LOW CHARGING CURRENT

* SANYO OS-CON

** SUMIDA CDRH127-150

*** AVX TPSD226L025R0200

†

C6 NOT NEEDED IF FLAG NOT USED

††

LUMEX SML-LX0805GW-TR

0.025Ω

200Ω

0.025Ω

Si4435

DBODY

(FROM

ADAPTER) R7

500Ω

3kC5

0.33µF

5.1k

200Ω

1µF

8.4V

††

OUT

***

22µF

× 2

0.1µF

0.68µF

2.2µF

0.1µF

Si4412

MMSD4148

L1**

15µH

MBRS140

5Ω

0.68µF

300Ω

†

0.1µF

100Ω

1.4k

PULL-UP

10k

1729 TA02

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE

NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

LTC1729 Series

MS8 Package

8-Lead Plastic MSOP

(LTC DWG # 05-08-1660)

MSOP (MS8) 1098

* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,

PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

0.021 ± 0.006

(0.53 ± 0.015)

0° – 6° TYP

SEATING

PLANE

0.007

(0.18)

0.040 ± 0.006

(1.02 ± 0.15)

0.012

(0.30)

REF

0.006 ± 0.004

(0.15 ± 0.102)

0.034 ± 0.004

(0.86 ± 0.102)

0.0256

(0.65)

BSC

0.193 ± 0.006

(4.90 ± 0.15)

8765

0.118 ± 0.004*

(3.00 ± 0.102)

0.118 ± 0.004**

(3.00 ± 0.102)

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTIO

LTC1729 Series

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.016 – 0.050

(0.406 – 1.270)

0.010 – 0.020

(0.254 – 0.508)× 45°

0°– 8° TYP

0.008 – 0.010

(0.203 – 0.254)

SO8 1298

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

TYP

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

1234

0.150 – 0.157**

(3.810 – 3.988)

8765

0.189 – 0.197*

(4.801 – 5.004)

0.228 – 0.244

(5.791 – 6.197)

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

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 represen-

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

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTIO

LTC1729 Series

1729f LT/LCG 0800 4K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1999

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

●

FAX: (408) 434-0507

●

www.linear-tech.com

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LT1510 Constant-Voltage/Constant-Current Battery charger Up to 1.5A Charge Current for Lithium-Ion, NiCd and

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SENSE

LT1511 3A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries

LT1512 SEPIC Battery Charger V

Can Be Higher or Lower Than Battery Voltage, 2A Switch

LT1513 SEPIC Battery Charger V

Can Be Higher or Lower Than Battery Voltage, 3A Switch

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3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger

TO MAIN

SYSTEM

LOAD

BATSENSE

OVP

BAT

SENSE

GND

STATUS

NTC

LTC1729-8.4

LT1511 OR LT1769

OPTION: TIE RESISTOR TO STATUS FOR

CHARGE TERMINATION AT

LOW CHARGING CURRENT

* TOKIN C55Y5U1E156Z

** SUMIDA CDRH125-220MC

*** AVX TPSD226K025R0200

†

LUMEX SML-LX0805GW-TR

D1, D2, D4: GENERAL SEMICONDUCTOR

510Ω

200Ω

1% R

0.05Ω

300Ω

GND CLP

CLN

PROG

BOOST

COMP1

SPIN

OVP

0.1µF

5.1K

SS24 D2

SS24

220pF

1.4k

200Ω

0.47µF

8.4V

†

1729 TA04

PROG

4.93k

PROG

1µF

C1*

15µF

0.33µF

MBR0540T

L1**

22µH

1µF

C7***

22µF

100Ω

SS24 INPUT POWER

11.5V TO 28V

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE

NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

1µF

TYPICAL APPLICATIO