Datasheet LTC1729 Datasheet (Linear Technology)

FEATURES

Final Electrical Specifications

■

Trickle Charge Preconditioning If Cell <2.7V

■

Charging Enabled When 0°C < T < 50°C

■

Built-In Termination: 3-Hour Time-Out

■

C/10 Detection with Status Indicator

■

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

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APPLICATIONS

■

Cellular Phones

■

PDAs

■

Cradle Chargers

■

Camcorders

LTC1729 Series

Li-Ion Battery Charger

Termination Controllers

October 1999

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DESCRIPTION

The LTC®1729 series is a family of smart
controllers for lithium-ion battery chargers. These ICs
provide trickle charge preconditioning, temperature charge
qualification, time or charge current termination, auto­matic 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 termi­nation 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.

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

termination

TYPICAL APPLICATION

MBRM120T3

0.22µF

L1**
10µH

MMBD914L

200Ω

* 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

1µF

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SW

LT1510-5

BOOST
GND
OVP

SENSE

1

OVP

2

BAT

LTC1729-4.2

3

SENSE

4

GND

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

V

PROG

BAT

V

STATUS

NTC

CC

1µF

V

C

0.1µF

8

CC

7

V

C

6

5

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

OPTION: TIE RESISTOR TO STATUS FOR
CHARGE TERMINATION AT
LOW CHARGING CURRENT

300Ω

C

OUT

22µF

0.1µF

6.19k

1k

+

***

4.2V

+

MBRM120T3

CIN*
10µF

1729 F01

1.4k

†

D1
CHARGE STATUS

INPUT POWER

8.2V TO 20V

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.

1

LTC1729 Series

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ABSOLUTE MAXIMUM RATINGS

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(Note 1)

VCC......................................................................... 30V

SENSE, V

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

BAT

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

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

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PACKAGE/ORDER INFORMATION

ORDER PART

TOP VIEW

OVP

1

BAT

2

SENSE

3

GND

4

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

= 150°C, θJA = 200°C/W

JMAX

8

V

7

V

6

STATUS

5

NTC

CC
C

NUMBER

LTC1729CMS8-4.1
LTC1729CMS8-4.2
LTC1729CMS8-8.2
LTC1729CMS8-8.4

MS8 PART MARKING

LTLY
LTJH
LTLZ
LTJG

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

ORDER PART

1

OVP

BAT

2

SENSE

3

GND

4

8-LEAD PLASTIC SO

T

= 150°C, θJA = 150°C/W

JMAX

TOP VIEW

S8 PACKAGE

8

7

6

5

V

CC

V

C

STATUS
NTC

NUMBER

LTC1729CS8-4.1
LTC1729CS8-4.2
LTC1729CS8-8.2
LTC1729CS8-8.4

S8 PART MARKING

172941
172942
172982
172984

Consult factory for Industrial and Military grade parts.

ELECTRICAL CHARACTERISTICS

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
DC CHARACTERISTICS

I

VIN

V

LKOH

V

LKOL

I

VBAT

V

CLAMP

V

MAX

V

MIN

I

SENSE

V

C10

VCC Supply Current VIN = 5V (Below UVLO) ● 1512 µA

V

= 8V, 200µA Pull-Up on V

IN

= 8V, V

V

IN

VIN = 8V, V
VIN Undervoltage Lockout High ● 5.5 6.5 7.5 V
VIN Undervoltage Lockout Low ● 5.0 6.0 7.0 V
V

Current VIN = 5V (Below UVLO), V

BAT

V

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

BAT

High V

Low V

SENSE Pin Current Charge State, V
SENSE Pin C/10 Offset Charge State, V

Threshold High Going Threshold ● 4.25 4.51 4.75 V

BAT

Threshold High Going Threshold ● 2.55 2.7 2.85 V

BAT

= 8V, V

V

IN

= 8V, V

V

IN

VIN = 8V, V

Low Going Threshold ● 4.25 4.50 4.75 V

Low Going Threshold ● 2.45 2.6 2.75 V

= 2.5V Trickle 10 17 21 mA

BAT

= 3.5V Charge ● 0.5 3.0 5.0 mA

BAT

= 4.25V No Bat ● 40 73 120 µA

BAT

= 2.5V Trickle – 19 –16 –9.5 mA

BAT

= 3.5V Charge ● –2.7 – 1.3 – 0.5 mA

BAT

= 3V ● 85 100 115 µA

SENSE

= (V

C10

BAT

(4.5V) No Bat ● 1.0 1.4 2.0 mA

BAT

= 4.2V ● –1 –0.1 1 µA

BAT

) ● 4.25 4.5 4.75 V

BAT

– V

) ● ±1 ±2.5 mV

SENSE

2

LTC1729 Series

ELECTRICAL CHARACTERISTICS

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

I

NTC

V

NTC-RESET

V

NTC-HOT

V

NTC-COLD

V

OVP

V

OL-ST

V

OL-VC

I

SOFT

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS

I

VIN

V

LKOH

V

LKOL

I

VBAT

V

CLAMP

V

MAX

V

MIN

I

SENSE

V

C10

I

NTC

V

NTC-RESET

V

NTC-HOT

V

NTC-COLD

V

OVP

V

OL-ST

V

OL-VC

I

SOFT

NTC Pin Current V

= 1V ● 90 100 110 µA

NTC

Thermistor Pin Reset Threshold ● 0.160 0.206 0.240 V
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
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 Pin Voltage V

= 4.1V or V

BAT

= 4.2V ● 2.455 2.465 2.475 V

BAT

2.460 2.465 2.470 V
Output Low Voltage-STATUS Pin IO = 3mA ● 0.5 0.9 1.2 V
Output Low Voltage-VC Pin IO = 1mA ● 0.35 0.6 0.75 V
Status Soft Pull-Down Current V

= 4.5V ● 40 50 65 µA

STATUS

LTC1729-8.2/LTC1729-8.4

VCC Supply Current VIN = 9V (Below UVLO) ● 1612 µA

V

= 12V, 200µA Pull-Up on V

IN

= 12V, V

V

IN

VIN = 12V, V

= 5V Trickle 10 17 21 mA

BAT

= 7V Charge ● 0.5 3.0 5.0 mA

BAT

(9V) No Bat ● 1.0 1.4 2.0 mA

BAT

VIN Undervoltage Lockout High ● 9.5 10.4 11.4 V
VIN Undervoltage Lockout Low ● 8.5 9.6 10.5 V
V

Current VIN = 9V (Below UVLO), V

BAT

V

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

BAT

High V

Threshold High Going Threshold ● 8.5 9.013 9.5 V

BAT

= 12V, V

V

IN

= 12V, V

V

IN

VIN = 12V, V

= 8.5V No Bat ● 60 95 140 µA

BAT

= 5V Trickle – 19 – 16 –9.5 mA

BAT

= 7V Charge ● –2.7 – 1.3 – 0.5 mA

BAT

= 8.4V ● –1 –0.1 1 µA

BAT

) ● 8.5 9 9.5 V

BAT

Low Going Threshold ● 8.5 9 9.5 V

Low V

Threshold High Going Threshold ● 5.1 5.4 5.7 V

BAT

Low Going Threshold ● 4.9 5.2 5.5 V

SENSE Pin Current Charge State, V
SENSE Pin C/10 Offset Charge State, V
NTC Pin Current V

= 1V ● 90 100 110 µA

NTC

= 7V ● 85 100 115 µA

SENSE

= (V

C10

BAT

– V

) ● ±1 ±2.5 mV

SENSE

Thermistor Pin Reset Threshold ● 0.160 0.206 0.240 V
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

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 Pin Voltage V

= 8.2V or V

BAT

= 8.4V ● 2.455 2.465 2.475 V

BAT

2.460 2.465 2.470 V
Output Low Voltage-STATUS Pin IO = 3mA ● 0.5 0.9 1.2 V
Output Low Voltage-VC Pin IO = 1mA ● 0.35 0.6 0.75 V
Status Soft Pull-Down Current V

= 4.5V ● 40 50 65 µA

STATUS

3

LTC1729 Series

ELECTRICAL CHARACTERISTICS

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

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
TIMER4 Timer for V
T

OSC

Oscillator Period ● 6.66 7.63 9.09 µs

Filter ● 0.764 0.859 1.043 sec

MAX

Filter ● 3.055 3.5 4.17 sec

C/10

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

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PIN FUNCTIONS

OVP (Pin 1): Output from an Internal Precision Resistor
Divider Used as a Voltage Feedback Monitor for Constant­Voltage 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 VCC is below the undervoltage lockout thresh­old. During trickle charge preconditioning and charging
the BAT pin sources 16mA 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 VC pin and the current sources on BAT
and SENSE pins are turned off. The STATUS pin is not
affected.

Note 2: VIN = 8V for LTC1729-4.1/LTC1729-4.2; VIN = 12V for
LTC1729-8.2/LTC1729-8.4

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 while the V

CC

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 pull­down 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.

VC (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.

VCC (Pin 8): Input Supply. For 4.1V or 4.2V single cell
operation, VCC should be between 8V and 28V with the IC
turning off when VCC drops below 6V. For 2-cell applica­tions, the undervoltage lockout is 10.4V with a minimum
VCC of 12V. Removing the wall adapter will trigger an
undervoltage lockout and put the part in a high impedance
condition. When the supply is connected, the part is
initialized in the Reset mode with the state machine forced
in the Charge state with all the timers set to zero.

4

BLOCK DIAGRA

3

SENSE

–

COMP1

+

BAT

2

UVLO

M1

2.465V

OVP

1

W

1.3mA

100µA

UVLO

16mA

4.5V/CELL
CLAMP

4.5V/CELL

2.7V/CELL

+

–

+

–

COMP2

COMP3

C/10

V

MAX

V

MIN

HOLD

LOGIC

AND

TIMER

LTC1729 Series

V

7

C

M2

6

STATUS

M3

50µA

NTC

100µA

5

2.79V

0.405V

0.2V

+

–

+

–

+

–

COMP4

COMP5

COMP6

Figure 2. Block Diagram

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APPLICATIONS INFORMATION

Overview

The LTC1729 is a charge termination controller for the
LT1505/LT1510/LT1511/LT1512/LT1513/LT1769 con­stant-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 constant­voltage/constant-current charging. The secondary func­tion 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 only
needs six external components when combined with the

RESET

1729 F02

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

5

LTC1729 Series

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APPLICATIONS INFORMATION

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.

The comparator COMP1 is used to indicate C/10 charge
current 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
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

= true to the

MAX

the VC pin, reducing the duty cycle of the charger. If the
battery protection circuit quickly returns battery connec­tion to the charger (in less than one second), then the
LTC1729 continues charging without resetting the timers.

For a battery that has been over-discharged, the LTC1729
provides a 16mA 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.

6

20mV

+
–

CHARGING
CURRENT

R1

0.2Ω

+

20mV

R2

200Ω

V

CC

I

BIAS

C1
1µF

SENSE

BAT

Figure 3. C/10 Detection Circuit

–

–

COMP1

+

100µA

3-SEC

FILTER

LOGIC

AND

TIMERS

LTC1729

STATUS

50µA

CHARGE
LED

1729 F03

LTC1729 Series

RESET MODE

I

BAT

= 0

STATUS = PULL-DOWN

V

C

= PULL-DOWN

PAUSE

I

BAT

= 0

STATUS = PULL-DOWN

V

C

= PULL-DOWN

DONE

I

BAT

= 0

STATUS = OPEN

V

C

= PULL-DOWN

NO BAT

I

BAT

= 0

STATUS = OPEN

V

C

= PULL-DOWN

HOLD MODE

I

BAT

= 0

STATUS = PREVIOUS STATUS

V

C

= PULL-DOWN

PRECONDITION

I

BAT

= 16mA

STATUS = PULL-DOWN

V

C

= PULL-DOWN

t

MAX

= 1HR

V

BAT

< V

MIN

V

BAT

> V

MIN

V

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

V

BAT

< V

MAX

FOR MORE THAN 1SEC

V

BAT

< V

MAX

FOR MORE THAN 1SEC

V

BAT

> V

MAX

FOR MORE THAN 1SEC

V

BAT

> V

MAX

FOR MORE THAN 1SEC

V

NTC

> 2.79V OR

V

NTC

< 0.405V

V

NTC

< 2.79V AND

V

NTC

> 0.405V

V

BAT

> V

MIN

V

BAT

< V

MIN

CHARGER “ON”

I

BAT

= 1.3mA

STATUS = PULL-DOWN

V

C

= OPEN

t

MAX

= 3HR

CHARGE

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APPLICATIONS INFORMATION

V

= 1V

= 0V

= 0V

= 0V

= 0V

= 1V

BATTERY CLAMP
PULL-DOWN
ON

NORMAL CHARGE

TRICKLE CHARGE
PRECONDITIONING

1729 F04

MAX

V

MIN

4.5V/CELL

V

MAX

V

MIN

2.7V/CELL

BATTERY VOLTAGE

V

MAX

V

MIN

Figure 4. BAT Voltage Operating Range

HOLD MODE

2.79V

NORMAL CHARGE

Figure 5. NTC Voltage Operating Range

When the input supply is removed in step-down charger
designs, the VCC 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 VCC pin that
is present in the LT1510, LT1511, LT1769, and the body
diode of the top MOSFET in the LT1505 charger. Removing
the input supply will result in the VCC 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
VCC voltage drops below the UVLO threshold.

0.405V

HOLD MODE

THERMISTOR VOLTAGE

0.2V

RESET MODE

1729 F05

Figure 6. State Diagram

The logic and timer block consists of a state machine,
oscillator and counter. The state machine will be dis­cussed 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.

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.

7

LTC1729 Series

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APPLICATIONS INFORMATION

3. When a heavily 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 (VC 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
Second, if the battery is removed from the charger, the
V

signal is activated as mentioned in the Block Dia-

MAX

gram section. This causes the state machine to make the
V

> V

BAT

exit the charger “ON” state is with a V
to the Precondition state. The battery will need to drop
below 2.6V/cell to be less than V
scenario.

transition to the Pause state. The third way to

MAX

transition to the Done state.

MAX

< V

BAT

. This is not a likely

MIN

transition

MIN

requirement for this transition is for the BAT pin voltage to
exceed V
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
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 16mA 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.

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.

Terminate at C/10 Current

for more than one second. The IC now

MAX

for one second. The

MAX

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
V

remain greater than V

BAT

second. From these conditions, the LTC1729 interprets
that a battery has been removed. If the voltage on the BAT
pin stays less than V
the state machine returns to the Charge state (Precondi­tion 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

for more than one second, then

MAX

for more than one

MAX

8

Charging can also be terminated using C/10 detection
rather than the 3-hour time-out. By connecting the low
side of the NTC thermistor to the STATUS pin instead of
ground, 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 VC pin is pulled low which turns off the
charger. This circuit is shown in Figure 7.

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 VCC pin brought below the UVLO threshold.
The automatic battery detection features are disabled
during the Hold mode.

LTC1729 Series

U

WUU

APPLICATIONS INFORMATION

LTC1729-4.2

1

1µF

2

3

4

OVP

BAT

SENSE

GND

OVP

BAT

SENSE

200Ω

Figure 7. Terminate Charging at C/10

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

8

V

CC

7

V

V

C

C

6

STATUS

5

NTC

10k NTC THERMISTOR

NTHS1206N02 VISHAY/DALE

0.1µF

1729 F07

V

CC

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

tor

(Figure 8). The LED on the STATUS pin will always go

charging indica-

off after the 3-hour charge cycle is completed, regardless
of the C/10 circuitry.

CHARGE
CURRENT

I

BIAS

+
–

SENSE
RESISTOR

SENSE

BAT

–

COMP1

+

Figure 8. Modify C/10 Indication to Create Charging Indicator

LTC1729

100µA

1729 F08

U

TYPICAL APPLICATIONS

V

IN

LT1512

V

C

STATUS

R5
1k

L1A**

V

V

I

C5

0.1µF

V

NTC

SW

FB
FB

CC

V

C

INPUT POWER

4V TO 9V

R7

C6

100Ω

1µF

22µF

C3

S/S

GND

OVP

BAT

LTC1729-4.2

SENSE

GND

SEPIC Charger with 0.5A Output Current

C2*

2.2µF

R4, 24Ω

C4

0.22µF

D1

MBRS130LT3

L1B**

R3

0.2Ω

C7
10µF

R8
10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

OPTION: TIE R8 TO STATUS FOR
CHARGE TERMINATION AT
LOW CHARGING CURRENT

R6

0.2Ω

C1

22µF

R1

29.4k

R2

12.4k

R

PULLUP

10k

R9
1k

†

D4

+

* TOKIN CERAMIC 1E225ZY5U-C203-F

** L1A, L1B ARE TWO 33µH WINDINGS ON A

SINGLE INDUCTOR; COILTRONICS CTX33-3

†

LUMEX SML-LX0805GW-TR SIZE R9 FOR
20mA TYPICAL

BOOST

CAP

4.2V

GND

CAP

FOR 3.5V TO 14V USE LTC1144

+

LTC1044

–

V

OSC

OUT

+

V

LV

1/2 BAT85S

+

D2
1/2 BAT85S

C8
10µF

D3

1729 F11

9

LTC1729 Series

TYPICAL APPLICATIONS

TO

V

(FROM

ADAPTER)

IN

5.1k

DBODY

M3

Si4435

R7

500Ω

R5

3k

R6

R

0.025Ω

1µF

C6

0.1µF

C1

S4

SYSTEM

POWER

R1
1k

C7

0.68µF

C

*

IN

47µF

V

35V

CC

CLN
CLP
INFET
UV
SYNC
SHDN
FLAG
CAP
COMP1

BAT2 BAT SENSE SPIN

U

4A, 2-Cell Lithium-Ion Battery Charger

BOOST

LT1505

BOOSTC

GBIAS

TGATE

BGATE

PROG

3 CELL

AGND
PGND

SW

V

4.2V

4.1V

V

C

FB

C3

2.2µF

R

4.93k
1%

5Ω

MMSD4148

PROG

D2

R3
300Ω

C
1µF

R4
3k

PROG

C5

0.33µF

M1
Si4412

M2
Si4412

C4

0.1µF

D3

MMSD4148

D4
MBRS140

C2

0.68µF

L1**

15µH

R

S1

0.025Ω

R

S2

200Ω
1%

R

S3

200Ω
1%

C

OUT

22µF
× 2

***

+

8.4V

R8

100Ω

* SANYO OS-CON

** SUMIDA CDRH127-150

*** AVX TPSD226L025R0200

†

LUMEX SML-LX0805GW-TR

C8

0.1µF

OVP

BAT

LTC1729-8.4

SENSE

GND

V

STATUS

NTC

R

PULL-UP

10k

CC

V

C

C9

0.1µF

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

OPTION: TIE RESISTOR TO STATUS FOR
CHARGE TERMINATION AT
LOW CHARGING CURRENT

R9

1.4k

†

D5

1729 F09

10

PACKAGE DESCRIPTION

(

0.007
(0.18)

0.021 ± 0.006
(0.53 ± 0.015)

* 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° – 6° TYP

U

Dimensions in inches (millimeters) unless otherwise noted.

MS8 Package

8-Lead Plastic MSOP

(LTC DWG # 05-08-1660)

0.118 ± 0.004*
(3.00 ± 0.102)

0.193 ± 0.006

(4.90 ± 0.15)

SEATING

PLANE

0.040 ± 0.006
(1.02 ± 0.15)

0.012

(0.30)

0.0256

REF

(0.65)

BSC

0.152mm) PER SIDE

0.034 ± 0.004

(0.86 ± 0.102)

0.006 ± 0.004

(0.15 ± 0.102)

LTC1729 Series

8

7

6

5

0.118 ± 0.004**
(3.00 ± 0.102)

MSOP (MS8) 1098

12

4

3

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.228 – 0.244

(5.791 – 6.197)

0.010 – 0.020

(0.254 – 0.508)

0.008 – 0.010

(0.203 – 0.254)

*

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

× 45°

0°– 8° TYP

0.016 – 0.050

(0.406 – 1.270)

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

TYP

0.189 – 0.197*
(4.801 – 5.004)

7

8

1

2

5

6

0.150 – 0.157**
(3.810 – 3.988)

3

4

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

SO8 1298

11

LTC1729 Series

TYPICAL APPLICATION

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

U

0.47µF

L1**

22µH

100Ω

R

S4

0.05Ω

R7

1.4k

D5

D1

SS24

†

D2
SS24

R5
3k

R6

5.1K

INPUT POWER

11.5V TO 28V

TO MAIN
SYSTEM
POWER

R1

C
1µF

R3
300Ω

8.4V

PROG

510Ω

R

4.93k

PROG

GND CLP

R

S1

STATUS

CLN

V

PROG

BATSENSE

V

CC

V

CC

UV

V

C

R

S3

200Ω
1%

C

+

C1*
15µF

C4

0.33µF

R2
1k

C7***
22µF

C6

0.1µF

+

SW

D3
MBR0540T

D4
SS24

C3
200pF

C5
1µF

200Ω

LT1511 OR LT1769

BOOST

COMP1

SPIN
OVP

R

S2

0.05Ω

1%

OVP

BAT

LTC1729-8.4

SENSE

C2

R4

* TOKIN C55Y5U1E156Z

** SUMIDA CDRH125-220MC

*** AVX TPSD226K025R0200

†

LUMEX SML-LX0805GW-TR

D1, D2, D4: GENERAL SEMICONDUCTOR

GND

NTC

10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT

OPTION: TIE RESISTOR TO STATUS FOR
CHARGE TERMINATION AT
LOW CHARGING CURRENT

1729 F10

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LT1505 High Efficiency Constant-Voltage/Constant-Current Battery Charger Uses External Synchronous N-Channel FETs
LT1510 Constant-Voltage/Constant-Current Battery charger Up to 1.5A Charge Current for Lithium-Ion, NiCd and

NiMH Batteries, Internal R
LT1511 3A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries
LT1512 SEPIC Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 2A Switch
LT1513 SEPIC Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 3A Switch
LTC1759 SMBus-Controlled Smart Battery Charger LT1505 Charger Functionality with SMBus Control
LT1769 2A Constant-Voltage/Constant-Current Battery Charger In 28-Pin SSOP Package

SENSE

12

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com

1729i LT/TP 1099 4K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1999