1
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
V
CC
V
C
STATUS
NTC
SW
SENSE
OVP
GND
BOOST
PROG
V
C
BAT
1
2
3
4
8
7
6
5
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
1k
C
OUT
***
22µF4.2V
200Ω
300Ω6.19k
+
C
IN
*
10µF
MBRM120T3 INPUT POWER
8.2V TO 20V
D1
†
CHARGE STATUS
MBRM120T3
MMBD914L
V
CC
1.4k
+
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1729 Series
LTC1729CMS8-4.1
LTC1729CMS8-4.2
LTC1729CMS8-8.2
LTC1729CMS8-8.4
T
JMAX
= 150°C, θ
JA
= 150°C/W
ORDER PART
NUMBER
V
CC
......................................................................... 30V
SENSE, V
BAT
, NTC .................................... –0.3V to 15V
V
C
............................................................. –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
1
2
3
4
OVP
BAT
SENSE
GND
8
7
6
5
V
CC
V
C
STATUS
NTC
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C, θ
JA
= 200°C/ W
MS8 PART MARKING
LTLY
LTJH
LTLZ
LTJG
TOP VIEW
OVP
BAT
SENSE
GND
V
CC
V
C
STATUS
NTC
S8 PACKAGE
8-LEAD PLASTIC SO
1
2
3
4
8
7
6
5
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
I
CC
V
CC
Supply Current V
IN
= 5V (Below UVLO) ●1512 µA
V
IN
= 8V, V
BAT
> 4.5V, No Bat ●1.0 1.4 2.0 mA
V
IN
= 8V, V
BAT
= 2.5V Trickle 10 17 21 mA
V
IN
= 8V, V
BAT
= 3.5V Charge ●0.5 3.0 5.0 mA
V
LKOH
V
IN
Undervoltage Lockout High ●5.5 6.5 7.5 V
V
LKOL
V
IN
Undervoltage Lockout Low ●5.0 6.0 7.0 V
I
VBAT
V
BAT
Current V
IN
= 5V (Below UVLO), V
BAT
= 4.2V ●–1 –0.1 1 µA
V
IN
= 8V, V
BAT
= 4.25V No Bat ●40 73 120 µA
V
IN
= 8V, V
BAT
= 2.5V Trickle –19 –12 –9.5 mA
V
IN
= 8V, V
BAT
= 3.5V Charge ●–2.7 –1.3 –0.5 mA
V
CLAMP
V
BAT
Clamp No Bat (External 200µA Pull-Up on V
BAT
)●4.25 4.5 4.75 V
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
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
I
SENSE
SENSE Pin Current Charge State, V
SENSE
= 3V ●85 100 115 µA
V
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
UU
W
ELECTRICAL CHARACTERISTICS
3
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
I
NTC
NTC Pin Current V
NTC
= 1V ●90 100 110 µA
V
NTC-RESET
Thermistor Pin Reset Threshold ●0.160 0.206 0.240 V
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
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
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
V
OL-ST
Output Low Voltage-STATUS Pin I
O
= 3mA ●0.5 0.9 1.2 V
V
OL-VC
Output Low Voltage-V
C
Pin I
O
= 1mA ●0.35 0.6 0.75 V
I
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
I
CC
V
CC
Supply Current V
IN
= 9V (Below UVLO) ●1612 µA
V
IN
= 12V, V
BAT
> 9V, No Bat ●1.0 1.4 2.0 mA
V
IN
= 12V, V
BAT
= 5V Trickle 10 17 21 mA
V
IN
= 12V, V
BAT
= 7V Charge ●0.5 3.0 5.0 mA
V
LKOH
V
IN
Undervoltage Lockout High ●9.5 10.4 11.4 V
V
LKOL
V
IN
Undervoltage Lockout Low ●8.5 9.6 10.5 V
I
VBAT
V
BAT
Current V
IN
= 9V (Below UVLO), V
BAT
= 8.4V ●–1 –0.1 1 µA
V
IN
= 12V, V
BAT
= 8.5V No Bat ●60 95 140 µA
V
IN
= 12V, V
BAT
= 5V Trickle –19 –12 –9.5 mA
V
IN
= 12V, V
BAT
= 7V Charge ●–2.7 –1.3 –0.5 mA
V
CLAMP
V
BAT
Clamp No Bat (External 200µA Pull-Up on V
BAT
)●8.5 9 9.5 V
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
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
I
SENSE
SENSE Pin Current Charge State, V
SENSE
= 7V ●85 100 115 µA
V
C10
SENSE Pin C/10 Offset Charge State, V
C10
= (V
BAT
– V
SENSE
)●±1±2.5 mV
I
NTC
NTC Pin Current V
NTC
= 1V ●90 100 110 µA
V
NTC-RESET
Thermistor Pin Reset Threshold ●0.160 0.206 0.240 V
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
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
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
V
OL-ST
Output Low Voltage-STATUS Pin I
O
= 3mA ●0.5 0.9 1.2 V
V
OL-VC
Output Low Voltage-V
C
Pin I
O
= 1mA ●0.35 0.6 0.75 V
I
SOFT
Status Soft Pull-Down Current V
STATUS
= 4.5V ●40 50 65 µA
4
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
IN
= 8V for LTC1729-4.1/LTC1729-4.2; V
IN
= 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
t
OSC
Oscillator Period ●6.66 7.63 9.09 µs
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
UW
IVBAT vs Temperature (4.2V Version)
TEMPERATURE (°C)
0
8
10
14
75
1729 G01
6
4
25 50 100
2
0
12
I
VBAT
(mA)
V
BAT
= 2.5V
TEMPERATURE (°C)
0
8
10
14
75
1729 G02
6
4
25 50 100
2
0
12
I
VBAT
(mA)
V
BAT
= 5V
V
CC
(V)
6
14
12
10
8
6
4
2
018 26
1729 G03
10 14 22 30
I
VBAT
(mA)
V
BAT
= 3.5V
V
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
CC
(V)
10
0
I
VBAT
(mA)
2
4
6
8
10
12
14 18 22 26
1729 G04
30
V
BAT
= 5V
V
BAT
= 7V
ICC vs VCC (4.2V Version)
VCC (V)
6
2
ICC (mA)
4
6
8
10
14
10 14 18 22
1729 G05
26 30
12 VBAT = 2.5V
VBAT = 3.5V
V
CC
(V)
10
2
I
CC
(mA)
4
6
8
10
12
14
14 18 22 26
1729 G06
30
V
BAT
= 5V
V
BAT
= 7V
5
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
CC
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
C
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
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 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.
V
C
(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.
V
CC
(Pin 8): Input Supply. For 4.1V or 4.2V single cell
operation, V
CC
should be between 8V and 28V with the IC
turning off when V
CC
drops below 6V. For 2-cell applica-
tions, the undervoltage lockout is 10.4V with a minimum
V
CC
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.
UU
U
PI FU CTIO S
6
LTC1729 Series
BLOCK DIAGRA
W
BAT
3
2
OVP 1
NTC 5
SENSE
STATUS
100µA
1729 F02
6
V
C
7
–
+
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
M1
M2
M3
50µA
Figure 2. Block Diagram
7
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
V
CC
CHARGE
LED
LTC1729
SENSE
BAT
+
+
–
–
R2
200Ω
20mV
IBIAS
20mV R1
0.2Ω
CHARGING
CURRENT
C1
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
C
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
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8
LTC1729 Series
V
MAX
= 1V
V
MIN
= 0V
4.5V/CELL
BATTERY CLAMP
PULL-DOWN
ON
V
MAX
= 0V
V
MIN
= 0V
2.7V/CELL
NORMAL CHARGE
BATTERY VOLTAGE
V
MAX
= 0V
V
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
CC
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
CC
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
CC
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
CC
voltage drops below the UVLO threshold.
If external circuitry is connected directly to the V
CC
pin and
the input power is removed, battery current will flow
through the charger’s internal parasitic diode (SW pin to
V
CC
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
9
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
C
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
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
= 12mA
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
Figure 6. State Diagram
10
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
V
MAX
signal is activated as mentioned in the Block Dia-
gram section. This causes the state machine to make the
V
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
V
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
3k
200k
STATUS
1729 F07
V
CC
LTC1729
V
IN
V
DD
OUT
µPROCESSOR
IN
6
8
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,
11
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
V
CC
V
C
STATUS
NTC
V
C
V
CC
1
2
3
4
8
7
6
5
LTC1729-4.2
1µF
0.1µF
1729 F08
10k NTC THERMISTOR
NTHS1206N02 VISHAY/DALE
200Ω
100µA
1729 F09
–
+
COMP1
LTC1729
SENSE
I
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
C
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
CC
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.
12
LTC1729 Series
Wide Input Voltage Range 1A Charger
OVP
BAT
SENSE
GND
V
CC
V
C
STATUS
NTC
S/S
V
SW
GND V
C
V
FB
I
FB
LTC1729-8.4
BOOST
CAP
+
GND
CAP
–
V
+
OSC
LV
V
OUT
LTC1044
LT1512
C4
0.33µF
C1
22µF
×2
Si9925
R3
0.1Ω
R1
29.4k
D2
1/2 BAT85S
D3
1/2 BAT85S
10µF
R2
12.4k
L1**
C6
1µF
1729 TA01
* TOKIN CERAMIC 1E225ZY5U-C203-F
** L1, L2 ARE TWO 10µH INDUCTORS: SUMIDA CDRH6D38-100
R8
R8:10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT
R5
470Ω
C2*
4.7µF
R7
100Ω
R4 39Ω
L2**
+
+
C3
22µF
ON/OFF
C7
10µF
C5
0.1µF
D1
MBRS340
V
IN
3V TO 28V
V
IN
+
R6
0.1Ω
R
PULL-UP
47k
8.4V
220k
+
TYPICAL APPLICATIO S
U
V
CC
V
C
STATUS
NTC
8
7
6
5
LTC1729
2.2k 0.1µF
TO V
CC
12V
10k
2k
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
ON
OFF
OFF
GREEN
OFF
OFF
ON
ON
1729 TA03
Using STATUS Pin to Indicate Charge Status
13
LTC1729 Series
4A, 2-Cell Lithium-Ion Battery Charger
TYPICAL APPLICATIO S
U
CLN
CLP
INFET
UV
SYNC
SHDN
FLAG
CAP
COMP1
GBIAS
TGATE
SW
BGATE
V
C
PROG
3 CELL
V
FB
4.2V
4.1V
AGND
PGND
TO
SYSTEM
LOAD
BAT2 BAT SENSE SPIN
R
PROG
4.93k
1%
C
PROG
1µF
BOOST BOOSTC
OVP
BAT
SENSE
GND
V
CC
V
C
STATUS
NTC
LTC1729-8.4
LT1505
C
IN
*
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
R
S1
0.025Ω
R
S2
200Ω
1%
R
S4
0.025Ω
M3
Si4435
DBODY
V
IN
(FROM
ADAPTER) R7
500Ω
R5
3k
R1
1k
R4
3kC5
0.33µF
R6
5.1k
R
S3
200Ω
1%
C1
1µF
8.4V
+
D5
††
V
CC
C
OUT
***
22µF
× 2
C9
0.1µF
C8
0.1µF
C7
0.68µF
C3
2.2µF
C4
0.1µF
M1
Si4412
M2
Si4412
D2
MMSD4148
D3
MMSD4148
L1**
15µH
D4
MBRS140
5Ω
C2
0.68µF
R3
300Ω
C6
†
0.1µF
R8
100Ω
R9
1.4k
R
PULL-UP
10k
1729 TA02
10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT
+
+
14
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
12
34
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.
U
PACKAGE DESCRIPTIO
15
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.
U
PACKAGE DESCRIPTIO
16
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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3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger
TO MAIN
SYSTEM
LOAD
BATSENSE
OVP
BAT
SENSE
GND
V
CC
V
C
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
R1
510Ω
R
S2
200Ω
1% R
S1
0.05Ω
R
S4
0.05Ω
R5
3k
R3
300Ω
R2
1k
GND CLP
CLN
V
CC
V
C
UV
PROG
SW
BOOST
COMP1
SPIN
OVP
C6
0.1µF
R6
5.1K
D4
SS24 D2
SS24
C3
220pF
R7
1.4k
R
S3
200Ω
1%
C2
0.47µF
8.4V
+
D5
†
1729 TA04
R
PROG
4.93k
C
PROG
1µF
C1*
15µF
C4
0.33µF
D3
MBR0540T
L1**
22µH
C5
1µF
C7***
22µF
R4
100Ω
D1
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
U
