LINER LTC1729CMS8-8.2 Li-ion battery charger termination controller Datasheet

Final Electrical Specifications
LTC1729 Series
Li-Ion Battery Charger
Termination Controllers
October 1999
U
DESCRIPTION
FEATURES
■
■
■
■
■
■
■
■
■
■
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, automatic charger and battery detection and status output.
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
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).
U
APPLICATIONS
■
■
■
Cellular Phones
PDAs
Cradle Chargers
Camcorders
The LTC1729 series is available in the 8-pin MSOP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
■
TYPICAL APPLICATION
MBRM120T3
MBRM120T3
1µF
LT1510-5
0.22µF
300Ω
+
6.19k
PROG
L1**
10µH
BOOST
GND
MMBD914L
SENSE
OVP
1k
0.1µF
BAT
VCC
2
200Ω
1µF
CIN*
10µF
VC
OVP
1
INPUT POWER
8.2V TO 20V
VCC
SW
BAT
VC
LTC1729-4.2
3
SENSE STATUS
4
GND
NTC
* 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
COUT***
22µF
8
+
4.2V
0.1µF
1.4k
7
D1†
CHARGE STATUS
6
1729 F01
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
Figure 1. 500kHz Li-Ion Cell Phone Charger (0.8A)
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
W W
U
W
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VCC ......................................................................... 30V
SENSE, VBAT, NTC .................................... – 0.3V to 15V
VC ............................................................. – 0.3V to 15V
OVP ............................................................ – 0.3V to 5V
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
U
W
U
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
OVP
BAT
SENSE
GND
8
7
6
5
1
2
3
4
VCC
VC
STATUS
NTC
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 200°C/ W
LTC1729CMS8-4.1
LTC1729CMS8-4.2
LTC1729CMS8-8.2
LTC1729CMS8-8.4
ORDER PART
NUMBER
TOP VIEW
OVP
1
8 VCC
BAT
2
7 VC
SENSE
3
6 STATUS
GND
4
5 NTC
MS8 PART MARKING
LTLY
LTJH
LTLZ
LTJG
S8 PACKAGE
8-LEAD PLASTIC SO
LTC1729CS8-4.1
LTC1729CS8-4.2
LTC1729CS8-8.2
LTC1729CS8-8.4
S8 PART MARKING
TJMAX = 150°C, θJA = 150°C/ W
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.
SYMBOL
PARAMETER
DC CHARACTERISTICS
CONDITIONS
IVIN
VIN = 5V (Below UVLO)
VIN = 8V, 200µA Pull-Up on VBAT (4.5V) No Bat
VIN = 8V, VBAT = 2.5V Trickle
VIN = 8V, VBAT = 3.5V Charge
VCC Supply Current
LTC1729-4.1/LTC1729-4.2
MIN
TYP
MAX
UNITS
●
1
1.0
10
0.5
5
1.4
17
3.0
12
2.0
21
5.0
µA
mA
mA
mA
●
●
VLKOH
VIN Undervoltage Lockout High
●
5.5
6.5
7.5
V
VLKOL
VIN Undervoltage Lockout Low
●
5.0
6.0
7.0
V
IVBAT
VBAT Current
VIN = 5V (Below UVLO), VBAT = 4.2V
VIN = 8V, VBAT = 4.25V No Bat
VIN = 8V, VBAT = 2.5V Trickle
VIN = 8V, VBAT = 3.5V Charge
●
●
●
–1
40
– 19
– 2.7
– 0.1
73
– 16
– 1.3
1
120
– 9.5
– 0.5
µA
µA
mA
mA
VCLAMP
VBAT Clamp
No Bat (External 200µA Pull-Up on VBAT)
●
4.25
4.5
4.75
V
VMAX
High VBAT Threshold
High Going Threshold
Low Going Threshold
●
●
4.25
4.25
4.51
4.50
4.75
4.75
V
V
VMIN
Low VBAT Threshold
High Going Threshold
Low Going Threshold
●
●
2.55
2.45
2.7
2.6
2.85
2.75
V
V
ISENSE
SENSE Pin Current
Charge State, VSENSE = 3V
●
85
100
115
µA
VC10
SENSE Pin C/10 Offset
Charge State, VC10 = (VBAT – VSENSE)
●
±1
±2.5
mV
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
MIN
TYP
MAX
90
100
110
●
0.160
0.206
0.240
V
High Going Threshold
Low Going Threshold
●
●
0.460
0.380
0.486
0.405
0.510
0.430
V
V
Thermistor Pin Cold Hold Threshold
High Going Threshold
Low Going Threshold
●
●
2.70
2.10
2.79
2.23
2.90
2.35
V
V
VOVP
OVP Pin Voltage
VBAT = 4.1V or VBAT = 4.2V
●
2.455
2.460
2.465
2.465
2.475
2.470
V
V
VOL-ST
Output Low Voltage-STATUS Pin
IO = 3mA
●
0.5
0.9
1.2
V
VOL-VC
Output Low Voltage-VC Pin
IO = 1mA
●
0.35
0.6
0.75
V
ISOFT
Status Soft Pull-Down Current
VSTATUS = 4.5V
●
40
50
65
µA
SYMBOL
INTC
PARAMETER
NTC Pin Current
VNTC-RESET
Thermistor Pin Reset Threshold
VNTC-HOT
Thermistor Pin Hot Hold Threshold
VNTC-COLD
CONDITIONS
VNTC = 1V
UNITS
µA
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C,
VIN = 12V
SYMBOL
PARAMETER
DC CHARACTERISTICS
CONDITIONS
IVIN
VIN = 9V (Below UVLO)
VIN = 12V, 200µA Pull-Up on VBAT (9V) No Bat
VIN = 12V, VBAT = 5V Trickle
VIN = 12V, VBAT = 7V Charge
VCC Supply Current
VLKOH
VIN Undervoltage Lockout High
VLKOL
VIN Undervoltage Lockout Low
IVBAT
VBAT Current
LTC1729-8.2/LTC1729-8.4
MIN
TYP
MAX
UNITS
●
1
1.0
10
0.5
6
1.4
17
3.0
12
2.0
21
5.0
µA
mA
mA
mA
●
9.5
10.4
11.4
V
●
●
●
8.5
9.6
10.5
V
VIN = 9V (Below UVLO), VBAT = 8.4V
VIN = 12V, VBAT = 8.5V No Bat
VIN = 12V, VBAT = 5V Trickle
VIN = 12V, VBAT = 7V Charge
●
●
●
–1
60
– 19
– 2.7
– 0.1
95
– 16
– 1.3
1
140
– 9.5
– 0.5
µA
µA
mA
mA
VCLAMP
VBAT Clamp
No Bat (External 200µA Pull-Up on VBAT)
●
8.5
9
9.5
V
VMAX
High VBAT Threshold
High Going Threshold
Low Going Threshold
●
●
8.5
8.5
9.013
9
9.5
9.5
V
V
VMIN
Low VBAT Threshold
High Going Threshold
Low Going Threshold
●
●
5.1
4.9
5.4
5.2
5.7
5.5
V
V
ISENSE
SENSE Pin Current
Charge State, VSENSE = 7V
●
85
100
115
µA
VC10
SENSE Pin C/10 Offset
Charge State, VC10 = (VBAT – VSENSE)
●
±1
±2.5
mV
INTC
NTC Pin Current
VNTC = 1V
●
90
100
110
µA
VNTC-RESET
Thermistor Pin Reset Threshold
●
0.160
0.206
0.240
V
VNTC-HOT
Thermistor Pin Hot Hold Threshold
High Going Threshold
Low Going Threshold
●
●
0.460
0.380
0.486
0.405
0.510
0.430
V
V
VNTC-COLD
Thermistor Pin Cold Hold Threshold
High Going Threshold
Low Going Threshold
●
●
2.70
2.10
2.79
2.23
2.90
2.35
V
V
VOVP
OVP Pin Voltage
VBAT = 8.2V or VBAT = 8.4V
●
2.455
2.460
2.465
2.465
2.475
2.470
V
V
VOL-ST
Output Low Voltage-STATUS Pin
IO = 3mA
●
0.5
0.9
1.2
V
VOL-VC
Output Low Voltage-VC Pin
IO = 1mA
●
0.35
0.6
0.75
V
ISOFT
Status Soft Pull-Down Current
VSTATUS = 4.5V
●
40
50
65
µA
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
AC CHARACTERISTICS
TIMER1
Timer for Trickle-Charge Preconditioning
CONDITIONS
MIN
TYP
MAX
UNITS
●
0.869
1
1.305
Hr
TIMER2
Timer for Charging
●
2.61
3
3.55
Hr
TIMER3
Timer for VMAX Filter
●
0.764
0.859
1.043
sec
TIMER4
Timer for VC/10 Filter
●
3.055
3.5
4.17
sec
TOSC
Oscillator Period
●
6.66
7.63
9.09
µs
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: VIN = 8V for LTC1729-4.1/LTC1729-4.2; VIN = 12V for
LTC1729-8.2/LTC1729-8.4
U
U
U
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.
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 VCC
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.
LTC1729 Series
W
BLOCK DIAGRA
7 VC
M2
SENSE 3
100µA
UVLO
6 STATUS
–
M3
COMP1
+
50µA
1.3mA
16mA
C/10
COMP2
BAT 2
+
4.5V/CELL
CLAMP
UVLO
M1
4.5V/CELL
–
2.7V/CELL
+
VMAX
LOGIC
AND
TIMER
COMP3
OVP 1
2.465V
–
VMIN
HOLD
100µA
COMP4
+
NTC 5
2.79V
–
0.405V
+
COMP5
–
COMP6
0.2V
+
RESET
–
1729 F02
Figure 2. Block Diagram
U
W
U
U
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
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
U
U
W
U
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 VMAX = 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 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.
VCC
CHARGING
CURRENT
LTC1729
IBIAS
+
20mV
–
+ 20mV –
R1
0.2Ω
R2
200Ω
SENSE
C1
1µF
STATUS
–
COMP1
BAT
CHARGE
LED
100µA
+
3-SEC
FILTER
LOGIC
AND
TIMERS
50µA
1729 F03
Figure 3. C/10 Detection Circuit
6
LTC1729 Series
U
W
U
U
APPLICATIONS INFORMATION
BATTERY VOLTAGE
VMAX = 1V
VMIN = 0V
CHARGE
BATTERY CLAMP
PULL-DOWN
ON
RESET MODE
IBAT = 0
STATUS = PULL-DOWN
VC = PULL-DOWN
4.5V/CELL
VMAX = 0V
VMIN = 0V
NORMAL CHARGE
VBAT < VMIN
2.7V/CELL
VMAX = 0V
VMIN = 1V
TRICKLE CHARGE
PRECONDITIONING
1729 F04
Figure 4. BAT Voltage Operating Range
VBAT > VMIN
PRECONDITION
IBAT = 16mA
STATUS = PULL-DOWN V
BAT < VMIN
VC = PULL-DOWN
t MAX = 1HR
VBAT < VMAX
FOR MORE THAN 1SEC
THERMISTOR VOLTAGE
2.79V
NORMAL CHARGE
0.405V
TIME > t MAX
DONE
IBAT = 0
STATUS = OPEN
VC = PULL-DOWN
VBAT < VMAX
FOR MORE THAN 1SEC
VBAT > VMAX
FOR MORE THAN 1SEC
VBAT > VMAX
FOR MORE THAN 1SEC
NO BAT
IBAT = 0
STATUS = OPEN
VC = PULL-DOWN
VNTC > 2.79V OR
VNTC < 0.405V
HOLD MODE
NOTE: FOR STATUS
PULL-DOWN = HARD:
FOR CURRENT > C/10
PULL-DOWN = 50µA:
FOR CURRENT < C/10 FOR 3SEC
CHARGER “ON”
IBAT = 1.3mA
STATUS = PULL-DOWN
VC = OPEN
t MAX = 3HR
VBAT > VMAX
PAUSE
IBAT = 0
STATUS = PULL-DOWN
VC = PULL-DOWN
HOLD MODE
VBAT > VMIN
VNTC < 2.79V AND
VNTC > 0.405V
HOLD MODE
IBAT = 0
STATUS = PREVIOUS STATUS
VC = PULL-DOWN
0.2V
RESET MODE
1729 F05
1729 F06
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.
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
U
W
U
U
APPLICATIONS INFORMATION
3. When a heavily discharged battery is installed, trickle
charge conditioning must take place before the full
charge current.
requirement for this transition is for the BAT pin voltage to
exceed VMAX for more than one second. The IC now
assumes that the battery has been removed.
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.
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 VMAX for one second. The
LTC1729 will now work on the assumption that a new
battery has been installed.
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 > tMAX transition to the Done state.
Second, if the battery is removed from the charger, the
VMAX signal is activated as mentioned in the Block Diagram section. This causes the state machine to make the
VBAT > VMAX transition to the Pause state. The third way to
exit the charger “ON” state is with a VBAT < VMIN transition
to the Precondition state. The battery will need to drop
below 2.6V/cell to be less than VMIN. 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
VBAT remain greater than VMAX 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 VMAX for more than one second, then
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
8
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
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
U
W
U
APPLICATIONS INFORMATION
LTC1729-4.2
1
OVP
2
BAT
1µF 3
200Ω
SENSE
4
OVP
VCC
BAT
VC
SENSE
8
7
0.1µF
VC
6
STATUS
GND
VCC
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.
5
NTC
By reducing the LTC1729 SENSE pin resistor to 0Ω, the
STATUS pin function can be changed to a charging indicator (Figure 8). The LED on the STATUS pin will always go
off after the 3-hour charge cycle is completed, regardless
of the C/10 circuitry.
10k NTC THERMISTOR
NTHS1206N02 VISHAY/DALE
1729 F07
Figure 7. Terminate Charging at C/10
Using Status as a Charging Indicator
CHARGE
CURRENT
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 voltage which is compared with the voltage across the charge
current sense resistor. When these voltages are equal, the
LTC1729
IBIAS
+
–
SENSE
RESISTOR
SENSE
–
BAT
+
100µA
COMP1
1729 F08
Figure 8. Modify C/10 Indication to Create Charging Indicator
U
TYPICAL APPLICATIONS
SEPIC Charger with 0.5A Output Current
L1A**
INPUT POWER
4V TO 9V
C3
22µF
VIN
C2*
2.2µF
D1
MBRS130LT3
R6
0.2Ω
BOOST
VSW
C1
22µF
R1
29.4k
L1B**
S/S LT1512
VFB
GND
VC
IFB
C5
0.1µF
R5
1k
R4, 24Ω
C4
0.22µF
R2
12.4k
R3
0.2Ω
CAP +
+
LTC1044
GND
4.2V
CAP –
V+
D2
1/2 BAT85S
OSC
LV
+
VOUT
C8
10µF
FOR 3.5V TO 14V USE LTC1144
D3
1/2 BAT85S
RPULLUP
10k
OVP
R7
C6
100Ω 1µF
VCC
VC
BAT
LTC1729-4.2
SENSE STATUS
GND
NTC
C7
10µF
R9
1k
D4†
1729 F11
* 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
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
9
LTC1729 Series
U
TYPICAL APPLICATIONS
4A, 2-Cell Lithium-Ion Battery Charger
TO
SYSTEM
POWER
DBODY
M3
Si4435
VIN
(FROM
ADAPTER)
R7
500Ω
RS4
0.025Ω
C1
1µF
CIN*
47µF
35V
C4
D3
0.1µF MMSD4148
VCC BOOST BOOSTC
GBIAS
CLN
TGATE
CLP
R5
3k
SW
INFET
UV
SHDN
FLAG
CAP
COMP1
C6
0.1µF
R1
1k
C7
0.68µF
D2
MMSD4148
5Ω
VC
PROG
3 CELL
VFB
RPROG
4.93k
1%
C2
0.68µF
M1
Si4412
M2
Si4412
BGATE
LT1505
SYNC
R6
5.1k
C3
2.2µF
D4
MBRS140
RS2
200Ω
1%
CPROG
1µF
PGND
BAT2 BAT SENSE SPIN
RS3
200Ω
1%
RPULL-UP
10k
OVP
C8
0.1µF
R8
100Ω
* SANYO OS-CON
** SUMIDA CDRH127-150
*** AVX TPSD226L025R0200
† LUMEX SML-LX0805GW-TR
10
VCC
BAT
VC
LTC1729-8.4
SENSE STATUS
GND
NTC
C9
0.1µF
+
8.4V
R4
3k
C5
0.33µF
R3
300Ω
AGND
COUT***
22µF
×2
L1**
15µH
4.2V
4.1V
RS1
0.025Ω
R9
1.4k
D5†
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 F09
LTC1729 Series
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.118 ± 0.004*
(3.00 ± 0.102)
0.034 ± 0.004
(0.86 ± 0.102)
8
7 6
5
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.021 ± 0.006
(0.53 ± 0.015)
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1098
1
* 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
2 3
4
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*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
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
11
LTC1729 Series
U
TYPICAL APPLICATION
3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger
D1
SS24
R1
510Ω
GND
RS4
0.05Ω
CLN
SW
D4
SS24
C2
0.47µF
VCC
+
LT1511 OR LT1769
BOOST
L1**
22µH
INPUT POWER
11.5V TO 28V
CLP
D3
MBR0540T
C1*
15µF
D2
SS24
UV
R6
5.1K
COMP1
C3
200pF
PROG
VC
SPIN
OVP
SENSE
RS2
200Ω
1%
C4
0.33µF
BAT
RS1
0.05Ω
OVP
C5
1µF
CPROG
1µF
R3
300Ω
R2
1k
RS3
200Ω
1%
C7***
22µF
R4
100Ω
R5
3k
TO MAIN
SYSTEM
POWER
RPROG
4.93k
+
8.4V
C6
0.1µF
VCC
R7
1.4k
D5†
BAT
VC
LTC1729-8.4
SENSE STATUS
GND
NTC
* TOKIN C55Y5U1E156Z
** SUMIDA CDRH125-220MC
*** AVX TPSD226K025R0200
† LUMEX SML-LX0805GW-TR
D1, D2, D4: GENERAL SEMICONDUCTOR
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 RSENSE
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
12
Linear Technology Corporation
1729i LT/TP 1099 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1999
Similar pages