LINER LTC1729 Li-ion battery charger termination controller Datasheet

LTC1729 Series
Li-Ion Battery Charger
Termination Controllers
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FEATURES
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DESCRIPTIO
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.
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
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).
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APPLICATIO S
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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.
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TYPICAL APPLICATIO
MBRM120T3
MBRM120T3
1µF
LT1510-5
0.22µF
INPUT POWER
8.2V TO 20V
VCC
SW
300Ω
CIN*
10µF
6.19k
PROG
L1**
10µH
BOOST
1k
VC
GND
MMBD914L
0.1µF
OVP
SENSE
BAT
+
COUT***
22µF
+
4.2V
LTC1729-4.2
1
2
200Ω
1µF
3
4
OVP
BAT
SENSE
GND
VCC
VC
STATUS
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
8
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)
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LTC1729 Series
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ABSOLUTE
RATI GS
(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
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PACKAGE/ORDER I FOR ATIO
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
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
TJMAX = 150°C, θJA = 200°C/ W
LTLY
LTJH
LTLZ
LTJG
LTC1729CS8-4.1
LTC1729CS8-4.2
LTC1729CS8-8.2
LTC1729CS8-8.4
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
172941
172942
172982
172984
TJMAX = 150°C, θJA = 150°C/ W
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
LTC1729-4.1/LTC1729-4.2
MIN
TYP
MAX
CONDITIONS
UNITS
DC CHARACTERISTICS
●
1
1.0
10
0.5
5
1.4
17
3.0
12
2.0
21
5.0
µA
mA
mA
mA
●
5.5
6.5
7.5
V
●
5.0
6.0
7.0
V
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
– 12
– 1.3
1
120
– 9.5
– 0.5
µA
µA
mA
mA
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
ICC
VCC Supply Current
VLKOH
VIN Undervoltage Lockout High
VLKOL
VIN Undervoltage Lockout Low
IVBAT
VBAT Current
VCLAMP
2
VIN = 5V (Below UVLO)
VIN = 8V, VBAT > 4.5V, No Bat
VIN = 8V, VBAT = 2.5V Trickle
VIN = 8V, VBAT = 3.5V Charge
●
●
LTC1729 Series
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 8V
SYMBOL
PARAMETER
CONDITIONS
INTC
NTC Pin Current
VNTC = 1V
VNTC-RESET
Thermistor Pin Reset Threshold
VNTC-HOT
Thermistor Pin Hot Hold Threshold
VNTC-COLD
LTC1729-4.1/LTC1729-4.2
MIN
TYP
MAX
UNITS
●
90
100
110
µA
●
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
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 12V
SYMBOL
PARAMETER
LTC1729-8.2/LTC1729-8.4
MIN
TYP
MAX
CONDITIONS
UNITS
DC CHARACTERISTICS
●
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
– 12
– 1.3
1
140
– 9.5
– 0.5
µA
µA
mA
mA
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
ICC
VCC Supply Current
VLKOH
VIN Undervoltage Lockout High
VLKOL
VIN Undervoltage Lockout Low
IVBAT
VBAT Current
VCLAMP
VIN = 9V (Below UVLO)
VIN = 12V, VBAT > 9V, No Bat
VIN = 12V, VBAT = 5V Trickle
VIN = 12V, VBAT = 7V Charge
●
●
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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 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
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TYPICAL PERFOR A CE CHARACTERISTICS
IVBAT vs Temperature (4.2V Version)
14
IVBAT vs Temperature (8.4V Version)
14
VBAT = 2.5V
IVBAT vs VCC (4.2V Version)
14
VBAT = 5V
12
12
12
10
10
10
8
6
IVBAT (mA)
IVBAT (mA)
IVBAT (mA)
VBAT = 2.5V
8
6
8
6
4
4
4
2
2
2
0
0
0
VBAT = 3.5V
0
25
50
75
25
0
100
50
100
75
IVBAT vs VCC (8.4V Version)
ICC vs VCC (4.2V Version)
8
10
12
10
8
0
2
14
18
22
VCC (V)
26
30
1729 G04
8
6
VBAT = 3.5V
4
VBAT = 7V
30
VBAT = 5V
VBAT = 2.5V
6
4
26
ICC vs VCC (8.4V Version)
ICC (mA)
12
ICC (mA)
IVBAT (mA)
10
6
22
14
VBAT = 5V
10
18
VCC (V)
14
1729 G03
14
12
2
10
1729 G02
1729 G01
4
6
TEMPERATURE (°C)
TEMPERATURE (°C)
4
VBAT = 7V
2
6
10
14
18
VCC (V)
22
26
30
1729 G05
10
14
18
22
VCC (V)
26
30
1729 G06
LTC1729 Series
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PI FU CTIO S
OVP (Pin 1): Connection to 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 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 VC 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 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 IC in a high impedance
condition. When the supply is connected, the IC is initialized in the Reset mode with the state machine forced in the
Charge state with all the timers set to zero.
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LTC1729 Series
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BLOCK DIAGRA
7 VC
M2
SENSE 3
100µA
UVLO
6 STATUS
–
M3
COMP1
+
50µA
C/10
1.3mA
12mA
COMP2
BAT
+
2
UVLO
M1
4.5V/CELL
CLAMP
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
6
LTC1729 Series
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APPLICATIO S I FOR ATIO
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 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.
Comparator COMP1 is used to indicate C/10 charge current threshold. (“C” is a term used to indicate the Amperehour 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.
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
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LTC1729 Series
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APPLICATIO S I FOR ATIO
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.
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.
If external circuitry is connected directly to the VCC pin and
the input power is removed, battery current will flow
through the charger’s internal parasitic diode (SW pin to
VCC 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 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.
HOLD MODE
BATTERY VOLTAGE
VMAX = 1V
VMIN = 0V
BATTERY CLAMP
PULL-DOWN
ON
4.5V/CELL
VMAX = 0V
VMIN = 0V
NORMAL CHARGE
2.7V/CELL
VMAX = 0V
VMIN = 1V
NORMAL CHARGE
0.405V
HOLD MODE
0.2V
TRICKLE CHARGE
PRECONDITIONING
1729 F04
Figure 4. BAT Voltage Operating Range
8
THERMISTOR VOLTAGE
2.79V
RESET MODE
1729 F05
Figure 5. NTC Voltage Operating Range
LTC1729 Series
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APPLICATIO S I FOR ATIO
State Machine
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 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 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.
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.
CHARGE
RESET MODE
IBAT = 0
STATUS = PULL-DOWN
VC = PULL-DOWN
VBAT < VMIN
VBAT > VMIN
VBAT > VMIN
PRECONDITION
IBAT = 12mA
STATUS = PULL-DOWN V
BAT < VMIN
VC = PULL-DOWN
t MAX = 1HR
VBAT < VMAX
FOR MORE THAN 1SEC
CHARGER “ON”
IBAT = 1.3mA
STATUS = PULL-DOWN
VC = OPEN
t MAX = 3HR
TIME > t MAX
VBAT > VMAX
PAUSE
IBAT = 0
STATUS = PULL-DOWN
VC = PULL-DOWN
VBAT > VMAX
FOR MORE THAN 1SEC
NOTE: FOR STATUS
PULL-DOWN = HARD:
FOR CURRENT > C/10
PULL-DOWN = 50µA:
FOR CURRENT < C/10 FOR 3SEC
DONE
IBAT = 0
STATUS = OPEN
VC = PULL-DOWN
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
VNTC < 2.79V AND
VNTC > 0.405V
HOLD MODE
IBAT = 0
STATUS = PREVIOUS STATUS
VC = PULL-DOWN
1729 F06
Figure 6. State Diagram
9
LTC1729 Series
U
W
U U
APPLICATIO S I FOR ATIO
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
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.
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.
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.
10
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 microprocessor can detect three states from this pin (charging,
C/10 and stop charging). See Figure 7.
VIN
VDD
8
VCC
200k
LTC1729
STATUS
6
µPROCESSOR
3k
OUT
IN
1729 F07
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 resistor. 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
U
W
U U
APPLICATIO S I FOR ATIO
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 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 VCC 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 voltage 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 indicator (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.
LTC1729-4.2
1
OVP
2
BAT
1µF 3
200Ω
SENSE
4
OVP
VCC
BAT
SENSE
VC
STATUS
GND
NTC
8
7
VCC
0.1µF
VC
6
5
10k NTC THERMISTOR
NTHS1206N02 VISHAY/DALE
1729 F08
Figure 8. Terminate Charging at C/10
CHARGE
CURRENT
LTC1729
IBIAS
+
–
SENSE
RESISTOR
SENSE
–
BAT
+
100µA
COMP1
1729 F09
Figure 9. Modify C/10 Indication to Create Charging Indicator
11
LTC1729 Series
U
TYPICAL APPLICATIO S
Wide Input Voltage Range 1A Charger
VIN
3V TO 28V
L1**
+
C3
VIN
22µF
C2*
4.7µF
Si9925
D1
MBRS340
BOOST
VSW
+
L2**
ON/OFF
R1
29.4k
S/S LT1512
VFB
GND
VC
C4
0.33µF
R5
470Ω
C5
0.1µF
D2
1/2 BAT85S
CAP +
OSC
LTC1044
GND
LV
C1
22µF
×2
CAP –
D3
1/2 BAT85S
VOUT
+
R4 39Ω
IFB
V+
10µF
R2
12.4k
R3
0.1Ω
R6
0.1Ω
8.4V
RPULL-UP
47k
LTC1729-8.4
R7 C6
100Ω 1µF
+
OVP
VCC
BAT
VC
C7
10µF
220k
1729 TA01
SENSE
GND
STATUS
R8:10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE
NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT
NTC
R8
* TOKIN CERAMIC 1E225ZY5U-C203-F
** L1, L2 ARE TWO 10µH INDUCTORS: SUMIDA CDRH6D38-100
Using STATUS Pin to Indicate Charge Status
TO VCC
12V
VCC
8
0.1µF
2.2k
VC
7
LTC1729
STATUS
NTC
6
5
PNP: MMBT3906
12
47k
10k
2k
4.7k
2k
CONDITION
NO WALL ADAPTER
CHARGING (IBAT > C/10)
CHARGING (IBAT < C/10)
TIMER EXPIRED
AMBER
OFF
ON
OFF
OFF
GREEN
OFF
OFF
ON
ON
1729 TA03
AMBER LED
GREEN LED
LTC1729 Series
U
TYPICAL APPLICATIO S
4A, 2-Cell Lithium-Ion Battery Charger
TO
SYSTEM
LOAD
DBODY
M3
Si4435
VIN
(FROM
ADAPTER)
RS4
0.025Ω
+
R7
500Ω
C1
1µF
CIN*
47µF
35V
C4
D3
0.1µF MMSD4148
VCC BOOST BOOSTC
GBIAS
CLN
TGATE
CLP
R5
3k
SW
INFET
LT1505
SYNC
SHDN
VFB
RPROG
4.93k
1%
C2
0.68µF
M1
Si4412
M2
Si4412
PROG
CAP
D4
MBRS140
AGND
RS2
200Ω
1%
R8
100Ω
* SANYO OS-CON
** SUMIDA CDRH127-150
*** AVX TPSD226L025R0200
† C6 NOT NEEDED IF FLAG NOT USED
†† LUMEX SML-LX0805GW-TR
OVP
VCC
BAT
VC
SENSE
GND
+
RS3
200Ω
1%
RPULL-UP
10k
LTC1729-8.4
C8
0.1µF
COUT***
22µF
×2
8.4V
CPROG
1µF
PGND
BAT2 BAT SENSE SPIN
+
R4
3k
C5
0.33µF
R3
300Ω
4.1V
RS1
0.025Ω
L1**
15µH
4.2V
COMP1
C6†
0.1µF
5Ω
VC
3 CELL
FLAG
R1
1k
C7
0.68µF
D2
MMSD4148
BGATE
UV
R6
5.1k
C3
2.2µF
C9
0.1µF
R9
1.4k
D5††
STATUS
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 TA02
13
LTC1729 Series
U
PACKAGE DESCRIPTIO
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)
8
7 6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
1
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
2 3
4
0.034 ± 0.004
(0.86 ± 0.102)
0° – 6° TYP
0.021 ± 0.006
(0.53 ± 0.015)
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.006 ± 0.004
(0.15 ± 0.102)
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
14
LTC1729 Series
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
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
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.
SO8 1298
15
LTC1729 Series
U
TYPICAL APPLICATIO
3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger
D1
SS24
R1
510Ω
GND
RS4
0.05Ω
1µF
CLN
SW
D4
SS24
C2
0.47µF
VCC
LT1511 OR LT1769
C1*
15µF
D2
SS24
BOOST
L1**
22µH
INPUT POWER
11.5V TO 28V
CLP
D3
MBR0540T
UV
R6
5.1K
COMP1
C3
220pF
PROG
VC
SPIN
OVP
SENSE
RS2
200Ω
1%
C4
0.33µF
BAT
R2
1k
RS3
200Ω
1%
RS1
0.05Ω
+
LTC1729-8.4
R4
100Ω
R5
3k
TO MAIN
SYSTEM
LOAD
C5
1µF
OVP
VCC
BAT
VC
SENSE
GND
C7***
22µF
CPROG
1µF
R3
300Ω
RPROG
4.93k
+
8.4V
C6
0.1µF
R7
1.4k
D5†
STATUS
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 TA04
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
LT1571-1/LT1571-2
LT1571-5
200kHz/500kHz Constant-Current/Constant-Voltage Battery
Charger Family
Up to 1.5A Charge Current for 1- or 2-Cell Li-Ion Batteries,
Preset and Adjustable Battery Voltages, C/10 Charge Detection
LTC1731
Linear Charger
Programmable Timer, C/10 Flag, 8-Pin MSOP
LTC1732
Linear Charger
Programmable Timer, C/10 Flag, AC Power Good, 10-Pin MSOP
LTC1759
SMBus-Controlled Smart Battery Charger
LT1505 Charger Functionality with SMBus Control
LT1769
2A Constant-Voltage/Constant-Current Battery Charger
28-Pin SSOP Package
16
Linear Technology Corporation
1729f LT/LCG 0800 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