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LTC1729 Series Li-Ion Battery Charger Termination Controllers
FEATURES
s s s s s s s s s
DESCRIPTIO
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Built-In Termination: 3-Hour Time-Out C/10 Detection with Status Indicator Trickle Charge Preconditioning If Cell < 2.7V Charging Enabled When 0C < T < 50C 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(R)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. Combining the LTC1729 series part with the LT(R)1510 (1.5A), LT1769 (2A), LT1511 (3A) and LT1505 (> 4A) step-down chargers is a simple operation. Connecting six pins from the LTC1729 series part to the step-down chargers completes the integration. The LTC1729 termination controllers are also compatible with step-down/ step-up (SEPIC) chargers, including the LT1512 (2A switch) and LT1513 (3A switch). The LTC1729 series is available in the 8-pin MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s s s s
Cellular Phones PDAs Cradle Chargers Camcorders
TYPICAL APPLICATIO
0.22F L1** 10H MMBD914L
MBRM120T3 SW LT1510-5 PROG BOOST GND OVP SENSE BAT VC 0.1F 1k VCC 1F 300 6.19k
+
COUT*** 22F
+
4.2V
LTC1729-4.2 1 2 200 1F 3 4 OVP BAT SENSE GND VCC VC STATUS NTC 8 7 6
1729 F01
0.1F
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
* TOKIN OR MARCON SURFACE MOUNT ** COILTRONICS TP3-100, 10H, 2.2mm HEIGHT (0.8A CHARGING CURRENT) COILTRONICS TP1 SERIES, 10H, 1.8mm HEIGHT (<0.5A CHARGING CURRENT) *** PANASONIC EEFCD1B220 LUMEX SML-LX0805GW-TR
Figure 1. 500kHz Li-Ion Cell Phone Charger (0.8A)
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MBRM120T3 CIN* 10F INPUT POWER 8.2V TO 20V 1.4k D1 CHARGE STATUS
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LTC1729 Series
ABSOLUTE
AXI U
RATI GS
VCC ......................................................................... 30V SENSE, VBAT, NTC .................................... - 0.3V to 15V VC ............................................................. - 0.3V to 15V OVP ............................................................ - 0.3V to 5V
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW OVP BAT SENSE GND 1 2 3 4 8 7 6 5 VCC VC STATUS NTC
LTC1729CMS8-4.1 LTC1729CMS8-4.2 LTC1729CMS8-8.2 LTC1729CMS8-8.4 MS8 PART MARKING LTLY LTJH LTLZ LTJG
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 150C, JA = 200C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VIN = 8V
SYMBOL ICC PARAMETER VCC Supply Current CONDITIONS VIN = 5V (Below UVLO) VIN = 8V, VBAT > 4.5V, No Bat VIN = 8V, VBAT = 2.5V Trickle VIN = 8V, VBAT = 3.5V Charge
q q q q q
DC CHARACTERISTICS 1 1.0 10 0.5 5.5 5.0 -1 40 - 19 - 2.7 4.25 4.25 4.25 2.55 2.45 85 5 1.4 17 3.0 6.5 6.0 - 0.1 73 - 12 - 1.3 4.5 4.51 4.50 2.7 2.6 100 1 12 2.0 21 5.0 7.5 7.0 1 120 - 9.5 - 0.5 4.75 4.75 4.75 2.85 2.75 115 2.5 A mA mA mA V V A A mA mA V V V V V A mV
VLKOH VLKOL IVBAT
VIN Undervoltage Lockout High VIN Undervoltage Lockout Low 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 No Bat (External 200A Pull-Up on VBAT) High Going Threshold Low Going Threshold High Going Threshold Low Going Threshold Charge State, VSENSE = 3V Charge State, VC10 = (VBAT - VSENSE)
VCLAMP VMAX VMIN ISENSE VC10
VBAT Clamp High VBAT Threshold Low VBAT Threshold SENSE Pin Current SENSE Pin C/10 Offset
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(Note 1)
STATUS .................................................... - 0.3V to 30V Operating Temperature Range .................... 0C to 70C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER
TOP VIEW OVP BAT SENSE GND 1 2 3 4 8 VCC 7 VC 6 STATUS 5 NTC
LTC1729CS8-4.1 LTC1729CS8-4.2 LTC1729CS8-8.2 LTC1729CS8-8.4 S8 PART MARKING 172941 172942 172982 172984
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 150C, JA = 150C/ W
LTC1729-4.1/LTC1729-4.2 MIN TYP MAX
UNITS
q q q q q q q q q q
LTC1729 Series
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VIN = 8V
SYMBOL INTC VNTC-RESET VNTC-HOT VNTC-COLD VOVP VOL-ST VOL-VC ISOFT PARAMETER NTC Pin Current Thermistor Pin Reset Threshold Thermistor Pin Hot Hold Threshold Thermistor Pin Cold Hold Threshold OVP Pin Voltage Output Low Voltage-STATUS Pin Output Low Voltage-VC Pin Status Soft Pull-Down Current High Going Threshold Low Going Threshold High Going Threshold Low Going Threshold VBAT = 4.1V or VBAT = 4.2V IO = 3mA IO = 1mA VSTATUS = 4.5V CONDITIONS VNTC = 1V
q q q q q q q q q q
LTC1729-4.1/LTC1729-4.2 MIN TYP MAX 90 0.160 0.460 0.380 2.70 2.10 2.455 2.460 0.5 0.35 40 100 0.206 0.486 0.405 2.79 2.23 2.465 2.465 0.9 0.6 50 110 0.240 0.510 0.430 2.90 2.35 2.475 2.470 1.2 0.75 65
UNITS A V V V V V V V V V A
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VIN = 12V
SYMBOL ICC PARAMETER VCC Supply Current CONDITIONS VIN = 9V (Below UVLO) VIN = 12V, VBAT > 9V, No Bat VIN = 12V, VBAT = 5V Trickle VIN = 12V, VBAT = 7V Charge
q q q q q
LTC1729-8.2/LTC1729-8.4 MIN TYP MAX 1 1.0 10 0.5 9.5 8.5 -1 60 - 19 - 2.7 8.5 8.5 8.5 5.1 4.9 85 90 0.160 0.460 0.380 2.70 2.10 2.455 2.460 0.5 0.35 40 6 1.4 17 3.0 10.4 9.6 - 0.1 95 - 12 - 1.3 9 9.013 9 5.4 5.2 100 1 100 0.206 0.486 0.405 2.79 2.23 2.465 2.465 0.9 0.6 50 12 2.0 21 5.0 11.4 10.5 1 140 - 9.5 - 0.5 9.5 9.5 9.5 5.7 5.5 115 2.5 110 0.240 0.510 0.430 2.90 2.35 2.475 2.470 1.2 0.75 65
UNITS A mA mA mA V V A A mA mA V V V V V A mV A V V V V V V V V V A
DC CHARACTERISTICS
VLKOH VLKOL IVBAT
VIN Undervoltage Lockout High VIN Undervoltage Lockout Low VBAT Current VIN = 9V (Below UVLO), VBAT = 8.4V VIN = 12V, VBAT = 8.5V No Bat VIN = 12V, VBAT = 5V Trickle VIN = 12V, VBAT = 7V Charge No Bat (External 200A Pull-Up on VBAT) High Going Threshold Low Going Threshold High Going Threshold Low Going Threshold Charge State, VSENSE = 7V Charge State, VC10 = (VBAT - VSENSE) VNTC = 1V High Going Threshold Low Going Threshold High Going Threshold Low Going Threshold VBAT = 8.2V or VBAT = 8.4V IO = 3mA IO = 1mA VSTATUS = 4.5V
q q q q q q q q q q q q q q q q q q q q
VCLAMP VMAX VMIN ISENSE VC10 INTC VNTC-RESET VNTC-HOT VNTC-COLD VOVP VOL-ST VOL-VC ISOFT
VBAT Clamp High VBAT Threshold Low VBAT Threshold SENSE Pin Current SENSE Pin C/10 Offset NTC Pin Current Thermistor Pin Reset Threshold Thermistor Pin Hot Hold Threshold Thermistor Pin Cold Hold Threshold OVP Pin Voltage Output Low Voltage-STATUS Pin Output Low Voltage-VC Pin Status Soft Pull-Down Current
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LTC1729 Series
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. (Note 2)
SYMBOL TIMER1 TIMER2 TIMER3 TIMER4 tOSC PARAMETER Timer for Trickle-Charge Preconditioning Timer for Charging Timer for VMAX Filter Timer for VC/10 Filter Oscillator Period CONDITIONS
q q q q q
MIN 0.869 2.61 0.764 3.055 6.66
TYP 1 3 0.859 3.5 7.63
MAX 1.305 3.55 1.043 4.17 9.09
UNITS Hr Hr sec sec s
AC CHARACTERISTICS
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
TYPICAL PERFOR A CE CHARACTERISTICS
IVBAT vs Temperature (4.2V Version)
14 12 10 VBAT = 2.5V 14 12 10
IVBAT (mA)
IVBAT (mA)
IVBAT (mA)
8 6 4 2 0 0 25 50 TEMPERATURE (C)
1729 G01
75
IVBAT vs VCC (8.4V Version)
12 VBAT = 5V 10 8
IVBAT (mA)
ICC (mA)
ICC (mA)
6 4 2 0 10 14 18 22 VCC (V) 26 30
1729 G04
VBAT = 7V
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UW
IVBAT vs Temperature (8.4V Version)
VBAT = 5V 14 12
IVBAT vs VCC (4.2V Version)
VBAT = 2.5V 10 8 6 4 2 VBAT = 3.5V 0 100 0 25 50 TEMPERATURE (C)
1729 G02
8 6 4 2
0 75 100 6 10 14 18 VCC (V) 22 26 30
1729 G03
ICC vs VCC (4.2V Version)
14 12 10 8 6 4 2 VBAT = 3.5V VBAT = 2.5V 14 12 10 8 6 4 2 6 10 14 18 VCC (V) 22 26 30
1729 G05
ICC vs VCC (8.4V Version)
VBAT = 5V
VBAT = 7V 10 14 18 22 VCC (V) 26 30
1729 G06
LTC1729 Series
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 200A current source that will compensate for this 50A to 80A load. SENSE (Pin 3): Input to C/10 Current Detection Circuit. This pin sinks 100A 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 100A 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 50A 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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5
LTC1729 Series
BLOCK DIAGRA
SENSE 3
COMP1
BAT
2 M1 UVLO 4.5V/CELL CLAMP 4.5V/CELL
OVP 1
2.465V
100A COMP4 NTC 5 2.79V
+ -
COMP5 0.405V
+ -
COMP6
0.2V
+ -
6
W
7 VC M2
100A
UVLO 6 STATUS
+
50A C/10
-
1.3mA
12mA COMP2
M3
+ -
COMP3 2.7V/CELL
VMAX LOGIC AND TIMER VMIN HOLD
+ -
RESET
1729 F02
Figure 2. Block Diagram
LTC1729 Series
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 LT1510 LT1510-5 LT1511 LT1512 LT1513 LT1769 4A Step-Down Charger with Input Current Limit 1.5A Step-Down Charger 1.5A 500kHz Step-Down Charger 3A Step-Down Charger with Input Current Limit 2A Switch SEPIC Charger 3A Switch SEPIC Charger 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.
CHARGING CURRENT
+
20mV
Figure 3. C/10 Detection Circuit
+
-
R1 0.2
R2 200
C1 1F
BAT
-
+ 20mV -
SENSE
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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 0.2 current sense resistor R1. The 100A current sink on the SENSE pin develops 20mV across the 200 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 LTC1729
IBIAS
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100A STATUS
3-SEC FILTER LOGIC AND TIMERS
CHARGE LED
COMP1
50A
1729 F03
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LTC1729 Series
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 0C to 50C 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 0C or above 50C. The 100A bias current through the 10k thermistor will generate 2.79V at 0C and 0.405V at 50C. The voltage hysteresis on COMP4 and COMP5 is designed to give 10C 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.
VMAX = 1V VMIN = 0V
BATTERY VOLTAGE
BATTERY CLAMP PULL-DOWN ON
THERMISTOR VOLTAGE
4.5V/CELL VMAX = 0V VMIN = 0V 2.7V/CELL VMAX = 0V VMIN = 1V TRICKLE CHARGE PRECONDITIONING
1729 F04
NORMAL CHARGE
Figure 4. BAT Voltage Operating Range
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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 2.79V NORMAL CHARGE 0.405V HOLD MODE 0.2V RESET MODE
1729 F05
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Figure 5. NTC Voltage Operating Range
LTC1729 Series
APPLICATIO S I FOR ATIO
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.
CHARGE
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 PAUSE IBAT = 0 STATUS = PULL-DOWN VC = PULL-DOWN VBAT > VMAX FOR MORE THAN 1SEC
VBAT > VMAX VBAT < VMAX FOR MORE THAN 1SEC
VNTC > 2.79V OR VNTC < 0.405V HOLD MODE IBAT = 0 STATUS = PREVIOUS STATUS VC = PULL-DOWN
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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.
RESET MODE IBAT = 0 STATUS = PULL-DOWN VC = PULL-DOWN VBAT > VMIN CHARGER "ON" IBAT = 1.3mA STATUS = PULL-DOWN VC = OPEN t MAX = 3HR NOTE: FOR STATUS PULL-DOWN = HARD: FOR CURRENT > C/10 PULL-DOWN = 50A: FOR CURRENT < C/10 FOR 3SEC TIME > t MAX DONE IBAT = 0 STATUS = OPEN VC = PULL-DOWN VBAT > VMAX FOR MORE THAN 1SEC NO BAT IBAT = 0 STATUS = OPEN VC = PULL-DOWN VNTC < 2.79V AND VNTC > 0.405V
1729 F06
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Figure 6. State Diagram
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LTC1729 Series
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 50A pull-down.
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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 50A 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 8 VCC LTC1729 STATUS 6 200k 3k OUT IN
1729 F07
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VDD
PROCESSOR
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 50A current source is connected to the STATUS pin. The IN pin will then be pulled high by the 3k pull-up. By forcing the OUT pin into a high impedance state, the current source will pull the pin low through the 200k resistor. When the internal timer has expired, the STATUS pin will change to high impedance state and the 200k resistor will then pull the pin high to indicate the charging has stopped. Terminate at C/10 Current Charging can also be terminated using C/10 detection before the 3-hour time-out. By connecting the low side of the NTC thermistor to the STATUS pin instead of ground,
LTC1729 Series
APPLICATIO S I FOR ATIO
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
OVP BAT 200 SENSE
Figure 8. Terminate Charging at C/10
CHARGE CURRENT
+ -
SENSE RESISTOR
Figure 9. Modify C/10 Indication to Create Charging Indicator
+
BAT
-
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current). This C/10 number is not fixed, but is set by an external resistor connected to the LTC1729 SENSE pin. A 100A 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 0, 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 2 1F 3 4 OVP BAT SENSE GND VCC VC STATUS NTC 8 7 6 5 10k NTC THERMISTOR NTHS1206N02 VISHAY/DALE
1729 F08
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VCC 0.1F VC
LTC1729
IBIAS SENSE
100A
COMP1
1729 F09
11
LTC1729 Series
TYPICAL APPLICATIO S
Wide Input Voltage Range 1A Charger
VIN 3V TO 28V
L1**
+ C3
22F ON/OFF
VIN
VSW L2** R1 29.4k R2 12.4k
S/S LT1512 VFB GND VC IFB R5 470 C5 0.1F R4 39 C4 0.33F R3 0.1
LTC1729-8.4 OVP R7 C6 100 1F BAT SENSE GND VCC VC
STATUS NTC R8 R8:10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT * TOKIN CERAMIC 1E225ZY5U-C203-F ** L1, L2 ARE TWO 10H INDUCTORS: SUMIDA CDRH6D38-100
VCC VC LTC1729 STATUS NTC
PNP: MMBT3906
12
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8 7 6 5
C2* 4.7F
D1 MBRS340
Si9925 BOOST
V+ D2 1/2 BAT85S D3 1/2 BAT85S
+
C1 22F x2
CAP + OSC LTC1044 GND LV CAP - VOUT
+
10F
R6 0.1 8.4V RPULL-UP 47k
+
C7 10F
220k
1729 TA01
Using STATUS Pin to Indicate Charge Status
TO VCC 12V
2.2k
0.1F 47k 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
10k
2k
4.7k
2k
AMBER LED
GREEN LED
LTC1729 Series
TYPICAL APPLICATIO S
4A, 2-Cell Lithium-Ion Battery Charger
DBODY M3 Si4435 R7 500 RS4 0.025
TO SYSTEM LOAD C4 D3 0.1F MMSD4148 VCC BOOST BOOSTC GBIAS CLN TGATE CLP INFET UV LT1505 SYNC SHDN FLAG CAP COMP1 R1 1k C7 0.68F SW BGATE VC PROG 3 CELL VFB 4.2V 4.1V AGND PGND BAT2 BAT SENSE SPIN R3 300 CPROG 1F RPROG 4.93k 1% C3 2.2F 5 D2 MMSD4148
VIN (FROM ADAPTER)
+
C1 1F
CIN* 47F 35V
R5 3k
R6 5.1k
C6 0.1F
C8 0.1F R8 100
* SANYO OS-CON ** SUMIDA CDRH127-150 *** AVX TPSD226L025R0200 C6 NOT NEEDED IF FLAG NOT USED LUMEX SML-LX0805GW-TR
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M1 Si4412 M2 Si4412 D4 MBRS140
C2 0.68F
RS1 0.025
L1** 15H
+
COUT*** 22F x2
+
8.4V
R4 3k C5 0.33F RS2 200 1% RS3 200 1%
LTC1729-8.4 OVP BAT SENSE GND VCC VC STATUS NTC C9 0.1F R9 1.4k D5
RPULL-UP 10k
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
PACKAGE DESCRIPTIO
0.007 (0.18) 0.021 0.006 (0.53 0.015)
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
14
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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
76
5
0.193 0.006 (4.90 0.15)
0.118 0.004** (3.00 0.102)
1 0.040 0.006 (1.02 0.15) 0 - 6 TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC
23
4 0.034 0.004 (0.86 0.102)
0.006 0.004 (0.15 0.102)
MSOP (MS8) 1098
LTC1729 Series
PACKAGE DESCRIPTIO
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
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
0.016 - 0.050 (0.406 - 1.270)
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.
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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
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
15
LTC1729 Series
TYPICAL APPLICATIO
3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger
R1 510 GND SW C2 0.47F L1** 22H D4 SS24 D3 MBR0540T COMP1 C3 220pF SPIN OVP SENSE RS2 200 1% RS1 0.05 PROG VC BAT RS3 200 1% C4 0.33F R2 1k CPROG 1F R3 300 VCC LT1511 OR LT1769 BOOST UV R6 5.1K C1* 15F D2 SS24 R5 3k CLP CLN 1F RS4 0.05 D1 SS24 INPUT POWER 11.5V TO 28V TO MAIN SYSTEM LOAD
R4 100
C5 1F
* TOKIN C55Y5U1E156Z ** SUMIDA CDRH125-220MC *** AVX TPSD226K025R0200 LUMEX SML-LX0805GW-TR D1, D2, D4: GENERAL SEMICONDUCTOR
RELATED PARTS
PART NUMBER LT1505 LT1510 LT1511 LT1512 LT1513 LT1571-1/LT1571-2 LT1571-5 LTC1731 LTC1732 LTC1759 LT1769 DESCRIPTION High Efficiency Constant-Voltage/Constant-Current Battery Charger Constant-Voltage/Constant-Current Battery charger 3A Constant-Voltage/Constant-Current Battery Charger SEPIC Battery Charger SEPIC Battery Charger 200kHz/500kHz Constant-Current/Constant-Voltage Battery Charger Family Linear Charger Linear Charger SMBus-Controlled Smart Battery Charger 2A Constant-Voltage/Constant-Current Battery Charger COMMENTS Uses External Synchronous N-Channel FETs Up to 1.5A Charge Current for Lithium-Ion, NiCd and NiMH Batteries, Internal RSENSE Charges Lithium, NiCd and NiMH Batteries VIN Can Be Higher or Lower Than Battery Voltage, 2A Switch VIN Can Be Higher or Lower Than Battery Voltage, 3A Switch Up to 1.5A Charge Current for 1- or 2-Cell Li-Ion Batteries, Preset and Adjustable Battery Voltages, C/10 Charge Detection Programmable Timer, C/10 Flag, 8-Pin MSOP Programmable Timer, C/10 Flag, AC Power Good, 10-Pin MSOP LT1505 Charger Functionality with SMBus Control 28-Pin SSOP Package
1729f LT/LCG 0800 4K * PRINTED IN USA
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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RPROG 4.93k
+
C7*** 22F
+
8.4V
LTC1729-8.4 OVP BAT SENSE GND VCC VC STATUS NTC
C6 0.1F
R7 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 TA04
(c) LINEAR TECHNOLOGY CORPORATION 1999

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