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ISL6298
Data Sheet March 9, 2006 FN9173.4
Li-ion/Li-Polymer Battery Charger
The ISL6298 is an integrated single-cell Li-ion or Li-polymer battery charger optimized for low current applications. The targeted applications include mini-disk (MD) players, Blue Tooth headsets, or other applications that use low-capacity battery cells. The ISL6298 is a linear charger that charges the battery in a CC/CV (constant current/constant voltage) profile. The charge current is programmable with an external resistor up to 450mA during the CC phase. Once the battery voltage reaches 4.2V (or 4.1V), the charger enters CV mode and the charge current starts to reduce. When the charger current drops to a user-programmable threshold, the charger indicates the end-of-charge with a STATUS pin. The charger does not actually terminate until a user-programmable total fast charge time is reached. If the battery voltage drops to a recharge threshold after termination, the charger will recharge the battery to its full capacity. The charger preconditions the battery with 20% of the programmed CC current if the battery voltage is below 2.8V. The total precharge time is limited to 1/8 of the total fast charge time. The ISL6298 features charge current thermal foldback to guarantee safe operation when the printed circuit board is space-limited for thermal dissipation. Additional features include an NTC thermistor interface for monitoring the ambient temperature, the ability to disable the time limit of the fast charge, an FAULT indication, and a thermally enhanced QFN or DFN package.
Features
* Complete Charger for Single-Cell Li-ion Batteries * Integrated Pass Element and Current Sensor * No External Blocking Diode Required * 1% Voltage Accuracy * Programmable Current Limit up to 450mA * Programmable End-of-Charge Current * Preconditioning with 20% Fast Charge Current * 10% Accuracy at 250mA * Charge Current Thermal Foldback * NTC Thermistor Interface for Battery Temperature Monitor * User Programmable Safety Timer * Ambient Temperature Range: -20C to 70C * Thermally-Enhanced QFN Packages * Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
* MD Players, Blue-Tooth Headsets and MP3 Players * Portable Instruments * PDAs, Cell Phones and Smart Phones * Stand-Alone Chargers
Related Literature
* Technical Brief TB363 "Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)" * Technical Brief TB379 "Thermal Characterization of Packaged Semiconductor Devices" * Technical Brief TB389 "PCB Land Pattern Design and Surface Mount Guidelines for QFN Packages"
Ordering Information
PART # (NOTE) ISL6298CR4Z ISL6298CR4Z-T ISL6298-2CR3Z TEMP. RANGE PART (C) MARKING PACKAGE (Pb-FREE) PKG. DWG. #
6298CR4Z -20 to 70 16 Ld 4x4 QFN L16.4x4 6298CR4Z 16 Ld 4x4 QFN Tape and Reel 982Z -20 to 70 10 Ld 3x3 DFN L10.3x3 10 Ld 3x3 DFN Tape and Reel
ISL6298-2CR3Z-T 982Z ISL6298-2CR4Z
Pinouts
ISL6298 (16 LD QFN) TOP VIEW
VBAT VBAT VIN VIN
6298CR4Z -20 to 70 16 Ld 4x4 QFN L16.4x4
ISL6298 (10 LD DFN) TOP VIEW
ISL6298-2CR4Z-T 6298CR4Z 16 Ld 4x4 QFN Tape and Reel NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
16 15 14 13 VIN 1 FAULT 2 STATUS 3 TIME 4 5 GND 6 TOEN 7 EN 8 V2P8 12 VBAT 11 TEMP 10 IMIN 9 IREF
VIN FAULT STATUS TIME GND
1 2 3 4 5
10 VBAT 9 8 7 6 TEMP IREF V2P8 EN
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2004-2006. All Rights Reserved. All other trademarks mentioned are the property of their respective owners.
ISL6298
Absolute Maximum Ratings
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 7V Output Pin Voltage (VBAT) . . . . . . . . . . . . . . . . . . . . . . -0.3 to 5.5V Signal Input Voltage (TOEN, TIME, IREF, IMIN) . . . . . . -0.3 to 3.2V Output Pin Voltage (STATUS, FAULT) . . . . . . . . . . . . . . . . -0.3 to 7V Charge Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500mA
Thermal Information
Thermal Resistance (Notes 1, 2) JA (C/W) JC (C/W) 4x4 QFN Package . . . . . . . . . . . . . . . . 41 4 3x3 DFN Package . . . . . . . . . . . . . . . . 46 4 Maximum Junction Temperature (Plastic Package) . . . . . . . . 150C Maximum Storage Temperature Range . . . . . . . . . . . -65C to 150C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300C
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . .-20C to 70C Supply Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3V to 6.5V Charge Current . . . . . . . . . . . . . . . . . . . . . . . . . . . 75mA to 450mA
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES: 1. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with "direct attach" features. See Tech Brief TB379. 2. JC, "case temperature" location is at the center of the exposed metal pad on the package underside. See Tech Brief TB379.
Electrical Specifications
Typical values are tested at VIN = 5V and 25C Ambient Temperature, maximum and minimum values are guaranteed over 0C to 70C Ambient Temperature with a supply voltage in the range of 4.3V to 6.5V, unless otherwise noted. SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
PARAMETER POWER-ON RESET Rising VIN Threshold Falling VIN Threshold (Note 3) STANDBY CURRENT VBAT Pin Sink Current VIN Pin Supply Current VIN Pin Supply Current VOLTAGE REGULATION Output Voltage Output Voltage Power MOSFET On Resistance CHARGE CURRENT Constant Charge Current Trickle Charge Current Constant Charge Current Trickle Charge Current Constant Charge Current Constant Charge Current Trickle Charge Current End-of-Charge Threshold RECHARGE THRESHOLD Recharge Voltage Threshold Recharge Voltage Threshold
3.0 2.25
3.4 2.4
4.0 2.65
V V
ISTANDBY IVIN IVIN
VIN floating or EN = LOW VBAT floating and EN pulled low VBAT floating and EN floating
-
30 1
3.0 -
A A mA
VCH VCH
For ISL6298 only For ISL6298-2 only VBAT = 3.7V, ICHARGE = 0.3A
4.059 4.158 -
4.10 4.20 0.5
4.141 4.242 -
V V
ICHARGE ITRICKLE ICHARGE ITRICKLE ICHARGE ICHARGE ITRICKLE IEOC
RIREF = 80k, VBAT = 3.7V RIREF = 80k, VBAT = 2.0V VIREF > 1.2V, VBAT = 3.7V VIREF > 1.2V, VBAT = 2.0V VIREF < 0.4V, VBAT = 3.7V, TA = 25C VIREF < 0.4V, VBAT = 3.7V, 0C ~ 50C VIREF < 0.4V, VBAT = 2.0V RIMIN = 80k
225 45 75 70 14
250 55 255 52 100 100 23 25
275 64 125 130 36
mA mA mA mA mA mA mA mA
VRECHRG VRECHRG
For ISL6298 only For ISL6298-2 only
-
3.9 4.0
-
V V
2
FN9173.4 March 9, 2006
ISL6298
Electrical Specifications
Typical values are tested at VIN = 5V and 25C Ambient Temperature, maximum and minimum values are guaranteed over 0C to 70C Ambient Temperature with a supply voltage in the range of 4.3V to 6.5V, unless otherwise noted. (Continued) SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
PARAMETER TRICKLE CHARGE THRESHOLD Trickle Charge Threshold Voltage Trickle Charge Threshold Voltage TEMPERATURE MONITORING Low Battery Temperature Threshold Low Battery Temperature Hysteresis High Battery Temperature Threshold High Battery Temperature Hysteresis Battery Removal Threshold Charge Current Foldback Threshold (Note 4) Current Foldback Gain (Note 4) OSCILLATOR Oscillation Period LOGIC INPUT AND OUTPUT TOEN Input High TOEN and EN Input Low IREF and IMIN Input High IREF and IMIN Input Low STATUS/FAULT Sink Current NOTES:
VMIN VMIN
For ISL6298 only For ISL6298-2 only
2.63 2.7
2.73 2.8
2.93 3.0
V V
VTMIN
V2P8 = 3.0V V2P8 = 3.0V
1.45 0.36 85 -
1.51 220 0.38 60 2.25 100 25
1.57 0.40 115 -
V mV V mV V C mA/C
VTMAX
V2P8 = 3.0V V2P8 = 3.0V
VRMV TFOLD GFOLD
V2P8 = 3.0V
TOSC
CTIME = 15nF
2.4
3.0
3.6
ms
2.0 1.2 Pin Voltage = 0.8V 5
-
0.8 0.4 -
V V V V mA
3. The POR falling edge voltage is guaranteed to be lower than the Trickle Charge Threshold Voltage (VMIN) by actual tests. 4. Guaranteed by characterization.
3
FN9173.4 March 9, 2006
ISL6298 Typical Operating Performance
4.25 4.24
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = 25C, RIREF = RIMIN = 80k, VBAT = 3.7V, Unless Otherwise Noted
4.216 4.214
BATTERY VOLTAGE (V)
OUTPUT VOLTAGE (V)
4.23 4.22 4.21 4.20 4.19 4.18 4.17 4.16 4.15 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
LOAD CURRENT = 10mA
4.212 4.210 4.208 4.206 4.204 4.202 4.200 0 20 40 60 80 100
CHARGE CURRENT (A)
TEMPERATURE (OC)
FIGURE 1. CHARGER OUTPUT VOLTAGE vs CHARGE CURRENT
FIGURE 2. CHARGER OUTPUT VOLTAGE vs TEMPERATURE
4.30 4.28
450 400
BATTERY VOLTAGE (V)
4.24 4.22 4.20 4.18 4.16 4.14 4.12 4.10 4.3 4.5 4.7 4.9 5.1 5.3 5.5 5.7 5.9 6.1 6.3 6.5
CHARGE CURRENT (mA)
4.26
CHARGE CURRENT = 10mA
350 300 250 200 150 100 50 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
RIREF = 50k VIREF = 0 V
INPUT VOLTAGE (V)
BATTERY VOLTAGE (V)
FIGURE 3. CHARGER OUTPUT VOLTAGE vs INPUT VOLTAGE CHARGE CURRENT IS 50mA
FIGURE 4. CHARGE CURRENT vs BATTERY VOLTAGE
500 450 400 0.45
CHARGE CURRENT (A)
RIREF = 50k
0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00
CHARGE CURRENT (mA)
350 300 250 200 150 100 50 0 0 20 40 60 80 100
RIREF = 50k
RIREF = 100k VIREF = 0 V
VIREF = 0 V
4.3 4.5 4.7 4.9 5.1 5.3 5.5 5.7 5.9 6.1 6.3 6.5
TEMPERATURE (OC)
INPUT VOLTAGE (V)
FIGURE 5. CHARGE CURRENT vs AMBIENT TEMPERATURE
FIGURE 6. CHARGE CURRENT vs INPUT VOLTAGE
4
FN9173.4 March 9, 2006
ISL6298 Typical Operating Performance
2.920
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = 25C, RIREF = RIMIN = 80k, VBAT = 3.7V, Unless Otherwise Noted (Continued)
3.00 2.95
V2P8 PIN VOLTAGE (V)
V2P8 PIN VOLTAGE (V)
LOAD CURRENT = 2 mA
2.915
2.90 2.85 2.80 2.75 2.70
2.910
2.905
2.900 3.5 4 4.5 5 5.5 6 6.5
0
2
4
6
8
10
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
FIGURE 7. V2P8 OUTPUT vs INPUT VOLTAGE
FIGURE 8. V2P8 OUTPUT vs ITS LOAD CURRENT
1000
770
MOSFET ON RESISTANCE (m)
MOSFET ON RESISTANCE (m)
900 800 700 600 500 400 0
MEASURED WITH THE 3X3 DFN PACKAGE
730 690 650 610 570 530 490 450
RIREF = 50k MEASURED AT 250mA
3X3 PACKAGE
4X4 PACKAGE
20
40
60
80
100
120
3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1
TEMPERATURE (OC)
BATTERY VOLTAGE (V)
FIGURE 9. rDS(ON) vs TEMPERATURE AT 3.7V OUTPUT
FIGURE 10. rDS(ON) vs OUTPUT VOLTAGE USING CURRENT LIMITED ADAPTERS
1.2
50
INPUT QUIESCENT CURRENT (A)
45 40 35 30 25 20 15 10 5 0 0
REVERSE CURRENT (A)
1.0 0.8 0.6 0.4 0.2 0.0 0 20 40 60 80 100
EN PIN GROUNDED
20
40
60
80
100
TEMPERATURE
(OC)
TEMPERATURE
(OC)
FIGURE 11. REVERSE CURRENT vs TEMPERATURE
FIGURE 12. INPUT QUIESCENT CURRENT vs TEMPERATURE
5
FN9173.4 March 9, 2006
ISL6298 Typical Operating Performance
50
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = 25C, RIREF = RIMIN = 80k, VBAT = 3.7V, Unless Otherwise Noted (Continued)
1.10
INPUT QUIESCENT CURRENT (mA)
INPUT QUIESCENT CURRENT (A)
45 40 35 30 25 20 15 10 5 0 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
1.05 1.00 0.95 0.90 0.85 0.80 4.2 4.5 4.8 5.1 5.4 5.7 6.0 6.3 6.6
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
FIGURE 13. INPUT QUIESCENT CURRENT vs INPUT VOLTAGE WHEN SHUTDOWN
FIGURE 14. INPUT QUIESCENT CURRENT vs INPUT VOLTAGE WHEN NOT SHUTDOWN
28 24 20
CURRENT (mA)
16 12 8 4 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
PIN VOLTAGE (V)
FIGURE 15. STATUS/FAULT PIN VOLTAGE vs CURRENT WHEN THE OPEN-DRAIN MOSFET TURNS ON
6
FN9173.4 March 9, 2006
ISL6298 Pin Description
VIN (Pin 1, 15, 16 for 4x4; Pin 1 for 3x3)
VIN is the input power source. Connect to a wall adapter.
EN (Pin 7 for 4x4; Pin 6 for 3x3)
EN is the enable logic input. Connect the EN pin to LOW to disable the charger or leave it floating to enable the charger.
Fault (Pin 2)
FAULT is an open-drain output indicating fault status. This pin is pulled to LOW under any fault conditions.
V2P8 (Pin 8 for 4x4; Pin 7 for 3x3)
This is a 2.8V reference voltage output. This pin outputs a 2.8V voltage source when the input voltage is above POR threshold and outputs zero otherwise. The V2P8 pin can be used as an indication for adapter presence.
Status (Pin 3)
STATUS is an open-drain output indicating charging and inhibit states. The STATUS pin is pulled LOW when the charger is charging a battery.
IREF (Pin 9 for 4x4; Pin 8 for 3x3)
This is the programming input for the constant charging current.
Time (Pin 4)
The TIME pin determines the oscillation period by connecting a timing capacitor between this pin and GND. The oscillator also provides a time reference for the charger.
IMIN (Pin 10 for 4x4; N/A for 3x3)
IMIN is the programmable input for the end-of-charge current. For the 3x3 DFN package, this pin is shorted to the V2P8 pin internally.
GND (Pin 5)
GND is the connection to system ground.
TEMP (Pin 11 for 4x4; Pin 9 for 3x3)
TEMP is the input for an external NTC thermistor. The TEMP pin is also used for battery removal detection.
TOEN (Pin 6 for 4x4; N/A for 3x3)
TOEN is the TIMEOUT enable input pin. Pulling this pin to LOW disables the TIMEOUT function. Leaving this pin HIGH or floating enables the TIMEOUT limit. For the 3x3 DFN package, this pin is left floating internally.
VBAT (Pin 12, 13, 14 for 4x4; Pin 10 for 3x3)
VBAT is the connection to the battery. Typically a 10F Tantalum capacitor is needed for stability when there is no battery attached. When a battery is attached, only a 1F ceramic capacitor is required.
Typical Applications
4x4 QFN Package Options
5V Wall Adapter
VIN VBAT
1F C1
TOEN
500 R1
500 R2
1 F C2
V2P8
ISL6298 D1 D2
FAULT STATUS EN V2P8 TEMP IREF IMIN
Battery Pack
RU
RT
T
1F C3
TIME
GND
R IMIN 80k
RIREF 80 k
CTIME 15nF
FIGURE 16. TYPICAL APPLICATION CIRCUIT FOR THE 4x4 QFN PACKAGE OPTIONS
7
FN9173.4 March 9, 2006
ISL6298 Typical Applications (Continued)
3x3 DFN Package Option
5V Wall Adapter
VIN VBAT
1F C1
500 R1
500 R2
1 F C2
ISL6298
(3X3 DFN)
FAULT STATUS V2P8 EN TIME IREF GND TEMP
Battery Pack
D1
D2
RT RU
1F C3
T
CTIME 15nF
RIREF 80 k
FIGURE 17. TYPICAL APPLICATION CIRCUIT FOR THE 3x3 DFN PACKAGE OPTION
3x3 DFN Package Option
5V Wall Adapter
VIN VBAT
1F C1
ISL6298
(3X3 DFN)
V2P8
1 F C2
Battery Pack
1F C3
To C
10k R1
10k R2
EN FAULT STATUS TIME TEMP IREF GND
CTIME 15nF
RIREF 80 k
FIGURE 18. TYPICAL APPLICATION CIRCUIT FOR NOT USING AN NTC THERMISTOR AND INTERFACING TO A MICRO-COMPUTER. THE TEMP PIN IS SHORT-CIRCUITED TO IREF PIN. THE INDICATIONS USES V2P8 PIN OUTPUT AS THE PULL-UP VOLTAGE.
8
FN9173.4 March 9, 2006
ISL6298 Block Diagram
QMAIN
VIN C1
VBAT
Temperature Monitoring IT
References QSEN VRECHRG 25000:1 Current Mirror ISEN VPOR VMIN VCH
V2P8
VIN
VBAT
Input_OK
+ VPOR + 100mV -
IREF RIREF IMIN RIMIN
IR Current References IMIN
+ CA CHRG + VA -
+ -
VCH +
Trickle/Fast ISEN + V2P8 Under Temp TEMP NTC Interface Over Temp Batt Removal TOEN TIME GND OSC COUNTER LOGIC MIN_I
Minbat
+
VMIN VRECHRG
Recharge
ESD Diodes VIN STATUS
STATUS VIN
FAULT Input_OK
FAULT
EN
NOTE: For the 3x3 DFN package, the TOEN pin is left floating and the IMIN pin is connected to the V2P8 pin internally. FIGURE 19. BLOCK PROGRAM
9
FN9173.4 March 9, 2006
ISL6298 Theory of Operation
The ISL6298 is an integrated charger optimized for lowcapacity single-cell Li-ion or Li-polymer batteries. It charges a battery with the constant current (CC) and constant voltage (CV) profile. The charge current is trimmed to have better than 10% accuracy at 250mA and is programmable up to 450mA. The charge voltage has 1% accuracy. Figure 20 shows the typical operating waveforms after power on. The power is applied at t0. When the input voltage reaches the power-on reset (POR) threshold at t1, the V2P8 pin starts to output a 2.8V supply. This supply also powers the internal control circuit. The POR initiates a charge cycle. Six different ways can initiate a charge cycle, as listed in Table 1.
TABLE 1. EVENTS THAT LEADS TO A NEW CHARGE CYCLE # 1 2 3 4 5 6 Power on Reset The VIN pin voltage drops below the VBAT pin voltage and then rises back above the VBAT pin voltage A new battery being inserted (detected by TEMP pin) The battery voltage drops below a recharge threshold after completing a charge cycle recovery from a battery over-temperature fault the EN pin is toggled from GND to floating EVENT
at the STATUS pin at the beginning of a charge cycle. When the EOC condition is reached, the STATUS rises to high, as shown at t4. After termination, if the battery voltage drops below a recharge threshold (t6 in Figure 20), a re-charge cycle will take place. The total time for the recharge cycle is the total fast charge time (t7 to t8). The trickle charge time is negligible in a recharge cycle. More detailed description for the operation is given below.
Power on Reset (POR)
The ISL6298 resets itself as the input voltage rises above the POR rising threshold. The V2P8 pin outputs a 2.8V voltage, the internal oscillator starts to oscillate, the internal timer is reset, and the charger begins to charge the battery. The two indication pins, STATUS and FAULT, indicate a LOW and a HIGH logic signal respectively. Figure 20 illustrates the startup of the charger between t0 to t2. The ISL6298 has a typical rising POR threshold of 3.4V and a falling POR threshold of 2.4V. The 2.4V falling threshold guarantees charger operation with a current-limited adapter to minimize the thermal dissipation. See more details on using a current-limited adapter in the ISL6292 datasheet, available at http://www.intersil.com.
Internal Oscillator
The internal oscillator (see the Block Diagram) establishes a timing reference. The oscillation period is programmable with an external timing capacitor, CTIME, as shown in Typical Applications. The oscillator charges the timing capacitor to 1.5V and then discharges it to 0.5V in one period, both with 10A current. The period TOSC is:
T OSC = 0.2 10 C TIME
6
A charge cycle goes through a trickle mode (t1 to t2), a constant current (CC) mode (t2 to t3) and a constant voltage (CV) mode (t3 to t5). The total fast charge (CC and CV) time (t2 to t5) is programmed by users to prevent charging a faulty battery for an excessively long time. At the end of the fast charge time (t5), the charger is terminated. The charger must reach an end-of-charge (EOC) condition before the termination; otherwise, the charger issues a fault indication through the FAULT pin. The charger issues a logic low signal
( sec onds )
(EQ. 1)
A 1nF capacitor results in a 0.2ms oscillation period.
Total Fast Charge Time
VIN
POR Threshold
The total fast charge time TIMEOUT is also programmed by the CTIME. A 22-stage binary counter increments each oscillation period to set the TIMEOUT, thus,
Charge Cycle
V2P8
Charge Cycle
TIMEOUT = 2
STATUS
22
C TIME T OSC = 14 ----------------1nF
( minutes )
(EQ. 2)
FAULT
15 Cycles to 1/8 TIMEOUT
A 1nF capacitor leads to 14 minutes of TIMEOUT. If a user needs to set the TIMEOUT to 3.5 hours, a 15nF capacitor is required. The charger must reach EOC before the charger terminates, otherwise, a TIMEOUT fault will be issued.
15 Cycles
VBAT
VRECHRG 2.8V VMIN IMIN
Trickle Charge Time
The trickle charge time is limited to 1/8 of TIMEOUT. If the trickle charge time (t1 to t2) exceeds the limit, a TIMEOUT fault will be issued. The end of trickle charger is determined by the battery voltage staying above the trickle charge threshold (given in the Electrical Specification) for 15 consecutive cycles of TOSC; therefore, the minimum time
FN9173.4 March 9, 2006
ICHARGE t0 t1 t2 t3 t4 t5
t6 t7
t8
FIGURE 20. TYPICAL OPERATING WAVEFORMS
10
ISL6298
the charger stays in the trickle mode is 15 cycles. Usually for a recharge cycle, the trickle charge time is 15 cycles (t6 to t7 in Figure 20). If the battery voltage falls below the trickle charge threshold during the 15 cycles, the 15-cycle counter is reset (not the total-trickle-charge-time counter) and the charger remains in the trickle mode.
End-of-Charge (EOC) Current
The EOC current IEOC sets the level at which the charger starts to indicate the end of the charge with the STATUS pin, as shown in Figure 20. The IEOC is set in two ways: 1. By connecting a resistor between the IMIN pin and ground, 2. Or by connecting the IMIN pin to the V2P8 pin. When programming with the resistor, the IEOC is set in the equation below:
V REF 0.8V I EOC = 2500 ---------------- = 2500 ---------------- ( A ) R IMIN R IMIN (EQ. 5)
Disabling TIMEOUT Limit
The TOEN pin allows the user to disable the fast charge TIMEOUT limit by pulling the TOEN pin to LOW or shorting it to GND. When this happens, the charger never terminates. The STATUS pin still issues the EOC indication when the EOC condition is reached. The EOC indication is latched and does not change until a new charge cycle starts, initiated by the events listed in Table 1. Leaving the TOEN pin floating is recommended to enable the TIMEOUT. Driving the TOEN pin above 3.0V is not recommended. The trickle charge time limit can never be disabled. For the 3x3 DFN package option, the TOEN pin is left floating internally and, therefore, the TIMEOUT cannot be disabled.
CC Mode Current Programming
The charge current is programmed by the IREF pin. There are three ways to program the charge current: 1. driving the IREF pin above 1.3V 2. driving the IREF pin below 0.4V, 3. or using the RIREF as shown in the Typical Applications. The voltage of IREF is regulated to a 0.8V reference voltage when not driven by any external source. The charging current during the CC mode is 25,000 times that of the current in the RIREF resistor. Hence, depending on how the IREF pin is used, the charge current is,
255mA 0.8V I CHARGE = ---------------- x 25000 ( A ) R IREF 100mA V IREF > 1.3V R IREF V IREF < 0.4V (EQ. 3)
where RIMIN is the resistor connected between the IMIN pin and the ground, as shown in the Typical Application Circuit. When connected to the V2P8 pin, the IEOC is set to 1/10 of ICHARGE given in EQ. 3, except when the IREF pin is shorted to GND. Under this exception, IEOC is 5mA. For the ISL6298 in the 3x3 DFN package, the IMIN pin is connected internally to the V2P8 pin.
EOC Conditions
The EOC indication is asserted when the following conditions are satisfied simultaneously: 1. The battery voltage is above the recharge threshold, and 2. The charge current is lower than the EOC current. The two conditions can prevent prematurely indicating EOC due to thermal foldback or other transient events.
Recharge
After a charge cycle is completed, charging is prohibited until the battery voltage drops to a recharge threshold, VRECHRG (see Electrical Specifications). Then a new charge cycle starts at point t6 and ends at point t8, as shown in Figure 20. The safety timer is reset at t6.
2.8V Voltage Regulator
The V2P8 pin is the output of an internal 2.8V linear regulator. The 2.8V is the voltage supply for the internal control circuit and can also be used by external circuits, such as the NTC thermistor circuit. The external load is not recommended to exceed 2mA. The V2P8 pin is recommended to be decoupled with a 1F ceramic capacitor.
The internal reference voltage at the IREF pin is capable of sourcing less than 100A current. When pulling down the IREF pin with a logic circuit, the logic circuit needs to be able to sink at least 100A current. The actual charge current may be affected by the thermal foldback function. See the Thermal Foldback section for more details.
NTC Thermistor Interface
The TEMP pin offers an interface to an external NTC thermistor. This pin has two functions: to monitor the battery ambient temperature or to monitor the insertion of the battery. The ISL6298 assumes that the NTC thermistor is inside the battery pack. The battery and the NTC thermistor are inserted or removed together. Removing the NTC thermistor disables the charger. Figure 21 shows the implementation of the TEMP pin. The comparator CP1 monitors the existence of the NTC thermistor. When the thermistor is removed, the TEMP pin voltage is
FN9173.4 March 9, 2006
Trickle Mode Current
The charge current in the trickle mode is 20% of the programmed CC mode charge current, that is:
I TRICKLE = 0.2 I CHARGE (EQ. 4)
where ICHARGE is the charge current given in EQ. 3.
11
ISL6298
pulled up to the V2P8 pin voltage, higher than the Battery Removal Threshold VRMV, and the charger is disabled. Comparators CP2 and CP3 form a window comparator and the two transistors, Q1 and Q2, create hysteresis for the two window thresholds respectively. When the TEMP pin voltage is "out of the window," determined by the VTMIN and VTMAX, the ISL6298 stops charging and indicates a fault condition. When the temperature returns to within the window, the charger re-starts a charge cycle. See the Application Information for more details on the NTC thermistor selection. of a charge cycle when the battery voltage is at its minimum but the charge current is at its maximum. The charge current thermal foldback function in the ISL6298 frees users from the over-heating concern. Figure 22 shows the typical charge curves in a charge cycle, using a constant voltage input. Once the internal temperature reaches 100C, the ISL6298 starts to reduce the charge current to prevent further temperature rise. The power dissipation is directly related to the thermal impedance, which is related to the layout of the printedcircuit board, and the ambient temperature. The dotted lines show the power limit and the current waveforms in two cases that the thermal foldback occurs. The current is reduced and gradually increases to the constant charge current as the battery voltage rises. Usually the charge current should not drop below the EOC current because of the thermal foldback. For some extreme cases if that does happen, the charger does not indicate end-of-charge unless the battery voltage is already above the recharge threshold.
Thermal Foldback
Over-heating is always a concern in a linear charger. The maximum power dissipation usually occurs at the beginning
2.8V
ISL6298
Battery Removal CP1
V2P8 R1 40K R2 60K
+
VRMV
RU
Under Temp
CP2
+
VTMIN To TEMP Pin R3 75K TEMP Q1
Indications
The ISL6298 has three indications: the input presence, the charge status, and the fault indication. The input presence is indicated by the V2P8 pin while the other two indications are presented by the STATUS pin and FAULT pin respectively.
RT
Over Temp
CP3 -
+
VTMAX Q2
R4 25K R5 4K
GND
Figure 23 shows the V2P8 pin voltage vs. the input voltage. The V2P8 pin outputs a 2.8V voltage (blue waveform) when the input voltage (yellow waveform) rises above 3.4V rising POR threshold and falls to zero volt when the input voltage falls below the 2.4V falling POR threshold. The V2P8 pin can be used as a logic signal for the input presence.
FIGURE 21. THE INTERNAL AND EXTERNAL CIRCUIT FOR THE NTC INTERFACE
Trickle Mode
Constant Current Mode
Constant Voltage Mode
Inhibit
3.4V 2.4V
VIN VCH VMIN
Input Voltage Battery Voltage
VIN
2.8V
IREF Charge Current IREF/5 P1 P2 P3 Power Dissipation
V2P8
FIGURE 23. THE V2P8 PIN OUTPUT vs THE INPUT VOLTAGE AT THE VIN PIN. VERTICAL: 1V/DIV, HORIZONTAL: 100ms/DIV
TIMEOUT
FIGURE 22. TYPICAL CHARGE CURVES USING A CONSTANT-VOLTAGE INPUT
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ISL6298
Three types of events will result in the FAULT pin to indicate a logic low signal. The following explains the causes and consequences. 1. TEMP pin voltage out of window. This is caused by the ambient temperature being out of the user-set window. When this fault occurs, the charging is halted until the temperature returns within the window. 2. TEMP pin voltage higher than the battery removal threshold. This is caused by the removal of the battery pack. The charger is disabled when the battery is removed and enabled when the battery is re-inserted. 3. TIMEOUT fault during trickle mode or CC mode. The charger is latched when this error occurs. This fault can only be cleared by cycling the input power or the EN input. The STATUS pin indicates a logic low when a charge cycle starts and indicates a high when the EOC conditions are met. Once the EOC conditions are met, the STATUS signal is latched to high until a new charge cycle. Both the STATUS and the FAULT pin need be pulled up with external resistors to the 2.8V from the V2P8 pin or the input voltage. Table 2 summarizes the STATUS and FAULT pins.
TABLE 2. INDICATION PINS FAULT STATUS High High Low High Low High INDICATION Charge completed with no fault (Inhibit) or Standby Charging in one of the three modes Fault
Applications Information
Capacitor Selection
Typically any type of capacitors can be used for the input and the output. A minimum 1F ceramic capacitor is recommended to be placed very close to the charger input. Higher value input decoupling capacitance helps the stable operation of the charger. The output capacitor selection is dependent on the availability of the battery during operation. When the battery is attached to the charger, the output capacitor can be any ceramic type with the value higher than 1F. However, if there is a chance the charger will be used as a linear regulator, a 10F tantalum capacitor is recommended. The V2P8 pin supplies power to the internal control circuit as well as external circuits. A good decoupling to this pin is very important to a reliable operation of the charger. It is recommended to use a 1F ceramic capacitor for this pin.
FAULT and STATUS Pull-Up Resistors
Both FAULT and STATUS pins are open-drain outputs that need an external pull-up resistor. It is recommended that both pins be pulled up to the input voltage or the 2.8V from the V2P8 pin, as shown in the Typical Application Circuits. If the indication pins have to be pulled up to other voltages, the user needs to examine carefully whether or not the ESD diodes will form a leakage current path to the battery when the input power is removed. If the leakage path does exist, an external transistor is required to break the path. Figure 24 shows the implementation. If the FAULT pin is directly pulled up to the VCC voltage (not shown in Figure 24), a current will flow from the VCC to the FAULT pin, then through the ESD diode to the VIN pin. Any leakage on the VIN pin, caused by an external or internal current path, will result in a current path from VCC to ground.
*Both outputs are pulled up with external resistors.
Shutdown
The ISL6298 can be shutdown by pulling the EN pin to ground. When shut down, the charger draws typically less than 30A current from the input power and less than 3A current from the battery. The 2.8V output at the V2P8 pin is also turned off. The EN pin needs be driven with an opendrain or open-collector logic output, so that the EN pin is floating when the charger is enabled.
VIN ESD Diode EN RLKG
VCC STATUS VIN or V2P8 VIN Q1 FAULT R1
Battery Leakage Current
The leakage current from the battery is different when the IC is enabled and disabled. When the IC is disabled, due to removing input power or pulling the EN pin to low, the leakage current is less than 3A. When the IC is enabled but not charging (due to a fault condition, the battery removal, or after termination), the leakage current is caused mainly by an internal 75k voltage divider for the output voltage feedback. The leakage current is approximately 56A when the battery voltage is 4.2V.
Control
GND
Note: RLKG is approximately 240k when EN is floating and is approximately 140k when the EN is grounded.
FIGURE 24. PULL-UP CIRCUIT TO AVOID BATTERY LEAKAGE CURRENT IN THE ESD DIODES.
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ISL6298
The N-channel MOSFET Q1 buffers the FAULT pin. The gate of Q1 is connected to VIN or the V2P8 pin. When the FAULT pin outputs a logic low signal, Q1 is turned on and its drain outputs a low signal as well. When FAULT is high impedance, R1 pulls the Q1 drain to high. When the input power is removed, the Q1 gate voltage is also removed, thus the Q1 drain stays high. where RCOLD and RHOT are the NTC thermistor resistance values at the cold and hot temperature limits respectively. It is usually difficult to find an NTC thermistor that has the exact ratio given in EQ. 7. A thermistor with a ratio larger than 7.08, that is:
R COLD ------------------- 7.08 R HOT (EQ. 9)
NTC Thermistor Circuit Design
As shown in Figure 21, the thresholds for the NTC circuit are formed by the internal voltage divider. Since the external circuit is also a voltage divider, the accuracy of the bias voltage, that is, the V2P8 pin voltage, becomes not critical. Figure 25 shows the typical values of the thresholds as percentages of the V2P8 pin voltage. The NTC thermistor resistance is dependent on the ambient temperature. Reducing temperature leads to the increase of the resistance as well as the TEMP pin voltage. When the TEMP pin voltage exceeds 50.3% of the bias voltage, an under-temperature fault is triggered. On the other hand, if the TEMP pin voltage is lower than 12.5%, an over temperature fault occurs. The TEMP pin voltage has to fall back to the 14.5% to 42.9% range for the fault be cleared, as shown in Figure 25. The ratio, K, of the TEMP pin voltage to the bias voltage is:
RT K = --------------------RT + RU (EQ. 6)
can be used in series with a regular resistor to form an effective thermistor that has the right ratio, as shown in Figure 26. With the series resistor RS, EQ. 7 can be rewritten as:
RS + R COLD ---------------------------------- = 7.08 RS + R
HOT
(EQ. 10)
Once the thermistor and the temperature limits are selected, RS and RU can be calculated using
R COLD - 7.08R HOT R S = -----------------------------------------------------6.08 (EQ. 11)
and
R U = 1.012 ( R S + R COLD ) (EQ. 12)
To summarize, the NTC thermistor circuit design requires three steps: 1. Find an NTC thermistor that satisfies EQ. 9. The temperature limits are determined by the application requirement. 2. Calculate the series resistance according to EQ. 11. 3. Calculate the pull-up resistance according to EQ. 12. The following is a design example. The charger is designed to charge the battery with the temperature range from 0C to 55C. The 10k NTC thermistor NCP15XH103F03RC from Murata (http://www.murata.com) satisfies EQ. 9. The resistance table is given in Table 3. The typical resistance at
Using the ratios at cold and hot temperature limits, as shown in Figure 25, resulting in:
R COLD ------------------- = 7.08 R HOT (EQ. 7)
and
R U = 1.012 R COLD (EQ. 8)
100%
V2P8
VTMIN (50.3%) VTMIN- (42.9%) TEMP Pin Voltage
RU TEMP
VTMAX+ (14.5%) VTMAX (12.5%) 0 Under Temp Over Temp
RT
GND
FIGURE 25. CRITICAL VOLTAGE LEVELS FOR TEMP PIN
FIGURE 26. EFFECTIVE NTC THERMISTOR CIRCUIT
14
Effective NTC Thermistor
FN9173.4 March 9, 2006
ISL6298
RS
ISL6298
0C and 55C are RCOLD = 27.2186k and RHOT = 3.535k respectively. Using EQ. 11 and EQ. 12 result in RS = 360 and RU = 27.9k.
Working with Current-Limited Adapter
The ISL6298 minimizes the thermal dissipation when powered by a current-limited ac adapter. The thermal dissipation can be further reduced when the adapter is properly designed. For more information regarding working with current-limited adapters, please refer to the ISL6292 datasheet available at http://www.intersil.com.
Hysteresis Temperature Calculation
Using EQ. 6 is re-arranged as:
K R T = ------------ R U - R S 1-K (EQ. 13)
Board Layout Recommendations
The ISL6298 internal thermal foldback function limits the charge current when the internal temperature reaches approximately 100C. In order to maximize the current capability, it is very important that the exposed pad under the package is properly soldered to the board and is connected to other layers through thermal vias. More thermal vias and more copper attached to the exposed pad usually result in better thermal performance. On the other hand, the number of vias is limited by the size of the pad. The exposed pad for the 4x4 QFN package is able to have 5 vias. The 3x3 DFN package allows 8 vias be placed in two rows. Since the pins on the 3x3 DFN package are on only two sides, as much top layer copper as possible should be connected to the exposed pad to minimize the thermal impedance. Refer to the ISL6298 evaluation boards for layout examples.
Substituting the ratio at the hysteresis threshold results in the NTC thermistor resistance at the threshold. Continuing the example above, the thermistor values are found to be 20.64k and 4.37k respectively at the low and high hysteresis temperatures. The corresponding temperatures are found from the Table 3 to be 7C and 49C respectively. In other words, the hysteresis temperatures for the low and high temperature limits are approximately 7C and 6C respectively.
Temperature Tolerance Calculation
The temperature accuracy is affected by the accuracy of the thresholds, RS, RU, and the NTC thermistor. Using the maximum ratio K, maximum possible RU, and minimum RS results in the maximum value of RT from EQ. 13, that is:
K MAX R T, MAX = ------------------------ R U, MAX - R S, MIN 1 - K MAX (EQ. 14)
From the Electrical Specification table, the maximum K is found to be 52.3%. Assuming the resistors have 1% accuracy, the maximum RU is 28.2k and the minimum RS is 356. The resultant maximum RT is then found to be 30.6k and the corresponding temperature is -3C. Hence the temperature tolerance is 3C. Similarly, the high temperature maximum thermistor value is 3.98k. Hence, the lowest temperature is 51C and the tolerance is 4C.
TABLE 3. RESISTANCE TABLE OF NCP15XH103F03RC TEMP (C) -3 0 6 7 50 51 55 R-Low (k) 30.3641 26.6780 20.7560 19.9227 4.0833 4.9498 3.4634 R-Center (k) 31.0200 27.2186 21.1230 20.2666 4.1609 4.0262 3.5350 R-High (k) 31.6869 27.7675 21.4944 20.6143 4.2395 4.1036 3.6076
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FN9173.4 March 9, 2006
ISL6298 Dual Flat No-Lead Plastic Package (DFN)
2X A D 0.15 C A 2X 0.15 C B
L10.3x3
10 LEAD DUAL FLAT NO-LEAD PLASTIC PACKAGE MILLIMETERS SYMBOL A A1 MIN 0.80 NOMINAL 0.90 0.20 REF 0.18 0.23 3.00 BSC 1.95 2.00 3.00 BSC 1.55 1.60 0.50 BSC 0.25 0.30 0.35 10 5 0.40 1.65 2.05 0.28 MAX 1.00 0.05 NOTES 5,8 7,8 7,8 8 2 3 Rev. 3 6/04 NOTES: 1. Dimensioning and tolerancing conform to ASME Y14.5-1994. 2. N is the number of terminals. 3. Nd refers to the number of terminals on D. 4. All dimensions are in millimeters. Angles are in degrees. 5. Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 6. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. 7. Dimensions D2 and E2 are for the exposed pads which provide improved electrical and thermal performance. 8. Nominal dimensions are provided to assist with PCB Land Pattern Design efforts, see Intersil Technical Brief TB389.
C L
6 INDEX AREA TOP VIEW
E
A3 b D D2 E E2
0.10 C
B
e k L N Nd
A C SEATING PLANE SIDE VIEW
0.08 C
A3
7 (DATUM B) 6 INDEX AREA (DATUM A) 1 2 D2
8
D2/2 NX k E2 E2/2
NX L N 8 N-1 e (Nd-1)Xe REF. BOTTOM VIEW 0.415 NX (b) 5 SECTION "C-C" C NX b (A1) 0.200 NX L NX b 5 0.10 M C A B
L e CC TERMINAL TIP
FOR ODD TERMINAL/SIDE
16
FN9173.4 March 9, 2006
ISL6298 Quad Flat No-Lead Plastic Package (QFN) Micro Lead Frame Plastic Package (MLFP)
L16.4x4
16 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE (COMPLIANT TO JEDEC MO-220-VGGC ISSUE C) MILLIMETERS SYMBOL A A1 A2 A3 b D D1 D2 E E1 E2 e k L L1 N Nd Ne P 0.25 0.50 1.95 1.95 0.23 MIN 0.80 NOMINAL 0.90 0.20 REF 0.28 4.00 BSC 3.75 BSC 2.10 4.00 BSC 3.75 BSC 2.10 0.65 BSC 0.60 16 4 4 0.60 12 0.75 0.15 2.25 2.25 0.35 MAX 1.00 0.05 1.00 NOTES 9 9 5, 8 9 7, 8 9 7, 8 8 10 2 3 3 9 9 Rev. 5 5/04 NOTES: 1. Dimensioning and tolerancing conform to ASME Y14.5-1994. 2. N is the number of terminals. 3. Nd and Ne refer to the number of terminals on each D and E. 4. All dimensions are in millimeters. Angles are in degrees. 5. Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 6. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. 7. Dimensions D2 and E2 are for the exposed pads which provide improved electrical and thermal performance. 8. Nominal dimensions are provided to assist with PCB Land Pattern Design efforts, see Intersil Technical Brief TB389. 9. Features and dimensions A2, A3, D1, E1, P & are present when Anvil singulation method is used and not present for saw singulation. 10. Depending on the method of lead termination at the edge of the package, a maximum 0.15mm pull back (L1) maybe present. L minus L1 to be equal to or greater than 0.3mm.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation's quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com 17
FN9173.4 March 9, 2006

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