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ISL6292D
Data Sheet July 2004 FN9166
Li-ion/Li Polymer Battery Charger
The ISL6292D is an integrated single-cell Li-ion or Li-polymer battery charger capable of operating with an input voltage as low as 2.4V. This charger is designed to work with various types of ac adapters or a USB port. The ISL6292D operates as a linear charger when the ac adapter is a voltage source. The battery is charged in a CC/CV (constant current/constant voltage) profile. The charge current is programmable up to 2A. The ISL6292D can also work with a current-limited adapter to minimize the thermal dissipation, in which case the ISL6292D combines the benefits of both a linear charger and a pulse charger. The ISL6292D features charge current thermal foldback to guarantee safe operation when the printed circuit board is space limited for thermal dissipation. Additional features include preconditioning of an over-discharged battery, an NTC thermistor interface for charging the battery in a safe temperature range, automatic recharge, and thermally enhanced QFN package.
Features
* Complete Charger for Single-Cell Li-ion Batteries * Integrated Pass Element and Current Sensor * No External Blocking Diode Required * Very Low Thermal Dissipation * Two-Speed Blinking Indication at Fault Conditions * 1% Voltage Accuracy * Programmable Current Limit up to 2A * Programmable End-of-Charge Current * Charge Current Thermal Foldback * NTC Thermistor Interface for Battery Temperature Monitor * Accepts Multiple Types of Adapters or USB BUS Power * Guaranteed to Operate at 2.65V After Start Up * Ambient Temperature Range: -20C to 70C * Thermally-Enhanced QFN Packages
PKG. DWG. # L16.4x4
Ordering Information
PART # ISL6292DCR4 TEMP. RANGE (C) -20 to 70 PACKAGE 16 Ld 4x4 QFN
ISL6292DCR4-T 16 Ld 4x4 QFN Tape and Reel ISL6292DCRZ (Note) -20 to 70 16 Ld 4x4 QFN (Pb-free) L16.4x4
* QFN Package: - Compliant to JEDEC PUB95 MO-220 QFN - Quad Flat No Leads - Package Outline - Near Chip Scale Package footprint, which improves PCB efficiency and has a thinner profile * Pb-free Available
ISL6292DCRZ-T 16 Ld 4x4 QFN Tape and Reel (Pb-free) (Note) NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which is 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-020B.
Applications
* Handheld Devices including Medical Handhelds * PDAs, Cell Phones and Smart Phones * Portable Instruments, MP3 Players * Self-Charging Battery Packs * Stand-Alone Chargers * USB Bus-Powered Chargers
Pinout
ISL6292D (16 LEAD QFN) TOP VIEW
VBAT VBAT VIN VIN
Related Literature
* Technical Brief TB363 "Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)"
16 15 14 13 VIN 1 STAT2 2 STAT1 3 TIME 4 5 GND 6 TOEN 7 EN 8 V2P8 12 VBAT 11 TEMP 10 IMIN 9 IREF
* Technical Brief TB379 "Thermal Characterization of Packaged Semiconductor Devices" * Technical Brief TB389 "PCB Land Pattern Design and Surface Mount Guidelines for QFN Packages"
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2004. All Rights Reserved. All other trademarks mentioned are the property of their respective owners.
ISL6292D
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 (STAT1, STAT2) . . . . . . . . . . . . . . . . . -0.3 to 7V Charge Current (For 4x4 QFN Package) . . . . . . . . . . . . . . . . . 2.1A ESD Rating Human Body Model (Per MIL-STD-883 Method 3015.7) . . .1500V Machine Model (Per EIAJ ED-4701 Method C-111) . . . . . . . .150V
Thermal Information
Thermal Resistance (Note 1) JA (C/W) JC (C/W) QFN Package (Notes 1, 2). . . . . . . . . . . 41 4 Maximum Junction Temperature (Plastic Package) . . . . . . . . 150C Maximum Storage Temperature Range . . . . . . . . . . . -65C to 150C For recommended soldering conditions, see Tech Brief TB389.
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . .-20C to 70C Supply Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3V to 6.5V
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 Dropout Voltage CHARGE CURRENT Constant Charge Current (Note 4) Trickle Charge Current Constant Charge Current Trickle Charge Current Constant Charge Current Trickle Charge Current End-of-Charge Threshold RECHARGE THRESHOLD Recharge Voltage Threshold Below VCH Recharge Voltage Threshold TRICKLE CHARGE THRESHOLD Trickle Charge Threshold Voltage
VPOR VPOR
3.0 2.25
3.5 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 VBAT = 3.7V, 0.5A
4.158 -
4.20 140
4.242 -
V mV
ICHARGE ITRICKLE ICHARGE ITRICKLE ICHARGE ITRICKLE
RIREF = 80k, VBAT = 3.7V RIREF = 80k, VBAT = 2.0V IREF Pin Voltage > 1.3V, VBAT = 3.7V IREF Pin Voltage > 1.3V, VBAT = 2.0V IREF Pin Voltage < 0.4V, VBAT = 3.7V IREF Pin Voltage < 0.4V, VBAT = 2.0V RIMIN = 80k
0.9 400 85
1.0 110 450 45 10 110
1.1 500 100 135
A mA mA mA mA mA mA
VRECHRG VRECHRG
The threshold in relative to VCH
3.85
-200 4.0
-80 -
mV V
VMIN
2.56
2.76
3.0
V
2
ISL6292D
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 TEMPERATURE MONITORING Low Battery Temperature Threshold Low Temperature Threshold Hysteresis High Battery Temperature Threshold High Temperature Threshold Hysteresis Battery Removal Threshold Charge Current Foldback Threshold (Note 5) Current Foldback Gain (Note 5) 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 STAT1/STAT2 Sink Current NOTES:
VTMIN
V2P8 = 3.0V V2P8 = 3.0V
1.40 .587 85 -
1.50 214 0.605 55 2.25 100 100
1.60 .623 115 -
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. The actual charge current may be affected by the thermal foldback function if the thermal dissipation capability is not enough or by the on resistance of the power MOSFET if the charger input voltage is too close to the output voltage. 5. Guaranteed by design, not a tested parameter.
3
ISL6292D Pin Description
VIN (Pin 1, 15, 16)
VIN is the input power source. Connect to a wall adapter.
EN (Pin 7)
EN is the enable logic input. Connect the EN pin to LOW to disable the charger or leave it floating to enable the charger.
STAT2 (Pin 2)
STAT2 is an open-drain output to indicate the charger status. This pin is pulled to LOW during charging and to HIGH when not charging. When a fault situation occurs, the pin outputs a one-speed blinking indication.
V2P8 (Pin 8)
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. Use a 1F ceramic capacitor to stabilize the internal linear regulator.
STAT1 (Pin 3)
STAT1 is an open-drain output to indicate the charger status. The STAT1 pin is pulled LOW when the charger is charging a battery and to HIGH when the charge finishes. This pin outputs two different speeds of blinking signal depending on the type of the fault case.
IREF (Pin 9)
This is the programming input for the constant charging current.
IMIN (Pin 10)
IMIN is the programmable input for the end-of-charge 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.
TEMP (Pin 11)
TEMP is the input for an external NTC thermistor. The TEMP pin is also used for battery removal detection.
GND (Pin 5)
GND is the connection to system ground.
VBAT (Pin 12, 13, 14)
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 0.1F ceramic capacitor is required as the minimum decoupling capacitor.
TOEN (Pin 6)
TOEN is the TIMEOUT enable input pin. Pulling this pin to LOW disables the TIMEOUT charge-time limit for the fast charge modes. Leaving this pin HIGH or floating enables the TIMEOUT limit.
Typical Application
5V WALL ADAPTER VIN C1 10F R1 330 TOEN VBAT C2 1F V2P8
+ -
ISL6292D
D1 TEMP STAT2 STAT1 EN V2P8 C3 1F CTIME 15nF TIME GND IREF IMIN RIMIN 80k
BATTERY PACK
RU
RT
T
RIREF 80k
4
ISL6292D Block Diagram
VIN C1
QMAIN
VBAT
Temperature Monitoring IT
References QSEN VRECHRG 100000:1 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 VIN
Recharge
STAT1 VIN STAT2
Input_OK EN
FIGURE 1. BLOCK PROGRAM
5
ISL6292D Flow Chart
Anytime VBAT>VIN, or VTEMP>2.1V, or VIN< VPOR, or EN = LOW
STOP
Charger: OFF LED: OFF VBAT VPOR and EN = HIGH
TEMP fault removed
TRICKLE CHARGE TEMP FAULT
Charger: OFF LED: Blinking (STAT1: Slow Speed STAT2: Fast Speed) TEMP fault Charger: ON LED: ON
VBAT < 2.8V when 1/8 TIMEOUT completes
TIMEOUT FAULT
Charger: OFF and latched LED: Blinking (Fast Speed for both STAT1 and STAT2) TIMEOUT completes
TEMP fault
VBAT > 2.8V before 1/8 TIMEOUT completes
FAST CHARGE TEMP FAULT
Charger: OFF LED: Blinking (STAT1: Slow Speed STAT2: Fast Speed) TEMP fault removed Charger: ON LED: ON
VBAT > 4.0V and ICHG < IMIN
TEMP fault
CHARGE COMPLETION
Charger: OFF LED: OFF
VBAT < 4.0V
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ISL6292D Theory of Operation
The ISL6292D is an integrated charger for single-cell Li-ion or Li-polymer batteries. The ISL6292D functions as a traditional linear charger when powered with a voltagesource adapter. When powered with a current-limited adapter, the charger minimizes the thermal dissipation commonly seen in traditional linear chargers. As a linear charger, the ISL6292D charges a battery in the popular constant current (CC) and constant voltage (CV) profile. The constant charge current IREF is programmable up to 2A with an external resistor or a logic input. The charge voltage VCH has 1% accuracy over the entire recommended operating condition range. The charger always preconditions the battery with 10% of the programmed current at the beginning of a charge cycle, until the battery voltage is verified to be above the minimum fast charge voltage, VMIN. This low-current preconditioning charge mode is named trickle mode. The verification takes 15 cycles of an internal oscillator whose period is programmable with the timing capacitor. A thermal-foldback feature removes the thermal concern typically seen in linear chargers. The charger reduces the charge current automatically as the IC internal temperature rises above 100C to prevent further temperature rise. The thermal-foldback feature guarantees safe operation when the printed circuit board (PCB) is space limited for thermal dissipation. A TEMP pin monitors the battery temperature to ensure a safe charging temperature range. The temperature range is programmable with an external negative temperature coefficient (NTC) thermistor. The TEMP pin is also used to detect the removal of the battery. The charger offers a safety timer for setting the fast charge time (TIMEOUT) limit to prevent charging a dead battery for an extensively long time. The TIMEOUT limit can be
Trickle Mode Constant Current Mode Constant Voltage Mode Inhibit
disabled as needed by the TOEN pin. The trickle mode is limited to 1/8 of TIMEOUT and cannot be disabled by the TOEN pin. The charger automatically re-charges the battery when the battery voltage drops below a recharge threshold. When the wall adapter is not present, the ISL6292D draws less than 3A current from the battery. Three indication pins are available from the charger to indicate the charge status. The V2P8 outputs a 2.8V dc voltage when the input voltage is above the power-on reset (POR) level and can be used as the power-present indication. This pin is capable of sourcing a 2mA current, so it can also be used to bias external circuits. The STAT1 pin is an open-drain logic output that turns LOW when the battery is being charged and turns HIGH when the EOC condition is qualified. The EOC condition is: the battery voltage rises above the recharge threshold and the charge current falls below a user-programmable EOC current threshold. Once the EOC condition is qualified, the STAT1 output rises to HIGH and is latched. The latch is released at the beginning of a charge or re-charge cycle. The STAT1 pin blinks when a fault occurs. The blinking frequency of a TIMEOUT fault is twice as fast as a temperature fault. The STAT2 pin behaves the same as the STAT1 except that it blinks at one frequency only when any fault occurs. Figure 2 shows the typical charge curves in a traditional linear charger powered with a constant-voltage adapter. From the top to bottom, the curves represent the constant input voltage, the battery voltage, the charge current and the power dissipation in the charger. The power dissipation PCH is given by the following equations:
P CH = ( V IN -V BAT ) I CHARGE (EQ. 1)
Trickle Mode
Constant Current Mode
Constant Voltage Mode
Inhibit
VIN VCH VMIN
Input Voltage Battery Voltage
VIN VCH VMIN IREF ILIM
Input Voltage Battery Voltage
IREF Charge Current IREF/10 P1 P2 P3
Charge Current IREF/10
Power Dissipation
P1 P2
Power Dissipation
FIGURE 2. TYPICAL CHARGE CURVES USING A CONSTANT-VOLTAGE ADAPTER
FIGURE 3. TYPICAL CHARGE CURVES USING A CURRENTLIMITED ADAPTER
7
ISL6292D
where ICHARGE is the charge current. The maximum power dissipation occurs during the beginning of the CC mode. The maximum power the IC is capable of dissipating is dependent on the thermal impedance of the printed-circuit board (PCB). Figure 2 shows, with dotted lines, two cases that the charge currents are limited by the maximum power dissipation capability due to the thermal foldback. When using a current-limited adapter, the thermal situation in the ISL6292D is totally different. Figure 3 shows the typical charge curves when a current-limited adapter is employed. The operation requires the IREF to be programmed higher than the limited current ILIM of the adapter, as shown in Figure 3. The key difference of the charger operating under such conditions occurs during the CC mode. The Block Diagram, Figure 1, aids in understanding the operation. The current loop consists of the current amplifier CA and the sense MOSFET QSEN. The current reference IR is programmed by the IREF pin. The current amplifier CA regulates the gate of the sense MOSFET QSEN so that the sensed current ISEN matches the reference current IR. The main MOSFET QMAIN and the sense MOSFET QSEN form a current mirror with a ratio of 100,000:1, that is, the output charge current is 100,000 times IR. In the CC mode, the current loop tries to increase the charge current by enhancing the sense MOSFET QSEN, so that the sensed current matches the reference current. On the other hand, the adapter current is limited, the actual output current will never meet what is required by the current reference. As a result, the current error amplifier CA keeps enhancing the QSEN as well as the main MOSFET QMAIN, until they are fully turned on. Therefore, the main MOSFET becomes a power switch instead of a linear regulation device. The power dissipation in the CC mode becomes:
P CH = R DS ( ON ) I CHARGE
2
Figure 4 illustrates the typical signal waveforms for the linear charger from the power-up to a recharge cycle. More detailed Applications Information is given below.
Applications Information
Power on Reset (POR)
The ISL6292D 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, STAT1 and STAT2, indicate LOW. Figure 4 illustrates the start up of the charger between t0 to t2. The ISL6292D 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 currentlimited adapter to minimize the thermal dissipation.
Charge Cycle
A charge cycle consists of three charge modes: trickle mode, constant current (CC) mode, and constant voltage (CV) mode. The charge cycle always starts with the trickle mode until the battery voltage stays above VMIN (2.8V typical) for 15 consecutive cycles of the internal oscillator. If the battery voltage drops below VMIN during the 15 cycles, the 15-cycle counter is reset and the charger stays in the trickle mode. The charger moves to the CC mode after verifying the battery voltage. As the battery-pack terminal voltage rises to the final charge voltage VCH, the CV mode begins. The terminal voltage is regulated at the constant VCH in the CV mode and the charge current is expected to decline. After the charge current drops below IMIN, the ISL6292D indicates the end-of-charge (EOC) with the STAT1 or STAT2 pin and terminates. Signals in a charge cycle are illustrated in Figure 4 between points t2 to t5.
(EQ. 2)
where rDS(ON) is the resistance when the main MOSFET is fully turned on. This power is typically much less than the peak power in the traditional linear mode. The worst power dissipation when using a current-limited adapter typically occurs at the beginning of the CV mode, as shown in Figure 3. The equation EQ.1 applies during the CV mode. When using a very small PCB whose thermal impedance is relatively large, it is possible that the internal temperature can still reach the thermal foldback threshold. In that case, the IC is thermally protected by lowering the charge current, as shown with the dotted lines in the charge current and power curves. Appropriate design of the adapter can further reduce the peak power dissipation of the ISL6292D. See the Application Information section for more information.
VIN
POR Threshold
V2P8
Charge Cycle
Charge Cycle
STAT1 STAT2
15 Cycles to 1/8 TIMEOUT
VBAT
VRECHRG 2.8V VMIN IMIN
15 Cycles
ICHARGE t0 t1 t2 t3 t4 t5
t6 t7
t8
FIGURE 4. OPERATION WAVEFORMS
8
ISL6292D
The following events initiate a new charge cycle: * POR, * a new battery being inserted (detected by TEMP pin), * the battery voltage drops below a recharge threshold after completing a charge cycle, * recovery from an battery over-temperature fault, * or, the EN pin is toggled from GND to floating. Further description of these events are given later in this data sheet.
Disabling TIMEOUT Limit
The TIMEOUT limit for the fast charge modes can be disabled by pulling the TOEN pin to LOW or shorting it to GND. When this happens, the charger becomes a currentlimited LDO (low-dropout) supply with its voltage regulated at the final charge voltage VCH and the current limit determined by the IREF pin. If the LDO load current drops below the end-of-charge current (refer to End-of-Charge section), the STAT1 and the STAT2 pin will indicate. The trickle charge time limit, however, is not disabled even when the TOEN pin is pulled to LOW. The charger operates in the trickle mode at the beginning of a charge cycle even if the TIMEOUT is disabled. Leaving the TOEN pin floating is recommended to enable the TIMEOUT. Driving the TOEN pin above 3.0V is not recommended.
Recharge
After a charge cycle completes, 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 4. The safety timer is reset at t6.
Charge 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 constant current mode is 100,000 times that of the current in the RIREF resistor. Hence, depending on how IREF pin is used, the charge current is,
I REF = 500mA 5 0.8V ---------------- x 10 ( A ) R IREF 100mA V IREF > 1.3V R IREF V IREF < 0.4V (EQ. 5)
Internal Oscillator
The internal oscillator 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
( sec onds )
(EQ. 3)
A 1nF capacitor results in a 0.2ms oscillation period. The accuracy of the period is mainly dependent on the accuracy of the capacitance and the internal current source.
Total Charge Time
The total charge time for the CC mode and CV mode is limited to a length of TIMEOUT. A 22-stage binary counter increments each oscillation period of the internal oscillator to set the TIMEOUT. The TIMEOUT can be calculated as:
TIMEOUT = 2
22
C TIME T OSC = 14 ----------------1nF
( minutes )
(EQ. 4)
The 500mA current is a guaranteed maximum value for high-power USB port, with the typical value of 450mA. The 100mA current is also a guaranteed maximum value for the low-power USB port. This design accommodates the USB power specification. 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. When the adapter is current limited, it is recommended that the reference current be programmed to at least 30% higher than the adapter current limit (which equals the charge current). In addition, the charge current should be at least 350mA so that the voltage difference between the VIN and the VBAT pins is higher than 100mV. The 100mV is the offset voltage of the input-output voltage comparator shown in the block diagram.
A 1nF capacitor leads to 14 minutes of TIMEOUT. For example, a 15nF capacitor sets the TIMEOUT to be 3.5 hours. The charger has to reach the end-of-charge condition before the TIMEOUT, otherwise, a TIMEOUT fault is issued. The TIMEOUT fault latches up the charger. There are two ways to release such a latch-up: either to recycle the input power, or toggle the EN pin to disable the charger and then enable it again. The trickle mode charge has a time limit of 1/8 TIMEOUT. If the battery voltage does not reach VMIN within this limit, a TIMEOUT fault is issued and the charger latches up. The charger stays in trickle mode for at least 15 cycles of the internal oscillator and, at most, 1/8 of TIMEOUT, as shown in Figure 4.
9
ISL6292D
End-of-Charge (EOC) Current
The end-of-charge current IMIN sets the level at which the charger indicates the end of the charge with the STAT1 and STAT2 pins, as shown in Figure 4. The charger terminates at this moment. The IMIN is set in two ways, by connecting a resistor between the IMIN pin and ground, or by connecting the IMIN pin to the V2P8 pin. When programming with the resistor, the IMIN is set in the equation below.
V REF 4 0.8V I MIN = 10000 ---------------- = ---------------- x10 ( A ) R IMIN R IMIN (EQ. 6)
2.8V Bias Voltage
The ISL6292D provides a 2.8V voltage for biasing the internal control and logic circuit. This voltage is also available for external circuits such as the NTC thermistor circuit. The maximum allowed external load is 2mA.
NTC Thermistor
The ISL6292D uses two comparators (CP2 and CP3) to form a window comparator, as shown in Figure 7. When the TEMP pin voltage is "out of the window," determined by the VTMIN and VTMAX, the ISL6292D stops charging and indicates a fault condition. When the temperature returns to the set range, the charger re-starts a charge cycle. The two MOSFETs, Q1 and Q2, produce hysteresis for both upper and lower thresholds. The temperature window is shown in Figure 6.
3.0V
where RIMIN is the resistor connected between the IMIN pin and the ground. When connected to the V2P8 pin, the IMIN is set to 1/10 of IREF, except when the IREF pin is shorted to GND. Under this exception, IMIN is 5mA.
Charge Current Thermal Foldback
Over-heating is always a concern in a linear charger. The maximum power dissipation usually occurs at the beginning 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 ISL6292D frees users from the over-heating concern. Figure 5 shows the current signals at the summing node of the current error amplifier CA in the Block Diagram. IR is the reference. IT is the current from the Temperature Monitoring block. The IT has no impact on the charge current until the internal temperature reaches approximately 100C; then IT rises at a rate of 1A/C. When IT rises, the current control loop forces the sensed current ISEN to reduce at the same rate. As a mirrored current, the charge current is 100,000 times that of the sensed current and reduces at a rate of 100mA/C. For a charger with the constant charge current set at 1A, the charge current is reduced to zero when the internal temperature rises to 110C. The actual charge current settles between 100C to 110C.
IR
VTMIN (1.50V) VTMIN(1.286V) TEMP Pin Voltage
VTMAX+ (0.660V) VTMAX (0.605V) 0V Under Temp Over Temp
FIGURE 6. CRITICAL VOLTAGE LEVELS FOR TEMP PIN
2.8V
ISL6292D
R1 Battery Removal CP1
V2P8
+
VRMV R2 VTMIN R3 To TEMP Pin TEMP Q1 RU
IT
Under Temp CP2
+
ISEN
100OC
Temperature
Over Temp CP3 R4 VTMAX Q2 R5 GND RT
FIGURE 5. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT
+
Usually the charge current should not drop below IMIN because of the thermal foldback. For some extreme cases if that does happen, the charger does not indicate end-ofcharge unless the battery voltage is already above the recharge threshold.
FIGURE 7. THE INTERNAL AND EXTERNAL CIRCUIT FOR THE NTC INTERFACE
10
ISL6292D
As the TEMP pin voltage rises from low and exceeds the 1.5V threshold (when the V2P8 pin is forced with a 3V bias), the under temperature signal rises and does not clear until the TEMP pin voltage falls below the 1.286V falling threshold. Similarly, the over-temperature signal is given when the TEMP pin voltage falls below the 0.605V threshold and does not clear until the voltage rises above 0.66V. The actual accuracy of the 3V bias is not important because all the thresholds and the TEMP pin voltage are ratios determined by the resistor dividers, as shown in Figure 7. The NTC thermistor is required to have a resistance ratio of 3.96:1 at the low and the high temperature limits, that is,
R COLD ------------------- = 3.96 R HOT (EQ. 7)
TIME OSC Output DFF1 Output
CTIME
STAT1
STATUS Temp Fault TIMEOUT Fault
STAT2
TIME
OSC
DFF1
DFF8 DFF9
(A)
This is because at the low temperature limit, the TEMP pin voltage is 1.5V, which is 1/2 of the 3V bias. Thus,
R COLD = R U (EQ. 8)
where RU is the pull-up resistor as shown in Figure 7. On the other hand, at the high temperature limit the TEMP pin voltage is 0.605V, 20.17% of the 3V bias. Therefore,
R HOT 0.2017 --------------- = -------------------------1 - 0.2017 RU (EQ. 9)
DFF8 Output DFF9 Output
(B)
FIGURE 9. EQUIVALENT CIRCUIT FOR THE STAT1/STAT2 INDICATION PINS AND KEY OPERATING WAVEFORMS
For applications that do not need to monitor the battery temperature, the NTC thermistor can be replaced with a regular resistor of a half value of the pull up resistor RU. Another option is to connect the TEMP pin to the IREF pin that has a 0.8V output. With such connection, the IREF pin can no longer be programmed with logic inputs.
When the charger senses a TEMP pin voltage that is 2.1V or higher, it assumes that the battery is removed. The battery removal detection circuit is also shown in Figure 7. When a battery is removed, the charger is stopped. When a battery is inserted again, a new charge cycle starts.
Battery Removal Detection
The ISL6292D assumes that the thermistor is co-packed with the battery and is removed together with the battery.
Indications
The ISL6292D has three indication pins: V2P8, STAT1, and STAT2. The input presence is indicated by the V2P8 pin. Figure 8 shows the V2P8 pin voltage vs. the input voltage. The equivalent circuit for the STAT1 and STAT2 pins are shown in Figure 9. Both pins have ESD diodes to clamp the pin voltage between ground and the input, as shown in the Block Diagram. The STATUS block outputs a logic HIGH when the charger is charging and a LOW whenever the charger is not charging. When a fault case happens, the charger stops charging, therefore, the STATUS block outputs LOW. Depending on fault cause, either the eighth or the ninth D-type flip-flop output is gated to the STAT1 pin. Both flip-flop outputs are 50% duty ratio blinking signals. The periods of the eighth and ninth flip-flop output are calculated by the following equations:
T 8th = 2 T OSC = 256 T OSC
8
3.4V 2.4V
VIN
2.8V
V2P8
(EQ. 10) (EQ. 11)
FIGURE 8. THE V2P8 PIN OUTPUT vs THE INPUT VOLTAGE AT THE VIN PIN. VERTICAL: 1V/DIV, HORIZONTAL: 100ms/DIV
T 9th = 2 T OSC = 512 T OSC
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Table 1 and 2 summarize the LED indication driven by STAT1 and STAT2 respectively.
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ISL6292D
TABLE 1. SUMMARY OF CHARGE STATUS AND LED OUTPUT STATUS Charging Charge Completed or Disabled Temperature Fault TIMEOUT Fault On OFF Blinks at the speed of T9th Blinks at the speed of T8th LED OUTPUT
Shutdown
The ISL6292D 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 the 2.8V output at the V2P8 pin is also turned off. The EN pin needs be driven with an open-drain or open-collector logic output, so that the EN pin is floating when the charger is enabled.
Input and Output Capacitor Selection
Typically any type of capacitors can be used for the input and the output. A 0.47F or higher value ceramic capacitor for the input is recommended to be placed very close to the input pin and the ground pin. Another 10F capacitance is required to stabilize the input voltage. When the battery is attached to the charger, the output capacitor can be any ceramic type with the value higher than 0.1F. However, if there is a chance the charger will be used as an LDO linear regulator, a 10F tantalum capacitor is recommended.
TABLE 2. SUMMARY OF CHARGE STATUS AND LED OUTPUT STATUS Charging Charge Completed or Disabled Fault On OFF Blinks at the speed of T8th LED OUTPUT
Working with Current-Limited Adapter
The ISL6292D can work with a current-limited adapter to significantly reduce the thermal dissipation during charging. Refer to the ISL6292 datasheet, which can be found at http://www.intersil.com, for more details.
Board Layout Recommendations
The ISL6292D 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 will result in better thermal performance. On the other hand, the number of vias is limited by the size of the pad. The exposed pads for the 4x4 QFN package is able to have 5 vias. Refer to the ISL6292 evaluation boards for layout examples.
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ISL6292D 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.
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