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| (R) ISL6292C Data Sheet July 22, 2005 FN9133.2 Li-ion/Li Polymer Battery Charger The ISL6292C 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. The ISL6292C 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 with an external resistor up to 1.5A. The ISL6292C can also work with a current-limited adapter to minimize the thermal dissipation, in which case the ISL6292C combines the benefits of both a linear charger and a pulse charger. The ISL6292C 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, automatic recharge, and thermally enhanced DFN package. Features * Complete Charger for Single-Cell Li-ion Batteries * Very Low Thermal Dissipation * Integrated Pass Element and Current Sensor * No External Blocking Diode Required * 1% Voltage Accuracy * Programmable Current Limit up to 1.5A * Charge Current Thermal Foldback * Accepts Multiple Types of Adapters * Guaranteed to Operate at 2.65V After Start Up * Ambient Temperature Range: -20C to 70C * Thermally-Enhanced DFN Packages * Pb-Free Plus Anneal Available (RoHS Compliant) 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 Ordering Information TEMP. PART # (NOTE) RANGE (C) ISL6292CCR3Z -20 to 70 PACKAGE PKG. DWG. # 10 Ld 3x3 DFN (Pb-free) L10.3x3 ISL6292CCR3Z-T 10 Ld 3x3 DFN Tape and Reel (Pb-free) 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. 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" Typical Application Circuit 5V Input C1 VIN VBAT ISL6292C C2 Pinout ISL6292C (3x3 DFN) TOP VIEW FAULT STATUS VSEN V2P8 Floating to Enable EN TIME IREF GND VIN C3 1 2 3 4 5 10 VBAT 9 8 7 6 VSEN IREF V2P8 EN FAULT STATUS CTIME RIREF TIME GND 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. 2004-2005. All Rights Reserved. All other trademarks mentioned are the property of their respective owners. ISL6292C Absolute Maximum Ratings Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 7V Output Pin Voltage (BAT, VSEN, V2P8). . . . . . . . . . . . . -0.3 to 5.5V Signal Input Voltage (TIME, IREF). . . . . . . . . . . . . . . . . -0.3 to 3.2V Output Pin Voltage (STATUS, FAULT) . . . . . . . . . . . . . . . . -0.3 to 7V Charge Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6A ESD Rating Human Body Model (Per MIL-STD-883 Method 3015.7) . . .2500V Machine Model (Per EIAJ ED-4701 Method C-111) . . . . . . . .200V Thermal Information Thermal Resistance (Notes 1, 2) . . . . . . . JA (C/W) JC (C/W) 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 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 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 3) Trickle Charge Current End-of-Charge Threshold RECHARGE THRESHOLD Recharge Voltage Threshold TRICKLE CHARGE THRESHOLD Trickle Charge Threshold Voltage TEMPERATURE MONITORING Charge Current Foldback Threshold (Note 4) Current Foldback Gain (Note 4) 3.0 2.25 3.4 2.4 3.95 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 4.20 - 4.256 175 4.30 - V mV ICHARGE ITRICKLE IMIN RIREF = 80k, VBAT = 3.7V RIREF = 80k, VBAT = 2.0V RIREF = 80k 0.9 85 1.0 110 110 1.1 135 A mA mA VRECHRG 3.90 4.053 4.155 V VMIN 2.73 2.84 3.04 V TFOLD GFOLD 85 - 100 100 115 - C mA/C 2 FN9133.2 July 22, 2005 ISL6292C 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 OSCILLATOR Oscillation Period LOGIC OUTPUTS STATUS/FAULT Sink Current NOTES: TOSC CTIME = 15nF 2.4 3.0 3.6 ms Pin Voltage = 0.8V 5 - - mA 3. 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. 4. Guaranteed by design, not a tested parameter. Pin Descriptions VIN (Pin 1) VIN is the input power source. Connect to a wall adapter. EN (Pin 6) 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. Any time a FAULT condition happens, it will reset the counter of the charger. V2P8 (Pin 7) This is a 2.8V reference voltage output. This pin outputs a 2.8V voltage source when the input voltage is above POR threshold, otherwise it outputs zero. 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. It will be forced to high impedance when the charge current drops to IMIN. This high impedance mode will be latched until a recharge cycle or a new charge cycle starts. IREF (Pin 8) This is the programming input for the constant charging current. It maintains at 0.8V when the charger is in normal operation. VSEN (Pin 9) VSEN is the remote voltage sense pin. Connect this pin as close as possible to the battery pack positive connection. If the VSEN pin is floating, its voltage drops to zero volt and the charger operates in the Trickle mode. 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. VBAT (Pin 10) 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. GND (Pin 5) GND is the connection to system ground. 3 FN9133.2 July 22, 2005 ISL6292C Typical Applications 5V WALL ADAPTER VIN C1 10F VBAT C2 10F ISL6292C D1 D2 VSEN FAULT STATUS V2P8 EN TIME CTIME 15nF IREF GND RIREF 80k C3 1F BATTERY PACK R1 1k R2 1k Block Diagram VIN C1 QMAIN VBAT TEMPERATURE MONITORING IT REFERENCES QSEN VRECHRG 100000:1 Current Mirror ISEN Input_OK + VPOR + 100mV VPOR VCH V2P8 VMIN VIN VSEN IREF R IREF IR CURRENT REFERENCES IMIN = IR /10 + CA CHRG + VA - + - VCH + Trickle/Fast ISEN + MIN_I Recharge Minbat VMIN + VIN VRECHR G Input_OK LOGIC ESDDiode STATUS EN STATUS VIN TIME GND OSC COUNTER FAULT FAULT FIGURE 1. BLOCK DIAGRAM 4 FN9133.2 July 22, 2005 ISL6292C Charging Flow Chart Power Up VIN>VPOR ? N Y POR Initialization Reset counter CC Charge Trickle Charge CV Charge VSEN>=VCH? VSEN>VMIN? Y N N Y Ich < IMIN ? Y N N N Trickle Charge 1/8 TIMEOUT? N TIMEOUT? Constant Voltage Charge TIMEOUT? N Y Y Constant Current Charge Y set FAULT low latch up charger EOC indication: set STATUS high keep FAULT high N charger inhibited reset counter N EN toggled ? TIMEOUT? N Y VSEN < VRECHRG? Y Start recharge Inhibit N Y EOC or FAULT FIGURE 2. CHARGING FLOW CHART 5 FN9133.2 July 22, 2005 ISL6292C Theory of Operation The ISL6292C is an integrated charger for single-cell Li-ion or Li-polymer batteries. The ISL6292C 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 ISL6292C charges a battery in the popular constant current (CC) and constant voltage (CV) profile. The constant charge current IREF is programmable up to 1.5A with an external resistor. 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 lowcurrent 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. 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 trickle mode is limited to 1/8 of TIMEOUT. The charger automatically re-charges the battery when the battery voltage drops below a recharge threshold. When the wall adapter is not present, the ISL6292C draws less than 1A current from the battery. Trickle Mode Constant Current Mode Constant Voltage Mode Inhibit 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 STATUS pin is an open-drain logic output that turns LOW at the beginning of a charge cycle until the end-ofcharge (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 STATUS output rises to HIGH and is latched. The latch is released at the beginning of a charge or re-charge cycle. The open-drain FAULT pin turns low when a charge time fault occurs or when the IREF pin is pulled below 0.35V or above 1.4V. Figure 3 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 equation: P CH = ( V IN - V BAT ) I CHARGE (EQ. 1) 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 3 shows, with dotted lines, two cases that the charge currents are limited by the maximum power dissipation capability due to the thermal foldback. 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 Power Dissipation Charge Current IREF/10 P1 P2 TIMEOUT Power Dissipation TIMEOUT FIGURE 3. TYPICAL CHARGE CURVES USING A CONSTANT-VOLTAGE ADAPTER FIGURE 4. TYPICAL CHARGE CURVES USING A CURRENTLIMITED ADAPTER 6 FN9133.2 July 22, 2005 ISL6292C When using a current-limited adapter, the thermal situation in the ISL6292C is totally different. Figure 4 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 4. 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 LOW and a HIGH logic signal respectively. Figure 5 illustrates the start up of the charger between t0 to t2. The ISL6292C 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 (2.84V 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 (1/10 of IREF, see Endof-Charge Current for more detail), the ISL6292C indicates the end-of-charge (EOC) with the STATUS pin. The charging actually does not terminate until the internal timer completes its length of TIMEOUT in order to bring the battery to its full capacity. Signals in a charge cycle are illustrated in Figure 5 between points t2 to t5. The following events initiate a new charge cycle: * POR, * the battery voltage drops below a recharge threshold after completing a charge cycle, * or, the EN pin is toggled from GND to floating. Further description of these events are given later in this data sheet. (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 4. The equation 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 by the dotted lines in the charge current and power curves. Appropriate design of the adapter can further reduce the peak power dissipation of the ISL6292C. See the Application Information section of the ISL6292 data sheet (www.intersil.com) for more information. Figure 5 illustrates the typical signal waveforms for the linear charger from the power-up to a recharge cycle. More detailed Applications Information is given below. VIN POR Threshold V2P8 Charge Cycle Charge Cycle STATUS FAULT 15 Cycles to 1/8 TIMEOUT Applications Information Power on Reset (POR) The ISL6292C 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 7 VBAT VRECHRG 2.8V VMIN IMIN 15 Cycles ICHARGE t0 t1 t2 t3 t4 t5 t6 t7 t8 FIGURE 5. OPERATION WAVEFORMS FN9133.2 July 22, 2005 ISL6292C 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 5. The safety timer is reset at t6. TABLE 1. CHARGE CURRENT vs RIREF VALUES (Note) CHARGE CURRENT (mA) RIREF (k) 267 160 100 88.9 80 MIN 250 450 720 810 900 TYP 300 500 800 900 1000 MAX 350 550 880 990 1100 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 NOTE: The limits are still preliminary. Additional samples will be tested for the final results. Table 1 shows the charge current vs. selected RIREF values. The ISL6292C is designed to be safe when the IREF pin is accidentally short-circuited to an external source or to ground. If the IREF pin is driven by an external source to below 0.38V or above 1.5V for any reason, the charger is disabled and the FAULT pin turns to LOW to indicate a fault condition. The charger will resume charging after the fault condition is removed. When the IREF is driven by a voltage between 0.38V to 0.5V (typical value), the charge current is limited to 100mA; or when driven to a voltage between 1.2V to 1.5V, the charge current is limited to 500mA. For any voltage between 0.5V to 1.2V, the charge current will drop to a very low value. This feature can protect the charger from a large charging current when IREF is accidentally shorted to ground or to a high voltage. Figure 6 shows the charge current when the IREF pin voltage is driven from 0V to 3V. ( 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) 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 5. End-of-Charge (EOC) Current The EOC current IMIN sets the level at which the charger starts to indicate the end of the charge with the STATUS pin, as shown in Figure 5. The charger actually does not terminate charging until the end of the TIMEOUT, as described in the Total Charge Time section. In the GND STATUS 5V/Div IREF Pin Voltage 500mV/Div Charge Current Programming The charge current in the CC mode is programmed by the IREF pin. The voltage of IREF is regulated to a 0.8V reference voltage. The charging current during the constant current mode is 100,000 times that of the current in the RIREF resistor. Hence, the charge current is, 5 0.8V I REF = ---------------- x 10 ( A ) R IREF Time Scale 40s/Div Charge Current 200mA/Div GND GND (EQ. 5) FIGURE 6. CHARGE CURRENT WHEN IREF PIN IS DRIVEN BY AN EXTERNAL VOLTAGE SOURCE 8 FN9133.2 July 22, 2005 ISL6292C Indications IR IT I SEN The ISL6292C 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. Figure 8 shows the V2P8 pin voltage vs. the input voltage. Table 2 summarizes the other two pins. 100O C TEMPERATURE 3.4V 2.4V FIGURE 7. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT. ISL6292C, the EOC current is internally set to 1/10 of the CC charge current, that is, 1 I MIN = ----- I REF 10 (EQ. 6) VIN 2.8V At the EOC, the STATUS signal rises to HIGH and is latched. The latch is not reset until a recharge cycle or a new charge cycle starts. V2P8 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 ISL6292C frees users from the over-heating concern. Figure 7 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. 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 8. THE V2P8 PIN OUTPUT vs THE INPUT VOLTAGE AT THE VIN PIN. VERTICAL: 1V/DIV, HORIZONTAL: 100ms/DIV TABLE 2. STATUS INDICATIONS 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 NOTE: Both outputs are pulled up with external resistors. Shutdown The ISL6292C 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. If the EN pin is driven by an external source, the POR threshold voltage will be affected. Input and Output Capacitor Selection Typically any type of capacitors can be used for the input and the output. Use of a 0.47F or higher value ceramic capacitor for the input is recommended. 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. 2.8V Bias Voltage The ISL6292C 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. 9 FN9133.2 July 22, 2005 ISL6292C Stability With Large Ceramic Output Capacitors The ISL6292C partially relies on the ESR (equivalent series resistance) of the output capacitor for the loop stability. When the system has a large ceramic capacitor or a number of ceramic capacitors in parallel, the ESR value can be too low for a stable operation. A low-value resistor should be inserted between the sensed feedback (VSEN pin) and the external large-value ceramic capacitor to improve the stability, as shown in Figure 9. In applications that have a sense resistor between the VBAT pin and the VSEN pin, such as the R1 shown in Figure 10, two small resistors can be used to create an equivalent low value resistor between the VSEN pin and the large capacitor, to avoid another more expensive low-value sense resistor. R2 and R3 in Figure 10 show how the two resistors are connected. The equivalent low-value resistance is, R3 R eq = -------------------- R 1 R2 + R3 (EQ. 7) To INPUT ISL6292C VIN VBAT R2 20 VSEN GND R3 20 R1 150m To Battery C1 10F Ceramic C2 Large Ceramic Capacitor FIGURE 10. THE CIRCUIT TO GENERATE THE EQUIVALENT LOW-VALUE RESISTOR Working with Current-Limited Adapter The ISL6292C can work with a current-limited adapter to significantly reduce the thermal dissipation during charging. Refer to the ISL6292 data sheet, which can be found at http://www.intersil.com, for more details. Board Layout Recommendations The ISL6292C 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 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 ISL6292 evaluation boards for layout examples. The value of (R2 + R3) should be significantly larger than that of the sense resistor R1 to minimize the accuracy of the current sensing. The parallel value of R2 and R3 should be significantly smaller than 72k (internal resistive divider value for setting the charger output voltage) to minimize the impact on the output voltage. Figure 10 shows two 20 resistor. The sum is 40, much higher than the 150m R1. The parallel value is 10, negligible compared to the 72k resistive divider. Such a selection is a good trade-off to result in 75m equivalent low-value resistance between the VSEN pin and the large capacitor. ISL6292C To INPUT VIN VBAT R1 75m To Battery C1 10F Ceramic VSEN GND C2 Large Ceramic Capacitor FIGURE 9. INSERTING R1 TO IMPROVE THE STABILITY OF APPLICATIONS WITH LARGE CERAMIC CAPACITOR IS USED AT THE OUTPUT 10 FN9133.2 July 22, 2005 ISL6292C 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 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 11 FN9133.2 July 22, 2005 |
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