1
®
FN9139 .1
ISL6292B
Li-ion/Li Polymer Battery Charger
The ISL6292B uses Intersil’s patent-pending dual-mode
charge technology to minimize the heat in a linear charger.
The ISL6292B is a modification of the original ISL6292 and
is optimized for cellular phone travel charger applications.
The low-heat generation feature of the dual-mode charger
enables the charger IC to be placed inside the connector of
the travel charger to completely remove the influence of the
adapter cable on the charging performance.
Working with a current-limited ac/dc converter, the dual-
mode charger charges a Li-ion battery with the same current
profile as a traditional linear charger. The constant charge
current is determined by the current limit of the ac/dc
converter. The constant output voltage is fixed at 4.2V. When
the battery voltage is below 2.8V, the charger preconditions
the battery with a low trickle-charge current. The charge
status is indicated by a tri-color LED. A safety timer prevents
charging a dead battery for an excessively long period.
The ISL6292B also features a thermal foldback function that
automatically reduces the charge current when the internal
die temperature exceeds a 100°C limit to prevent further
temperature rise. This function removes the concern of
thermal failure in the targeted space-limited applications. An
ambient temperature monitoring circuit allows users to set
two separate temperature limit levels, one for during charge
and one for not during charge. The thermally-enhanced QFN
package further improves the thermal performance of the
ISL6292B in space-limited applications.
Pinout ISL6292B TOP VIEW
Features
• Complete Charger for Single-Cell Li-ion Batteries
• Integrated Pass Element and Current Sensor
• No External Blocking Diode Required
• Very Low Thermal Dual-Mode Operation
• 1% Voltage Accuracy with Remote Sense
• Programmable Current Limit up to 1.5A
• Programmable End-of-Charge Current
• Programmable Safety Timer
• Drives a Tri-Color LED
• Charge Current Thermal Foldback
• NTC Thermistor Interface for Battery Temperature Monitor
• Two-Level Ambient Temperature Setting
• Guaranteed to Operate at 2.65V After Start-Up
• Ambient Temperature Range: -20°C to 70°C
• Thermally-Enhanced QFN Packages
• 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 (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
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 NUMBER TEMP. RANGE (°C) PKG. DWG. #
ISL6292BCR* -20 to 70 16 Ld 4x4 QFN
ISL6292BCRZ* (Note) -20 to 70 16 Ld 4x4 QFN
(Pb-free)
*Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free 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.
GRN
1
3
4
15
VIN
RED
TIME
VIN
VIN
BAT
BAT
16 14 13
2
12
10
9
11
6578
VSEN
TEMP
IMIN
IREF
GND
V2P9
DT
EN
Datasheet April 19, 2005
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-352-6832 |Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2004, 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
2FN9139 .1
April 19, 2005
Absolute Maximum Ratings Thermal Information
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 7V
Output Pin (BAT, VSEN, RED, GRN, DT) . . . . . . . . . . . -0.3 to 5.5V
Signal Pin (EN, TIME TEMP, IREF, IMIN, V2P9) . . . . . . -0.3 to 3.2V
Charge Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6A
ESD Rating
Human Body Model (Per MIL-STD-883 Method 3015.7) . . .3500V
Machine Model (Per EIAJ ED-4701 Method C-111). . . . . . . .200V
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . .-20°C to 70°C
Supply Voltage, VIN. . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3V to 6.5V
Recommended Charge Current. . . . . . . . . . . . . . . . 400mA to 1.5A
Thermal Resistance (Notes 1, 2) θJA (°C/W) θJC (°C/W)
4x4 QFN Package . . . . . . . . . . . . . . . . 41 4
Maximum Junction Temperature (Plastic Package) . . . . . . . . 150°C
Maximum Storage Temperature Range . . . . . . . . . . . -65°C to 150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300°C
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. θJA 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. θJC, “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 25°C Ambient Temperature, maximum and minimum values are
guaranteed over -10°C to 70°C Ambient Temperature with a supply voltage in the range of 4.3V to 6.5V, unless
otherwise noted.
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
POWER-ON RESET
Rising VIN Threshold 3.0 3.4 4.0 V
Falling VIN Threshold 2.3 2.4 2.7 V
STANDBY CURRENT
VBAT Pin Sink Current ISTANDBY VIN floating or EN pin is floating - - 3.0 µA
VIN Pin Supply Current IVIN BAT Pin floating, EN = LOW - 0.5 - mA
VOLTAGE REGULATION
Output Voltage VCH 4.158 4.20 4.242 V
Dropout Voltage VBAT = 3.7V, ICHARGE = 0.65A - 190 - mV
CHARGE CURRENT
Charge/Protection Current (Note 3) ICHARGE RIREF = 80kΩ, VBAT = 3.7V, VIN = 5V 0.9 1.0 1.1 A
Trickle Charge Current ITRICKLE RIREF = 80kΩ, VBAT = 2.0V, VIN = 5V 85 110 135 mA
End-of-Charge Threshold RIMIN = 133kΩ40 60 80 mA
RECHARGE THRESHOLD
Recharge Voltage Threshold VRECHRG 3.85 4.00 4.13 V
TRICKLE CHARGE THRESHOLD
Trickle Charge Threshold Voltage VMIN 2.7 2.8 3.2 V
BATTERY TEMPERATURE MONITORING
Low Temperature Threshold VTMIN V2P9 = 3.0V 1.44 1.50 1.58 V
Low Temperature Hysteresis (Note 4) - 214 - mV
High Temperature Threshold VTMAX V2P9 = 3.0V 0.35 0.38 0.405 V
High Temperature Hysteresis (Note 4) - 51.4 - mV
DT Pin MOSFET On Resistance RDT - 30 100 Ω
Charge Current Foldback Threshold (Note 4) TFOLD 85 100 115 °C
Current Foldback Gain (Note 4) GFOLD -100-mA/°C
ISL6292B
3FN9139 .1
April 19, 2005
OSCILLATOR
Oscillation Period TOSC CTIME = 15nF 2.4 3.0 3.6 ms
LOGIC INPUT AND OUTPUT
EN Input Low --0.8V
EN Pin External Pull Down to Disable - - 50 kΩ
RED Sink Current Pin Voltage = 0.8V 5 - - mA
GRN Sink Current Pin Voltage = 0.8V 5 - - mA
NOTES:
3. The actual current may be lower due to the thermal foldback.
4. Guaranteed by design, not a tested parameter.
Electrical Specifications Typical values are tested at VIN = 5V and 25°C Ambient Temperature, maximum and minimum values are
guaranteed over -10°C to 70°C Ambient Temperature with a supply voltage in the range of 4.3V to 6.5V, unless
otherwise noted. (Continued)
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
ISL6292B
4FN9139 .1
April 19, 2005
Pin Description
VIN
VIN is the input power source. Connect to a wall adapter.
RED, GRN
RED and GRN are two open-drain outputs to drive a red and
a green LED in the same package. The RED and the GRN
pins are guaranteed to be capable of sinking at least 5mA
current.
TIME
The TIME pin determines the oscillation period by
connecting a timing capacitor between this pin and GND.
The oscillator provides a time reference for the charger.
GND
GND is the connection to system ground.
V2P9
This is a 2.9V untrimmed voltage output. This pin outputs a
2.9V voltage source when the input voltage is above POR
threshold, independent on the EN pin input. The V2P9 pin
can be used as an indication for adapter presence.
EN
EN is the enable logic input. Connect the EN pin to LOW to
enable the charger or leave it floating to disable the charger.
This pin is pulled up to 2.9V when left floating.
IREF
This is the programming input for the constant charging
current in a linear charger. In the typical application of a
dual-mode charger, the IREF pin programs the trickle charge
current as well as the protection current level.
IMIN
IMIN is the programmable input for the end-of-charge
current.
TEMP
TEMP is the input for an external NTC thermistor.
DT
DT is the input to set the temperature difference before and
after the charging starts. This pin can also be used as an
indication whether or not the charger is charging.
VSEN
VSEN is the battery voltage sensing input. This pin allows
remote sense of the battery pack voltage.
BAT
BAT is the charger output.
Typical Application
ISL6292B
VIN
V2P9
TEMP
GND
BAT
Input
C1
To Battery
C3
BAT+
BAT-
ID
R1
R2
RT
C2
DT
RED
GRN
D2D1
EN
TIME
CTI M E
IREF
RIREF
IMIN
RIMIN
VSEN
C4
R3
RS
R4
R5
C1, C3:1µF X5R ceramic capacitor
C2, C4:0.1µF X5R ceramic ca pacitor
CTIME: 22nF X5R or better timing capacitor
D1, D2: dual-color (red and green) LED in one package
R1:41.2kΩ, 1%
R2: TBD, value dependent on the ∆T (2.3kΩ for 20°C)
RT: ECTH-160808-103-J-3800HT, 10kΩ at 25°C, 5%
RS:1.33kΩ, 1%
R3:10kΩ, 5% (R3 and C4 are for improving ESD protection)
RIREF :80kΩ, 1%
RIMIN : 133kΩ, 1% R4, R5:330Ω, 5%
ISL6292B
5FN9139 .1
April 19, 2005
Block Diagram
LOGIC
RED
ISEN
VIN BAT
100000:1
Curre nt
Mirror
COUNTER
+
-
+
-
VMIN
+
-
+
-
VCH
IREF
+
-
IMIN
TEMP
GRN
Recharge
Minbat
Under Temp
VRECHRG
CA
VA
MIN_I
Input_OK
IR
ISEN
IMIN
V2P
8
CHRG
+
-
+
-
Input_OK
VPOR
Trickle/Fast
References V2P9
Temperature
Monitoring
Current
References
IT
NTC
Interface Over Temp
TIME OSC
GND
VIN
VCH
VMIN
VPO R
VR ECHRG
QMAIN
QSEN
RIREF
RIMIN
C1
EN
DT
VSEN
+100mV
-
ISL6292B
6FN9139 .1
April 19, 2005
Flow Chart
TEMP FAULT
Charger: OFF
LED: YELLOW
TRICKLE CHARGE
Charger: ON
LED: RED
FAST CHARGE
Charger: ON
LED: RED
CHARGE TERMINATES
Charger: OFF
LED: GREEN
RECHARGE
Charger: ON
LED: GREEN
TIMEOUT FAULT
Charger: OFF
LED: YELLOW
Anytime POR
and Enable
occurs
VBAT > 2.8V before 1/8 TIMEOUT
completes
VBAT > VRECHRG and ICHG < IMIN
and
TIMEOUT not completed
VBAT < VRECHRG
TIMEOUT completes
TEMP fault removed
VBAT < 2.8V when 1/8 TIMEOUT
completes
CHARGE COMPLETES BUT NOT
TERMINATES
Charger: ON
LED: GREEN
TIMEOUT
completes
TIMEOUT
completes and
VBAT > VRECHRG
TEMP fault
TEMP fault
TEMP FAULT
Charger: OFF
LED: YELLOW
TEMP fault
TEMP fault
removed
TEMP FAULT
Charger: OFF
LED: YELLOW
TEMP fault
removed
TEMP fault
TEMP fault
CHARGE TERMINATES
Charger: OFF
LED: GREEN
TIMEOUT
completes and
VBAT < VRECHRG
ISL6292B
7FN9139 .1
April 19, 2005
Theory of Operation
The ISL6292B is based on the Intersil Patent-pending
dual-mode charging technology. The dual-mode technology
generates very low heat, which enables the charger to be
used in space-limited applications.
To take advantage of the low-heat feature, a current-limited
ac/dc converter is required as the power supply to the
charger. The current-limited supply has the I-V
characteristics shown in Figure 1. The supply is a dc source
before the load current reaches the limited current ILIM.
Once the current limit is reached, the supply current cannot
increase further; instead, the supply voltage falls. The
current-limited supply is equivalent to a voltage source with
an equivalent output impedance or a current source,
depending on the region it operates at, as shown in Figure 1.
The ISL6292B charges a battery with the traditional constant
current/constant voltage (CC/CV) profile. The constant
current is determined by the current limit ILIM of the supply
during the constant-current charge mode. To ensure dual-
mode operation, the current protection level set by the IREF
pin should be higher than ILIM. In the constant-voltage
charge mode, the battery voltage is regulated at 4.2V. When
the battery voltage is below the VMIN given in the Electrical
Specification, the charger preconditions the battery using
trickle charge mode. The trickle-charge current is 10% of the
protection current level programmed by the IREF pin.
Figure 2 shows the typical waveforms in a charge cycle of
the dual mode operation. When the battery is below VMIN,
the charge current is 10% of IREF set by the IREF pin. Since
the charge current is much less than the ILIM, the ac/dc
converter operates in the voltage source region. Once the
battery voltage exceeds VMIN, the charger starts to fully turn
on the internal P-channel power MOSFET. The ac/dc
converter operates in the current-limited region and its
voltage is pulled down to a level slightly higher than the
battery voltage. As shown in Figure 2, the charge current is
ILIM and is lower than IREF
. As the battery voltage reaches
the 4.2V VCH, the charge current starts to decrease. The
ac/dc supply moves out of the current-limit region and
becomes a voltage source again. When the charge current
reaches a programmable end-of-charge (EOC) level set by
the IMIN pin, the charger sends out an EOC indication. The
real termination of the charger happens at the end of a total
charge time set by the TIME pin.
The power dissipation is also shown in Figure 2. The power
dissipation in both the trickle mode and the constant-current
(CC) mode are very low. The possible peak power occurs at
the transition from the CC mode to the constant-voltage (CV)
mode. This peak power is much lower than the peak power
normally seen in a linear charger and can be further reduced
by properly designing the ac/dc converter. One simple
approach is to design the ac/dc converter output voltage just
high enough to fully charge the battery (normally lower than
5V). More information can be found in the ISL6292
datasheet available at http://www.intersil.com. To ensure the
thermal safety, the ISL6292B has an internal thermal fold-
back function that automatically reduces the charge current
if the internal temperature typically rises above 100°C.
The ISL6292B offers many other features. The trickle
current, the CC charge current, and the end-of-charge
(EOC) current are all programmable. A thermal foldback
function monitors the internal temperature and reduces the
charge current when the internal temperature rises above
100°C to prevent further temperature rise. A safety timer
sets the charge time limit for both trickle mode and fast mode
charge. When the battery voltage drops after the charge
cycle terminates, the charger automatically starts recharging
the battery to full. Two indication pins are designed to drive a
tri-color LED (a red and a green LED in the same package).
A simple thermistor circuit interface allows the user to set a
different level of ambient temperature before and after the
charger starts. All these features are described in detail in
the Application Information section.
FIGURE 1. THE I-V CHARACTERISTICS OF THE CURRENT-
LIMITED AC/DC CONVERTER.
VNL
VFL
ILIM
rO
VNL I LIM
rO =(VNL - VFL )/I
LIM
A
B
C
FIGURE 2. TYPICAL CHARGE CURVES USING A CURRENT-
LIMITED ADAPTER.
VCH
VMIN
VIN
IREF
IREF/10
P1
P2
ILIM
Trickle
Mode
Constant
Current Mode
Constant
Voltage Mode
Inhibit
TIMEOUT
Input Voltage
Battery Voltage
Charge Current
Power Dissipation
ISL6292B
8FN9139 .1
April 19, 2005
Applications Information
Power-On Reset (POR)
The ISL6292B has a 3.4V rising POR threshold. Before the
input voltage reaches the POR threshold, the 2.9V V2P9 pin
outputs 0V and the charger is disabled. Once the POR
threshold is reached, the V2P9 pin outputs 2.9V, the open-
drain MOSFET on the DT pin is turned on, and the ambient
temperature monitoring circuit starts to function. After a
delay and after the input voltage rises above the battery
voltage, the charger control circuit starts to work and the DT
pin impedance becomes high. Figure 3 shows the sequence
of the events at power on. The POR has a falling threshold
of 2.4V typically. At power on, all counters are reset to zero.
Charge Current and RIREF Selection
When the ISL6292B is used as a traditional linear charger,
the RIREF sets the constant charge current. The trickle
charge current is 10% of the CC current IREF. When working
with a current-limited supply, the CC current is determined
by the supply limited current ILIM. IREF needs to be
programmed higher than ILIM and is used as an overcurrent
protection. Taking into account the tolerance of both the ILIM
and IREF
, it is recommended the IREF be programmed at
least 30% higher than the ILIM. IREF can be found by the
following equation:
(EQ. 1)
The trickle charge current is 10% of IREF, that is,
(EQ. 2)
The ISL6292B has a comparator with 100mV offset voltage
to ensure the input voltage is higher than the battery voltage
before charging starts (see the Block Diagram). This
condition requires ILIM be higher than 400mA. The upper
limit for ILIM is 1.5A.
EOC Current and RIMIN Selection
The EOC current is programmed by the IMIN pin and can be
calculated by the following equation:
(EQ. 3)
The EOC current has a programming range up to 400mA.
To qualify as an EOC condition, the charge current needs to
drop below the IMIN level and stay below the IMIN level for
more than three to four cycles of the internal oscillator;
additionally, the battery voltage rises above the recharge
threshold given in the Electrical Specification table.
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 10µA current.
The period TOSC is:
(EQ. 4)
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 and CTIME Selection
The total charge time for the CC mode and CV mode is
limited to a length of TIMEOUT, which can be found by:
(EQ. 5)
FIGURE 3. EVENT SEQUENCE AT POWER UP
VIN
V2P9
DT
Imped
Charger
Start
POR
IREF
0.8V
RIREF
----------------- 105
×A()
=
ITrickle
0.8V
RIREF
----------------- 104
×A()
=
IMIN
0.8V
RIMIN
---------------- 104
×A()
=
TOSC 0.2 106CTIME
⋅⋅=ondssec()
FIGURE 4. OPERATION WAVEFORMS
VIN
V2P9
RED
GRN
VBAT
ICHG
15 Cycles to
1/8 TIM EOUT
15
Cycles
POR
Threshold
t0t1t2t3t4t5t6t7t8
Charge
Cycle
Charge
Cycle
IMIN
DT
Imped.
MINMINMIN
RECHRG
V
2.8V VMIN
TIMEOUT 14
CTIME
1nF
------------------
⋅=minutes()
ISL6292B
9FN9139 .1
April 19, 2005
CTIME is the timing capacitor shown in the Typical
Application circuit. A 1nF capacitor leads to 14 minutes of
TIMEOUT. For example, a 15nF capacitor sets the
TIMEOUT to be 3.5 hours. The charger is terminated when
the TIMEOUT is reached.
The trickle mode charge has a time limit of 1/8 TIMEOUT. If
the battery voltage does not reach VMIN within that 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.
Recharge Threshold
The charger terminates when the TIMEOUT limit expires.
After the termination, if the battery is below the recharge
threshold given in the Electrical Specification table, the
charger starts a re-charge cycle.
LED Indications
RED and GRN are two open-drain outputs that directly drive
a tri-color LED. At the moment when the power is applied or
when the charger is enabled through the EN pin, the charger
starts to charge and the RED indication pin outputs a low
impedance to drive a red LED. Once the charge finishes
(either when the EOC condition is qualified or when the
TIMEOUT completes), the GRN pin turns on to drive a green
LED and the red LED is off. The green LED remains on
unless the input power is recycled, or when the EN pin is
toggled, or a fault case happens. When a recharge occurs,
the indication remains in green.
When a fault case happens, both the RED and the GRN pins
are on to indicate a yellow color. If the FAULT is a TIMEOUT
fault, the yellow indication is latched and can only be reset
through the EN pin or the input power. If the FAULT is an
ambient temperature FAULT, the charger restarts after the
fault condition is removed. When not powered or when not
enabled, both LEDs are off. Table 1 summarizes the LED
indications.
VSEN Pin
The VSEN pin allows remote sensing of the battery voltage
to minimize the resistive voltage drop between the charger
output and the battery positive terminal. Figure 5 shows the
internal voltage feedback circuit. In applications that the
remote sense pin goes through a connector, a local low-
value resistor is recommended, as the R1 shown in Figure 5,
in case the connector has bad contact. The sum of R2 and
R3 is 75kΩ, therefore, a 10Ω R1 is negligible in output
voltage accuracy.
Ambient Temperature Sensing
The TEMP pin is used to set the ambient temperature range
that allows charging the battery. Typically, an NTC (negative
temperature coefficient) resistor is mounted on the printed
circuit board (PCB) to monitor the ambient temperature. Due
to the self-heating of the PCB during charging, the ISL6292B
provides the DT pin to set a higher temperature threshold
after the charger starts.
Figure 6 shows the internal circuit for the ambient
temperature sensing function. The two comparators form a
window comparator whose high-threshold is VTMIN and low-
threshold is VTMAX. These two thresholds are given in the
Electrical Specifications. The two MOSFETs (Q1 and Q2)
FIGURE 5. THE INTERNAL VOLTAGE FEEDBACK CIRCUIT
+
-
BAT
VSEN
R2
Q1
R3
VA
Enable
VREF
R1
10Ω
TABLE 1. LED INDICATION SUMMARY
STATUS RED GRN INDICATION
Charging L H Red
Full Charge (EOC), or recharging H L Green
Trickle TIMEOUT Error L L Yellow (Latched)
Over/Under Ambient Temperature L L Yellow
No Battery H H Off
FIGURE 6. THE INTERNAL AND EXTERNAL CIRCUIT FOR
THE NTC INTERFACE
+
-
+
-
V2P9
TEMP
DT
2.9V
R1
100K
R2
75K
R3
25K
R4
4K
Q1
Q2
CP1
CP2
Under
Temp
Over
Temp
RU
To TEMP Pin
VTM I N
VTM AX
RT
Q3
RD
GND
CHG
ISL6292B
10 FN9139 .1
April 19, 2005
create a hysteresis for each comparator respectively. The
DT pin is shorted to GND via the internal Q3 MOSFET when
the charger is not charging, resulting in the equivalent circuit
shown in Figure 7 (A). The on-resistance of Q3 is typically
50Ω and is negligible compared to the external resistors.
When the charger starts to charge, Q3 is turned off to set a
higher temperature range determined by the external
resistor RD. The equivalent circuit is shown in Figure 7 (B).
The DT pin allows the user to set up a higher shut down
ambient temperature after the charger starts up.
The selection of RU and RT uses the same procedure
described in the ISL6292 datasheet. The selection RD
follows the following equation:
RD = RT, @ 45 °C - RT,@ (4 5°C + ∆T)
where RT,@ 45 °C is the thermistor resistance at 45°C and the
RT,@ (45 °C + ∆T) is the resistance at 45°C + ∆T. Figure 8
shows the temperature windows before, during, and after
charging. Before and after charging, the temperature window
is -5°C to 45°C with 5°C hysteresis. During charging, the
high temperature limit changes to 45°C + ∆T. If this limit is
exceeded, the charger is stopped and the temperature has
to come back to below 40°C for the charging to be allowed
again. The low temperature limit is also increased. However,
the RD typically has a much lower resistance than the NTC
at low temperature, therefore, the influence on the
temperature threshold is not as much as at high
temperature. Typically, the low temperature threshold is
raised by less than 2°C, as shown in Figure 8.
Charge Current Thermal Foldback
The thermal foldback function monitors the die temperature
and reduces the charge current when the die temperature
rises above 100°C to prevent further temperature rise. The
charge current reduces at a rate of 100mA/°C after
exceeding 100°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 110°C. The actual charge
current settles between 100°C to 110°C.
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-of-
charge unless the battery voltage is already above the
recharge threshold.
2.9V Bias Voltage
The ISL6292B provides a 2.9V 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.
EN Pin
The EN pin allows direct interface to the battery ID pin of a
battery pack. The battery ID pin is connected with a resistor
of a value less than 27kΩ to ground inside the battery pack.
When the battery is not attached, the EN pin is pulled up by
an internal source to the V2P9 pin to disable the charger.
The 2.9V internal regulator is on as long as the input power
is applied, independent of the EN input. Table 2 summarizes
the status of each pin when the IC is disabled.
FIGURE 7. EQUIVALENT CIRCUITS FOR THE NTC DIVIDER
(A) BEFORE CHARGING STARTS
(B) DURING CHARGING.
V2P9
TEMP
DT
RU
RT
RQ3
GND
V2P9
TEMP
RU
RT
RD
GND
(A) (B)
TABLE 2. SUMMARY OF PIN BEHAVIOR WHEN THE IC IS
DISABLED BY THE EN PIN
PIN BEHAVIOR
V2P9 Outputs 2.9V.
RED High impedance
GRN High impedance
DT Low impedance
IREF Outputs 0.8V
IMIN Outputs 0.8V
TEMP The temperature monitoring circuit remains functioning.
FIGURE 8. BOARD TEMPERATURE MONITORING WHEN
THE CHARGE IS NOT CHARGING, THE
TEMPERATURE WINDOW IS -5°C AND 45°C.
ONCE THE CHARGER STARTS, THE
TEMPERATURE WINDOW IS 1.X°C TO 45°C+ ∆T.
0oC
45oC
45oC + ∆T
-5oC
40oC
Less than 2°C
CHARGENOT CHARGE NOT CHARGE
ISL6292B
11 FN9139 .1
April 19, 2005
Board Layout Recommendations
The ISL6292B is targeted for space-limited applications. 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 pads for the 4x4
QFN package are able to have 5 vias. As much copper as
possible should be connected to the exposed pad to
minimize the thermal impedance. Refer to the ISL6292B
evaluation board for layout examples.
ISL6292B
12
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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
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FN9139 .1
April 19, 2005
ISL6292B
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)
SYMBOL
MILLIMETERS
NOTESMIN NOMINAL MAX
A 0.80 0.90 1.00 -
A1 - - 0.05 -
A2 - - 1.00 9
A3 0.20 REF 9
b 0.23 0.28 0.35 5, 8
D 4.00 BSC -
D1 3.75 BSC 9
D2 1.95 2.10 2.25 7, 8
E 4.00 BSC -
E1 3.75 BSC 9
E2 1.95 2.10 2.25 7, 8
e 0.65 BSC -
k0.25 - - -
L 0.50 0.60 0.75 8
L1 - - 0.15 10
N162
Nd 4 3
Ne 4 3
P- -0.609
θ--129
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 & θ 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 ba ck (L1) maybe present. L
minus L1 to be equal to or greater than 0.3mm.
