Intersil ISL6297 Li-ion/li polymer battery charger Datasheet

ISL6297
®
Data Sheet
March 20, 2007
FN9215.1
Li-ion/Li Polymer Battery Charger
Features
The ISL6297 is a Dual-Mode Lithium Ion battery charger
optimized for cellular phone travel charger applications. It
uses Intersil’s patent-pending dual-mode charge
technology to minimize the heat normally generated in a
linear charger. By minimizing the heat generation, the
ISL6297 can be placed inside the connector of the travel
charger to completely remove the influence of the adapter
cable on the charging performance.
• Complete Charger for Single-Cell Li-ion Batteries
The ISL6297 is an enhancement of the original ISL6292B.
New features include improved accuracy, pre-charge circuit
verification, and enhanced LED indicator function.
• Integrated Pass Element and Current Sensor
• No External Blocking Diode Required
• Very Low Thermal Dual-Mode Operation
• 0.7% Voltage Accuracy with Remote Sense
• Pre-charge circuit verification with LED status indication
• Drives a bi-color LED
• Programmable Safety Timer
• Programmable Current Limit up to 1.5A
Working with a current-limited AC/DC converter, the dualmode 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 bi-color LED. A safety timer prevents
charging a dead battery for an excessively long period.
• Programmable End-of-Charge Current
The ISL6297 also features THERMAGUARD™, 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, for charge and non-charge
conditions. The thermally-enhanced QFN package further
improves the thermal performance of the ISL6297 in spacelimited applications.
• 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
• THERMAGUARD™ 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
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• PDAs, Cell Phones and Smart Phones
• Portable Instruments, MP3 Players
• Medical Handhelds
Pinout
• Self-Charging Battery Packs
16
14
15
• Stand-Alone Chargers
Ordering Information
BAT
BAT
VIN
VIN
ISL6297
(16 LD QFN)
TOP VIEW
PART
NUMBER
13
PART
TEMP.
MARKING RANGE (°C)
PACKAGE
PKG.
DWG. #
ISL6297CR*
ISL 6297CR
-20 to +70
16 Ld 4x4 QFN L16.4x4
ISL6297CRZ*
(Note)
62 97CRZ
-20 to +70
11 TEMP
16 Ld 4x4 QFN L16.4x4
(Pb-free)
3
10 IMIN
Add “-T” suffix for tape and reel.
4
9
2
RED
TIME
5
6
1
7
8
V2P9
GRN
EN
12 VSEN
DT
1
GND
VIN
IREF
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.
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.
Thermaguard is a trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2005-2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
ISL6297
Absolute Maximum Ratings
Thermal Information
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 7V
All Other Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 5.5V
Thermal Resistance (Notes 1, 2)
θJA (°C/W)
θJC (°C/W)
4x4 QFN Package . . . . . . . . . . . . . . . .
41
4
Junction Temperature Range . . . . . . . . . . . . . . . . .-55°C to +150°C
Operating Temperature Range . . . . . . . . . . . . . . . . .-40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . . . . . . .-65°C to +150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . +300°C
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . .-20°C to +70°C
Supply Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3V to 6.5V
Maximum Pin Voltage (Except VIN). . . . . . . . . . . . . . . . . . . . . 5.25V
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.
+150°C max junction temperature is intended for short periods of time. Constantly operated at +150°C may shorten the life of the part.
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 recommended operating conditions, unless otherwise noted.
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Rising VIN Threshold
2.9
3.4
4.0
V
Falling VIN Threshold
2.3
2.4
2.65
V
-
2.9
-
V
-
-
30
mA
30
-
-
mV
VIN floating or EN pin is floating
-
-
3.0
μA
POWER-ON RESET, OVER VOLTAGE PROTECTION, PRE-REGULATOR
2.9V Reference Output Voltage
V2P9
ILOAD = 2mA
2.9V Reference Output Current
VIN-BAT Comparator Offset
STANDBY CURRENT
VBAT Pin Sink Current
ISTANDBY
VIN Pin Supply Current
IVIN1
BAT Pin floating, EN = LOW
-
1.0
1.5
mA
VIN Pin Supply Current
IVIN2
BAT Pin floating, EN = HIGH
-
0.5
1.0
mA
VIN = 4.3V, VSEN = BAT= 4.5V, EN = HIGH
-
-
6.0
μA
4.17
4.20
4.23
V
-
250
300
mV
Charger Reverse Current
VOLTAGE REGULATION
Output Voltage
VCH
Dropout Voltage
VBAT = 3.7V, ICHARGE = 0.65A
CHARGE CURRENT
Charge/Protection Current
ICHARGE
RIREF = 80kΩ, VBAT = 3.7V, VIN = 5V
900
1000
1100
mA
Trickle Charge Current
ITRICKLE
RIREF = 80kΩ, VBAT = 2.0V, VIN = 5V
85
110
135
mA
RIMIN = 133kΩ
56
63
70
mA
End-of-Charge Current
CHARGE VOLTAGE THRESHOLDS
Short-Circuit Threshold
VSC
0.9
1.0
1.1
V
Trickle Charge Threshold - Rising
VMIN
2.7
2.9
3.2
V
Trickle Charge Threshold - Falling
Recharge Threshold - Falling
VMIN
2.6
2.7
3.0
V
VRECHRG
3.90
4.00
4.08
V
-
-210
-
mV
-
4.4
-
V
Difference from Final Battery Voltage
Open Circuit Test Threshold- Rising
2
VOCR
FN9215.1
March 20, 2007
ISL6297
Electrical Specifications
Typical values are tested at VIN = 5V and +25°C ambient temperature. Maximum and minimum values are
guaranteed over recommended operating conditions, unless otherwise noted. (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
1.94
2.0
2.06
V
135
167
199
mV
.704
.718
.732
V
160
185
200
mV
BATTERY TEMPERATURE MONITORING
Low Temperature Threshold
VTMIN
V2P9 = 2.88V
Low Temperature Hysteresis
High Temperature Threshold
VTMAX
V2P9 = 2.88V
High Temperature Hysteresis
RDT
-
25
-
Ω
Charge Current Foldback Threshold (Note 4)
TFOLD
-
100
-
°C
Current Foldback Gain (Note 5)
GFOLD
-
100
-
mA/°C
2.7
3.0
3.3
ms
EN Input Low
-
-
0.8
V
EN Pin External Pull Down to Disable
-
-
50
kΩ
5
10
-
mA
-
-
1
μA
DT Pin MOSFET On Resistance
OSCILLATOR
Oscillation Period
TOSC
CTIME = 15nF
LOGIC INPUT AND OUTPUT
LED Sink Current (RED, GRN)
Pin Voltage = 1.0V
LED Leakage Current
NOTES:
3. The actual current may be lower due to the thermal foldback.
4. Guaranteed by design and characterization to be typically +100°C ±15%.
5. Guaranteed by design and characterization.
3
FN9215.1
March 20, 2007
ISL6297
Pin Description
PIN #
PIN NAME
DESCRIPTION
1, 15, 16
VIN
VIN is the input power source. It is recommended to have a 1Ω resistor in series with the input decoupling capacitor to
prevent an over-shoot voltage when the input cable is plugged in.
2
GRN
Open-drain LED drive pin. This pin sinks a constant-current 10mA to drive a green LED in a bi-color LED pack.
3
RED
Open-drain LED drive pin. This pin sinks a constant-current 10mA to drive a red LED in a bi-color LED pack.
4
TIME
Timer Programming Input. 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.
5
GND
GND is the connection to system ground.
6
DT
Delta Temperature Setting Input. This pin sets 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.
7
EN
Enable Input. Connect EN LOW to enable the charger. Pull it HIGH or leave it floating to disable the charger. This pin is
pulled up to 2.9V when left floating.
8
V2P9
Untrimmed 2.9V 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 output is used to power the LEDs, the NTC circuit, or for other functions. The
maximum output current is 30mA. This output can also be used as an indication for adapter presence.
9
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.
10
IMIN
IMIN is the programmable input for the end-of-charge current.
11
TEMP
Temperature setting input. An external NTC thermistor is connected to this pin for ambient temperature sensing.
12
VSEN
Battery remote voltage sensing feedback pin. This pin allows remote sense of the battery pack voltage. Connect this pin
as close as possible to the battery positive terminal with a separate trace to minimize the impact of parasitic resistance.
This pin also serves the function of compensating for voltage drop caused by the connector contact resistance.
13, 14
BAT
-
EPAD
BAT is the charger output.
Exposed Pad. This pad is internally connected to GND. Connect as much copper as possible to this pad on the component
or other layers through thermal vias to maximize the thermal performance.
Typical Application
Input
Input
RIN
To Battery
BAT
VIN
C1
BAT+
C3
BAT-
C1
V2P9
R1
C2
R3
TEMP
D1
RS
R2
DT
EN
CTIME
TIME
RIREF
RED
GRN
GND
C1: 1μF X5R ceramic capacitor
C3: 10μF X5R ceramic capacitor
C2, C4: 0.1μF X5R ceramic capacitor
CTIME : 22nF X5R or better timing capacitor
D1, D2: dual-color (red and green) LED in one package
RIREF : 80kΩ, 1%
RIMIN : 133kΩ, 1%
4
ID
C4
ISL6297
RT
D2
VSEN
IREF
NOTE: Temperature limit
components selected for a
temperature Range of -5°C
to +45°C (not charging)
See Example, page 14
RIMIN
IMIN
R1: 15kΩ, 1%
R2: TBD, value dependent on the DT (1.37kΩ for +10°C delta)
RT: MuRata NCP18XH103J -- 10kΩ at +25°C, 5% (0603 size)
RS: 41.2Ω
R3: 10kΩ, 5% (R3 and C4 are for improving ESD protection)
RIN: 1Ω (Used to prevent overshoot when connecting the cable)
FN9215.1
March 20, 2007
ISL6297
Block Diagram
Q MAIN
VIN
BAT
R
C1IN
+
CA
-
VSEN
VPOR
+
+
50mV
CHRG
Current
References
IMIN
-
-
RIREF
VIN
+
Input_OK
IR
VCONVER
ISEN
VRECHRG
VCH
VPOR
100000:1
Current
Mirror
VMIN
QSEN
IT
IREF
V2P9
References
Temperature
Monitoring
C1
V+
A-
IMIN
VCH
RIMIN
+
Trickle/Fast
ISEN
-
Minbat
VMIN
+
-
+
MIN_I
VRECHRG
Recharge
V2P9
LOGIC
+
Under Temp
TEMP
NTC
Interface
DT
OSC
TIME
-
VCONVER
Batcon
Over Temp
RED
GRN
COUNTER
GND
Input_OK
EN
5
FN9215.1
March 20, 2007
ISL6297
State Diagram
Plug-in Indicator
LED:
POR
RED
GREEN
YELLOW
OFF
CHARGER: OFF
500ms
500ms
500ms
Idle
LED:
CHARGER:
DISABLE
OFF
OFF
ENABLE
DISABLE or
POR
Delay 500ms
LED:
CHARGER:
OFF
OFF
Open Battery Fault
LED:
CHARGER:
Connection Verify (70ms)
LED:
OUTPUT:
CHARGER:
Temp Fault
Cleared
(Return to previous state)
Battery (+)
Terminal
Disconnected
OFF
Up to VIN
TRICKLE
OFF
OFF
DISABLE or
POR
Battery (+) Terminal Connected
Short Circuit Test
Temperature Fault
LED:
CHARGER:
TIMEOUT:
LED:
YELLOW
CHARGER: OFF
RED
TRICKLE
RESTART
Non-Temperature Fault
LED:
YELLOW (Blink)
CHARGER: OFF
VSEN <1V
after 384
cycles
VSEN > 1V
before 384 cycles
Any Temp
Fault
VSEN < 2.8V after
1/8 TIMEOUT
Trickle Charge
LED:
CHARGER:
RED
TRICKLE
VSEN > 2.8V
before 1/8 TIMEOUT
Recharge
LED:
CHARGER:
Charge Termination
Fast Charge
GREEN
ON
TIMEOUT and
VSEN > 3.7V
ICHG > IMIN
LED:
CHARGER:
TIMEOUT and
VSEN < 3.7V
ICHG > IMIN
LED:
CHARGER:
VSEN > 4.05V and
ICHG < IMIN
before TIMEOUT
VSEN > 4.05V and
ICHG < IMIN
Timer Restart
RED
ON
GREEN
OFF
DISABLE or
POR
End of Charge
LED:
GREEN
CHARGER: ON
TIMEOUT: RESTART
LED:
CHARGER:
GREEN
ON
TIMEOUT
VSEN < 4.00V
Charge Complete
LED:
CHARGER:
6
GREEN
OFF
Note:
In the “Connection Verify” state, the output current
is limited to ITRICKLE. In this state, with a battery
connected, the output voltage rises no higher than
the battery voltage. Also in this state, with no
battery connected, the output voltage rises to VIN.
In all other states, the output voltage is limited to
4.2V (typ).
FN9215.1
March 20, 2007
ISL6297
Theory of Operation
The ISL6297 is based on the Intersil Patent-pending dualmode charging technology. This allows the ISL6297 to
function as a traditional linear charger when powered with a
voltage-source adapter. However, when powered with a
current-limited adapter, the charger minimizes the thermal
dissipation commonly seen in traditional linear chargers.
This dual-mode technology generates very low heat, which
enables the charger to be used in space-limited applications.
The ISL6297 charges a Lithium Ion battery using the
constant current (CC) and constant voltage (CV) profile
specified by battery cell manufacturers.
As a linear charger, the constant charge current IREF is
programmable up to 1.5A with an external resistor. The
constant charge voltage VCH is regulated by the ISL6297 at
4.2V with a 0.7% accuracy over the entire recommended
operating range.
The ISL6297 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.
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 +100°C to prevent further temperature rise. The
thermal-foldback feature guarantees safe operation when
the printed circuit board (PCB) is space limited for thermal
dissipation.
Trickle
Mode
VIN
VCH
Constant Current
Mode
Constant Voltage
Mode
Figure 1 shows the typical charge curves in a traditional
linear charger powered with a constant-voltage adapter. The
power dissipation PCH is given by the following equations:
P CH = ( V IN -V BAT ) × I CHARGE
(EQ. 1)
where ICHARGE is the charge current. The maximum power
dissipation occurs at 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 1 shows, with dotted lines, two cases in
which the charge currents are limited by the maximum power
dissipation capability due to the thermal foldback.
To take advantage of the low-heat feature of the ISL6297, 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 2. 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 a voltage source with an equivalent
output impedance or a current source, depending on its
operating region, as shown in Figure 2.
VNL
C
rO = (VNL - VFL)/ILIM
VFL
B
rO
VNL
I LIM
Inhibit
Input Voltage
A
ILIM
Battery Voltage
FIGURE 2. THE I-V CHARACTERISTICS OF THE CURRENTLIMITED AC/DC CONVERTER
VMIN
IREF
Charge Current
IREF/10
P1
P2
P3
Power Dissipation
TIMEOUT
FIGURE 1. TYPICAL CHARGE CURVES USING A
CONSTANT-VOLTAGE ADAPTER
7
In this mode of operation, the constant current is determined
by the current limit ILIM of the supply during the constantcurrent charge mode. To ensure dual-mode operation, the
current protection level set by the ISL6297 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 specified VMIN voltage, the charger
preconditions the battery using trickle charge mode.
Figure 3 shows the typical waveforms in a charge cycle of the
dual mode operation. When the battery voltage is below VMIN,
the trickle charge mode is in effect. 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 fully turns on the internal P-channel power
MOSFET. The AC/DC converter operates in the currentlimitedregion and its voltage is pulled down to a level slightly
higher than the battery voltage.
FN9215.1
March 20, 2007
ISL6297
Trickle
Mode
VIN
VCH
Constant
Current Mode
Constant
Voltage Mode
Inhibit
Input Voltage
just high enough (normally lower than 5V) to fully charge the
battery. More information can be found in the ISL6292
datasheet available at http://www.intersil.com.
Functional Overview
Battery Voltage
After applying power to the ISL6297, but before charging
starts, the ISL6297 gives a “Plug-in indication” by
sequencially turning on a red, a green and a yellow indicator.
The indicator then turns off. This verifies that the AC/DC
adapter and the ISL6297 have properly powered up.
VMIN
IREF
ILIM
Charge Current
The ISL6297 then waits in an idle mode until the enable pin
indicates that the battery pack has been plugged in. A
500ms delay give time for the pins to be connected prior to
the start of a connection verification operation.
IREF/10
P1
P2
Power Dissipation
TIMEOUT
FIGURE 3. TYPICAL CHARGE CURVES USING A CURRENTLIMITED ADAPTER
As shown in Figure 3, the charge current is ILIM and is lower
than IREF. As the battery voltage reaches the 4.2V VCH
level, 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.
.
When using a current-limited adapter, the thermal situation
in the ISL6297 is totally different from the voltage limited
case. Figure 3 shows the typical charge curves when a
current-limited adapter is employed. The operation requires
that the IREF level be programmed higher than the limited
current ILIM of the adapter. The key difference in the charger
operation under such conditions occurs during the CC mode.
The power dissipation in the CC mode becomes:
P CH = R DS ( ON ) × I CHARGE
2
(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.
When using a current-limited adapter, the worst power
dissipation typically occurs at the beginning of the CV mode,
as shown in Figure 3. The equation EQ.1 also applies to the
dual mode operation 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 ISL6297. One simple
approach is to design the AC/DC converter output voltage
8
In the connection verification, the ISL6297 determines if the
battery positive pin is connected. If not, the charge operation
does not start and the LED remains off.
If the battery is firmly connected, the ISL6297 checks to see
if the battery is good and that the battery connection is not
short-circuited. If no faults are detected the ISL6297 starts a
trickle charge and turns on the red LED charge indicator.
Once the battery voltage reaches VMIN, the charger outputs
a constant current until the battery voltage reaches VCH. The
ISL6297 then holds the voltage constant. As the battery
charges, the current supplied to the battery decreases.
When the charge current drops to IMIN, the ISL6297 issues
an EOC indication, which consists of the LED changing
colors from red to green. An end of charge indication will
also occur at the end of a user programmable TIMEOUT
period even if the cell is not completely charged.
If the battery voltage drops to a recharge threshold after the
end of charge, the ISL6297 recharges the battery until the
voltage again reaches 4.2V and the current drops below
IMIN. At this point, the charger again turns off. The recharge
cycle continues indefinitely until the charger is turned off by
disconnecting the battery, which sets the EN pin high.
An external NTC thermistor allows the ISL6297 to monitor
the ambient temperature. If the ambient temperature is out
range, the charger will not operate. Because the printedcircuit board (PCB) temperature rises during charge, the
ISL6297 provides a higher temperature limit during the
charge operation.
The ISL6297 also features a thermal-foldback function that
reduces the charge current if the IC internal temperature
reaches +100°C to prevent further temperature rise.
Applications Information
Power-On Reset (POR)
The ISL6297 has a 3.4V rising POR threshold. Before the
input voltage reaches the POR threshold, the V2P9 pin
outputs 0V and the charger is disabled. Once the POR
FN9215.1
March 20, 2007
ISL6297
threshold is reached, all counters are reset to zero, the
charge state machine is reset, 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.
ISL6297 terminates the charge operation, turns off the
output voltage, and sets the LEDs off. The device remains in
this state until the EN pin is toggled or the device goes
through a power cycle. (See Figure 5.)
EN Pin
If the battery is connected within the 70ms open battery
detect period, the voltage on VSEN pin needs to drop below
the (falling) threshold of about 4.3V before the end of the
70ms period. If not, then the battery has not been properly
connected and an open battery connection fault condition
exists, requiring a power cycle or a toggle of EN.
If all other charge conditions are met, pulling the EN pin low
starts the ISL6297 charge operation. In a typical application,
EN connects to the ID pin of a battery pack. Inside the
battery pack the ID pin connects to ground through a
resistance of less than 27kΩ. When the battery is not
attached to the charger, the ISL6297 internally pulls the EN
pin high to disable the charger. An RC filter on the ISL6297
EN input improves the charger ESD protection.
Table 1 summarizes the status of each pin when the EN pin
disables the IC.
TABLE 1. 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.
After the 500ms delay, if a battery is connected, the VSEN
voltage will remain below the 4.4V threshold and the
ISL6297 assumes that the battery is connected. The device
turns on the Red LED to indicate a charge operation and
starts a short circuit detection. (See Figure 4.)
If the battery positive terminal comes loose and reconnects
after this time, the charge operation sequence continues, but
the LED indicates an end of charge condition, regardless of
the state of charge.
Short Circuit Detection
To detect a short circuit condition the ISL6297 forces the
trickle charge current to the battery. If, after 384 cycles, the
battery voltage is below 1V, the ISL6297 considers the
battery or connection to be short-circuited. In this condition,
the charger turns off and a flashing yellow indicator displays
the occurance of this “non-temperture” fault.
Plug-in Indication
After power is applied to the ISL6297 and VIN exceeds the
POR threshold, the LEDs provide a Plug-in Indication
sequence. First the RED LED turns on for 500ms, then the
GREEN LED turns on for 500ms, then both turn on for
500ms (giving a YELLOW indication), and finally all the
LEDs turn off.
The ISL6297 turns on an LED by pulling the output line LOW
with a constant current of 10mA (typical). A typical bi-color
LED needs no series resistor for the LED connection,
however, current can be minimized by adding a serial
resistor in each LED path.
To clear a short circuit fault condition requires that the enable
pin be toggled, by removing the battery pack, or by cycling
the power on the charger.
Trickle Charge
If there is no short circuit the voltage is higher than 1V and
the charge operation continues with a trickle charge. In the
trickle charge, the ISL6297 applies 10% of the programmed
current to the battery. If the voltage on the cell is greater than
2.8V after 15 clock cycles, then the ISL6297 applies the full
constant current charge to the cell. However, if the voltage
on the cell does not rise above 2.8V in one eighth (1/8) of the
TIMEOUT period, then a non-temperature fault occurs and
the charger is turned off. A flashing yellow indicator
announces this condition.
Idle Condition and Battery Connection
Once VIN is greater than (VBAT + 50mV) and the
temperature is within the allowed range the ISL6297 is ready
to start the charge operation. Charging is initiated by
plugging in the battery, which pulls the EN pin low.
Connection Verification
The EN pin going low starts a 500ms delay. After the delay,
the ISL6297 turns on the charger for 70ms with a trickle
charge current and an output voltage of VIN. If no battery is
connected, the VSEN voltage will go up to approximately
VIN. If no battery is detected after the 70ms period, the
9
FN9215.1
March 20, 2007
ISL6297
Short Circuit Test
Connection Verification
VIN
V2P9
70ms
DT
500ms
500ms
Red
Green
500ms
500ms
500ms
RED
GRN
off
LEDs
Yellow
off
Red
Charge Starts
EN
Battery (+)
connection
verified
4.4V
VSEN
384 cycles
max.
Trickle current
ICHG
FIGURE 4. EVENT SEQUENCE AT POWER UP
5
0.8V
I REF = ----------------- × 10 ( A )
R IREF
500ms
EN
Battery connected here, but voltage
remains above the battery detect
(falling) threshold
- Open battery detected
VIN
Check if
BAT > 1V
If not: FAULT
4.4V
(EQ. 3)
The trickle charge current is 10% of IREF, that is,
4
0.8V
I Trickle = ----------------- × 10 ( A )
R IREF
(EQ. 4)
4.3V
VSEN
70ms
Trickle current
ICHG
Charge terminates. EN or
POR required before charge
sequence starts again
FIGURE 5. OPEN BATTERY DETECTED
Charge Current and RIREF Selection
When the ISL6297 is used as a traditional linear charger, the
RIREF sets the constant charge current. When working with a
dual-mode, 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 calculated by using the
following equation:
10
The ISL6297 has a comparator with a 50mV offset voltage to
ensure the input voltage is higher than the battery voltage
before charging starts (see the Block Diagram). This
condition, coupled with an RDS(on) of about 400mΩ (max)
requires ILIM be higher than 125mA. The upper limit for ILIM
is 1.5A.
EOC Current and RIMIN Selection
The EOC current level is programmed by the IMIN pin and
can be calculated by the following equation:
4
0.8V
I MIN = ---------------- × 10 ( A )
R IMIN
(EQ. 5)
The EOC current has a programming range up to 400mA.
To qualify as an EOC condition, the battery voltage must be
above the recharge threshold given in the Electrical
Specification table and the charge current needs to drop
below the IMIN level for 3 to 4 cycles of the internal oscillator.
FN9215.1
March 20, 2007
ISL6297
POR Threshold
VIN
V2P9
EN
500ms
DT
Impedance
Charge Cycle
Charge Cycle
RED
15 cycles to 1/8 TIMEOUT
GRN
Recharge
VSEN
2.8V min.
15 cycles
IMIN
ICHG
IMIN
TIMEOUT
FIGURE 6. OPERATION WAVEFORMS
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:
6
T OSC = 0.2 × 10 × C TIME
( sec onds )
(EQ. 6)
A 15nF capacitor results in a 3ms 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 time allowed for the battery to charge before an end of
charge indication is limited to the duration of the TIMEOUT
counter. The TIMEOUT period can be calculated by:
C TIME
TIMEOUT = 14 × -----------------1nF
( minutes )
(EQ. 7)
where 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 EOC indication goes active
when the TIMEOUT counter expires, even if the battery has
not reached full charge. At this point, if the voltage is above
4.05V, the recharge mechanism will continue to charge the
11
cell until the current drops below IMIN. If the TIMEOUT
counter expires before the battery reaches 4.05V, then the
end of charge indication goes active, but the charger turns
off. The charger cannot leave this condition without toggling
the enable pin or cycling the power.
The trickle mode charge has a time limit of 1/8 TIMEOUT. If
the battery voltage does not reach VMIN within that time
period, a TIMEOUT fault is issued and the charger turns off
with a flashing Yellow LED indicator. The charger stays in
trickle mode for at least 15 cycles of the internal oscillator
and, at most, 1/8 of TIMEOUT.
Once the ISL6297 detects that the battery reaches the EOC
condition, it resets the TIMEOUT counter. At the end of this
TIMEOUT period, the charger turns off and does not start
again until the battery reaches a recharge condition.
Recharge Threshold
Once the charger reaches an end of charge condition and
the charger turns off, if the battery voltage drops below the
recharge threshold given in the Electrical Specification table,
the charger starts a re-charge cycle. This is identical to an
inital charge cycle, except the indicator remains green.
LED Indications
The LED indicators show a number of conditions. On initial
power on reset, the LEDs sequence through red, green and
yellow. Once the charge begins, the ISL6297 pulls the RED
pin low to drive a red indicator. Once the charge properly
FN9215.1
March 20, 2007
ISL6297
finishes (either when the EOC condition is qualified or when
the TIMEOUT completes) the ISL6297 releases the RED
output and pulls the GRN pin low to drive a green indicator
while the red indicator turns off. The green LED remains on
unless the input power is recycled, or a fault occurs. During
a recharge operation, the indicator remains green.
When a temperature fault happens, both the RED and the
GRN pins turn on to indicate a yellow color. This fault is
cleared automatically when the temperature again returns to
the normal region. If the FAULT is non-temperature related,
the yellow indicator flashes. This type of fault is latched and
can only be reset by toggling the EN pin or cycling the input
power. Table 2 summarizes the LED indications.
Because the LED outputs provide a constant 10mA current
sink, no external resistors are necessary.
TABLE 2. LED INDICATION SUMMARY
STATUS
RED GRN
Plug In Indication
INDICATION
L
H
Red (500ms)
H
L
Green (500ms)
L
L
Yellow (500ms)
H
H
Off (500ms)
Charging
L
H
Red
Full Charge (EOC) or recharging
H
L
Green
Short circuit Error or trickle charge
TIMEOUT error
L
L
H
H
Yellow (Flashing
1Hz rate)
Over/Under Ambient Temperature
L
L
Yellow
Idle state
H
H
Off or Battery (+)
terminal not
connected
VSEN Pin
BAT
VSEN
R2
VA
+
Enable
VREF
R3
Q1
FIGURE 7. THE INTERNAL VOLTAGE FEEDBACK CIRCUIT
THERMAGUARD™ Charge Current Thermal
Foldback
Over-heating is always a concern in a linear charger or in the
linear region for a dual mode charger. The charge current
thermal foldback function in the ISL6297 frees users from
the over-heating concern.
Figure 8 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 +100°C; then IT
rises at a rate of 1μA/°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 +110°C. The actual charge
current settles between +100°C to +110°C.
When the charger is providing a large current to the cell,
there can be significant voltage drop in the PCB trace
between the charger output and the battery positive terminal.
To minimize this effect, the VSEN pin input provides a low
current monitoring path. This provides a more accurate
reading of the battery voltage. Figure 7 shows the internal
voltage feedback circuit.
IR
IT
ISEN
100OC
Temperature
FIGURE 8. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT
Usually the charge current should not drop below IMIN
because of the thermal foldback. If, in some extreme case
this does happen, the charger does not indicate end-ofcharge unless the battery voltage is already above the
recharge threshold.
12
FN9215.1
March 20, 2007
ISL6297
Ambient Temperature Sensing
The TEMP pin sets the allowable ambient temperature
range for 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 ISL6297
provides the DT pin to set a higher temperature threshold
during the charge operation.
Figure 9 shows the internal circuit for the ambient
temperature sensing function. Two comparators form a
window comparator whose high-threshold is VTMIN and lowthreshold is VTMAX. These two thresholds are given in the
Electrical Specifications. The two MOSFETs (Q1 and Q2)
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 10 (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 10 (B).
The DT pin provides a higher shut down ambient
temperature during the charger operation.
2.9V
V2P9
V2P9
RU
RU
TEMP
TEMP
RT
RT
DT
RD
RQ3
GND
(A)
GND
(B)
FIGURE 10. EQUIVALENT CIRCUITS FOR THE NTC DIVIDER
(A) BEFORE CHARGING STARTS
(B) DURING CHARGING
When the TEMP pin voltage is “out of the window,” as
determined by the VTMIN and VTMAX, the ISL6297 stops
charging and indicates a fault condition. When the
temperature returns to the set range, the charger continues
the charge cycle.
V2P9
2.9V
Under
Temp CP1
R1
100K
VTMIN
+
To TEMP Pin
R2
75K
RU
VTMIN (2.0V)
TEMP
VTMIN- (1.83V)
Q1
Over
Temp
CP2
-
R3
25K
VTMAX
RT
+
Q2
R4
4K
Under
Temp
Q3
GND
RD
FIGURE 9. THE INTERNAL AND EXTERNAL CIRCUIT FOR
THE NTC INTERFACE
13
VTMAX+ (0.788V)
VTMAX (0.714V)
0V
DT
CHG
TEMP
Pin
Voltage
Over
Temp
FIGURE 11. CRITICAL VOLTAGE LEVELS FOR TEMP PIN
As the temperature falls, the TEMP pin voltage rises. When
it exceeds the 2.0V VTMIN threshold, an under temperature
condition exists. This condition does not clear until the TEMP
pin voltage falls back below the threshold minus the
hysteresis voltage (VTMIN-). Similarly, an over-temperature
condition exists when the TEMP pin voltage falls below the
0.714V VTMAX threshold and does return to normal
temperature operation until the voltage rises above the
threshold plus the hysteresis voltage (VTMAX+). The actual
accuracy of the 2.9V supply voltage is not important
because all the thresholds and the TEMP pin voltage are
ratios determined by the resistor dividers, as shown in
Figure 9.
FN9215.1
March 20, 2007
ISL6297
The ratio, K, of the TEMP pin voltage to the bias voltage is:
RT
K = ---------------------RT + RU
With the series resistor RS, EQ. 12 can be re-written as:
RS + R
TCOLD
------------------------------------- = 6.84
R S + R THOT
(EQ. 8)
and
K
R T = ------------- × R
1–K
U
(EQ. 9)
Once the thermistor and the temperature limits are selected,
RS and RU can be calculated using:
At VTMIN,
2.0
K = ----------- = 0.6844
2.88
(EQ. 10)
Similarly, at VTMAX.
0.718
·
K = --------------- = 0.2493
2.88
(EQ. 11)
Using these equations to calculate the ratio of the thermistor
hot to cold resistance results in:
2.27R U
R TCOLD
----------------------= ----------------------· = 6.84
R THOT
0.332R U
(EQ. 12)
(EQ. 15)
R TCOLD – 6.84R THOT
R S = -------------------------------------------------------------5.84
(EQ. 16)
R U = 0.44 × ( R S + R TCOLD )
(EQ. 17)
and
To summarize, the NTC thermistor circuit design requires
three steps:
1. Find an NTC thermistor that satisfies EQ. 14. The
temperature limits are determined by the application
requirement.
2. Calculate the series resistance according to EQ. 16.
3. Calculate the pull-up resistance according to EQ. 17.
and
Example:
(EQ. 13)
R U = 0.44R TCOLD
where RTCOLD and RTHOT are the NTC thermistor
resistance values at the cold and hot temperature limits
respectively.
It is usually difficult to find an NTC thermistor that has the
exact ratio given in EQ. 12. A thermistor with a ratio larger
than 6.84, that is:
The charger is designed to charge the battery with the
temperature range from -5°C to +45°C. The 10kΩ NTC
thermistor NCP15XH103F03RC from Murata
(http://www.murata.com) satisfies EQ. 14. The resistance
values for this thermistor are given in Table 3. The typical
resistance at -5°C and +45°C are:
RTCOLD = 33.8922kΩ and
RTHOT = 4.9169kΩ.
Using EQ. 16 and EQ. 17 result in:
R TCOLD
----------------------≥ 6.84
R THOT
(EQ. 14)
can be used in series with a regular resistor to form an
effective thermistor that has the right ratio, as shown in
Figure 12.
RS = 41.6Ω and RU = 14.931kΩ.
Selecting RS = 41.2Ω and RU = 15kΩ gives a low
temperature threshold of -5.1°C and a high temperature
threshold of +44.9°C.
TABLE 3. RESISTANCE TABLE OF NCP15XH103F03RC
V2P8
RU
RS
ISL6297
RT
Effective NTC
Thermistor
TEMP
GND
TEMP (°C)
R-LOW (kΩ)
R-CENTER (kΩ)
R-HIGH (kΩ)
-10
41.4765
42.5062
43.5570
-5
33.1462
33.8922
34.6515
0
26.6780
27.2186
27.7675
6
20.7560
21.1230
21.4944
7
19.9227
20.2666
20.6143
40
5.7443
5.8336
5.9238
45
4.8333
4.9169
5.0015
50
4.0833
4.1609
4.2395
55
3.4634
3.5350
3.6076
FIGURE 12. EFFECTIVE NTC THERMISTOR CIRCUIT
14
FN9215.1
March 20, 2007
ISL6297
Hysteresis Temperature Calculation
Re-arranging EQ. 8, and including the effect of RS, gives:
K
R T = ------------- × R U – R S
1–K
(EQ. 18)
Using the K/(1-K) ratio at the hysteresis threshold, equation
18 provides the NTC thermistor resistance at the threshold.
Continuing the example above, the thermistor values are
found to be 26.2kΩ and 7.3kΩ respectively at the low and
high hysteresis temperatures. The corresponding
temperatures are found from Table 3. Cold recovery is about
+1.0°C and the hot recovery is about +33.9°C. In other
words, the hysteresis temperatures for the low and high
limits are approximately +6.1°C and +11.0°C, respectively.
Temperature Tolerance Calculation
The temperature accuracy is affected by the accuracy of the
thresholds, RS, RU, and the NTC thermistor. Using the
maximum ratio K, maximum possible RU, and minimum RS
results in the maximum value of RT from EQ. 18, that is:
K MAX
R TMAX = ------------------------- × R UMAX – R SMIN
1 – K MAX
(EQ. 19)
From the Electrical Specification table, the maximum K at
cold is found to be 0.71. Assuming the resistors have 1%
accuracy, the maximum RU is 15.15kΩ and the minimum RS
is 40.8Ω. The resultant maximum RT is then found to be
36.3kΩ and the corresponding temperature is about
negative +6.4°C. Hence the temperature tolerance is
+1.3°C. Similarly, at high temperature, the minimum K is
0.24, the minimum RU value is 14.85kΩ and the maximum
RS is 41.6Ω. Hence, the highest temperature is +46.0°C and
the tolerance is +1.1°C.
Charging Temperature Range
The selection of RD follows the following equation:
o
o
R D = R T ( @45 C ) – R T ( @45 C + ΔT )
(EQ. 20)
where RT(@+45°C) is the thermistor resistance at 45°C and
the RT (@+45°C + ΔT) is the resistance at some desired
temperature difference above +45°C. Figure 13 shows the
temperature windows before, during, and after charging.
From the example, before and after charging, the
temperature window is -5°C to +45°C with +6°C and +4°C
hysteresis. During charging, the high temperature limit
changes to +45°C + ΔT. If this limit is exceeded, the charger
is stopped and the temperature has to come back to below
+41°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 13.
15
+45°C+ΔT
+44.7°C
+32.0°C
Less than
+2°C
+0.6°C
-5.1°C
FIGURE 13. BOARD TEMPERATURE MONITORING. WHEN
NOT CHARGING, THE TEMPERATURE WINDOW
IS BETWEEN -5°C AND +45°C. ONCE THE
CHARGER STARTS, THE TEMPERATURE
WINDOW IS ~-3°C TO +45°C+ ΔT
2.9V Bias Voltage
A pre-regulator provides a regulated 2.9V on the V2P9 pin,
unless VIN drops below 2.9V plus 250mV (typical). Then the
output voltage tracks the input voltage with a 250mV dropout
voltage. The 2.9V output turns off when VIN drops below the
VIN (falling) threshold. A minimum 0.1μF X5R ceramic
capacitor is required for decoupling the pre-regulator.
The V2P9 output is used for biasing external circuits. The
maximum loading current on this pin is 30mA. Mainly, the
load current comes from the indication LEDs.
Board Layout Recommendations
The ISL6297 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 ISL6297
evaluation board for layout examples.
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”
FN9215.1
March 20, 2007
ISL6297
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
MIN
NOMINAL
MAX
NOTES
A
0.80
0.90
1.00
-
A1
-
-
0.05
-
A2
-
-
1.00
A3
b
0.23
D
0.28
9
0.35
5, 8
4.00 BSC
D1
D2
9
0.20 REF
-
3.75 BSC
1.95
2.10
9
2.25
7, 8
E
4.00 BSC
-
E1
3.75 BSC
9
E2
1.95
e
2.10
2.25
7, 8
0.65 BSC
-
k
0.25
-
-
-
L
0.50
0.60
0.75
8
L1
-
-
0.15
10
N
16
2
Nd
4
3
Ne
4
3
P
-
-
0.60
9
θ
-
-
12
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 & 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 back (L1) maybe present. L
minus L1 to be equal to or greater than 0.3mm.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
16
FN9215.1
March 20, 2007