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ISL6251A Schematic ( PDF Datasheet ) - Intersil Corporation

Teilenummer ISL6251A
Beschreibung Low Cost Multi Chemistry Battery Charger Controller
Hersteller Intersil Corporation
Logo Intersil Corporation Logo 




Gesamt 20 Seiten
ISL6251A Datasheet, Funktion
www.DataSheet4U.com
®
Data Sheet
ISL6251, ISL6251A
April 22, 2005
FN9202.0
Low Cost Multi-Chemistry Battery
Charger Controller
The ISL6251, ISL6251A is a highly integrated battery
charger controller for Li-Ion/Li-Ion polymer batteries and
NiMH batteries. High Efficiency is achieved by a
synchronous buck topology and the use of a MOSFET,
instead of a diode, for selecting power from the adapter or
battery. The low side MOSFET emulates a diode at light
loads to improve the light load efficiency and prevent system
bus boosting.
The constant output voltage can be selected for 2, 3 and 4
series Li-Ion cells with 0.5% accuracy over temperature. It
can be also programmed between 4.2V+5%/cell and
4.2V-5%/cell to optimize battery capacity. When supplying
the load and battery charger simultaneously, the input
current limit for the AC adapter is programmable to within
3% accuracy to avoid overloading the AC adapter, and to
allow the system to make efficient use of available adapter
power for charging. It also has a wide range of
programmable charging current. The ISL6251, ISL6251A
provides outputs that are used to monitor the current drawn
from the AC adapter, and monitor for the presence of an AC
adapter. The ISL6251, ISL6251A automatically transitions
from regulating current mode to regulating voltage mode.
Ordering Information
PART
NUMBER
TEMP
RANGE (°C)
PACKAGE
PKG.
DWG. #
ISL6251HRZ
(Notes 1, 2)
-10 to 100 28 Ld 5x5 QFN L28.5×5
(Pb-free)
ISL6251HAZ
(Notes 1, 2)
-10 to 100 24 Ld QSOP
(Pb-free)
M24.15
ISL6251AHRZ -10 to 100 28 Ld 5x5 QFN L28.5×5
(Notes 1, 2)
(Pb-free)
ISL6251AHAZ
(Notes 1, 2)
-10 to 100 24 Ld QSOP
(Pb-free)
M24.15
NOTES:
1. 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.
2. Add “-T” for Tape and Reel.
Features
• ±0.5% Charge Voltage Accuracy (-10°C to 100°C)
• ±3% Accurate Input Current Limit
• ±5% Accurate Battery Charge Current Limit
• ±25% Accurate Battery Trickle Charge Current Limit
(ISL6251A)
• Programmable Charge Current Limit, Adapter Current
Limit and Charge Voltage
• Fixed 300kHz PWM Synchronous Buck Controller with
Diode Emulation at Light Load
• Output for Current Drawn from AC Adapter
• AC Adapter Present Indicator
• Fast Input Current Limit Response
• Input Voltage Range 7V to 25V
• Support 2, 3 and 4 Cells Battery Pack
• Up to 17.64V Battery-Voltage Set Point
• Thermal Shutdown
• Support Pulse Charging
• Less than 10µA Battery Leakage Current
• Charge Any Battery Chemistry: Li-Ion, NiCd, NiMH, etc.
• Pb-Free Available (RoHS Compliant)
Applications
• Notebook, Desknote and Sub-notebook Computers
• Personal Digital Assistant
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.






ISL6251A Datasheet, Funktion
www.DataSheet4U.com
ISL6251, ISL6251A
Typical Operating Performance DCIN=20V, 4S2P Li-Battery, TA=25°C, unless otherwise noted.
0.6
VDD=5.075V
EN=0
0.3
0
0.1
VREF=2.390V
0.08
0.06
0.04
-0.3 0.02
-0.6
0 8 16 24 32
LOAD CURRENT (mA)
FIGURE 1. VDD LOAD REGULATION
40
0
0 100 200 300
LOAD CURRENT (µA)
FIGURE 2. VREF LOAD REGULATION
400
10
9
8
7
6
5
4
3
2
1
0
10 20 30 40 50 60 70 80 90 100
CSIP-CSIN (mV)
FIGURE 3. ICM ACCURACY vs AC ADAPTER CURRENT
1
0 .9 6
0 .9 2
0 .8 8
0 .8 4
VCSON=12.6V
(3 CELLS)
VCSON=8.4V
2 CELLS
VCSON=16.8V
4 CELLS
0 .8
0 .76
0 0 .5 1 1.5 2 2.5 3 3 .5 4
CHARGE CURRENT (A)
FIGURE 4. SYSTEM EFFICIENCY vs CHARGE CURRENT
LOAD STEP: 0-4A
CHARGE CURRENT: 3A
AC ADAPTER CURRENT LIMIT: 5.15A
LOAD
CURRENT
5A/div
ADAPTER
CURRENT
5A/div
CHARGE
CURRENT
2A/div
BATTERY
VOLTAGE
2V/div
FIGURE 5. LOAD TRANSIENT RESPONSE
6
CSON
5V/div
EN
5V/div
INDUCTOR
CURRENT
2A/div
CHARGE
CURRENT
2A/div
FIGURE 6. CHARGER ENABLE & SHUTDOWN
FN9202.0
April 22, 2005

6 Page









ISL6251A pdf, datenblatt
www.DataSheet4U.com
ISL6251, ISL6251A
Theory of Operation
Introduction
The ISL6251, ISL6251A includes all of the functions
necessary to charge 2 to 4 cell Li-Ion and Li-polymer
batteries. A high efficiency synchronous buck converter is
used to control the charging voltage and charging current up
to 10A. The ISL6251, ISL6251A has input current limiting
and analog inputs for setting the charge current and charge
voltage; CHLIM inputs are used to control charge current
and VADJ inputs are used to control charge voltage.
The ISL6251, ISL6251A charges the battery with constant
charge current, set by CHLIM input, until the battery voltage
rises up to a programmed charge voltage set by VADJ input;
then the charger begins to operate at a constant voltage
charge mode.
The EN input allows shutdown of the charger through a
command from a micro-controller. It also uses EN to safely
shutdown the charger when the battery is in extremely hot
conditions. The amount of adapter current is reported on the
ICM output. Figure 11 shows the IC functional block
diagram.
The synchronous buck converter uses external N-channel
MOSFETs to convert the input voltage to the required
charging current and charging voltage. Figure 12 shows the
ISL6251, ISL6251A typical application circuit with charging
current and charging voltage fixed at specific values. The
typical application circuit shown in Figure 13 shows the
ISL6251, ISL6251A typical application circuit which uses a
micro-controller to adjust the charging current set by CHLIM
input. The voltage at CHLIM and the value of R1 sets the
charging current. The DC/DC converter generates the
control signals to drive two external N-channel MOSFETs to
regulate the voltage and current set by the ACLIM, CHLIM,
VADJ and CELLS inputs.
The ISL6251, ISL6251A features a voltage regulation loop
(VCOMP) and two current regulation loops (ICOMP). The
VCOMP voltage regulation loop monitors CSON to ensure
that its voltage never exceeds the voltage and regulates the
battery charge voltage set by VADJ. The ICOMP current
regulation loops regulate the battery charging current
delivered to the battery to ensure that it never exceeds the
charging current limit set by CHLIM; and the ICOMP current
regulation loops also regulate the input current drawn from
the AC adapter to ensure that it never exceeds the input
current limit set by ACLIM, and to prevent a system crash
and AC adapter overload.
PWM Control
The ISL6251, ISL6251A employs a fixed frequency PWM
current mode control architecture with a feed forward
function. The feed-forward function maintains a constant
modulator gain of 11 to achieve fast line regulation as the
buck input voltage changes. When the battery charge
voltage approaches the input voltage, the DC/DC converter
operates in dropout mode, where there is a timer to prevent
the frequency from dropping into the audible frequency
range. It can achieve duty cycle of up to 99.6%.
To prevent boosting of the system bus voltage, the battery
charger operates in standard-buck mode when CSOP-
CSON drops below 4.25mV. Once in standard-buck mode,
hysteresis does not allow synchronous operation of the
DC/DC converter until CSOP-CSON rises above 12.5mV.
An adaptive gate drive scheme is used to control the dead
time between two switches. The dead time control circuit
monitors the LGATE output and prevents the upper side
MOSFET from turning on until LGATE is fully off, preventing
cross-conduction and shoot-through. In order for the dead
time circuit to work properly, there must be a low resistance,
low inductance path from the LGATE driver to MOSFET
gate, and from the source of MOSFET to PGND. The
external Schottky diode is between the VDDP pin and BOOT
pin to keep the bootstrap capacitor charged.
Setting the Battery Regulation Voltage
The ISL6251, ISL6251A uses a high-accuracy trimmed
band-gap voltage reference to regulate the battery charging
voltage. The VADJ input adjusts the charger output voltage,
and the VADJ control voltage can vary from 0 to VREF,
providing a 10% adjustment range (from 4.2V-5% to
4.2V+5%) on CSON regulation voltage. An overall voltage
accuracy of better than 0.5% is achieved.
The per-cell battery termination voltage is a function of the
battery chemistry. Consult the battery manufacturers to
determine this voltage.
• Float VADJ to set the battery voltage VCSON=4.2V ×
number of the cells,
• Connect VADJ to VREF to set 4.41V × number of cells,
• Connect VADJ to ground to set 3.99V × number of the
cells.
So, the maximum battery voltage of 17.6V can be achieved.
Note that other battery charge voltages can be set by
connecting a resistor divider from VREF to ground. The
resistor divider should be sized to draw no more than 100µA
from VREF; or connect a low impedance voltage source like
the D/A converter in the micro-controller. The programmed
battery voltage per cell can be determined by the following
equation:
VCELL = 0.175 VVADJ + 3.99 V
Connect CELLS as shown in Table 1 to charge 2, 3 or 4 Li+
cells. When charging other cell chemistries, use CELLS to
select an output voltage range for the charger. The internal
error amplifier gm1 maintains voltage regulation. The voltage
error amplifier is compensated at VCOMP. The component
values shown in Figure 12 provide suitable performance for
most applications. Individual compensation of the voltage
12 FN9202.0
April 22, 2005

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