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KB4054 Schematic ( PDF Datasheet ) - Kingbor Technology

Teilenummer KB4054
Beschreibung Li-Ion Battery Charger
Hersteller Kingbor Technology
Logo Kingbor Technology Logo 




Gesamt 15 Seiten
KB4054 Datasheet, Funktion
Kingbor Technology Co.,Ltd
TEL:(86)0755-26508846 FAX:(86)0755-26509052
KB4054
Li-Ion Battery Charger
FEATURES
Programmable Charge Current Up to 600mA
No MOSFET, Sense Resistor or Blocking
Diode Required
Complete Linear Charger in SOT Package for
Single Cell Lithium-Ion Batteries
Constant-Current/Constant-Voltage Operation with
Thermal Regulation to Maximize Charge Rate
Without Risk of Overheating
Charges Single Cell Li-Ion Batteries Directly
from USB Port
Preset 4.2V Charge Voltage with ±1% Accuracy
Charge Current Monitor Output for Gas
Gauging
Automatic Recharge
Charge Status Output Pin
C/10 Charge Termination
25µA Supply Current in Shutdown
2.9V Trickle Charge Threshold (KB4054)
Available Without Trickle Charge (KB4054X)
Soft-Start Limits Inrush Current
Available in SOT23-5 Package
Cellular Telephones, PDAs, MP3 Players
Charging Docks and Cradles
Bluetooth Applications
DESCRIPTION
The KB 4054 is a complete constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its ThinSOT package and low external component count
make the KB4054 ideally suited for portable applications.
Furthermore, the KB4054 is specifically designed to work
within USB power specifications.
No external sense resistor is needed, and no blocking
diode is required due to the internal MOSFET architecture.
Thermal feedback regulates the charge current to limit the
die temperature during high power operation or high
ambient temperature. The charge voltage is fixed at 4.2V,
and the charge current can be programmed externally with
a single resistor. The KB4054 automatically terminates
the charge cycle when the charge current drops to 1/10th
the programmed value after the final float voltage is
reached.
When the input supply (wall adapter or USB supply) is
removed, the KB4054 automatically enters a low current
state, dropping the battery drain current to less than 2µA.
The KB4054 can be put into shutdown mode, reducing
the supply current to 25µA.
Other features include charge current monitor, undervoltage
lockout, automatic recharge and a status pin to indicate
charge termination and the presence of an input voltage.
TYPICAL APPLICATION
450mA Single Cell Li-Ion Charger
VIN
4.5V TO 5.5V
1µF 4
VCC BAT 3
KB4054-4.2
5
PROG
450mA
4.2V
GND
Li-Ion
2.2k BATTERY
2
1






KB4054 Datasheet, Funktion
Kingbor Technology Co.,Ltd
TEL:(86)0755-26508846 FAX:(86)0755-26509052
KB4054
PIN FUNCTIONS
CHRG (Pin 1): Open-Drain Charge Status Output. When
the battery is charging, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is
completed, a weak pull-down of approximately 20µA is
connected to the CHRG pin, indicating an “AC present”
condition. When the KB4054 detects an undervoltage
lockout condition, CHRG is forced high impedance.
GND (Pin 2): Ground.
BAT (Pin 3): Charge Current Output. Provides charge
current to the battery and regulates the final float voltage
to 4.2V. An internal precision resistor divider from this pin
sets the float voltage which is disconnected in shutdown
mode.
VCC (Pin 4): Positive Input Supply Voltage. Provides
power to the charger. VCC can range from 4.25V to 6.5V
and should be bypassed with at least a 1µF capacitor.
When VCC drops to within 30mV of the BAT pin voltage, the
KB4054 enters shutdown mode, dropping I BAT to less
than 2µA.
PROG (Pin 5): Charge Current Program, Charge Current
Monitor and Shutdown Pin. The charge current is pro-
grammed by connecting a 1% resistor, RPROG, to ground.
When charging in constant-current mode, this pin servos
to 1V. In all modes, the voltage on this pin can be used to
measure the charge current using the following formula:
IBAT = (VPROG/RPROG) • 1000
The PROG pin can also be used to shut down the charger.
Disconnecting the program resistor from ground allows
a 3µA current to pull the PROG pin high. When it reaches
the 1.21V shutdown threshold voltage, the charger enters
shutdown mode, charging stops and the input supply
current drops to 25µA. This pin is also clamped to
approximately 2.4V. Driving this pin to voltages beyond
the clamp voltage will draw currents as high as 1.5mA.
Reconnecting RPROG to ground will return the charger to
normal operation.
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KB4054 pdf, datenblatt
Kingbor Technology Co.,Ltd
TEL:(86)0755-26508846 FAX:(86)0755-26509052
KB4054
APPLICATIONS INFORMATION
VS
RCC
VCC
BAT
1µF KB4054
PROG
GND
RPROG
Li-Ion
CELL
Figure 3. A Circuit to Maximize Thermal Mode Charge Current
Solving for IBAT using the quadratic formula2.
IBAT =
(VS VBAT )
⎝⎜
(VS
VBAT
)2
4RCC
(120°C
θJA
TA
)
⎠⎟
2RCC
Using RCC = 0.25, VS = 5V, VBAT = 3.75V, TA = 25°C and
θJA = 125°C/W we can calculate the thermally regulated
charge current to be:
IBAT = 708.4mA
While this application delivers more energy to the battery
and reduces charge time in thermal mode, it may actually
lengthen charge time in voltage mode if VCC becomes low
enough to put the KB4054 into dropout. Figure 4 shows
how this circuit can result in dropout as RCC becomes
large.
This technique works best when RCC values are minimized
to keep component size small and avoid dropout. Remem-
ber to choose a resistor with adequate power handling
capability.
VCC Bypass Capacitor
Many types of capacitors can be used for input bypassing,
however, caution must be exercised when using multi-
layer ceramic capacitors. Because of the self-resonant and
high Q characteristics of some types of ceramic capaci-
tors, high voltage transients can be generated under some
start-up conditions, such as connecting the charger input
to a live power source. Adding a 1.5resistor in series
with an X5R ceramic capacitor will minimize start-up
voltage transients. For more information, refer to Applica-
tion Note 88.
Charge Current Soft-Start
The KB4054 includes a soft-start circuit to minimize the
inrush current at the start of a charge cycle. When a charge
cycle is initiated, the charge current ramps from zero to the
full-scale current over a period of approximately 100µs.
This has the effect of minimizing the transient current load
on the power supply during start-up.
1000
VS = 5V
800
CONSTANT
CURRENT
600
VS = 5.5V
VS = 5.25V
400 THERMAL
MODE
DROPOUT
200
VBAT = 3.75V
TA = 25°C
θJA = 125°C/W
0 RPROG = 1.25k
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75
RCC ()
Figure 4. Charge Current vs RCC
Note 2: Large values of RCC will result in no solution for IBAT. This indicates that the KB4054
will not generate enough heat to require thermal regulation.
12

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