POWER LP28300

Preliminary Datasheet
LP28300
2A Synchronous Buck Li-ion Charger
General Description
Features
The LP28300 is a 2A Li-Ion battery charger intended for5V
wall adapters. It utilizes a 1.5MHz synchronous buck
converter topology to reduce power dissipation during
charging. Low power dissipation, an internal MOSFET
allow a physically small charger that can be embedded in a
wide range of handheld applications. The LP28300 includes
complete charge termination circuitry, automatic recharge
and a ±1% 4.2V float voltage. Input short-circuit protection
is included so no blocking diode is required.
¾
¾
¾
¾
Battery charge current, charge timeout and end-of-charge
indication parameters are set with external components.
Additional features include shorted cell detection,
temperature qualified charging and overvoltage protection.
The LP28300 is available in a low profile (0.75mm)
10-lead(3mm × 3mm) DFN package.
¾
¾
¾
¾
¾
Order Information
LP28300 -
□ □
Very Low Power Dissipation
2A Maximum Charge Current
No External MOSFETs and Blocking Diode Required
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
Drainage Charge Current Thermal Regulation Status
Outputs for LED or System Interface
Optional Battery Temperature Monitoring Before and
During Charge Automatic Sleep Mode for Low-Power
Consumption Available in 3mm × 3mm TDFN-10
Package
RoHS Compliant and 100% Lead (Pb)-Free
Typical Application Circuit
□
F: Pb-Free
Package Type
QV: TDFN-10
Applications
—
—
—
—
—
—
Portable Media Players
Cellular and Smart mobile phone
PDA/DSC
Handheld Battery-Powered Devices
Handheld Computers
Charging Docks and Cradles
Marking Information
Please see website.
LP28300 – 01
Version
1.1 Datasheet
Sep.-2010
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Page 1 of 10
Preliminary Datasheet
LP28300
Functional Pin Description
P a c k a g e Ty p e
Pin Configurations
VIN
1
TS
2
EN
3
STAT
4
BATT
5
10
GND
9
SW
8
NC
7
VIN
6
SNS
LP28300
TDFN- 10
11
PGND
Pin Description
PIN
PIN
Number
VIN
1,7
TS
2
EN
3
STAT
4
BATT
5
SNS
6
NC
8
SW
9
GND
PGND
10
11
LP28300 – 01
Version
DESCRIPTION
Positive Supply Voltage Input. This pin connects to the power devices inside the chip. VIN ranges from
4V to 5.5V for normal operation. Operation down to the under-voltage lockout threshold is allowed
with current limited wall adapters. Decouple with a 10µF or larger surface mounted ceramic capacitor.
NTC (Negative Temperature Coefficient) Thermistor Input. With an external 10kΩ NTC thermistor to
ground, this pin senses the temperature of the battery pack and stops the charger when the temperature
is out of range. To disable the temperature qualification function, ground the NTC pin.
Enable Input Pin. Pulling the EN pin high places the LP28300 into a low power state where the BAT
drain current drops to less than 3µA and the supply current is reduced to less than 50µA. For normal
operation, pull the pin low.
Open-Drain Charge Status Output. When the battery is charging, the STAT pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is completed, When the LP28300 detects an
under voltage lockout condition, STAT is forced high impedance.
Battery Charger Output Terminal. Connect a 22µF ceramic chip capacitor between BAT and PGND to
keep the ripple voltage small.
Internal Sense Resistor. Connect to external inductor.
Current Amplifier Sense Input. A sense resistor, RSENSE, must be connected between the SENSE and
BAT pins. The maximum charge current is equal to 100mV/RSENSE.
No connector.
Switch Node Connection. This pin connects to the drains of the internal main and synchronous power
MOSFET switches. Connect to external inductor.
Ground.
Power Ground Pad.
1.1 Datasheet
Sep.-2010
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Page 2 of 10
Preliminary Datasheet
LP28300
Typical Application Circuits
VIN
1
VIN
7
3
VIN
EN
4
1R
LP28300 SNS
10
VIN
1
1R
LP28300
STAT
10
BATT
10uH
6
SNS
RSNS
100mR
5
2
TS
PGND
GND
10uF
1Cell
9
BATT
10uF
22uF
Rts
10K
11
SW
VIN
EN
4
2
1uF
VIN
7
3
RSNS
100mR
5
TS
PGND
10uF
10uH
6
BATT
STAT
GND
10uF
9
SW
22uF
1uF
11
BATT
Rts
10K
USB Charge CTRL
H:USB Charging, Iset=500mA
L:DC Adapter Charging, Iset=1300mA
VIN
1
7
3
VIN
VIN
EN
1R
4
SW
LP28300
STAT
BATT
10uF
10
Version
1.1 Datasheet
Sep.-2010
PGND
GND
10uF
LP28300 – 01
SNS
TS
RSNS1 100mR
Q1 9
6
10uH
RSNS2
200mR
5
1uF 22uF
2
11
www.lowpowersemi.com
Rts
10K
BATT
Page 3 of 10
Preliminary Datasheet
LP28300
Function Block Diagram
GND
Vin
SW
SNS
Vin
EN
GND
BATT
STAT
Absolute Maximum Ratings
— Input Voltage to GND (VIN) ----------------------------------------------------------------------------- 2.6V to 6.5V
— BAT, ISET, STAT (VX) ------------------------------------------------------------------------ 0.3V to VIN+0.3V
— BAT Short-Circuit Duration ---------------------------------------------------------------------------- Continuous
— BAT Pin Current ------------------------------------------------------------------------------------------ 2500mA
— Maximum Junction Temperature ---------------------------------------------------------------------------- 125°C
— Operating Junction Temperature Range (TJ) ----------------------------------------------------- -40℃ to 85°C
— Maximum Soldering Temperature (at leads, 10 sec) ------------------------------------------------------ 260°C
Thermal Information
—
Maximum Power Dissipation (PD,TA<40°C) -------------------------------------------------------------- 2W
—
Thermal Resistance (JA) ---------------------------------------------------------------------------------- 46℃/W
LP28300 – 01
Version
1.1 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 4 of 10
Preliminary Datasheet
LP28300
Electrical Characteristics (The specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.)
SYMBOL
VIN
PARAMETER
Adapter/USB Voltage Range
ICC
VFLOAT
CONDITIONS
Input Supply Current
Regulated Output (Float) Voltage
Charge Mode (Note 4), RISET = 10k
Standby Mode (Charge Terminated)
Shutdown Mode (RISET Not
Connected,
VCC < VBAT, or VCC < VUV)
0°C ≤ TA ≤ 85°C, IBAT = 40mA
RSNS = 100mΩ, Current Mode
RSNS = 68mΩ, Current Mode
IBAT
MIN
2.65
4.158
860
1300
0
BAT Pin Current
Standby Mode, VBAT = 4.2V
Shutdown Mode (RISET Not
Connected) Sleep Mode, VCC = 0V
ITRIKL
Trickle Charge Current
VTRIKL
Trickle Charge Threshold Voltage
VTRHYS
Trickle Charge Hysteresis Voltage
VBAT < VTRIKL, RSNS = 100mΩ(Note 80
5)
RSNS = 100mΩ,VBAT Rising (Note 5) 2.8
RSNS = 100mΩ,(Note 5)
60
VSNS
ISTAT
SNS Pin Voltage
STAT Pin Weak Pull-Down Current
RISET = 10k, Current Mode
VSTAT = 5V
VSTAT
STAT Pin Output Low Voltage
ISTAT = 5mA
ΔVRESTAT
TLIM
TSS
ISNS
LP28300 – 01
Recharge Battery Threshold Voltage VFLOAT - VRESTAT
Junction Temperature in Constant Temperature Mode
Soft-Start Time
IBAT = 0 to IBAT =850V/RISET
ISET Pin Pull-Up Current
Version
1.1 Datasheet
Sep.-2010
www.lowpowersemi.com
88
8
100
TYP.
5
MAX UNITS
6
V
300
2000
200
500
25
4.2
1000
1470
-2.5
±1
±1
100
2.9
80
100
20
0.35
150
50
4.242
1120
1620
-6
±2
±2
120
3.0
110
116
35
0.6
200
120
uA
V
mA
uA
mA
V
mV
mV
uA
V
mV
100
3
°C
uS
uA
Page 5 of 10
Preliminary Datasheet
LP28300
Typical Operating Characteristics
LP28300 – 01
Version
1.1 Datasheet
Sep.-2010
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Page 6 of 10
Preliminary Datasheet
LP28300
Operation
The LP28300 is a constant current, constant voltage
Li-Ion battery charger controller that uses a current
mode PWM step-down (buck) switching
architecture. The charge current is set by an external
sense resistor (RSENSE) across the SENSE and BAT
pins. The final battery float voltage is internally set
to 4.2V per cell. For batteries like lithium-ion that
require accurate final float voltage, the internal 2.4V
reference, voltage amplifier and the resistor divider
provide regulation with ±1% accuracy.
Figure 1.Typical Charge Profile
A charge cycle begins when the voltage at the VCC
pin rises above the UVLO level and is 250mV or
more greater than the battery voltage. At the
beginning of the charge cycle, if the battery voltage
is less than the trickle charge threshold, 2.9V for the
4.2 version, the charger goes into trickle charge
mode. The trickle charge current is internally set to
15% of the full-scale current. If the battery voltage
stays low for 30 minutes, the battery is considered
faulty and the charge cycle is terminated. When the
battery voltage exceeds the trickle charge threshold,
the charger goes into the full-scale constant current
charge mode. In constant current mode, the charge
current is set by the external sense resistor RSENSE
and an internal 100mV reference;
start to decrease. When the current drops to 25%
of the full-scale charge current, an internal
comparator turns off the internal pull-down
N-channel MOSFET at the STAT pin, and connects
a weak current source to ground to indicate a near
end-of-charge condition. A 10kΩ NTC (negative
temperature coefficient) thermistor can be
connected from the NTC pin to ground for battery
temperature qualification. The charge cycle is
suspended when the temperature is outside of the
0°C to 50°C window.
Shutdown
The LP28300 can be shut down by pulling the
COMP pin to ground which pulls the GATE pin
high turning off the external P-channel MOSFET.
When the COMP pin is released, the internal timer
is reset and a new charge cycle starts. In shutdown,
the output of the CHRG pin is high impedance and
the quiescent current remains at 1.5mA. Removing
the input power supply will put the charger into
sleep mode. If the voltage at the VCC pin drops
below (VBAT + 250mV) or below the UVLO level,
the LP28300 goes into a low current (ICC = 10µA)
sleep mode, reducing the battery drain current.
Automatic Recharge
Once the charge cycle is terminated, the LP28300
continuously monitors the voltage on the BAT pin
using a comparator with a 2ms filter time
(tRECHARGE). A charge cycle restarts when the battery
voltage falls below 4.05V (which corresponds to
approximately 80% to 90% battery capacity). This
ensures that the battery is kept at or near a fully
charged condition and eliminates the need for
periodic charge cycle initiations. STAT output enters
a strong pull-down state during recharge cycles.
When the battery voltage approaches the
programmed float voltage, the charge current will
Battery Temperature Detection
A negative temperature coefficient (NTC)
thermistor located close to the battery pack can be
used to monitor battery temperature and will not
allow charging unless the battery temperature is
within an acceptable range. Connect a 10kΩ
thermistor from the TS pin to ground. If the
LP28300 – 01
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Version
1.1 Datasheet
Sep.-2010
Page 7 of 10
Preliminary Datasheet
LP28300
temperature rises to 50°C, the resistance of the
one-half of output charge current. Actual
NTC will be approximately 4.2kΩ. With the 85µA
pull-up current source, the Hot temperature
voltage threshold is 360mV. For Cold temperature,
the voltage threshold is set at 2.4V which is equal
to 0°C (Rts 28kΩ) with 85µA of pull-up current.
If the temperature is outside the window, the
GATE pin will be pulled up to VCC and the timer
frozen while the output status at the STAT pin
remains the same. The charge cycle begins or
resumes once the temperature is within the
acceptable range. Short the TS pin to ground to
disable the temperature qualification feature.
However the user may modify these thresholds by
adding two external resistor. See figure 3.
capacitance value is not critical. Solid tantalum
capacitors have a high ripple current rating in a
relatively small surface mount package, but
caution must be used when tantalum capacitors
are used for input bypass. High input surge
currents can be created when the adapter is
hot-plugged to the charger and solid tantalum
capacitors have a known failure mechanism when
subjected to very high turn-on surge currents.
Selecting the highest possible voltage rating on
the capacitor will minimize problems. Consult
with the manufacturer before use. The selection
of output capacitor COUT is primarily determined
by the ESR required to minimize ripple voltage
and load step transients. The output ripple ∆VOUT
is approximately bounded by:

Figure 2. Temperature Sensing Configuration
Since ∆IL increases with input voltage, the output
ripple is highest at maximum input voltage.
Typically, once the ESR requirement is satisfied,
the capacitance is adequate for filtering and has
the necessary RMS current rating. Switching
ripple current splits between the battery and the
output capacitor depending on the ESR of the
output capacitor and the battery impedance. EMI
considerations usually make it desirable to
minimize ripple current in the battery leads.
Ferrite beads or an inductor may be added to
increase battery impedance at the 500kHz
switching frequency. If the ESR of the output
capacitor is 0.2Ω and the battery impedance is
raised to 4Ω with a bead or inductor, only 5% of
the current ripple will flow in the battery.
Figure 3. Temperature Sensing Thresholds
Input and Output Capacitors
Since the input capacitor is assumed to absorb all
input switching ripple current in the converter, it
must have an adequate ripple current rating.
Worst-case RMS ripple current is approximately
Inductor Selection
A high (1.5MHz) operating frequency was chosen
for the buck switcher in order to minimize the size
of the inductor. However, take care to use inductors
with low core losses at this frequency. A good
LP28300 – 01
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Version
1.1 Datasheet
Sep.-2010
Page 8 of 10
Preliminary Datasheet
choice is the IHLP-2525AH-01from Vishay Dale.
LP28300
typical application. With 1.5µH and2A charge
current:
To calculate the inductor ripple current:
and
where VBAT is the battery voltage, VIN is the input
voltage, L is the inductance and f is the PWM
oscillator frequency(typically 1.5MHz). Maximum
inductor ripple current occurs at maximum VIN and
VBAT = VIN/2.
Layout Considerations
Peak inductor current will be:
where IBAT is the maximum battery charging
current.
When sizing the inductor make sure that the peak
current will not exceed the saturation current of the
inductors. Also, ∆IL should never exceed 0.4(IBAT)
as this may interfere with proper operation of the
output short-circuit protection comparator. 1.5µH
provides reasonable inductor ripple current in a
LP28300 – 01
Version
1.1 Datasheet
Sep.-2010
Switch rise and fall times are kept under 5ns for
maximum efficiency. To minimize radiation, the SW
pin and input bypass capacitor leads (between VIN
and PGND) should be kept as short as possible. A
ground plane should be used under the switching
circuitry to prevent inter plane coupling. The
exposed pad must be connected to the ground plane
for proper power dissipation. The other paths
contain only DC and/or 1.5MHz tri-wave ripple
current and are less critical. With the exception of
the input and output filter capacitors(which should
be connected to PGND) all other components that
return to ground should be connected to GND.
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Preliminary Datasheet
LP28300
Packaging Information
LP28300 – 01
Version
1.1 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 10 of 10