LP28056

Preliminary Datasheet
LP28056
1.2A Single-chip Li-ion and Li-POL Charge with OVP
General Description
Features
The LP28056 is a complete constant-current/ constantvoltage linear charger for single cell lithium-ion batteries.
Its TDFN-10 package and low external component count
make the LP28056 ideally suited for portable applications.
Furthermore, the LP28056 is specifically designed to work
within USB power specifications. Its have a over voltage
protection in input with 6.5V and support over zero
voltages of battery can charge enable.
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 ISET rammed externally with
a single resistor. The LP28056 automatically terminates the
charge cycle when the charge current drops to 1/10th the
ISET rammed value after the final float voltage is reached.
When the input supply (wall adapter or USB supply) is
removed, the LP28056 automatically enters a low current
state, dropping the battery drain current to less than 2µA.
The LP28056 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.
z Very Low Power Dissipation
z Vin Over Voltage Protection:6.5V
z Short-circuit protection
z Programmable Charge Current Up to 1200mA
z No MOSFET, Sense Resistor or Blocking Diode
Required
z Constant-Current/Constant-Voltage Operation with
Thermal Regulation to Maximize Charge Rate Without
Risk of Overheating
z Charges Single Cell Li-Ion Batteries Directly from USB
Port
z 25µA Supply Current in Shutdown
z Time Pre-charge Conditioning With Safety Timer
Reverse Leakage Protection Prevents Battery
z Drainage Charge Current Thermal Regulation Status
Outputs for LED or System Interface
z Indicates Charge and Fault Conditions
z Optional Battery Temperature Monitoring Before and
During Charge Automatic Sleep Mode for Low-Power
z Consumption Available in SOP-8P Package
z RoHS Compliant and 100% Lead (Pb)-Free
Typical Application Circuit
VIN
Order Information
LP28056SPF
4
6
LP28056 - □ □ □
7
F: Pb-Free
10uF
Package Type
SP: SOP-8(P)
3
VIN
BATT
STAT2
ISET
5
2
STAT1
VSS
4.7uF
Rset
1K
PGND
9
Applications
—
—
—
—
Portable Media Players/MP3 players
Cellular and Smart mobile phone
PDA/DSC
Marking Information
Please see website www.lowpowersemi.com
LP28056.
Bluetooth Applications
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 1 of 9
BATTERY
Preliminary Datasheet
LP28056
Functional Pin Description
P a c k a g e Ty p e
Pin Configurations
NC
1
8
NC
7
STAT1
6
STAT2
5
BATT
LP28056
ISET
SOP-8(P)
2
9
VSS
3
VIN
4
PGND
Pi n Desc ript ion
PIN
PIN
Number
1,8
NC
DESCRIPTION
No Connector.
Charge Current Program, Charge Current Monitor and Shutdown Pin. The charge current is programmed
by connecting a 1% resistor(RPROG)to ground. When charging in constant-current mode, this pin servos to
2
Iset
3
VSS
VSS is the connection to system ground.
4
Vin
VIN is the input power source. Connect to a wall adapter.
5
BATT
6
STAT2
7
STAT1
1V. In all modes, the voltage on this pin can be used to measure the charge current using the following
formula.
BAT is the connection to the battery. Typically a 10µF Tantalum capacitor is needed for stability when
there is no battery attached. When a battery is attached, only a 0.1µF ceramic capacitor is required.
Open-Drain Charge Status Output. When the battery is charging, the STAT pin is pulled High by an
internal N-channel MOSFET. When the charge cycle is completed, the pin is pulled 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, the pin is pulled High.
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 2 of 9
Preliminary Datasheet
LP28056
Function Block Diagram
LP28056
Absolute Maximum Ratings
— Input Voltage to GND (VIN) ----------------------------------------------------------------------------- 2.6V to 8V
— BAT, ISET, STAT (VX) ---------------------------------------------------------------------- 0.3V to VIN+0.3V
— BAT Short-Circuit Duration ---------------------------------------------------------------------------- Continuous
— BAT Pin Current ------------------------------------------------------------------------------------------ 1500mA
— 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) -------------------------------------------------------------- 1.5W
—
Thermal Resistance (JA) --------------------------------------------------------------------------------- 46℃/W
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 3 of 9
Preliminary Datasheet
LP28056
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
ICC
VFLOAT
PARAMETER
CONDITIONS
MIN
2.65
Adapter/USB Voltage Range
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)
4.158
840
386
0
0°C ≤ TA ≤ 85°C, IBAT = 40mA
RISET = 1k, Current Mode
RISET = 2k, Current Mode
IBAT
BAT Pin Current
Standby Mode, VBAT = 4.2V
Shutdown Mode (RISET Not
Connected) Sleep Mode, VCC = 0V
ITRIKL
Trickle Charge Current
VBAT < VTRIKL, RISET = 2k (Note 5)
VTRIKL
Trickle Charge Threshold Voltage
RISET = 10k, VBAT Rising (Note 5)
VTRHYS
Trickle Charge Hysteresis Voltage
RISET = 10k (Note 5)
VUV
VUVHYS
VMSD
VASD
ITERM
VISET
ISTAT
VSTAT
ΔVRESTAT
TLIM
VCC Undervoltage Lockout Threshold From VCC Low to High
VCC Undervoltage Lockout Hysteresis
Manual Shutdown Threshold Voltage
VCC – VBAT Lockout Threshold
Voltage
ISET Pin Rising
ISET Pin Falling
VCC from Low to High
VCC from High to Low
C/10 Termination Current Threshold
RISET = 10k (Note 6)
RISET = 2k
ISET Pin Voltage
STAT Pin Weak Pull-Down Current
RISET = 10k, Current Mode
VSTAT = 5V
STAT Pin Output Low Voltage
ISTAT = 5mA
Recharge Battery Threshold Voltage VFLOAT - VRESTAT
RON
Junction Temperature in Constant Temperature Mode
Power FET “ON” Resistance (Between VCC and BAT)
tSS
Soft-Start Time
IISET
VIN OVP
20
2.8
60
3.7
150
1.15
0.9
70
5
0.085
0.085
0.9
8
100
ISET Pin Pull-Up Current
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
5.9
www.lowpowersemi.com
MAX UNITS
7
V
300
2000
200
500
25
4.2
880
44
-2.5
±1
±1
45
2.9
80
3.8
200
1.21
1.0
100
30
0.10
0.10
1.0
20
0.35
150
50
4.242
920
455
-6
±2
±2
70
3.0
110
3.95
300
1.30
1.1
140
50
0.115
0.115
1.1
35
0.6
200
120
600
100
3
IBAT = 0 to IBAT =850V/RISET
Over voltage protection
TYP.
5
6.2
uA
V
mA
uA
mA
V
mV
V
mV
V
V
mV
mV
mA/mA
mA/mA
V
uA
V
mV
°C
mΩ
uS
uA
6.5
Page 4 of 9
V
Preliminary Datasheet
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
LP28056
Page 5 of 9
Preliminary Datasheet
LP28056
Typical Operating Characteristics
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 6 of 9
Preliminary Datasheet
LP28056
Operation
The LP28056 is a single cell lithium-ion battery charger
using a constant-current/constant-voltage algorithm. It can
deliver up to 1200mA of charge current (using a good
thermal PCB layout) with a final float voltage accuracy of
±1%. The LP28056 includes an internal P-channel power
MOSFET and thermal regulation circuitry. No blocking
diode or external current sense resistor is required; thus, the
basic charger circuit requires only two external components.
Furthermore, the LP28056 is capable of operating from a
USB power source.
Normal Charge Cycle
A charge cycle begins when the voltage at the VCC pin rises
above the UVLO threshold level and a 1% ISET ram
resistor is connected from the ISET pin to ground or when a
battery is connected to the charger output. If the BAT pin is
less than 2.9V, the charger enters trickle charge mode. In
this mode, the LP28056 supplies approximately 1/10 the
ISET rammed charge current to bring the battery voltage up
to a safe level for full current charging. (Note: The
LP28056 does not include this trickle charge feature).
When the BAT pin voltage rises above 2.9V, the charger
enters constant-current mode, where the ISET rammed
charge current is supplied to the battery. When the BAT pin
approaches the final float voltage (4.2V), the LP28056
enters constant-voltage mode and the charge current begins
to decrease. When the charge current drops to 1/10 of the
ISET rammed value, the charge cycle ends.
ISET ramming Charge Current
The charge current is ISET rammed using a single resistor
from the ISET pin to ground. The battery charge current is
1000 times the current out of the ISET pin. The ISET ram
resistor and the charge current are calculated using the
following equations:
RSET=880V/ICHG，ICHG= 880V/RSET
The charge current out of the BAT pin can be determined at
any time by monitoring the ISET pin voltage using the
following equation:
IBAT= VSET x 880/RSET
voltage is reached. This condition is detected by using an
internal, filtered comparator to monitor the ISET pin. When
1
the ISET pin voltage falls below 100mV for longer than
tTERM (typically 1ms), charging is terminated. The charge
current is latched off and the LP28056 enters standby mode,
where the input supply current drops to 200µA. (Note: C/10
termination is disabled in trickle charging and thermal
limiting modes).
When charging, transient loads on the BAT pin can cause
the ISET pin to fall below 100mV for short periods of time
before the DC charge current has dropped to 1/10th the
ISET rammed value. The 1ms filter time (tTERM) on the
termination comparator ensures that transient loads of this
nature do not result in premature charge cycle termination.
Once the average charge current drops below 1/10th the
ISET rammed value, the LP28056 terminates the charge
cycle and ceases to provide any current through the BAT
pin. In this state, all loads on the BAT pin must be supplied
by the battery.
The LP28056 constantly monitors the BAT pin voltage in
standby mode. If this voltage drops below the 4.05V
recharge threshold (VRESTAT), another charge cycle begins
and current is once again supplied to the battery. To
manually restart a charge cycle when in standby mode, the
input voltage must be removed and reapplied, or the
charger must be shut down and restarted using the ISET pin.
Figure 1 shows the state diagram of a typical charge cycle.
Charge Status Indicator (STAT)
The charge status output has three different states: strong
pull-down (~10mA), weak pull-down (~20µA) and high
impedance. The strong pull-down state indicates that the
LP28056 is in a charge cycle. Once the charge cycle has
terminated, the pin state is determined by undervoltage
lockout conditions. A weak pull-down indicates that VCC
meets the UVLO conditions and the LP28056 is ready to
charge. High impedance indicates that the LP28056 is in
undervoltage lockout mode: either VCC is less than 100mV
above the BAT pin voltage or insufficient voltage is applied
to the VCC pin. A microprocessor can be used to distinguish
Charge Termination
between these three states—this method is discussed in the
Applications Information section.
A charge cycle is terminated when the charge current falls
to 1/10th the ISET rammed value after the final float
Thermal Limiting
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 7 of 9
Preliminary Datasheet
An internal thermal feedback loop reduces the ISET
rammed charge current if the die temperature attempts to
rise above a preset value of approximately 120°C. This
feature protects the LP28056 from excessive temperature
and allows the user to push the limits of the power handling
capability of a given circuit board without risk of damaging
the LP28056. The charge current can be set according to
typical (not worst-case) ambient temperature with the
assurance that the charger will automatically reduce the
current in worst-case conditions. TDFN power considerations are discussed further in the Applications Information section.
LP28056
The conditions that cause the LP28056 battery charger
to reduce charge current through thermal feedback can
be approximated by considering the total power
dissipated in the IC. For high charge currents, the
LP28056 power dissipation is approximately:
Where PD is the total power dissipated within the IC,
ADP is the input supply voltage, VBAT is the battery
voltage, IBAT is the charge current and PD_BUCK is the
power dissipation due to the regulator. PD_BUCK can be
calculated as:
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until VCC
rises above the undervoltage lockout threshold. The UVLO
circuit has a built-in hysteresis of 200mV. Furthermore, to
protect against reverse current in the power MOSFET, the
UVLO circuit keeps the charger in shutdown mode if VCC
falls to within 30mV of the battery voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown mode until VCC rises 100mV above the battery
voltage.
Where VOUTB is the regulated output of the switching
regulator, IOUTB is the regulator load and is the regulator
efficiency at that particular load.
It is not necessary to perform worst-case power
dissipation scenarios because the LP28056 will
automatically reduce the charge current to maintain the
die temperature at approximately 125°C. However, the
approximate ambient temperature at which the thermal
feedback begins to rotect the IC is:
Manual Shutdown
At any point in the charge cycle, the LP28056 can be put
into shutdown mode by removing RISET thus floating the
ISET pin. This reduces the battery drain current to less than
2µA and the supply current to less than 50µA. A new
charge cycle can be initiated by reconnecting the ISETram
resistor.
In manual shutdown, the STAT pin is in a weak pull-down
state as long as VCC is high enough to exceed the UVLO
conditions. The STAT pin is in a high impedance state if
the LP28056 is in undervoltage lockout mode: either VCC is
within 100mV of the BAT pin voltage or insufficient
voltage is applied to the VCC pin.
Automatic Recharge
Once the charge cycle is terminated, the LP28056 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.
T=
If there is more power dissipation due to the switching
regulator or the LDO, the thermal regulation will kick in
at a somewhat lower temperature than this. In the above
circumstances, the LP28056 can be used above 82.75°C,
but the charge current will be reduced from 250mA. The
approximate current at a given ambient temperature can
be calculated:
o
o
o
Note: 1V = 1J/C = 1W/A
Power Dissipation
LP28056 – 01 Ver. 1.1 Datasheet
Example: Consider the extreme case when an LP28056
is operating from a 6V supply providing 250mA to a 3V
Li-Ion battery, the switching regulator and the LDO are
off. The ambient temperature above which the LP28056
will begin to reduce the 250mA charge current is
approximately: (Correctly soldered to a 2500mm2
double-sided 1 oz. copper board, the LP28056 has a
thermal resistance of approximately 43°C/W.)
FEB.-2012
www.lowpowersemi.com
Page 8 of 9
Preliminary Datasheet
LP28056
Furthermore, the voltage at the ISET pin will change
proportionally with the charge current as discussed in
the ISET ramming Charge Current section.
Packaging Information
LP28056 – 01 Ver. 1.1 Datasheet
FEB.-2012
www.lowpowersemi.com
Page 9 of 9