LP3947 [NSC]
USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC; USB / AC适配器，单节锂离子电池充电器IC
| 型号： | LP3947 |
| 厂家： | 
National Semiconductor |
| 描述： | USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC |
| 文件： | 总14页 (文件大小：647K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
November 2004
LP3947
USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC
n Near-Depleted Battery Preconditioning
n Monitors Battery Temperature
The LP3947 is a complete charge management system that
n Built-In 5.6 hour timer
General Description
safely charges and maintains a Li-Ion battery from either
USB power source or AC adaptor. In USB mode, the LP3947
n Under Voltage and Over Voltage Lockout
n Charge Status Indicators
n Charge Current Monitor Analog Output
n LDO Mode Operation can source 1 Amp
n Continuous Over Current/Temperature Protection
supports charging in low power or high power mode. Alter-
natively, the LP3947 can take charge from AC adaptor. In
both USB and AC adaptor modes, charge current, battery
regulation voltage, and End of Charge (EOC) point can be
selected via I2C interface. The LP3947 can also operate on
default values that are pre-programmed in the factory. The
battery temperature is monitored continuously at the Ts pin
to safeguard against hazardous charging conditions. The
charger also has under-voltage and over-voltage protection
as well as an internal 5.6 hr timer to protect the battery. The
pass transistor and charge current sensing resistor are all
integrated inside the LP3947.
Key Specifications
n 1% Charger Voltage Accuracy Over 0˚C ≤ TJ ≤ 85˚C
n 4.3V to 6.0V Input Voltage Range
n 100 mA to 750 mA charge current range, in charger
mode
n 100mA to 500mA charge current range, in USB mode
n LLP Package Power Dissipation: 2.7W at TA = 25˚C
The LP3947 operates in four modes: pre-qualification, con-
stant current, constant voltage and maintenance modes.
There are two open drain outputs for status indication. An
internal amplifier readily converts the charge current into a
voltage. Also, the charger can operate in an LDO mode
providing a maximum of 1.2 Amp to the load.
Applications
n Cellular Phones
n PDAs
n Digital Cameras
n USB Powered Devices
n Programmable Current Sources
Features
n Supports USB Charging Scheme
n Integrated Pass Transistor
Typical Application Circuit
20111001
More Application Circuit can be found in the Application Note section.
© 2004 National Semiconductor Corporation
DS201110
www.national.com
Connection Diagrams and Package Mark Information
20111002
(Top View)
See NS Package Number SDA14B
Pin Description
Pin #
Name
EN
Description
1
Charger Enable Input. Internally pulled high to CHG-IN pin. A HIGH enables the charger and a
LOW disables the charger.
2
3
4
5
6
7
SCL
I2C serial Interface Clock input.
I2C serial Interface Data input/out.
SDA
BATT
VT
Battery supply input terminal. Must have 10 µF ceramic capacitor to GND
Regulated 2.78V output used for biasing the battery temperature monitoring thermistor.
Battery Voltage Sense connected to the positive terminal of the battery.
Select pin between AC adaptor and USB port. A LOW sets the LP3947 in USB port and a HIGH
sets it in the AC adaptor.
VBSENSE
MODE
8
9
Diff-Amp
Ts
Charge current monitoring differential amplifier output. Voltage output representation of the charge
current.
Multi function pin. Battery temperature monitoring input and LDO/Charger mode.
Pulling this pin to VT, or removing the thermistor by physically disconnecting the battery, sets the
device in LDO mode.
10
EOC
Active Low Open Drain Output. Active when USB port or AC adaptor is connected and battery is
fully charged. For more information, refer to “LED Charge Status Indicators” section.
Ground
11
12
GND
CHG
Active Low Open Drain Output. Active when USB port or AC adaptor is connected and battery is
being charged. For more information, refer to “LED Charge Status Indicators” section.
Control pin to switch between low power (100 mA) mode and high power (500 mA) mode in USB
mode. This pin is pulled high internally as default to set the USB in 100 mA mode. This pin has to
be externally pulled low to go into 500 mA mode.
13
14
ISEL
CHG-IN
Charger input from a regulated, current limited power source. Must have a 1 µF ceramic capacitor
to GND
Ordering Information
LP3947
Supplied as 1000 Units,
Tape and Reel
LP3947
Supplied as 4500 Units
Tape and Reel
Default
Options*
Package
Marking
LP3947ISD-09
LP3947ISDX-09
ICHG = 500 mA
VBATT = 4.1V
EOC = 0.1C
L00055B
LP3947ISD-51
LP3947ISDX-51
ICHG = 500 mA
VBATT = 4.2V
EOC = 0.1C
L00056B
*Other default options are available. Please contact National Semiconductor sales office/distributors for availability and specifications.
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2
LP3947 Functional Block Diagram
20111003
3
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Absolute Maximum Ratings (Notes 1,
2)
Operating Ratings (Notes 1, 2)
CHG-IN
0.3V to 6.5V
0V to 6V
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
EN, ISEL, MODE, SCL, SDA,
VT (Note 3)
Junction Temperature
Operating Temperature
Thermal Resistance θJA
Maximum Power Dissipation
(Note 6)
−40˚C to +125˚C
−40˚C to +85˚C
37˚C/W
CHG-IN
−0.3V to +6.5V
All pins except GND and CHG-IN
(Note 3)
−0.3V to +6V
150˚C
1.21W
Junction Temperature
Storage Temperature
Power Dissipation (Note 4)
ESD (Note 5)
−40˚C to +150˚C
1.89W
Human Body Model
Machine Model
2 kV
200V
Electrical Characteristics
Unless otherwise noted, VCHG-IN = 5V, VBATT = 4V, CCHG-IN = 1 µF, CBATT = 10 µF. Typical values and limits appearing in nor-
mal type apply for TJ = 25˚C. Limits appearing in boldface type apply over the entire junction temperature range for operation,
TJ = −40˚C to +85˚C. (Notes 7, 8, 9)
Limit
Symbol
Parameter
Conditions
Typ
Units
Min
Max
VCC SUPPLY
VCHG-IN
VUSB
Input Voltage Range
4.5
4.3
6
6
V
ICC
Quiescent Current
VCHG-IN ≤ 4V
2
20
µA
EOC = Low, adaptor connected,
VBATT = 4.1V
50
150
VOK-TSHD
Adaptor OK Trip Point (CHG-IN)
VCHG-IN –VBATT (Rising)
VCHG-IN –VBATT (Falling)
VCHG-IN (Rising)
60
50
mV
mV
V
VUVLO-TSHD Under Voltage Lock-Out Trip Point
VOVLO-TSHD Over Voltage Lock-Out Trip Point
3.95
3.75
5.9
5.7
160
20
3.6
3.4
4.3
4.1
VCHG-IN (Falling)
V
VCHG-IN (Rising)
V
VCHG-IN (Falling)
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
(Note 8)
˚C
BATTERY CHARGER
ICHG
Fast Charge Current Range
ISEL = High, In USB Mode
ISEL = Low, In USB Mode
In AC Adaptor Mode
100
500
mA
100
−20
−10
45
750
+20
+10
70
Fast Charge Current Accuracy
ICHARGE = 100 mA or 150 mA
ICHARGE ≥ 200 mA
mA
%
IPRE-CHG
IEOC
Pre-Charge Current
VBATT = 2V
mA
End of Charge Current Accuracy
100 mA to 450 mA, 0.1C EOC Only
(Note 10)
−10
+10
mA
%
500 mA to 750 mA, All EOC Points
−20
+20
VBATT
Battery Regulation Voltage (For 4.1V TJ = 0˚C to +85˚C
Cell)
Battery Regulation Voltage (For 4.2V TJ = 0˚C to +85˚C
4.1
4.1
4.1
4.2
4.059
4.038
4.158
4.137
4.141
4.162
4.242
4.263
TJ = −40˚C to +85˚C
V
V
Cell)
TJ = −40˚C to +85˚C
VCHG-Q
Full Charge Qualification Threshold
VBATT Rising, Transition from
Pre-Charge to Full Current
3.0
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4
Electrical Characteristics (Continued)
Unless otherwise noted, VCHG-IN = 5V, VBATT = 4V, CCHG-IN = 1 µF, CBATT = 10 µF. Typical values and limits appearing in nor-
mal type apply for TJ = 25˚C. Limits appearing in boldface type apply over the entire junction temperature range for operation,
TJ = −40˚C to +85˚C. (Notes 7, 8, 9)
Limit
Symbol
Parameter
Conditions
Typ
Units
Min
Max
BATTERY CHARGER
VBAT-RST
Restart Threshold Voltage
(For 4.1V Cell)
VBATT Falling, Transition from EOC,
to Pre-Qualification State
VBATT Falling, Transition from EOC,
to Pre-Qualification State
(Note 8)
3.9
3.77
3.86
4.02
4.12
V
Restart Threshold Voltage
(For 4.2V Cell)
4.00
120
RSENSE
Internal Current Sense Resistance
Internal Current Sense Resistor
Load Current
mΩ
1.2
A
ICHGMON
Diff-Amp Output
ICHG = 50 mA
0.583
0.663
1.790
5.625
5.625
100
ICHG = 100 mA
V
ICHG = 750 mA
tOUT
VOL
Charger Time Out
TJ = 0˚C to 85˚C
4.78
4.5
6.42
6.75
Hrs
mV
TJ = −40˚C to +85˚C
EOC, CHG Pins each at 9 mA
Low Level Output Voltage
TEMPERATURE SENSE COMPARATORS
VUTLO
VOTLO
Low Voltage Threshold
Voltage at Ts Pin, Rising
Voltage at Ts Pin, Falling
Voltage at Ts Pin, Rising
Voltage at Ts Pin, Falling
Voltage at Ts Pin, % of VT
2.427
2.369
1.470
1.390
97
V
V
High Voltage Threshold
VLDO
VT
LDO Mode Voltage Threshold
Voltage Output
%
V
2.787
LDO MODE (Ts = HIGH)
VOUT
Output Voltage Regulation
ILOAD = 50 mA
ILOAD = 750 mA
4.10
4.06
V
LOGIC LEVELS
VIL
VIH
IIL
Low Level Input Voltage
EN, ISEL, MODE
EN, ISEL, MODE
EN, ISEL = LOW
MODE = LOW
0.4
V
High Level Input Voltage
Input Current
2.0
−10
−5
V
+10
+5
µA
µA
µA
IIH
Input Current
EN, ISEL, MODE = HIGH
−5
+5
Electrical Characteristics, I2C Interface
Unless otherwise noted, VCHG-IN = VDD = 5V, VBATT = 4V. Typical values and limits appearing in normal type apply for TJ
=
25˚C. Limits appearing in boldface type apply over the entire junction temperature range for operation, TJ = −40˚C to +125˚C.
(Notes 7, 8, 9)
Limit
Symbol
VIL
Parameter
Conditions
SDA & SCL (Note 8)
Typ
Units
Min
0.4
Max
Low Level Input Voltage
High Level Input Voltage
Low Level Output Voltage
Schmitt Trigger Input Hysteresis
Clock Frequency
0.3 VDD
VDD +0.5
0.2 VDD
V
V
VIH
SDA & SCL (Note 8)
SDA & SCL (Note 8)
SDA & SCL (Note 8)
(Note 8)
0.7 VDD
0
VOL
V
VHYS
FCLK
tHOLD
0.1 VDD
V
400
kHz
Hold Time Repeated START
Condition
(Note 8)
0.6
µs
tCLK-LP
tCLK-HP
CLK Low Period
(Note 8)
(Note 8)
1.3
0.6
µs
µs
CLK High Period
5
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Electrical Characteristics, I2C Interface (Continued)
Unless otherwise noted, VCHG-IN = VDD = 5V, VBATT = 4V. Typical values and limits appearing in normal type apply for TJ
=
25˚C. Limits appearing in boldface type apply over the entire junction temperature range for operation, TJ = −40˚C to +125˚C.
(Notes 7, 8, 9)
Limit
Symbol
tSU
Parameter
Conditions
Typ
Units
Min
0.6
Max
Set-Up Time Repeated START
Condition
(Note 8)
µs
tDATA-HOLD Data Hold Time
(Note 8)
(Note 8)
(Note 8)
300
100
0.6
ns
ns
µs
tDATA-SU
tSU
Data Set-Up Time
Set-Up Time for STOP Condition
tTRANS
Maximum Pulse Width of Spikes that (Note 8)
must be Suppressed by the Input
50
ns
Filter of both DATA & CLK Signals.
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device
is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical
Characteristics tables.
Note 2: All voltages are with respect to the potential at the GND pin.
Note 3: Caution must be taken to avoid raising pins EN and V 0.3V higher than V
and raising pins ISEL, MODE, SCL and SDA 0.3V higher than V
.
BATT
T
CHG-IN
Note 4: The Absolute Maximum power dissipation depends on the ambient temperature and can be calculated using the formula
P = (TJ – TA)θJA
,
(1)
where T is the junction temperature, T is the ambient temperature, and θ is the junction-to-ambient thermal resistance. The 1.89W rating appearing under
J
A
JA
Absolute Maximum Ratings results from substituting the Absolute Maximum junction temperature, 150˚C, for T , 80˚C for T , and 37˚C/W for θ . More power can
J
A
JA
be dissipated safely at ambient temperatures below 80˚C. Less power can be dissipated safely at ambient temperatures above 80˚C. The Absolute Maximum power
dissipation can be increased by 27 mW for each degree below 80˚C, and it must be de-rated by 27 mW for each degree above 80˚C.
Note 5: The human-body model is used. The human-body model is 100 pF discharged through 1.5 kΩ.
Note 6: Like the Absolute Maximum power dissipation, the maximum power dissipation for operation depends on the ambient temperature. The 1.21W rating
appearing under Operating Ratings results from substituting the maximum junction temperature for operation, 125˚C, for T , 80˚C for T , and 37˚C/W for θ into
J
A
JA
(1) above. More power can be dissipated at ambient temperatures below 80˚C. Less power can be dissipated at ambient temperatures above 80˚C. The maximum
power dissipation for operation can be increased by 27 mW for each degree below 80˚C, and it must be de-rated by 27 mW for each degree above 80˚C.
Note 7: All limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production with T = 25˚C. All hot and cold limits are
J
guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
Note 8: Guaranteed by design.
Note 9: LP3947 is not intended as a Li-Ion battery protection device, any battery used in this application should have an adequate internal protection.
Note 10: The 10 mA limits apply to all charge currents from 100 mA to 450 mA, to 0.1C End Of Charge (EOC). The limits increase proportionally with higher EOC
points. For example, at 0.2C, the End Of Charge current accuracy becomes 20 mA.
20111004
FIGURE 1. Li-Ion Charging Profile
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6
VBATT voltage across the battery terminals. During this cycle,
the charge current, ICHG, continues to decrease with time
and when it drops below 0.1C (default value), the EOC
signal is activated indicating successful completion of the
charge cycle. The EOC current can be programmed to 0.1C,
0.15C, or 0.2C. The default value is 0.1C. After completing
the full charge cycle, the controller will start the maintenance
cycle where battery pack voltage is monitored continuously.
During the maintenance cycle, if the pack voltage drops 200
mV below the termination voltage, charge cycle will be initi-
ated providing that the wall adaptor is plugged in and is alive.
Application Notes
LP3947 CHARGER OPERATION
The LP3947 charge cycle is initiated with AC adaptor or USB
power source insertion. If the voltage on the CHG-IN pin
meets under-voltage (VUVLO-TSHD), over-voltage (VOVLO-
TSHD) requirements, and the Adaptor OK signal is detected,
then pre-qualification cycle begins (see Figure 1). In this
cycle, a safe current level, less than 70mA, is pumped into
the battery while the voltage across the battery terminals is
measured. Once this voltage exceeds 3.0V, the controller
will initiate constant current fast charge cycle. If the CHG-IN
pin is connected to an AC adaptor, the default charge current
is 500 mA and I2C interface can be used to program this
parameter. If the CHG-IN pin is connected to the USB port,
constant current cycle will start with a default of 100 mA.
During this cycle, the 5.6 hr safety timer starts counting.
Charging terminates when the battery temperature is out of
range. For more explanation, please refer to “Ts Pin” section.
The LP3947 with I2C interface allows maximum flexibility in
selecting the charge current, battery regulation voltage and
EOC current. The LP3947 operates in default mode during
power up. See the “I2C Interface” section for more detail.
When charging source comes from the USB port, charging
starts with 100 mA (low power mode, ISEL = high). The USB
controller can set the ISEL pin low to charge the battery at
500 mA. A simple external circuit selects between an AC
adaptor or the USB port. The circuit is designed with priority
given to the AC adaptor.
If the 5.6 hr safety timers times out during constant current
cycle, charging is terminated. As the battery is charged
during constant current mode, the voltage across pack ter-
minal increases until it reaches 4.2V (or 4.1V). As soon as
pack terminal reaches 4.2V (or 4.1V), the controller starts
operating in constant voltage mode by applying regulated
20111006
FIGURE 2. LP3947 with External Switch
7
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Application Notes (Continued)
20111007
FIGURE 3. LP3947 Charger Flow Chart
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Application Notes (Continued)
CHARGE CURRENT SELECTION IN CONSTANT
CURRENT MODE
to set the charge current in the LP3947. In the USB mode,
the LP3947 will initially charge with 100 mA (ISEL = high). By
setting the ISEL pin low, charge current can be programmed
to 500 mA. In addition, with ISEL = low, the charge current
can be programmed to different values via the I2C interface.
In the AC adaptor mode, the LP3947 is designed to provide
a charge current ranging from 100 mA to 750 mA, in steps of
50 mA, to support batteries with different capacity ratings.
The default value is 500 mA. No external resistor is required
TABLE 1. Charge Current Selection in AC Adaptor/USB Mode
MODE Pin
AC Adaptor Mode HIGH
ISEL Pin
HIGH
Functions
ISEL polarity is irrelevant. Default 500 mA charge current. Can be
reprogrammed via I2C.
HIGH
LOW
LOW
LOW
USB Mode
HIGH
100 mA charge current
Default 500 mA charge current. Can be reprogrammed via I2C.
LOW
BATTERY VOLTAGE SELECTION
CHARGE CURRENT SENSE DIFFERENTIAL AMPLIFIER
The battery voltage regulation can be set to 4.1V or 4.2V by
default. Please refer to the Ordering Information table for
more detail.
The charge current is monitored across the internal 120 mΩ
current sense resistor. The differential amplifier provides the
analog representation of the charge current. Charge current
can be calculated using the following equation:
END OF CHARGE (EOC) CURRENT SELECTION
The EOC thresholds can be programmed to 0.1C, 0.15C or
0.2C in the LP3947. The default value is 0.1C, which pro-
vides the highest energy storage, but at the expense of
longer charging time. On the other hand, 0.2C takes the
least amount of charging time, but yields the least energy
storage.
Where voltage at Diff Amp output (VDIFF) is in volt, and
charge current (ICHG) is in amps.
20111009
FIGURE 4. Charge Current Monitoring Circuit (Diff-Amp)
Monitoring the Diff Amp output during constant voltage cycle
can provide an accurate indication of the battery charge
status and time remaining to EOC. This feature is particularly
useful during constant voltage mode. The current sense
circuit is operational in the LDO mode as well. It can be used
to monitor the system current consumption during testing.
LED CHARGE STATUS INDICATORS
The LP3947 is equipped with two open drain outputs to drive
a green LED and a red LED. These two LEDs work together
in combinations to indicate charge status or fault conditions.
Table 2 shows all the conditions.
9
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Application Notes (Continued)
TABLE 2. LED Indicator Summary
RED LED
GREEN LED
(EOC)
OFF
(CHG)
OFF
ON
Charger Off
Charging Li Ion Battery*
OFF
Maintenance Mode
OFF
OFF
OFF
OFF
ON
ON
Charging Li Ion Battery after Passing Maintenance Mode
EN Pin = LOW
ON
ON
LDO Mode
OFF
5.6 Hr Safety Timer Flag/Battery Temperature Violation
ON
* Charging Li Ion battery for the first time after V
insertion.
CHG-IN
Ts PIN
Voltage on the Ts Pin
Charger Status
The LP3947 continuously monitors the battery temperature
by measuring the voltage between the Ts pin and ground.
Charging stops if the battery temperature is outside the
permitted temperature range set by the battery’s internal
thermistor RT and the external bias resistor RS. A 1% preci-
sion resistor should be used for RS. A curve 2 type thermistor
is recommended for RT. The voltage across RT is propor-
tional to the battery temperature. If the battery temperature is
outside of the range during the charge cycle, the LP3947 will
suspend charging. As an example, for a temperature range
of 0˚C to 50˚C, a 10kΩ for the thermistor and a 4.1kΩ for Rs
should be used. When battery temperature returns to the
permitted range, charging resumes from the beginning of the
flow chart and the 5.6 hr safety timer is reset. Refer to Figure
3. LP3947 Charger Flow Chart for more information.
<
2.427v ≤ Ts 2.7V
Charger Off
0V ≤ Ts ≤ 1.39V
<
<
1.39V Ts 2.427V
Charger On
LDO MODE
The charger is in the LDO mode when the Ts pin is left
floating. This mode of operation is used primarily during
system level testing of the handset to eliminate the need for
battery insertion. CAUTION: battery may be damaged if
device is operating in LDO mode with battery connected.
The internal power FET provides up to 1.2 amp of current at
BATT pin in this mode. The LDO output is set to 4.1V. When
operating at higher output currents, care must be taken not
to exceed the package power dissipation rating. See “Ther-
mal Performance of LLP Package” section for more detail.
In absence of the thermistor, Ts pin will be pulled high to VT
and the LP3947 goes into LDO mode. In this mode, the
internal power FET provides up to 1.2 amp of current at the
BATT pin. The LDO output is set to 4.1V or 4.2V, depending
on the programmed battery regulation voltage. When oper-
ating at higher output currents, care must be taken not to
exceed the package power dissipation rating. See “Thermal
Performance of LLP Package” section for more detail.
EN PIN
The Enable pin is used to enable/disable the charger, in both
the charger mode and the LDO mode, see Figures 5, 6. The
enable pin is internally pulled HIGH to the CHG-IN pin. When
the charger is disabled, it draws less than 4 µA of current.
Charger Status in Relation to Ts Voltage
Voltage on the Ts Pin
Charger Status
Ts ≥ 2.7V
LDO Mode
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Application Notes (Continued)
20111010
<
<
FIGURE 5. Power Up Timing Diagram in Charger Mode (1.39V Ts 2.427V)
20111011
FIGURE 6. Power Up Timing Diagram in LDO Mode (Ts ≥ 2.7V)
MODE PIN
mode. It will turn the charger off when the 5.6 hr timer is up
while the charger is still in constant current mode. In this
case, both LEDs will turn on, indicating a fault condition.
The mode pin toggles the LP3947 between the AC adaptor
mode and the USB mode. When CHG-IN is connected to a
USB port, this pin must be set low. When CHG-IN is con-
nected to an AC adaptor, this pin must be tied high to either
the BATT pin or to the wall adaptor input. Caution: MODE pin
should never be tied to CHG-IN pin directly, as it will turn on
an internal diode.
When the battery temperature is outside the specified tem-
perature range, the 5.6 hr safety timer will reset upon recov-
ery of the battery temperature.
I2C INTERFACE
I2C interface is used in the LP3947 to program various
parameters as shown in Table 3. The LP3947 operates on
default settings following power up. Once programmed, the
LP3947 retains the register data as long as the battery
voltage is above 2.85V.
5.6 HR SAFETY TIMER IN CHARGER MODE
The LP3947 has a built-in 5.6 hr back up safety timer to
prevent over-charging a Li Ion battery. The 5.6 hr timer starts
counting when the charger enters the constant current
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Application Notes (Continued)
TABLE 3. LP3947 Serial Port Communication address code 7h’47
LP3947 Control and Data Codes
Addrs
Register
Charger
7
6
5
4
3
AC Adaptor
Charge
Current
Code 3
(1)
2
AC Adaptor
Charge
Current
Code 2
(0)
1
AC Adaptor
Charge
Current
Code 1
(0)
0
8'h00
Batt Voltage
(0) = 4.1V
1 = 4.2V
AC Adaptor
Charge
Current
Code 0
(0)
Register -1
8'h01
8'h02
Charger
EOC
(Green LED)
R/O
Charging
(Red LED)
R/O
EOC
EOC
Register -2
SEL-1
(0)
SEL-0
(1)
Charger
USB
USB
USB
USB
Charge
Current
Code 0
(0)
Register -3
Charge
Current
Code 3
(1)
Charge
Current
Code 2
(0)
Charge
Current
Code 1
(0)
Numbers in parentheses indicate default setting. “0” bit is set to low state, and “1” bit is set to high state. R/O –Read Only, All other bits are Read and Write.
TABLE 4. Charger Current and EOC Current Programming Code
Charger Current
Selection Code ISET (mA)
End of Charge Current
Selection Code
Data Code
4h'00
4h'01
4h'02
4h'03
4h'04
4h'05
4h'06
4h'07
4h'08
4h'09
4h'0A
4h'0B
4h'0C
4h'0D
100
150
200
250
300
350
400
450
500
550
600
650
700
750
0.1C
0.15C
0.2C
20111012
w = write (sda = “0”)
r = read (sda = “1”)
ack = acknowledge (sda pulled low by either master or slave)
Nack = No Acknowledge
rs = repeated start
FIGURE 7. LP3947 (Slave) Register Write
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12
Application Notes (Continued)
20111013
w = write (sda = “0”)
r = read (sda = “1”)
ack = acknowledge (sda pulled low by either master or slave)
Nack = No Acknowledge
rs = repeated start
FIGURE 8. LP3947 (Slave) Register Read
THERMAL PERFORMANCE OF LLP PACKAGE
charged, then 740 mA of ICHG can safely charge the battery.
More power can be dissipated at ambient temperatures
below 70˚C. Less power can be dissipated at ambient tem-
peratures above 70˚C. The maximum power dissipation for
operation can be increased by 27 mW for each degree below
70˚C, and it must be de-rated by 27 mW for each degree
above 70˚C.
The LP3947 is a monolithic device with an integrated pass
transistor. To enhance the power dissipation performance,
the Leadless Lead frame Package, or LLP, is used. The LLP
package is designed for improved thermal performance be-
cause of the exposed die attach pad at the bottom center of
the package. It brings advantage to thermal performance by
creating a very direct path for thermal dissipation. Compared
to the traditional leaded packages where the die attach pad
is embedded inside the mold compound, the LLP reduces a
layer of thermal path.
LAYOUT CONSIDERATION
The LP3947 has an exposed die attach pad located at the
bottom center of the LLP package. It is imperative to create
a thermal land on the PCB board when designing a PCB
layout for the LLP package. The thermal land helps to con-
duct heat away from the die, and the land should be the
same dimension as the exposed pad on the bottom of the
LLP (1:1 ratio). In addition, thermal vias should be added
inside the thermal land to conduct more heat away from the
surface of the PCB to the ground plane. Typical pitch and
outer diameter for these thermal vias are 1.27 mm and 0.33
mm respectively. Typical copper via barrel plating is 1oz
although thicker copper may be used to improve thermal
performance. The LP3947 bottom pad is connected to
ground. Therefore, the thermal land and vias on the PCB
board need to be connected to ground.
The thermal advantage of the LLP package is fully realized
only when the exposed die attach pad is soldered down to a
thermal land on the PCB board and thermal vias are planted
underneath the thermal land. Based on a LLP thermal mea-
surement, junction to ambient thermal resistance (θJA) can
be improved by as much as two times if a LLP is soldered on
the board with thermal land and thermal vias than if not.
An example of how to calculate for LLP thermal performance
is shown below:
For more information on board layout techniques, refer to
Application Note 1187 “Leadless Leadframe Package
(LLP).” The application note also discusses package han-
dling, solder stencil, and assembly.
By substituting 37˚C/W for θJA, 125˚C for TJ and 70˚C for TA,
the maximum power dissipation allowed from the chip is
1.48W. If VCHG-IN is at 5.0V and a 3.0V battery is being
13
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Physical Dimensions inches (millimeters) unless otherwise noted
NS Package Number SDA14B
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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