BL4054

BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
FEATURES
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DESCRIPTION
Programmable Charge Current Up to
800mA
No MOSFET, Sense Resistor or Blocking
Diode Required
Preset 4.2V Charge Voltage with ±1%
Accuracy
Charge Current Monitor Output for Gas
Gauging
Thermal Regulation Maximizes Charge
Rate Without Risk of Overheating
Charges Single Cell Li-Ion Batteries Directly from USB Port
Over-Voltage Protect
Automatic Recharge
Charge Status Output Pin
C/10 Charge Termination
25μA Supply Current in Shutdown
2.9V Trickle Charge Threshold
Soft-Start Limits Inrush Current
Available in 5-Lead SOT-23 Package
The BL4054 is a complete constant-current /
constant voltage linear charger for single cell
Lithium-Ion batteries. 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 BL4054
automatically terminates the charge cycle
when the charge current drops to 1/10 the
programmed value after the final float voltage
is reached.
When the input supply (wall adapter or USB
supply) is removed, the BL4054 automatically
enters a low current state, dropping the
battery drain current to less than 2μΑ. The
BL4054 can be put into shutdown mode,
reducing the supply current to 25μA.
APPLICATIONS
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Cellular and Smart Phones
Charging Docks and Cradles
Blue Tooth Applications
PDAs
MP3 Players
Other features include charge current monitor,
under-voltage lockout, automatic recharge
and a status pin to indicate charge termination and the presence of an input voltage.
ORDERING INFORMATION
TYPICAL APPLICATION
VCC
4.5V TO 6.5V
BL4054 – XX X X XXX
Package:
TRN:TSOT23-5
RN:SOT23-5
1μF
Features:
P: Standard(default, lead free)
C: Customized
Trickle Charge
T: Trickle Charge
N: No Trickle Charge
VCC
BAT
600mA
BL4054
4.2V
Li-Ion
Battery
PROG
GND
Float Voltage
42……4.2V
43……4.3V
44……4.4V
1.65k
600mA Application Circuit
PPMIC BU
-1-
www.belling.com.cn
BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Absolute Maximum Rating (Note 1)
Input Supply Voltage (VCC)
PROG Voltage
BAT Voltage
CHRGb
BAT Short-Circuit Duration
BAT Pin Current
-0.3V to +10V
-0.3V to +VCC
-0.3V to 7V
-0.3V to 10V
Continuous
800mA
PROG Pin Current
Maximum Junction Temperature
Operating Temperature Range(Note2)
Storage Temperature Range
Lead Temperature (Soldering, 10s)
800μA
125°C
-40°C to 85°C
-65°C to 125°C
300°C
Package Information
TSOT23-5
TOP VIEW
1
GND
2
BAT
3
5
PROG
4
VCC
MARKING
Part Number
CHRGb
Top Mark
BL4054-4.2
XVYM
BL4054-4.3
XVYM
BL4054-4.4
XVYM
Temp Range
(Note3)
-40°C to +85°C
Thermal Resistance (Note 4)
Package
TSOT23-5
ӨJA
220°C/W
ӨJC
110°C/W
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: The BL4054 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: X:Product Code V:Voltage Code Y:Year M:Month
Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
PPMIC BU
-2-
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Pin Description
PPMIC BU
PIN
NAME
1
CHRGb
2
GND
3
BAT
4
VCC
5
PROG
FUNCTION
Open-Drain Charge Status Output. When the battery is
charging, the CHRGb pin is pulled low by an internal Nchannel MOSFET. When the charge cycle is completed, a
weak pull-down of approximately 20μA is connected to the
CHRGb pin, indicating an “AC present” condition. When the
BL4054 detects an under-voltage lockout condition, CHRGb is
forced high impedance.
Ground
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.
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 BL4054 enters shutdown mode,
dropping IBAT to less than 2μA.
Charge Current Program, Charge Current Monitor and
Shutdown Pin. The charge current is Programmed by
connecting a 1% resistor, RPROG, from this pin 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.
-3-
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Block Diagram
120oC
TDIE
VCC
+
4
TA
1x
1000x
7.0V
BAT
5μΑ
3
+
-
+
MA
R1
-
OVP
-
-
+
OV_SHDN
SHDN
+
VA
CA
C1
R2
REF
1.21V
+
R3
1V
R4
1
+
0.1V
-
R5
C2
CHRGb
STANDBY
C3
+
-
TO
BAT
VCC
2.9V
5
PPMIC BU
3μΑ
-4-
PROG
GND
RPROG
2
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Electrical Characteristics (Note 4)
(VCC = 5V, TA = 25°C, unless otherwise noted.)
Symbol
Parameter
Conditions
ISPLYCHRG
Charge Mode Supply Current (Note5)
RPROG=2kΩ
RPROG =10kΩ
IBATCHRG
Charge Mode Battery Current
RPROG =2kΩ
RPROG =10kΩ
465mA
93mA
500mA
100mA
2000μA
2000μA
535mA
107mA
VPROGCHRG
PROG Pin Voltage
RPROG =2kΩ
RPROG =10kΩ
0.93V
0.93V
1V
1V
1.07V
1.07V
ISPLYSTBY
Standby Mode Supply Current
100μA
500μA
IBATSTBY
Standby Mode Battery Current
-2.5μA
-6μA
ISPLYMSD
Manual Shutdown Mode Supply Current
IBATMSD
Manual Shutdown Mode Battery Current
-2μA
VPROGCLMP
PROG Pin Clamp Voltage
2V
ISPLYASD
Automatic Shutdown Mode Supply Current
IBATASD
Automatic Shutdown Mode Battery Current
ISPLYUVLO
UVLO Mode Supply Current
IBATUVLO
UVLO Mode Battery Current
-2μA
2μA
IBATSLEEP
Sleep Mode Battery Current
-1μA
1μA
VFLOAT
Float Voltage
4.158V
4.2V
4.242V
ITRIKL
Trickle Charge Current
20mA
5mA
50mA
10mA
70mA
15mA
VTRIKL
Trickle Charge Threshold
2.8V
2.9V
3V
VTRIKL, HYS
Trickle Charge Hysteresis
60mV
100mV
150mV
VUVLO
UVLO Threshold
3.7V
3.9V
4.1V
VUVLO, HYS
UVLO Hysteresis
150mV
200mV
300mV
VOVP
Input Over-Voltage Protect Threshold
6.8V
7V
7.2V
VOVP, HYS
Input Over-Voltage Protect Hysteresis
PPMIC BU
Typ
300μA
0
Max
90μA
-2μA
RPROG =2kΩ
RPROG =10kΩ
-5-
Min
0
2μA
3V
25μA
50μA
0
2μA
25μA
50μA
200mV
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
VMSD, RISE
Manual Shutdown Threshold, PROG rising
1.15V
1.21V
1.3V
VMSD, FALL
Manual Shutdown Threshold, PROG falling
0.95V
1.0V
1.05V
VASD, RISE
Automatic Shutdown Threshold, BAT rising
5mV
30mV
50mV
VASD, FALL
Automatic Shutdown Threshold, BAT falling
70mV
100mV
140mV
ITERM
C/10 Termination Current Threshold
85mV
100mV
115mV
VRECHRG
Auto Recharge Battery Voltage
4V
4.05V
4.1V
ICHRGb
CHRGb Pin Weak Pull-down Current
8μA
20μA
35μA
VCHRGb
CHRGb Pin Output Low Voltage
0.35V
0.6V
TLIM
Junction Temperature In Constant
Temperature Mode
120°C
RON
Power FET ON Resistance
600mΩ
TSS
Soft-Start Time
TRECHRG
Recharge Comparator Filter Time
0.75ms
2ms
4.5ms
TTERM
Termination Comparator Filter Time
0.4ms
1ms
2.5ms
IPROG
PROG Pin Pull-up Current
RPROG =2kΩ
50μs
3μA
Note 4: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
Note 5: Supply current includes PROG pin current (approximately 100μA) but does not include any current delivered to the battery
through the BAT pin (approximately 100mA).
Typical Performance Characteristics
PROG Pin Voltage vs
Temperature
PROG Pin Voltage vs Supply
Voltage (Constant Current Mode)
VCC=5V
VBAT=4V
TA=25°C
RPROG=10K
1.0175
1.0150
VCC=5V
VBAT=4V
RPROG=10K
500
IBAT(mA)
1.0125
300
1.0100
1.000
1.0075
200
1.0050
0.995
100
1.0025
0.990
4.0
VCC=5V
TA=25°C
RPROG=2K
400
VPROG(V)
VPROG(V)
600
1.0200
1.010
1.005
Charge Current vs
PROG Pin Voltage
4.5
5.0
5.5
VCC(V)
PPMIC BU
6.0
6.5
7.0
1.0000
-50
-25
0
25
50
TEMPERATURE(°C)
-6-
75
100
0
0.00
0.25
0.50
0.75
1.00
1.25
VPROG(V)
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Typical Performance Characteristics
PROG Pin Pull-Up Current vs
Temperature and Supply Voltage
PROG Pin Current vs PROG Pin
Voltage (Clamp Current)
PROG Pin Current vs PROG Pin
Voltage (Pull-Up Current)
4.5
0
4.0
VBAT=4.3V
VPROG=0V
4.2
3.5
-50
3.0
-100
IPROG(μΑ)
IPROG(μA)
3.9
3.6
IPROG(μΑ)
2.5
-150
2.0
VCC=4.2V
VCC=6.5V
1.5
3.3
-200
VCC=5V
VBAT=4.3V
TA=25°C
1.0
3.0
0.5
2.7
-50
-25
0
25
50
75
100
125
TEMPERATURE(°C)
0.0
2.0
2.2
2.3
2.4
2.5
2.6
4.17
4.15
200
300
400
500
600
4.210
4.205
VFLOAT(V)
VFLOAT(V)
4.19
100
4.200
4.190
4.190
4.185
-50
-25
0
25
50
TEMPERATURE(°C)
75
100
40
35
38
20
15
5
1
PPMIC BU
2
3
4
VCHRGb(V)
5
6
7
6.5
7.0
CHRGb Pin I-V Curve
(Weak Pull-Down State)
15
28
20
-50
6.0
20
30
22
0
5.5
25
32
24
5.0
30
34
26
VCC=5V
VBAT=4V
TA=25°C
4.5
ICHRGb(μA)
ICHRGb(mA)
ICHRGb(mA)
25
5.5
VCC(V)
36
30
5.0
TA=25°C
RPROG=10K
4.185
4.0
CHRGb Pin Current vs Temperature
(Strong Pull-Down State)
40
4.5
4.200
4.195
CHRGb Pin I-V Curve
(Strong Pull-Down State)
4.0
4.205
4.195
IBAT(mA)
10
3.5
4.215
VCC=5V
RPROG=10K
4.210
4.21
0
3.0
Regulated Output (Float) Voltage
vs Supply Voltage
4.215
VCC=5V
TA=25°C
RPROG=1.25K
4.23
2.5
VPROG(V)
Regulated Output (Float) Voltage
vs Temperature
4.25
0
-300
2.0
VPROG(V)
Regulated Output (Float) Voltage
vs Charge Current
VFLOAT(V)
2.1
VCC=5V
VBAT=4.3V
TA=25°C
-250
10
VCC=5V
VBAT=4V
VCHRGb=1V
VCC=5V
VBAT=4.3V
TA=25°C
5
0
-25
0
25
50
75
TEMPERATURE(°C)
-7-
100
125
0
1
2
3
4
5
6
7
VCHRGb(V)
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Typical Performance Characteristics
CHRGb Pin Current vs Temperature
(Weak Pull-Down State)
36
60
60
VCC=5V
VBAT=4.3V
VCHRGb=5V
33
30
RPROG=2K
50
40
VCC=5V
VBAT=2.5V
30
24
ITRIKL(mA)
27
20
10
18
VBAT=2.5V
TA=25°C
30
20
21
RPROG=2K
50
40
ITRIKL(mA)
ICHRGb(μΑ)
Trickle Charge Current vs
Supply Voltage
Trickle Charge Current
vs Temperature
10
RPROG=10K
15
-50
-25
0
25
50
75
100
0
-50
125
TEMPERATURE(°C)
Trickle Charge Threshold vs
Temperature
0
25
50
RPROG=10K
75
TEMPERATURE(°C)
100
0
4.0
125
4.5
5.0
5.5
6.0
6.5
7.0
VCC(V)
Charge Current vs Battery Voltage
3.000
Charge Current vs Supply Voltage
600
600
500
500
400
400
RPROG=2K
VCC=5V
RPROG=10K
2.975
-25
2.925
IBAT(mA)
VTRIKL(V)
IBAT(mA)
2.950
300
2.900
2.875
200
200
VCC=5V
RPROG=2K
TA=25°C
2.850
100
2.825
2.800
-50
-25
0
25
50
75
100
0
2.7
125
TEMPERATURE(°C)
Charge Current vs Ambient
Temperature
3.0
3.3
3.6
VBAT(V)
100
RPROG=10K
3.9
4.2
0
4.0
4.5
4.11
700
500
VCC=5V
4.09
RPROG=10K
650
4.07
VRECHRG(V)
IBAT(mA)
300
RDS(ON)(mΩ)
600
400
VCC=5V
VBAT=4V
4.03
100
4.01
PPMIC BU
0
25
50
75
100 125 150
TEMPERATURE(°C)
3.99
-50
5.5
VCC(V)
6.0
6.5
7.0
VCC=4.2V
IBAT=100mA
RPROG=2K
500
450
400
RPROG=10K
0
-50 -25
5.0
550
4.05
200
4.5
Power FET "ON" Resistance
vs Temperature
Recharge Voltage Threshold
vs Temperature
600
RPROG=2K
VBAT=4V
TA=25°C
300
-25
0
25
50
75
TEMPERATURE(°C)
-8-
100
125
350
-50
-25
0
25
50
75
TEMPERATURE(°C)
100
125
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Operation
The BL4054 is a single cell Lithium-Ion battery
charger using a constant-current / constantvoltage algorithm. It can deliver up to 800mA
of charge current (using a good thermal PCB
layout) with a final float voltage accuracy of
±1%. The BL4054 includes an internal Pchannel 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 BL4054 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% program resistor is connected from
the PROG 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 BL4054
supplies approximately 1/10 the programmed
charge current to bring the battery voltage up
to a safe level for full current charging.
resistor and the charge current are calculated
using the following equations:
1000V
1000V
R PROG =
I CHG =
I CHG
R PROG
The charge current out of the BAT pin can be
determined at any time by monitoring the
PROG pin voltage using the following
equation:
V
I BAT = PROG • 1000
R PROG
Charge Termination
A charge cycle is terminated when the charge
current falls to 1/10th the programmed value
after the final float voltage is reached. This
condition is detected by using an internal,
filtered comparator to monitor the PROG pin.
When the PROG pin voltage falls below
100mV for longer than TTERM (typically 1ms),
charging is terminated. The charge current is
latched off and the BL4054 enters standby
mode, where the input supply current drops to
100μA. (Note: C/10 termination is disabled in
trickle charging mode).
Programming Charge Current
When charging, transient loads on the BAT
pin can cause the PROG pin to fall below
100mV for short periods of time before the DC
charge current has dropped to 1/10th the
programmed 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 programmed value, the BL4054 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 charge current is programmed using a
single resistor from the PROG pin to ground.
The battery charge current is 1000 times the
current out of the PROG pin. The program
The BL4054 constantly monitors the BAT pin
voltage in standby mode. If this voltage drops
below the 4.05V recharge threshold (VRECHRG),
another charge cycle begins and current is
When the BAT pin voltage rises above 2.9V,
the charger enters constant-current mode,
where the programmed charge current is
supplied to the battery. When the BAT pin
approaches the final float voltage (4.2V), the
BL4054 enters constant-voltage mode and the
charge current begins to decrease. When the
charge current drops to 1/10 of the programmmed value, the charge cycle ends.
PPMIC BU
-9-
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
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 PROG
pin. Figure 1 shows the state diagram of a
typical charge cycle.
POWER ON
PROG
RECONNECTED
OR
UVLO CONDITION
STOPS
SHUTDOWN MODE
ICC DROPS TO <25μA
CHRGb:Hi-Z IN UVLO
WEAK PULL-DOWN
OTHERWISE
PROG FLOATED
OR
UVLO CONDITION
BAT < 2.9V
TRICKLE CHARGE
MODE
1/10TH FULL CURRENT
CHRGb:STRONG
PULL-DOWN
BAT > 2.9V
PROG < 100mV
STANDBY MODE
NO CHARGE CURRENT
CHRGb:WEAK
PULL-DOWN
Over-Voltage Protect
2.9V < BAT < 4.05V
Figure1. State Diagram of a Typical Charge Cycle
Charge Status Indicator (CHRGb)
The charge status output has three different
states: strong pull-down (~10mA), weak pulldown (~20μA) and high impedance. The
strong pull-down state indicates that the
BL4054 is in a charge cycle. Once the charge
cycle has terminated, the pin state is determined by under-voltage lockout conditions. A
weak pull-down indicates that VCC meets the
UVLO conditions and the BL4054 is ready to
charge. High impedance indicates that the
BL4054 is in under-voltage 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 between these three states—the
application circuit of this method is shown in
the Typical Applications section.
PPMIC BU
At any point in the charge cycle, the BL4054
can be put into shutdown mode by removing
RPROG thus floating the PROG 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 program resistor.
In manual shutdown, the CHRGb pin is in a
weak pull-down state as long as VCC is high
enough to exceed the UVLO conditions. The
CHRGb pin is in a high impedance state if the
BL4054 is in under-voltage lockout mode:
either VCC is within 100mV of the BAT pin
voltage or insufficient voltage is applied to the
VCC pin.
BAT > 2.9V
CHARGE MODE
FULL CURRENT
CHRGb:STRONG
PULL-DOWN
Manual Shutdown
The BL4054 has an internal Over-Voltage
Protect comparator, once the input voltage
VCC rises above 7V (VOVP), this comparator will
shut down the chip. This feature can pre-vent
the BL4054 from the over-voltage stress due
to the input transient at hot plug in. In this
state, the CHRGb pin will be high impedance.
Once the VCC falls back to safe range (VOVP VOVP, HYS), normal operation continues.
Automatic Recharge
Once the charge cycle is terminated, the
BL4054 continuously monitors the voltage on
the BAT pin using a comparator with a 2ms
filter time (TRECHRG). 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. CHRGb output enters
a strong pull-down state during recharge
cycles.
- 10 -
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BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Applications Information
Stability Considerations
The constant-voltage mode feedback loop is
stable without an output capacitor provided a
battery is connected to the charger output.
With no battery present, an output capacitor is
recommended to reduce ripple voltage. When
using high value, low ESR ceramic capacitors,
it is recommended to add a 1Ω resistor in
series with the capacitor. No series resistor is
needed if tantalum capacitors are used.
In constant-current mode, the PROG pin is in
the feedback loop, not the battery. The
constant-current mode stability is affected by
the impedance at the PROG pin. With no
additional capacitance on the PROG pin, the
charger is stable with program resistor values
as high as 20k. However, additional capacitance on this node reduces the maximum
allowed program resistor thus it should be
avoided.
Average, rather than instantaneous, charge
current may be of interest to the user. For
example, if a switching power supply operating in low current mode is connected in
parallel with the battery, the average current
being pulled out of the BAT pin is typically of
more interest than the instantaneous current
pulses. In such a case, a simple RC filter can
be used on the PROG pin to measure the
average battery current as shown in Figure 2.
A 10k resistor has been added between the
PROG pin and the filter capacitor to ensure
stability.
Thermal Limiting
An internal thermal feedback loop reduces the
programmed charge current if the die temperature attempts to rise above a preset value of
approximately 120°C. This feature protects the
PPMIC BU
BL4054 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 BL4054. 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.
10k
CHARGE
CURRENT
MONITOR
CIRCUITRY
PROG
BL4054
RPROG
CFILTER
GND
Figure 2. Isolating Capacitive Load on PROG Pin
Power Dissipation
The conditions that cause the BL4054 to
reduce charge current through thermal feedback can be approximated by considering the
power dissipated in the IC. Nearly all of this
power dissipation is generated by the internal
MOSFET—this is calculated to be approximately:
PD = (VCC − VBAT ) • I BAT
where PD is the power dissipated, VCC is the
input supply voltage, VBAT is the battery
voltage and IBAT is the charge current. The
approximate ambient temperature at which the
thermal feedback begins to protect the IC is:
TA = 120°C − PD • θ JA
TA = 120°C − (VCC − VBAT ) • I BAT • θ JA
Example: An BL4054 operating from a 5V
USB supply is programmed to supply 400mA
full-scale current to a discharged Li-Ion battery
with a voltage of 3.75V. Assuming θJA is
150°C/W, the ambient temperature at which
the BL4054 will begin to reduce the charge
current is approximately:
TA = 120°C − (5V − 3.75V) • 400mA • 150°C / W
TA = 45°C
The BL4054 can be used above 45°C ambient,
- 11 -
www.belling.com.cn
BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
but the charge current will be reduced from
400mA. The approximate current at a given
ambient temperature can be approximated by:
120°C − TA
I BAT =
(VCC − VBAT ) • θ JA
Using the previous example with an ambient
temperature of 60°C, the charge current will
be reduced to approximately:
120°C − 60°C
IBAT =
= 320mA
(5V − 3.75V) • 150°C / W
Moreover, when thermal feedback reduces the
charge current, the voltage at the PROG pin is
also reduced proportionally as discussed in
the Operation section.
It is important to remember that BL4054
applications do not need to be designed for
worst-case thermal conditions since the IC will
automatically reduce power dissipation when
the junction temperature reaches approximately 120°C.
several different board sizes and copper areas.
All measurements were taken in still air on
3/32" FR-4 board with the device mounted on
topside.
Table 1. Measured Thermal Resistance (2-Layer Board*)
COPPER AREA
BOARD THERMAL RESISTANCE
TOPSIDE BACKSIDE AREA JUNCTION-TO-AMBIENT
2500mm2 2500mm2 2500mm2
125℃/W
1000mm2
2
225mm
2
2500mm2
2500mm2
125℃/W
2
2500mm2
130℃/W
2
2
2500mm
100mm
2500mm
2500mm
135℃/W
50mm2
2500mm2
2500mm2
150℃/W
*
Each layer uses one ounce copper
Table 2. Measured Thermal Resistance (4-Layer Board**)
COPPER AREA
BOARD THERMAL RESISTANCE
(EACH SIDE)
AREA JUNCTION-TO-AMBIENT
2500mm2***
2500mm2
80℃/W
**Top and bottom layers use two ounce copper, inner layers use one ounce copper
***10,000mm2 total copper area
VCC Bypass Capacitor
Thermal Considerations
Because of the small size of the ThinSOT
package, it is very important to use a good
thermal PC board layout to maximize the
available charge current. The thermal path for
the heat generated by the IC is from the die to
the copper lead frame, through the package
leads, (especially the ground lead) to the PC
board copper. The PC board copper is the
heat sink. The footprint copper pads should be
as wide as possible and expand out to larger
copper areas to spread and dissipate the heat
to the surrounding ambient. Feed-through vias
to inner or backside copper layers are also
useful in improving the overall thermal performance of the charger. Other heat sources
on the board, not related to the charger, must
also be considered when designing a PC
board layout because they will affect overall
temperature rise and the maximum charge
current.
The following table lists thermal resistance for
PPMIC BU
Many types of capacitors can be used for
input bypassing, however, caution must be
exercised when using multilayer ceramic capacitors. Because of the self-resonant and high
Q characteristics of some types of ceramic
capacitors, 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 Ω resistor in series
with an X5R ceramic capacitor will minimize
start-up voltage transients.
Charge Current Soft-Start
The BL4054 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 fullscale current over a period of approximately
50μs. This has the effect of minimizing the
transient current load on the power supply
during start-up.
- 12 -
www.belling.com.cn
BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Typical Applications
USB/Wall Adapter Power Li-Ion Charger
5V WALL
ADAPTER
BAT
1k
VIN=5V
IBAT
3
Li-Ion
CELL
BL4054
4
USB
POWER
VCC
5
PROG
GND
2
10k
1μF
Full Featured Single Cell Li-Ion Charger
1μF
4
VCC
500mA
3
BAT
2.5k
100mA/
330Ω
500mA
1
μC
BL4054
5
CHRGb
PROG
GND
2
Li-Ion
CELL
2k
SHDN
Using a Microprocessor to Determine CHRGb State
VDD
V+
VCC
BL4054
VCC
BAT
3
500mA
BL4054
1μF
2k
OUT
CHRGb
4
5V WALL
ADAPTER
μPROCESSOR
800k
Basic Li-Ion Charger
with Reverse Polarity Input Protection
PROG
GND
2
5
Li-Ion
CELL
2k
IN
800mA Li-Ion Charger
with External Power Dissipation
VIN=5V
0.25Ω
4
1μF
PPMIC BU
VCC
BAT
3
800mA
BL4054
5
PROG
GND
2
1.25k
Li-Ion
CELL
- 13 -
www.belling.com.cn
BL4054
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in Thin SOT
Package Description
PPMIC BU
- 14 -
www.belling.com.cn