DEMO MANUAL DC705A
LTC4053EMSE-4.2
Lithium-Ion Linear Battery Charger
with Thermal Regulation
Description
Demonstration circuit DC705 is a complete constant-
current, constant-voltage battery charger designed to
charge one Lithium-Ion cell. The
LTC
®
4053EMSE-4.2
used
on this demo circuit features an internal P-channel power
MOSFET with a unique thermal feedback loop that reduces
the output current under high ambient temperature and/or
high power dissipation conditions. This feature allows the
charger to provide higher charge currents under normal
conditions and still provide safe charging under abnormal
conditions such as high ambient temperature, high input
voltage or low battery voltage. The IC is available in a 10-pin
MSOP thermally enhanced package featuring an exposed
bottom-side metal pad for soldering to the PC board.
Other features include:
•
Preset float voltage of 4.2V ±1%
• 1A
and 0.5A constant current selected by a jumper
•
Capable of charging directly from USB power
• 3-hour
charge termination timer. This timer can be set
for other time periods through a capacitor change. For
instance, you may want to use a much shorter period
(on the order of 30 seconds) when evaluating the board
with a battery simulator instead of a real Li-Ion battery.
•
Charge current monitor output can be used for gas
gauging
•
Manual shutdown
•
Low battery drain current when input supply is removed
•
No isolation diode or current sense resistor required
•
C/10 trickle charge for deeply discharged batteries
•
Auto recharge when battery voltage drops below pre-
set threshold
•
Input power OK LED indicator (ACPR)
•
C/10 charge LED indicator (CHRG)
•
Fault LED indicator for “out of temp range” (FAULT)
Small surface mount components are used to minimize
board space and height with the circuitry occupying ap-
proximately 0.15 square inches of board space with a
height of 0.054 inches (1.4mm).
Table 1. Typical Demo Board Specifications
Input Voltage Range V
IN
Output Voltage V
BAT
(Constant
Voltage Mode)
Output Current I
BAT
(Constant
Current Mode)
Current Monitor Output
Output Current I
BAT
(Trickle Current
Mode)
C/10 CHRG LED Threshold Level
Circuit Board Temperature in
Thermal Feedback Mode
Trickle Charge Threshold Voltage
Battery Drain Current with V
IN
Removed
4.25V to 7V (Upper Range Limited
by PC Board Dissipation)
4.2V ±1%
1A ±8%, 0.5A ±8% (Selected by
Jumper)
1.5V ±5% at Full Current
100mA ±20%, 50mA ±20%
100mA ±20%, 50mA ±25%
60°C to 70°C
2.457V
< 1µA
Design files for this circuit board are available at
http://www.linear.com/demo/DC705A
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
dc705af
1
DEMO MANUAL DC705A
Quick start proceDure
To save time, we recommend using a battery simulator
(described in Table 2 and Figure 1) If an actual rechargeable
Li-Ion battery is used, keep the DC resistance between the
charger and the battery to a minimum, as this will affect
the charge current in the constant voltage mode.
Table 2. Test Equipment Required for Demo Board Evaluation
Lab power supply for input power
Digital voltmeter for measuring input
voltage (V
IN
)
Digital voltmeter for measuring battery
voltage (V
BAT
)
Digital voltmeter for measuring PROG pin
voltage (current monitor)
Digital voltmeter for measuring voltage
across current sense resistor (I
BAT
)
4.2V rechargeable Li-Ion cell or battery
simulator
Battery Simulator Consists of:
Power supply with coarse and fine output
voltage adjust controls
Power resistor (preload for power supply)
Current sense resistor for measuring
charge current
Current sense resistor for measuring
battery drain current
0 to 5V, 2.5A
2Ω, 10W
0.1Ω, 1%, 1W
1k, 1%, 0.5W
0 to 7V, 1.2A
3 1/2 digits
4 1/2 digits, resolution to
1mV
3 1/2 digits, resolution to
1mV
100mV range
600mA/Hr to 1.3A/Hr
SETup
Refer to Table 2 and Figure 1 for equipment requirements
and proper setup.
1. Set jumper JP1 to the “RUN” position (lower position).
2. Set jumper JP2 to the lower position, which programs
the constant charge current to 1A.
3. Set the input power supply to 0V, and then connect it
to the V
IN
and GND pins of the demo board.
4. Set the battery simulator to 0V, and then connect it to
the BAT and GND pins.
5. Connect the digital voltmeters as shown in the setup
diagram to measure V
IN
, V(current monitor), charge
voltage (V
BAT
) and the charge current (I
BAT
).
2
dc705af
MEASURE CHARGE CURRENT
+
–
0.1
1%
Quick start proceDure
BATTERY
SIMULATOR
BENCH POWER
SUPPLY
+
+
–
VBAT
+
2
10W
PRELOAD
0V TO 4.3V
AT 2.5A
INPUT POWER
SUPPLY
0V TO 7V
1.5A
DO NOT
EXCEED 7V
+
–
–
WITH COURSE
AND FINE
VOLTAGE
ADJUSTMENT
DC705A F01
–
MONITOR
CHARGE
CURRENT
MEASURE
BATTERY
VOLTAGE
Figure 1. proper Measurement Equipment Setup
DEMO MANUAL DC705A
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3
DEMO MANUAL DC705A
Quick start proceDure
EvAluATion
undervoltage lockout Feature
•
Increase the input power supply to approximately 3.8V
(battery simulator power supply set for 0V).
The charger output voltage and charge current should
be 0V. All three LEDs should be off. The charger is in
shutdown due to the undervoltage lockout feature.
Trickle Charge Current
•
Increase the input voltage to 5V and keep the battery
simulator power supply at 0V.
The CHRG and ACPR LEDs should now be on, and the
FAULT LED should be off. The charger output voltage
(V
BAT
) should be approximately 240mV, and the charge
current should be about 100mA (10mV on the charge
current DVM). This is the trickle charge mode for a
deeply discharged battery. Typically, a battery that has
not been charged for a long time.
Constant Current Charge
•
Starting at 0V, slowly increase the battery simulator
power supply (V
BAT
), observing the charger’s output
voltage on the DVM.
When the charger’s output voltage exceeds approxi-
mately 2.45V, the charger will suddenly enter the con-
stant current portion of the charge cycle, resulting in an
abrupt jump in the charge current to the programmed
value of approximately 1.0A (100mV on the charge
current DVM). This is constant current mode.
Move jumper JP2 to the upper position (0.5A) to reduce
the charge current (I
BAT
) to 500mA, resulting in a read-
ing of approximately 50mV on the charge current DVM.
Move the jumper back to the original position.
vpRoG verification
•
With 1.0A charge current flowing into the battery simu-
lator, measure the current monitor pin voltage V
PROG
.
This voltage is proportional to charge current with 1.5V
indicating full programmed current (1.0A).
Constant voltage Charge
1. Continue slowly increasing the battery simulator power
supply, thus simulating a battery accepting charge.
The charge current should remain at the programmed
value of 1.0A until the charger output voltage is within
approximately 10mV of the of the preset charge volt-
age, at which time the charge current will begin to de-
crease. This is the beginning of the constant voltage
portion of the charge cycle.
2. Continue slowly increasing the battery simulator power
supply until the charge current drops to approximately
200mA (20mV on the charge current DVM), then read
the charger output voltage. This reading is the charger
float voltage which should be 4.2V ±40mV.
Shutdown
1. Move the SHDN/CHRG jumper JP1 to the upper posi-
tion.
This shuts the charger down dropping the charge cur-
rent to 0mA. This is the shutdown mode.
2. Move the jumper back to the original location.
Charge lED, C/10 Charge near Complete
•
Continue to slowly increase the battery simulator power
supply while observing the CHRG LED. The LED will
go out when the charge current drops to approximately
10% of the programmed charge current of 1.0A. This
verifies that the C/10 output is operating correctly.
NOTE: The LED current drops from approximately 10mA
when the LED is on, to approximately 25µA when the
charge current drops to 10%, and drops to 0µA after
the timer has timed out. (3 hours when a 0.1µF timing
capacitor is used).
At C/10, when the CHRG LED goes out, the battery is
about 94% charged. The charger will continue charging
for 3 hours (0.1µF timing capacitor) then stop, at which
point the battery is 100% charged.
4
dc705af
DEMO MANUAL DC705A
Quick start proceDure
Recharge
•
After the timer has timed out, slowly decrease the
battery simulator power supply. At around 4.05V, the
1.0A charge current should return. This is the Recharge
Threshold Voltage.
NOTE: For evaluation purposes, the time can be de-
creased from the programmed 3 hours to approximately
30 seconds by reducing the timer capacitor (C3) from
0.1µF to 270pF.
Sleep Mode
•
To verify battery drain current in the sleep mode, re-
move the input supply voltage or shut the supply off,
replace the 0.1Ω current sense resistor with a 1kΩ, and
set the battery simulator power supply to approximately
4V. The charge current DVM will now read battery drain
current with 1mV/µA.
NOTE: On this demo board, the thermistor (R6) is
replaced with a 10kΩ resistor. Because the board can
get quite hot, the thermistor must be located near the
battery, not on the PC board.
Thermal Control loop
1. Increase the input voltage to about 6.5V, and reduce
the battery simulator power supply to around 3V.
This causes increased power dissipation, which raises
the LTC4053 junction temperature. When the junction
temperature reaches approximately 105°C, the charge
current decreases enough to maintain the junction
temperature at 105°C.
2. Increase the battery simulator voltage or reduce the input
voltage to reduce the charger power dissipation and
allow the charge current to return to the programmed
current of 1A.
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