DC531A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 531
LI-ION BATTERY CHARGER
LTC4052
DESCRIPTION
Demonstration circuit 531 is a complete pulse battery
charger designed to charge one Lithium-Ion cell. DC531
features the LTC4052 Li-Ion pulse charger with internal
MOSFET suitable for charging at a maximum current of
1A.
Other Features include:
‰ Preset float voltage of 4.2V ±1%
‰ Constant Current set by wall adapter current limit
‰ Over current protection
‰ 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 Li-Ion battery.
‰ Trickle charge for deeply discharged batteries
‰ Auto recharge when battery voltage drops below 4.05.
‰ Low battery drain current when the input supply is
removed
‰ Input Power OK LED indicator (ACPR)
‰ C/10 Charge LED indicator (CHRG)
Small surface mount components are used to minimize
board space and height with the circuitry occupying approximately 0.15 square inches of board space with a
height of 0.054 inches (1.4mm).
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary
PARAMETER
VALUE
Input Voltage Range
4.5V to 10V
Output Voltage VBAT
4.2V ±1%
Output Current IBAT (constant current mode) Up to 1A (determined by
input supply current limit)
Output Current IBAT (trickle current mode)
24mA ±40%
C/10 CHRG LED Threshold Level
10% Duty Cycle
Trickle Charge Threshold Voltage
2.45V
Battery Drain Current with VIN Removed
1µA
QUICK START PROCEDURE
Demonstration circuit 531 is easy to set up to evaluate
the performance of the LTC4052. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
1. Before connecting the input power supply to the de-
mo board, adjust the power supply current limit to
1A. Adjust the output voltage to 0V and then connect
the power supply to the Vin and GND pins of the
demo board.
2. Set the battery simulator to 0V, and then connect it to
the BAT and GND pins.
3. Connect the digital voltmeters as shown in the setup
4. Begin increasing the input voltage to 6V and keep the
battery simulator power supply at 0V. Both LEDs
(CHRG and ACPR) should have come on at approximately 2V, and the charge current should be approximately 24mA. This is the trickle charge mode for a
deeply discharged battery. Typically, a battery that
has not been charged for a long time.
5. Starting from 0V, slowly increase the battery simula-
tor power supply (VBAT), observing the charger’s
output voltage on the DVM. When the charger’s output voltage exceeds approximately 2.5V, the charger
will suddenly enter the Constant current portion of the
charge cycle resulting in an abrupt increase in charge
diagram to measure the input voltage VIN, charger
voltage (VBAT) and the charge current (IBAT).
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 531
LI-ION BATTERY CHARGER
current (IBAT) to the current limit of the input power
supply. This is the constant current mode.
6. Continue to slowly increase the battery simulator
power supply until the charge current pulsing begins.
Approximately 3 seconds after the pulsing stops, the
CHRG LED turns off and stays latched off.
NOTE: When an actual battery is used, the battery volt-
4.260V. The 60mV overvoltage is due to the (measured) 60mΩ resistance of the internal ESR of the battery simulator power supply and associated wiring,
and the 1A of charge current. The pulsing stops when
the lower portion of the charger voltage exceeds
4.200V ±1% or the timer ends the charge cycle.
7. After the timer has timed out, slowly decrease the
age rises much slower than the battery simulator, resulting in a very gradual decrease in pulse duty cycle.
When the duty cycle drops to 10%, the CHRG LED
goes off, though there is still 40µA flowing through
the LED.
battery simulator power supply. At approximately
4.05V the charge current resumes and a new charge
cycle begins. This is the Recharge Threshold Voltage.
When the timer ends (3 hours for a 0.1µF timing capacitor) the charge cycle ends and the CHRG pin becomes high impedance. Connecting a new battery or
cycling the input power turns on the CHRG LED, starting a new charge cycle. A new charge cycle also begins if the battery voltage drops below 4.05V, though
the CHRG LED is not on.
creased from the programmed 3 hours to approximately 30 seconds by reducing the timer capacitor
(C4) from 0.1µF to 270pF
When the charger is in the pulse mode, the DVM
reading appears to exceed the 4.2V Li-Ion float voltage. This is because when the charger is pulsing, the
LTC4052 monitors the charger’s output voltage when
the charge current is not flowing. Because of the battery and pack protection ESR, wiring and connector
resistance, the charger’s output voltage will exceed
the 4.2V float voltage when the charge current is flowing.
Figure 2 shows typical waveforms when the battery is
near the end of the charge cycle. The charger output
voltage, when charge current is flowing, approaches
NOTE: For evaluation purposes, the time can be de-
8. To verify battery drain current, remove the input sup-
ply voltage. The ammeter that was reading charge
current now reads the battery drain current. A typical
value is less than 1µA.
9. To verify the overcurrent protection feature, adjust the
battery simulator power supply to approximately 3.5V.
Increase the current limit of the input power supply to
approximately 2.5A. When the charge current reaches
the overcurrent threshold of approximately 1.9A, the
charge current immediately stops, waits for 640ms,
then rises again, resulting in short pulses of current at
approximately 1.6Hz. These short pulses of current
represent an average current of approximately 1% of
the overcurrent level of 1.9A. Figure 3 shows the
waveforms.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 531
LI-ION BATTERY CHARGER
MEASURE
CHARGE
CURRENT
(IBAT)
+
+
+
VBAT
+
–
INPUT POWER SUPPLY
4.5V–10V
2.5A
WITH ADJUSTABLE
CURRENT LIMIT
–
RECOMMENDED
LI-ION BATTERY SIMULATOR*
+
2Ω
10W
PRELOAD
–
–
BATTERY
SIMULATOR
BENCH
POWER SUPPLY
0V–4.3V
2A
WITH COURSE
AND FINE
VOLTAGE
ADJUSTMENT
–
* CAN USE A LI-ION BATTERY,
THOUGH TESTING TAKES MORE TIME
Figure 1. Proper Measurement Equipment Setup
NOTE: Although it would take more time, this charger can also be evaluated using a rechargeable Li-Ion battery in
place of the battery simulator pictured here. If you use an actual battery, 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.
6V
INPUT
VOLTAGE
5V
4V
THIS AMPLITUDE IS A RESULT
OF THE TOTAL ESR AND 1A OF
CHARGE CURRENT
4.25V
CHARGER
OUTPUT
VOLTAGE
4.20V
4.15V
TOTAL ESR = 60mΩ
AC ADAPTER = 5.8V
AC ADAPTER CURRENT LIMIT = 1A
1.0A
CHARGE
CURRENT
0.5A
0A
Figure 2. End of Charging Cycle
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 531
LI-ION BATTERY CHARGER
6V
INPUT
VOLTAGE
5V
4V
4.25V
CHARGER
OUTPUT
VOLTAGE
4.20V
4.15V
1.0A
CHARGE
CURRENT
0.5A
0A
Figure 3. Overcurrent Protection
4
5
4
3
2
1
D
D
VIN
+VIN
4.5V-10V
1A Limit
E1
D2
GRN
ACPR
D1
RED
CHRG
R2
750
R1
750
R4
10K
U1*
3 LTC4052EMS8E
C1
0.047uF
25V
+VIN
C2
0.022uF
25V
CHRG
C
2
ACPR
GND
C3
1.0uF
16V
7
GATE
6
R5
4.7
R3
0.04
1206
SENSE
1
BAT
8
C
E3
BAT
TIMER
4
5
GND
E2
Single
Li-lon Cell
C4
0.1uF
16V
GND
E4
B
B
CONTRACT NO.
* VERSION TABLE
A
VERSION
Battery Voltages
DC531A-A
4.2V
APPROVALS
DRAWN
U1
LTC4052EMS8E-4.2
June Wu
DATE
5/3/02
CHECKED
TECHNOLOGY
TITLE
DESIGNER
5/3/02
SIZE CAGE CODE
Thursday, February 20, 2003 SCALE:
4
A
LTC4052EMS8E, Li-Ion Battery Pulse Charger
APPROVED
ENGINEER Fran Hoffart
5
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
3
DWG NO
FILENAME:
2
REV
DC531A
SHEET
A
1
1
OF
1
Similar pages