QUICK START GUIDE FOR DEMO CIRCUITS 530A-A AND 530A-B
LI-ION BATTERY CHARGER
QUICK START PROCEDURE
Demonstration circuits 530A-A and 530A-B are easy to
set up to evaluate the performance of the LTC4050. Re-
fer to Figure 1 for proper measurement equipment setup
and follow the procedure below:
1.
Install jumper JP1 in the PROG position
to enable the
charger.
2.
Set the input power supply to 0V, and then connect it
to the VIN and GND pins of the demo board.
3.
Set the battery simulator to 0V, and then connect it to
the BAT and GND pins.
4.
Connect the digital voltmeters as shown in the setup
diagram to measure VIN, charger voltage (VBAT) and
the charge current (IBAT).
5.
Start the demo board evaluation by increasing the
input power supply to approximately 3.8V (battery
simulator power supply set for 0V). The charger out-
put voltage and charge current should be 0. The
CHRG and ACPR LEDs should be off.
The charger is
off due to the undervoltage lockout feature.
6.
Increase the input voltage to 5V and keep the battery
simulator power supply at 0V. Both LEDs (CHRG and
ACPR) should now be on, the charger output voltage
(VBAT) should be approximately 140mV, and the
charge current should be approximately 70mA.
This
is the trickle charge mode for a deeply discharged
battery.
Typically, a battery that has not been charged
for a long time.
7.
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 out-
put 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
current (IBAT) to the programmed value of approxi-
mately 700mA.
This is the constant current mode.
8.
Continue slowly increasing the battery simulator
power supply, thus simulating a battery accepting
charge. The charge current should remain at the pro-
grammed value of 700mA until the charger output
voltage is within approximately 10mV of the preset
charge voltage, at which time the charge current will
begin to decrease.
This is the beginning of the con-
stant voltage portion of the charge cycle.
9.
Continue slowly increasing the battery simulator
power supply until the charge current drops to ap-
proximately 200mA, and then read the charger output
voltage.
This reading is the charger float voltage
(VBAT) which will be either 4.1V or 4.2V ± 40mV
depending on the demo board version.
10.
Place jumper JP1 in the SHDN position. The charger
will shut down, dropping the charge current to 0mA.
The ACPR LED remains on and the charge LED goes
out.
11.
Return JP1 to the PROG position.
12.
Continue slowly increasing the battery simulator
power supply while observing the CHRG LED. The
LED will go out when the charge current drops to ap-
proximately 10% of the programmed charge current
of 700mA.
This verifies that the C/10 output is oper-
ating correctly.
The current through the LED drops from approxi-
mately 10mA when the LED is on, to approximately
30µA 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
approximately 94% charged. The charger will con-
tinue charging for a total of 3 hours (0.1µF timing ca-
pacitor) and then stop, at which point the battery is
approximately 99% charged.
NOTE:
For evaluation purposes, the time can be de-
creased from the programmed 3 hours to approxi-
mately 30 seconds by reducing the timer capacitor
(C3) from 0.1µF to 270pF.
13.
After the timer has timed out, slowly decrease the
battery simulator power supply. At approximately
3.88V for demo board DC530A-A, a new 700mA
charge cycle begins. With demo board DC530A-B,
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