Linear Technology DC708 Quick Start Manual page 2

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC708
LITHIUM-ION LINEAR BATTERY CHARGER WITH THERMAL REGULATION
To save time, we recommend using a battery simulator
(described in Table 2 and Figure 1•) If an actual re-
chargeable 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 (VIN)
Digital voltmeter for measuring
battery voltage (VBAT)
Digital voltmeter for measuring
PROG pin voltage (current moni-
tor)
Digital voltmeter for measuring
voltage across current sense resis-
tor (IBAT)
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 measur-
ing charge current
Current sense resistor for measur-
ing battery drain current
SETUP
Refer to Table 2 and Figure 1 for equipment require-
ments and proper setup.
Set jumper JP1 to the "RUN" position (lower posi-
1.
tion).
Set jumper JP2 to the lower position, which programs
2.
the constant charge current to 1A.
Set the input power supply to 0V, and then connect it
3.
to the VIN and GND pins of the demo board.
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
0 to 5V, 2.5A
2Ω, 10W
0.1Ω, 1%, 1W
1k, 1%, 0.5W
Set the battery simulator to 0V, and then connect it to
4.
the BAT and GND pins.
Connect the digital voltmeters as shown in the setup
5.
diagram to measure VIN, V(current monitor), charge
voltage (VBAT) and the charge current (IBAT).
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 0. 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
(VBAT) 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 (VBAT), 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 pro-
grammed 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 re-
duce the charge current (IBAT) to 500mA, resulting in
a reading of approximately 50mV on the charge cur-
2