QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC867
DUAL INPUT USB / AC ADAPTER STANDALONE LI-ION CHARGER
2
QUICK START PROCEDURE
Demonstration circuit 867 is easy to set up to
evaluate the performance of the LTC4075X. Refer
to Figure 1 for proper measurement equipment
setup and follow the procedure below:
The charger can be evaluated using an actual
Lithium Ion battery or a battery simulator. The bat-
tery simulator is faster because all battery state-of-
charge conditions can be quickly simulated.
A battery simulator consists of an adjustable
power supply with a load resistor across the power
supply output. The resistor value is selected that
will provide approximately 1A when the power
supply is set for 2.5V and power supply must pro-
vide at least 1.7A when adjusted for 4.2V. An ex-
ample for battery simulator would be a 2 Ohm, 10
Watt power resistor connected to the output of a
5V, 5A bench supply.
1. With the input power supply and battery simu-
lator power supply adjusted to 0V, connect the
two power supply outputs to the
ADAPTER
INPUT
and
GND
terminals; and
LI-ION+
and
GND
terminals as shown in Figure 1 to test AC
adapter charging mode. Make sure that
USB
ENABLE
terminal (turret) is floating or pulled
low for enabling AC adapter mode charging.
2. Increase the battery voltage to 3.6V. Observe
the 800mA battery charge current (measured
at input). Start to increase the adapter input
voltage. When the input supply voltage ex-
ceeds 4.2V, the charger should activate and
the PWR and CHRG LEDs will illuminate.
3. Increase the battery voltage to 4.2V and note
that the charge current falls to 0 and “CHRG”
LED will be turned off. This illustrates the con-
stant voltage portion of the charging character-
istic.
4. Set both power supply and battery simulator
back to 0V and connect the power supply (or
USB source) to
USB INPUT
and
GND
termi-
nals; and
LI-ION+
and
GND
terminals as
shown in Figure 1 to test the USB charging
mode. Make sure that the
USB ENABLE
jumper is set to “
USB ON”
position for ena-
bling USB input charging mode.
5. Increase the battery voltage to 3.6V. Observe
the 476mA battery charge current (measured
at input). Start to increase the USB input volt-
age. When the input supply voltage exceeds
4V the charger should activate and the CHRG
LED will illuminate.
6. Test the USB shutdown mode by placing the
USB ENABLE
jumper to “
USB OFF”
position.
Note that the input current (or USB current)
falls to under 30uA to comply with the USB
shutdown mode.
7. Place jumper back to “
USB ON”
position for
enabling USB charging. Increase the battery
voltage to 4.2V and note that the charge cur-
rent falls to 0 and “CHRG” LED will be turned
off. This illustrates the constant voltage portion
of the charging characteristic. Note that the
input current (or USB current) decrease down
to 50uA, which is the typical USB current un-
der standby mode (when the charging is termi-
nated).