QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC867
LTC4075XEDD
DESCRIPTION
Demonstration circuit DC867 features the
LTC4075X standalone linear charger that is capa-
ble of charging a single-cell Li-Ion battery from
both AC adapter and USB inputs. DC867 is de-
signed to demonstrate the LTC4075X capability to
automatically select the appropriate power source
for charging. DC867 is set up so that when the
USB source is used as the input, the charge cur-
rent is set to 500mA and when the AC adapter is
available, regardless of the USB input connection,
the charge current increases to 800mA.
The enable operation of the LTC4075X changes
with different input sources. When the LTC4075X
is charging from the AC adapter source, a “logic
low” enables the charger and when the USB input
is used for charging, “logic high” is needed to acti-
vate the LTC4075X. DC867 is design to start
charging with AC adapter as default mode. For
USB input charging, the JP1 jumper has to be set
to the
USB on
position or the
USB ENABLE
pin
(turret) has to be pulled above 1V. The jumper
setting can be
USB on
for AC adapter charging
mode but the
USB ENABLE
terminal (turret) has
to be floating or pulled low to enable AC adapter
mode charging.
There are two LED indicators (the third LED is for
optional “USB power” indication) for battery
charge status and input power status.
The
“CHRG” LED will be turned on when LTC4075X is
charging and it will be turned off when charging is
terminated or the LTC4075X is disabled. The
“PWR” LED will be turned on when the input
source is sufficient to begin charging. The “PWR”
LED will be turned off when the input source is not
present or the input source is below the under
voltage lockout threshold (Typically 4.2V for AC
adapter and 4V for USB inputs).
The charge currents for both USB and AC adapter
charging modes and termination current setting
can be easily adjusted by changing the program
resistors. Please refer to the LTC4075X datasheet
for more information.
DUAL INPUT USB / AC ADAPTER STANDALONE LI-ION CHARGER
Design files for this circuit board are available.
Call the LTC factory.
________________________________________________
LTC is a trademark of Linear Technology Corporation
Table 1.
Performance Summary (T
A
= 25°C unless otherwise noted)
PARAMETER FOR LED DRIVER
Input Voltage Range AC adapter and USB
Output Float Voltage VBAT (constant voltage mode)
Charge Current AC adapter
Charge Current USB Input
Charge Termination
Over The Full Operating Temperature
Range (0°C to 85°C)
R4 = 1.24K
R3 = 2.10K
R5 = 2.00K
CONDITION
VALUE
4.3V to 6V
4.2V +/- 1%
800mA
476mA (500mA max, 0°C to
85°C)
50mA
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC867
DUAL INPUT USB / AC ADAPTER STANDALONE LI-ION CHARGER
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).
2
stm32/stm8
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
