QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC848
USB POWER SOLUTION IN QFN 4X4
1
LTC4066
DESCRIPTION
Demonstration circuit DC848 is a complete power
controller for a USB powered device. It is based
on the LTC4066 and provides the following func-
tions; 700mA CC/CV timer terminated temperature
qualified charger suitable for Li-ion cells, a USB
power manager that insures compliance with the
USB power specification and power path man-
agement for the battery. The LTC4066 uses the
intermediate bus voltage topology that results in
faster charging and lower power loss than the
charger fed topology. All this functionality con-
sumes less 77mm
2
of PCB area with all the com-
ponents on one sid e.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Cor-
poration.
Table 1. Performance Summary
PARAMETER CONDITION VALUE
Input Voltage 4.5-5.5V
Battery Charger
Iout V
IN
= 5V, Vbat=3.6V 700mA +- 7%
Float voltage Vin = 5V, battery disconnected from BATT pin 4.20v+/- 35mV
Trickle Charge threshold V
IN
= 5V 2.9V +-0.1V
Recharge threshold V
IN
= 5V (Vfloat – 130mV) to (Vfloat-60mV)
USB Current
Input Current 500mA mode V
IN
= 5V, USB Active 500mA mode 475mA typical, 500mA max
Input Current 100mA mode V
IN
= 5V, USB Active 100mA mode 93mA typical, 100mA max
Input Current suspend mode V
IN
=5V, USB suspend 300uA max
OPERATING PRINCIPLES
Demo DC848 is base d on the LTC4066. This chip
manages the power supplies that would be typical
for a USB powered device. Power is input from
either the USB cable or an adapter to an interme-
diate voltage bus. The intermediate voltage bus is
preferentially powered from the adapter, then USB
and finally if required from the battery via an ideal
diode. The battery charger is a CC/CV timer ter-
minated type capable of charge currents of up to
800mA.
QUICK START PROCEDURE
Demonstration circuit DC848 is easy to set up to
evaluate the performance of the LTC4066. Refer
to Figure 1 for proper measurement equipment
setup and follow the procedure below:
1.
Connect input power supply, meters and output
load as shown in Figure 1.
USB Charging
2.
Place the Master ON/O FF jumper in the ON po-
sition.
3.
Place the USB ON/OFF jumper in the ON posi-
tion. Place the USB current jumper in the
500mA position. Set the battery simulator volt-
age to zero, slowly raise the USB input voltage.
When the supply voltage exceeds 3.8V the
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC848
USB POWER SOLUTION IN QFN 4X4
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charger sho uld activate and the ch arge LED D3
will illuminate. The battery will be in trickle
charge mode. Increase the battery voltage to
3.6V from abo ut 2.9V the battery charge curr ent
will increase to 475mA. Note that the inpu t cur-
rent from the USB does not exceed the USB
spec of 500mA.
4.
Now increase the load on the SYSTEM LOAD
OUTPUT. Note that as the output load is in-
creased the charging current is decreased and
the USB current remains within the 500mA limit.
5.
Place the USB curren t jumper in the 100m A po-
sition and note that USB input current falls to
maintain compliance with the USB input current
spec. Also note that as the external load is in-
creased the battery will start to discharge into
the SYSTEM LOAD OUTPUT, illustrating the
ideal diode function of the LTC4066
6.
Place the USB ON/OFF jumper in the OFF po-
sition and note that the USB current falls to un-
der 300uA to comply with the USB suspend
mode current.
Adapter Charging
7.
Ramp up the wall adapter voltage. When the
wall adapter exceeds 4.3 volts the LTC4066 will
cease drawing cur rent from the USB and switch
over to the wall adapter.
8.
Note that the charge current to the battery has
increased to 700mA.
9.
Increase the battery voltage to 4.2V and note
that the charge current falls to 0 this illustrates
the constant voltage portion of the charging
characteristic.
Battery Powered Operation
10.
Set Both USB input voltage and the adapter in-
put voltage to zero. The battery will now power
the load on the System Load Output, illustrating
the ideal diode function of the LTC4066. D4
comes on. Note that the battery is now being
discharged.
Other
11.
Frequen cy at char ge timer cap C2 chan ges with
charging current, indicating the adaptive feature
to ensure the full charge of battery.
12.
Pins are provided to all control functions in or-
der to simplify wiring of the demo circuit into a
system board.
13.
NTC function; provision has been made for
connection of an external 10k NTC, for tem-
perature qualified charging. To use this feature
set the NTC jumper in the external position and
connect the external NTC to the NTC terminal
and ground.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC848
USB POWER SOLUTION IN QFN 4X4
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Figure 1. Proper Measurement Equipment Setup
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC848
USB POWER SOLUTION IN QFN 4X4
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