QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC929A-A/B
USB POWER SOLUTION IN DFN 6X3
LTC4089/-5
DESCRIPTION
Demonstration circuit DC929A-A/B is a monolithic high
voltage (6V-36V) switching buck regulator, USB Power-
path controller, and Li-Ion battery charger. It is based
on the LTC4089/-5 and provides the following functions:
1.2A monolithic buck regulator with output voltage
tracking battery voltage V
BAT
, a 700mA CC/CV timer ter-
minated temperature qualified charger suitable for Li-Ion
cells, a USB power manager that insures compliance
with the USB power specification and Powerpath man-
agement for the battery. The LTC4089/-5 uses the in-
Table 1. Performance Summary
PARAMETER
HVIN Input Voltage
HVOUT/VOUT
V
HVIN
= 6V - 36V
CONDITION
VALUE
6V - 36V
= V
BAT
+0.3V (for LTC4089)
= 5V (for LTC4089-5)
Battery Charger
I
BAT
Float Voltage
Trickle Charge Threshold
Recharge Threshold
USB Current
I
USB
- 500mA Mode
I
USB
- 100mA Mode
I
USB
- Suspend Mode
V
USB
= 5V, USB Active 500mA Mode
V
USB
= 5V, USB Active 100mA Mode
V
USB
=5V, USB Suspend
475mA typical, 500mA max
93mA typical, 100mA max
50uA typical , 100uA max
V
USB
= 5V, Vbat=3.6V
V
USB
= 5V, battery disconnected from BATT pin
V
USB
= 5V
V
USB
= 5V
700mA +/- 7%
4.20V +/- 35mV
2.9V +/- 0.1V
(Vfloat – 130mV) to (Vfloat-60mV)
termediate bus voltage topology that results in faster
charging and lower power loss than the charger fed to-
pology. All this functionality consumes less than 2cm
2
of PCB area with all components on one side of the PCB.
Design files for this circuit board are available. Call
the LTC factory.
, LTC , LT, and Powerpath are registered trademarks of Linear Technology
Corporation.
OPERATING PRINCIPLES
DC929A-A is the demo board for LTC4089, while
DC929A-B is for LTC4089-5. The only difference is that
the voltage on HVOUT/VOUT of LTC4089 tracks battery
voltage (0.3V higher than V
BAT
, with minimum of 3.46V,
maximum 4.6V), while that of LTC4089-5 is fixed at 5V.
This chip manages the power supplies that would be
typical for a USB powered device and/or a high voltage
source, such as fire wire or automotive battery. Power
is input from either the USB cable or a high voltage
adapter to an intermediate voltage bus VOUT. The inter-
mediate voltage bus is preferentially powered from the
adapter, then USB and finally if required from the battery
via an internal ideal diode and an optional external
MOSFET (Q2). The battery charger is a CC/CV timer ter-
minated type capable of charge currents of up to 1.2A.
QUICK START PROCEDURE
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC929A-A/B
USB POWER SOLUTION IN DFN 6X3
Demonstration circuit DC929A-A/B is easy to set up to
evaluate the performance of the LTC4089/-5. Refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below:
1.
Adapter Charging
6.
Connect input power supply, meters and output load
as shown in Figure 1, with the following initial values:
PS1 = 0V
PS2 = 5V
PS3 = 2.5V
I
USB
= 0mA
8.
9.
7.
Ramp up the wall adapter voltage. When the wall
adapter exceeds 5.9 volts the LTC4089 will cease
drawing current from the USB and switch over to the
wall adapter. Both the AC-present LED (D3, red) and
charge LED (D4, green) are on.
Note that the V
OUT
of DC929A-A is about 0.3V above
V
BAT
, indicating the adaptive feature of V
OUT
to mini-
mize the charging power loss. The V
OUT
of DC929A-B
is fixed at 5V.
Note that the charge current to the battery has in-
creased to 700mA.
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. In the
mean time, the charge LED (D4) turns off.
Both USB input voltage and the adapter input
voltage to zero. The battery will now power the load
on the System Load Output, illustrating the ideal di-
ode function of the LTC4085. Note that the battery is
now being discharged.
USB Charging
2.
Place the USB ON/OFF jumper (JP3) in the ON posi-
tion. Place the USB Current jumper (JP2) in the
500mA position. Turn on the power supplies, the
charger should activate and the charge LED D4 will il-
luminate. The battery will be in trickle charge mode,
I
BAT
is around 70mA. Increase the battery voltage to
above 2.9V the battery charge current (I
BAT
) will in-
crease to 470mA. Note that the input current from
the USB (I
USB
) is about 475mA, which does not exceed
the USB spec of 500mA.
Now increase the load on the SYSTEM LOAD OUTPUT
(I
OUT
). Note that as the output load is increased the
charging current is decreased and the USB current
remains within the 500mA limit.
Place the USB current jumper in the 100mA position
and note that USB input current falls to maintain
compliance with the USB input current spec. Also
note that as the external load is increased the battery
will start to discharge into the SYSTEM LOAD
OUTPUT, illustrating the ideal diode function of the
LTC4089
Place the USB ON/OFF jumper (JP1) in the OFF posi-
tion and note that the USB current falls to under
100uA to comply with the USB suspend mode cur-
rent.
Battery Powered Operation
10.
Set
3.
Other
Frequency at charge timer cap C4 changes with charging
current, indicating the adaptive feature to ensure the full
charge of battery.
11.
4.
Pins are provided to all control functions in order to
simplify wiring of the demo circuit into a system
board.
NTC function; provision has been made for connec-
tion of an external 10k NTC, for temperature 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.
12.
5.
2
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