DEMO MANUAL
DC2386A-A/DC2386A-B
LTC4125EUFD and
LTC4120EUD Wireless Power Transfer
Battery Charger Demonstration Kit
DC2330A transmitter supports Foreign Object Detection
via the
LTC4125.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2386A
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
DESCRIPTION
Demonstration kit DC2386A is a kit of the DC2330A
LTC
®
4125EUFD demonstration board, the DC2445A-A/
DC2445A-B LTC4120EUD demonstration board, and an
assortment of different length standoffs. The DC2330A
can deliver up to 1.68W to the receive board with up to
12mm spacing between the transmit and receive coils. The
CONTENTS
1
×
DC2330A (LTC4125EUFD) Demo Board
1
×
DC2445A-A/DC2445A-B (LTC4120EUD) Demo board (with 12.5mm (0.5") Nylon Standoffs, 8.25mm Gap), see Figure 3
4
×
6.25mm (0.25˝) Nylon Standoffs (2.0mm Gap)
4
×
9.5mm (0.375˝) Nylon Standoffs (5.25mm Gap)
4
×
15.9mm (0.625˝) Nylon Standoffs (11.65mm Gap)
Kit Build Options
KIT NUMBER
DC2386A-A
DC2386A-B
T
X
BOARD
DC2330A
DC2330A
LTC T
X
PART NUMBER
LTC4125EUFD
LTC4125EUFD
R
X
BOARD
DC2445A-A
DC2445A-B
LTC R
X
PART NUMBER
LTC4120EUD-4.2
LTC4120EUD
R
X
OPTION
Fixed 4.2V Float Voltage
Adjustable Float Voltage
PERFORMANCE SUMMARY
SYMBOL
V
IN
I
VIN
V
BAT
V
BAT
I
BAT
AIR GAP
PARAMETER
DC2330A Voltage Input
DC2330A V
IN
Current
DC2445A-A BAT Pin Voltage
DC2445A-B BAT Pin Voltage
DC2445A BAT Pin Current
Separation Between LT
X
and LR
X
I
VIN
≤ 2.5A
V
IN
= 5V
Specifications are at T
A
= 25°C
MIN
3
4.15
4.2
4.2
370mA
385mA
8.25
400mA
TYP
MAX
5.5
2.0
4.25
UNITS
V
A
V
V
A
mm
CONDITIONS
R9 = 1.40MΩ, R10 = 1.05MΩ
V
BAT
= 3.7V, DC2445A-A/DC2445A-B(R5) = 3.01kΩ
I
BAT
= 400mA (Figure 3)
Figure 1. DC2330A Picture
Figure 2. DC2445A-A/DC2445A-B Picture
dc2386aabfa
1
DEMO MANUAL
DC2386A-A/DC2386A-B
QUICK START PROCEDURE
Refer to Figure 4 for the proper measurement equip-
ment setup and jumper settings, DC2445A mounting on
DC2330A, and follow the procedure below.
NOTE. When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the V
CC
or V
IN
and GND terminals. See Figure 5 for proper scope
probe technique.
1. Place the DC2445A-A/DC2445A-B board atop the
DC2330A board, by aligning: (See Figure 4)
DC2330A Mounting Hole
MH3
MH2
MH4
MH6
=>
=>
=>
=>
DC2445A-A/B MH
MH1
MH2
MH3
MH4
lighting up sequentially. When a valid load is found the
LED sweeping will freeze until the next search period,
≈ 3.7s later. Note that the last LED, the red LED, should
not normally be lit.
Observe AM1 and AM2. AM2 should have increased
from ≈10mA RMS, 250mA peak to about 600mA. AM1
should be reading 380mA ~ 400mA of charge current
into the battery emulator. All the charge LEDs on the
DC2445A-X should now be lit.
If the DC2445A-X board is receiving power, it will at-
tempt to charge the battery. Again this is evinced by
the green LEDs lighting. If all the green LEDs are lit,
the LTC4120EUD, on the DC2445A, is charging at the
full programmed battery charge current.
3. The LTC4125EUFD on the DC2330A, keeps the transmit
power at slightly more than the load requires for ≈ 3.7s,
then searches again. This is why the blue LEDs on the
DC2330A go out and start ramping up again.
This should result in the transmit antenna being directly 4. When the system is operating correctly, slide a piece of
above the receive antenna, with the centers aligned.
blank PCB*, or coin between the transmit and receive
The standoffs on the DC2445A-A/DC2445A-B are
coils. The transmit current should immediately drop to
0.5"(12.5mm) when shipped. This results in an air gap
0A. This is the Foreign Object Detection in operation,
of 8.25mm (See Figure 3). The DC2386A kit ships with
preventing a foreign object from getting hot.
three additional standoff sizes. This allows the air gap
to be varied from 0.083" (~2.0mm) to 0.46" (~11.6mm). 5. Please change the standoffs on the DC2445A-A/
DC2445A-B board to yield the air gap most appropriate
2. Set PS1 = 3.7V, PS2 = 5V, and enable the power sup-
for your project.
plies. The DC2330A should start sweeping the LT
X
cur-
*Testing with a blank PCB of at least 10cm
2
(1.5 IN
2
) of copper.
rent looking for a load. This is evinced by the blue LEDs
LR
X
EMBEDDED
IN PCB
F01
DC2445 PCB
4×12.5mm (0.5 INCH)
STANDOFFS
8.25mm
LT
X
DC2330 PCB
4.25mm
12.5mm
Figure 3. As Shipped Demo Kit Air Gap
2
dc2386aabfa
DEMO MANUAL
DC2386A-A/DC2386A-B
QUICK START PROCEDURE
+
PS1
+
3.7V BIPOLAR SUPPLY
±1A
–
–
AM1
CONNECTING THE DC2445A-A/DC2445A-B
PS2
5V SUPPLY
1A
+
–
+
AM2
–
CONNECTING THE DC2330A
PS2
5V SUPPLY
1A
+
–
+
AM2
–
+
PS1
+
3.7V BIPOLAR SUPPLY
±1A
–
–
AM1
DC2445A-A/DC2445A-B MOUNTED ON TOP OF DC2330A
Figure 4. Equipment Setup for DC2386A–A/DC2386A–B Kit
Figure 5. Measuring Input or Output Ripple
Note: All connections from equipment should be Kelvin connected directly to the board pins which they are con-
nected on this diagram and any input or output leads should be twisted pair.
dc2386aabfa
3
DEMO MANUAL
DC2386A-A/DC2386A-B
THEORY OF OPERATION
The DC2386A kit demonstrates operation of a magneti-
cally coupled resonant Wireless Power Transfer (WPT)
system. The LTC4125EUFD transmitter searches for a
suitable load, and powers it until the next search period.
The LTC4120EUD battery charger uses DHC to control its
input power ensuring full power charging under a variety
of operating conditions.
DC2330A – Wireless Power Transmitter Board
featuring the LTC4125EUFD
The DC2330A Wireless Power Transmitter is used to power
a load wirelessly. In this kit, it is used in conjunction with
the DC2445A-X Wireless Power Receiver Board to charge
a Li-Ion battery.
The LTC4125EUFD implements an AutoResonant drive of
the series resonant tank composed of LT
X
(See LT
X
Table 1
for a list of tested LT
X
coils) and CT
X
(See DC2330A Sche-
matic on page 12). The AutoResonant drive uses a zero
crossing detector to determine the resonant frequency
of the series LC circuit. All subsequent duty cycles dis-
cussed here use the resonant period determined by the
AutoResonant circuitry.
The SW1 and SW2 pins each have a half bridge drive. At
zero current crossing, whichever SW
X
pin has current flow-
ing out of the pin, is set to V
IN
for a duty cycle determined
by the corresponding PTH
X
pin (see Figure 10). When the
Table 1. Tested LTX Coils
Vendor
Würth
Inter-Technical
Sunlord
Part Number
760308100110
L4000T02
SWA50N50H35C05B
http://www.we-online.com
http://www.inter-technical.com/index.php?page=products#
http://www.sunlordinc.com/
URL
SW
X
pin is set to V
IN
, it increases the current flowing in
the transmitter series resonant LC circuit. The absolute
value of the tank current is determined by the resonant tank
components
and also by the reflected load impedance.
The LTC4125EUFD sweeps the duty cycle by way of a 5
bit DAC that sets the PTH
X
voltage, and hence duty cycle.
The FB pin is driven by the node forming the junction of
the transmit coil, LT
X
, and the transmit capacitor, CT
X
.
The voltage at this node is proportional to the circulating
current in the transmitter resonant tank (see Figure 8).
The LTC4125EUFD monitors the FB pin and when a valid
exit condition is found, stops incrementing the PTH VDAC.
The PTH VDAC is held at the detection level for the rest
of the sweep cycle. Some exit conditions are adjustable
by the user, and some are proprietary and not adjustable.
As load power requirements may change or foreign ob-
jects may enter the WPT transfer field, the LTC4125EUFD
periodically repeats the sweep as described above. Several
of the components of the sweep period are adjustable,
but the DC2330A sets the overall sweep period to about
3.7s (see Figure 9).
The AutoResonant detect circuity will shift the transmitter
frequency for some fault conditions, particularly Foreign
Object Detection (FOD).
4
dc2386aabfa
DEMO MANUAL
DC2386A-A/DC2386A-B
THEORY OF OPERATION
Figure 6. Coil Side of Transmit Coil, LT
X
Figure 7. Backside of Transmit Coil, LT
X
Figure 8. FB
∝
I(LT
X
), Lt. Blue = LTC4125.FB, Grn. = I(LT
X
)
Figure 9. Dk. Blue = V(PTH), Lt. Blue = LTC4125.FB,
Pk. = V(PROG), Grn. = LTC4120.IN
dc2386aabfa
5
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