Linear Technology DC2181A Series Quick setup guide

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DEMO MANUAL
DC2181A-A/B
Description
LTC4120EUD
Wireless Power Receiver
and 400mA Buck Battery Charger
Demonstration circuit 2181 is an LT C
®
4120EUD demon-
stration board. The DC2181 is used with the DC1968A
wirelesspowertransmitterorthePowerByProxiProxiPoint
transmitter (both available separately). Either can deliver
2W to the DC2181, with up to 10mm spacing between
the transmitter and the receive coil. The basic transmitter
doesn’tsupportforeignmetalobjectdetection. Transmitters
available separately. See last page for details.
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.
performance summary
BoarD photo
FEATURED PART
DC2181A-A LTC4120EUD-4.2 (Fixed Output)
DC2181A-B LTC4120EUD (Adjustable Output)
Design files for this circuit board are available at
http://www.linear.com/demo/DC2181A
Specifications are at TA= 25°C
Figure 1. DC2181 Wireless Power Receiver Demo Board
Figure 2. DC1968A Wireless Power Basic Transmitter Demo Board Figure 3. PowerByProxi ProxiPoint Transmitter
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
HVIN DC1968A High Voltage Input Voltage Range IHVIN ≤ 500mA at HVIN = 8V 8 38 V
VCC DC1968A VCC Input Range IVCC = 0 ~ 700mA 4.75 5.25 V
V(BAT) DC2181A BAT Pin Voltage R9 = 1.40MΩ, R10 = 1.05MΩ 2.5 4.25 V
I(BAT) DC2181A BAT Pin Current V(BAT) = 3.7V, DC1967A(R5) = 3.01kΩ, All Bar
Graph LEDs on.
370 380 390 mA
OR OR
NOTE: These boards
are not included with
DC2181 and must be
ordered separately.
Seelastpagefordetails.

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DEMO MANUAL
DC2181A-A/B
assemBly test proceDure
For the proper measurement equipment setup and jumper
settings refer to Figure 6a, if you are using the DC1968A
wireless power basic transmitter, or Figure 5a, if you are
usingthe PowerByProxi ProxiPoint transmitter. Please fol-
low the checkout procedure, below, to familiarize yourself
with the DC2181 demo board.
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 VCC or VIN and GND terminals. See Figure 4 for
proper scope probe technique.
1. Connect power to the transmitter. For the DC1968A
basic transmitter set PS1 to 5V, and turn on. For the
PowerByProxi ProxiPoint transmitter, plug in the
power supply that came with the transmitter.
2. Set PS2 to 3.6V, and turn the supply on. PS2 is the
battery emulator battery voltage. The purpose of the
3.6Ω is to make PS2 into a bipolar supply. Most power
suppliescanonly sourcecurrent not sink current,bipolar
supplies can do both. A bipolar supply is necessary for a
battery emulator, as it must absorb the current coming
from the charger. By placing a 3.6Ω resistor in parallel
with a normal supply, the supply can absorb up to 1A,
at 3.6V.
3. Place the DC2181A receive board on the transmitter as
shown in Figure 5c, if you are using the PowerByProxi
ProxiPoint transmitter. Or as shown in Figure 6c, if
using the DC1968A. Note: for the ProxiPoint transmit-
ter, the LED the ProxiPoint transmitter should change
from green to solid red. If the LED turns blinking red,
please remove the DC2181A board, wait until the LED
turns green, and once again place the DC2181 on the
transmitter. If the ProxiPoint transmitter LED does not
change to solid red on the second try, please contact
your FAE.
4. The green bar graph LEDs on the DC2181 demo board
should light. Observe AM1, there is an additional 10mA
flowing from the BAT into the bar graph LEDs. Please
ensure that VM1 measures less than 4V. If not lower
PS2 until it does.
The bar graph LEDs indicate the percent of programmed
charge current flowing into the battery. They do so by
monitoring the PROG voltage. PROG will be 1V, at full
programmed charge current.
If you lower the battery emulator voltage, by lowering
PS2, until VM1 reads approximately 2.9V, you will see
the bar graph drop to 10%. This is the trickle current,
which is set to 10% of the programmed charge current.
5. Test is complete.
Figure 4. Proper Measurement Technique for Measuring Ripple

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DEMO MANUAL
DC2181A-A/B
Figure 5a. DC2181A-A/B Wireless Power Demo Board Connection
Figure 5b. PowerByProxi’s ProxiPoint Transmitter
Figure 5c. DC2181A-A/B Wireless Power Demo Board Mounted on PowerByProxi’s ProxiPoint Transmitter
Note: All connections from equipment should be Kelvin connected directly to the
board pins which they are connected on this diagram and any input or output leads
should be twisted pair.
assemBly test proceDure
3.6Ω3.6V POWER SUPPLY
1A
VM1
AM1
PS1 –
+
–
+
V
–+
A

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DEMO MANUAL
DC2181A-A/B
assemBly test proceDure
Figure 6a. DC2181A-A/B Wireless Power Demo Board Connection
Figure 6b. DC1968A Wireless Power Basic Transmitter Connection
Figure 6c. DC2181A-A/B Wireless Power Demo Board Mounted on
DC1968A Wireless Power Basic Transmitter
Note: All connections from equipment should be Kelvin connected directly to the
board pins which they are connected on this diagram and any input or output leads
should be twisted pair.
3.6Ω3.6V BIPOLAR SUPPLY
1A
VM1
AM1
PS2 –
+
–
+
V
–+
A
5V POWER SUPPLY
1A
PS1
–
+

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DEMO MANUAL
DC2181A-A/B
theory of operation
Figure 7. DC1968A Basic Transmitter
The DC2181A demo board demonstrates operation of a
doubletuned magnetically coupled resonant power transfer
circuit. The DC2181A demo Board must be used in con-
junction with either the DC1968A wireless power basic
transmitter or the PowerByProxi ProxiPoint transmitter.
For theory of operation of the PowerByProxi ProxiPoint
transmitter, please refer to the ProxiPoint documentation.
DC1968A – Basic Transmitter
The DC1968A basic transmitter is used to transmit wire-
less power and is used in conjunction with the DC2181A
wireless power receiver board featuring the LTC4120.
The DC1968A is configured as a current fed astable multi-
vibrator, with oscillation frequency set by a resonant tank.
The DC1968A basic transmitter is set to 130kHz operation
and the DC1967A LTC4120 demonstration board resonant
frequency is 127kHz with DHC enabled and 140kHz with
DHC disabled. For the DC1968A basic transmitter the
resonant components are the 2X0.15µF PPE film capaci-
tors (Cx1 and Cx2) and the 5.0µH(Lx) transmit coil (see
Schematic: Basic Inductive Transmitter with Pre-
Regulator). This gives a resonant frequency of 129.95kHz.
The tolerance on the transmit coil and resonant capacitors
is ±2%, or 2.6kHz. Inductors L1 and L2 are used to make
the resonant structure current fed.
The current fed topology makes the peak-to-peak voltage
on the resonant tank equal to 2πVCC. VCC is 5V, so the
peak-to-peak tank voltage is 31.5V, see Figure 7.
2µs/DIV
VCx-Cy
20V/DIV
VCx
10V/DIV
VCy
10V/DIV
DC2181A F07
The blue and green traces are the drains of the transmit-
ter MOSFETs M1 and M2 (see Schematic: Basic Inductive
T
ransmitter with Pre-Regulator), respectively. The red
trace is the difference (VCX – VCY) of those two nodes,
and shows that the resonant tank is producing a sine
wave. The peak-to-peak voltage of 2πVCC = 31.5V, results
from the current fed topology. This in turn determines
the breakdown of the MOSFETs and diodes D2 and D3.
To increase transmit power by raising VCC, you must also
change M1, M2, D2 and D3, to reflect the higher voltages
on the CXand CYnodes.
The magnitude of the magnetic field is directly proportional
to the current in the transmit coil. For a resonant system
this current is Q times the input current. So the higher the
Q the larger the magnetic field. Therefore the transmit coil
is constructed with Litz wire, and the resonant capacitors
are very low dissipation PPS film capacitors. This leads
to a Q of approximately 10 at 130kHz, and a circulating
current of approximately 6AP-P, at full load.
DC2181 – Wireless Power Receiver Board Featuring
the LTC4120
The DC2181 LTC4120 wireless power receiver IC imple-
ments dynamic
harmonization control (DHC), which tunes
or detunes the receive circuit to receive more or less
power as needed. The primary receive tank is composed
of AE1, and C2S, although it must be noted that C2S is AC
grounded through C5, the LTC4120 decoupling capacitor,
to be in parallel with AE1. C2S also serves to tap power
off the resonant circuit and send it to the LTC4120, (see
Schematic: 400mA Wireless Synchronous Buck Battery
Charger).

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DEMO MANUAL
DC2181A-A/B
theory of operation
The waveforms in Figure 8 were captured at a transmit-
to-receive gap of 8mm. The blue trace is the waveform at
the CXpin of the receiver board (see Schematic: 400mA
Wireless Synchronous Buck Battery Charger), and the
red trace is the charge current into the battery. Although
the transmit waveform is a sine wave, the series-parallel
connection of the secondary resonant circuit does not
yield a sine wave, and this waveform is correct. The charge
current into the battery has an average of ≈ 400mA, for a
delivered power of 1.5W(VBAT = 3.7V). However, 10mA
has been diverted to the charge LEDs, for a net battery
charge current of 390mA. The ripple on the charge current
is synchronous to the transmit waveform.
Summary
The LTC4120 wireless power receiver IC adjusts the
receiver resonant frequency to keep the system from
transferring too much power when the coupling is high
between transmit and receive coils. The LTC4120 wireless
power receiver IC increases power transfer when power
transfer is insufficient. This is accomplished by switching
capacitors into the resonant circuit using the DHC pin. This
gives a much wider operating transmit distance.
Figure 9 shows VIN to the LTC4120 and the battery charge
current. The blue trace is the charge current into the bat-
tery, and the red trace is the voltage at VIN on the receiver
board. VIN is about 25V, while the LTC4120 delivers 1.5W
at a distance of 8mm, to the battery. There is negligible
transmit frequency ripple on VIN, and the voltage is well
above the 14V DHC voltage. This indicates that the input
rectifiers are operating in peak detect mode, and that DHC
is inactive.
Figure 9. DC2181A Receiver
2µs/DIV
VIN TO GND
5V/DIV
DC2181A F09
IBAT
100mA/DIV
VBAT = 3.7V
Figure 8. DC2181A Receiver Board
2µs/DIV
IBAT
VBAT = 3.7V
100µA/DIV
DC2181A F08
Cx TO GND
20V/DIV
DHC
When VIN is above 14V, the DHC pin is open and C2P
doesn’t enhance the energy transfer; this is the detuned
state, and the resonant frequency of the receive tank is
142kHz.WhenVIN fallsbelow 14V,the DHCpin is grounded
putting C2P in parallel with both C2S and AE1 thus chang-
ing the resonant frequency to 127.4kHz. When the receiver
is tuned at 127.4kHz and drawing significant power, the
transmit frequency is pulled down to 127kHz. So, at full
power the system is now a double-tuned resonant circuit.
Figure 10 shows approximate power transfer vs distance
between transmitter and receiver. Note the minimum
clearance. The minimum is needed to avoid exceeding
the maximum input voltage.

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DEMO MANUAL
DC2181A-A/B
theory of operation
AE1, the Receive Antenna
One of the main differences between the DC1967A and the
DC2181 demo boards, is that the wireless power receive
antenna is separate for the DC2181 demo board.
Several antennas were tested, with the criteria of pass-
ing 2.5W at 8mm spacing. The following table lists the
antennas that passed successfully:
MANUFACTURER CONSTRUCTION MFG PART NUMBER
TDK Ferrite on PCB B67410-A0223-X195
Inter-Technical Ferrite on PCB L41200R01
Inter-Technical Ferrite on PCB L41200R02*
Inter-Technical Litz on Ferrite L41200R03
Inter-Technical Litz on Ferrite L41200R04
Inter-Technical Ferrite on PCB L41200R05
TDK Wire on Ferrite WR282830-37M8-LR4
Würth Wire on Ferrite 760308101303
*AE1 wireless power receive antenna shipped with DC2181
The manufacturers can be contacted at:
Inter-Technical www.inter-technical.com, search for LTC4120
TDK www.tdk.components.com
Würth http://katalog.we-online.de/pbs/
datasheet/760308101303.pdf
AE1 is physically mounted with double sided tape, as well
as the electrical connection pins. Removing AE1 is likely
to damage the ferrite on the backside of the antenna. Only
remove AE1 when you have the a suitable replacement
at hand.
Figure 10. Power Transfer vs Axial Distance and Misalignment
17mm
Full Power
±1mm
½ Power
±1mm
½ Power
Envelope
18mm
13mm
15mm
2mm
3mm
4mm
5mm
6mm
7mm
8mm
9mm
Full Power
Envelope DC1967A-B with
25mm Receive
Antenna
DC2181A F10
Transmit Antenna
1mm Minimum Clearance

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DEMO MANUAL
DC2181A-A/B
parts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
DC2181A General Bill of Materials
DC2181A Required Circuit Components
1 1 AE1 RECEIVE ANTENNA INTER-TECHNICAL, L41200R02
2 2 C2S1, C2P1 CAP, CHIP, C0G, 0.0047μF, ±5%, 50V, 0805 MURATA, GRM2165C1H472JA01D
3 1 C2P2 CAP, CHIP, C0G, 0.0018μF, ±5%, 50V, 0603 KEMET, C0603C182J5GAC7533
4 1 C2S2 CAP, CHIP, C0G, 0.022μF, ±5%, 50V, 0805 MURATA, GRM21B5C1H223JA01L
5 1 C1 CAP, CHIP, X5R, 10μF, ±20%, 16V, 0805 TDK, C2012X5R1C106K
6 1 C2 CAP, CHIP, X5R, 47μF, ±10%, 16V, 1210 MURATA, GRM32ER61C476KE15L
7 1 C3 CAP, CHIP, X7R, 0.01μF, ±10%, 50V, 0603 TDK, C1608X7R1H103K
8 1 C4 CAP, CHIP, X5R, 2.2μF, ±20%, 6.3V, 0402 MURATA, GRM155R60J225ME15D
9 1 C5 CAP, CHIP, X7S, 10μF, ±20%, 50V, 1210 TDK, C3225X7S1H106M
10 3 D1, D2, D3 DIODE, SCHOTTKY, 40V, 2A, PowerDI123 DIODES, DFLS240L-7
11 1 L1 IND, SMT,15μH, 260mΩ, ±20%, 0.86A, 4mm × 4mm COILCRAFT, LPS4018-153ML
12 1 R1 RES, CHIP, 1.40M, ±1%, 1/16W, 0402 VISHAY, CRCW04021M40FKED
13 1 R2 RES, CHIP, 412kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402412KFKED
14 2 R3, R7 RES, CHIP, 10kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040210K0FKED
15 1 R5 RES, CHIP, 3.01kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW04023K01FKED
16 1 R36 RES, CHIP, 0Ω JUMPER, 1/16W, 0402 VISHAY, CRCW04020000Z0ED
Additional Demo Board Circuit Components
1 3 C6, C8, C9 CAP, CHIP, X7R, 0.01μF, ±10%, 25V, 0402 TDK, C1005X7R1E103K
2 2 C7, C10 CAP, CHIP, X5R, 1μF, ±10%, 16V, 0402 TDK, C1005X5R1C105K
3 1 D4 DIODE, ZENER, 39V, ±5%, 1W, PowerDI123 DIODES, DFLZ39
4 8 D5, D6, D7, D8, D9, D10,
D11, D12
DIODE, LED, GREEN, 0603 LITE-ON, LTST-C193KGKT-5A
5 1 R4 RES, CHIP, 2kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04022K00JNED
6 2 R11, R12 RES, CHIP, 100kΩ, ±5%,1/16W, 0402 VISHAY, CRCW0402100KJNED
7 1 R13 RES, CHIP, 10kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW040210K0JNED
8 2 R14, R35 RES, CHIP, 432Ω, ±1%, 1/16W, 0402 VISHAY, CRCW0402432RFKED
9 2 R15, R33 RES, CHIP, 22.6kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040222K6FKED
10 1 R16 RES, CHIP, 34.8kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040234K8FKED
11 7 R17, R18, R19, R20,
R21, R22, R23
RES, CHIP, 100kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402100KFKED
12 1 R24 RES, CHIP, 49.9kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040249K9FKED
13 8 R25 TO R32 RES, CHIP, 1kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04021K00JNED
14 1 R34 RES, CHIP, 787kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402787KFKED
15 2 R6, R38 RES, CHIP, 0Ω JUMPER, 1/16W, 0402 VISHAY, CRCW04020000Z0ED
16 0 R8-OPT, R37-OPT RES, CHIP, 0Ω JUMPER, 1/16W, 0402 VISHAY, CRCW04020000Z0ED
17 2 U2, U3 ULTRALOW POWER QUAD COMPARATORS WITH
REFERENCE, 5mm × 4mm DFN16
LINEAR TECHNOLOGY, LTC1445CDHD

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DEMO MANUAL
DC2181A-A/B
parts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
DC2181A-A Required Circuit Components
1 0 R9 NO LOAD. SMD 0402
2 1 R10 RES, CHIP, 0Ω JUMPER, 1/16W, 0402 VISHAY, CRCW04020000Z0ED
3 1 U1 400mA WIRELESS SYNCHRONOUS BUCK BATTERY
CHARGER, 3mm × 3mm QFN16
LINEAR TECHNOLOGY, LTC4120EUD-4.2
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
DC2181A-B Required Circuit Components
1 1 R9 RES, CHIP, 1.40M, ±1%, 1/16W, 0402 VISHAY, CRCW04021M40FKED
2 1 R10 RES, CHIP, 1.05M, ±1%, 1/16W, 0402 VISHAY, CRCW04021M05FKED
3 1 U1 400mA WIRELESS SYNCHRONOUS BUCK BATTERY
CHARGER, 3mm × 3mm QFN16
LINEAR TECHNOLOGY, LTC4120EUD
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Hardware: For Demo Board Only
1 4 E3, E4, E7, E8 TURRET, 0.091˝ MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 E1, E2, E5, E6 TURRET, 0.061˝ MILL-MAX, 2308-2-00-80-00-00-07-0
3 2 J1, J2 HEADER, 1PIN, 0.020˝ × 0.020˝ SAMTEC, TMM-101-02-L-S
4 0 J3-OPT CONN, 3 PIN POLARIZED HIROSE, DF3-3P-2DSA
5 2 BP1, BP2, BP3, BP4 CLEAR 0.200˝ × 0.440˝ BUMPER KEYSTONE, 785-C
6 0.00058 3M, 0.5IN WIDE, 1/16IN THICK, DOUBLE SIDED FOAM
TAPE, 0.75IN × 0.50IN PIECE
3M, 4466
7 4 STAND-OFF, NYLON, 0.375˝ KEYSTONE, 8832

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DEMO MANUAL
DC2181A-A/B
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
DC1968A Bill of Materials
DC1968A Required Circuit Components
1 1 CX1, CX2 CAP, CHIP, PPS, 0.15µF, ±2%, 50V, 6mm × 4.1mm PANASONIC, ECHU1H154GX9
2 2 C4, C5 CAP, CHIP, X7R, 0.01µF, ±10%, 50V, 0402 MURATA, GRM155R71H103KA88D
3 1 C6 CAP, CHIP, X7R, 4.7µF, ±10%, 50V, 0402 MURATA, GRM31CR71H475KA12L
4 1 C7 CAP, CHIP, X5R, 0.068µF, ±10%, 50V, 0603 MURATA, GRM188R71H683K
5 1 C8 CAP, CHIP, C0G, 330pF, ±5%, 50V, 0402 TDK, C1005COG1H331J
6 1 C9 CAP, CHIP, X7R, 0.47µF, ±10%, 25V, 0603 MURATA, GRM188R71E474K
7 1 C10 CAP, CHIP, X5R, 22µF, ±20%, 6.3V, 0805 TAIYO-YUDEN, JMK212BJ226MG
8 2 D1, D4 DIODE, ZENER, 16V, 350mV, SOT23 DIODES, BZX84C16
9 2 D2, D3 DIODE, SCHOTTKY, 40V, 1A, 2DSN ON SEMICONDUCTOR, NSR10F40NXT5G
10 1 D5 DIODE, SCHOTTKY, 40V, 2A, PowerDI123 DIODES, DFLS240L
11 2 L1, L2 IND, SMT, 68µH, 0.41A, 0.40Ω, ±20%, 5mm × 5mm TDK, VLCF5028T-680MR40-2
12 1 L3 IND, SMT, 4.7µH, 1.6A, 0.125Ω, ±20%, 4mm × 4mm COILCRAFT, LPS4018-472M
13 1 Lx TRANSMIT COIL TDK, WT-505060-8K2-LT
14 2 M1, M2 MOSFET, SMT, N-CHANNEL, 60V, 11mΩ, SO8 VISHAY, Si4108DY-T1-GE3
15 1 M3 MOSFET, SMT, P-CHANNEL, –12V, 32mΩ, SOT23 VISHAY, Si2333DS
16 1 M4 MOSFET, SMT, N-CHANNEL, 60V, 7.5Ω, 115mA, SOT23 ON SEMI, 2N7002L
17 2 R1, R2 RES, CHIP, 100Ω, ±5%, 1/16W, 0402 VISHAY, CRCW0402100RJNED
18 2 R3, R8 RES, CHIP, 150kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW0402150JNED
19 1 R4 RES, CHIP, 40.2kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040240K2FKED
20 1 R5 RES, CHIP, 20kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040220K0FKED
21 2 R6, R10 RES, CHIP, 100kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402100KFKED
22 1 R7 RES, CHIP, 536kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402536KFKED
23 1 U1 LT3480EDD, PMIC 38V, 2A, 2.4MHz STEP-DOWN SWITCHING
REGULATOR WITH 70µA QUIESCENT CURRENT
LINEAR TECHNOLOGY, LT3480EDD
Additional Demo Board Circuit Components
1 0 CX3-OPT, CX4-OPT CAP, PPS, 0.15µF, 2.5%, 63VAC, MKS02 WIMA, MKS0D031500D00JSSD
2 1 D6 LED, GREEN, 0603 LITE-ON, LTST-C190KGKT
3 1 R9 RES, CHIP, 1kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04021K00JNED
Hardware: For Demo Board Only
1 6 E1 TO E6 TURRET, 0.09 DIA MILL-MAX, 2501-2-00-80-00-00-07-0
2 4 STAND-OFF, NYLON, 0.375˝ KEYSTONE, 8832
parts list