Linear Technology DC1789A Quick setup guide

1
dc1789afa
DEMO MANUAL DC1789A
Description
LTM2884
Isolated USB Transceiver
with Isolated Power
Demonstration circuit 1789A is an isolated USB transceiver
with isolated power featuring the LT M
®
2884. The demo
circuit features an EMI optimized circuit configuration and
printed circuit board layout. All components are integrated
into the µModule
®
isolator. The demo circuit operates
from a supply on VCC and/or VBUS. The part generates
an isolated output voltage on VCC2 and communicates all
performance summary
operating principles
necessary signaling across the isolation barrier through
LTC’s isolator µModule technology.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
(TA= 25°C)
The LTM2884 contains an isolated DC/DC converter de-
livering power to VCC2 at 5V from the input supply VCC
and/or VBUS. Isolation is maintained by the separation of
GND and GND2 where significant operating voltages and
transients can exist without affecting the operation of the
LTM2884. The logic side ON pin enables or shuts down
the LTM2884. All logic side signals are referenced to the
logic supply pin VLO. The LTM2884 has two power supply
inputs, VCC and VBUS. For applications requiring more
than 200mA from VCC2, VCC must be connected to an
external supply of 8.1V to 16.5V. VBUS may be connected
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VCC Operating Supply Range (Isolated Power Input) 4.4 12 16.5 V
VBUS Operating Supply Range (USB Bus Power Input) 4.4 5 16.5 V
VCC2 Regulated Output Voltage VCC = VBUS = 4.4V, ICC2 = 200mA
VCC = 8.1V, ICC2 = 500mA
4.75
4.75
5
5
5.25
5.25
V
V
tLDR Low Speed Data Rate 1.5 Mbps
tFDR Full Speed Data Rate 12 Mbps
VIORM Maximum Working Insulation Voltage GND to GND2 560
400
VDC
VRMS
Common Mode Transient Immunity 30 kV/µs
to USB bus power or to the external supply. For applica-
tions requiring 200mA or less connect VCC and VBUS to
USB bus power.
Upstream USB signaling is controlled by the bidirectional
pins D1+and D1–. A 1.5k pull-up resistor is automatically
configured dependent upon the connected downstream
peripheral device. For full speed and low speed devices
the pull-up is asserted on D1+and D1–, respectively. The
downstream USB data pins, D2+and D2–, each have
integrated 15k pull-down resistors.
Downloaded from Arrow.com.

2
dc1789afa
DEMO MANUAL DC1789A
operating principles
Figure 1. DC1789A Radiated Emissions,
Normalized to 10m per IEC 61000-4-20
The LTM2884 includes a suspend power feature that
when enabled (high) reduces the supply current on VCC
and VBUS when the upstream USB bus is idle. However, in
this mode, if a downstream device is connected or discon-
nected from the bus or remote wake-up functionality is
configured, it will not be recognized by the LTM2884 and
relayed to the host. A resume command at the upstream
side will wake up the LTM2884 and a re-numeration by
the host will be required. If suspend power is configured
low the LTM2884 operates in a low power mode but will
respond to disconnects,reconnects, downstream wake-up
commands, or host resume commands.
The demo circuit has been designed and optimized for
low RF emissions. EMI mitigation techniques used include
the following:
1. Board/ground plane size has been minimized. This
reduces the dipole antenna formed between the logic
side and isolated side ground planes.
2. Top signal routing and ground floods have been opti-
mized to reduce signal loops, minimizing differential
mode radiation.
EMI performance is shown in Figure 1, measured using
a gigahertz transverse electromagnetic (GTEM) cell and
method detailed in IEC 61000-4-20, “Testing and Mea-
surement Techniques – Emission and Immunity Testing
in Transverse Electromagnetic Waveguides.”
FREQUENCY (MHz)
0
dBµV/m
54
12
30
6
–6
0
24
18
48
42
36
–12
–18 400100
DC1789A F01
1000300 900600 700500 800200
DC1789A
CISPR 22 CLASS B LIMIT
DETECTOR = PEAK-HOLD
RBW = 120kHz, VBW = 300kHz
SWEEP TIME = 680ms, ≥10 SWEEPS
# OF POINTS = 501
Downloaded from Arrow.com.Downloaded from Arrow.com.

3
dc1789afa
DEMO MANUAL DC1789A
Quick start proceDure
Demonstration circuit 1789A makes it easy to set up and
evaluate the performance of the LTM2884. Refer to Figure
2 for proper measurement equipment setup and follow
the procedure below.
NOTE: When measuring the input or output voltage ripple
or high speed signals, care must be taken to avoid a long
ground lead on the oscilloscope probe.
1. Place jumpers in their default positions:
JP1 VCC supply in the VBUS position
JP2 VBUS supply in the VBUS position
JP3 SUSPEND POWER in the OFF position
JP4 C2 in the OUT position
NOTE: To simulate a hub/splitter output, C2 can be
jumpered IN. The additional capacitance reduces VBUS
droop on downstream device plug-in.
2. Connect USB cable from computer to input side (J1)
of the demo board.
3. Connect computer mouse, low speed device, or USB
memory stick, typically high speed device, to output
side (J2) of demo board.
4. Verify proper operation of mouse or memory stick.
Figure 2. Demo Board Setup
MEMORY STICK
MOUSE
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

4
dc1789afa
DEMO MANUAL DC1789A
pcB layout
Layer 1. Top Layer
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

5
dc1789afa
DEMO MANUAL DC1789A
Layer 2. Bottom Layer
pcB layout
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

6
dc1789afa
DEMO MANUAL DC1789A
parts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 U1 I.C., LTM2884CY LINEAR LTM2884CY#PBF
Hardware/Components (For Demo Board Only)
2 1 C1 CAP., TANT 22F 25V 20% ‘C’ AVX TAJC226M025R
3 1 C2 CAP., TANT 100F 10V 20% ‘C’ AVX TPSC107M010R0150
4 1 J1 USB RECEPTACLE TYPE B MILL-MAX 897-43-004-90-00000
5 1 J2 USB RECEPTACLE TYPE A MILL-MAX 896-43-004-90-00000
6 3 JP1-4 0.1" SINGLE ROW HEADER, 3-PIN SAMTEC TSW-103-26-L-S
7 3 JP1-4 SHUNT SAMTEC SNT-100-BK-G
8 4 TP1-4 TESTPOINT, TURRET, 0.095 MILL-MAX 2501-2-00-80-00-00-07-0
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

7
dc1789afa
DEMO MANUAL DC1789A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
schematic Diagram
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

8
dc1789afa
DEMO MANUAL DC1789A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2013
LT 0314 REV A • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.