DC1789A - ANALOG DEVICES - Datasheet.Directory

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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

5.25

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.

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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)

dBµV/m

–6

–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

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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

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DEMO MANUAL DC1789A

pcB layout

Layer 1. Top Layer

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DEMO MANUAL DC1789A

Layer 2. Bottom Layer

pcB layout

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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

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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

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DEMO MANUAL DC1789A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● 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