Linear Technology LTM2886 Quick setup guide

1
dc1790af
DEMO MANUAL DC1790A
Description
LTM2886
SPI/Digital or I2C µModule Isolator with
Fixed ±5V and Adjustable 5V Regulated Power
Demonstration circuit 1790A is a serialperipheral interface
bus (SPI) or inter-IC bus (I2C) µModule
™
isolator with
fixed ±5V and adjustable 5V regulated power featuring the
LT M
®
2886. 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 single external supply on
VCC. The part generates output voltages on VCC2, which L, LT, LTC, LTM, µModule, 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
operAting principles
may be adjusted by an external programming resistor, and
fixed voltages on V+and V–. It communicates all neces-
sary 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
(TA= 25°C)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VCC Input Supply Range LTM2886-5 4.5 5 5.5 V
LTM2886-3 3.0 3 3.6 V
VCC2 Regulated Output Voltage 4.75 5 5.25 V
Adjustable Output Voltage Range 3.0 5.5 V
Current Limit 100 mA
V+Regulated Output Voltage 4.75 5 5.25 V
Current Limit 100 mA
V–Regulated Output Voltage –4.75 –5 –5.25 V
Current Limit 100 mA
fMAX Maximum Data Rate DI1 →O1, Ix →DOx, CL= 15pF 20 MHz
LTM2886-S, Bidirectional Communication
LTM2886-S, Unidirectional Communication
4
8
MHz
MHz
LTM2886-I 400 kHz
VIORM Maximum Working Insulation Voltage GND to GND2 560 VDC
400 VRMS
Common Mode Transient Immunity 30 kV/µs
The LTM2886 contains an isolated DC/DC conversion
system, including a secondary quadrupler, with multiple
LDOs to deliver power to the three output voltage rails
from VCC. Isolation is maintained by the separation of
GND and GND2 where significant operating voltages and
transients can exist without affecting the operation of the
LTM2886. The logic side ON pin enables or shuts down the
LTM2886. All logic side signals are referenced to the logic
supply pin VL. The LTM2886 is available in two data bus
configurations, SPI (–S) or I2C (–I), and with two input
voltage ranges, 3.0 to 3.6 volts (–3) or 4.5 to 5.5 volts (–5).

2
dc1790af
DEMO MANUAL DC1790A
SPI signaling is controlled by the logic inputs CS, SDI,
and SCK. SDOE controls the SDO output and is normally
connected to CS. The corresponding isolated side output
signals are CS2, SDI2, and SCK2. SDO2 is the isolated
side SPI data input. All of the SPI communication channels
may be used as generic digital I/O.
I2C signaling is controlled by the logic inputs SDA and
SCL, corresponding to SDA2 and SCL2 on the isolated
side. The SCL channel is unidirectional supporting master
mode only I2C communication. SCL2 output is standard
CMOS push-pull drive. SDA signaling is bidirectional,
and includes an internal current source pull-up on SDA2
supporting up to 200pF of load capacitance.
Demo circuit 1790A is available in four configurations
supporting all versions of the LTM2886. Table 1 details
the demo circuit configurations.
Table 1.
DEMO CIRCUIT INPUT VOLTAGE COMMUNICATION
DC1790A-A 3.0V to 3.6V SPI/Digital
DC1790A-B 4.5V to 5.5V SPI/Digital
DC1790A-C 3.0V to 3.6V I2C
DC1790A-D 4.5V to 5.5V I2C
The demo circuit has been designed and optimized for low
RF emissions. To this end some features of the LTM2886
are not available for evaluation on the demo circuit. The
logic supply voltage VLis tied to VCC on the demo circuit,
and the ON pin is not available on the input pin header,
but may be controlled by jumper JP1. EMI mitigation
techniques used include the following.
1. Four layer PCB, allowing for isolated side to logic side
“bridge” capacitor. The bridge capacitor is formed be-
tween an inner layer of floating copper which overlaps
the logic side and isolated side ground planes. This
structure creates two series capacitors, each with
approximately .008” of insulation, supporting the full
dielectric withstand rating of 2500VRMS. The bridge
capacitor provides a low impedance return path for
injected currents due to parasitic capacitances of the
LTM2886’s signal and power isolating elements.
2. Discrete bridge capacitors (C3, C4) mounted between
GND2 and GND. The discrete capacitors provide ad-
ditional attenuation at frequencies below 400MHz.
Capacitors are safety rated type Y2, manufactured by
Murata, part number GA342QR7GF471KW01L.
3. Board/ground plane size has been minimized. This
reduces the dipole antenna formed between the logic
side and isolated side ground planes.
4. Top signal routing and ground floods have been opti-
mized to reduce signal loops, minimizing differential
mode radiation.
5. Common mode filtering is integrated into the input and
output pin headers. Filtering helps to reduce emissions
caused by conducted noise and minimizes the effects
of cabling to common mode emissions.
6. A combination of low ESL and high ESR decoupling is
used. A low ESL ceramic capacitor is located close to
the moduleminimizing highfrequency noiseconduction.
A high ESR tantalum capacitor is included to minimize
board resonances and prevent voltage spikes due to
hot plugging of the supply voltage.
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”.
operAting principles

3
dc1790af
DEMO MANUAL DC1790A
operAting principles
Figure 1. DC1790A Radiated Emissions
LTM2886 Low EMI Demo Board Radiated Emissions
The demo circuit includes provisions for programming
the VCC2 voltage rail. Resistor R5 allows the VCC2 power
rail to be reduced from its nominal operating voltage of
5V. The formula presented in Table 2 allows selection of
the appropriate resistor value.
Table 2.
VOLTAGE RAIL RESISTOR TO REDUCE OUTPUT
VCC2 R5 = 61.9k • (VCC2–1.22)/(5–VCC2)

4
dc1790af
DEMO MANUAL DC1790A
TECHNOLOGY
VIN
– +
Figure 2. Demo Board Setup
qUick stArt proceDUre
Demonstration circuit 1790A is easy to set up and evalu-
ate the performance of the LTM2886. 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. Install JP1 in the ON (default) position.
2. With power off, connect the input power supply to VCC
and GND on pin header J1.
3. Turn on the power at the input.
NOTE: Make sure that the input voltage does not exceed 6V.
4. Check for the proper output voltages. VCC2 = 5V,
V+= 5V, and V–= –5V on pin header J2.
5. Once the proper output voltages are established, con-
nect signals to J1 and J2 pin headers as appropriate.
The header pin names and locations are detailed on the
demo board silkscreen below the pin headers.

5
dc1790af
DEMO MANUAL DC1790A
pcB lAYoUt
Layer 1. Top Layer
Layer 2. Ground Plane

6
dc1790af
DEMO MANUAL DC1790A
Layer 3. Signal Layer
Layer 4. Bottom Layer
pcB lAYoUt

7
dc1790af
DEMO MANUAL DC1790A
pArts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 U1 –A
–B
–C
–D
I.C., LTM2886CY-3S
I.C., LTM2886CY-5S
I.C., LTM2886CY-3I
I.C., LTM2886CY-5I
LINEAR LTM2886CY-3S#PBF
LINEAR LTM2886CY-5S#PBF
LINEAR LTM2886CY-3I#PBF
LINEAR LTM2886CY-5I#PBF
Hardware/Components (For Demo Board Only)
2 1 C1 CAP., TANT 10μF 10V 20% TAJA AVX TAJA106M010RNJ
3 1 C2 CAP., CER 1μF 10V 20% 0508 MURATA LLL219R71A105MA01L
4 2 C3, C4 CAP., CER 470pF 250Vac 10% 1808 MURATA GA342QR7GF471KW01L
5 2 J1, J2 0.1” DOUBLE ROW HEADER, 5 ×2 PIN SAMTEC TSW-105-22-G-D
6 2 J1, J2 0.1” FERRITE PLATE, 5 ×2 HOLE FAIR RITE 2644247101
7 1 JP1 2mm SINGLE ROW HEADER, 3-PIN SAMTEC TMM-103-02-L-S
8 1 JP1 SHUNT SAMTEC 2SN-BK-G
9 1 R1 –C
–D
RES., CHIP 10kΩ 1% 0805
RES., CHIP 10kΩ 1% 0805
YAGEO RC0805FR-0710KL
YAGEO RC0805FR-0710KL
10 1 R2 –C
–D
RES., CHIP 10kΩ 1% 0805
RES., CHIP 10kΩ 1% 0805
YAGEO RC0805FR-0710KL
YAGEO RC0805FR-0710KL
11 1 R3 –C
–D
RES., CHIP 0 0805
RES., CHIP 0 0805
YAGEO RC0805FR-070RL
YAGEO RC0805FR-070RL
12 1 R4 –A
–B
RES., CHIP 0 0805
RES., CHIP 0 0805
YAGEO RC0805FR-070RL
YAGEO RC0805FR-070RL

8
dc1790af
DEMO MANUAL DC1790A
scheMAtic DiAgrAM
GND2
C3 470pF 1808
C4 470pF 1808
PCB SUBSTRATE 'BRIDGE' CAPACITOR, 20pF TOTAL TOP COPPER TOP COPPER
INNER LAYER 1
R5 OPEN
C2
1uF
0508
JP1
ON
C1 10uF 3216
1
2
3
4
56
78
9
10
J1
R1 OPEN
R2 OPEN
12
3 4 56
78
910
J2
VCC VCC
DI1
DNC
DO1
GND GND
SDA
SCL
DO2
LTM2886-I
VCC VCC
CSB DO2 DO1
GND GND
SDI
SCK
SDO
LTM2886-S
V-
VCC2
SDA2
SCL2
I2
V+
GND2
O1
DNC
I1
LTM2886-I
V-
VCC2
SDI2
SCK2
SDO2
V+
GND2
CS2B
I2 I1
LTM2886-S
R3 OPEN
R4 0
OFF
-11ST PROTOTYPE KEITH B. 12-2-10
HGFEDCBA HGFEDCBA
1 2 3 4 5 6 7
1 2 3 4 5 6 7
TITLE: SCHEMATIC SIZE IC NO. REV.
DATE: SHEET OF
APPROVALS
SCALE = NONE
CUSTOMER NOTICE
Wednesday, August 10, 2011
1
SPI/DIGITAL OR I2C uMODULE ISOLATOR, LOW EMI
KEITH B.
1 1
LTM2886CY-3S/-5S
DEMO CIRCUIT 1790A
ETADDEVORPPAVEROCE
REVISION HISTORY
DESCRIPTION
1630 McCarthy Blvd.
Milpitas, CA 95035 Phone: [phone] Fax: [phone] www.linear.com
LTC CONFIDENTIAL
FOR CUSTOMER
USE ONLY
THIS CIRCUIT IS PROPRIETARY TO
LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT
TO DESIGN A CIRCUIT THAT MEETS CUSTOMER -
SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMERS RESPONSIBILITY TO VERIFY
PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND
PRINTED CIRCUIT LAYOUT MAY SIGNIFICANTLY
AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
TECHNOLOGY
PCB DES. APP ENG.KEITH B.
INPUT CONNECTOR OUTPUT CONNECTOR
N/A
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE IN OHMS, 0805.
ALL CAPACITORS ARE IN MICROFARADS, 0805.
ASSY U1 VCC
LTM2886CY-3S
-A 3.0V - 3.6V
LTM2886CY-5S-B 4.5V - 5.5V
*
VCC
SCK
A3
CS
A5
V+ L8
SDI
A4
V- L7
DO2
A2
SDOE
A6 ON
A7
VL
A8 VCC
B8
SDI2 L4
CS2L5
AVCC2K6
VCC2L6
SDO
A1
DO1
B1
GND
B2
SCK2L3
I2 L2
SDO2L1
I1 K1
GND2K4
U1 LTM2886CY-*
DC1790A-A/B

9
dc1790af
DEMO MANUAL DC1790A
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
DC1790A-C/D
GND2
SCL
A3
DI1
A5
V+ L8
SDA
A4
V- L7
DNC
A2
GND1
A6 ON A7
VL
A8 VCC
B8
SDA2L4
O1 L5
AVCC2K6
VCC2L6
DO2
A1
DO1
B1
GND
B3
SCL2L3
DNCL2
I2 L1
I1 K1
GND2K4
U1 LTM2886CY-*
C3 470pF 1808
C4 470pF 1808
PCB SUBSTRATE 'BRIDGE' CAPACITOR, 20pF TOTAL TOP COPPER TOP COPPER
INNER LAYER 1
R5 OPEN
C2
1uF
0508
JP1
ON
C1 10uF 3216
1
2
3
4
56
78
9
10
J1
R1 10k
R2 10k
12
3 4 56
78
910
J2
VCC VCC
DI1
DNC
DO1
GND GND
SDA
SCL
DO2
LTM2886-I
VCC VCC
CSB DO2 DO1
GND GND
SDI
SCK
SDO
LTM2886-S
V-
VCC2
SDA2
SCL2
I2
V+
GND2
O1
DNC
I1
LTM2886-I
V-
VCC2
SDI2
SCK2
SDO2
V+
GND2
CS2B
I2 I1
LTM2886-S
R3 0
R4 OPEN
OFF
-11ST PROTOTYPE KEITH B. 12-2-10
HGFEDCBA HGFEDCBA
1 2 3 4 5 6 7
1 2 3 4 5 6 7
TITLE: SCHEMATIC SIZE IC NO. REV.
DATE: SHEET OF
APPROVALS
SCALE = NONE
CUSTOMER NOTICE
Wednesday, July 27, 2011
1
SPI/DIGITAL OR I2C uMODULE ISOLATOR, LOW EMI
KEITH B.
1 1
LTM2886CY-3I/-5I
DEMO CIRCUIT 1790A
ETADDEVORPPAVEROCE
REVISION HISTORY
DESCRIPTION
1630 McCarthy Blvd.
Milpitas, CA 95035 Phone: [phone] Fax: [phone] www.linear.com
LTC CONFIDENTIAL
FOR CUSTOMER
USE ONLY
THIS CIRCUIT IS PROPRIETARY TO
LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT
TO DESIGN A CIRCUIT THAT MEETS CUSTOMER -
SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMERS RESPONSIBILITY TO VERIFY
PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND
PRINTED CIRCUIT LAYOUT MAY SIGNIFICANTLY
AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
TECHNOLOGY
PCB DES. APP ENG.KEITH B.
INPUT CONNECTOR OUTPUT CONNECTOR
N/A
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE IN OHMS, 0805.
ALL CAPACITORS ARE IN MICROFARADS, 0805.
ASSY U1 VCC R1 R2 R3 R4
LTM2886CY-3I-C 3.0V - 3.6V 10K 10K 0 OPT
LTM2886CY-5I
-D 4.5V - 5.5V 10K 10K 0 OPT
*
VCC

10
dc1790af
DEMO MANUAL DC1790A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2014
LT 0214 • 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

Mouser Electronics
Authorized Distributor
Click to View Pricing, Inventory, Delivery & Lifecycle Information:
Analog Devices Inc.:
DC1790A-B DC1790A-C DC1790A-A DC1790A-D