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DESCRIPTION
DEMO MANUAL DC1957A
LTM2892-S
SPI/Digital µModule Isolator
Demonstration circuit 1957A is a serial peripheral interface bus (SPI) or digital µModule isolator featuring the
LTM2892-S. The demo circuit operates from external supply voltages on V
CC1
, VL1, V
, and VL2. It communicates
CC2
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
and Isolator is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
all necessary signaling across the isolation barrier through
®
LTC’s Isolator™ µModule
PERFORMANCE SUMMARY
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
V
f
MAX
V
CC1
, V
L1
IORM
, V
CC2
L2
Input Supply Range 3.0 5.5 V
Logic Supply Range 1.62 5.5 V
Maximum Data Rate
Maximum Working Insulation Voltage GND1 to GND2 850 V
Common Mode Transient Immunity 50 kV/µs
technology.
Specifications are at TA = 25°C
INx → OUTx, C
SPI Bidirectional Communication
SPI Unidirectional Communication
= 15pF
L
20 MHz
4
8
600 V
MHz
MHz
RMS
DC
OPERATING PRINCIPLES
The LTM2892-S requires two to four external power supplies for operation, one for power and one for the signal
interface, on each side of the isolation barrier. The logic
supplies may be tied to the input supplies. Isolation is
maintained by the separation of GND1 and GND2 where
significant operating voltages and transients can exist
without affecting the operation of the LTM2892-S. The ON1
and/or ON2 pins enable or shut down the LTM2892-S, both
must be driven to their respective logic supply voltage for
proper operation. All SPI or Digital signals are referenced
to the logic supply pins V
or VL2.
L1
SPI signaling is typically configured by defining the digital
pins as follows:
Logic Side: IN1 = SCK(IN), IN2 = SDI(IN), IN3 = CS(IN)
= SDOE, and OUTD = SDO(OUT).
Isolated Side: OUT1 = SCK(OUT), OUT2 = SDI(OUT),
OUT3 = CS(OUT), and IND = SDO(IN).
Reference Figure 1 for schematic representation.
No special precautions are required for low RF emissions.
EMI performance is shown in Figure 2, measured using
a gigahertz transverse electromagnetic (GTEM) cell and
method detailed in IEC 61000-4-20, Testing and Measurement Techniques – Emission and Immunity Testing in
Transverse Electromagnetic Waveguides.
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DEMO MANUAL DC1957A
OPERATING PRINCIPLES
LTM2892-S
V
CC1
V
L1
ON1
EOUTD
INC
INB
INA
OUTF
OUTE
OUTD
Figure 1. SPI Pin Definition
60
DETECTOR = PEAK HOLD
RBW = 120kHz
VBW = 300kHz
50
SWEEP TIME = 680ms, ≥ 10 SWEEPS
NUMBER OF POINTS = 501
5V
CS(IN)
SDI(IN)
SCK(IN)
SDO(OUT)
ISOLATION BARRIER
V
CC2
V
L2
ON2
EOUTA
OUTC
OUTB
OUTA
INF
INE
IND
GND2GND1
dc1957a F01
5V
CS(OUT)
SDI(OUT)
SCK(OUT)
SDO(IN)
NOTE: INE AND INF ARE
OPTIONAL CONNECTIONS
40
30
20
dBµV/m
10
TA = 25°C
0
–10
–20
CISPR 22 CLASS B LIMIT
1000400 800200 600100
dn1957a F02
–30
DUT
0
500 900300 700
FREQUENCY (MHz)
2
Figure 2. DC1957A Radiated Emissions
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QUICK START PROCEDURE
DEMO MANUAL DC1957A
Demonstration circuit 1957A is easy to set up and evaluate the performance of the LTM2892-S. Refer to Figure 3
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 jumpers as shown in Figure 3 and the schematic
diagram.
2. With power off, connect the input power supplies to
- GND1 and V
V
CC1
3. Turn on the power at the input.
NOTE: Make sure that the input voltage does not ex-
ceed6V.
4. Configure jumpers or connect signals to turrets as appropriate. If a signal is connected to an input channel
turret the associated channel jumper must be removed
for proper operation.
- GND2 as shown.
CC2
Figure 3. Demo Board Setup
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DEMO MANUAL DC1957A
PCB LAYOUT
Top Copper Bottom Copper
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 U1 I.C., LTM2892CY-S LINEAR LTM2892CY-S#PBF
Hardware: For Demo Board Only
2 4 C1-4 CAP., TANT 4.7F 10V 20% 0805 NICHICON F921A475MPA
3 16 E4-19 TURRET, 0.065" MILL-MAX 2308-2-00-80-00-00-07-0
4 6 E1-3, E20-22 TURRET, 0.095" MILL-MAX 2501-2-00-80-00-00-07-0
5 2 JP6-7 2mm SINGLE ROW HEADER, 2 X 1 PIN SAMTEC TMM-102-02-L-S
6 10 JP1-5, JP8-12 2mm SINGLE ROW HEADER, 3 x 1 PIN SAMTEC TMM-103-02-L-S
7 12 JP1-12 2mm SHUNT SAMTEC 2SN-BK-G
8 10 R1-R10 RES., CHIP 100 5% 1206 AAC CR18-101JM
4
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SCHEMATIC DIAGRAM
DEMO MANUAL DC1957A
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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DEMO MANUAL DC1957A
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 application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
Linear Technology Corporation
6
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
dc1957af
LT 0912 • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2012
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