DEMO MANUAL
DC1079A-A/DC1079A-B
LTC4310-1/LTC4310-2
Hot Swappable I2C Isolators
DESCRIPTION
Demonstration circuit 1079A features the LTC4310 I2C
isolator. The LTC®4310 provides bidirectional I2C communication between two I2C buses whose grounds are
isolated from one another. Each LTC4310 encodes I2C
bus logic states into signals that are transmitted across
an isolation barrier to another LTC4310. The receiving
LTC4310 decodes the transmission and drives its I2C bus
to the appropriate logic state. The isolation barrier can be
bridged by an inexpensive Ethernet (or other) transformer
to achieve communications across voltage differences
reaching thousands of volts, or it can be bridged by capacitors for lower voltage isolation. DC1079A shows both
transformer and capacitor techniques. Separate supplies
are connected on opposite sides of the isolation barrier.
Rise time accelerators provide strong pull-up currents on
SCL and SDA rising edges to meet rise time specifications
for heavily loaded systems. Data and clock Hot Swap™
circuitry prevent data corruption when a card is inserted
into or removed from a live bus. When a bus is stuck low
for 37ms, the LTC4310 turns off its pull-down devices
and generates up to sixteen clocks and a STOP bit in an
attempt to free the bus. Driving EN low sets the LTC4310
in a very low current shutdown mode to conserve power.
This is set with a jumper for each LTC4310 on the DC1079A.
The READY pin provides a digital output flag that pulls low
to indicate that the LTC4310 is driving its SDA and SCL
pins with the logic state information it is receiving on its
RXP and RXN pins from the other LTC4310. An LED at
each READY pin indicates that READY is low.
DC1079A-A is populated with the LTC4310-1 and is intended for use in I2C systems up to 100kHz. DC1079A-B
is populated with the LTC4310-2 which is intended for I2C
bus speeds from 100kHz to 400kHz.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Hot Swap, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
BOARD PHOTO
Figure 1. DC1079A
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DEMO MANUAL
DC1079A-A/DC1079A-B
PERFORMANCE SUMMARY
Table 1. DC1079A Typical Setup and Performance Summary (TA = 25°C)
PARAMETER
CONDITIONS
MIN
TYP
Supply and Bus Voltage
VCC_A to GND_A, VCC_B to GND_B, VCC_C to GND_C, VCC_D to GND_D
Isolation
GND_A to GND_B, 100V Capacitor Coupling
GND_C to GND_D, EPF8119S Transformer Coupling
100
1500
VRMS
Maximum I2C Clock
DC1079A-A, LTC4310-1
DC1079A-B, LTC4310-2
100
400
kHz
kHz
Bus Pull-Up Resistors
DC1079A-A, LTC4310-1
DC1079A-B, LTC4310-2
10
3.3
kΩ
kΩ
3
MAX
UNITS
5.5
V
V
QUICK START PROCEDURE
Demonstration circuit 1079A is easy to set up to evaluate
the performance of the LTC4310. Refer to Figure 2 and
Figure 3 for proper measurement equipment setup and
follow the procedures below.
100V Isolation with Capacitor Coupling (Figure 2):
1. Connect first supply (3V to 5.5V) across VCC_A and
GND_A.
2. Connect first I2C bus to SDA_A and SCL_A.
3. Set ENABLE_A Jumper to EN.
4. Connect second supply (3V to 5.5V) across VCC_B
and GND_B.
1500VRMS Isolation with Transformer Coupling (Figure 3):
1. Connect first supply (3V to 5.5V) across VCC_C and
GND_C.
2. Connect first I2C bus to SDA_C and SCL_C.
3. Set ENABLE_C Jumper to EN.
4. Connect second supply (3V to 5.5V) across VCC_D
and GND_D.
5. Connect second I2C bus to SDA_D and SCL_D.
6. Set ENABLE_D Jumper to EN.
5. Connect second I2C bus to SDA_B and SCL_B.
6. Set ENABLE_B Jumper to EN.
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DEMO MANUAL
DC1079A-A/DC1079A-B
QUICK START PROCEDURE
V1
3V TO 5.5V
V2
3V TO 5.5V
+–
–+
ENABLE1
ENABLE2
SDA1
SDA2
SCL1
SCL2
READY1
READY2
Figure 2. DC1079A Setup for Low Voltage Isolation and Capacitor Coupling
READY1
READY2
SCL1
SCL2
SDA1
SDA2
ENABLE1
ENABLE2
+–
–+
V1
3V TO 5.5V
V2
3V TO 5.5V
Figure 3. DC1079A Setup for High Voltage Isolation and Transformer Coupling
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DEMO MANUAL
DC1079A-A/DC1079A-B
OPERATION
DC1079A demonstrates I2C communication sent across an
isolation barrier with the LTC4310. For low voltage 100V
isolation, a power supply between 3V to 5.5V is connected
across VCC_A and GND_A. This supply provides the pull-up
supply for the I2C bus connected to this side of the ground
isolation. A second supply, isolated from the first supply,
is connected across VCC_B and GND_B. The second I2C
bus is connected to this side and pulled-up to VCC_B.
The state of the I2C bus on GND_A is transmitted by an
LTC4310 to the corresponding LTC4310 on GND_B across
small 100pF, 100V capacitors. And vice versa, the LTC4310
on GND_B reports its I2C bus state to the LTC4310 on
GND_B. When both supplies are up, both LTC4310 devices
are enabled (set by jumpers), communication between the
two LTC4310 devices is established, and the bus lines are
not stuck low, a READY signal is given by each LTC4310.
A green LED on each side of the isolation is driven by
the respective READY pin and indicates that I2C is linked
between the two buses.
In an application with higher voltage isolation of 1500VRMS,
an inexpensive Ethernet transformer is used in place of the
coupling capacitors. This is demonstrated in the bottom
half of the DC1079A. The setup and operation is the same
above with the capacitor coupling, but the supplies and I2C
buses are connected to GND_C and GND_D ground sides.
DC1079A-A and DC1079A-B DIFFERENCES
On the DC1079A-A, the LTC4310-1 is used at U1, U2, U3,
and U4 and intended for bus speeds up to 100kHz. The
DC1079A-B uses the LTC4310-2 in all four places instead
and is intended for bus speeds from 100kHz to 400kHz.
When the SDA (or SCL) bus is rising between 0V and 0.35
• VCC, the LTC4310 controls the bus rise rate to (0.35 •
VCC)/900ns for the LTC4310-1 and to (0.35 • VCC)/300ns
for the LTC4310-2.
Bus pull-up resistors R2 and R3 that go to VCC_A, R5 and
R8 that go to VCC_B, R10 and R11 that go to VCC_C, and
R13 and R16 that go to VCC_D are also different between
the DC1079A-A and the DC1079A-B. The 10k pull-ups
along with the LTC4310-1 on the DC1079A-A allows for
approximately 50pF of bus capacitance with a supply of
5V, or 3pF with a 3.3V supply. On the DC1079A-B, the
3.3k pull-ups along with the LTC4310-2 allows for close
to 100pF of bus capacitance with a supply of 5Vor 3.3V.
Refer to the SDA, SCL Bus Pull-Up Resistor Value Selection section in the LTC4310 datasheet.
RADIATED EMISSIONS
DC1079A capacitor coupling and transformer coupling
circuits have been tested and scanned for radiated emissions. The levels fall below the limits defined in the basic
international EMI standard CIPR22 Class B. Figure 4 shows
the results for the capacitor coupling and Figure 5 is the
results for transformer coupling. Layout, parts placement,
component selection, and wire connections will all have
an effect with radiated emissions. Attention must be paid
towards these items when testing for radiated emissions.
BOARD LAYOUT
DC1079A layout provides galvanic isolation on all four
layers between the grounds as well as the vias, copper
and pads referenced to the respective ground. Refer to
the layout files.
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4
DEMO MANUAL
DC1079A-A/DC1079A-B
OPERATION
55
AMPLITUDE (dBuV/m)
45
35
25
15
5
30
100
200
300
400
500
600
700
800
900
1000
800
900
1000
FREQUENCY (MHz)
Figure 4. DC1079A, Capacitor Coupling, Radiated Emissions Scan
55
AMPLITUDE (dBuV/m)
45
35
25
15
5
30
100
200
300
400
500
600
700
FREQUENCY (MHz)
Figure 5. DC1079A, Transformer Coupling, Radiated Emissions Scan
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5
DEMO MANUAL
DC1079A-A/DC1079A-B
PCB LAYOUT
Top Silkscreen
Layer 1. Component Side
Layer 2. GND Layer
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6
DEMO MANUAL
DC1079A-A/DC1079A-B
PCB LAYOUT
Layer 3. GND Layer
Layer 4. Bottom Layer
dc1079af
7
DEMO MANUAL
DC1079A-A/DC1079A-B
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
DC1079A Rev 3
1
6
C1, C2, C7, C8, C9, C10
CAP, 0603 0.1μF 10V 10% X7R
AVX 0603ZC104KAT
2
5
C3, C4, C5, C6, C11
CAP, 0805 100pF 5% 100V COG
AVX 08051A101JAT
3
4
D1, D2, D3, D4
LED, GREEN
PANASONIC LN1351C-(TR)
4
8
E1, E2, E7-E10, E16, E17
TURRET
MILL-MAX-2501-2-00-80-00-00-07-0
5
16
E3-E6, E11-E14, E18-E25
TURRET
MILL MAX 2308-2-00-80-00-00-07-0
6
4
JP1, JP2, JP5, JP6
HEADER, 3-PIN, 2mm
SAMTEC TMM-103-02-L-S
7
4
R1, R6, R9, R14
RES, 0603 1kΩ 5% 1/10W
AAC CR16-102JM
8
1
T1
XFMR, GALVANIC GROUND ISOLATION, 1500V
PAC ELEC. EPF8119S
9
4
XJP1, XJP2X, JP5, XJP6
SHUNT, 2mm
SAMTEC 2SN-BK-G
DC1079A-A Rev 3
1
1
2
12
3
4
PCB ASSEMBLY
LINEAR TECH DC1079A REV 3
R2-R5, R7, R8, R10-R13, R16
RES, 0603 10kΩ 5% 1/10W
AAC CR16-103JM
U1, U2, U3, U4
IC, I2C THROUGH SPLITTER
LINEAR TECH. LTC4310CDD-1
PCB ASSEMBLY
LINEAR TECH DC1079A REV 3
DC1079A-B Rev 3
1
1
2
8
R2, R3, R5, R8, R10, R11, R13, R16 RES, 0603 3.3kΩ 5% 1/10W
VISHAY CRCW06033K30JNEA
3
4
R4, R7, R12, R15
RES, 0603 10kΩ 5% 1/10W
AAC CR16-103JM
4
4
U1, U2, U3, U4
IC, I2C THROUGH SPLITTER
LINEAR TECH. LTC4310CDD-2
dc1079af
8
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.
A
B
C
EN
[3]
1K
[3]
1K
4
5
LTC4310CD-2
5
LTC4310CD-1
-B
U1-U4
-A
ASSY
3.3k
10k
R2, R3, R5, R8, R10, R11, R13, R16
1. ALL CAPACITOR AND RESISTOR CASE SIZE ARE 0603.
2. INSTALL SHUNTS AS SHOWN.
[3]
1
GND
READY
SCL
SDA
ENABLE
U3
[3]
GND
READY
SCL
SDA
ENABLE
U1
[3]
E20
10K
R12
5
4
3
2
1
10K
R4
E24
[3]
R11
[3]
R3
3
D3
GRN
READY_C
R10
R9
D1
GRN
READY_A
R2
R1
2
2
JP5
2
E11
DIS
ENABLE_C
EN
DIS
ENABLE_A
JP1
E13
E16
E10
E19
E22
E5
E3
E7
E2
NOTES: UNLESS OTHERWISE SPECIFIED,
C
GND_C
READY_C
SCL_C
SDA_C
GND_C
VCC_C
A
GND_A
READY_A
SCL_A
SDA_A
GND_A
VCC_A
11
D
4
4
TXN
TXP
VCC
RXP
RXN
3
4
7
TX+
16
0.1uF
9
10
11
12
13
14
15
C10
RX-
CT(4)
RX+
N/C
N/C
TX-
CT(2)
C9
RD-
CT(3)
RD+
N/C
N/C
TD-
CT
TD+
0.1uF
8
7
6
5
2
8
6
1
10
9
T1
EPF8119S
3
1500 Vrms TRANSFORMER ISOLATION
100V
C11
100pF
100V
C8
TXN
TXP
VCC
RXP
RXN
6
7
8
9
TXN
TXP
VCC
RXP
RXN
0.1uF
10
VCC_D
6
6
8
9
10
7
C6
100pF
100V
C5
100pF
C2
0.1uF
VCC_B
7
8
9
0.1uF
C7
TXN
TXP
VCC
RXP
RXN
0.1uF
100V
C4
100pF
10
100V
C3
100pF
C1
VCC_C
VCC_A
CAPACITOR ISOLATION
3
U2
[3]
5
4
3
2
1
R14
2
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6833/,(')2586(:,7+/,1($57(&+12/2*<3$576
6&$/( 121(
$33(1* ',/,$15
3&%'(6 0,
TECHNOLOGY
D
GND_D
READY_D
SCL_D
SDA_D
GND_D
VCC_D
B
GND_B
READY_B
SCL_B
SDA_B
DATE
DILIAN R.
APPROVED
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04/08/10
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1
6+((7 LTC4310CDD-1/-2
DEMO CIRCUIT 1079A
Monday, August 02, 2010
,&12
2) 5(9
ISOLATED I2C THROUGH SPLITTER
1$
6,=(
PRODUCTION
GND_B
1
REVISION HISTORY
DESCRIPTION
VCC_B
7,7/( 6&+(0$7,&
E21
E25
4
5
E14
E17
E9
E18
E23
E6
E4
E8
E1
E12
$33529$/6
DIS
ENABLE_D
EN
DIS
ENABLE_B
EN
3
REV
2
D4
GRN
2
JP6
2
JP2
READY_D
1K
&86720(5127,&(
[3]
R16
D2
GRN
READY_B
1K
R6
ECO
3
1
[3]
10K
[3]
R13
[3]
10K
R8
R15
R5
R7
2
/,1($57(&+12/2*<+$60$'($%(67())25772'(6,*1$
&,5&8,77+$70((76&86720(56833/,('63(&,),&$7,216
+2:(9(5,75(0$,167+(&86720(5
65(63216,%,/,7<72
9(5,)<3523(5$1'5(/,$%/(23(5$7,21,17+($&78$/
$33/,&$7,21&20321(1768%67,787,21$1'35,17('
&,5&8,7%2$5'/$<2870$<6,*1,),&$17/<$))(&7&,5&8,7
3(5)250$1&(255(/,$%,/,7<&217$&7/,1($5
7(&+12/2*<$33/,&$7,216(1*,1((5,1*)25$66,67$1&(
GND
READY
SCL
SDA
ENABLE
U4
[3]
GND
READY
SCL
SDA
ENABLE
11
3
1
3
1
GND
GND
11
GND
GND
11
3
1
3
1
5
A
B
C
D
DEMO MANUAL
DC1079A-A/DC1079A-B
SCHEMATIC DIAGRAM
dc1079af
9
DEMO MANUAL
DC1079A-A/DC1079A-B
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
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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
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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
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Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1079af
10 Linear Technology Corporation
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