Datasheet
LTC4310-1/LTC4310-2
14
431012fa
applicaTions inForMaTion
TYPICAL APPLICATIONS
Figure 8 shows the LTC4310-1 providing I
2
C communica-
tions between an I
2
C bus referenced to system ground and
an I
2
C bus using –5V for its ground reference. Ceramic
coupling capacitors, C1-C5, are used to bridge the isolation
barrier. This circuit is recommended for ground isolation
voltages less than 100V and is limited by the voltage rating
of C1-C5. Higher voltage ceramic capacitors may be used
to achieve higher isolation voltages. Because the LTC4310
uses a pseudo-differential transmit scheme, capacitor C5
must be connected between ground and –5V to provide a
return path for the transmitted current.
Figure 9 shows the LTC4310-1 in an application circuit
using its zero current shutdown mode. A microprocessor
only activates the left LTC4310-1 when it needs to com-
municate with the isolated I
2
C bus. Because the LTC4310-1
contains a STOP bit and bus idle detection circuitry, there
is no danger of connecting in the middle of a message
when the microprocessor asynchronously reenables the
LTC4310-1.
Figure 8. Low Voltage I
2
C Isolation Between a Ground Referenced Bus and a –5V Referenced Bus
3.3V
C
BUS
= 30pFC
BUS
= 100pF
R1
5.1k
R2
5.1k
R3
10k
431012 F08
C7
0.01µF
C1
–5V
–5V
R5
10k
R6
10k
GND
RXP
RXN
TXP
TXN
LTC4310-1
V
CC
READY
EN
SDA
SCL
R4
10k
C3
C2
C4
C6
0.01µF
GND
TXP
TXN
RXP
RXN
LTC4310-1
V
CC
READY
EN
SDA
SCL
C5
C1 TO C5 = 47pF, 100V
Figure 9. The LTC4310-1 in a Zero Current Shutdown Application
5V
R1
3.3k
R2
3.3k
R3
10k
431012 F09
C7
0.01µF
–5V
–5V
R5
5.1k
R6
5.1k
GND
RXP
RXN
TXP
TXN
LTC4310-1
V
CC
READY
EN
SDA
SCL
R4
10k
C6
0.01µF
GND
TXP
TXN
RXP
RXN
LTC4310-1
V
CC
READY
EN
SDA
SCL
. . .
SLAVE#1
µP
SLAVE#N
ON
OFF
C1
C3
C2
C4
C5
C1 TO C5 = 47pF, 100V
C
BUS
= 150pFC
BUS
= 200pF