Datasheet

LTC4315
15
4315f
APPLICATIONS INFORMATION
from a live backplane. The features mentioned previously
provide noise immunity and allow timing specifications to
be met for a wide range of backplane loading conditions.
In the 6 × 4 radial configuration shown in Figure 9, the
LTC4314s on the shelf managers and the LTC4315s on
the FRUs drive the large backplane capacitance while the
I
2
C slave devices on the FRUs only drive the small input
capacitance of the LTC4315. The LTC4314s on only one
of the shelf managers are enabled at a given time. All the
benefits provided by the LTC4315 in Figure 8 apply to
Figure 9 as well.
Cascading and Interoperability with Other LTC Buffers
and Non-Compliant I
2
C Devices
Multiple LTC4315s can be cascaded or the LTC4315 can be
cascaded with other LTC bus buffers. Cascades often exist
in large I
2
C systems, where multiple I/O cards having bus
buffers connect to a common backplane bus. Two issues
need to be considered when using such cascades—the
a d d i t i v e n a t u r e o f t h e b u f f e r l o g i c l o w o f f s e t v o l t a g e s a n d t h e
impact of the RTA-buffer interaction on the noise margin.
Figure 9. LTC4315s Used in a Radially Connected Telecommunications System in a 6 × 4 Arrangement. Only the
Clock Path Is Shown for Simplicity. The Data Pathway Is Identical.
SHELF MANAGER #1
IPMB-A(X24)
IPMB-B(X24)
SCL1
SCL24
SCL1
SCL24
3.3V
R2
10k
LTC4314#1
V
CC
V
CC2
SCLOUT1
SCLOUT2
SCLOUT3
SCLOUT4
SCLIN
ENABLE1
ENABLE2
ENABLE3
ENABLE4
ACC
ENABLE1A
ENABLE2A
ENABLE3A
ENABLE4A
ENABLE21A
ENABLE22A
ENABLE23A
ENABLE24A
R1
10k
µP
3.3V
3.3V
IPMB-B DETAILS (NOT SHOWN) ARE IDENTICAL TO IPMB-A
IPMB-B
R5
10k
LTC4314#6
V
CC
V
CC2
SCLOUT1
SCLOUT2
SCLOUT3
SCLOUT4
SCLIN
ENABLE1
ENABLE2
ENABLE3
ENABLE4
ACC
3.3V
4315 F09
BACKPLANE
IPMB-B
SCL24
IPMB-A
SCL1
IPMB-A
SCL24
IPMB-B
SCL1
FRU #1
LTC4315
I
2
C
DEVICE
3.3V
3.3V
3.3V
SCLOUT
V
CC2
V
CC
SCLIN
ACC
R3
10k
R4
10k
LTC4315
3.3V
SCLOUT
V
CC2
V
CC
SCLIN
ACC
FRU #24
LTC4315
I
2
C
DEVICE
3.3V
3.3V
3.3V
SCLOUT
V
CC2
V
CC
SCLIN
ACC
R6
10k
R7
10k
LTC4315
3.3V
SCLOUT
V
CC2
V
CC
SCLIN
ACC
SHELF MANAGER #2
IDENTICAL TO SHELF MANAGER #1
sss
sss sss
sss
sss