LTC2851 LINER [Linear Technology], LTC2851 Datasheet - Page 13

• Manufacturer Part Number: LTC2851
• Description: 20Mbps RS485 Transceivers
• Manufacturer: LINER [Linear Technology]

applicaTions inFormaTion
from a driver transition may exceed the hysteresis levels
on the logic and data inputs pins causing an unintended
state change. This can be avoided by maintaining normal
logic levels on the pins and by slewing inputs through
their thresholds by faster than 1V/µs when transitioning.
Good supply decoupling and proper line termination also
reduces glitches caused by driver transitions.
Cable Length vs Data Rate
For a given data rate, the maximum transmission distance
is bounded by the cable properties. A typical curve of cable
length vs data rate compliant with the RS485 standard is
shown in Figure 14. Three regions of this curve reflect
different performance limiting factors in data transmis-
sion. In the flat region of the curve, maximum distance is
determined by resistive losses in the cable. The downward
sloping region represents limits in distance and data
rate due to AC losses in the cable. The solid vertical line
Typical applicaTions
TE = 5V
D
R
LTC2859
Multi-Node Network with End Termination Using LTC2859
R
TE = 0V
D
LTC2859
represents the specified maximum data rate in the RS485
standard. The dashed lines at 250kbps and 20Mbps show
the maximum data rates of the LTC2859/LTC2861 in Low-
EMI and normal modes, respectively.
R
TE = 0V
100
10k
10
1k
Figure 14. Cable Length vs Data Rate
(RS485 Standard Shown in Solid Lines)
10k
D
LTC2859
100k
LTC2859/LTC2861
DATA RATE (bps)
RS485 MAX
DATA RATE
1M
MAX DATA RATE
LOW-EMI MODE
10M
MODE MAX
DATA RATE
NORMAL
285961 F14
R
LTC2859
100M
2859/61 TA04
D
TE = 5V
13
285961fc