MAX3292CSD Maxim Integrated Products, MAX3292CSD Datasheet - Page 13

• Manufacturer Part Number: MAX3292CSD
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated Products

Specifications of MAX3292CSD

• Data Rate: 10000 Kbps
• Propagation Delay Time Ns: 44 ns
• Operating Supply Voltage: 5 V
• Supply Current: 2 mA
• Operating Temperature Range: 0 C to + 70 C
• Package / Case: SOIC-14
• Input Voltage: 5 V
• Maximum Power Dissipation: 695 mW
• Mounting Style: SMD/SMT
• Output Current: +/- 30 mA to + 250 mA
• Output Voltage: - 7.5 V to + 12.5 V
• Product: RS-422/RS-485 Combination
• Lead Free Status / Rohs Status: No

3) Don’t overload the cable with too many receivers.
The MAX3291/ MAX3292 are centered for a load imped-
ance of 54Ω, which corresponds to the parallel combina-
tion of the cable impedance and termination resistors. If
your cable impedance deviates somewhat from this
value, you still get the preemphasis effect (although the
ideal preemphasis time, t
However, if your cable impedance is significantly differ-
ent, the preemphasis ratio DPER changes, resulting in
Figure 19. Typical Half-Duplex RS-485 Network
Figure 20. Typical Full-Duplex RS-485 Network
Even though the MAX3291/MAX3292 receives pre-
sent only 1/4-unit load, placing 128 receivers on the
cable will attenuate the signal if spaced out along
the cable and, in addition, cause reflections if
clumped in one spot. The MAX3291/MAX3292 suc-
cessfully drive the cables to correct RS-485/RS-422
levels with 128 receivers, but the preemphasis
effect is significantly diminished.
for High-Speed, Long-Distance Communication
RS-485/RS-422 Transceivers with Preemphasis
DE
RO
RE
DI
RO
RE
DE
DI
NOTE: RE AND DE ON.
D
D
MAX3291
MAX3292
R
______________________________________________________________________________________
R
A
B
Z
Y
R = Z
R = Z
PRE
O
O
Z
Y
B
A
, may need adjustment).
R = Z
Y
DI
O
D
Z
DE
B
RE
RO
R
A
DI
Z
D
Y
DE
significantly less preemphasis. Determine the preempha-
sis ratio versus load by referring to the Driver Differential
Output Voltage vs. R
Characteristics . Read the strong and normal levels from
the graph (remember that the horizontal units are half
your cable impedance) and divide the two numbers to
get DPER (DPER = V
Figures 19 and 20 show typical network application cir-
cuits with proper termination.
At low data rates (<1Msps), preemphasis operation is
not guaranteed because it is highly dependent on the
system power-supply noise. Minimize this noise by
increasing bypass capacitance and using a power
supply with a fast transient response.
B
R
RO
A
RE
Y
DI
D
Z
Preemphasis at Low Data Rates
DE
B
RE
R
R = Z
RO
DIFF
STRONG
O
A
graph in the Typical Operating
Y
B
A
Z
R = Z
R = Z
/ V
O
O
Y
B
A
Z
NORMAL
MAX3291
MAX3292
R
R
DE
D
D
= V
(MAX3292)
ODP
DI
DE
RE
RO
RO
DI
RE
/ V
OD
13
).