Datasheet

MAX3845
DVI/HDMI 2:4 TMDS Fanout Switch and
Cable Driver
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Temperature Sense
Pin 14, TEMP, allows the on-die temperature to be
sensed as an analog voltage output. To sense the die
temperature, measure the DC voltage at TEMP. The
approximate die temperature can be determined using
the following equation:
T
J
= (V
TEMP
- 0.93) x 297
Also see the Typical Operating Characteristics section
for more information.
Power-Down
The power-down inputs (PWRDWN_1 and PWRDWN_2)
reduce power consumption by powering down the cho-
sen input and all outputs that are selected to that input.
For example, when output channels 1 and 4 are select-
ed to transmit input channel 2, and channel 2 is pow-
ered down, both outputs 1 and 4 are also powered
down.
Hotplug Detect
Each output channel has a HOTPLUGx detection pin
associated with it. This pin is designed to detect
whether a monitor’s hotplug connection is attached. If
HOTPLUGx is low (less than 1.5V), the associated out-
put is powered down. If HOTPLUGx is higher than
V
CC
- 0.2V, up to 5.5V, the associated output is pow-
ered up.
Activating an Output
Several things must occur for an output to be active.
Table 2 lists the required inputs to enable an output.
Cable Selection
Good quality cable is recommended for good perfor-
mance. Deterministic jitter (DJ) can be caused by dif-
ferential-to-common-mode conversion (or vice versa)
within a twisted pair (STP or UTP), usually a result of
cable twist or dielectric imbalance. Refer to Application
Note
HFAN-4.5.4: ‘Jitter Happens’ when a Twisted Pair
is Unbalanced for more information.
VOLTAGES AT THE INPUT OF THE TMDS RECEIVER (TYPICAL)
CONDITIONS
V
DIFF
V
CM
V
H
V
L
PREEMPHx = LOW, OUT_LEVEL = LOW (Output Drive Current = 11mA)
No back termination 1100mV
P-P
V
CC
- 275mV V
CC
V
CC
- 550mV
PREEMPHx = LOW, OUT_LEVEL = HIGH (Output Drive Current = 14mA)
Differential 200 back terminations (DC-coupled) 950mV
P-P
V
CC
- 350mV V
CC
- 120mV V
CC
- 585mV
Differential 300 back terminations (DC-coupled) 1050mV
P-P
V
CC
- 350mV V
CC
- 90mV V
CC
- 615mV
Single-ended, 2x 100 back terminations (AC-coupled) 950mV
P-P
V
CC
V
CC
+ 240mV V
CC
- 240mV
Table 1. Output Levels With and Without Back Termination
OUTPUT x
STATE
IN_SELx
CONDITION
HOTPLUGx
CONDITION
PWRDWN_1
CONDITION
PWRDWN_2
CONDITION
LOS 1
CONDITION
LOS 2
CONDITION
INPUT 1 HIGH HIGH LOW Don’t care LOW Don’t care
INPUT 2 LOW HIGH Don’t care LOW Don’t care LOW
Table 2. Output Enable Requirements