MAX3845 Maxim Integrated Products, MAX3845 Datasheet - Page 12

• Manufacturer Part Number: MAX3845
• Description: DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
• Manufacturer: Maxim Integrated Products

DVI/HDMI 2:4 TMDS Fanout Switch and
Cable Driver
Figure 4. Simplified Input Circuit Schematic
Figure 5. Simplified Output Circuit Schematic
12
INPUT+
INPUT-
TMDS
TMDS
______________________________________________________________________________________
MAX3845
V
50Ω
CC
*TVS IS A "TRANSIENT VOLTAGE
50Ω
SUPPRESSOR" CLAMP-CIRCUIT.
TVS*
EQUALIZATION
NETWORK
MAX3845
Interface Models
TVS*
V
CC
TMDS
OUTPUT+
TMDS
OUTPUT-
The data inputs and outputs are the MAX3845’s most
critical paths, and great care should be taken to mini-
mize discontinuities on these transmission lines
between the connector and the IC. Here are some sug-
gestions for maximizing the performance of the
MAX3845:
For more information, refer to the schematic and board
layers of the Maxim evaluation kit, MAX3845EVKIT .
The exposed pad on the 100-pin TQFP-EP provides a
very low thermal resistance path for heat removal from
the IC. The pad is also electrical ground on the
MAX3845 and must be soldered to the circuit board
ground for proper thermal and electrical performance.
Refer to Maxim Application Note HFAN-08.1: Thermal
Considerations of QFN and Other Exposed-Paddle
Packages for additional information.
Because the MAX3845 is a high-power device, it is
important to ensure that good heat dissipation is incor-
porated into the PCB design. The device’s temperature-
sense pin (TEMP) allows estimation of the junction
temperature to be made while the MAX3845 is operat-
ing. This information can be used to determine if the
PCB layout is dissipating heat properly.
• Maintain 100Ω differential transmission line imped-
• The data and clock inputs should be wired directly
• An uninterrupted ground plane should be posi-
• Ground path vias should be placed close to the IC
• Use good high-frequency layout techniques and
ance into and out of the MAX3845.
between the cable connector and IC without stubs.
tioned beneath the high-speed I/Os.
and the input/output interfaces to allow a return cur-
rent path to the IC and the DVI/HDMI cable.
multilayer boards with an uninterrupted ground
plane to minimize EMI and crosstalk.
Exposed-Pad Package and Thermal
Layout Considerations
Considerations