MAX3845UCQ+TD Maxim Integrated Products, MAX3845UCQ+TD Datasheet - Page 8

• Manufacturer Part Number: MAX3845UCQ+TD
• Description: IC SW/CBL DRVR DVI/HDMI 100TQFP
• Manufacturer: Maxim Integrated Products
• Type: HDMI/DVI Switchr

Specifications of MAX3845UCQ+TD

• Applications: HDMI, DVI, Receivers
• Mounting Type: Surface Mount
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX3845 2:4 DVI/HDMI fanout switch and cable
driver accept differential CML input data at rates of
250Mbps up to 1.65Gbps (individual channel data
rate). The input portion of the device consists of two
independent TMDS inputs, each having four fixed-level
equalizers, four limiting amplifiers, a loss-of-signal
(LOS) detector, and power-down control. The output
portion of the device consists of four independent
TMDS outputs, each having four multiplexers, four out-
put buffers with selectable preemphasis, HOTPLUG
detection, and channel selection control (Figure 1).
All four differential pairs on the MAX3845’s TMDS
inputs have fixed-level equalizers to compensate for 0in
to 6in of FR4 PCB losses. The signal boost is approxi-
mately 1dB at 825MHz. If more equalization is desired,
use the MAX3814 or MAX3815 in front of the MAX3845
to accommodate long cable lengths.
Limiting amplifiers follow the equalizer block to ensure
proper signal levels are achieved for the multiplexers.
Input channel 1 has an LOS detector attached to the
IN1_B pair. For input channel 2 the LOS detector is
attached to the IN2_C pair. If the received-signal ampli-
tude is smaller than 150mV
output channels selected to input 1 are muted.
Likewise, if a signal smaller than 150mV
at IN2_C, all output channels selected to input 2 are
muted.
Each MAX3845 output has four multiplexers, one for
each signal pair contained in the TMDS channel. These
connect the output to either input 1 or input 2. The
IN_SELx pins control the multiplexers.
The preemphasis drivers have three selectable levels
of preemphasis: 0dB, 3dB, and 6dB. The preemphasis
drivers provide a precompensated signal that allows for
extended length cables to be used at the output.
DVI/HDMI 2:4 TMDS Fanout Switch and
Cable Driver
8
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Loss-of-Signal (LOS) Detectors
Detailed Description
Fixed Input Equalization
Preemphasis Drivers
P-P
Limiting Amplifiers
(typical) at IN1_B, all
Multiplexers
P-P
(typical) is
The MAX3845 is designed and characterized to oper-
ate from 250Mbps to 1.65Gbps. HDMI 1.3 specifies up
to 2.25Gbps for 1080p “deep color” and allows a maxi-
mum data rate of 3.4Gbps on each of the three data
pairs. The MAX3845 operates normally in an HDMI 1.3
system up to 1.65Gbps. The MAX3845 operates at data
rates above 1.65Gbps with reduced jitter performance.
See the Typical Operating Characteristics section for
more information.
High-bandwidth digital content protection (HDCP) is a
copy protection system employed in some DVI and
most HDMI interfaces. Video data is encrypted at the
transmitter and decrypted at the receiver. The data
scrambling is dependent upon shared keys established
during the authentication protocol that occurs over the
DDC channel (between the video source and the dis-
play). The MAX3845 does not decrypt or reencrypt
data. Therefore, HDCP-encrypted video routed through
the MAX3845 is only viewable on the display to which
the DDC channel is connected. For applications that
employ HDCP, the MAX3845 acts as a dual 1:4 switch
and not as a fanout device. This means that one video
source can be selected to drive any one of four dis-
plays, but the video source cannot be replicated on
more than one display at the time. Fanout is possible in
non-HDCP applications, allowing one video source to
simultaneously drive up to four displays.
The OUT_LEVEL pin is an LVTTL input that allows the
user to select between standard output drive current
(11mA) or increased output drive current (14mA). The
increased output current setting allows back termina-
tion resistors to be used on the outputs. The use of
back terminations is highly recommended for best sig-
nal integrity (see Figures 2 and 3).
If OUT_LEVEL is set low, the standard output drive cur-
rent (11mA) is consistent with DVI/HDMI architecture
and common-mode levels. As per standard, no back
termination is used so no reflected energy can be
absorbed.
If OUT_LEVEL is set high, the output drive current is
increased to 14mA and allows the use of back termina-
tion resistors. Two options are available: a differential
back termination resistor or two single-ended pullup
resistors (see Figures 2 and 3).
Output Level Control, Back Termination,
Applications Information
MAX3845 in HDMI 1.3 Systems
MAX3845 in HDCP Systems
and AC-Coupling