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19-0798; Rev 0; 4/07
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
General Description
The MAX3845 is a TMDS(R) 2-to-4 fanout switch and cable driver for multimonitor distribution of DVITM or HDMITM signaling up to 1.65Gbps. Both inputs and outputs are standard TMDS signaling as per DVI and HDMI standards. Because TMDS links are "point-to-point," buffering is required for fanout applications. Four DVI/HDMI TMDS outputs are provided for fanout distribution. Each TMDS output can be independently sourced from either input or can be turned off. Each TMDS input or output is composed of four differential channels that can be arbitrarily assigned to the three data signals and the 1/10th-rate clock. The data rate depends on resolution, but it can vary from 250Mbps (VGA) to 1.65Gbps (UXGA or 1080p/60). Typical applications include multiroom display of the same video source or industrial/commercial signage applications such as airport monitors or trading room floor displays. The MAX3845 includes selectable output preemphasis that extends output cable reach up to an additional 7m. For DDC switching, use the companion MAX4814E* 2:4 low-resistance CMOS crosspoint switch. DDC switching is not required for applications that connect DDC to one reference monitor only. The MAX3845 can be configured to create a 2 x 8 or 4 x 4 switch (see the Typical Operating Circuit diagrams). The MAX3845 is available in a 14mm x 14mm, 100-pin TQFP-EP package and operates over the -10C to +85C temperature range.
Features
Two DVI/HDMI TMDS-Compatible Inputs and Four DVI/HDMI TMDS-Compatible Outputs Save Power by Turning Off Unused Outputs Each Output Independently Selects Input 1 or Input 2 Three Preemphasis Settings Extend Cable Reach Up to 7m Operation Up to 1.65Gbps 14mm x 14mm, 100-Pin TQFP Package with Exposed Paddle for Heat Sinking 3.3V Power Supply TMDS Data (x3) and Clock (x1) Can Be Arbitrarily Assigned to the Four Identical Switched Paths (A, B, C, and D)
MAX3845
Ordering Information
PART MAX3845UCQ+ TEMP RANGE PIN-PACKAGE -10C to +85C 100 TQFP-EP PKG CODE C100E-3
+Denotes a lead-free package.
EP = Exposed pad.
Applications
Digital Signage and Industrial Display PC Monitor Distribution Home A/V Receivers DVI/HDMI Distribution Amplifiers DVI/HDMI Crosspoint Switches
CONTROL SIGNALS
Typical Operating Circuit
2:4 FANOUT/SWITCH APPLICATION IN_SEL[1:4] PREEMPH[1:4] OUTPUT TO DISPLAY 1 OUTPUT TO DISPLAY 2 OUTPUT TO DISPLAY 3 OUTPUT TO DISPLAY 4 HOTPLUG[1:4] BUFFER 2:4 CMOS SWITCH x5 DDC DATA, DDC CLK, HOTPLUG, 5V, GND, (CEC)
VIDEO SOURCE 1 VIDEO SOURCE 2
MAX3845
2:4 DVI/HDMI TMDS FANOUT SWITCH AND CABLE DRIVER
Pin Configuration appears at end of data sheet.
TMDS is a registered trademark of Silicon Image, Inc. DVI is a trademark of Digital Display Working Group. HDMI is a trademark of HDMI Licensing, LCC. *Future product--contact factory for availability.
Typical Operating Circuits continued at end of data sheet.
1
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
ABSOLUTE MAXIMUM RATINGS
Supply Voltage Range (VCC) ................................-0.3V to +5.5V Voltage Range at HOTPLUGx Pins ......................-0.3V to +6.0V Voltage Range at LVTTL, LVCMOS, I/O Pins .......-0.3V to +5.5V Voltage Range at CML Output Pins ......................-0.3V to +5.5V Voltage Range at CML Input Pins (CML short to GND duration < 1s)....................-0.3V to +4.0V Voltage Between Any Input CML I/O Complementary Pair ......................................................3.3V Voltage Range at LOSMUTE_EN ..........................-0.3V to +5.5V Voltage Between Any Output CML I/O Complementary Pair.......................................................3.6V Continuous Power Dissipation (TA = +70C) 100-Pin TQFP-EP (derate 45.5mW/C above +70C) ............................................................3636mW Operating Junction Temperature .....................-55C to +150C Storage Temperature Range ............................-55C to +150C Die Attach Temperature ..................................................+400C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = 3.0V to +3.6V, TA = -10C to +85C. Typical values are at VCC = +3.3V, external terminations = 50 1%, TMDS rate = 250Mbps to 1.65Gbps, TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Power-Supply Current Supply-Noise Tolerance SKIN-EFFECT EQUALIZER PEAKING Fixed Rx Equalizer Compensation Settable Tx Preemphasis JITTER PERFORMANCE 0dB cable loss, no preemphasis 200 back termination 3dB cable loss, +3dB preemphasis 6dB cable loss, +6dB preemphasis 0dB cable loss, no preemphasis No back termination 3dB cable loss, +3dB preemphasis 6dB cable loss, +6dB preemphasis Residual Random Jitter (Note 3) CML INPUTS (SOURCE SIDE) Differential-Input Voltage Swing Common-Mode Input Voltage Input Voltage When Disconnected VID VCM At cable input 400 VCC - 1000 VCC - 10 2000 VCC VCC + 10 mVP-P mV Measured with source Tr/T f = 250ps 0.04 0.05 0.07 0.07 0.08 0.10 1.5 0.12 0.12 0.12 UI 0.2 0.2 0.2 2 psRMS Gain at 825MHz PREEMPHx pin = low PREEMPHx pin = open PREEMPHx pin = high 1 0 3 6 dB SYMBOL ICC CONDITIONS PREEMPH[1:4] = high, OUT_LEVEL = high, current into VCC pins, 1200mV P-P = VIN DC to 500kHz MIN TYP 454 50 MAX 626 UNITS mA mVP-P
Residual Deterministic Jitter (Measured at end of cable having ideal skin-effect loss and connectors, e.g., Gore Twin Coax, Amphenol Skewclear Twinax, with SMA connectors) (Note 2)
2
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 3.0V to +3.6V, TA = -10C to +85C. Typical values are at VCC = +3.3V, external terminations = 50 1%, TMDS rate = 250Mbps to 1.65Gbps, TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Input Resistance Input LOS/Mute Threshold Input LOS/Mute Response Time Input Return Loss CML OUTPUTS (CABLE SIDE) No preemphasis, no back termination, OUT_LEVEL = low No preemphasis, 200 OUT_LEVEL = high back termination, 900 825 VCC - 10 VCC - 10 75 90 12 Worst case among A, B, C, and D of an output VIH VIL All except IN_SELx pins IN_SELx pins VIH(MIN) < VIN < VIH(MAX) VIL(MIN) < VIN < VIL(MAX) Typical input 30k All except OUT_LEVEL pin OUT_LEVEL pin HOTPLUGx Input High Voltage HOTPLUGx Input Low Voltage to GND VCC - 0.2 2.0 1.0 0.8 100 150 500 5.5 1.5 V A V 35 1050 925 1200 mVP-P 1050 VCC + 10 VCC + 10 140 40 60 ps mV SYMBOL RIN Single-ended Differential peak-peak Deassert mute Assert mute Differential, 1.6GHz CONDITIONS MIN 45 TYP 50 150 1.2 0.6 19 MAX 55 mV s dB UNITS
MAX3845
Differential-Output Voltage Swing
VOD
Output-Voltage High Output Voltage During PowerDown Rise/Fall Time Intrapair Skew Interpair Skew CONTROL INTERFACE LVTTL Input High Voltage LVTTL Input Low Voltage LVTTL Input High Current LVTTL Input Low Current
VOH VOFF
Single-ended, no back termination Single-ended, PWRDWN_x = low or VCC = 0V 20% to 80% (TA = 0C to +85C)
Note 1: AC specifications are guaranteed by design and characterization. Note 2: Test pattern is a 210 - 1 PRBS + 20 ones + 210 - 1 PRBS (inverted) + 20 zeros. Note 3: Test pattern is a 1111 0000 pattern at 1.65Gbps.
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Typical Operating Characteristics
(Typical values are at VCC = +3.3V, TA = +25C, data pattern = 210 - 1 PRBS + 20 ones + 210 - 1 PRBS (inverted) + 20 zeros, unless otherwise noted.)
SUPPLY CURRENT vs. AMBIENT TEMPERATURE
MAX3845 toc01
SUPPLY CURRENT vs. AMBIENT TEMPERATURE
MAX3845 toc02
OUTPUT EYE DIAGRAM AT 1.65Gbps SHORT LOW-LOSS SMA CABLE
MAX3845 toc03
500 480 460 ICC (mA) 440 420 400 380 360 340 -10 5 20 35 50 65 80 AMBIENT TEMPERATURE (C) 6dB PREEMPHASIS 3dB PREEMPHASIS 0dB PREEMPHASIS OUT_LEVEL = LOW, ALL INPUTS/OUTPUTS ACTIVE, PREEMPHASIS SAME ON ALL OUTPUT CHANNELS
500 480 460 ICC (mA) 440 420 6dB PREEMPHASIS 400 3dB PREEMPHASIS 380 0dB PREEMPHASIS 360 340 -10 5 20 35 50 65 80 OUT_LEVEL = HIGH, ALL INPUTS/OUTPUTS ACTIVE, PREEMPHASIS SAME ON ALL OUTPUT CHANNELS
0dB PREEMPHASIS 200 BACK TERMINATION
150mV/div
100ps/div
AMBIENT TEMPERATURE (C)
OUTPUT EYE DIAGRAM AT 2.25Gbps SHORT LOW-LOSS SMA CABLE
MAX3845 toc04
OUTPUT EYE DIAGRAM AT 1.65Gbps 6dB LOSS, 24AWG, 25ft TWIN-AX CABLE
MAX3845 toc05
OUTPUT EYE DIAGRAM AT 2.25Gbps 6dB LOSS, 24AWG, 25ft TWIN-AX CABLE
MAX3845 toc06
0dB PREEMPHASIS 200 BACK TERMINATION
6dB PREEMPHASIS 200 BACK TERMINATION
6dB PREEMPHASIS 200 BACK TERMINATION
150mV/div
150mV/div
150mV/div
80ps/div
100ps/div
80ps/div
OUTPUT EYE DIAGRAM AT 1.65Gbps THROUGH 2m DVI TO HDMI CABLE
MAX3845 toc07
JITTER vs. INPUT-SIDE CABLE LOSS AT 825 MHz
140 120 JITTER (psP-P) DATA RATE = 1.65Gbps 200 BACK TERMINATION
MAX3845 toc08
JITTER vs. OUTPUT-SIDE CABLE LOSS AT 825 MHz
DATA RATE = 1.65Gbps 200 BACK TERMINATION 3dB PREEMPHASIS 0dB PREEMPHASIS
MAX3845 toc09
6dB PREEMPHASIS 200 BACK TERMINATION
160
120 100 80 60 40 20 0 6dB PREEMPHASIS
150mV/div
100 80 60 40 20 0 0 2 4 CABLE LOSS (dB) 6 8
JITTER (psP-P)
100ps/div
0
2
4 CABLE LOSS (dB)
6
8
4
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Typical Operating Characteristics (continued)
(Typical values are at VCC = +3.3V, TA = +25C, data pattern = 210 - 1 PRBS + 20 ones + 210 - 1 PRBS (inverted) + 20 zeros, unless otherwise noted.)
DIFFERENTIAL-INPUT RETURN LOSS vs. FREQUENCY
MAX3845 toc10
MAX3845
TEMP VOLTAGE vs. JUNCTION TEMPERATURE
MAX3845 toc11
POWER DISSIPATION vs. AMBIENT TEMPERATURE
ALL INPUTS/OUTPUTS ACTIVE, PREEMPHASIS SAME ON ALL OUTPUT CHANNELS
MAX3845 toc12
0 -5 -10 GAIN (dB)
1.6 1.5 1.4 TEMP (V) 1.3 1.2 1.1 1.0 0.9 0.8
3000 2500 POWER DISSIPATION (mW) 2000 1500 1000 500 0 0dB PREEMPHASIS OUT_LEVEL = LOW 6dB PREEMPHASIS OUT_LEVEL = HIGH
-15 -20 -25 -30 -35 -40 0 500 1000 1500 2000 2500 3000 FREQUENCY (MHz)
-10
10
30
50
70
90
110 130 150
-10
5
20
35
50
65
80
JUNCTION TEMPERATURE (C)
AMBIENT TEMPERATURE (C)
Pin Description
PIN 1, 4, 7, 10, 97, 100 NAME VCC1 IN1_B+, IN1_C+, IN1_D+, IN1_A+ IN1_B-, IN1_C-, IN1_D-, IN1_AFUNCTION Positive Power-Supply Connection. Powers input channel 1 and output channels 1 and 2.
2, 5, 8, 98
Noninverting TMDS CML Input, Channel 1
3, 6, 9, 99
Inverting TMDS CML Input, Channel 1
11 12 13 14
Power-Down, LVTTL/LVCMOS Input. Force high or leave open to power down input channel 1. Force PWRDWN_1 low to enable input channel 1. The MAX3845 powers down if both PWRDWN_1 and PWRDWN_2 are forced high or left open. VCC3 LOSMUTE_EN TEMP Positive Power-Supply Connection. Powers the temp-sense circuitry. LOS MUTE Enable Input. Connect to VCC for typical operation. Connect to GND to disable the LOS MUTE function. Junction Temperature Sensor. Attach a ground-referenced voltage DMM to this pin to measure the die's junction temperature (see the VCC3 pin description). Leave open if not used.
15 16, 19, 22, 25, 26, 29
Power-Down, LVTTL/LVCMOS Input. Force high or leave open to power down input channel 2. Force PWRDWN_2 low to enable input channel 2. The MAX3845 powers down if both PWRDWN_1 and PWRDWN_2 are forced high or left open. VCC2 Positive Power-Supply Connection. Powers input channel 2 and output channels 3 and 4.
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Pin Description (continued)
PIN 17, 20, 23, 27 NAME IN2_A+, IN2_B+, IN2_C+, IN2_D+ IN2_A-, IN2_B-, IN2_C-, IN2_DIN_SEL4, IN_SEL3, IN_SEL2, IN_SEL1 PREEMPH4, PREEMPH3, PREEMPH2, PREEMPH1 HOTPLUG4, HOTPLUG3, HOTPLUG2, HOTPLUG1 FUNCTION
Noninverting TMDS, CML Input, Channel 2
18, 21, 24, 28
Inverting TMDS, CML Input, Channel 2
30, 61, 65, 96
Input Select, LVTTL Input. Force high to select input channel 1. Force low to select input channel 2. Leave open to disable the output channel.
31, 62, 64, 95
Preemphasis Select, LVTTL/LVCMOS Input. Force high for 6dB of output preemphasis. Leave open for 3dB of output preemphasis. Force low for 0dB of output preemphasis (normal).
32, 46, 80, 94
Hotplug Sense Input. Connect this pin to the display's HOTPLUGx signal (buffered) to allow automatic power-down of the associated output when the display is disconnected. A low-cost quad 5V, noninverting CMOS gate (74ACT32 series) is recommended to buffer the MAX3845 from the HOTPLUGx pin to match HOTPLUG level specifications. If this feature is not used, connect to VCC.
33, 36, 39, 42, 45, 47, 50, 51, 54, 57, 60
GND2
Supply Ground. Ground connection for input channel 2 and output channels 3 and 4.
34, 37, 40, 43
OUT4_D-, OUT4_C-, OUT4_B-, OUT4_AOUT4_D+, OUT4_C+, OUT4_B+, OUT4_A+ OUT3_D-, OUT3_C-, OUT3_B-, OUT3_A-, OUT3_D+, OUT3_C+, OUT3_B+, OUT3_A+,
Inverting TMDS, CML Output, Channel 4
35, 38, 41, 44
Noninverting TMDS, CML Output, Channel 4
48, 52, 55, 58
Inverting TMDS, CML Output, Channel 3
49, 53, 56, 59
Noninverting TMDS, CML Output, Channel 3
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Pin Description (continued)
PIN 63 NAME OUT_LEVEL FUNCTION Output Level Select, LVTTL/LVCMOS Input. Force pin low when no back termination is used (11mA of tail current). Force pin high when 200 back termination resistors are used (14mA of tail current).
MAX3845
66, 69, 72, 75, 76, 79, 81, 84, 87, 90, 93
GND1
Supply Ground. Ground connection for input channel 1 and output channels 1 and 2.
67, 70, 73, 77
OUT2_D-, OUT2_C-, OUT2_B-, OUT2_AOUT2_D+, OUT2_C+, OUT2_B+, OUT2_A+ OUT1_D-, OUT1_C-, OUT1_B-, OUT1_AOUT1_D+, OUT1_C+, OUT1_B+, OUT1_A+ EP
Inverting TMDS, CML Output, Channel 2
68, 71, 74, 78
Noninverting TMDS, CML Output, Channel 2
82, 85, 88, 91
Inverting TMDS, CML Output, Channel 1
83, 86, 89, 92
Noninverting TMDS, CML Output, Channel 1
--
Ground. The exposed pad must be soldered to the circuit board ground for proper thermal and electrical operation.
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Detailed Description
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 output buffers with selectable preemphasis, HOTPLUG detection, and channel selection control (Figure 1).
Applications Information
MAX3845 in HDMI 1.3 Systems
The MAX3845 is designed and characterized to operate from 250Mbps to 1.65Gbps. HDMI 1.3 specifies up to 2.25Gbps for 1080p "deep color" and allows a maximum 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.
MAX3845 in HDCP Systems
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 display). 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 displays, 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.
Fixed Input Equalization
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 approximately 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
Limiting amplifiers follow the equalizer block to ensure proper signal levels are achieved for the multiplexers.
Loss-of-Signal (LOS) Detectors
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 amplitude is smaller than 150mVP-P (typical) at IN1_B, all output channels selected to input 1 are muted. Likewise, if a signal smaller than 150mVP-P (typical) is at IN2_C, all output channels selected to input 2 are muted.
Output Level Control, Back Termination, and AC-Coupling
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 termination resistors to be used on the outputs. The use of back terminations is highly recommended for best signal integrity (see Figures 2 and 3). If OUT_LEVEL is set low, the standard output drive current (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 termination resistors. Two options are available: a differential back termination resistor or two single-ended pullup resistors (see Figures 2 and 3).
Multiplexers
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.
Preemphasis Drivers
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.
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
OUT_LEVEL 2:4 DVI FANOUT SWITCH AND CABLE DRIVER OUTPUT MACRO 1
PE
OUT1_[A-D] HOTPLUG1 PREEMPH1
DVI OR HDMI CONNECTOR
EXAMPLE: MAX3815 OUTPUT MACRO 2
IN_SEL1
EQ
IN1_[A-D]
EQ LOS 1 ->MUTE
LA PE INPUT MACRO 1 OUT2_[A-D] HOTPLUG2 PREEMPH2 IN_SEL2 DVI OR HDMI CONNECTOR
CLKLOS
PWRDWN_1
PD
LOSMUTE_EN EXAMPLE: MAX3815
OUTPUT MACRO 3
PE EQ IN2_[A-D] EQ LOS 2 ->MUTE LA
OUT3_[A-D] HOTPLUG3 PREEMPH3 IN_SEL3
DVI OR HDMI CONNECTOR
CLKLOS
PWRDWN_2
PD
INPUT MACRO 2
OUTPUT MACRO 4
PE TEMP (DIE TEMP SENSE) ANALOG TEMP SENSE
OUT4_[A-D] HOTPLUG4 PREEMPH4 IN_SEL4
DVI OR HDMI CONNECTOR
POWER-DOWN LOGIC FOR EACH OF 4 OUTPUT MACROS PWRDWN_ [OUTPUT MACRO x], WHERE x = 1, 2, 3, OR 4, IF: DECODER HIGH IN_SELx LOW OPEN [PWRDWN_1 = LOW] OR [LOS 1 = HIGH] AND [IN_SELx = HIGH] OR [PWRDWN_2 = HIGH] OR [LOS 2 = HIGH] AND [IN_SELx = LOW] OR [IN_SELx = OPEN] R [HOTPLUGx = LOW OR OPEN] 2xR
ON-CHIP SIGNAL: POWER-DOWN OUTPUT MACRO x
Figure 1. Functional Diagram
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
+3.3V
MAX3845
50 TMDS OUTPUT PAIR 200* OR 300* 50
Z0(DIFF) = 100
Rx
TMDS RECEIVER
*BACK TERMINATION RESISTOR IS LOCATED AS CLOSE AS POSSIBLE TO THE MAX3845.
Figure 2. DC-Coupled Differential Back Termination
+3.3V
+3.3V
MAX3845
100* TMDS OUTPUT PAIR 0.1F 100* 0.1F Z0(DIFF) = 100 Rx 50 50
TMDS RECEIVER
*BACK TERMINATION RESISTORS ARE LOCATED AS CLOSE AS POSSIBLE TO THE MAX3845.
Figure 3. AC-Coupled Single-Ended Back Termination
Back termination greatly reduces signal degradation caused by reflections coming off DVI/HDMI connectors and any other transmission line discontinuities. Much of the reflected energy off a DVI connector, for example, is absorbed by the back termination resistance rather than reflected forward, causing eye closure. For the cases shown in Figures 2 and 3, the return loss is approximately 9.5dB. In other words, about 90% of the reflected energy is absorbed by the back termination resistors. Maxim strongly recommends using back termination to maximize the MAX3845's performance.
The differential back termination options reduce the common-mode output voltage seen by the TMDS receiver to approximately VCC - 350mV (Table 1). The single-ended back termination option allows for AC-coupling between the MAX3845 and a TMDS receiver, so long as the TMDS receiver is tolerant of an input common-mode voltage equal to VCC (HDMI 1.2 or later).
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Table 1. Output Levels With and Without Back Termination
CONDITIONS VOLTAGES AT THE INPUT OF THE TMDS RECEIVER (TYPICAL) VDIFF 1100mVP-P 950mVP-P 1050mVP-P 950mVP-P VCM VCC - 275mV VCC - 350mV VCC - 350mV VCC VH VCC VCC - 120mV VCC - 90mV VCC + 240mV VL VCC - 550mV VCC - 585mV VCC - 615mV VCC - 240mV
PREEMPHx = LOW, OUT_LEVEL = LOW (Output Drive Current = 11mA) No back termination Differential 200 Differential 300 back terminations (DC-coupled) back terminations (DC-coupled) back terminations (AC-coupled) PREEMPHx = LOW, OUT_LEVEL = HIGH (Output Drive Current = 14mA)
Single-ended, 2x 100
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: TJ = (VTEMP - 0.93) x 297 Also see the Typical Operating Characteristics section for more information.
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 output is powered down. If HOTPLUGx is higher than VCC - 0.2V, up to 5.5V, the associated output is powered down.
Activating an Output
Several things must occur for an output to be active. Table 2 lists the required inputs to enable an output.
Power-Down
The power-down inputs (PWRDWN_1 and PWRDWN_2) reduce power consumption by powering down the chosen input and all outputs that are selected to that input. For example, when output channels 1 and 4 are selected to transmit input channel 2, and channel 2 is powered down, both outputs 1 and 4 are also powered down.
Cable Selection
Good quality cable is recommended for good performance. Deterministic jitter (DJ) can be caused by differential-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.
Table 2. Output Enable Requirements
OUTPUT x STATE INPUT 1 INPUT 2 IN_SELx CONDITION HIGH LOW HOTPLUGx CONDITION HIGH HIGH PWRDWN_1 CONDITION LOW Don't care PWRDWN_2 CONDITION Don't care LOW LOS 1 CONDITION LOW Don't care LOS 2 CONDITION Don't care LOW
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Interface Models Layout Considerations
The data inputs and outputs are the MAX3845's most critical paths, and great care should be taken to minimize discontinuities on these transmission lines between the connector and the IC. Here are some suggestions for maximizing the performance of the MAX3845: * Maintain 100 differential transmission line impedance into and out of the MAX3845. * The data and clock inputs should be wired directly between the cable connector and IC without stubs. * An uninterrupted ground plane should be positioned beneath the high-speed I/Os. * Ground path vias should be placed close to the IC and the input/output interfaces to allow a return current path to the IC and the DVI/HDMI cable. * Use good high-frequency layout techniques and multilayer boards with an uninterrupted ground plane to minimize EMI and crosstalk. For more information, refer to the schematic and board layers of the Maxim evaluation kit, MAX3845EVKIT.
VCC VCC
MAX3845
50
TMDS INPUT+
50
EQUALIZATION NETWORK
TMDS INPUT-
Figure 4. Simplified Input Circuit Schematic
MAX3845
TMDS OUTPUT+ TMDS OUTPUT-
Exposed-Pad Package and Thermal Considerations
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 incorporated into the PCB design. The device's temperaturesense pin (TEMP) allows estimation of the junction temperature to be made while the MAX3845 is operating. This information can be used to determine if the PCB layout is dissipating heat properly.
TVS*
TVS*
*TVS IS A "TRANSIENT VOLTAGE SUPPRESSOR" CLAMP-CIRCUIT.
Figure 5. Simplified Output Circuit Schematic
12
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DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Pin Configuration
PREEMPH1 HOTPLUG1 HOTPLUG2 OUT1_C+ OUT1_D+ OUT1_A+ OUT1_AOUT1_B+ OUT2_A+ OUT1_COUT1_DOUT1_BOUT2_AGND1 IN_SEL1
MAX3845
GND1
GND1
GND1
GND1
GND1
100
99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76
+
VCC1 INT1_B+ INT1_BVCC1 IN1_C+ IN1_CVCC1 IN1_D+ IN1_DVCC1 PWRDWN_1 VCC3 LOSMUTE_EN TEMP PWRDWN_2 VCC2 IN2_A+ IN2_AVCC2 IN2_B+ IN2_BVCC2 IN2_C+ IN2_CVCC2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51
GND1
VCC1
TOP VIEW
IN1_A+ VCC1
IN1_A-
GND1 OUT2_B+ OUT2_BGND1 OUT2_C+ OUT2_CGND1 OUT2_D+ OUT2_DGND1 IN_SEL2 PREEMPH2 OUT_LEVEL PREEMPH3 IN_SEL3 GND2 OUT3_A+ OUT3_AGND2 OUT3_B+ OUT3_BGND2 OUT3_C+ OUT3_CGND2
MAX3845
26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
IN2_D+ IN2_DVCC2 IN_SEL4 PREEMPH4 HOTPLUG4
OUT4_DOUT4_D+ GND2 OUT4_COUT4_C+ GND2 OUT4_B-
OUT4_AOUT4_A+ GND2 HOTPLUG3 GND2
TQFP-EP* *EXPOSED PAD MUST BE CONNECTED TO GROUND.
______________________________________________________________________________________
OUT3_D+ GND2
OUT4_B+
GND2
OUT3_D-
VCC2
GND2
13
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Typical Operating Circuits (continued)
HDCP* APPLICATION HDMI/DVI CABLE
MAX3845
DVI/HDMI DUAL 1:4 SWITCH CONFIGURATION
MOVIE WITH HDCP
HDMI/DVI CABLE
OFF
MOVIE WITH HDCP Blu-rayTM, HD-DVD, CABLE STB, SATELLITE STB SPORTS WITH HDCP Blu-ray, HD-DVD, CABLE STB, SATELLITE STB
HDMI/DVI CABLE
HDMI/DVI CABLE HDMI/DVI CABLE
SPORTS WITH HDCP
HDMI/DVI CABLE
OFF
DRIVER SELECTS (8) IN_SELx: HIGH = INPUT 1, OPEN = OFF, LOW = INPUT 2 PREEMPHx: HIGH = 6dB, OPEN = 3dB, LOW = 0dB
* BECAUSE THE MAX3845 IS A TRANSPARENT SWITCH, HDCP SOURCES CAN ONLY BE CONNECTED TO ONE HDCP-COMPLIANT DISPLAY AT A TIME AND CANNOT BE FANNED OUT THROUGH THE MAX3845. Blu-ray is a trademark of Blu-ray Disc Association.
14
______________________________________________________________________________________
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Typical Operating Circuits (continued)
NON-HDCP APPLICATION HDMI/DVI CABLE
MAX3845
MAX3845
DVI/HDMI 2:4 FANOUT BUFFER
VIDEO FOOTAGE VIDEO DISPLAY
HDMI/DVI CABLE PCB TRACES
VIDEO FOOTAGE VIDEO CAPTURE CARD ON PC/MAC
GRAPHICS ASIC SCALING AND PICTURE PROCESSING ENGINE WITH TDMS OUTPUT
PCB TRACES EQ COMPUTER GRAPHICS VIDEO CARD ON PC/MAC LONG HDMI CABLE
HDMI/DVI CABLE
COMPUTER GRAPHICS VIDEO DISPLAY
MAX3815
DVI/HDMI EQUALIZER HDMI/DVI CABLE COMPUTER GRAPHICS VIDEO DISPLAY
DRIVER SELECTS (8) IN_SELx: HIGH = INPUT 1, OPEN = OFF, LOW = INPUT 2 PREEMPHx: HIGH = 6dB, OPEN = 3dB, LOW = 0dB
FOR APPLICATIONS THAT ARE NOT HDCP ENCODED, THE MAX3845 CAN BE USED TO FAN OUT DVI AND HDMI SIGNALS.
______________________________________________________________________________________
15
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Typical Operating Circuits (continued)
MAX3845
4 x 4 MATRIX APPLICATION DVI/HDMI DUAL 1:4 SWITCH CONFIGURATION MAX3845 DVI/HDMI 2:4 FANOUT BUFFER OUTPUT 1
INPUT 1
OUTPUT 2
INPUT 2
INPUT 3 26 TOP VIEW 1 INPUT 4 50
OUTPUT 3
1 26 26 SIDE VIEW PART A 100 76 DRIVER SELECTS 2x(8) IN_SELx (PART A): HIGH = INPUT 2, OPEN = OFF, LOW = INPUT 4 IN_SELx (PART B): HIGH = INPUT 1, OPEN = OFF, LOW = INPUT 3 PREEMPHx: HIGH = 6dB, OPEN = 3dB, LOW = 0dB 50 50
OUTPUT 4
PART B
FOR 4 x 4 MATRIX OPERATION, TWO MAX3845 PARTS ARE LOCATED ON EITHER SIDE OF THE BOARD WITH THE AXIS OF ROTATION ABOUT PINS 13 AND 63.
16
______________________________________________________________________________________
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Typical Operating Circuits (continued)
MAX3845
2:8 FANOUT/SWITCH APPLICATION DVI/HDMI 2:4 FANOUT SWITCH AND CABLE DRIVER OUTPUT 1
MAX3845
OUTPUT 2
OUTPUT 3
MAX3814
INPUT 1 DVI/HDMI CABLE EQUALIZER AND DRIVER (USE 200 BACK TERM)
(8) MINIMUM LOSS POWER SPLITTERS
OUTPUT 4
MAX3845
DVI/HDMI 2:4 FANOUT SWITCH AND CABLE DRIVER OUTPUT 5
MAX3814
INPUT 2 DVI/HDMI CABLE EQUALIZER AND DRIVER (USE 200 BACK TERM)
(8) MINIMUM LOSS POWER SPLITTERS
OUTPUT 6
50 MATCHED MINIMUM LOSS POWER SPLITTER: THROUGH LOSS (ANY PORT TO ANY PORT) IS 6dB. 16 SIGNAL 1 Z0 = 50 16 SIGNAL 3 Z0 = 50
OUTPUT 7
16
OUTPUT 8 SIGNAL 2 Z0 = 50
______________________________________________________________________________________
17
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver MAX3845
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, 100L TQFP 14x14x1.00mm WITH EXPOSED PAD OPTION
21-0116
D
1
2
18
______________________________________________________________________________________
14x14x1.00L TQPF, EXP. PAD.EPS
DVI/HDMI 2:4 TMDS Fanout Switch and Cable Driver
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX3845
PACKAGE OUTLINE, 100L TQFP 14x14x1.00mm WITH EXPOSED PAD OPTION
21-0116
D
2
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
(c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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