AD8197ASTZ [ADI]

4:1 HDMI/DVI Switch with Equalization; 4 : 1 HDMI / DVI开关,具有均衡
AD8197ASTZ
型号: AD8197ASTZ
厂家: ADI    ADI
描述:

4:1 HDMI/DVI Switch with Equalization
4 : 1 HDMI / DVI开关,具有均衡

复用器 开关 复用器或开关 信号电路
文件: 总32页 (文件大小:711K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
4:1 HDMI/DVI Switch with Equalization  
Preliminary Data Sheet  
AD8197  
FEATURES  
APPLICATIONS  
Multiple input displays  
Projectors  
A/V receivers  
Four inputs, one output HDMI™/DVI links  
Enables HDMI 1.3-compliant receiver  
Pin-to-pin compatible with the AD8191  
Four TMDS channels per link  
Set-top boxes  
Supports 250 Mbps to 2.25 Gbps data rates  
Supports 25 MHz to 225 MHz pixel clocks  
Advanced television (HDTV) sets  
Equalized inputs for operation with long HDMI cables  
(20 meters at 2.25 Gbps)  
FUNCTIONAL BLOCK DIAGRAM  
Fully buffered unidirectional inputs/outputs  
Globally switchable, 50 Ω on-chip terminations  
Pre-emphasized outputs  
Low added jitter  
Single-supply operation (3.3 V)  
Four auxiliary channels per link  
Bidirectional unbuffered inputs/outputs  
Flexible supply operation (3.3 V to 5 V)  
HDCP standard compatible  
Allows switching of DDC bus and two additional signals  
Multiple channel bundling modes  
1x (4:1) HDMI/DVI link switch (default)  
2x (8:1) TMDS channel and auxiliary signal switch  
1x (16:1) TMDS channel and auxiliary signal switch  
Output disable feature  
Reduced power dissipation  
Figure 1.  
Removable output termination  
TYPICAL APPLICATION  
Allows building of larger arrays  
Two AD8197s support HDMI/DVI dual-link  
Standards compliant: HDMI receiver, HDCP, DVI  
Serial (I2C® slave) and parallel control interface  
100-lead, 14 mm × 14 mm LQFP, Pb-free package  
Figure 2. Typical HDTV Application  
The AD8197 is provided in a 100-lead LQFP, Pb-free, surface  
mount package specified to operate over the −40°C to +85°C  
temperature range.  
GENERAL DESCRIPTION  
The AD8197 is an HDMI/DVI switch featuring equalized  
TMDS inputs and pre-emphasized TMDS outputs, ideal for  
systems with long cable runs. Outputs can be set to a high  
impedance state to reduce the power dissipation and/or allow  
the construction of larger arrays using the wire-OR technique.  
Flexible channel bundling modes (for both the TMDS channels  
and the auxiliary signals) allow the AD8197 to be configured as a  
4:1 single HDMI/DVI link switch, a dual 8:1 switch, or a single  
16:1 switch.  
PRODUCT HIGHLIGHTS  
1. Supports data rates up to 2.25 Gbps, enabling greater than  
1080p HDMI formats with deep color, and UXGA (1600 ×  
1200) DVI resolutions.  
2. Input cable equalizer enables use of long cables at the input  
(more than 20 meters of 24 AWG cable at 2.25 Gbps).  
3. Auxiliary switch routes a DDC bus and two additional signals  
for a single-chip, HDMI 1.3 receive-compliant solution.  
PrA  
Information furnished by Analog Devices is believed to be accurate and reliable. However, no  
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other  
rights of third parties that may result from its use. Specifications subject to change without notice. No  
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.  
Trademarks and registeredtrademarks arethe property of their respective owners.  
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.  
Tel: 781.329.4700  
Fax: 781.461.3113  
www.analog.com  
©2006 Analog Devices, Inc. All rights reserved.  
 
AD8197  
Preliminary Technical Data  
TABLE OF CONTENTS  
Features .............................................................................................. 1  
Read Procedure........................................................................... 17  
Switching/Update Delay............................................................ 17  
Parallel Control Interface .............................................................. 18  
Serial Interface Configuration Registers ..................................... 19  
High Speed Device Modes Register......................................... 19  
Auxiliary Device Modes Register............................................. 20  
Receiver Settings Register ......................................................... 22  
Input Termination Pulse Register 1 and Register 2 ............... 22  
Receive Equalizer Register 1 and Register 2 ........................... 22  
Transmitter Settings Register.................................................... 22  
Parallel Interface Configuration Registers .................................. 23  
High Speed Device Modes Register......................................... 23  
Auxiliary Device Modes Register............................................. 23  
Receiver Settings Register ......................................................... 24  
Input Termination Pulse Register 1 and Register 2 ............... 24  
Receive Equalizer Register 1 and Register 2 ........................... 24  
Transmitter Settings Register.................................................... 24  
Application Information................................................................ 25  
Pinout........................................................................................... 25  
Cable Lengths and Equalization............................................... 25  
PCB Layout Guidelines.............................................................. 26  
Outline Dimensions....................................................................... 30  
Ordering Guide .......................................................................... 30  
Applications....................................................................................... 1  
Functional Block Diagram .............................................................. 1  
Typical Application........................................................................... 1  
General Description......................................................................... 1  
Product Highlights ........................................................................... 1  
Specifications..................................................................................... 3  
Absolute Maximum Ratings............................................................ 5  
Thermal Resistance ...................................................................... 5  
Maximum Power Dissipation ..................................................... 5  
ESD Caution.................................................................................. 5  
Pin Configuration and Function Descriptions............................. 6  
Typical Performance Characteristics ............................................. 9  
Theory of Operation ...................................................................... 13  
Introduction................................................................................ 13  
Input Channels............................................................................ 13  
Output Channels ........................................................................ 13  
High Speed (TMDS) Switching Modes ................................... 14  
Auxiliary Switch.......................................................................... 14  
Auxiliary (Low Speed) Switching Modes................................ 15  
Serial Control Interface.................................................................. 16  
Reset ............................................................................................. 16  
Write Procedure .......................................................................... 16  
PrA| Page 2 of 32  
Preliminary Data Sheet  
SPECIFICATIONS  
AD8197  
TA = 27°C, AVCC = 3.3 V, VTTI = 3.3 V, VTTO = 3.3 V, DVCC = 3.3 V, AMUXVCC = 5 V, AVEE = 0 V, DVEE = 0 V, differential input  
swing = 1000 mV, TMDS outputs terminated with external 50 Ω resistors to 3.3 V, unless otherwise noted.  
Table 1.  
Parameter  
Conditions/Comments  
Min  
Typ Max  
Unit  
DYNAMIC PERFORMANCE  
Maximum Data Rate (DR) per Channel  
Bit Error Rate (BER)  
Added Deterministic Jitter  
Added Random Jitter  
Differential Intrapair Skew  
Differential Interpair Skew1  
EQUALIZATION PERFORMANCE  
Receiver (Highest Setting)2  
Transmitter (Highest Setting)3  
INPUT CHARACTERISTICS  
Input Voltage Swing  
NRZ  
2.25  
Gbps  
PRBS 223 − 1  
10−9  
TBD  
TBD  
TBD  
TBD  
DR ≤ 2.25 Gbps, PRBS 223 − 1  
ps (p-p)  
ps (rms)  
ps  
At output  
At output  
ps  
Boost frequency = 825 MHz  
Boost frequency = 825 MHz  
12  
6
dB  
dB  
Differential  
150  
AVCC − 800  
1200  
AVCC  
mV  
mV  
Input Common-Mode Voltage (VICM  
OUTPUT CHARACTERISTICS  
High Voltage Level  
)
Single-ended high speed channel  
Single-ended high speed channel  
AVCC − 10  
AVCC − 600  
75  
AVCC + 10  
mV  
Low Voltage Level  
Rise/Fall Time (20% to 80%)  
AVCC − 400 mV  
135 200  
ps  
INPUT TERMINATION  
Resistance  
Single-ended  
50  
Ω
AUXILIARY CHANNELS  
On Resistance, RAUX  
On Capacitance, CAUX  
Input/Output Voltage Range  
POWER SUPPLY  
AVCC  
100  
8
Ω
pF  
V
DC bias = 2.5 V, ac voltage = 3.5 V, f = 100 kHz  
Operating range  
DVEE  
3
AMUXVCC  
3.6  
3.3  
V
QUIESCENT CURRENT  
AVCC  
Outputs disabled  
30  
48  
88  
5
35  
72  
40  
60  
44  
64  
mA  
mA  
mA  
mA  
mA  
mA  
Outputs enabled, no pre-emphasis  
Outputs enabled, maximum pre-emphasis  
Input termination on4  
Output termination on, no pre-emphasis  
Output termination on, maximum  
pre-emphasis  
100 110  
VTTI  
VTTO  
40  
40  
80  
54  
46  
90  
DVCC  
AMUXVCC  
3.2  
7
8
mA  
mA  
0.01 0.1  
POWER DISSIPATION  
Outputs disabled  
Outputs enabled, no pre-emphasis  
Outputs enabled, maximum pre-emphasis  
115  
384  
704  
271 361  
574 671  
910 1050  
mW  
mW  
mW  
TIMING CHARACTERISTICS  
Switching/Update Delay  
High speed switching register: HS_CH  
All other configuration registers  
200  
1.5  
ms  
ms  
ns  
RESET Pulse Width  
50  
PrA | Page 3 of 32  
 
 
AD8197  
Preliminary Technical Data  
Parameter  
Conditions/Comments  
Min  
Typ Max  
Unit  
SERIAL CONTROL INTERFACE5  
Input High Voltage, VIH  
Input Low Voltage, VIL  
Output High Voltage, VOH  
Output Low Voltage, VOL  
PARALLEL CONTROL INTERFACE  
Input High Voltage, VIH  
Input Low Voltage, VIL  
2
V
V
V
V
0.8  
0.4  
2.4  
2
V
V
0.8  
1 Differential interpair skew is measured between the TMDS pairs of a single link.  
2 AD8197 output meets the transmitter eye diagram as defined in the DVI Standard Revision 1.0 and the HDMI Standard Revision 1.3.  
3 Cable output meets the receiver eye diagram mask as defined in the DVI Standard Revision 1.0 and the HDMI Standard Revision 1.3.  
4 Typical value assumes only the selected HDMI/DVI link is active with nominal signal swings and that the unselected HDMI/DVI links are deactivated. Minimum and  
maximum limits are measured at the respective extremes of input termination resistance and input voltage swing.  
5 The AD8197 is an I2C slave and its serial control interface is based on the 3.3 V I2C bus specification.  
PrA| Page 4 of 32  
Preliminary Data Sheet  
AD8197  
ABSOLUTE MAXIMUM RATINGS  
Table 2.  
THERMAL RESISTANCE  
θJA is specified for the worst-case conditions: a device soldered  
in a 4-layer JEDEC circuit board for surface-mount packages.  
θJC is specified for no airflow.  
Parameter  
Rating  
AVCC to AVEE  
DVCC to DVEE  
DVEE to AVEE  
VTTI  
VTTO  
AMUXVCC  
3.7 V  
3.7 V  
0.3 V  
AVCC + 0.6 V  
AVCC + 0.6 V  
5.5 V  
Table 3. Thermal Resistance  
Package Type  
θJA  
θJC  
Unit  
100-Lead LQFP  
56  
19  
°C/W  
Internal Power Dissipation  
High Speed Input Voltage  
2.2 W  
AVCC − 1.4 V < VIN  
AVCC + 0.6 V  
<
MAXIMUM POWER DISSIPATION  
The maximum power that can be safely dissipated by the AD8197  
is limited by the associated rise in junction temperature. The  
maximum safe junction temperature for plastic encapsulated  
devices is determined by the glass transition temperature of the  
plastic, approximately 150°C. Temporarily exceeding this limit  
may cause a shift in parametric performance due to a change in  
the stresses exerted on the die by the package.  
High Speed Differential Input Voltage  
Low Speed Input Voltage  
2.0 V  
DVEE − 0.3 V < VIN  
AMUXVCC + 0.6 V  
DVEE − 0.3 V < VIN  
DVCC + 0.6 V  
−65°C to +125°C  
−40°C to +85°C  
150°C  
<
I2C and Parallel Logic Input Voltage  
<
Storage Temperature Range  
Operating Temperature Range  
Junction Temperature  
Exceeding a junction temperature of 175°C for an extended  
period can result in device failure. To ensure proper operation, it  
is necessary to observe the maximum power rating as determined  
by the coefficients in Table 3.  
Stresses above those listed under Absolute Maximum Ratings  
may cause permanent damage to the device. This is a stress  
rating only; functional operation of the device at these or any  
other conditions above those indicated in the operational  
section of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods may affect  
device reliability.  
ESD CAUTION  
PrA | Page 5 of 32  
 
 
AD8197  
Preliminary Technical Data  
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS  
Figure 3. Pin Configuration  
Table 4. Pin Function Descriptions  
Pin No.  
Mnemonic  
Type1  
Power  
HS I  
Description  
1, 13, 22, 54, 63, 75  
AVCC  
Positive Analog Supply. 3.3 V nominal.  
High Speed Input Complement.  
High Speed Input.  
2
IN_B0  
IP_B0  
AVEE  
3
HS I  
4, 10, 16, 25, 51, 60, 66, 72  
Power  
HS I  
Negative Analog Supply. 0 V nominal.  
High Speed Input Complement.  
High Speed Input.  
5
IN_B1  
IP_B1  
VTTI  
6
HS I  
7, 19, 57, 69  
Power  
HS I  
Input Termination Supply. Nominally connected to AVCC.  
High Speed Input Complement.  
High Speed Input.  
8
IN_B2  
IP_B2  
IN_B3  
IP_B3  
IN_A0  
IP_A0  
9
HS I  
11  
12  
14  
15  
HS I  
High Speed Input Complement.  
High Speed Input.  
HS I  
HS I  
High Speed Input Complement.  
High Speed Input.  
HS I  
PrA| Page 6 of 32  
 
Preliminary Data Sheet  
AD8197  
Pin No.  
17  
Mnemonic  
Type1  
HS I  
Description  
IN_A1  
IP_A1  
High Speed Input Complement.  
High Speed Input.  
18  
HS I  
20  
IN_A2  
IP_A2  
HS I  
High Speed Input Complement.  
High Speed Input.  
21  
HS I  
23  
IN_A3  
IP_A3  
HS I  
High Speed Input Complement.  
24  
HS I  
High Speed Input.  
26  
I2C_ADDR0  
I2C_ADDR1  
I2C_ADDR2  
DVEE  
Control  
Control  
Control  
Power  
Control  
Control  
Power  
HS O  
HS O  
Power  
HS O  
HS O  
HS O  
HS O  
HS O  
HS O  
Control  
Control  
Control  
Control  
Control  
Control  
HS I  
I2C Address 1st LSB.  
I2C Address 2nd LSB.  
I2C Address 3rd LSB.  
27  
28  
29, 95  
30  
Negative Digital and Auxiliary Multiplexer Power Supply. 0 V nominal.  
Quad Switching Mode High Speed Source Selection Parallel Interface LSB.  
Quad Switching Mode High Speed Source Selection Parallel Interface MSB.  
Positive Digital Power Supply. 3.3 V nominal.  
High Speed Output Complement.  
High Speed Output.  
PP_CH0  
PP_CH1  
DVCC  
31  
32, 38, 47  
33  
ON0  
34  
OP0  
35, 41  
36  
VTTO  
Output Termination Supply. Nominally connected to AVCC.  
High Speed Output Complement.  
High Speed Output.  
ON1  
37  
OP1  
39  
ON2  
High Speed Output Complement.  
High Speed Output.  
40  
OP2  
42  
ON3  
High Speed Output Complement.  
High Speed Output.  
43  
OP3  
44  
RESET  
PP_PRE0  
PP_PRE1  
PP_OCL  
I2C_SCL  
I2C_SDA  
IN_D0  
IP_D0  
IN_D1  
IP_D1  
IN_D2  
IP_D2  
IN_D3  
IP_D3  
IN_C0  
IP_C0  
Configuration Registers Reset. Normally pulled up to AVCC.  
High Speed Pre-Emphasis Selection Parallel Interface LSB.  
High Speed Pre-Emphasis Selection Parallel Interface MSB.  
High Speed Output Current Level Parallel Interface.  
I2C Clock.  
45  
46  
48  
49  
50  
I2C Data.  
52  
High Speed Input Complement.  
High Speed Input.  
53  
HS I  
55  
HS I  
High Speed Input Complement.  
High Speed Input.  
56  
HS I  
58  
HS I  
High Speed Input Complement.  
High Speed Input.  
59  
HS I  
61  
HS I  
High Speed Input Complement.  
High Speed Input.  
62  
HS I  
64  
HS I  
High Speed Input Complement.  
High Speed Input.  
65  
HS I  
67  
IN_C1  
IP_C1  
HS I  
High Speed Input Complement.  
High Speed Input.  
68  
HS I  
70  
IN_C2  
IP_C2  
HS I  
High Speed Input Complement.  
High Speed Input.  
71  
HS I  
73  
IN_C3  
IP_C3  
HS I  
High Speed Input Complement.  
High Speed Input.  
74  
HS I  
76  
PP_EN  
PP_EQ  
AUX_D3  
Control  
Control  
LS I/O  
High Speed Output Enable Parallel Interface.  
High Speed Equalization Selection Parallel Interface.  
Low Speed Input/Output.  
77  
78  
PrA | Page 7 of 32  
AD8197  
Preliminary Technical Data  
Pin No.  
79  
Mnemonic  
AUX_D2  
AUX_D1  
AUX_D0  
AMUXVCC  
AUX_C3  
Type1  
LS I/O  
LS I/O  
LS I/O  
Power  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
LS I/O  
Control  
Description  
Low Speed Input/Output.  
Low Speed Input/Output.  
Low Speed Input/Output.  
80  
81  
82  
Positive Auxiliary Multiplexer Supply. 5V typical.  
Low Speed Input/Output.  
83  
84  
AUX_C2  
Low Speed Input/Output.  
85  
AUX_C1  
Low Speed Input/Output.  
86  
AUX_C0  
Low Speed Input/Output.  
87  
AUX_COM3  
AUX_COM2  
AUX_COM1  
AUX_COM0  
AUX_B3  
Low Speed Common Input/Output.  
Low Speed Common Input/Output.  
Low Speed Common Input/Output.  
Low Speed Common Input/Output.  
Low Speed Input/Output.  
88  
89  
90  
91  
92  
AUX_B2  
Low Speed Input/Output.  
93  
AUX_B1  
Low Speed Input/Output.  
94  
AUX_B0  
Low Speed Input/Output.  
96  
AUX_A3  
Low Speed Input/Output.  
97  
AUX_A2  
Low Speed Input/Output.  
98  
AUX_A1  
Low Speed Input/Output.  
99  
AUX_A0  
Low Speed Input/Output.  
100  
PP_OTO  
High Speed Output Termination Selection Parallel Interface.  
1 HS = high speed, LS = low speed, I = input, O = output.  
PrA| Page 8 of 32  
Preliminary Data Sheet  
AD8197  
TYPICAL PERFORMANCE CHARACTERISTICS  
TA = 27°C, AVCC = 3.3 V, VTTI = 3.3 V, VTTO = 3.3 V, DVCC = 3.3 V, AMUXVCC = 5 V, AVEE = 0 V, DVEE = 0 V, differential input  
swing = 1000 mV, TMDS outputs terminated with external 50 Ω resistors to 3.3 V, pattern = PRBS 27 − 1, data rate = 2.25 Gbps, unless  
otherwise noted.  
Figure 4. Test Circuit Diagram for RX Eye Diagram  
Figure 7. RX Eye Diagram at TP3, EQ = 6 dB (Cable = 2 meters, 30 AWG)  
Figure 5. RX Eye Diagram at TP2 (Cable = 2 meters, 30 AWG)  
Figure 8. RX Eye Diagram at TP3, EQ = 12 dB (Cable = 20 meters, 24 AWG)  
Figure 6. RX Eye Diagram at TP2 (Cable = 20 meters, 24 AWG)  
PrA | Page 9 of 32  
 
 
 
AD8197  
Preliminary Technical Data  
TA = 27°C, AVCC = 3.3 V, VTTI = 3.3 V, VTTO = 3.3 V, DVCC = 3.3 V, AMUXVCC = 5 V, AVEE = 0 V, DVEE = 0 V, differential input  
swing = 1000 mV, TMDS outputs terminated with external 50 Ω resistors to 3.3 V, pattern = PRBS 27 − 1, data rate = 2.25 Gbps, unless  
otherwise noted.  
Figure 9. Test Circuit Diagram for TX Eye Diagrams  
Figure 10. TX Eye Diagram at TP2, PE = 2 dB  
Figure 12. TX Eye Diagram at TP3, PE = 2 dB (Cable = 2 meters, 30 AWG)  
Figure 11. TX Eye Diagram at TP2, PE = 6 dB  
Figure 13. TX Diagram at TP3, PE = 6 dB (Cable = 10 meters, 28 AWG)  
PrA| Page 10 of 32  
 
Preliminary Data Sheet  
AD8197  
TA = 27°C, AVCC = 3.3 V, VTTI = 3.3 V, VTTO = 3.3 V, DVCC = 3.3 V, AMUXVCC = 5 V, AVEE = 0 V, DVEE = 0 V, differential input  
swing = 1000 mV, TMDS outputs terminated with external 50 Ω resistors to 3.3 V, pattern = PRBS 27 − 1, data rate = 2.25 Gbps, unless  
otherwise noted.  
Figure 14. Jitter vs. Input Cable Length (See Figure 4 for Test Setup)  
Figure 17. Jitter vs. Output Cable Length (See Figure 9 for Test Setup)  
Figure 15. Jitter vs. Data Rate  
Figure 18. Eye Height vs. Data Rate  
Figure 16. Jitter vs. Supply Voltage  
Figure 19. Eye Height vs. Supply Voltage  
PrA | Page 11 of 32  
AD8197  
Preliminary Technical Data  
TA = 27°C, AVCC = 3.3 V, VTTI = 3.3 V, VTTO = 3.3 V, DVCC = 3.3 V, AMUXVCC = 5 V, AVEE = 0 V, DVEE = 0 V, differential input  
swing = 1000 mV, TMDS outputs terminated with external 50 Ω resistors to 3.3 V, pattern = PRBS 27 − 1, data rate = 2.25 Gbps, unless  
otherwise noted.  
Figure 20. Jitter vs. Differential Input Swing  
Figure 23. Jitter vs. Input Common-Mode Voltage  
Figure 21. Jitter vs. Temperature  
Figure 24. Differential Input Termination Resistance vs. Temperature  
Figure 22. Rise and Fall Time vs. Temperature  
PrA| Page 12 of 32  
Preliminary Data Sheet  
AD8197  
THEORY OF OPERATION  
programming the RX_TO bit in the receiver settings register. By  
default, the input termination is enabled. The input  
terminations are enabled and cannot be switched when  
programming the AD8197 through the parallel control  
interface.  
INTRODUCTION  
The AD8197 is a pin-to-pin HDMI 1.3 receive compliant  
replacement for the AD8191. The primary function of the  
AD8197 is to switch one of four (HDMI or DVI) single-link  
sources to one output. Each HDMI/DVI link consists of four  
differential, high speed channels and four auxiliary single-  
ended, low speed control signals. The high speed channels  
include a data-word clock and three transition minimized  
differential signaling (TMDS) data channels running at 10× the  
data-word clock frequency for data rates up to 2.25 Gbps. The  
four low speed control signals are 5 V tolerant bidirectional  
lines that can carry configuration signals, HDCP encryption,  
and other information, depending upon the specific  
application.  
VTTI  
50  
50Ω  
IP_xx  
IN_xx  
CABLE  
EQ  
AVEE  
Figure 25. High Speed Input Simplified Schematic  
All four high speed TMDS channels in a given link are identical;  
that is, the pixel clock can be run on any of the four TMDS  
channels. Transmit and receive channel compensation is  
provided for the high speed channels where the user can  
(manually) select among a number of fixed settings.  
The input equalizer can be manually configured to provide two  
different levels of high frequency boost: 6 dB or 12 dB. The user  
can individually control the equalization level of the eight high  
speed input channels by selectively programming the associated  
RX_EQ bits in the receive equalizer register through the serial  
control interface. Alternately, the user can globally control the  
equalization level of all eight high speed input channels by  
setting the PP_EQ pin of the parallel control interface. No  
specific cable length is suggested for a particular equalization  
setting because cable performance varies widely between  
manufacturers; however, in general, the equalization of the  
AD8197 can be set to 12 dB without degrading the signal  
integrity, even for short input cables. At the 12 dB setting, the  
AD8197 can equalize more than 20 meters of 24 AWG cable at  
2.25 Gbps.  
The AD8197 switching logic has three modes: quad mode (a  
quad 4:1 switch), dual mode (a dual 8:1 switch) and single  
mode (one 16:1 switch).  
The AD8197 has two control interfaces. Users have the option  
of controlling the part through either the parallel control  
interface or the I2C serial control interface. The AD8197 has  
eight user-programmable I2C slave addresses to allow multiple  
2
RESET  
AD8197s to be controlled by a single I C bus. A  
pin is  
provided to restore the control registers of the AD8197 to  
default values. In all cases, serial programming values override  
any prior parallel programming values and any use of the serial  
control interface disables the parallel control interface until the  
AD8197 is reset.  
OUTPUT CHANNELS  
Each high speed output differential pair is terminated to the  
3.3 V VTTO power supply through two 50 Ω on-chip resistors  
(see Figure 26). This termination is user-selectable; it can be  
turned on or off by programming the TX_PTO bit of the  
transmitter settings register through the serial control interface,  
or by setting the PP_OTO pin of the parallel control interface.  
When using the serial control interface, all three switching  
modes (quad, dual, and single) are accessible and the high speed  
channel switching mode is controlled independently of the  
auxiliary signal switching mode. When using the parallel  
control interface, only the quad switching mode is accessible,  
and the same channel select bus (PP_CH[1:0]) simultaneously  
switches both the high speed channels and the auxiliary signals.  
The output termination resistors of the AD8197 back-terminate  
the output TMDS transmission lines. These back-terminations,  
as recommended in the HDMI 1.3 specification, act to absorb  
reflections from impedance discontinuities on the output traces,  
improving the signal integrity of the output traces and adding  
flexibility to how the output traces can be routed. For example,  
interlayer vias can be used to route the AD8197 TMDS outputs  
on multiple layers of the PCB without severely degrading the  
quality of the output signal.  
INPUT CHANNELS  
Each high speed input differential pair terminates to the 3.3 V  
VTTI power supply through a pair of single-ended 50 Ω on-  
chip resistors, as shown in Figure 25. The input terminations  
can be optionally disconnected for approximately 100 ms  
following a source switch. The user can program which of the  
16 high speed input channels employs this feature by selectively  
programming the associated RX_PT bits in the input  
The AD8197 output has a disable feature that places the outputs  
in a tristate mode. This mode is enabled by programming the  
HS_EN bit of the high speed device modes register through the  
serial control interface or by setting the PP_EN pin of the  
termination pulse register through the serial control interface.  
Additionally, all the input terminations can be disconnected by  
PrA | Page 13 of 32  
 
 
AD8197  
Preliminary Technical Data  
parallel control interface. Larger wire-ORed arrays can be  
constructed using the AD8197 in this mode.  
interfaces. When using the serial control interface, the user  
selects which TMDS link is routed to the output by  
programming the HS_CH bits of the high speed device modes  
register in accordance with the switch mapping listed in Table 8.  
When using the parallel control interface, the user selects which  
TMDS link is routed to the output by setting the PP_CH bus of  
the parallel control interface in accordance with the switch  
mapping listed in Table 26.  
VTTO  
50  
50Ω  
OPx  
ONx  
Dual Switching Mode  
DISABLE  
AVEE  
I
OUT  
In this mode, the AD8197 behaves as a locked dual [8:1] TMDS  
channel switch. The two 8:1 switches share the channel select  
input and, therefore, switch together. The user selects which two  
out of the eight possible input groups are routed to output by  
programming the HS_CH bits of the high speed device modes  
register in accordance with the switch mapping listed in Table 9.  
This mode is only accessible through the serial control interface.  
Figure 26. High Speed Output Simplified Schematic  
The AD8197 requires output termination resistors when the  
high speed outputs are enabled. Termination can be internal  
and/or external. The internal terminations of the AD8197 are  
enabled by programming the TX_PTO bit of the transmitter  
settings register or by setting the PP_OTO pin of the parallel  
control interface. The internal terminations of the AD8197  
default to the setting indicated by PP_OTO upon reset. External  
terminations can be provided either by on-board resistors or by  
the input termination resistors of an HDMI/DVI receiver. If  
both the internal terminations are enabled and external termi-  
nations are present, set the output current level to 20 mA by  
programming the TX_OCL bit of the transmitter settings  
register through the serial control interface or by setting the  
PP_OCL pin of the parallel control interface. The output  
current level defaults to the level indicated by PP_OCL upon  
reset. If only external terminations are provided (if the internal  
terminations are disabled), set the output current level to 10 mA  
by programming the TX_OCL bit of the transmitter settings  
register or by setting the PP_OCL pin of the parallel control  
interface. The high speed outputs must be disabled if there are  
no output termination resistors present in the system.  
Single Switching Mode  
In this mode, the AD8197 behaves as a single 16:1 TMDS  
channel multiplexer; one of the 16 input channels is routed to  
all of the outputs. The user selects which input channel is  
routed to the outputs by programming the HS_CH bits in the  
high speed device modes register in accordance with the switch  
mapping listed in Table 10. This mode is only accessible  
through the serial control interface.  
AUXILIARY SWITCH  
The auxiliary (low speed) lines have no amplification. They are  
routed using a passive switch that is bandwidth compatible with  
standard speed I2C. The schematic equivalent for this passive  
connection is shown in Figure 27.  
R
AUX  
AUX_A0  
½C  
AUX_COM0  
½C  
AUX  
AUX  
The output pre-emphasis can be manually configured to provide  
one of four different levels of high frequency boost. The specific  
boost level is selected by programming the TX_PE bits of the  
transmitter settings register through the serial control interface,  
or by setting the PP_PE bus of the parallel control interface. No  
specific cable length is suggested for a particular pre-emphasis  
setting because cable performance varies widely between  
manufacturers.  
Figure 27. Auxiliary Channel Simplified Schematic,  
AUX_A0 to AUX_COM0 Routing Example  
When turning off the AD8197, care needs to be taken with  
the AMUXVCC supply to ensure that the auxiliary multiplexer  
pins remain in a high impedance state. A scenario that illustrates  
this requirement is one where the auxiliary multiplexer is used  
to switch the display data channel (DDC) bus. In some applica-  
tions, additional devices can be connected to the DDC bus  
(such as an EEPROM with EDID information) upstream of the  
AD8197. Extended display identification data (EDID) is a VESA  
standard-defined data format for conveying display configuration  
information to sources to optimize display use. EDID devices  
may need to be available via the DDC bus, regardless of the  
state of the AD8197 and any downstream circuit. For this  
configuration, the auxiliary inputs of the powered down  
AD8197 need to be in a high impedance state to avoid pulling  
down on the DDC lines and preventing these other devices  
from using the bus.  
HIGH SPEED (TMDS) SWITCHING MODES  
The AD8197 has three high speed switching modes: quad, dual,  
and single. These are selected by programming the HS_SM bits  
of the high speed device modes register through the serial  
control interface.  
Quad Switching Mode  
This is the default mode. In quad mode, the AD8197 behaves  
like a 4:1 HDMI/DVI link multiplexer routing groups of four  
TMDS input channels to the four-channel output. This mode is  
accessible through both the serial and the parallel control  
PrA| Page 14 of 32  
 
 
 
Preliminary Data Sheet  
AD8197  
When the AD8197 is powered from a simple resistor network,  
as shown in Figure 28, it uses the 5 V supply that is required  
from any HDMI/DVI source to guarantee high impedance of  
the auxiliary multiplexer pins. The AMUXVCC supply does not  
draw any static current; therefore, it is recommended that the  
resistor network tap the 5 V supplies as close to the connectors  
as possible to avoid any additional voltage drop.  
Quad Switching Mode  
This is the default mode. In quad mode, the AD8197 behaves  
like a 4:1 auxiliary link multiplexer, routing groups of four  
auxiliary input signals to the four-signal output. The user can  
select which group of inputs is routed to the output by program-  
ming the AUX_CH bits of the auxiliary device modes register  
through the serial control interface in accordance with the  
switch mapping listed in Table 13. Alternately, the user can  
select which group of inputs is routed to the output by setting  
the PP_CH bus of the parallel control interface in accordance  
with the switch mapping listed in Table 27.  
This precaution does not need to be taken if the DDC  
peripheral circuitry is connected to the bus downstream of  
the AD8197.  
Dual Switching Mode  
In this mode, the AD8197 behaves as a locked dual [8:1]  
auxiliary signal switch. The two 8:1 switches share the channel  
select input and, therefore, switch together. The user selects  
which two out of the eight possible input groups are routed to  
the output by programming the AUX_CH bits of the auxiliary  
device modes register in accordance with the switch mapping  
listed in Table 14. This mode is only accessible through the  
serial control interface.  
Figure 28. Suggested AMUXVCC Power Scheme  
Single Switching Mode  
AUXILIARY (LOW SPEED) SWITCHING MODES  
In this mode the AD8197 behaves as a single 16:1 TMDS  
channel multiplexer; a single channel, out of a possible 16, is  
routed to all of the outputs. The user selects which input  
channel is routed to the outputs by programming the AUX_CH  
bits of the auxiliary device modes register in accordance with  
the switch mapping listed in Table 15. This mode is only  
accessible through the serial control interface.  
The AD8197 has three auxiliary switching modes: quad, dual,  
and single. These are selected by programming the AUX_SM  
bits of the auxiliary device modes register through the serial  
control interface. The auxiliary switching mode is independent  
of the high speed switching mode whenever the part is  
controlled through the serial control interface. When the part is  
controlled through the parallel control interface, however, only  
quad mode is accessible and the auxiliary switching mode  
cannot be independently controlled.  
PrA | Page 15 of 32  
 
 
AD8197  
Preliminary Technical Data  
SERIAL CONTROL INTERFACE  
RESET  
4. Wait for the AD8197 to acknowledge the request.  
On initial power-up, or at any point in operation, the AD8197  
register set can be restored to preprogrammed default values by  
5. Send the register address (eight bits) to which data is to be  
written. This transfer should be MSB first.  
RESET  
pulling the  
pin to low in accordance with the specifica-  
RESET  
6. Wait for the AD8197 to acknowledge the request.  
tions in Table 1. During normal operation, however, the  
pin must be pulled up to 3.3 V. Following a reset, the prepro-  
grammed default values of the AD8197 register set correspond  
to the state of the parallel interface configuration registers, as  
listed in Table 24. The AD8197 can be controlled through the  
parallel control interface until the first serial control event  
occurs. As soon as any serial control event occurs, the serial  
programming values, corresponding to the state of the serial  
interface configuration registers (Table 5), override any prior  
parallel programming values, and the parallel control interface  
is disabled until the part is subsequently reset.  
7. Send the data (eight bits) to be written to the register  
whose address was set in Step 5. This transfer should be  
MSB first.  
8. Wait for the AD8197 to acknowledge the request.  
9. Perform one of the following:  
9a. Send a stop condition (while holding the I2C_SCL  
line high, pull the I2C_SDA line high) and release  
control of the bus to end the transaction (shown in  
Figure 29).  
WRITE PROCEDURE  
To write data to the AD8197 register set, an I2C master (such as  
a microcontroller) needs to send the appropriate control signals  
to the AD8197 slave device. The signals are controlled by the  
I2C master, unless otherwise specified. For a diagram of the  
procedure, see Figure 29. The steps for a write procedure are as  
follows:  
9b. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 2 in this procedure to perform  
another write.  
9c. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 2 of the read procedure (in the  
Read Procedure section) to perform a read from  
another address.  
1. Send a start condition (while holding the I2C_SCL line  
high, pull the I2C_SDA line low).  
2. Send the AD8197 part address (seven bits). The upper four  
bits of the AD8197 part address are the static value [1001]  
and the three LSBs are set by Input Pin I2C_ADDR2, Input  
Pin I2C_ADDR1, and Input Pin I2C_ADDR0 (LSB). This  
transfer should be MSB first.  
9d. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 8 of the read procedure (in the  
Read Procedure section) to perform a read from the  
same address set in Step 5.  
3. Send the write indicator bit (0).  
*
I2C_SCL  
R/W  
GENERAL CASE  
I2C_SDA  
FIXED PART  
ADDR  
START  
ADDR  
REGISTER ADDR  
DATA  
STOP  
ACK  
ACK  
ACK  
EXAMPLE  
I2C_SDA  
1
2
3
4
5
6
7
8
9
*THE SWITCHING/UPDATE DELAY BEGINS AT THE FALLING EDGE OF THE  
LAST DATA BIT; FOR EXAMPLE, THE FALLING EDGE JUST BEFORE STEP 8.  
Figure 29. I2C Write Diagram  
PrA| Page 16 of 32  
 
 
 
 
Preliminary Data Sheet  
AD8197  
I2C_SCL  
R/W  
R/W  
GENERAL CASE  
I2C_SDA  
FIXED PART  
ADDR  
FIXED PART  
ADDR  
START  
ADDR  
REGISTER ADDR  
SR  
ADDR  
DATA  
STOP  
ACK  
ACK  
ACK  
ACK  
EXAMPLE  
I2C_SDA  
1
2
3
4
5
6
7
8
9
10 11  
12  
13  
Figure 30. I2C Read Diagram  
13b. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 2 of the write procedure (previous  
Write Procedure section) to perform a write.  
READ PROCEDURE  
To read data from the AD8197 register set, an I2C master (such  
as a microcontroller) needs to send the appropriate control  
signals to the AD8197 slave device. The signals are controlled  
by the I2C master, unless otherwise specified. For a diagram of  
the procedure, see Figure 30. The steps for a read procedure are  
as follows:  
13c. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 2 of this procedure to perform a  
read from another address.  
1. Send a start condition (while holding the I2C_SCL line  
high, pull the I2C_SDA line low).  
13d. Send a repeated start condition (while holding the  
I2C_SCL line high, pull the I2C_SDA line low) and  
continue with Step 8 of this procedure to perform a  
read from the same address.  
2. Send the AD8197 part address (seven bits). The upper four  
bits of the AD8197 part address are the static value [1001]  
and the three LSBs are set by Input Pin I2C_ADDR2, Input  
Pin I2C_ADDR1, and Input Pin I2C_ADDR0 (LSB). This  
transfer should be MSB first.  
SWITCHING/UPDATE DELAY  
There is a delay between when a user writes to the configura-  
tion registers of the AD8197 and when that state change takes  
physical effect. This update delay occurs regardless of whether  
the user programs the AD8197 via the serial or the parallel  
control interface. When using the serial control interface, the  
update delay begins at the falling edge of I2C_SCL for the last  
data bit transferred, as shown in Figure 29. When using the  
parallel control interface, the update delay begins at the  
transition edge of the relevant parallel interface pin. This update  
delay is register specific and the times are specified in Table 1.  
3. Send the write indicator bit (0).  
4. Wait for the AD8197 to acknowledge the request.  
5. Send the register address (eight bits) from which data is to  
be read. This transfer should be MSB first.  
6. Wait for the AD8197 to acknowledge the request.  
7. Send a repeated start condition (Sr) by holding the  
I2C_SCL line high and pulling the I2C_SDA line low.  
8. Resend the AD8197 part address (seven bits) from Step 2.  
The upper four bits of the AD8197 part address are the  
static value [1001] and the three LSBs are set by the Input  
Pin I2C_ADDR2, I2C_ADDR1 and Input Pin I2C_ADDR0  
(LSB). This transfer should be MSB first.  
During a delay window, new values can be written to the  
configuration registers but the AD8197 does not physically  
update until the end of that registers delay window. Writing  
new values during the delay window does not reset the window;  
new values supersede the previously written values. At the end  
of the delay window, the AD8197 physically assumes the state  
indicated by the last set of values written to the configuration  
registers. If the configuration registers are written after the delay  
window ends, the AD8197 immediately updates and a new  
delay window begins.  
9. Send the read indicator bit (1).  
10. Wait for the AD8197 to acknowledge the request.  
11. The AD8197 serially transfers the data (eight bits) held in  
the register indicated by the address set in Step 5. This data  
is sent MSB first.  
12. Acknowledge the data from the AD8197.  
13. Perform one of the following:  
13a. Send a stop condition (while holding the I2C_SCL  
line high, pull the SDA line high) and release control  
of the bus to end the transaction (shown in Figure 30).  
PrA | Page 17 of 32  
 
 
 
AD8197  
Preliminary Technical Data  
PARALLEL CONTROL INTERFACE  
The AD8197 can be controlled through the parallel interface  
using the PP_EN, PP_CH[1:0], PP_EQ, PP_PRE[1:0], PP_OTO,  
and PP_OCL pins. Logic levels for the parallel interface pins  
are set in accordance with the specifications listed in Table 1.  
Setting these pins updates the parallel control interface  
registers, as listed in Table 24. Following a reset, the AD8197  
can be controlled through the parallel control interface until the  
first serial control event occurs. As soon as any serial control  
event occurs, the serial programming values override any prior  
parallel programming values, and the parallel control interface  
is disabled until the part is subsequently reset. The default serial  
programming values correspond to the state of the serial  
interface configuration registers, as listed in Table 5.  
PrA| Page 18 of 32  
 
Preliminary Data Sheet  
AD8197  
SERIAL INTERFACE CONFIGURATION REGISTERS  
The serial interface configuration registers can be read and written using the I2C serial control interface, Pin I2C_SDA, and Pin I2C_SCL.  
The least significant bits of the AD8197 I2C part address are set by tying the Pin I2C_ADDR2, Pin I2C_ADDR1, and Pin I2C_ADDR0 to  
3.3 V (Logic 1) or 0 V (Logic 0). As soon as the serial control interface is used, the parallel control interface is disabled until the AD8197  
is reset as described in the Serial Control Interface section.  
Table 5. Serial (I2C) Interface Register Map  
Name  
Bit 7  
Bit 6  
Bit 5  
Bit 4  
Bit 3  
Bit 2  
Bit 1  
Bit 0  
Addr. Default  
High Speed  
Device  
Modes  
High  
High speed switching  
mode select  
High speed source select  
0x00  
0x40  
speed  
switch  
enable  
HS_EN  
HS_SM[1]  
HS_SM[0]  
HS_CH[3]  
HS_CH[2]  
HS_CH[1]  
HS_CH[0]  
Auxiliary  
Device  
Modes  
Auxiliary  
switch  
enable  
Auxiliary switching  
mode select  
Auxiliary switch source select  
0x01  
0x10  
0x40  
0x01  
AUX_EN  
AUX_SM[1] AUX_SM[0] AUX_CH[3] AUX_CH[2] AUX_CH[1]  
AUX_CH[0]  
Receiver  
Settings  
High speed  
input  
termination  
select  
RX_TO  
Input  
Termination  
Pulse 1  
Source A and Source B : input termination pulse-on-source switch select  
(disconnect termination for a short period of time)  
0x11  
0x12  
0x00  
0x00  
RX_PT[7] RX_PT[6]  
RX_PT[5]  
RX_PT[4]  
RX_PT[3]  
RX_PT[2]  
RX_PT[1]  
RX_PT [0]  
Input  
Termination  
Source C and Source D: input termination pulse-on-source switch select  
(disconnect termination for a short period of time)  
Pulse 2  
RX_PT[15] RX_PT[14]  
RX_PT[13]  
Source A and Source B: input equalization level select  
RX_EQ[5] RX_EQ[4] RX_EQ[3] RX_EQ[2]  
Source C and Source D: input equalization level select  
RX_EQ[15] RX_EQ[14] RX_EQ[13] RX_EQ[12] RX_EQ[11] RX_EQ[10]  
High speed output  
RX_PT[12]  
RX_PT[11]  
RX_PT[10]  
RX_PT[9]  
RX_PT[8]  
RX_EQ[0]  
RX_EQ[8]  
Receive  
Equalizer 1  
0x13  
0x14  
0x20  
0x00  
0x00  
0x03  
RX_EQ[7] RX_EQ[6]  
RX_EQ[1]  
Receive  
Equalizer 2  
RX_EQ[9]  
Transmitter  
Settings  
High speed  
High speed  
output  
current level  
pre-emphasis level select output  
termination  
select  
select  
TX_PE[1]  
TX_PE[0]  
TX_PTO  
TX_OCL  
HS_CH[3:0]: High Speed (TMDS) Switch Source Select Bus  
HIGH SPEED DEVICE MODES REGISTER  
Table 8. Quad Mode, 4× [4:1], High Speed Switch Mapping  
HS_EN: High Speed (TMDS) Channels Enable Bit  
HS_CH[3:0] O[3:0] Description  
Table 6. HS_EN Description  
XX00  
XX01  
XX10  
XX11  
A[3:0]  
B[3:0]  
C[3:0]  
D[3:0]  
High Speed Source A switched to  
output  
High Speed Source B switched to  
output  
High Speed Source C switched to  
output  
High Speed Source D switched to  
output  
HS_EN Description  
0
1
High speed channels off, low power/standby mode  
High speed channels on  
HS_SM[1:0]: High Speed (TMDS) Switching Mode  
Select Bus  
Table 7. HS_SM Description  
HS_SM[1:0]  
Description  
00  
01  
10  
11  
Quad mode, 4× [4:1]  
Dual mode, 2× [8:1]  
Single mode, 1× [16:1]  
Illegal value; previous value of HS_SM[1:0]  
retained  
PrA | Page 19 of 32  
 
 
 
AD8197  
Preliminary Technical Data  
Table 9. Dual Mode, 2× [8:1], High Speed Switch Mapping  
HS_CH[3:0] O[3:2] O[1:0] Description  
AUXILIARY DEVICE MODES REGISTER  
AUX_EN: Auxiliary (Low Speed) Switch Enable Bit  
X000  
X001  
X010  
X011  
X100  
X101  
X110  
X111  
A1  
A3  
B1  
B3  
C1  
C3  
D1  
D3  
A0  
A2  
B0  
B2  
C0  
C2  
D0  
D2  
The A0 and A1 high speed  
channels switched to output  
The A2 and A3 high speed  
channels switched to output  
The B0 and B1 high speed  
channels switched to output  
The B2 and B3 high speed  
channels switched to output  
The C0 and C1 high speed  
channels switched to output  
The C2 and C3 high speed  
channels switched to output  
Table 11. AUX_EN Description  
AUX_EN  
Description  
0
Auxiliary switch off, no low speed input/output  
to low speed common input/output  
connection  
1
Auxiliary switch on  
AUX_SM[1:0]: Auxiliary (Low Speed) Switching Mode  
Select Bus  
Table 12. AUX_SM[1:0] Description  
AUX_SM[1:0] Description  
The D0 and D1 high speed  
channels switched to output  
The D2 and D3 high speed  
channels switched to output  
00  
01  
10  
11  
Quad Mode, 4× [4:1]  
Dual Mode, 2× [8:1]  
Single Mode, 1× [6:1]  
Illegal value; previous value of AUX_SM[1:0]  
retained  
Table 10. Single Mode, 1× [16:1], High Speed Switch  
Mapping  
HS_CH[3:0] O[3:0] Description  
AUX_CH[3:0]: Auxiliary (Low Speed) Switch Source  
Select Bus  
0000  
0001  
0010  
0011  
0100  
0101  
0110  
0111  
1000  
1001  
1010  
1011  
1100  
1101  
1110  
1111  
A0  
A1  
A2  
A3  
B0  
B1  
B2  
B3  
C0  
C1  
C2  
C3  
D0  
D1  
D2  
D3  
High Speed Channel A0 switched to  
output  
High Speed Channel A1 switched to  
output  
High Speed Channel A2 switched to  
output  
High Speed Channel A3 switched to  
output  
High Speed Channel B0 switched to  
output  
High Speed Channel B1 switched to  
output  
High Speed Channel B2 switched to  
output  
High Speed Channel B3 switched to  
output  
High Speed Channel C0 switched to  
output  
High Speed Channel C1 switched to  
output  
High Speed Channel C2 switched to  
output  
High Speed Channel C3 switched to  
output  
High Speed Channel D0 switched to  
output  
High Speed Channel D1 switched to  
output  
High Speed Channel D2 switched to  
output  
High Speed Channel D3 switched to  
output  
Table 13. Quad Mode, 4× [4:1], Auxiliary Switch Mapping  
AUX_CH[3:0] AUX_COM[3:0] Description  
XX00  
XX01  
XX10  
XX11  
AUX_A[3:0]  
AUX_B[3:0]  
AUX_C[3:0]  
AUX_D[3:0]  
Auxiliary Source A switched  
to output  
Auxiliary Source B switched  
to output  
Auxiliary Source C switched  
to output  
Auxiliary Source D switched  
to output  
PrA| Page 20 of 32  
 
 
 
 
Preliminary Data Sheet  
AD8197  
Table 14. Dual Mode, 2× [8:1], Auxiliary Switch Mapping  
Table 15. Single Mode, 1× [16:1], Auxiliary Switch Mapping  
AUX_CH[3:0] AUX_COM[3:2] AUX_COM[1:0] Description  
AUX_CH[3:0] AUX_COM[3:0] Description  
X000  
X001  
X010  
X011  
X100  
X101  
X110  
X111  
AUX_C0  
AUX_C1  
AUX_C2  
AUX_C3  
AUX_D0  
AUX_D1  
AUX_D2  
AUX_D3  
AUX_A0  
AUX_A1  
AUX_A2  
AUX_A3  
AUX_B0  
AUX_B1  
AUX_B2  
AUX_B3  
The A0 and  
C0 auxiliary  
channels  
switched to  
output  
The A1 and  
C1 auxiliary  
channels  
switched to  
output  
The A2 and  
C2 auxiliary  
channels  
switched to  
output  
The A3 and  
C3 auxiliary  
channels  
switched to  
output  
The B0 and  
D0 auxiliary  
channels  
switched to  
output  
The B1 and  
D1 auxiliary  
channels  
switched to  
output  
The B2 and  
D2 auxiliary  
channels  
switched to  
output  
The B3 and  
D3 auxiliary  
channels  
0000  
0001  
0010  
0011  
0100  
0101  
0110  
0111  
1000  
1001  
1010  
1011  
1100  
1101  
1110  
1111  
AUX_A0  
AUX_A1  
AUX_A2  
AUX_A3  
AUX_B0  
AUX_B1  
AUX_B2  
AUX_B3  
AUX_C0  
AUX_C1  
AUX_C2  
AUX_C3  
AUX_D0  
AUX_D1  
AUX_D2  
AUX_D3  
Auxiliary Channel A0  
switched to output  
Auxiliary Channel A1  
switched to output  
Auxiliary Channel A2  
switched to output  
Auxiliary Channel A3  
switched to output  
Auxiliary Channel B0  
switched to output  
Auxiliary Channel B1  
switched to output  
Auxiliary Channel B2  
switched to output  
Auxiliary Channel B3  
switched to output  
Auxiliary Channel C0  
switched to output  
Auxiliary Channel C1  
switched to output  
Auxiliary Channel C2  
switched to output  
Auxiliary Channel C3  
switched to output  
Auxiliary Channel D0  
switched to output  
Auxiliary Channel D1  
switched to output  
Auxiliary Channel D2  
switched to output  
Auxiliary Channel D3  
switched to output  
switched to  
output  
PrA | Page 21 of 32  
 
AD8197  
Preliminary Technical Data  
RECEIVER SETTINGS REGISTER  
RECEIVE EQUALIZER REGISTER 1 AND REGISTER 2  
RX_TO: High Speed (TMDS) Channels Input Termination  
On/Off Select Bit  
RX_EQ[X]: High Speed (TMDS) Input X Equalization Level  
Select Bit  
Table 16. RX_TO Description  
Table 19. RX_EQ[X] Description  
RX_TO  
Description  
RX_EQ[X]  
Description  
0
1
Input termination off  
0
1
Low equalization (6 dB)  
High equalization (12 dB)  
Input termination on (can be pulsed on and off  
according to settings in the input termination  
pulse register)  
Table 20. RX_EQ[X] Mapping  
RX_EQ[X]  
Corresponding Input TMDS Channel  
INPUT TERMINATION PULSE REGISTER 1 AND  
REGISTER 2  
RX_PT[X]: High Speed (TMDS) Input Channel X  
Pulse-On-Source Switch Select Bit  
Bit 0  
Bit 1  
Bit 2  
Bit 3  
Bit 4  
Bit 5  
Bit 6  
Bit 7  
B0  
B1  
B2  
B3  
A0  
A1  
A2  
A3  
C3  
C2  
C1  
C0  
D3  
D2  
D1  
D0  
Table 17. RX_PT[X] Description  
RX_PT[X]  
Description  
0
Input termination for TMDS Channel X always  
connected when source is switched  
Bit 8  
Bit 9  
1
Input termination for TMDS Channel X  
disconnected for 100 ms when source switched  
Bit 10  
Bit 11  
Bit 12  
Bit 13  
Bit 14  
Bit 15  
Table 18. RX_PT[X] Mapping  
RX_PT[X]  
Corresponding Input TMDS Channel  
Bit 0  
Bit 1  
Bit 2  
Bit 3  
Bit 4  
Bit 5  
Bit 6  
Bit 7  
B0  
B1  
B2  
B3  
A0  
A1  
A2  
A3  
C3  
C2  
C1  
C0  
D3  
D2  
D1  
D0  
TRANSMITTER SETTINGS REGISTER  
TX_PE[1:0]: High Speed (TMDS) Output Pre-Emphasis  
Level Select Bus (For All TMDS Channels)  
Table 21. TX_PE[1:0] Description  
TX_PE[1:0]  
Bit 8  
Bit 9  
Description  
00  
01  
10  
11  
No pre-emphasis (0 dB)  
Low pre-emphasis (2 dB)  
Medium pre-emphasis (4 dB)  
High pre-emphasis (6 dB)  
Bit 10  
Bit 11  
Bit 12  
Bit 13  
Bit 14  
Bit 15  
TX_PTO: High Speed (TMDS) Output Termination On/Off  
Select Bit (For All Channels)  
Table 22. TX_PTO Description  
TX_PTO  
Description  
0
1
Output termination off  
Output termination on  
TX_OCL:High Speed (TMDS) Output Current Level Select  
Bit (For All Channels)  
Table 23. TX_OCL Description  
TX_OCL  
Description  
0
1
Output current set to 10 mA  
Output current set to 20 mA  
PrA| Page 22 of 32  
 
Preliminary Data Sheet  
AD8197  
PARALLEL INTERFACE CONFIGURATION REGISTERS  
The parallel interface configuration registers can be directly set using the PP_EN, PP_CH[1:0], PP_EQ, PP_PRE[1:0], PP_OTO, and  
PP_OCL pins. This interface is only accessible after the part is reset and before any registers are accessed using the serial control interface.  
The state of each pin is set by tying it to 3.3 V (Logic 1) or 0 V (Logic 0).  
Table 24. Parallel Interface Register Map  
Name  
Bit 7  
Bit 6  
Bit 5  
Bit 4  
Bit 3  
Bit 2  
Bit 1  
Bit 0  
High Speed  
High speed  
High speed switching  
High speed source select  
Device Modes  
switch enable mode select (quad)  
PP_EN  
0
0
0
0
0
0
PP_CH[1]  
PP_CH[0]  
Auxiliary Device  
Modes  
Auxiliary  
Auxiliary switching  
Auxiliary switch source select  
switch enable mode select (quad)  
1
0
0
PP_CH[1]  
PP_CH[0]  
Receiver  
Settings  
Input term. on/off  
select (termination  
always on)  
1
Input  
Source A and Source B input termination pulse-on-source switch select (termination always on)  
Termination  
Pulse 1  
0
0
0
0
0
0
0
0
0
0
Input  
Termination  
Pulse 2  
Source C and Source D input termination pulse-on-source switch select (termination always on)  
0
0
0
0
0
0
Receive  
Equalizer 1  
Source A and Source B input equalization level select  
PP_EQ PP_EQ PP_EQ PP_EQ  
Source C and Source D input equalization level select  
PP_EQ PP_EQ PP_EQ PP_EQ  
Output pre-emphasis Output  
level select termination  
on/off select  
PP_PE[1] PP_PE[0] PP_OTO  
PP_EQ PP_EQ  
PP_EQ PP_EQ  
PP_EQ  
PP_EQ  
PP_EQ  
PP_EQ  
Receive  
Equalizer 2  
Transmitter  
Settings  
Output current level  
select  
PP_OCL  
HIGH SPEED DEVICE MODES REGISTER  
AUXILIARY DEVICE MODES REGISTER  
The high speed (TMDS) switching mode is fixed to quad mode  
when using the parallel interface.  
The auxiliary (low speed) switch is always enabled and the  
auxiliary switching mode is fixed to quad mode when using the  
parallel interface.  
PP_EN: High Speed (TMDS) Channels Enable Bit  
PP_CH[1:0]: Auxiliary Switch Source Select Bus  
Table 25. PP_EN Description  
Table 27. Quad Auxiliary Switch Mode Mapping  
PP_EN Description  
PP_CH[1:0] AUX_COM[3:0] Description  
0
1
High speed channels off, low power/standby mode  
High speed channels on  
00  
01  
10  
11  
AUX_A[3:0]  
AUX_B[3:0]0  
AUX_C[3:0]  
AUX_D[3:0]  
Auxiliary Source A switched to  
output  
Auxiliary Source B switched to  
output  
Auxiliary Source C switched to  
output  
Auxiliary Source D switched to  
output  
PP_CH[1:0]: High Speed (TMDS) Switch Source Select Bus  
Table 26. Quad High speed Switch Mode Mapping  
PP_CH[1:0] O[3:0] Description  
00  
01  
10  
11  
A[3:0]  
B[3:0]  
C[3:0]  
D[3:0]  
High Speed Source A switched to  
output  
High Speed Source B switched to  
output  
High Speed Source C switched to  
output  
High Speed Source D switched to  
output  
PrA | Page 23 of 32  
 
 
 
 
AD8197  
Preliminary Technical Data  
TRANSMITTER SETTINGS REGISTER  
RECEIVER SETTINGS REGISTER  
PP_PE[1:0]: High Speed (TMDS) Output Pre-Emphasis  
Level Select Bus (For All TMDS Channels)  
High speed (TMDS) channels input termination is fixed to on  
when using the parallel interface.  
Table 29. PP_PE[1:0] Description  
INPUT TERMINATION PULSE REGISTER 1 AND  
REGISTER 2  
PP_PE[1:0]  
Description  
00  
01  
10  
11  
No pre-emphasis (0 dB)  
Low pre-emphasis (2 dB)  
Medium pre-emphasis (4 dB)  
High pre-emphasis (6 dB)  
High speed input (TMDS) channels pulse-on-source switching  
fixed to off when using the parallel interface.  
RECEIVE EQUALIZER REGISTER 1 AND REGISTER 2  
PP_EQ: High Speed (TMDS) Inputs Equalization Level  
Select Bit (For All TMDS Input Channels)  
PP_OTO: High Speed (TMDS) Output Termination On/Off  
Select Bit (For All TMDS Channels)  
The input equalization cannot be set individually (per channel)  
when using the parallel interface; one equalization setting  
affects all input channels.  
Table 30. PP_OTO Description  
PP_OTO  
Description  
0
1
Output termination off  
Output termination on  
Table 28. PP_EQ Description  
PP_EQ  
Description  
PP_OCL: High Speed (TMDS) Output Current Level Select  
Bit (For All TMDS Channels)  
0
1
Low equalization (6 dB)  
High equalization (12 dB)  
Table 31. TX_OCL Description  
PP_OCL  
Description  
0
1
Output current set to 10 mA  
Output current set to 20 mA  
PrA| Page 24 of 32  
 
Preliminary Data Sheet  
AD8197  
APPLICATION INFORMATION  
Figure 31. Layout of the TMDS Traces on the AD8197 Evaluation Board (Only Top Signal Routing Layer is Shown)  
and output pre-emphasis of the AD8197 is that the AD8197 can  
compensate for the signal degradation of both input and output  
cables; it acts to reopen a closed input data eye and transmit a  
full-swing HDMI signal to an end receiver. More information  
on the specific performance metrics of the AD8197 can be  
found in the Typical Performance Characteristics section.  
The AD8197 is an HDMI/DVI switch featuring equalized  
TMDS inputs and pre-emphasized TMDS outputs. It is in-  
tended for use as a 4:1 switch in systems with long cable runs  
on both the input and/or the output, and is fully HDMI 1.3  
receive-compliant.  
PINOUT  
The AD8197 also provides a distinct advantage in receive-type  
applications because it is a fully buffered HDMI/DVI switch.  
Although inverting the output pin order of the AD8197 on the  
PCB requires a designer to place vias in the high speed signal  
path, the AD8197 fully buffers and electrically decouples the  
outputs from the inputs. Consequently, the effects of the vias  
placed on the output signal lines are not seen at the input of the  
AD8197. The programmable output terminations also improve  
signal quality at the output of the AD8197. Therefore, the PCB  
designer has significantly improved flexibility in the placement  
and routing of the output signal path with the AD8197 over  
other solutions.  
The AD8197 is designed for an HDMI/DVI receiver pinout  
at its input and a transmitter pinout at its output. This makes  
the AD8197 ideal for use in AVR-type applications where the  
designer routes both the inputs and the outputs directly to  
HDMI/DVI connectors. This type of layout is used on the  
AD8197 evaluation board, as shown in Figure 31. When the  
AD8197 is used in receiver type applications, it is necessary to  
change the ordering of the output pins on the PCB to match up  
with the on-board receiver.  
One advantage of the AD8197 in an AVR-type application is  
that all of the high speed signals can be routed on one side (the  
topside) of the board, as shown in Figure 31. In addition to  
12 dB of input equalization, the AD8197 provides up to 6 dB of  
output pre-emphasis that boosts the output TMDS signals and  
allows the AD8197 to precompensate when driving long PCB  
traces or output cables. The net effect of the input equalization  
CABLE LENGTHS AND EQUALIZATION  
The AD8197 offers two levels of programmable equalization  
for the high speed inputs: 6 dB and 12 dB. The equalizer of  
the AD8197 supports video data rates of up to 2.25 Gbps. It can  
equalize more than 20 meters of 24 AWG HDMI cable at 2.25  
PrA | Page 25 of 32  
 
 
AD8197  
Preliminary Technical Data  
Gbps, which corresponds to the video format, 1080p with deep  
color.  
speed, and transferred over a single-ended transmission line  
that does not need to have controlled impedance. The primary  
concern with laying out the auxiliary lines is ensuring that they  
conform to the I2C bus standard and do not have excessive  
capacitive loading.  
The length of cable that can be used in a typical HDMI/DVI  
application depends on a large number of factors, including:  
Cable quality: the quality of the cable in terms of conductor  
wire gauge and shielding. Thicker conductors have lower  
signal degradation per unit length.  
TMDS Signals  
In the HDMI/DVI standard, four differential pairs carry the  
TMDS signals. In DVI, three of these pairs are dedicated to  
carrying RGB video and sync data. For HDMI, audio data is  
interleaved with the video data; the DVI standard does not  
incorporate audio information. The fourth high speed differ-  
ential pair is used for the AV data-word clock, and runs at  
one-tenth the speed of the TMDS data channels.  
Data rate: the data rate being sent over the cable. The signal  
degradation of HDMI cables increases with data rate.  
Edge rates: the edge rates of the source input. Slower input  
edges result in more significant data eye closure at the end  
of a cable.  
Receiver sensitivity: the sensitivity of the terminating  
receiver.  
The four high speed channels of the AD8197 are identical.  
No concession was made to lower the bandwidth of the fourth  
channel for the pixel clock, so any channel can be used for any  
TMDS signal. The user chooses which signal is routed over  
which channel. Additionally, the TMDS channels are symmetrical;  
therefore, the p and n of a given differential pair are inter-  
changeable, provided the inversion is consistent across all inputs  
and outputs of the AD8197. However, the routing between  
inputs and outputs through the AD8197 is fixed. For example,  
in quad mode, Output Channel 0 always switches between  
Input A0, Input B0, Input C0, Input D0, and so forth.  
As such, specific cable types and lengths are not recommended  
for use with a particular equalizer setting. In nearly all applica-  
tions, the AD8197 equalization level can be set to high, or 12 dB,  
for all input cable configurations at all data rates, without  
degrading the signal integrity.  
PCB LAYOUT GUIDELINES  
The AD8197 is used to switch two distinctly different types of  
signals, both of which are required for HDMI and DVI video.  
These signal groups require different treatment when laying out  
a PC board.  
The AD8197 buffers the TMDS signals and the input traces can  
be considered electrically independent of the output traces. In  
most applications, the quality of the signal on the input TMDS  
traces are more sensitive to the PCB layout. Regardless of the  
data being carried on a specific TMDS channel, or whether the  
TMDS line is at the input or the output of the AD8197, all four  
high speed signals should be routed on a PCB in accordance  
with the same RF layout guidelines.  
The first group of signals carries the audiovisual (AV) data.  
HDMI/DVI video signals are differential, unidirectional, and  
high speed (up to 2.25 Gbps). The channels that carry the video  
data must be controlled impedance, terminated at the receiver,  
and capable of operating at the maximum specified system data  
rate. It is especially important to note that the differential traces  
that carry the TMDS signals should be designed with a  
controlled differential impedance of 100 Ω. The AD8197  
provides single-ended, 50 Ω terminations on-chip for both its  
inputs and outputs, and both the input and output terminations  
can be enabled or disabled through the serial interface.  
Transmitter termination is not required by the HDMI 1.3 standard  
but its inclusion improves the overall system signal integrity.  
Layout for the TMDS Signals  
The TMDS differential pairs can either be microstrip traces,  
routed on the outer layer of a board, or stripline traces, routed  
on an internal layer of the board. If microstrip traces are used,  
there should be a continuous reference plane on the PCB layer  
directly below the traces. If stripline traces are used, they must  
be sandwiched between two continuous reference planes in the  
PCB stack-up. Additionally, the p and n of each differential pair  
must have a controlled differential impedance of 100 Ω. The  
characteristic impedance of a differential pair is a function of  
several variables including the trace width, the distance separating  
the two traces, the spacing between the traces and the reference  
plane, and the dielectric constant of the PC board binder material.  
Interlayer vias introduce impedance discontinuities that can  
cause reflections and jitter on the signal path, therefore, it is  
preferable to route the TMDS lines exclusively on one layer of the  
board, particularly for the input traces. In some applications, such  
as using multiple AD8197s to construct large input arrays, the use  
of interlayer vias becomes unavoidable. In these situations, the  
input termination feature of the AD8197 improves system signal  
The audiovisual (AV) data carried on these high speed channels  
are encoded by a technique called transmission minimized  
differential signaling (TMDS) and in the case of HDMI, is also  
encrypted according to the high bandwidth digital copy  
protection (HDCP) standard.  
The second group of signals consists of low speed auxiliary  
control signals used for communication between a source and a  
sink. Depending upon the application, these signals can include  
the DDC bus (this is an I2C bus used to send EDID information  
and HDCP encryption keys between the source and the sink),  
the consumer electronics control (CEC) line, and the hot plug  
detect (HPD) line. These auxiliary signals are bidirectional, low  
PrA| Page 26 of 32  
 
Preliminary Data Sheet  
AD8197  
integrity by absorbing reflections. Take care to use vias minimally  
and to place vias symmetrically for each side of a given differential  
pair. Furthermore, to prevent unwanted signal coupling and  
interference, route the TMDS signals away from other signals  
and noise sources on the PCB.  
is coupled to the other. When the two traces of a differential  
pair are close and strongly coupled, they should have a width  
that produces a 100 Ω differential impedance. When the traces  
split apart, to go into a connector, for example, and are no  
longer so strongly coupled, the width of the traces should be  
increased to yield a differential impedance of 100 Ω in the new  
configuration.  
Both traces of a given differential pair must be equal in length  
to minimize intrapair skew. Maintaining the physical symmetry  
of a differential pair is integral to ensuring its signal integrity;  
excessive intrapair skew can introduce jitter through duty cycle  
distortion (DCD). The p and n of a given differential pair should  
always be routed together to establish the required 100 Ω differ-  
ential impedance. Enough space should be left between the  
differential pairs of a given group so that the n of one pair does  
not couple to the p of another pair. For example, one technique is  
to make the interpair distance 4 to 10 times wider than the  
intrapair spacing.  
Ground Current Return  
In some applications, it can be necessary to invert the output  
pin order of the AD8197. This requires a designer to route the  
TMDS traces on multiple layers of the PCB. When routing  
differential pairs on multiple layers, it is necessary to also re-  
route the corresponding reference plane in order to provide one  
continuous ground current return path for the differential  
signals. An example of this is illustrated in Figure 32.  
Any group of four TMDS channels (Input A, Input B, Input C,  
Input D, or the output) should have closely matched trace  
lengths to minimize interpair skew. Severe interpair skew can  
cause the data on the four different channels of a group to arrive  
out of alignment with one another. A good practice is to match  
the trace lengths for a given group of four channels to within  
0.05 inches on FR4 material.  
Minimizing intra- and interpair skew becomes increasingly  
important as data rates increase. Any introduced error will  
constitute a correspondingly larger fraction of a bit period at  
higher data rates.  
While the AD8197 features input equalization and output pre-  
emphasis, the length of the TMDS traces should be minimized  
to reduce overall signal degradation. Commonly used PC board  
material, such as FR4, is lossy at high frequencies; therefore,  
long traces on the circuit board increase signal attenuation  
resulting in decreased signal swing and increased jitter through  
intersymbol interference (ISI).  
Figure 32. Example Routing of Reference Plane  
TMDS Terminations  
The AD8197 provides internal, 50 Ω single-ended terminations  
for all of its high speed inputs and outputs. It is not necessary to  
include external termination resistors for the TMDS differential  
pairs on the PCB.  
Controlling the Characteristic Impedance of a TMDS  
Differential Pair  
The characteristic impedance of a differential pair depends on  
a number of variables including the trace width, the distance  
between the two traces, the height of the dielectric material  
between the trace and the reference plane below it, and the  
dielectric constant of the PCB binder material. To a lesser  
extent, the characteristic impedance also depends upon the  
trace thickness and the presence of solder mask. There are  
many combinations that can produce the correct characteristic  
impedance. It is generally required to work with the PC board  
fabricator to obtain a set of parameters to produce the desired  
results.  
The output termination resistors of the AD8197 back-terminate  
the output TMDS transmission lines. These back-terminations  
act to absorb reflections from impedance discontinuities on the  
output traces, improving the signal integrity of the output traces  
and adding flexibility to how the output traces can be routed.  
For example, interlayer vias can be used to route the AD8197  
TMDS outputs on multiple layers of the PCB without severely  
degrading the quality of the output signal.  
Auxiliary Control Signals  
There are four single-ended control signals associated with each  
source or sink in an HDMI/DVI application. These are hot plug  
detect (HPD), consumer electronics control (CEC), and two  
display data channel (DDC) lines. The two signals on the DDC  
bus are SDA and SCL (serial data and serial clock, respectively).  
One consideration is how to guarantee a differential pair with  
a differential impedance of 100 Ω over the entire length of the  
trace. One technique to accomplish this is to change the width  
of the traces in a differential pair based on how closely one trace  
PrA | Page 27 of 32  
 
AD8197  
Preliminary Technical Data  
3W  
W
3W  
These four signals can be switched through the auxiliary bus of  
the AD8197 and do not need to be routed with the same strict  
considerations as the high speed TMDS signals.  
SILKSCREEN  
In general, it is sufficient to route each auxiliary signal as a  
single-ended trace. These signals are not sensitive to impedance  
discontinuities, do not require a reference plane, and can be  
routed on multiple layers of the PCB. However, it is best to  
follow strict layout practices whenever possible to prevent the  
PCB design from affecting the overall application. The specific  
routing of the HPD, CEC, and DDC lines depends upon the  
application in which the AD8197 is being used.  
LAYER 1: SIGNAL (MICROSTRIP)  
PCB DIELECTRIC  
LAYER 2: GND (REFERENCE PLANE)  
PCB DIELECTRIC  
LAYER 3: PWR (REFERENCE PLANE)  
PCB DIELECTRIC  
LAYER 4: SIGNAL (MICROSTRIP)  
SILKSCREEN  
For example, the maximum speed of signals present on the  
auxiliary lines is 100 kHz I2C data on the DDC lines; therefore,  
any layout that enables 100 kHz I2C to be passed over the DDC  
bus should suffice. The HDMI 1.3 specification, however, places  
a strict 50 pF limit on the amount of capacitance that can be  
measured on either SDA or SCL at the HDMI input connector.  
This 50 pF limit includes the HDMI connector, the PCB, and  
whatever capacitance is seen at the input of the AD8197, or an  
equivalent receiver. There is a similar limit of 100 pF of input  
capacitance for the CEC line.  
REFERENCE LAYER  
RELIEVED UNDERNEATH  
MICROSTRIP  
Figure 33. Example Board Stackup  
HPD is a dc signal presented by a sink to a source to indicate  
that the source EDID is available for reading. The placement  
of this signal is not critical, but it should be routed as directly  
as possible.  
When the AD8197 is powered up, one set of the auxiliary in-  
puts is passively routed to the outputs. In this state, the AD8197  
looks like a 100 Ω resistor between the selected auxiliary inputs  
and the corresponding outputs as illustrated in Figure 27. The  
AD8197 does not buffer the auxiliary signals, therefore, the  
input traces, output traces, and the connection through the  
AD8197 all must be considered when designing a PCB to meet  
HDMI/DVI specifications. The unselected auxiliary inputs of the  
AD8197 are placed into a high impedance mode when the device  
is powered up. To ensure that all of the auxiliary inputs of the  
AD8197 are in a high impedance mode when the device is powered  
off, it is necessary to power the AMUXVCC supply as illustrated  
in Figure 28.  
The parasitic capacitance of traces on a PCB increases with  
trace length. To help ensure that a design satisfies the HDMI  
specification, the length of the CEC and DDC lines on the PCB  
should be made as short as possible. Additionally, if there is a  
reference plane in the layer adjacent to the auxiliary traces in  
the PCB stack-up, relieving or clearing out this reference plane  
immediately under the auxiliary traces significantly decreases  
the amount of parasitic trace capacitance. An example of the  
board stackup is shown in Figure 33.  
In contrast to the auxiliary signals, the AD8197 buffers the  
TMDS signals, allowing a PCB designer to layout the TMDS  
inputs independently of the outputs.  
PrA| Page 28 of 32  
 
Preliminary Data Sheet  
AD8197  
RECOMMENDED  
Power Supplies  
The AD8197 has five separate power supplies referenced to  
two separate grounds. The supply/ground pairs are:  
AVCC/AVEE  
VTTI/AVEE  
VTTO/AVEE  
EXTRA ADDED INDUCTANCE  
DVCC/DVEE  
NOT RECOMMENDED  
AMUXVCC/DVEE  
Figure 34. Recommended Pad Outline for Bypass Capacitors  
The AVCC/AVEE (3.3 V) and DVCC/DVEE (3.3 V) supplies  
power the core of the AD8197. The VTTI/AVEE supply (3.3 V)  
powers the input termination (see Figure 25). Similarly, the  
VTTO/AVEE supply (3.3 V) powers the output termination  
(see Figure 26). The AMUXVCC/DVEE supply (3.3 V to 5 V)  
powers the auxiliary multiplexer core and determines the  
maximum allowed voltage on the auxiliary lines. For example,  
if the DDC bus is using 5 V I2C, then AMUXVCC should be  
connected to +5 V relative to DVEE.  
In applications where the AD8197 is powered by a single 3.3 V  
supply, it is recommended to use two reference supply planes  
and bypass the 3.3 V reference plane to the ground reference  
plane with one 220 pF, one 1000 pF, two 0.01 μF, and one 4.7 μF  
capacitors. The capacitors should via down directly to the  
supply planes and be placed within a few centimeters of the  
AD8197. The AMUXVCC supply does not require additional  
bypassing. This bypassing scheme is illustrated in Figure 35.  
In a typical application, all pins labeled AVEE or DVEE should  
be connected directly to ground. All pins labeled AVCC,  
DVCC, VTTI, or VTTO should be connected to 3.3 V, and  
Pin AMUXVCC tied to 5 V. The supplies can also be powered  
individually, but care must be taken to ensure that each stage of  
the AD8197 is powered correctly.  
Power Supply Bypassing  
The AD8197 requires minimal supply bypassing. When  
powering the supplies individually, place a 0.01 μF capacitor  
between each 3.3 V supply pin (AVCC, DVCC, VTTI, and  
VTTO) and ground to filter out supply noise. Generally, bypass  
capacitors should be placed near the power pins and should  
connect directly to the relevant supplies (without long inter-  
vening traces). For example, to improve the parasitic inductance  
of the power supply decoupling capacitors, minimize the trace  
length between capacitor landing pads and the vias as shown in  
Figure 34.  
Figure 35. Example Placement of Power Supply Decoupling Capacitors  
Around the AD8197  
PrA | Page 29 of 32  
 
 
AD8197  
OUTLINE DIMENSIONS  
16.20  
16.00 SQ  
15.80  
1.60 MAX  
0.75  
0.60  
0.45  
100  
1
76  
75  
PIN 1  
14.20  
14.00 SQ  
13.80  
TOP VIEW  
(PINS DOWN)  
1.45  
1.40  
1.35  
0.20  
0.09  
7°  
3.5°  
0°  
0.08  
COPLANARITY  
25  
51  
50  
0.15  
0.05  
26  
SEATING  
PLANE  
0.27  
0.22  
0.17  
VIEW A  
0.50  
BSC  
LEAD PITCH  
VIEW A  
ROTATED 90° CCW  
COMPLIANT TO JEDEC STANDARDS MS-026-BED  
Figure 36. 100-Lead Low Profile Quad Flat Package [LQFP]  
(ST-100)  
Dimensions shown in millimeters  
ORDERING GUIDE  
Model  
Temperature Range  
Package Description  
Package Option  
ST-100  
ST-100  
Ordering Quantity  
AD8197ASTZ1  
AD8197ASTZ-RL1  
AD8197-EVAL  
−40°C to +85°C  
−40°C to +85°C  
100-Lead Low Profile Quad Flat Package [LQFP]  
100-Lead Low Profile Quad Flat Package [LQFP], Reel  
Evaluation Kit  
1,000  
1 Z = Pb-free part.  
Rev. J | Page 30 of 32  
 
 
Preliminary Data Sheet  
NOTES  
AD8197  
PrA | Page 31 of 32  
AD8197  
NOTES  
Preliminary Technical Data  
©2006 Analog Devices, Inc. All rights reserved. Trademarks and  
registered trademarks are the property of their respective owners.  
PR06471-0-12/06(PrA)  
PrA| Page 32 of 32  
 
 
 
 

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