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19-3669; Rev 0; 4/05
Complete VGA Interface with EMI Suppression
General Description
The MAX9511 is a complete solution to interface a video graphics controller to a VGA port and/or docking station with optimal video performance and minimal electromagnetic interference (EMI) emission. The MAX9511 has output drivers with variable EMI suppression for graphics video and sync (RGBHV) signals. The MAX9511 includes external load-detection circuitry. The MAX9511 suppresses EMI emissions by limiting the slew rate (SR) rather than limiting bandwidth with fixed L-C filters. The SR controls the large-signal bandwidth without affecting the small-signal bandwidth, resulting in sharper video images, while reducing EMI. The SR of the MAX9511 provides tighter control than traditional passive L-C components, and allows the SR to track the resolution by varying an external resistor (RRX) rather than being fixed to a sub-optimal value. The load-detection circuitry of the MAX9511 automatically detects and transmits a change in load status to the input stages when an external load (monitor, docking station, or projector) is connected. The MAX9511 is compatible with the load-detection circuitry on the digital-to-analog (DAC) outputs of most video graphics controllers. The output drivers provide 6dB of gain to compensate for the 75 back-termination resistors, which reduce transmission line reflections. The RGBHV channels can be placed into shutdown to reduce power when no external load is connected. The MAX9511 operates from 3V and 5V supplies. The DDC circuitry performs bidirectional level translation from 3V to 5V logic levels. The MAX9511 is offered in a 24-pin QSOP package and is specified over the commercial 0C to +70C temperature range.
Features
o RGB Drivers with Adjustable Slew Rate for EMI Control o H Sync and V Sync Drivers with Level Translation o Bidirectional Level Translators for DDC Support o Simultaneously Drives External Monitor/Projector and Docking Station without Analog RGB Switches--No Stub Reflections o Eliminates Up to 34 External Components o Small 24-Pin QSOP Package
MAX9511
Ordering Information
PART MAX9511CEG TEMP RANGE 0C to +70C PINPACKAGE 24 QSOP PKG CODE E24-2
Pin Configuration
TOP VIEW
VCC 1 GREEN_IN 2 24 AGND 23 GREEN_OUT 22 AGND 21 RED_OUT
Applications
Notebook PCs (Laptops) Docking Stations Graphics Cards for Notebooks and Personal Computers Personal Computer Motherboards with On-Board Video Graphics Controllers Workstations
AGND 3 RED_IN 4 BLUE_IN 5 RX 6 SHDN 7 DDC_DATA_IN 8 DDC_CLK_IN 9 H_SYNC_IN 10 V_SYNC_IN 11 VDD2 12
MAX9511
20 AGND 19 BLUE_OUT 18 DGND 17 DDC_DATA_OUT 16 DDC_CLK_OUT 15 H_SYNC_OUT 14 V_SYNC_OUT 13 VDD1
QSOP
________________________________________________________________ Maxim Integrated Products
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Complete VGA Interface with EMI Suppression MAX9511
ABSOLUTE MAXIMUM RATINGS
VCC to AGND............................................................-0.3V to +6V VDD1, VDD2 to DGND ...............................................-0.3V to +6V DGND to AGND.....................................................-0.1V to +0.1V RED_IN, GREEN_IN, BLUE_IN to AGND.....-0.3V to (VCC + 0.3V) RED_OUT, GREEN_OUT, BLUE_OUT to AGND ................................................-0.3V to (VCC + 0.3V) RX to AGND................................................-0.3V to (VCC + 0.3V) H_SYNC_IN, V_SYNC_IN, SHDN to DGND ..............................................-0.3V to (VDD2 + 0.3V) H_SYNC_OUT, V_SYNC_OUT to DGND ..............................................-0.3V to (VDD1 + 0.3V) DDC_DATA_IN to DGND..............(DDC_DATA_OUT - 0.3V) to (VDD2 + 0.3V) DDC_DATA_OUT to DGND .................(DDC_DATA_IN - 0.1V) to (VDD1 + 0.3V) DDC_CLK_IN to DGND ................(DDC_CLK_OUT - 0.3V) to (VDD2 + 0.3V) DDC_CLK_OUT to DGND....................(DDC_CLK_IN - 0.1V) to (VDD1 + 0.3V) DDC_DATA_OUT to DDC_DATA_IN ........................-0.1V to +6V DDC_CLK_OUT to DDC_CLK_IN.............................-0.1V to +6V Continuous Power Dissipation (TA = +70C) 24-Pin QSOP (derate 9.5mW/C above +70C)..........762mW Operating Temperature Range...............................0C to +70C Storage Temperature Range .............................-65C to +150C 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 = 5V, VDD1 = 5V, VDD2 = SHDN = 3V, RL = 150 to AGND, DGND = AGND, RRX = 7k to AGND, TA = 0C to +70C. Typical values are at TA = +25C.)
PARAMETER Supply Voltage Range SYMBOL VCC VDD1 VDD2 ICC Quiescent Supply Current IDD1 IDD2 VIDEO Input Voltage Range Output Black Level Voltage Voltage Gain Gain Matching Input Resistance Output Short-Circuit Current (To AGND) Load-Detection Voltage Output Load Detection Power-Supply Rejection Large-Signal Bandwidth VIN AV AV RIN IOUT VX_IN RL_OUT PSRR (Note 1) VIN = 0.4V 4.5V VCC 5.5V, VIN = 0.5V VOUT = 1.6VP-P, RRX = 7k 200 40 48 370 Inferred from voltage gain 0 VIN 0.9V, RL = 75 0 VIN 0.9V, RL = 75 0 VIN 1V, with load 0.4V VIN 0.7V, no load 0.02 -80 0 100 +1.9 0.7 190 +2 1 60 -72 40 0.315 -65 0.9 290 +2.1 2 V mV V/V % M mA V dB MHz VOUT,BLACK RED_IN = GREEN_IN = BLUE_IN = AGND CONDITIONS Inferred from PSRR Inferred from logic test Inferred from logic test SHDN = VDD2 SHDN = DGND SHDN = VDD2 SHDN = DGND SHDN = VDD2 SHDN = DGND RRX = 7k RRX = 36k MIN 4.5 4.5 2.3 38 25 0.15 3 0.027 220 26 TYP MAX 5.5 5.5 3.6 50 35 0.25 6 0.08 500 40 A mA V UNITS
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Complete VGA Interface with EMI Suppression
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VDD1 = 5V, VDD2 = SHDN = 3V, RL = 150 to AGND, DGND = AGND, RRX = 7k to AGND, TA = 0C to +70C. Typical values are at TA = +25C.)
PARAMETER Slew Rate (Notes 2, 3) Settling Time Undershoot/Overshoot Linearity Error Peak Signal-to-Noise Ratio Channel-to-Channel Skew Power-Supply Rejection Ratio Crosstalk Input Termination Switch Delay LOGIC Input Low Level Input High Level VIL VIH H_SYNC_IN, V_SYNC_IN and SHDN H_SYNC_IN, V_SYNC_IN and SHDN IOL = 4mA H_SYNC_OUT, VH_SYNC_IN = DGND 0.7 x VDD2 0.55 0.3 x VDD2 V V tSWD SYMBOL SR tS tOS, tUS LE SNR t PSRR VIN = 700mVP-P (Notes 6, 7) f = 100kHz to 100MHz, VIN = 700mVP-P R to G to B (Note 3) f = 100kHz All hostile, f = 10MHz CONDITIONS RRX = 36k, TA = +25C RRX = 7k, TA = +25C (Notes 4, 5) MIN 250 900 TYP 330 1100 0 1 0.036 50 500 49 55 70 1100 MAX 450 1300 UNITS V/s ns % % dB ps dB dB ns
MAX9511
Output Low Level
VOL
V_SYNC_OUT, VV_SYNC_IN = DGND DDC_DATA_IN, VDDC_DATA_OUT = IOL = 50A DGND DDC_CLK_IN, VDDC_CLK_OUT = DGND IOL = 3mA DDC_DATA_OUT, VDDC_DATA_IN = DGND DDC_CLK_OUT, VDDC_CLK_IN = DGND H_SYNC_OUT, VH_SYNC_IN = VDD2 V_SYNC_OUT, VV_SYNC_IN = VDD2 DDC_DATA_IN, VDDC_DATA_OUT = VDD1 DDC_CLK_IN, VDDC_CLK_OUT = VDD1 DDC_DATA_OUT, VDDC_DATA_IN = VDD2 DDC_CLK_OUT, VDDC_CLK_IN = VDD2 VDD1 - 1.5 VDD2 - 0.4 VDD1 - 1.5 35 250 30 DDC_DATA_OUT, DDC_CLK_OUT DDC_DATA_IN, DDC_CLK_IN 2 3.0 55 330 47 3 4.7
0.4
V
0.5
IOH = 4mA IOH = 50A IOH = 50A SYNC Output Resistance SHDN Pulldown Resistance SYNC Input Resistance DDC Pullup Resistance RSO RSD RSI RPO RPI
Output High Level
VOH
V
85 500 65 4 6.5
k k k
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Complete VGA Interface with EMI Suppression MAX9511
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VDD1 = 5V, VDD2 = SHDN = 3V, RL = 150 to AGND, DGND = AGND, RRX = 7k to AGND, TA = 0C to +70C. Typical values are at TA = +25C.)
PARAMETER Rise/Fall Time Propagation Delay Enable Time Disable Time SYMBOL tR/tF tPLH, tPHL All SYNC outputs (Notes 2, 3) DDC only, CL = 47pF SYNC, CSYNC = 47pF, TA = +25C (Notes 3, 8) VIN = 0.7VP-P, SHDN from DGND to VDD2, outputs settle to 1% of final value VIN = 0.7VP-P, SHDN from VDD2 to DGND, outputs settle to 1% of final value CONDITIONS CSYNC = 47pF, TA = +25C CSYNC = 470pF, TA = +25C 50 MIN TYP 7 70 400 12 1200 400 22 ns ns ns 100 ns MAX UNITS
This is the voltage at which the input termination switches; VIN > VX_IN = switch open, VIN < VX_IN = switch closed. Measured between the 10% to 90% points on rising or falling edge. Not production tested. Guaranteed by design. Measured from the END of overshoot/undershoot to 5% of final value. VIN = 700mV with a rise time >1ns. Linearity error is the maximum difference between the actual and measured output of a video ramp. Done in accordance with VESA Test Procedure, Version 1, 6/11/2001. Note 7: Linearity error measured as percentage of full scale. Note 8: Propagation delay is the time difference between the VDD2 / 2 input crossing and the 1.4V output crossing. Note 1: Note 2: Note 3: Note 4: Note 5: Note 6:
Typical Operating Characteristics
(VCC = 5V, VDD1 = 5V, VDD2 = 3V, RL = 150 to AGND, RRX = 7k to AGND, TA = +25C, unless otherwise noted.)
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY
MAX9511 toc01
LARGE-SIGNAL GAIN FLATNESS vs. FREQUENCY
MAX9511 toc02
LARGE-SIGNAL BANDWIDTH vs. FREQUENCY vs. RRX
2 1 0 GAIN (dB) -1 -2 -3 -4 -5 -6 -7 RRX = 20k RRX = 35k RRX = 50k 0.1 1 10 FREQUENCY (MHz) 100 1000 RRX = 5k
MAX9511 toc03
3 2 1 0 GAIN (dB) VOUT = 1.6VP-P TA = TMIN to TMAX
0.5 0.4 0.3 0.2 GAIN (dB) 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
3
-1 -2 -3 -4 -5 -6 -7 0.1 1 10 FREQUENCY (MHz) 100 1000
0.1
1
10 FREQUENCY (MHz)
100
1000
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Complete VGA Interface with EMI Suppression
Typical Operating Characteristics (continued)
(VCC = 5V, VDD1 = 5V, VDD2 = 3V, RL = 150 to AGND, RRX = 7k to AGND, TA = +25C, unless otherwise noted.)
MAX9511
SMALL-SIGNAL BANDWIDTH vs. FREQUENCY vs. RRX
MAX9511 toc04
LARGE-SIGNAL GAIN FLATNESS vs. FREQUENCY vs. RRX
0.4 0.3 0.2 GAIN (dB) 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 RRX = 35k RRX = 50k RRX = 5k RRX = 20k
MAX9511 toc05
3 2 1 0 GAIN (dB) -1 -2 -3 -4 -5 -6 -7 0.1 1 10 100 1000 RRX = 5k RRX = 20k RRX = 35k RRX = 50k
0.5
10,000
0.1
1
10 FREQUENCY (MHz)
100
1000
FREQUENCY (MHz)
ALL-HOSTILE CROSSTALK vs. FREQUENCY
-10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70 -80 -90 -100 0.1 1 10 FREQUENCY (MHz) 100 1000 -120 0.1 TA = +85C TA = 0C, +25C
MAX9511 toc06
OFF-ISOLATION vs. FREQUENCY
MAX9511 toc07
0
0 -20 OFF-ISOLATION (dB) -40 -60 -80 -100
1
10 FREQUENCY (MHz)
100
1000
TRANSIENT RESPONSE
MAX9511 toc08
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX9511 toc09
0 -10 VIN 500mV/div 0V -20 PSRR (dB) -30 -40 -50 -60 -70 TA = 0C TA = +25C TA = +70C
VOUT 1V/div OV 2ns/div
0.01
0.1
1
10
100
1000
FREQUENCY (MHz)
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Complete VGA Interface with EMI Suppression MAX9511
Typical Operating Characteristics (continued)
(VCC = 5V, VDD1 = 5V, VDD2 = 3V, RL = 150 to AGND, RRX = 7k to AGND, TA = +25C, unless otherwise noted.)
SYNC PULSE RESPONSE
MAX9511 toc10
DDC_IN TO DDC_OUT PULSE RESPONSE
MAX9511 toc11
RL = 2.2k INPUT 1V/div 0V CL = 47pF CL = 150pF CL = 220pF CL = 330pF CL = 510pF INPUT 1V/div
RL = 100k CL = 47pF
0V
OUTPUT 1V/div
OUTPUT 2V/div
tR = 250ns tF = 30ns 0V 500ns/div
0V
50s/div
DDC_OUT TO DDC_IN PULSE RESPONSE
MAX9511 toc12
POWER-SUPPLY CURRENT vs. TEMPERATURE (ICC)
48 POWER-SUPPLY CURRENT (mA) 46 44 42 40 38 36 34 32 30 0 25 50 75
MAX9511 toc13
50
RL = 100k CL = 47pF INPUT 2V/div 0V
OUTPUT 1V/div
tR = 280ns tF = 4ns 0V 500ns/div
TEMPERATURE (C)
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Complete VGA Interface with EMI Suppression MAX9511
Typical Operating Characteristics (continued)
(VCC = 5V, VDD1 = 5V, VDD2 = 3V, RL = 150 to AGND, RRX = 7k to AGND, TA = +25C, unless otherwise noted.)
POWER-SUPPLY CURRENT vs. TEMPERATURE (IDD1, IDD2)
MAX9511 toc14
OUTPUT OFFSET vs. TEMPERATURE (VOUT,BLACK)
MAX9511 toc15
INPUT RESISTANCE vs. TEMPERATURE
-62 -64 RESISTANCE () -66 -68 -70 -72 -74 -76 -78 0.4V VIN 0.7V NO LOAD
MAX9511 toc16
4.0 SHDN = VDD2 3.5 POWER-SUPPLY CURRENT (mA) IDD1 3.0 2.5 2.0 1.5 1.0 0.5 0 0 25 50
300 250 OFFSET VOLTAGE (mV) 200 150 100 50 MEAN - 3 x SIGMA MEAN + 3 x SIGMA MEAN
-60
IDD2 0 75 0 25 50 75 TEMPERATURE (C) TEMPERATURE (C)
-80 0 25 50 75 TEMPERATURE (C)
Pin Description
PIN 1 2 3, 20, 22, 24 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 21 23 NAME VCC GREEN_IN AGND RED_IN BLUE_IN RX SHDN DDC_DATA_IN DDC_CLK_IN H_SYNC_IN V_SYNC_IN VDD2 VDD1 V_SYNC_OUT H_SYNC_OUT DDC_CLK_OUT DGND BLUE_OUT RED_OUT GREEN_OUT Analog Power Supply Green Video Input Analog Ground Red Video Input Blue Video Input Slew-Rate Control. Connect an external resistor from RX to AGND. Active-Low Shutdown. For normal operation connect to VDD2. SHDN is internally pulled to DGND. DDC Data Input. Defaults to VDD2 through an internal pullup resistor. DDC Clock Input. Defaults to VDD2 through an internal pullup resistor. Horizontal SYNC Input. Defaults to AGND through an internal pulldown resistor. Vertical SYNC Input. Defaults to AGND through an internal pulldown resistor. SYNC/DDC 3V Supply SYNC/DDC 5V Supply. Supplies 5V to SYNC and DDC output circuitry. Vertical Sync Output Horizontal Sync Output DDC Clock Output. Defaults to VDD1 through an internal pullup resistor. Digital Ground Blue Video Output Red Video Output Green Video Output FUNCTION
DDC_DATA_OUT DDC Data Output. Defaults to VDD1 through an internal pullup resistor.
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Complete VGA Interface with EMI Suppression MAX9511
Block Diagram
VCC
Detailed Description
The MAX9511 solves several difficult problems in interfacing a video graphics controller to a VGA port and/or the docking station connector. First, there is a trade-off between video quality and EMI. The usual method for reducing EMI is to insert a fixed-frequency LC -filter between the video DAC output and the connector. Given the large component variation of the capacitors and inductors, the frequency response is sharply reduced to meet EMI requirements. As a result, video quality suffers making sharp transitions in the video soft. The MAX9511 video drivers have a variable slew rate, which limits electromagnetic emissions and can be adjusted by an external resistor. As a result, the slew rate of the MAX9511 can be varied to reduce electromagnetic emissions at a given resolution, maximizing video quality. Since the slew rate is variable and set by a resistor instead of fixed by capacitors and inductors, video performance and electromagnetic emissions are consistent during production. The MAX9511 also has horizontal and vertical sync output drivers, bidirectional level translators for DDC support, and external load-detection circuits that correctly transfer information about the external load to the video graphics controller.
MAX9511
RISENSE VY
GREEN_IN
GREEN_OUT
-75
VX
RISENSE
VY
RED_IN
RED_OUT
-75
VX
RISENSE
VY
Load Detection
BLUE_IN BLUE_OUT -75 RX
VX
VDD1 SHDN RPI RPI RB RPO VDD2
DDC_DATA_IN
DDC_DATA_OUT
RB DDC_CLK_IN RSO
RPO DDC_CLK_OUT
H_SYNC_IN
H_SYNC_OUT
RSI
V_SYNC_IN
RSO
V_SYNC_OUT
RSI
AGND
DGND
Most notebook computers implement a power-saving load-detection circuit that disables the external monitor output when no monitor is plugged into the rear panel VGA connector as shown in Figure 1. Upon startup or on command, the video controller generates a sequence of detection pulses out of the current DAC shown, that results in an output voltage of above 315mV when an external monitor (RL) is connected, and above 630mV when disconnected. If the monitor is disconnected at the time of the pulse, the comparator inside the notebook trips and disables the video. When the monitor is plugged in, the resulting pulse will not trip the comparator and the video is enabled. If the lowpass filter is simply replaced with an amplifier, the monitor termination RL is isolated from the video controller and the conventional load-detection scheme does not work. For this reason, the MAX9511 includes the load-detection circuit. When RL is connected (i.e., the monitor is plugged in) to the output of the MAX9511, the internal load-detection circuit disconnects the synthesized -75 resistor from the input. The resulting 37.5 resistance at the DAC output indicates to the DAC's internal load-detection circuit that the monitor is plugged in. Removing RL (i.e., disconnecting the monitor) causes the MAX9511's load-detection circuit to connect the synthesized -75
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Complete VGA Interface with EMI Suppression MAX9511
VIDEO CONTROLLER LOWPASS FILTER FOR EMI SUPPRESSION IOUT MONITOR
REF CURRENT DAC
RT 75
RL 75
Figure 1. Conventional Load-Detection Scheme
VIDEO CONTROLLER RISENSE IOUT G=2 OUT RT 37.5
MONITOR
MAX9511
VY VIS RT 75
REF CURRENT DAC
-75
RL 75
VX
Figure 2. Load-Detection Scheme with MAX9511
resistor to the input. This results in an equivalent impedance of 75 at the DAC output, which indicates to the video controller's internal load-detection circuit that the load is disconnected and the video controller shuts down the video output. Figure 2 and Table 1 demonstrate how the MAX9511 load-detection circuit operates in conjunction with the video controller load detection.
6dB, and hence the actual video signal seen by the load is only 120mV higher than the video signal at the input of the MAX9511. Monitors and other display devices AC-couple the input signal so the 120mV level shift should not affect the displayed video image.
Output Video Signal Level Shift
The video signal at the MAX9511 output is shifted upwards by approximately 240mV from the input to keep the output stage of the video driver in a linear region of operation. At the connector, the video signal is attenuated by 6dB, canceling the 6dB gain of the video driver. The 240mV level shift is also attenuated by
Table 1. Function of Load-Detection Scheme
AMPLIFIER OUTPUT Connected to External Load Not Connected to External Load MAX9511 RESISTANCE AT DAC INTERNAL OUTPUT SWITCH Open Closed 37.5 75
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Complete VGA Interface with EMI Suppression MAX9511
Vertical and Horizontal SYNC
The MAX9511 has separate, noninverting, vertical and horizontal sync buffers. Both sync inputs can level-shift an input as low as 2.3V to a 5V output. Both sync drivers have hysteresis at their input to prevent "chatter" in their outputs. The sync output drivers have a 55 (typ) output impedance (RSO) to match the cable impedance used for vertical and horizontal sync in most applications. Both sync inputs are pulled to DGND through a 47k resistor if the controller's SYNC source goes high impedance, or if the inputs are left floating, avoiding ambiguous output conditions. EMI can result from rapid transitions of the sync or the video signals. To reduce the rise and fall times of the sync signal, additional capacitance may be added to the sync outputs. Adding additional capacitance may require "recentering" the display.
SLEW RATE vs. RRX
1400 1200 SLEW RATE (V/s) 1000 800 600 400 200 0 0 10 20 30 40 50 RRX (k)
MAX9511 fig03
1600
Display Data Channel (DDC)
The MAX9511 bidirectional display data channel (DDC) level translator allows for a lower voltage video controller logic to operate with a higher voltage external monitor logic. Power supplied at VDD2 defines the DDC input voltage thresholds while power supplied at VDD1 defines the DDC output thresholds. Two Schottky-clamped npn transistors shift the lower level DDC inputs to higher logic-level outputs. DDC_CLK_OUT and DDC_DATA_OUT are pulled to VDD1 by internal pullup resistors to prevent ambiguous conditions when left floating. At shutdown, DDC inputs can still respond to external commands.
Figure 3. Slew Rate vs. RRX
Shutdown
The MAX9511 features a low-power shutdown mode for battery-powered/portable applications. Shutdown reduces the quiescent current of the video and sync drivers. Connecting SHDN to ground (DGND) disables the outputs and places the MAX9511 into a low-power shutdown mode. SHDN has a 330k (typ) internal pulldown resistor to DGND. Connect SHDN to VDD2 for normal operation.
Applications Information
Customizing Slew Rates for Different Resolutions
When the MAX9511 connects to devices of different resolutions, different slew rates should be used. The slew rate of the MAX9511 is adjustable by varying RRX between 7k and 38k. By selecting a valid RRX value for a resolution, the MAX9511 minimizes the EMI and optimizes the video output quality. Shown are two configurations to adjust slew rates using different RRX values for different video resolutions. Figure 4 shows how to customize slew rates for three resolutions. This circuit provides three predetermined slew rates by paralleling resistors to create three RRX values. The combination is controlled by a digital command from the video controller through a switch. This requires that the sample clock rates used by different resolutions are close. The sync bandwidth-limiting capacitors (CSYNC) are set for the highest resolution.
Slew-Rate Limiting
The MAX9511 outputs are slew-rate limited to reduce EMI. Slew-rate limiting affects the large-signal bandwidth (LSBW) more than the small-signal bandwidth (SSBW), and can be scaled according to the following formula: LSBW(-3dB) = SR 2 x x VOUT
where VOUT is the output signal's peak-to-peak voltage and LSBW(-3dB) is the -3dB bandwidth. The slew rate of the MAX9511 is controlled by a resistor between RX and AGND. The resistor (RRX) can be varied to optimize the EMI suppression to the display resolution while preserving the display quality. The RRX range is approximately 7k for maximum slew rate and 38k for minimum slew rate (see Figure 3). Slew-rate limiting can be approximated by: 7000 SR = 1030 (V / s) RRX
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Complete VGA Interface with EMI Suppression MAX9511
5V 4.7F 0.22F 5V 0.1F POWERMANAGEMENT CIRCUIT 2.3V TO 3.6V 0.1F 1nF REMOTE MONITOR 7 8 13 12 VDD2 1 VCC 17 DOCKING STATION SYNC BANDWIDTH LIMITING CAPACITORS CSYNC = 47pF TO 470pF CSYNC CSYNC
SHDN VDD1 DDC_DATA_IN
DDC_DATA_OUT
9 10 11
DDC_CLK_IN H_SYNC_IN V_SYNC_IN
DDC_CLK_OUT
16
H_SYNC_OUT V_SYNC_OUT
15 14 23
75 75
VIDEO CONTROLLER
MAX9511
GREEN_OUT
4 37.5
RED_IN
RED_OUT
21
75 75
BLUE_OUT 2 GREEN_IN
19
75 75
37.5
5
BLUE_IN RX
6 R1 = 47k
37.5 AGND 3, 20, 22, 24 DGND 18 COM2 NO1
R2 = 47k COM1 IN1 IN2 R3 = 18k NO2
MAX4731
Figure 4. Three Resolution Slew-Rate Control
Figure 4 showcases the setup for three commonly used resolutions: 1600 x 1200, 1280 x 1024, and 1024 x 768. Since the resolution change is relatively slow, the switch does not have to be fast. The impedance of the switch does not need to be low compared to RRX . When using a high-impedance switch, the resistance
from the switch should be included to calculate RRX. The MAX4731 50 SPST analog switch shown in the figure is used with three external resistors to get RRX values of 47k, 23.5k, and 10k for 1600 x 1200, 1280 x 1024, and 1024 x 768 resolutions, respectively.
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Complete VGA Interface with EMI Suppression MAX9511
5V 4.7F 0.22F 5V 0.1F POWERMANAGEMENT CIRCUIT 2.3V TO 3.6V 0.1F 1nF REMOTE MONITOR 7 8 13 12 VDD2 1 VCC 17 DOCKING STATION SYNC BANDWIDTH LIMITING CAPACITORS CSYNC = 47pF TO 470pF CSYNC CSYNC
SHDN VDD1 DDC_DATA_IN
DDC_DATA_OUT
9 10 11
DDC_CLK_IN H_SYNC_IN V_SYNC_IN
DDC_CLK_OUT
16
H_SYNC_OUT V_SYNC_OUT
15 14 23
75 75
VIDEO CONTROLLER
MAX9511
GREEN_OUT
4 37.5
RED_IN
RED_OUT
21
75 75
BLUE_OUT 2 GREEN_IN
19
75 75
37.5
5
BLUE_IN RX
6
7k
H W R1 = 80k
37.5 AGND 3, 20, 22, 24 DGND 18 SDA SCL
MAX5432
L
Figure 5. Slew-Rate Control with a Digital Potentiometer
The circuit in Figure 5 uses a MAX5432 digital potentiometer to provide more flexibility in customizing slew rates. An 80k external trim resistor is placed in parallel
with the 50k MAX5432 to limit the maximum value of RRX to 38k. This setup provides 33 levels of RRX values through the I2C control ports at the MAX5432.
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Complete VGA Interface with EMI Suppression
Power Supplies
The MAX9511 operates with a 4.5V to 5.5V power supply for video (RGBHV), while DDC and SYNC operate from 2.3V to 3.6V and 4.5V to 5.5V supplies.
Power-Supply Bypassing and Ground Management
The MAX9511's high-frequency performance requires proper layout and bypassing. For best performance, place components as close to the device as possible. Digital or AC transient signals on AGND can create noise at the outputs. Return AGND to the lowest impedance ground available. Bypass the analog supply (VCC) with a 4.7F capacitor paralleled with a 0.22F and 0.001F capacitor to AGND, placed as close to the device as possible. Bypass the digital supplies (VDD1, VDD2) with a 0.1F capacitor to DGND, placed as close to the device as possible. Careful PC board ground layout minimizes crosstalk between the outputs.
MAX9511
SYNC Bandwidth-Limiting Capacitors
The output impedance, RSO, of the MAX9511 and an additional capacitance (CSYNC) can form a lowpass filter that reduces the jitter of the sync output signal. With RSO (55 typ) sync output impedance, the -3dB point of the lowpass filter is given by: f-3dB = 1 2RSOCSYNC
Choose CSYNC so f-3dB is well above the highest frequency of interest. TRANSISTOR COUNT: 353 PROCESS: BIPOLAR
Chip Information
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13
Complete VGA Interface with EMI Suppression MAX9511
Typical Operating Circuit
5V 4.7F 0.22F 5V 0.1F POWERMANAGEMENT CIRCUIT 2.3V TO 3.6V 0.1F 1nF REMOTE MONITOR 7 8 13 12 VDD2 1 VCC 17 DOCKING STATION SYNC BANDWIDTH LIMITING CAPACITORS CSYNC = 50pF TO 500pF CSYNC CSYNC
SHDN VDD1 DDC_DATA_IN
DDC_DATA_OUT
9 10 11
DDC_CLK_IN H_SYNC_IN V_SYNC_IN
DDC_CLK_OUT
16
H_SYNC_OUT V_SYNC_OUT
15 14 23
75 75
VIDEO CONTROLLER
MAX9511
GREEN_OUT
4 37.5
RED_IN
RED_OUT
21
75 75
BLUE_OUT 2 GREEN_IN
19
75 75
37.5
5
BLUE_IN RX
6
37.5 AGND 3, 20, 22, 24 DGND 18 RRX
14
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Complete VGA Interface with EMI Suppression
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.)
QSOP.EPS
MAX9511
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
E
1 1
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 ____________________ 15 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

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