Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video
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Transcript of Amplificadores de Alta Velocidade Dicas e Truques Nas Aplicacoes de Video
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High Speed Amplifiers
Video Tips and Tricks
Randy Stephens
Member Group Technical Staff
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Agenda
Video Overview Analog Video But Everything is Digital, Right?
Standards
Video Signal What Does it Look Like?
Why Use a Filter?
Test Equipment
Solving Common Video Issues Measurement Discrepancies
Input Coupling AC or DC
Output Coupling AC or DC
Output Coupling Frequency Tweaks
A Few Solutions Think Outside the Box Comparison to Passive Filters
Questions
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Analog Video is Everywhere
DVI/HDMI
Receiver
Tuner
VCR/DVDR
DDR SDRAM
Antenna/CableConnection
DTV, HDTV, CRT
AudioDAC Amp
AV Receiver
Digital AudioOutput Jack
CVBS
S-Video
ComponentYPbPr
1394Link &Phy
Media Interface Card
AudioA/D
TMDS341
Decoder /Video ADC
XDRMemory
Video Processor
High PerformanceClocking
Encoder /Video DAC
DVD Player
DSC
PVR Set Top Box
ProjectorDigi-Cam
PC
PMP
CameraPhone
MediaInterface
Logic
A
/V
Inputs
A/VO
utputs
CVBS
S-Video
ComponentYPbPr
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Overview Resolution & Format
3DCombFilter
Tuner
VideoDecoder(TVP5160)
CloseCaption
V Chip
Tele Text
Micro-Processor
EEPROM
or Flash
Audio Processor
De-Interlacer
Class D Audio Amp
(TPA3100D2)
Scaler
A/DConverter
DVI/RxHDCP/HDMI LVDS Tx
TTL Output
OSDSDRAM
DVIPC-VGA
YPbPr
S Video
CVBS (Composite)
RF In
Audio
LVDS Rx
LCD GateDriver
LCDPanel
Lamp
Back LightConverter
SDTVCVBS
SDTVCVBS
SDTV/EDTV/
HDTV
Component
SDTV/EDTV/
HDTV
ComponentSDTVS-Video
SDTVS-Video
SD/ED/HDTVYCbCr
Digital RGB
SD/ED/HDTVYCbCr
Digital RGB
VGA/SVGA/XGA
SXGA/UXGA/QXGA
AnalogRGB
VGA/SVGA/XGA
SXGA/UXGA/QXGA
AnalogRGB
VGA/SVGAXGA
SXGA/UXGA/QXGA
DigitalRGB
VGA/SVGAXGA
SXGA/UXGA/QXGA
DigitalRGB
HDMIComponent
New : Display Port
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Common Video StandardsSDTVStandard Definition Television:
CVBS (Composite Video Baseband Signal) - SMPTE 170M
S-Video
480i (NTSC) or 576i (PAL) Interlaced
EDTVEnhanced Definition Television:
480p (NTSC) or 576p (PAL)
Progressive - SMPTE 293M
HDTVHigh Definition Television:
720p Progressive - SMPTE 296M
1080i Interlaced - SMPTE 274M / ITU-R BT.709
1080p Progressive - SMPTE 274M / ITU-R BT.709
SMPTE = Society of Motion Picture and Television Engineers
ITU-R = International Telecommunication UnionRadiocommunication
ITU-R BT.1358
ITU-R BT.601 (Formerly
CCIR)
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Color Signal Flow
R
G
B
Gamma
R
G
B
YNTSC/PAL/480ip/576ip = 0.299R + 0.587G + 0.114BY720p/1080ip = 0.2126R + 0.7152G + 0.0722B
PB 480ip/576ip = 0.5 (B -Y) / (1 0.114)
PB 720p/1080ip = 0.5 (B -Y) / (1 0.0722)
Luma (Y)
Blue Color Difference (PB)
PR 480ip/576ip = 0.5 (R -Y) / (1 0.299)
PR 720p/1080ip = 0.5 (R -Y) / (1 0.2126)
Red Color Difference (PR)
U = 0.492 (B -Y)V = 0.877 (R -Y)
NTSC/PAL
NTSC = 3.58MHz
PAL = 4.43MHz
Subcarrier
Modulator
PB
PR
ComponentOutput
Y
S
I = Vcos 33 - Usin 33Q = Vsin 33 + Ucos 33
S-VideoOutput
CVBS
++
Chroma (C)
Simplified Color Flow in Consumer Video System
S
ource
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Video Signal Summary
SRMIN = 2 Pi Vpk (1Vpk) x 0.707 (-3dB) x 2 (to ensure no problems)
FormatStandard / Display
ResolutionSignal
Element
AnalogBandwidth
(MHz)
Ideal Min.SR
(V/us)
H. SyncWidth(us)
Max. VideoAmplitude
(Vpp)CVBS CVBS 4.2* ;
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CVBS Video Signal = S-Video Y + C
NTSC 100 IRE = 714mV
40 IRE = 286mVGR
RD
BL
Wh Yel Cy Gr Mg Rd BL BLK
100
89
70
59
41
30
11
0
S-Video Y100% Saturation
IRE Units
+0.714V
-0.286V
-40
-20
0
20
10
100
80
60
40
+0.700V
-0.300V
NTSC PAL
82.8
NTSC S-Video C'100% Saturation
IRE Units
20
60
40
-60
0
-20
-40
117 117109.2 109.282.8
167.1
0
283.5240.7 60.7 103.5
347.1
40
0
0
0.7V
0.62V
0.49V
0.41V
0.29V
0.21V
0.08V
0V
PAL 100 IRE = 700mV
40 IRE = 300mV
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100% Saturation Color Bars Screen Shots
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Screen Shots NTSC & PAL
NTSC: S-Video Y C
CVBSPAL: S-Video Y C
CVBSNote : 100% Color Saturation causes CVBS Signal to be about 1.25Vpp
75% Color Saturation causes CVBS Signal to be 1Vpp
10uS / Div10uS / Div
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Screen Shots 480i Component
480i YPBPR 480i GBR10uS / Div 10uS / Div
Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on Color Difference Signals
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Screen Shots 480p / 576p Component
480p YPBPR 576p YPBPR4uS / Div 4uS / Div
Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on Color Difference Signals
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Screen Shots 720p Component
720p @ 60HzYPBPR
720p @ 60HzGBR
4uS / Div 4uS / Div
Note : Maximum Voltage Swing is 1Vpp on Channels with Sync
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Screen Shots 1080i / 1080p Component
4uS / Div 2uS / Div1080i @ 60HzYPBPR
1080p @ 60HzYPBPR
Note : Maximum Voltage Swing is 1Vpp on Channels with Sync
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Screen Shot Computer Video (VGA)
1280 X 1024 @ 60Hz RGSB 1920 X 1440 @ 75Hz RGSB2uS / Div 1uS / Div
Notes : 1) Maximum Voltage Swing is 1Vpp on Channels with Sync2) HSync can also be found on All or None of these Signals
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SDTV Video DAC
Every video DAC shows aliasing
artifacts.
Vertical or diagonal lines appearthroughout picture.
Remember this Signal Feeds into anADC in modern designs -> Aliasing.
Wh Fil DAC O ?
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Why Filter DAC Output?Actual DVD Player Encoder (DAC) Output
-90
-80
-70
-60
-50
-40
-30
-20
000E+0 20E+6 40E+6 60E+6 80E+6 100E+6 120E+6
Frequency
Output-dB
-90
-80
-70
-60
-50
-40
-30
-20
000E+0 50E+6 100E+6 150E+6 200E+6 250E+6 300E+6 350E+6 400E+6
Frequency
Output-dB
Baseband
Signal
Nyquist
Zone 2 & 3
2Fs3Fs
4Fs5Fs 6Fs 7Fs 8Fs
9Fs 10Fs 11Fs 12Fs 13Fs 14Fs
Nyquist
Zone 4 & 5Nyquist
Zone 6 & 7 NyquistZone 8 & 9
Fs
Fs 2Fs3Fs
4Fs
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No DAC Filter Gives Poor Video
Buffer ampwithout filter:
Videodisplay shows
DAC imageinterference
Standard VideoTest Patterns
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Using DAC Filter Gives Good Video
THS7303 Bufferamp withfilter:
Videodisplay clean
Standard VideoTest Patterns
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Low Pass Filters : Part 1 - Amplitude
VERY Hard to Achieve in Any System
SYSTEM Level Response Not justthe Amplifier or Filter Alone
Targeted for Broadcast QualitySystems (Many Systems in Series andthe effects are additive)
Consumer Video is More Relaxed !!!
Most Standards Show Requirements
Example
ITU-R BT.601(SDTV)
StandardShows:
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5th-Order Filter Responses - Amplitude
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
100E+3 1E+6 10E+6 100E+6Frequency - Hz
Output-dB
0.5dB 10MHz Chebyshev
8.5MHz Modified Butterworth
Ex: Low Pass Filters - Amplitude
5th-Order Filter Responses - Ampli tude
-50
-40
-30
-20
-10
0
10
100E+3 1E+6 10E+6 100E+6Frequency - Hz
Output-dB
0.5dB 10MHz Chebyshev
8.5MHz Modified Butterworth
Look at a 5th-Order Filter Comparison:
Modified Butterworth at 8.5MHz
0.5-dB Chebyshev at 10MHz
Attenuation at 27-MHz :
Chebyshev = 57dB
Butterworth = 46dB
0.5dB Flatness Bandwidth :
Chebyshev = 10-MHz
Butterworth = 6-MHz
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Low Pass Filters : Part 2 - Group Delay
ITU-R BT.601(SDTV)
StandardShows:
Do NOT Forget About Group Delay !!!
Group Delay is Defined as:Change in Phase (Degrees)
360 X Change in Frequency (Hz)
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5th-Order Filter Responses - Group Delay
20
40
60
80
100
120
140
160
180
100E+3 1E+6 10E+6 100E+6Frequency
GroupDelay-ns
0.5dB 10MHz
Chebyshev
8.5MHz Modified Butterworth
Ex: Low Pass Filters Group Delay
5th-Order Filter Responses - Phase
-405
-360
-315
-270
-225
-180
-135
-90
-45
0
45
100E+3 1E+6 10E+6 100E+6Frequency
Phase-Degrees
0.5dB 10MHz
Chebyshev
8.5MHz Modified
Butterworth
Typically only Concerned with Group Delay Variation at a SpecificFrequency (Relative to 100kHz typ)
Absolute Value of Group Delay is Generally not a Concern - Exceptfor Channel to Channel Timing Matching
Why is this Important ??? ...
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Low Pass Filters Pulse Response
Remember:Video Signal Amplitude = Amount of Color,Brightness, etc. to Display on the Screen
If the Signal Goes from say Black to White
to Black (0V to 0.7V to 0V) in successivepixels, then overshoot and ringing must beavoided.
Otherwise smearing and other artifacts willbe seen on the display.
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5th-Order Filter Responses - Pulse Response
0.951
0.965
0.979
0.993
1.007
1.021
1.035
1.049
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Time - us
OutputVoltage
0.5dB 10MHz Chebyshev
8.5MHz Modified Butterworth
Input
Low Pass Filters Pulse Response
5th-Order Filter Responses - Pulse Response
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Time - us
OutputVoltage
0.5dB 10MHz Chebyshev
8.5MHz Modified ButterworthInput
Rule of Thumb : The more variation in Group Delay, Themore Overshoot and Ringing will Occur
1 IRE (~7mV) Settling Time: Chebyshev = 482nSButterworth = 217nS
C t C I t t d Filt P d t
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Current Consumer Integrated Filter ProductsAll Utilize Butterworth Filters
VideoStandard
Fixed
Filter
SDTV :CVBS
S-Video480i / 576i
Selectable
LPF
HDTV :1080p501080p60
HDTV :720p1080i
1080p24/30
EDTV :480p576p
THS7303 / THS7353
3-Channels9/16/35MHz Filters
I2C Control
THS73143-Channels
8.5MHz Filters
THS7313
3-Channels8.5MHz FiltersI2C Control
THS73153-Channels
8.5MHz FiltersGain = 5.2V/V
Bypass Mode150MHz
THS73183-Channels
20MHz Filters3.5mA Total
WCSP
THS73163-Channels
36MHz Filters
OPA360 / 611-Ch / 9MHz Filter
2V/V / 5.2V/V
THS73744-Channels
9.5MHz Filters
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Test Equipment for Video - Standard Definition
VM700TTHESD Video
Analyzer NTSC and PAL
CVBS, S-Video, Component
Differential Gain and Phase
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CVBS Video Differential Gain and Phase
Differential Phase: dP Change in Phase (Hue) of the color modulation
(Chroma) due to a change in brightness (Luma)amplitude
Affects the actual color
Consumer Products > 0.5%
Professional Products target < 0.05%
Differential Gain: dG
Change in Amplitude (Saturation) of the colormodulation (Chroma) due to a change inbrightness (Luma) amplitude
Affects color Saturation Consumer Products > 0.5 Professional Products target < 0.05
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VM700T Tests
Signal to Noise Ratio MeasurementK2T Pulse Test
Measures Potential Issues Before and Aftera Pulse
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VM700T Tests
Short Time Distortion Test
Measures Potential Overshoot and SettlingTime Issues
Horizontal Sync + Color Burst Timing
Measures H-Sync Amplitude, Time, rise/falltimes, color burst amplitude and duration
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VM700T Tests
Chroma and Luma Gain Delay
Measures Both Luma and Chroma Signalsfor Gain Errors and Relative Timing
Note Frequency Responses Can also be done, but a Network Analyzer isSignificantly Better than Video Analyzers
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VM5000 Testing
VM5000 Just About Everything ElseNTSC and PAL Component Video (SD/ED/HD)
RGB, GBR
Recently Replaced by VM6000
Test Results are Not Graphical (like VM700T)
Test Results are Numbers Only
Examples:
SNR = 70.1dB
Y to Pb, Y to Pr, Pb to PrTiming Error = 1.1ns, 1.1ns, 0.5ns
Color Bar Amplitude : White = 698mV, Yellow
= 647mV, Cyan = 549mV, Green = 498mV..
Etc
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VM5000 Test
Ex: Short Time Distortion Test
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Measurement Issues
Key Issue Differences Between Bench Testing and
Customer Product Testing Bench Measurements
Uses Video Signal Generators (Ex: Tektronix TG700, Quantum Data802R, etc)
Many VM700T / VM5000 Tests can Calibrate Out the Video Generator +
Cables + VM700T / VM5000 Measurement Results with Amplifier in the Signal
Chain shows Only Amplifier Impact on the Video Signal
Calibrate Path MeasurementVideo Generator
DUT / EVM
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Measurement Issues
Key Issue Differences Between Bench Testing and
Customer Product Testing Customer System Measurements
Uses Video Encoder/DAC/SOC as Signal Source
Uses SOC/Encoder/DAC On-Chip Signals, or
DVD/Sat/Cable/Ext. Input/etc. Signal Source (+ Decoding +
Processing + Encoder) Little or No Calibration done
Customer Shows Test Results of the System which Shows PossiblePerformance Issues
Measurement
Source(Cable/Sat/DVD/Gen)
System
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Measurement Issues
How to Resolve Issue: Measure the Signal Before the Amplifier and then
After the Amplifier
Possible Solutions:
Many SOC/Encoders/DAC have some capability to tweak theprocessing. Usually a Register Setting.
If a Front-End Decoder is being used, maybe a tweak to aRegister on the Decoder can help.
If all else fails, Maybe some Tweaks to the Amplifier Can
Help the Customer.
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Resolving Issues Common Solutions
Modify the Interface Between the DAC outputand the Amplifier.
Modify the Output Interface to the Line
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC /Encoder
+3.3V
1
2
3
4
CVBS
Y
C
CVBSOut
75
Y
Out
75
C
Out75+3.3V
75
75
SDTVCVBS
S-Video YS-Video C480i/576iYPBPR
GBR 75
S-Video
R
R
R
THS7314
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Video Amplifier Signal Biasing Single Supply
DC Modes
AC Modes
DC
DC+SHIFT
ACSTC
ACBIAS
1.65V3.3V
AC BIAS
AC Sync Tip Clamp
250mV0V
DC + Level Shift
250mV
0V
DC
0V
Make Sure Input Signalis >50mV or OutputClipping May Occur
Allows Input Signal to go to 0Vwithout Output Clipping Problems
3.3V
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Input Tweaks:
Sometimes the Interface is Wrong Current Sinking DAC is DC coupled to the Amplifier
Problem is DC Level is Typically too High for DC Coupling to OccurResulting in Saturation of the Amplifier
Solution AC Couple between the DAC and Amplifier
Utilize Sync Tip Clamp Function of the Amplifier for Video Signalswith Bottom-Level Sync (ex: CVBS, S-Video Y, Comp. Y)
Utilize Bias for all other signals (ex: S-Video C, Comp. Pb and Pr)
Resolving Issues Input Tweak
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC /Encoder
+3.3V
1
2
3
4
Y
PB
PR
+3.3V
SDTV480i/576iYPBPR
GBR
THS7314
0.1uF
22uF
+
R
+3.3V
R
+3.3V
R
+3.3V
0.1uF
0.1uF
0.1uF
3.01M
+3.3V
3.01M
+3.3V
Bias
STC
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Resolving Issues Input Tweak
Input Tweaks:
DC Coupling is Generally Best Used with Current Source DACs with Output Voltage of Sync Signal
Approaching 0V (Most Common)
Ideal for Amplifiers with Internal Level Shift to Prevent Output Sat.
AC Coupling can also Work, but DC Coupling is Generally Better
No AC Coupled Tilt / Droop
No Abberations due to Sync Tip Clamp Function (Never Perfect)
Even if DC Coupling is Utilized, Tweaking the DAC Termination Resistor(and/or DAC Bias Setting Resistor) may Improve Performance
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC /Encoder
+3.3V
1
2
3
4
CVBS
Y
C
+3.3V
SDTVCVBS
S-Video YS-Video C480i/576iYPBPR
GBR
R
R
R
THS7314DC Coupling
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Output Coupling AC or DC ???
AC Coupled
Legacy Way of Output Coupling
Universally Acceptable
Meets All Specifications for DC levels on Output
Possible Issues:
Line Tilt or Droop
Large Capacitor (330uF to 470uF typ) = Increased Cost andPCB Size
330uF
0.1uF
+
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC /Encoder
+3.3V
1
2
3
4
CVBS
Y
C
CVBSOut
75
Y
Out
75
C
Out75
+3V to 5V
75
75
SDTVCVBS
S-Video YS-Video C480i/576i
YPBPR
GBR 75
S-Video
R
R
R
THS7314330uF+
0.1uF
22uF
+
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Output Coupling AC or DC ???
DC Coupled
New Way of Coupling No Capacitor = Lower Cost and Smaller PCB Area
No Line Tilt or Droop
Possible Issues:
Amplifier Offsets Cause a Current Flow.
EIA-770 Specification Requires Backporch Voltage = 0V +/- 1V atReceiver (0V +/- 2V at Amplifier Output).
Japan Specification EIAJ CP-1203 Requires Output Voltage = 0V +/-0.1V with No Video Signal.
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC /Encoder
+3.3V
1
2
3
4
CVBS
Y
C
CVBSOut
75
Y
Out
75
C
Out75+3.3V
75
75
SDTVCVBS
S-Video YS-Video C480i/576i
YPBPR
GBR 75
S-Video
R
R
R
THS7314
0V 1V
0.7V 1V
-0.3V 1V
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Output Coupling - AC with SAG Correction
To See How it Works, Break it up into
Low-Frequency and High-FrequencyOperation:
DC : Zc = infinityAmp Gain = 1 + [(R1 + RF) / RG]
High Freq: Zc = 0
Amp Gain = 1+[((R1||R2) + RF) / RG)= 2 V/V (6 dB)
Choosing Proper Component Values willresult in the Amplifier Gain Increasing asthe Capacitors Impedance Increases
(which would normally result in Video
Output amplitude reduction).Thus the effects cancel each other outresulting in Low-Frequency Extensionwhile using Much Smaller Capacitors.
Out
SAG
47uF
33uF
75
75
VideoOut
+
-
RG RF
R1
R2
Input
-20
-15
-10
-5
0
5
10
15
20
1 10 100
Frequency - Hz
Gain-dB
47uF Only
Amp Gain
330uF
-20
-15
-10
-5
0
5
10
15
20
1 10 100
Frequency - Hz
Gain-dB
Amp Gain + 47uF = Same as 330uF + 6dB
SAG Correction Real Data
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AC-Bypass Video Output Responses
-18
-15
-12
-9
-6
-3
0
3
1 10 100Frequency - Hz
Output-dB
47uF
100uF
330uF
47uF + 33uF SAG
Out
SAG
47uF
33uF
75
75
VideoOut
+
-
RG RF
R1
R2
Input
MeasurementPoint
AC-Bypass Amplifer Responses
0
3
6
9
12
15
1 10 100Frequency - Hz
Output-dB
AmplifierOutput
with SAG
SAG FeedbackPoint
Traditional AmplifierOutput (330uF)
SAG = 47uF + 33UF
Amp OutputMeasurement Point
SAG Correction Real Data
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Resolving Issues Output Tweak
Modify the Source Termination Resistor
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT1
2
3
4
CVBSOut
75
Y
Out
75
C
Out75+3.3V
75
75 75
S-Video
THS7314
.07575
75IN
OUT
V
V
SNTERMI
NTERM
IN
OUT
RR
R
V
V
Traditional :
Ex: If Gain Needs to be Increased, Reducing Source ResistorIncreases System Gain.
While not an Ideal Solution, Testing (K2T Pulse) Shows thatReflections are not an Issue and all Other Tests Pass
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Resolving Issues Output Tweak
Frequency Compensation
75
75+
-
R C
VOUT
VIN
275(2
)75(1
sC
sC
V
V
IN
OUT
Should Not Let R be less than 25-ohms as this can causeInstability to the Amplifier
Capacitive Load of Cable will Appear Directly on the Amplifier Outputwith no R.
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Resolving Issues Output Tweak
75
75+
-
R C
VOUT
VIN
C = 180pF
R = Variable
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Resolving Issues Output Tweak
75
75+
-
R C
VOUT
VIN
C = Variable
R = 75
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Resolving Issues Output Tweak
THS7314 Bench Testing
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
1E+6 10E+6Frequency
Output-
dB
No Compensation
120pF
R = 75-Ohms
180pF
220pF
270pF
75
75+
-
R C
VOUT
VIN
Drawback An Increase in Group Delay Variation
Configuration Tweak CVBS From S-Video
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Configuration Tweak CVBS From S-Video
Scenario: DAC only has S-Video Y and C Outputs. Need CVBS Output.Solution: THS7314 Low Cost 3-Channel SDTV Amplifier
330uF
0.1uF
+
5
8
7
6
VS+ GND
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT
DAC
/Encoder
+VD
1
2
3
4
Y
C
CVBS
Out75
Y
Out
75
C
Out75
+VA
75
75 75
S-VideoOPTIONAL - 1
RDAC
THS7314
330uF+
0.1uF
10uF
+
0.1uF
0.1uF
+VA
RPRDAC
OPTIONAL - 2
150
150
0.1uF
R C
Optional - 3
Optional 1 : Not Required. Only needed if DAC voltages are above 1.4V Max
Note : RP is not critical. Allowable value is from 3.1Mohm to 5.6Mohm Sets DC inputBias operating point and ultimately output DC operating point.
Optional 2 : Not Required for SMPTE/IEC/EIA standards. Can be used ifdesired or to meet EIAJ CP1203 Specification
Optional 3 : Not Required. Use to get a boost in the upper frequency area dueto 2 X filters for CVBS signal. Good starting point is R = 150 and C = 68 pF
Configuration Tweak - SCART
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Configuration Tweak - SCARTScenario: System Needs to Support SCART output Cost IssuesSolution: THS7374 + Low Cost Switches
11
14
13
12
CH.4 IN CH.4 OUT
CH.2 IN
CH.3 IN
CH.1 IN
CH.3 OUT
CH.2 OUT
CH.1 OUT1
2
3
4
R
G
TV CVBS /Sync Out
75
75
75
+3Vto 5V
VideoSOC
/DAC
R1
R1
THS7374
TV R Out
TV G Out
B
5
6
7
10
9
8NC
BYPASSDISABLE
VS+GND
NC
R1
75
TV B Out
To GPIOController Or GND
TV
SCART330uF *+
330uF *
330uF *
330uF *
17
1918
20
13
1514
16
9
1110
12
5
76
8
1
32
4
17
1918
20
13
1514
16
9
1110
12
5
76
8
1
32
4
21*Optional
470
AudioLeft Out 47uF
470
AudioRight Out 47uF
N/C
N/C
N/C
N/C
N/C
75VCR CVBS /
Sync Out330uF *+
VCRSCART
N/C
N/C
N/C
N/C
N/C
75N/C
+12V
ABC
INHVEEVSS CD4053
CVBS /
SyncR1
Audio
Left
R2
Right
R2
22k
22k
100
47uF
100
47uF
100k
100k
470
AudioLeft Out 47uF
470
AudioRight Out 47uF
AmpLPFBias
0.1uF
220
75
10k
Fast BlankRGB / CVBS(From GPIO)
470
10k
1.5k
+12V
1.8k
Stby/TV(From GPIO)
10k
16:9 / 4:3
(From GPIO)
22k
AudioLeft In
AudioRight In
VCR Mode
VCR CVBS In
+Vbias
AmpLPFBias
21
NE5532DRV600DRV601
SOC
PCM17xx
Note:
This Example Does NotProvide ALL SCARTfeatures, but can work formany systems
Other circuit configurationsavailable that include morefunctions.
Passive vs Active Filters
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Passive vs. Active Filters
Active Filter Passive Filter
Cost Very Low to High Very Low
ToleranceGood due to Element
Matching
Inductor15% to20%
Capacitor10% to15%
Corner Frequency +/- 10% typ+/-15% to +/-25%
(Depends on ComponentTolerances)
TemperatureTolerance
Good due to Matching andLow Coefficient Elements Poor
PCB Area Low to Mid Low to High
ImpedanceVariations
Small Input and OutputImpedance Variations
Significant Input andOutput Variations
Misc. Info Can Save System PowerInductors are Magnetic
Components
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Active Filters Save Power ??? Yes they Can
VideoDAC / Encoder
75
3V
VIDEO OUT
75
26.6 mA
Active Current
Quiescent Current
26.6 mA
1V
1V
26.6 mA
No Buffer
With Buffer
DAC Quiescent Current = 2mA/Ch 6.6 mW/Ch
DAC Quiescent Current = 26.6mA/Ch 88 mW/Ch
3.3V 3.3V
3.3V
VideoDAC / Encoder
499
VIDEO OUT
75
75
x 2
2 mA
2 mA
1.5 mA
2V1V
13 . 3 mA
1V
Active Current 14.5mA (48mW)
Real Video Signals Result
in Buffer current of about
7mA RMS System
Savings of60mW/Ch
DAC Quiescent Current with ~1.24Vpp (100% CVBS) = 33mA/Ch 109 mW/Ch
DAC Quiescent Current with ~1.24Vpp = 2.5mA/Ch 8.3mW/Ch
P i Fil M C l A l i
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Passive Filter Monte Carlo Analysis
DAC
75 150pF
2.2uH 2.2uH
75150pF470pF
Example: 5-Pole 8.5MHzButterworth Passive Filter
Monte Carlo Anaylsis
Inductors +/-15%
Capacitors +/-10%
Resistors +/-1%
Amplitude Variations
Group Delay Variations
P i Fil M C l A l i
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Passive Filter Monte Carlo Analysis
DAC
75 150pF
2.2uH 2.2uH
75150pF470pF
Example: 5-Pole 8.5MHzButterworth Passive Filter
Monte Carlo Anaylsis
Inductors +/-15%
Capacitors +/-10%
Resistors +/-1%
Input and Output
ImpedanceVariations
Unit StepResponseVariations
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Questions?