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TSH346
Triple video buffer/filter for HD video applications
Features

6th order filtering of 36 MHz 5 V single-supply operation Internal input DC level shifter No input capacitor required Three matched 6 dB amplifiers AC or DC output-coupled Very low harmonic distortion Specified for 150 loads Minimum and maximum data is tested during production
R in 1
Pin1 identification
SO-8 (plastic package)
Top View
36MHz LPF
+ + +
6dB
8 R out
Applications

G in 2
36MHz LPF
6dB
7 G out
High-end video systems High definition TV (HDTV) Broadcast and graphic video Multimedia products
+VCC 4 B in 3
36MHz LPF
6dB
6 B out
DC Shifter
5 GND
Description
The TSH346 is a triple single-supply video buffer featuring an internal gain of 6 dB and a 36 MHz filtering for HD video outputs on 75- video lines. The TSH346 is ideal to drive either YUV, YPbPr or RGB signals from video DAC outputs. The main advantage of this circuit is that its input DC level shifter allows for video signals on 75- video lines without damaging the synchronization tip of the video signal, and with no input capacitor, while using a single 5 V power supply. The DC level shifter is internally fixed and optimized to keep the output video signals between low and high output rails. This level is as low as possible to minimize the output DC level in the video line. The TSH346 is available in an SO-8 plastic package for optimum space saving.
December 2008
Rev 2
1/18
www.st.com 18
Absolute maximum ratings and operating conditions
TSH346
1
Table 1.
Symbol VCC Vin Toper Tstd Tj Rthjc Rthja Pmax. ESD
Absolute maximum ratings and operating conditions
Absolute maximum ratings (AMR)
Parameter Supply voltage (1) Input voltage range
(2)
Value 6 2.5 -40 to +85 -65 to +150 150 28 150 1 500 2 100
Unit V V C C C C/W C/W W V kV V
Operating free air temperature range Storage temperature Maximum junction temperature SO8 thermal resistance junction to case SO8 thermal resistance junction to ambient area Maximum power dissipation (at Tamb = 25 C) for Tj = 150 C CDM: charged device model HBM: human body model MM: machine model
1. All voltage values, except the differential voltage, are with respect to the network terminal. 2. The magnitude of the input and output voltages must never exceed VCC +0.3 V.
Table 2.
Symbol VCC
Operating conditions
Parameter Power supply voltage Value 4.5 to 5.5 (1) Unit V
1. Tested in full production with a +5 V single power supply.
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TSH346
Electrical characteristics
2
Table 3.
Symbol
Electrical characteristics
VCC = +5 V single supply, Tamb = 25 C (unless otherwise specified)
Parameter Test conditions Min. Typ. Max. Unit
DC performance VDC Output DC shift RL = 150 Tamb , -40 C < Tamb < +85 C Input bias current Input resistance Input capacitance No load, input to GND ICC Total supply current -40 C < Tamb < +85 C DC voltage gain RL = 150 , Vin = 0.5 V -40 C < Tamb < +85 C Output characteristics VOH VOL High level output voltage Low level output voltage Isource IOUT Isink Filtering Small signal, VICM = 0.5 V, RL = 150 -3 dB bandwidth -1 dB bandwidth Small signal, F = 74.25 MHz VICM = 0.5 V, RL = 150 RL = 150 -40 C < Tamb < +85 C RL = 150 76 -40 C < Tamb < +85 C 106 -40 C < Tamb < +85 C 3.4 3.9 V 3.8 47 100 91 mA 134 126 mV 1.96 45 2 1.96 2.05 V/V Tamb , input to GND -40 C < Tamb < +85 C 100 240 310 1.3 1.4 1 0.1 44.6 51.6 mA 3.6 A M pF 440 mV
Iib Rin Cin
G
Bandwidth High definition Attenuation D Noise eN Total input voltage noise Delay between each channel
25 25
36 32 32 0.5
MHz
dB ns
F = 100 kHz, RIN = 50
86
nV/ Hz
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Electrical characteristics
TSH346
Figure 1.
10
Filtering
Figure 2.
6.2
Gain flatness
0
6.0
Filter response (dB)
-10
Filter response (dB)
Vcc=5V small signal Load=150
10M 100M
5.8
-20
5.6
-30
-40
5.4
Vcc=5V small signal Load=150
1M 10M
-50 1M
5.2
Frequency (Hz)
Frequency (Hz)
Figure 3.
0 -10 -20
Distortion 1 MHz (HD)
Figure 4.
0 -10 -20
Distortion 10 MHz (HD)
Vcc=5V F=1MHz Load=150
Vcc=5V F=10MHz Load=150
HD2 & HD3 (dBc)
-40 -50 -60 -70 -80 HD3 -90 -100 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 HD2
HD2 & HD3 (dBc)
-30
-30 -40 -50 -60 -70 -80 -90 -100 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 HD3 HD2
Output Amplitude (Vp-p)
Output Amplitude (Vp-p)
Figure 5.
1000
Input noise vs. frequency
Vcc=5V No load
Figure 6.
-40
Channel crosstalk vs. frequency
-45
Input: 1Vp-p Vcc=5V Load=150
Input Noise (nV/VHz)
-50
Gain (dB)
100 100 1k 10k 100k 1M
-55
-60
-65
-70
-75 1M
10M
100M
Frequency (Hz)
Frequency (Hz)
4/18
TSH346
Electrical characteristics
Figure 7.
2.10
Gain vs. input amplitude
Figure 8.
5.0 4.5 4.0
Output vs input amplitude
Vcc=5V Load=150
2.05
Vcc=5V Load=150
VOH
3.5
Gain (V/V)
2.00
Vout (V)
3.0 2.5 2.0 1.5
1.95 1.0 0.5 Output DCshift 1.90 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Vin (Vp-p)
Vin (V)
Figure 9.
50
Current consumption vs. supply
Figure 10. Supply current vs. temperature
50 49 48 47
Vcc=5V no Load
40
Vcc=5V no Load
Icc (mA)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Icc (mA)
30
46 45 44 43
20
10
42 41
0 0.0
40 -40
-20
0
20
40
60
80
Vcc (V)
Temperature (C)
Figure 11.
60 55
Filtering vs. temperature
Figure 12. Filter attenuation vs. temperature
60
Vcc=5V Load=150
55 50
Vcc=5V Load=150
-1dB Bandwidth (MHz)
50 45 40 35 30 25 20 -40
Attenuation (dB)
45 40 35 30 25 20 -40
HD, f=74.25MHz
-20
0
20
40
60
80
-20
0
20
40
60
80
Temperature (C)
Temperature (C)
5/18
Electrical characteristics
TSH346
Figure 13. Gain matching vs. temperature
5
Figure 14. Output DC shift vs. temperature
400 375 350 325
Vcc=5V Load=150
4
Vcc=5V Load=150
3
DCshift (mV)
-20 0 20 40 60 80
300 275 250 225 200 175
MG (%)
2
1
150 125
0 -40
100 -40
-20
0
20
40
60
80
Temperature (C)
Temperature (C)
Figure 15. Isink vs. temperature
150 140
Figure 16. Isource vs. temperature
120
110 130 120 110 100 90 80 70 60 60 50 -40 100
Isource (mA)
Isink (mA)
90
80
70
Vcc=5V
-20 0 20 40 60 80 50 -40
Vcc=5V
-20 0 20 40 60 80
Temperature (C)
Temperature (C)
Figure 17.
2.0 1.8 1.6
Ibias vs. temperature
Figure 18. VOH vs. temperature
4.00
Vcc=5V
3.95 3.90
1.4
Ibias (A)
VOH (V)
1.2 1.0 0.8 0.6
3.85 3.80 3.75 3.70
0.4 0.2 0.0 -40 3.65 3.60 -40
Vcc=5V Load=150
-20 0 20 40 60 80
-20
0
20
40
60
80
Temperature (C)
Temperature (C)
6/18
TSH346
Electrical characteristics
Figure 19. VOL vs. temperature
60
Figure 20. Gain vs. temperature
2.20 2.15
55 2.10 50 2.05 2.00 1.95 1.90 35
VOL (mV)
45
40
Vcc=5V Load=150
-20 0 20 40 60 80
Gain (dB)
1.85 1.80 -40
Vcc=5V Load=150
-20 0 20 40 60 80
30 -40
Temperature (C)
Temperature (C)
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Power supply considerations and improvement of the PSRR
TSH346
3
Power supply considerations and improvement of the PSRR
Correct power supply bypassing is very important to optimize performance in low and highfrequency ranges. Bypass capacitors should be placed as close as possible to the IC pin (pin 4) to improve high-frequency bypassing. A capacitor (CLF) greater than 10 F is necessary to improve the PSRR in low frequencies. For better quality bypassing, a capacitor of 100 nF (CHF) can be added. CHF must be placed as close as possible to the IC pin, to improve the noise supply rejection in the higher frequency ranges. A coil can be added in order to better reject the noise from the supply and to prevent current peaks as much as possible. Figure 21. Circuit for power supply bypassing
+VCC
Coil CLF
+
CHF 4 R G B 5 TSH346
AM00824
8/18
TSH346
Power supply considerations and improvement of the PSRR Figure 22. Circuit for noise rejection improvement measurement
S R +5 V
T-bias Coil + CLF AGILENT 4395A CHF 50 TSH346 50 A
AM00825
Figure 23 shows how the power supply noise rejection evolves versus frequency depending on how carefully the power supply decoupling is achieved. Figure 23. Power supply noise rejection
0 -10
Noise rejection ratio (dB)
-20 -30 -40 -50 -60 -70 -80 10k
Vcc=5V(dc)+0.2Vp-p(ac) Decoupling capacitor: 10F+100nF Load=150 Noise rejection=20 log (VCC/Vout)
no coil
coil=560H
100k
1M
10M
100M
Frequency (Hz)
9/18
Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components
TSH346
4
Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components
Figure 24. Implementation of the video driver on output video DACs
+5 V Reconstruction filtering LPF 1 Vpp 2 Vpp + + + 6 dB
Y
Video DAC
75
75
cable
1 Vpp 75
TV
Pb
Video DAC 0. 0.7 Vpp
Reconstruction filtering LPF + + + 6 dB
75
75
cable
0.7 Vpp 75
1. 1.4 Vpp
Pr
Video DAC 0. 0.7 Vpp
Reconstruction filtering LPF + + + 6 dB
75
75
cable
0.7 Vpp 75
TSH346
GND -5 V
1. 1.4 Vpp
AM00826
10/18
TSH346
Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components
Figure 25. Shapes of HD video signals coming from DACs including the synchronization tip (Y signal)
White (100IRE) 54 ns (4t) 27 ns (2t) 27 ns (2t) Image content
590 ns (44 t)
300 mV Black (30IRE)
300 mV
GN D
590 ns (44 t)
14.8 us (110 0t): 1920/1080i 24.3 us (180 0t): 1280/720i
s yn c.t ip *Fclock=74.25 MHz *t=1/Fclock=13.5 ns
AM00827
The TSH346 is used to drive high definition video signals up to 30 MHz. It can drive components such as YPbPr and RGB where the bottom of the signal is close to zero volts. An internal input DC value is added to the video signal in order to shift the bottom from GND. The shift is not based on the average of the signal, but is an analog summation of a DC component to the video signal. Therefore, no input capacitors are required. This provides a real advantage in terms of cost and board space. Under these conditions, it is possible to drive the signal in single supply with no saturation of the driver against the lower rail. Because half of the signal is lost through output impedance matching, in order to correctly drive the video line the shifted signal is multiplied by a gain of +2 or +6 dB.
11/18
Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components Figure 26. Flexible solution for SD and HD signals
TSH346
HD
DAC
+5V
R
150
TV
75
Cable
75
DAC
G
150
75
Cable
75
DAC
B
150
TSH346 SO8
75
Cable RCA SCART
75
SD
DAC
+5V
R-G-B, Y-C-CVBS
75
Y,G
150
Cable
75
DAC
Pb,B,C
150
75
Cable
75
DAC
Pr,R,CVBS
150
TSH173 TSH103 SO8
75
Cable
75
SD CVBS
DAC
150
+5V
Y-C
75
TSH122 SC70
Cable
75
CVBS
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TSH346
Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components
4.1
Output capacitor
The output can be either DC- or AC-coupled, and can be directly connected to the line via a 75- resistor (4) (Figure 27). Alternatively, an output capacitor can be used to remove any DC components in the load. Assuming a 150- load, a coupling capacitor of 220 F can be used to provide a very low cut-off frequency close to 5 Hz (Figure 28). Figure 27. IDC output coupling (1 of 3 channels)
+5V Video DAC 150 75 TSH346 75
75 cable
AM00828
Figure 28. AC output coupling (1 of 3 channels)
+5V Video DAC 150 CS 75 TSH346 C = 220 F 75 +
cable
75
AM00829
1. CS is a 100 nF used to decrease the parasitic components of C in high frequencies. 2. The 75- resistor must be as close as possible to the output of the driver to minimize the effect of parasitic capacitance.
13/18
Package information
TSH346
5
Package information
In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK(R) packages, depending on their level of environmental compliance. ECOPACK(R) specifications, grade definitions and product status are available at: www.st.com. ECOPACK(R) is an ST trademark.
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TSH346 Figure 29. SO-8 package mechanical drawing
Package information
Table 4.
SO-8 package mechanical data
Dimensions
Ref. Min. A A1 A2 b c D E E1 e h L L1 k ccc 0 0.25 0.40 0.10 1.25 0.28 0.17 4.80 5.80 3.80
Millimeters Typ. Max. 1.75 0.25 0.004 0.049 0.48 0.23 4.90 6.00 3.90 1.27 0.50 1.27 1.04 8 0.10 1 0.010 0.016 5.00 6.20 4.00 0.011 0.007 0.189 0.228 0.150 Min.
Inches Typ. Max. 0.069 0.010
0.019 0.010 0.193 0.236 0.154 0.050 0.020 0.050 0.040 8 0.004 0.197 0.244 0.157
15/18
Ordering information
TSH346
6
Ordering information
Table 5. Order codes
Temperature range -40C to +85C Package SO-8 Packing Tube Tape & reel Marking TSH346I TSH346I
Part number TSH346ID TSH346IDT
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TSH346
Revision history
7
Revision history
Table 6.
Date 29-May-2007 16-Dec-2008
Document revision history
Revision 1 2 Initial release. Added curves in Chapter 2: Electrical characteristics. Added all test limits in Table 3. Changes
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TSH346
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