TSH346 STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
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 Ω loads ■ Minimum and maximum data is tested during production
Applications
■ High-end video systems ■ High definition TV (HDTV) ■ Broadcast and graphic video ■ Multimedia products
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-Ω 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-Ω 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. Top View
1 R out
+VCC Pin1 identification DC Shifter 6dB 6dB 6dB 36MHz LPF B in B out GND 36MHz LPF 36MHz LPF SO-8 (plastic package)
1 Absolute maximum ratings and operating conditions
Table 1. Absolute maximum ratings (AMR)
- All voltage values, except the differential volt age, are with respect to the network terminal.
- The magnitude of the input and output voltages must never exceed V CC +0.3 V.
Table 2. Operating conditions
- Tested in full production with a +5 V single power supply.
2 Electrical characteristics
Table 3. V CC = +5 V single supply, Tamb = 25° C (unless otherwise specified)
Figure 19. VOL vs. temperature Figure 20. Gain vs. temperature
3 Power supply considerations and improvement of the
Figure 21. Circuit for power supply bypassing
4 Using the TSH346 to drive YC, C VBS, YUV, YPbPr and
Figure 24. Implementation of the video driver on output video DACs
1 Vpp
2 Vpp
Figure 25. Shapes of HD video signals comi ng from DACs including the synchronization tip 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. real advantage in terms of cost and board space. the driver against the lower rail. drive the video line the shifted signal is multiplied by a gain of +2 or +6 dB.
Figure 26. Flexible solution for SD and HD signals
4.1 Output capacitor
used to provide a very low cut-off frequency close to 5 Hz (Figure 28). Figure 27. IDC output coupling (1 of 3 channels) Figure 28. AC output coupling (1 of 3 channels)
- C S is a 100 nF used to decrease the parasitic components of C in high frequencies.
- The 75- Ω resistor must be as close as possible to the output of the driver to minimize the effect of parasitic
5 Package information
In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK ® is an ST trademark.
Figure 29. SO-8 package mechanical drawing Table 4. SO-8 package mechanical data
6 Ordering information
Table 5. Order codes
7 Revision history
Table 6. Document revision history 29-May-2007 1 Initial release. 16-Dec-2008 2 Added curves in Chapter 2: Electrical characteristics. Added all test limits in Table 3.