TSH345 STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
Features
■ Selectable 6th order filtering of 36 MHz,
18 MHz and 9 MHz
■ 5 V single-supply operation ■ Internal input DC level shifter ■ No input capacitor required ■ 3 matched 6 dB amplifiers ■ AC or DC output-coupled ■ Very low harmonic distortion ■ Specified for 150 Ω loads ■ Data min. and max. are tested during production
Applications
■ High-end video systems ■ High definition TV (HDTV) ■ Broadcast and graphic video ■ Multimedia products
Description
The TSH345 is a triple single-supply video buffer featuring an internal gain of 6 dB and selectable filtering for HD and SD video outputs on 75 Ω video lines. The TSH345 is ideal to drive either Y- C, C V B S, Y- U - V, Y- P b - P r o r R - G - B s i g n a l s f r o m video DAC outputs. The main advantage of this circuit is its input DC level shifter. It allows you to drive video signals on 75 Ω video lines without damage to the synchronization tip, and without either input or output 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 in the best position for the greatest linearity. The TSH345 is available in the SO14 plastic package for optimum space-saving. G out R2 in R out +VCC B out R1 in G1 in GND8 DC Shifter 6dB 6dB 36MHz 18MHz 9MHz LPF 6dB 36MHz 18MHz 9MHz LPF 36MHz 18MHz 9MHz LPF B1 in 5 G2 in B2 in Fs1 Mux Fs0 MUXMUXMUX SO14 TSSOP14
1 Absolute maximum ratings and operating conditions
Table 1. Absolute maximum ratings (AMR)
- All voltage values, except differential volt age, are with respect to network terminal.
- The magnitude of input and output voltage must never exceed V CC +0.3 V.
Table 2. Operating conditions
- Tested in full production with +5 V single power supply.
2 Electrical characteristics
Table 3. Electrical characteristics at V CC = +5 V single supply, Tamb =2 5 ° C
2.02 V/V
0.3 V and 1 V
Table 4. Filter and standby settings, V CC = +5 V single supply, Tamb =2 5 ° C Table 5. Mux settings, V CC = +5 V single supply, Tamb =2 5 ° C
0 R1 G1 B1 Video1 selected
1 R2 G2 B2 Video2 selected
3 Power supply considerations
the PSRR in the higher frequencies. Figure 1. Circuit for power supply bypassing
4 Using the TSH345 to drive Y-C, C VBS, Y-U-V, Y-Pb-Pr
Figure 2. Implementation of the video driver on output video DACs Figure 3. Shapes of video signals comi ng from DACs (example for a black picture)
- Fclock=74.25MHz
- t=1/Fclock=13.5ns SD GND 4.6us 160ns 300mV Black (30IRE) 64us 150ns sync.tip sync.tip
Figure 4. Flexibility of the TSH345 for SD and HD signals 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. saturation of the driver against the lower rail. drive the video line, the shifted signal is multiplied by a gain of 2 or +6 dB.
4.1 Output capacitor
Figure 5. DC output coupling (1 of 3 channels) Figure 6. AC output coupling (1 of 3 channels)
- C S is a 100nF used to decrease the parasitic components of C in high frequencies.
- The 75-ohm resistor must be as clos e as possible to the output of the driver to minimize the effect of
5 Package information
In order to meet environmental requirements, STMicroelectronics offers these devices in ECOPACK® packages. These packages have a lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an STMicroelectronics trademark. ECOPACK specifications are available at: www.st.com
5.1 SO-14 package
Ref. Dimensions Millimeters Inches A1 . 7 5 0 . 0 6 8 a1 0.1 0.2 0.003 0.007 a2 1.65 0.064 b 0.35 0.46 0.013 0.018 b1 0.19 0.25 0.007 0.010 C0 . 5 0 . 0 1 9 c1 45° (typ.) D 8.55 8.75 0.336 0.344 E 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 7.62 0.300 F 3.8 4.0 0.149 0.157 G 4.6 5.3 0.181 0.208 L 0.5 1.27 0.019 0.050 M0 . 6 8 0 . 0 2 6 S 8° (max.)
5.2 TSSOP14 package
Ref. Dimensions Millimeters Inches A 1.2 0.047 b 0.19 0.30 0.007 0.012 c 0.09 0.20 0.004 0.0089 e 0.65 BSC 0.0256 BSC K 0 °8 ° 0 °8 ° c Eb A2A D PIN 1 IDENTIFICATION LKe
6 Ordering infomation
7 Revision history
Table 6. Order codes 29-May-07 1 Preliminary data, initial release.