TSH122 Datasheet, PDF (10/16 Pages) STMicroelectronics – Ultra low power video buffer,filter with power-down

Application information
TSH122
3.2
3.2.1
3.2.2
Implementation considerations
Input
The DC level shifter optimizes the position of the video signal with no clamping on the output
rails.
Filter
A reconstruction filter is used to attenuate the DAC’s sampling frequency because it
generates a parasitic signal in the video spectrum (typically at 27 MHz in the case of
standard video). This function is fulfilled while keeping a low group delay and a good gain
flatness along the video band.
Figure 25. Internal schematic
2.25 V to 5 V
DC shifter
+Vcc
6
5 ^Power-down
Input 1 LPF _{+ +}
6^th order
-
2R
R
2R
4 ^Output
2R
3
SAG
2
GND
3.2.3
Output
In an AC-coupling configuration, the SAG correction allows use of two small low-cost
capacitors in place of one large capacitor (see Figure 26). The AC-coupling output reduces
the power consumption by removing the DC component included in the signal.
Nevertheless, the output can be directly connected to the line without any capacitor. In this
case, the OUT and SAG pins are connected together and the equivalent gain of the buffer
remains at 6 dB (see Figure 27).
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