OPA361-Q1 Datasheet, PDF (12/18 Pages) Texas Instruments – 3V Video Amplifier with Internal Gain and Filter in SC70

OPA361-Q1
SBOS552 – MARCH 2011
OPA361 Disable Pulse
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OPA361 Ouput Pulled LOW
Due to Video Load
Equilization Pulses
1st Vertical Sync Pulse
Vertical Sync Pul ses
Figure 9. Output of OPA361-Q1 Pulled Down: TV Connected.
TWL92230
1.8V DAC 0.5V V_REF
OMAP2420
OPA361
Video
DAC
+In
R_SET
500Ω
2-Pole
Filter
Regulator V_AUX
V+ 2.5Vor 2.8V
1.8V
10mV
Out ^75Ω
PullUp
10kΩ
+
75Ω
4kΩ
G =5.2V/V
TV Detect
GPIO⁽³⁾
Enable
TV Detect
GPIO
Shutdown
Control
(see note 1)
GND
100kΩ⁽²⁾
Figure 10. Using TV-Detect Signal to Disable/Enable the OPA361-Q1
Disabling the OPA361-Q1 also disconnects the internal feedback resistors’ path to GND, and therefore there is
no current flowing from the logic supply through the pull-up resistor to GND if no video load is connected; this
helps to conserve battery life. The typical leakage when the output is pulled high and OPA361-Q1 is disabled is
only about 300pA.
The following functionality can be achieved by implementing TV-detection:
• Automatic video start by polling the video line periodically.
• Automatic video stop if the TV (or other equipment) is disconnected.
Proper implementation allows to significantly simplify the user interface.
For more information, see Application Report SBOA109, OPA361-Q1 and TV Detection, available for download
at www.ti.com.
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