Datasheet

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SBOS334A − SEPTEMBER 2005 − REVISED JANUARY 2006
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11
Video
DAC
1.8V DAC 0.5V V
REF
2−Pole
Filter
Shutdown
Control
+
75
Ω
1.8V
Pull−Up
10k
Ω
100k
Ω
(2)
4k
Ω
(see note 1)
G = 5.2V/V
75
Ω
TV Detect
TV Detect
GPIO
(3)
GPIO
(1) Closed when enabled during normal operation; open when shut down.
(2) Protects GPIO against overvoltage conditions during active video transmission.
(3) GPIO must be able to generate interrupt.
OMAP2420
OPA361
TWL92230
500
Ω
Regulator V
AUX
2.5V or 2.8V
10mV
R
SET
+In
Out
V+
GND
Enable
Figure 10. Using TV-Detect Signal to Disable/Enable the OPA361
Disabling the OPA361 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 is disabled is only about 300pA.
The following functionality can be achieved by
implementing TV-detection:
D Automatic video start by polling the video line
periodically.
D 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 and TV Detection, available for download at
www.ti.com.