OPA361

SBOS334A − SEPTEMBER 2005 − REVISED JANUARY 2006

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7

APPLICATIONS INFORMATION

The OPA361 video amplifier has been optimized to fit

seamlessly

with

Texas

Instruments’

OMAP242x

Multimedia processor. The following features have been

integrated to provide excellent video performance.

D Internal gain setting resistors (G = 5.2V/V) reduce

the number of external components needed in the

video circuit.

D Integration of the 500Ω video encoder load resistor

and 4k

Ω RSET resistor used by the OMAP242x

helps minimize the number of external components

and also ensures excellent ratio and temperature

tracking. This feature helps to keep the overall gain

accurate and stable over temperature.

D TV-detection support in connection with an

OMAP242x multimedia processor. This feature

helps to automate start/stop operation of the TV-out

function and minimizes power consumption.

D A 2-pole filter is incorporated for DAC signal

reconstruction.

D The OPA361 employs an internal level shift circuit

that avoids sync pulse clipping and allows

DC-coupled output.

D A shutdown feature reduces quiescent current to

less than 1.5

µA—crucial for portable applications

Although OPA361 is optimized for the OMAP242x

processor, it is also suitable to interface with any digital

media processor that outputs a video signal on the order

of 0.4VPP to 0.5VPP.

Figure 1 shows a typical application drawing with the

OMAP242x

processor and the TWL92230 Energy

Management Chip.

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 an interrupt.

OMAP2420

OPA361

TWL92230

500

Ω

Regulator V

AUX

2.8V

10mV

R

SET

+In

Out

V+

GND

Enable

Figure 1. Typical Application using the OMAP242x and the TWL92230