Features

Outstanding video performance

Internal gain: 5.2V/V

Support TV detection

Compatible with OMAP242X and Davinci processor

#8226 ; 2 Extreme Reconstruction Filter

The input range includes ground

DC coupling input

[ [ [ 123]

Integrated level converter

DC coupling output (1)

no output capacitors

Rail -to -track output

Static current: low

Turn off current: 1.5 A Single Power Source: 2.5V to 3.3V

SC70-6 Packaging: 2.0mm x 2.1mm

conforms to ROHS

(1), internal circuits to avoid output saturation, even if the 0V synchronization prompt level of the 0V of the video signal is entered.

Application

Photo mobile phone

Instructions

OPA361 high -speed amplifier is optimized for 3V portable video applications optimized Essence It is an OMAP2420 and Da Vinci processor or other applications with 0.5VPP video output that compatible with video encoders embedded in Texas instruments. The input common modular range includes GND, which allows video DAC (digital modular converters) DC to OPA361. The TV detection function greatly simplifies the end user interface by promoting the automatic start/stop of video transmission.

Output swing in the ground 5mv and 250mv to V+range, and the standard back -end video load (150 ). Internal level offset circuits prevent output and 0V input saturation, thereby preventing synchronous pulse waves in ordinary video circuits. Therefore, OPA361 is very suitable for DC coupling of video load.

OPA361 Set resistor (G u003d 5.2V/V) and a 2nd pole video DAC reconstruction filter through integrated internal gainOptimized space -sensitive applications.

In the shutdown mode, the static current dropped to lt; 1.5μA, significantly reduced power consumption and extend the battery life.

OPA361 has 2 mm x 2.1 mm SC70-6 miniature packaging.

Related low -voltage video amplifier

(1) Turn off when in normal operation; open when closed.

Typical features: vs u003d 2.8V

When TA u003d+25 ° C and RL u003d 150

Application information OPA361 video amplifier can OMAP242X multimedia processor seamlessly cooperate. Integrate the following functions to provide excellent video performance.

Internal gain setting resistance (G u003d 5.2V/V) reduces the number of external components required in the video circuit.

OMAP242X's 500 video encoder load resistor and 4K integration help to maximize the number of external components and ensure the excellent ratio And temperature tracking. This feature helps maintain the accuracy and temperature stability of the overall gain.

TV detection connected to the OMAP242X multimedia processor. This function helps to automatically start/stop the TV output function and minimize the power consumption.

2 polar filters for DAC signal reconstruction.

OPA361 uses an internal level conversion circuit to avoid synchronous pulse cutting waves and allow DC coupling output.

The shutdown function can reduce the static current below 1.5μA, which is essential for portable applications.

Although OPA361 optimizes OMAP242X processor, it is also suitable for interfaces with any digital media processor, which can output a video signal of 0.4VPP to 0.5VPP.

FIG. 1 shows a typical application diagram of the OMAP242X processor and TWL92230 energy management chip.

The working voltage

OPA361 completely specified from 2.5V to 3.3V within the temperature range from 40c to+125C. The typical feature is displayedParameters significantly changes with work voltage or temperature. Power insertion should be bypass with 100NF ceramic capacitors.

Input voltage

The input consensus range of the OPA361 series expands from GND to 0.55V of 3.3V power supply. The input range is limited by internal gain, maximum output swing capacity and power supply voltage.

Enter overvoltage protection

All OPA361 pins are used in the internal ESD protection diode connected to the power supply for static electricity protection. If the current is limited to 10mA, these diode will provide input -driven protection.

Enable/close

OPA361 has a closed function, which can disable output and reduce static current to less than 1.5 μA. This feature is particularly useful for portable video applications, because the device is rarely connected to TV (TV) or other video devices.

Enable logic input voltage refer to the OPA361 GND pin. The logic level used to enable the grain to enable the operational amplifier high. Logic level is compatible with 1.8V CMOS logic level. Effective logic high level is defined as 1.3V higher than GND. Low effective logic is defined as higher than GND less than 0.35V. If the pins are not connected, the internal pull circuit will be enabled to use the amplifier.

When the OPA361 is disabled, the internal circuit will also disconnect the internal gain setting feedback. This function supports TV detection functions. For more details, see the TV detection function part.

Internal 2 pole filter

OPA361 filter is a Sallen-Key topology with a 9MHz cut-off frequency. Figure 2 shows the detailed drawings of the filter component. This filter allows video signals to pass without any visible distortion, as shown in Figure 3 to 6. The sampling frequency of the video encoder embedded in the OMAP242X processor is usually 54MHz. At this frequency, the attenuation is usually 23dB, which effectively attenuates the sampling alias.

The internal 500 #8486 in the GND input converts the output current of the OMAP2420 internal video DAC to voltage. It is also part of the Sallen Key filter. Using an external resistor to adjust the input voltage range will also change the characteristics of the filter.

Video Performance

The color strip signal in FIG. 3 shows a good amplitude characteristics. Compared to the brightness signal, the color is not attenuated.

CCIR330/5 test mode requires one of the maximum dynamic range, so test OPA361 output voltage swing capacity. The range diagram shown in Figure 4 is taken with 2.8V power, and there is noShow any shear.

The multi -pulse test mode has different sine wave pulse segments, the frequency is as follows: 0.5MHz, 1MHz, 2MHz, 4MHz, 4.8MHz, 5.8MHz, 420mvpp. There is no decay even at the highest frequency, which indicates that the frequency response of OPA361 is very flat. As shown in Figure 5 and Figure 6, the top line shows a complete signal. The following line is a more detailed view of the last three sine waves.

CCIR17 test mode contains 2T and 20T pulses, as shown in Figure 6. 2T pulse is used to check pulse disturbance and reflection, and 20T pulse is used to check the amplitude and group delay between color and brightness. Neither pulse shows any distortion or group delayed pseudo -shadows.

Internal level conversion

Many common video DAC embedded in digital media processors, such as the new OMAP242X processor, at a single power supply (none Negative power) work. Generally, the minimum point of the synchronous pulse output by these videos is close to 0V. For 0V input, the output of the general single power supply amplifier is saturated under the voltage greater than 0V. This effect will intercept the same step pulse to reduce the integrity of the video signal. OPA361 uses an internal level conversion circuit to avoid limit. The input signal usually moves about 11 millivolves. This offset is within the OPA361 linear output voltage range under the standard 150 video load.

Output swing capacity

FIG. 7 shows the real output swing capacity of OPA361, which puts the tip of the synchronous pulse at the slightly negative voltage. Even if the output synchronization tip is 3mv, 75 the output of the series is not displayed without the cutting wave of the synchronous pulse.

TV detection function

The TV detection function of OPA361 cooperates with OMAP242X (or other processors) to detect whether the TV is connected to the video output of the device to the device Essence In order to detect TV loads, OPA361 will be briefly closed, and Ideally, during the first vertical synchronization pulse period. For detection, a simple pull -up resistor connected to the processor logic power supply is used at the output end of the OPA361. If the TV (or other video equipment) is connected, the voltage level will be pulled down; if there is no connection, the voltage level will be pulled up. The GPIO in the processor can be used to read this logic level and decide whether to connect to the video load. Figure 8 shows the range of the range when the TV is disconnected, and Figure 9 shows the range chart when connecting TV; the launch in the two pictures is a disabled pulse. Figure 10 shows the use of TV detection signals to disable or enable OPA361.

The disable OPA361 will also disconnect the grounding path of the internal feedback resistor. Therefore, if there is no video load connection, the logic power supply does not pass through the pulled resistor to the GND;Save battery life.When the output is raised and OPA361 is disabled, the typical leakage volume is only about 300Pa.

The following functions can be achieved through the implementation of TV detection:

*Start video through regular rotation video cables.

*If the TV (or other equipment) is disconnected, the video stops automatically.

Correct implementation can greatly simplify the user interface.