OPA360 datasheet(6/24 Pages) TI1

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OPA360

SB0S294E − DECEMBER 2003 − REVISED SEPTEMBER 2006

www.ti.com

APPLICATIONS INFORMATION

The OPA360 video amplifier has been optimized for

portable video applications:

D Internal gain setting resistors (G = 2) reduce the

number of external components needed in the

video circuit.

D A 2-pole filter is incorporated for DAC signal

reconstruction.

D The sag correction function reduces the size of the

output coupling capacitors without compromising

performance.

D OPA360 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 5

µA—crucial for portable applications

such as digital still cameras (DSCs) and camera

phones.

The OPA360 interfaces to digital media processors

(DM320/270, DSC25). It has been optimized for the

requirements

digital

still

cameras

and

cell

phone/camera designs.

OPERATING VOLTAGE

The OPA360 is fully specified from 2.7V to 3.3V over a

temperature range of −40

°C to +85°C. Parameters that

vary significantly with operating voltages or temperature

are shown in the Typical Characteristics.

Power-supply pins should be bypassed with 100nF

ceramic capacitors.

INPUT VOLTAGE

The input common-mode range of the OPA360 series

extends from GND to (V+) − 1.5V. Because of the internal

gain, the input voltage range necessary for an output in the

valid range will be limited.

INPUT OVERVOLTAGE PROTECTION

All OPA360 pins are static-protected with internal ESD

protection diodes connected to the supplies. These diodes

will provide input overdrive protection if the current is

externally limited to 10mA

ENABLE/SHUTDOWN

The OPA360 has a shutdown feature that disables the

output and reduces the quiescent current to less than 5

µA.

This feature is especially useful for portable video

applications such as digital still cameras and camera

phones, where the equipment is infrequently connected to

a TV or other video device.

The Enable logic input voltage is referenced to the

OPA360 GND pin. A logic level HIGH applied to the enable

pin enables the op amp. A valid logic HIGH is defined as

≥ 1.6V above GND. A valid logic LOW is defined as ≤ 0.8V

above GND. If the Enable pin is not connected, internal

pull-up

circuitry will

enable the amplifier. Enable pin

voltage levels are tested for a valid logic HIGH threshold

of 1.6V minimum and a valid logic LOW threshold of 0.8V

maximum.

INTERNAL 2-POLE FILTER

The OPA360 filter is a Sallen-Key topology with a 9MHz

cutoff frequency. This allows the video signals to pass

without any visible distortion, as shown in Figure 3 through

Figure 5. The video DACs embedded in TI’s Digital Media

Processors over-sample at 27MHz. At this frequency, the

attenuation is typically 21dB, which effectively attenuates

the sampling aliases.

The filter characteristics vary somewhat with signal source

impedance. A source impedance greater than 500

Ω can

degrade filter performance. With current-output video

DACs, a resistor to GND is often used to create a voltage

output which is then applied to the OPA360 input (see

Figure 1). TI’s Digital Media Processors, such as the

DM270 or DM320, typically use a 200

Ω resistor to GND to

convert the current output signal. This 200

Ω source

impedance does not degrade video performance.

12pF

650

Ω

NOTE: (1) Optional.

325

Ω

1.4k

Ω

1.1k

Ω

528

Ω

845

Ω

SAG

OPA360

(1)

()

10pF

Ω

Television

Figure 1. Filter Structure of OPA360

OPA360 Datasheet(PDF) 6 Page - Texas Instruments

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