OPA360 Datasheet, PDF (6/15 Pages) Burr-Brown (TI) – 3V Video Amplifier with 6dB Gain and Filter in SC70

OPA360
SB0S294C − DECEMBER 2003 − REVISED JULY 2004
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 5µA—crucial for portable applications
such as digital still cameras and camera phones.
The OPA360 interfaces to digital media processors
(DM320/270, DSC25). It has been optimized for the
requirements of 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.
www.ti.com
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 5µA.
This feature is especially useful for portable video
applications such as digital still cameras (DSC) 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 500Ω 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 200Ω resistor to GND to
convert the current output signal. This 200Ω source
impedance does not degrade video performance.
10pF
()
R
1.1kΩ 1.4kΩ
(1)
12pF
NOTE: (1) Optional.
V_O
75Ω
325Ω
650Ω
845Ω
528Ω
SAG
OPA360
Figure 1. Filter Structure of OPA360
6
Television
75Ω