OPA362 Datasheet, PDF (9/18 Pages) Texas Instruments – 3V VIDEO AMPLIFIER with Internal Gain and Filter in SC70

OPA362
www.ti.com ........................................................................................................................................................................................ SBOS480 – SEPTEMBER 2009
Operating Voltage
The OPA362 is fully specified from 2.5V to 3.3V over
a temperature range of –40°C to +125°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 OPA362 series
extends from GND to 0.55V on a 3.3V supply. The
input range is limited by the internal gain in
conjunction with the maximum output swing capability
and the power-supply voltage.
Input Overvoltage Protection
All OPA362 pins are static-protected with internal
ESD protection diodes connected to the supplies.
These diodes provide input overdrive protection if the
current is externally limited to 10mA.
Enable/Shutdown
The OPA362 has a shutdown feature that disables
the output and reduces the quiescent current to less
than 1.5μA. This feature is especially useful for
portable video applications, where the device is
infrequently connected to a television (TV) or other
video device.
The Enable logic input voltage is referenced to the
OPA362 GND pin. A logic level high applied to the
Enable pin enables the op amp. The logic levels are
compatible with 1.8V CMOS logic levels. A valid logic
high is defined as greater than 1.3V above GND. A
valid logic low is defined as less than 0.5V above
GND. If the Enable pin is not connected, internal
pull-up circuitry enables the amplifier.
When disabling the OPA362, internal circuitry also
disconnects the internal gain setting feedback. This
feature supports the TV-detection function; see the
TV-Detect Function section for more detailed
information.
Internal Two-Pole Filter
The OPA362 filter is a Sallen-Key topology with an
8.5MHz cutoff frequency. Figure 19 shows a detailed
drawing of the filter components. This filter allows
video signals to pass without any visible distortion, as
shown in Figure 20 through Figure 23. The video
encoder embedded in the OMAP343x processor
typically samples at 54MHz. At this frequency, the
attenuation is typically 23dB, which effectively
attenuates the sampling aliases.
The internal 872Ω resistor on the input to GND
converts the output current of the OMAP3430 internal
video DAC into a voltage. It is also part of the
Sallen-Key filter. Using an external resistor to adjust
the input voltage range also changes the filter
characteristics.
()
OPA362
1838W
2.5kW
872W
3.6pF
12.5pF
4.22kW
1kW
V_O 75W
Television
75W
Figure 19. OPA362 Filter Structure
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): OPA362
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