OPA361-Q1 Datasheet, PDF (8/18 Pages) Texas Instruments – 3V Video Amplifier with Internal Gain and Filter in SC70

OPA361-Q1
SBOS552 – MARCH 2011
www.ti.com
OPERATING VOLTAGE
The OPA361-Q1 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 OPA361-Q1 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 OPA361-Q1 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 OPA361-Q1 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 OPA361-Q1 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 > 1.3V above GND. A valid logic LOW is defined as < 0.35V above GND. If the Enable pin is not
connected, internal pull-up circuitry will enable the amplifier.
When disabling the OPA361-Q1, internal circuitry also disconnects the internal gain setting feedback. This
feature is in support of the TV-detection function. See the TV-Detect Function section for more detailed
information.
INTERNAL 2-POLE FILTER
The OPA361-Q1 filter is a Sallen-Key topology with a 9MHz cutoff frequency. Figure 2 shows a detailed drawing
of the filter components. This filter allows video signals to pass without any visible distortion, as shown in
Figure 3 through Figure 6. The video encoder embedded in the OMAP242x processor typically samples at
54MHz. At this frequency, the attenuation is typically 23dB, which effectively attenuates the sampling aliases.
The internal 500Ω resistor on the input to GND converts the output current of the OMAP2420 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
will also alter the filter characteristics.
()
OPA361
2.2kΩ
2.2kΩ
500Ω
3.6pF
12.5pF
4.22kΩ
V_O 75Ω
Television
75Ω
1kΩ
Figure 2. Filter Structure of the OPA361-Q1
8
Submit Documentation Feedback
Product Folder Link(s) :OPA361-Q1
Copyright © 2011, Texas Instruments Incorporated