max9588auat Maxim Integrated Products, Inc., max9588auat Datasheet - Page 9

• Manufacturer Part Number: max9588auat
• Description: Max9586, Max9587, Max9588, Max9589 Single, Dual, Triple, And Quad Standard-definition Video Filter Amplifiers With Ac-coupled Input Buffers
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9586–MAX9589 filter and amplify the video
DAC output in applications such as set-top boxes and
televisions. These devices consist of input clamps,
input bias circuits, lowpass filters, and gain of 2V/V out-
put amplifiers capable of driving a standard 150Ω
video load to ground.
The input stages of the MAX9586–MAX9589 are either
sync-tip clamps or bias circuits. Sync-tip clamps accept
AC-coupled CVBS or luma video signals with sync puls-
es. The sync-tip voltage is internally set to 300mV. Bias
circuit inputs accept AC-coupled chroma, a subcarrier
modulated with the color information. The bias voltage
of the bias circuits is approximately 500mV.
The filter passband (±1dB) is typically 8.5MHz, which
makes the device suitable for standard-definition video
signals from all sources (e.g., broadcast and DVD).
Broadcast video signals are channel limited: NTSC sig-
nals have 4.2MHz bandwidth and PAL signals have
5MHz bandwidth. Video signals from a DVD player,
however, are not channel limited, so the bandwidth of
DVD video signals can approach the Nyquist limit of
6.75MHz. (Recommendation ITU-R BT.601-5 specifies
13.5MHz as the sampling rate for standard-definition
video). Therefore, the maximum bandwidth of the signal
is 6.75MHz. To ease the filtering requirements, most
modern video systems oversample by two times, clock-
ing the video current DAC at 27MHz.
Video Filter Amplifiers with AC-Coupled Input Buffers
Single, Dual, Triple, and Quad Standard-Definition
_______________________________________________________________________________________
Detailed Description
Video Filter
Inputs
The video output amplifiers can both source and sink
load current, allowing output loads to be DC- or AC-
coupled. The amplifier output stage needs approxi-
mately 300mV of headroom from either supply rail. The
devices have an internal level-shift circuit that positions
the sync tip at approximately 300mV at the output.
If the supply voltage is greater than 3.135V (5% below
a 3.3V supply), each amplifier can drive two DC-cou-
pled video loads to ground. If the supply is less than
3.135V, each amplifier can drive only one DC-coupled
or AC-coupled video load.
The MAX9586 draws less than 1µA supply current
when SHDN is low. In shutdown mode, the amplifier
output becomes high impedance.
The outputs can be AC-coupled since the output stage
can source and sink current as shown in Figure 3.
Coupling capacitors should be 220µF or greater to
keep the highpass filter, formed by the 150Ω equivalent
resistance of the video transmission line, to a corner
frequency of 4.8Hz or below. The frame rate of PAL
systems is 25Hz, and the frame rate of NTSC systems
is 30Hz. The corner frequency should be well below the
frame rate.
The MAX9586–MAX9589 operate from a single-supply
voltage down to 2.7V, allowing for low-power operation.
Bypass V
external components as close as possible to the device.
Power-Supply Bypassing and Ground
DD
to GND with a 0.1µF capacitor. Place all
Applications Information
AC-Coupling the Outputs
Shutdown (MAX9586)
Outputs
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