TMC2242C Datasheet, PDF (1/16 Pages) Fairchild Semiconductor – Digital Half-Band Interpolating/Decimating Filter 12-bit In/16-bit Out, 60 MHz

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TMC2242C
Digital Half-Band Interpolating/Decimating Filter
12-bit In/16-bit Out, 60 MHz
Features
• Pin-compatible upgrade of TMC2242B
• User-selectable interpolate d.c. gain, 0 dB or -6 dB
• True unity d.c. gain in all “0 db” modes
• 40 MSPS performance in equal-rate filter modes
• 40 and 60 MSPS speed grades in all other modes
• User-selectable 2:1 decimation, 1:2 interpolation, and
equal-rate filter modes, plus unfiltered bypass/delay mode
• Defeatable πx/sin(πx) compensation filter
• Passband ripple <0.014 dB
• Stopband rejection >56 dB
• Dedicated 12-bit two’s complement or unsigned input bus
• 16-bit two’s complement or unsigned output bus with
user-selectable rounding to 8 to 16 effective bits
• Programmable limiter prevents overflow or clips to
CCIR601 levels
• New double-latency modes match Y channel data flow to
slower-sampled CB and CR data flows
• New dual-channel interpolation and decimation for
YUV422
Applications
• Digital-to-Analog Converter Prefiltering with optional
x/sinx correction
• 1:2 interpolation
• Analog-to-Digital Converter Postfiltering
• 2:1 decimation
• Low-ripple low-pass (0 to 0.2 fs) filter
Block Diagram
Description
The TMC2242C, a linear-phase low-pass half-band digital
filter with fixed coefficients, can be used to halve or double
the sampling rate of a digital signal. When used as a decimat-
ing post-filter with a double-speed oversampling A/D con-
verter, it greatly reduces the cost and complexity of the
required analog antialiasing pre-filters. When used as an
interpolating pre-filter with a double-speed oversampling
D/A converter, it greatly reduces the complexity and cost of
the necessary analog post-filter, particularly when its x/sin(x)
correction filter is engaged.
The TMC2242C user selects the mode of operation (deci-
mate, interpolate, equal-rate, bypass, x/sin(x))and rounding.
The part can accept 12-bit two’s complement or unsigned
data at up to 60 MHz and can output saturated two’s comple-
ment or offset binary data rounded to from 8 to 16 bits.
Within the speed grade I/O limit, the output sample rate may
be 1/2, 1, or 2 times the input sample rate. Two-channel
modes permit it to interpolate or to decimate two multi-
plexed data streams (such as video CB and CR) jointly.
The filter response is flat to within ±0.014 dB up to 0.21fs
(e.g. 5.75MHz at a 27MHz clock rate), with stopband attenu-
ation greater than 56dB above 0.29fs. Symmetric-coefficient
filters such as the TMC2242C always have linear phase
response. Half-band response is -6 dB.
Fabricated on an advanced submicron CMOS process, the
TMC2242C is available in a 44-lead PLCC package. Perfor-
mance is guaranteed from 0 to 70°C and over a power supply
range of 4.75 to 5.25V.
SI11-0
ZERO
INSERT
FIR
FILT
X/SIN(X)
FILTER
ROUND
LIMIT
DECIMATE
SO15-0
SO3-0
CONTROL
DEC INT SYNC TCO RND OE
65-2242C-01
Rev. 1.0.0