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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

• 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

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-

The filter response is flat to within

(e.g. 5.75MHz at a 27MHz clock rate), with stopband attenu-

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.

Block Diagram

TCO RND

OE

DEC

INT

SYNC

ROUND

LIMIT

X/SIN(X)

FILTER

FIR

FILT

ZERO

INSERT

DECIMATE

CONTROL

65-2242C-01

TMC2242C

Digital Half-Band Interpolating/Decimating Filter

12-bit In/16-bit Out, 60 MHz

Rev. 1.0.0