HM9270DM Ver la hoja de datos (PDF) - ELAN Microelectronics

Número de pieza

componentes Descripción

Fabricante

HM9270DM

DTMF RECEIVER

ELAN Microelectronics 

HM 9270C/D

DTMF RECEIVER

5V

100 NF

Vin

100 KΩ

5V

100 KΩ

3.58

MHz

HM9270D

IN+

IN

GS

VREF

INH

PWDN

OSC1

OSC2

VSS

0.1µf

VDD

St/GT

ESt

StD

Q4

Q3

Q2

Q1

TOE

100 NF

300 KΩ

FIGURE 3. SINGLE ENDED INPUT CONFIGURATION

The HM9270C/D monolithic DTMF receiver offers small size, low power consumption and high performance. Its

architecture consists of a bandsplit filter section, which separates the high and low tones of receiver pair, followed by

a digital counting section which verifies the frequency and duration of the received tones before passing the

corresponding code to the output bus.

FILTER SECTION

Separation of the low-group and high-group tones is achieved by applying the dual tone signal to the inputs of two

filters a sixth order for the high group and an eighth order for the low group. The bandwidths of which correspond

to the bands enclosing the low-group and high-group tones (see Fig. 4). The filter section also in corporates

notches at 350Hz and 440 Hz for exceptional dial-tone rejection. Each filter output is followed by a second-order

switched-capacitor section which smooths the signals prior to limiting. Limiting is performed by high-gain com-

parators which are provided with hysteresis to prevent detection of unwanted low-level signals and noise; the

outputs of the comparators provide full-rail logic swings at the frequencies of the incoming tones.

Flow Fhigh KEY TOE Q4 Q3 Q2 Q1

697 1209 1 H 0 0 0 1

Decoder Section

697 1336 2 H 0 0 1 0

The decoder used digital counting techniques to

697 1477 3 H 0 0 1 1

determine the frequencies of the limited tones and to

770 1209 4 H 0 1 0 0

verify that they correspond to standard DTMF

770 1336 5 H 0 1 0 1

frequencies. A complex averaging algorithm(protects) 770 1477 6 H 0 1 1 0

against tone simulation by extraneous signals, such as 852 1209 7 H 0 1 1 1

voice, while providing tolerance to smalll frequency

852 1336 8 H 1 0 0 0

deviations and variations. This averaging algorithm has 852 1477 9 H 1 0 0 1

been developed to ensure an optimum combination of 941 1336 0 H 1 0 1 0

immunity to "talk-off" and tolerance to the presence of 941 1209 * H 1 0 1 1

interfering signals ("third tones") and noise. When the 941 1477 # H 1 1 0 0

detector recognizes the simultaneous presence of two

697 1633 A H 1 1 0 1

valid tones (referred to as "signal condition" in some

770 1633 B H 1 1 1 0

industry specifications), it raises the "early steering"

852 1633 C H 1 1 1 1

flag (ESt). Any subsequent loss of signal condition will 941 1633 D H 0 0 0 0

cause ESt to fall.

-

- ANY L

ZZZ Z

L = LOGIC LOW , H = LOGIC HIGH, Z = HIGH

IMPEDANCE

FIGURE 4. LOGIC TABLE

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