DTMF RECEIVER

HM 9270C/D

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General Description

The HM 9270C/D is a complete DTMF receiver integrating both the bandsplit filter and digital decoder

functions. The filter section uses switched capacitor techniques for high- and low-group filters and dial-tone

rejection. Digital counting techniques are employed in the decoder to detect and decode all 16 DTMF tone-

pairs into a 4-bit code. External component count is minimized by on-chip provision of a differential input

amplifier, clock-oscillator and latched 3-state bus interface.

Features

• Complete receiver in an 18-pin package.

• Excellent performance.

• CMOS, single 5 volt operation.

• Minimum board area.

• Central office quality.

• Low power consumption.

• Power-Down mode (HM9270D only).

• Inhibit-mode (HM9270D only).

Pin Configurations

* Connect to V

SS

HM9270C

IN+

IN

GS

IC*

IC*

OSC1

OSC2

ESt

StD

Q4

Q3

Q2

Q1

TOE

St/GT

1

2

3

4

5

6

7

8

9

18

17

16

15

14

13

12

11

10

HM9270D

IN+

IN

GS

INH

PWDN

OSC1

OSC2

ESt

StD

Q4

Q3

Q2

Q1

TOE

St/GT

1

2

3

4

5

6

7

8

9

18

17

16

15

14

13

12

11

10