MT88700S DTMF Encoder Decoder

  1. Reference


Dual Tone Multiple Frequency technologies were introduced by Bell Labs to replace pulse-dialing in telephones. MT8870 is a DTMF Decoder module that generates a 4-bit digital code with respect to the DTMF audio signal. The MT8870 Decoder IC is integrated with an operational amplifier with user-adjustable Guard time. The embedded band-split filter uses switch capacitor techniques to distinguish and split low and high frequencies from the received signal. The module is provided with an audio jack to receive the DTMF signal generated.

MT8870-DTMF-Decoder-Module.webp MT8870-DTMF-Decoder-Module-components.webp MT8870-DTMF-Decoder-Module-pinout-diagram.webp

Number Pin Name Function
1 IN+ Non-Inverting input pin
2 IN- Inverting input pin
3 GS Gain Select pin
4 VRef Output Reference Voltage
5 INH Input Inhibit pin
6 PWDN Input Power Down pin
7 OSC1 Clock input pin
8 OSC2 Clock output pin
9 VSS Ground pin
10 TOE Decoder Output Enable pin
11-14 Q1-Q4 Decoder Output pins
15 StD Output Delayed Steering pin
16 ESt Output Early Steering pin
17 St/GT Input steering/Output Guard Time pin
18 VDD Positive Power Supply pin



Glenn Lyons VK4PK
Ver:gnl20220104 - pre published v0.9