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MT8870DS / MT8870 SOP-18 DTMF Tone Decoder IC (5pcs)
MT8870DS / MT8870 SOP-18 DTMF Tone Decoder IC (5pcs)
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MT8870DS / MT8870 — SOP-18 DTMF Tone Decoder IC
The MT8870DS is a complete DTMF (Dual-Tone Multi-Frequency) receiver IC in SOP-18 SMD package. It decodes all 16 standard DTMF tones (0–9, A–D, *, #) and outputs a 4-bit binary code plus a strobe signal — making it ideal for telephone remote control, tone-based command systems, and audio frequency detection. This listing provides 5 pieces — new and original.
Key Specifications
| Parameter | Value |
|---|---|
| Part Numbers | MT8870DS / MT8870D / MT8870 |
| Package | SOP-18 (SMD) |
| DTMF Tones Decoded | All 16 (0–9, A–D, *, #) |
| Output | 4-bit binary (Q1–Q4) + StD strobe |
| Crystal Frequency | 3.579545MHz (standard NTSC crystal) |
| Supply Voltage (Vdd) | 2.5V – 5.5V |
| Input Sensitivity | -25dBm (typ.) |
| Guard Time | 40ms (min. tone duration) |
| Operating Temperature | -40°C to +85°C |
| Quantity | 5 PCS |
DTMF Output Code Table
| Key | Q4 | Q3 | Q2 | Q1 |
|---|---|---|---|---|
| 1 | 0 | 0 | 0 | 1 |
| 2 | 0 | 0 | 1 | 0 |
| 3 | 0 | 0 | 1 | 1 |
| * | 1 | 0 | 1 | 0 |
| 0 | 1 | 0 | 1 | 1 |
| # | 1 | 1 | 0 | 0 |
| A–D | 1 | 1 | 0–1 | 0–1 |
Why Choose MT8870DS?
- ✅ Complete DTMF receiver — bandpass filter, decoder, and latch in one IC
- ✅ 4-bit parallel output — directly readable by Arduino/ESP32 GPIO or 74HC595
- ✅ StD strobe output — interrupt-driven reading, no polling needed
- ✅ Standard 3.58MHz crystal — uses common NTSC TV crystal, easy to source
- ✅ 2.5–5.5V operation — compatible with 3.3V and 5V systems
Compatible With / Works With
- Arduino UNO/Nano (read Q1–Q4 on digital pins, StD as interrupt)
- ESP32 / ESP8266 (3.3V compatible, read via GPIO)
- Telephone line interface circuits (600Ω transformer coupling)
- 3.579545MHz crystal (standard NTSC, widely available)
- MT8880 (DTMF transceiver, transmit + receive)
Typical Applications
- Telephone Remote Control — control Arduino relay via DTMF tones from any phone
- DTMF Decoder Module — decode keypad tones for access control systems
- Tone-Based Command System — audio frequency command decoder for radio remote control
- Caller ID / IVR System — detect DTMF digits in telephone IVR applications
- Security System — DTMF-based alarm arm/disarm via telephone
FAQ
Q: What crystal does MT8870DS need?
A: A standard 3.579545MHz crystal (NTSC color burst frequency). This is the same crystal used in old NTSC TV sets and is widely available. Connect between pins OSC1 and OSC2 with 22pF load capacitors.
Q: How do I connect MT8870DS to Arduino?
A: Connect Q1–Q4 to Arduino digital pins (D2–D5), StD to an interrupt pin (D2 or D3). When StD goes HIGH, read Q1–Q4 to get the 4-bit DTMF code. Use attachInterrupt() for reliable detection.
Q: Can MT8870DS decode tones from a smartphone?
A: Yes. Play DTMF tones through a speaker near the MT8870DS input, or connect via audio jack. The IC's input sensitivity (-25dBm) is sufficient for audio-level signals from smartphones.
Package Contents
- 5× MT8870DS / MT8870 SOP-18 DTMF Tone Decoder IC
