MT8870DS DTMF Receiver SMD IC

MT8870DS DTMF Receiver SMD IC

The MT8870DS is a complete, monolithic Dual-Tone Multi-Frequency (DTMF) receiver integrated circuit. Its primary role is to accurately detect and decode the standard 16 DTMF tone pairs, which are the combinations of high and low-frequency tones used in telephone signaling, into a corresponding 4-bit binary code. This IC elegantly integrates both the essential bandsplit filter and the digital decoder functions onto a single chip, providing a highly compact solution for telephony and control systems.

The device employs a sophisticated architecture for reliable signal interpretation. The incoming DTMF signal is first processed by a filter section that uses switched capacitor techniques to cleanly separate the low and high-group tones. This section also incorporates notches to reject common dial tones, preventing false triggering. The separated tones are then passed to a digital decoder that uses a complex averaging algorithm to verify the frequencies and their duration, ensuring immunity to voice simulation and noise.

Designed for easy integration into larger systems, the MT8870DS minimizes external component requirements by including an on-chip differential input amplifier, clock oscillator, and a latched three-state bus interface. It offers designer flexibility through features like an adjustable guard time for validating signal duration, a power-down mode for energy savings, and an inhibit mode to ignore specific tone codes. The three-state outputs allow for direct connection to a microprocessor data bus.

Features:

• Complete DTMF Receiver Integration.
• Low Power Consumption.
• Internal Gain Setting Amplifier.
• Adjustable Guard Time.
• Central Office Quality.
• Power-Down Mode (PWDN).
• Inhibit Mode (INH).
• Backward Compatible with MT8870C/8870C-1.
• Latched Three-State Bus Interface.

Specifications: