The MT8870D/MT8870D-1 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; the decoder uses digital counting techniques to detect and decode all 16 DTMF tonepairs into a 4-bit code. External component count is minimized by on chip provision of a differential input amplifier, clock oscillator and latched three-state bus interface.Separation of the low-group and high group tones is achieved by applying the DTMF signal to the inputs of twosixth-order switched capacitor bandpass filters, the bandwidths of which correspond to the low and high group
frequencies. The filter section also incorporates notches at 350 and 440 Hz for exceptional dial tone rejection (see
Figure 3).

The MT8870 module is a low power device DTMF decoder chip. It is a complete DTMF receiver integrating both the band-split filter and digital decoding functions. This module is suitable for modem interfaces, mobile radios and  other DTMF related applications.

FEATURES of MT8870 DTMF Receiver

• Recommended Dc Power Supply:5.5V
• RecommendedOperating Temperature:-40ºC to +85ºC
• Power Dissipation:500 mW
• Maximum Operating Supply Current:9mA
• • Complete DTMF Receiver
  • Low power consumption
  • Internal gain setting amplifier
  • Adjustable guard time
  • Central office quality
  • Power-down mode
  • Inhibit mode
  • Backward compatible with MT8870C/MT8870C-1
• 
• Complete DTMF Receiver
• Low power consumption
• Internal gain setting amplifier
• Adjustable guard time
• Central office quality
• Power-down mode
• Inhibit mode
• Backward compatible with MT8870C/MT8870C-1
• Receiver system for British Telecom (BT) or CEPT Spec (MT8870D-1)
• Paging systems
• Repeater systems/mobile radio
• Credit card systems
• Remote control
• Personal computers
• Telephone answering machine

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