HTCSEMI HT8870ARWZ

Microcircuit is purposed for receiving and decoding of tone pairs from tone-pulse dialers in frequency dialing mode. Microcircuit can be used in telecom systems, consumer electronic devices. The IC detects all sixteen standard DTMF signals and converts them into corresponding digital code. Input of the IC is composed of input operational amplifier and three filters - pre-filter, filter of low- frequency group, filter of high-frequency group. The signal received at the input of IC, is supplied to inverting input of operational amplifier VN, which gain ratio is set by external components (at typical application gain equals 1). From the operational amplifier output signal is supplied to pre-filter. Preliminary filter is a band rejection filter and is designed to suppress frequencies to 440 Hz. After filtering DTMF signal is simultaneously supplied to filter high and low groups. Filter low-frequency group - band filter that passes only the low tone group. Filter high-frequency group - band-pass filter which passes only the high-tone group. Allocated signals are amplified and passed through to the frequency detector. Frequency detector determines the frequency of signals received from each filter, code detector converts this information in to 4-bit code, which goes to the latch output. Output latches are designed for the reception, transmission and storage of 4-bit code. When a high-level signal at the output DV, the tone code can be read from D0 - D3 pins. Control unit allows controlling intertone pause duration and the duration of the input DTMF signal for the given values of R3 and C4.

• Supply voltage U_CC = (2.5 - 5.5) V
• No external filter is required
• Low-cost 3.58 MHz resonator is used
• 1633 Hz signal detection inhibit
• 3 state data output
• Power down mode
• Temperature range -20 … +75 ℃
• Permissible electrostatic discharge potential 500V

• telecom systems
• consumer electronic devices