75T204 5V Low-Power Subscriber DTMF Receiver April 2000 DESCRIPTION FEATURES The 75T204 is a complete Dual-Tone Multifrequency (DTMF) receiver that detects 16 standard digits. No front-end pre-filtering is needed. The only external components required are an inexpensive 3.58-MHz television “colorburst” crystal for frequency reference and a bias resistor. An Alternate Time Base (ATB) is provided to permit operation of up to 10 75T204's from a single crystal. The 75T204 employs state-ofthe-art "switched-capacitor" filter technology, resulting in approximately 40 poles of filtering, and digital circuitry on the same CMOS chip. The analog input signal is pre-processed by 60-Hz reject and band split filters and then zero-cross detected to provide AGC. Eight bandpass filters detect the individual tones. Digital processing is used to measure the tone and pause durations • Intended for applications with less requirements than the 75T202/75T203 • 14-pin plastic DIP or 16-pin SO package for high system density • NO front-end band-splitting filters required • Single low-tolerance 5-volt supply • Detects all 16 standard DTMF digits. • Uses an inexpensive 3.579545-MHz crystal • Excellent speech immunity • Output in 4-bit hexadecimal code • Three-state outputs for microprocessor interface (continued) BLOCK DIAGRAM BANDPASS FILTERS 697 PRE-PROCESSOR ANALOG 60 Hz REJECT PREEMP BAND SPLIT FILTERS ZERO CROSSING DETECTORS BS1 AMPLITUDE DETECTORS 770 852 941 BS2 TIMING CIRCUITRY 1209 1336 ATB DV 1477 DV XEN XIN DATA STROBE 1633 ÷8 CLOCK GENERATOR CHIP CLOCKS D1 1Mz XOUT D2 OUTPUT DECODER OUTPUT REGISTER D4 POWER REGULATOR VOLTAGE REF D8 DATA CLEAR EN VP GND 75T204 5V Low-Power Subscriber DTMF Receiver DESCRIPTION (continued) DV and to provide output timing and decoding. The outputs interface directly to standard CMOS circuitry and are three-state enabled to facilitate bus-oriented architectures. DV signals a detection by going high after a valid tone pair is sensed and decoded at the output pins D1, D2, D4, and D8. DV remains high until a valid pause occurs. ANALOG IN N/C PINS This pin accepts the analog input. It is internally biased so that the input signal may be AC coupled. The input may be DC coupled as long as it does not exceed the positive supply. Proper input coupling is illustrated in Figure 1. These pins have no internal connection and may be left floating. Output Code The 75T204 is designed to accept sinusoidal input wave forms but will operate satisfactorily with any input that has the correct fundamental frequency with harmonics less then -20 dB below the fundamental. CRYSTAL OSCILLATOR The 75T204 contains an onboard inverter with sufficient gain to provide oscillation when connected to a low-cost television “colorburst” crystal. The crystal oscillator is enabled by tying XEN high. The crystal is connected between XIN and XOUT. A 1 Mz 10% resistor is also connected between these pins. In this mode, ATB is a clock frequency output. Other 75T204’s (or 75T202's) may use the same frequency reference by tying their ATB pins to the ATB of a crystal connected device. XIN and XEN of the auxiliary devices must then be tied high and low respectively. Ten devices may run off a single crystal-connected 75T204 (or 75T202) as shown in Figure 2. OUTPUTS D1, D2, D4, D8 and EN Outputs D1, D2, D4, D8 are CMOS push-pull when enabled (EN high) and open circuited (high impedance) when disabled by pulling EN low. These digital outputs provide the hexadecimal code corresponding to the detected digit. The digital outputs become valid after a tone pair has been detected (DV is high) and they are then cleared when a valid pause is timed. The hexadecimal codes are described in Table 1. Digit D8 D4 D2 D1 1 0 0 0 1 2 0 0 1 0 3 0 0 1 1 4 0 1 0 0 5 0 1 0 1 6 0 1 1 0 7 0 1 1 1 8 1 0 0 0 9 1 0 0 1 0 1 0 1 0 * 1 0 1 1 # 1 1 0 0 A 1 1 0 1 B 1 1 1 0 C 1 1 1 1 D 0 0 0 0 TABLE 1: Output Codes 2 75T204 5V Low-Power Subscriber DTMF Receiver VP VP 7 Analog In (On Chip) VIN > VP (On Chip) VIN < VP 0.01 µF 7 10 pF Analog In 10 pF >100 kΩ >100 kΩ GND GND FIGURE 1: Input Coupling VP XIN XOUT 10 9 75T204 ATB 6 XEN 11 XIN Connected to VP 10 75T204 6 XEN 11 Up to 10 Devices FIGURE 2: Crystal Connections 3 75T204 5V Low-Power Subscriber DTMF Receiver DTMF DIALING MATRIX See Figure 3. Please note that column 3 is for special applications and is not normally used in telephone dialing. Col 0 Col 1 Col 2 Col 3 Row 0 1 2 3 A Row 1 4 5 6 B Row 2 7 8 9 C Row 3 * 0 # D FIGURE 3: DTMF Dialing Matrix Analog Input ton toff Tone burst 1 Pause tR tD D1, D2, D4, D8 tS tH DV FIGURE 4: Timing Diagram 4 Tone burst 2 75T204 5V Low-Power Subscriber DTMF Receiver DETECTION FREQUENCY Low Group f0 High Group f0 Row 0 = 697 Hz Column 0 = 1209 Hz Row 1 = 770 Hz Column 1 = 1336 Hz Row 2 = 852 Hz Column 2 = 1477 Hz Row 3 = 941 Hz Column 3 = 1633 Hz 75T204 TIMING (Refer to Figure 4.) PARAMETER CONDITIONS tON tOFF Tone Time Pause Time MIN NOM MAX UNITS for detection 40 - - ms for rejection - - 20 ms for detection 40 - - ms for rejection - - 20 ms tD Detect Time 25 - 46 ms tR Release Time 35 - 50 ms tSU Data Setup Time 7 - - µs tH Data Hold Time 4.2 - 5.0 ms Output Enable Time CL = 50pF, RL = 1k½ - - 200 ns Output Disable Time CL = 35pF, RL = 500½ - - 200 ns Output Rise Time CL = 50pF - - 200 ns Output Fall Time CL = 50pF - - 200 ns 5 75T204 5V Low-Power Subscriber DTMF Receiver APPLICATION INFORMATION excessive noise is present above 28kHz, the simple RC filter shown in Figure 5 may be employed to band limit the incoming signal. The 75T204 will tolerate total input RMS noise up to 12dB below the lowest amplitude tone. For most telephone applications, the combination of the high frequency attenuation of the telephone line and internal band-limiting make special circuitry at the input to the 75T204 unnecessary. However, noise near the 56kHz internal sampling frequency will be aliased (folded back) into the audio spectrum, so if Noise will also be reduced by placing a grounded trace around the XIN and XOUT pins on the circuit board layout when using a crystal. It is important to note that XOUT is not intended to drive an additional device. XIN may be driven externally; in this case leave XOUT floating. 2.4 k = 5% ANALOG IN NOISY SIGNAL 0.01 mF = 20% FIGURE 5: RC Filter 6 75T204 75T204 5V Low-Power Subscriber DTMF Receiver ELECTRICAL SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS (Operation above absolute maximum ratings may damage the device. connected to VP or GND, as appropriate.) All 75T204 unused inputs must be PARAMETER RATING DC Supply Voltage - V P +7V Operating Temperature -40°C to +85°C Ambient Storage Temperature -65°C to +150°C Power Dissipation (25°C) 65mW Input Voltage (All inputs except ANALOG IN) (VP + 0.5V) to -0.5V ANALOG IN Voltage (VP + .5V) to (V P - 10V) DC Current into any Input ±1.0mA Lead Temperature - Soldering, 10 sec. 300°C ELECTRICAL CHARACTERISTICS (-40°C ² TA ² +85°C, V P = 5V ± 10%) PARAMETER CONDITIONS Frequency Detect Bandwidth Amplitude for Detection Twist Tolerance each tone Twist= High Tone Low Tone MIN TYP MAX UNITS ±(1.5+2Hz) ±2.3 ±3.5 % of fO -32 -2 dBm ref. to 600Ω -10 +10 dB 0.8 Vrms 0dB dB* 60-Hz Tolerance Dial Tone Tolerance “precise” dial tone Talk Off MITEL tape #CM 7290 Digital Outputs “0” level, 400µA load 0 0.5 V (except XOUT) “1” level, 200µA load VP-0.5 VP V Digital Inputs “0” level 0 0.3V P V “1” level 0.7V P VP V 10 mV p-p 16 mA -12 dB* Power Supply Noise wide band Supply Current TA = 25°C Noise Tolerance MITEL tape #CM 7290 Input Impedance VP³V IN³V P-10 2 10 100KΩ||15pF * dB referenced to lowest amplitude tone 7 hits 75T204 5V Low-Power Subscriber DTMF Receiver MECHANICAL SPECIFICATIONS 14-Pin DIP 16-Pin SOL 8 75T204 5V Low-Power Subscriber DTMF Receiver PACKAGE PIN DESIGNATIONS CAUTION: Use handling procedures necessary for a static sensitive component. (Top View) D2 1 16 D4 D2 1 14 D4 D1 2 15 D8 D1 2 13 D8 EN 3 14 DV EN 3 12 DV VP 4 13 N/C 11 ATB N/C 5 12 ATB XIN N/C 6 11 XIN XEN 7 10 XOUT ANALOG IN 8 9 GND 75T204 VP 4 N/C 5 10 XEN 6 9 XOUT ANALOG IN 7 8 GND 14-Pin DIP 75T204 16-Pin SOL ORDERING INFORMATION PART DESCRIPTION ORDER NUMBER PACKAGING MARK 75T204 14-Pin PDIP 75T204-IP 75T204-IP 16-SOL 75T204-IL 75T204-IL 75T204 No responsibility is assumed by TDK Semiconductor Corporation for use of this product nor for any infringements of patents and trademarks or other rights of third parties resulting from its use. No license is granted under any patents, patent rights or trademarks of TDK Semiconductor Corporation and the company reserves the right to make changes in specifications at any time without notice. Accordingly, the reader is cautioned to verify that the data sheet is current before placing orders. TDK Semiconductor Corporation, 2642 Michelle Drive, Tustin, CA 92780-7019, (714) 508-8800, FAX: (714) 508-8877 1989 - 2000 TDK Semiconductor Corporation 04/24/00- rev. C 9