NT Tone Dialer. Features. General Description. Pin Configuration & Keyboard Assignments

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1 Tone Dialer Features Wide Supply Voltage Range: 1.8V to 5.5V Ceramic oscillator (480KHz ceramic resonator) Fully debounced scanning keyboard Minimum tone duration: 73ms Very low tone distortion: less than 1% in band On-chip power-on reset SINGLE-TONE OUTPUT mode Low standby and operating power All pins protected against ESD and latch-up Low frequency error: max. +0.3% General Description The NT95088 DTMF is specifically designed to implement a dual tone telephone dialing system in applications which require a fixed supply operation and a highly stable tone output level, making it well suited for electronic telephone applications. The device can interface directly to a standard XY matrix telephone keyboard and operates directly with the telephone lines. All the required dual-tone frequencies are derived from the widely used 480KHz ceramic resonator, which Pin Configuration & Keyboard Assignments provides high accuracy and stability. The sinusoidal waveforms for the individual tones are digitally synthesized on the chip. waveforms generated such have low total harmonic distortion. The built-in minimum tone duration function provides an adaptive solution and fast dialing with short DTMF output being achieved. A reliable power-on reset circuit guarantees proper functioning under a variety of power supply conditions. Block Diagram R R R3 * 0 # R4 C1 C2 C3 1

2 Absolute Maximum Ratings* Power Supply Voltage V to +6.0V Input Voltage V to VDD + 0.3V Maximum Power Dissipation mW Operating Temperature (Top) C to +70 C Storage Temperature(Tstg) C to +150 C *Comments Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to this device. These are stress ratings only. Functional operation of this device at these or any other conditions above those indicated in the operational sections of this specification is not implied or intended. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability. DC Electrical Characteristics (VDD = 3.5V, VSS = 0V, FOSC = 480KHz, TOP = 25 C, unless otherwise specified.) Parameter Symbol Min. Typ. Max. Unit Conditions Test CKT. Operating Voltage VDD V OSC Running, All O/P Unloaded B Operating Current IDD ma VDD = 2.0V, All O/P Unloaded B Standby Current ISD µa VDD = 2.0V ISD µa VDD = 3.5V All O/P Unloaded A MUTE Output Sink Current IOL ma VDD = 2.0V IOL ma VDD = 3.5V VOL = 0.5V C MUTE Output Source Current IOH ma VDD = 2.0V, VOH = 1.5V IOH ma VDD = 3.5V, VOH = 3.0V C MUTE Output Sink Current ma VDD = 2V ma VDD = 3.5V VOH = 0.5V C MUTE Output Source Current ma VDD = 2V, VOH = 1.5V 2 4 ma VDD = 3.5V, VOH = 3.0V C Row I/P Current 0.65 ma VDD = 3.5V, VIN = 0V - Column I/P Current 16.5 µa VDD = 3.5V, VIN = 0V - 2

3 DC Electrical Characteristics (continued) Parameter Symbol Min. Typ. Max. Unit Conditions Test CKT. Input Voltage Range Single Column Tone Output Amplitude Single Row Tone Output Amplitude VIH 0.8 VDD 1 VDD VIL VDD VOC mvp-p VDD = 2.0V, RLOAD = 15KΩ VOC mvp-p VDD = 3.5V, RLOAD = 15KΩ VOR mvp-p VDD = 2.0V, RLOAD = 15KΩ VOR mvp-p VDD = 3.5V, RLOAD = 15KΩ - B B Valley of Single Tone Vv VDD RLOAD = 15KΩ B Distortion THD 5.0 % *(See note below) B Pre-Emphasis Twist db B * Note: DIS% = (V1 + V V N ) 2 2 (VIL + V IH ) 1/2 1/2 1. V1.... Vn are the inter-modulation or the harmonic frequencies in the 500Hz to 3400Hz band. 2. VIL and VIH are the individual frequency components of the DTMFsignal. 3

4 AC Characteristics Parameter Symbol Min. Typ. Max. Unit Conditions OSC Start-up Time TSTART 5 ms VDD = V Debounce Time TD 10 ms Minimum Tone Duration TMTD 73 ms Pre-Digit Pause TPDP1 43 ms Mute Delay Time TPDP2 5 ms Inter-digit pause TTIDP 73 ms Comparisons of Specified vs. Actual Tone Frequencies Table 1 shown below details the frequency tolerance of the output tones for DTMF signals generated by the NT95088 tone output pin. R/C Output Frequency (Hz) Specified Actual Error % * Unit Conditions R Hz R Hz R Hz R Hz FOSC = 480KHz C1 1,209 1, Hz C2 1,336 1, Hz C3 1,477 1, Hz *: % Error does not include oscillator drift Table 1 4

5 Pin Description Pin No. Designation Description 1, 2, 3, 4, 12, 13, R4 - R1 C1 - C3 OSCI OSCO VSS VDD Key inputs These are the keyboard input pins of the NT The output of Column pins, C1, C2 and C3 are high and the output of Row pins, R1, R2, R3 and R4 are low in the standby state. Each column has a pull-up resistor (120KΩ typically). A logic low is presented at the connected row and column pins. A debouncing circuit is provided (10 ms typically). Multiple keys Single Tone output is provided for testing purposes. Oscillator input/output A 480KHz ceramic resonator and two 100 pf serial loading capacitors to form a complete oscillator circuit. The oscillator circuit is activated upon the depression of any key. Maximum start-up time is 5 ms at VDD = 3.5V. Power supply VSS: Negative Power Supply VDD: Positive Power Supply Operating Voltage Range is 1.8V to 5.5V 9 TONE Dual-tone multi-frequency signal output The output impedance is typically 1.5KΩ. This pin is forced to VSS when there is no output. The column tone to row tone ratio is typically 2 db. A single tone is created by pressing two or more keys in a row for the appropriate row tone and two or more keys in a column for the appropriate column tone. 10 MUTE MUTE signal output active low This is an open drain output device. This output is activated during tone output. It can sink the current from a higher voltage source (>VDD) directly. 11 MUTE MUTE signal output active high This is an inverter output. This output is activated during tone output. The source/sink capability is 0.45/0.7 ma at 2V supply voltage and 0.5 drain voltage fall. 5

6 Functional Description 1. N-Channel Open Drain Output-MUTE DTMF Tone Generator The NT95088 is well designed with a 6 level, 12 segment, 1/2 VDD reference voltage structure. The Total Harmonic Distortion (THD) of the NT95088 DTMF output is typically 5%, which is a very low value compared with the EIA RS-470 standard of 10% THD. The temperature coefficient of the DTMF output amplitude is balanced to zero from the adaptive DTMF generator structure. The output strength of the Column Tone is pre-emphasized 2.5 db higher than the Row Tone. The typical equivalent output impedance of the DTMF generator is 1.5KΩ. "DTMF Signal THD VS. Operating Voltage" and "DTMF Output Amplitude VS. Operating Voltage" is shown in figures 1 and 2 for reference in circuit design. (THD) Total Harmonic dbm (V) Amplitude (R1) -50 ~ ~ ~ V Operating Voltage DTMF Signal THD VS. Operating Voltage V Operating Voltage DTMF Output Amplitude VS. Operating Voltage Figure 1. Figure 2. 6

7 (1) R1 Single Tone (2) C1 Single Tone (3) DTMF Figure 3. DTMF Waveforms Timing Waveform (when power supply is ready) KEY IN 50ms 80ms 100ms TSTART TSTART OSC OSCILLATION OSCILLATION TD TD TONE OUTPUT TMTD TMTD MUTE TD TD MUTE TSTART Oscillator Start Up Time TD Debounce Time TMTD Minimun Tone Duration 73ms 7

8 Application Circuits (for reference only) A Low Cost Touch-Tone Telephone Application VOICE NETWORK EXAMPLE TIP RING ZNR 240WV HOOK SWITCH D3 D4 OFF HOOK ON HOOK BG-1 D1 D2 2mA CURRENT SOURCE C1 + R12 R2 R5 R3 Q1 R4 R1 + R11 C2 R10 R6 C3 Q2 R9 R7 D5 R8 C4 + C10 C5 D6,D7 C6 + ZD1 MIC+ MICROPHONE TRANSMITTER R1 8 VDD 7 VSS 1 DC COUPLE R15 Q R2 R3 NT95088 C7 C8 R16 * 0 # 1 R4 TONE C3 C2 C1 OSC1 OSC0 MUTE R17 R18 C9 C11 2 AC COUPLE OSC1 C13 C12 Parts List Diode D1 - D4: IN4004 x 4 D5, D6, D7: IN4148 x 3 Transistor Q 1 - Q4: 2SC945 x 4 Resistor: R1: 4.7K R2: 3.3K R3: 180Ω R4: 22 Ω R5: 1.2K R6: 1.2K R7: 680K R8: 2.2K R9: 75 Ω R10: 4.7K R11: 22K R12: 10K R13: 10K R14: 1.2K R15: 1.2K R16: 220 Ω R17: 10K R18: 1.2K Capacitor C1: 10 µf/16wv C2: 10 µf/16wv C3: 0.1 µf/50wv C4: µf/50wv C5: µf/50wv C6: 47 µf/10wv C7: µf/50wv C8: µf/50wv C9: µf/50wv C10: 1 µf/10wv C11: µf/50wv C12: 100pF C13: 100pF Oscillator OSCI: 480KHz Ceramic Resonator High Voltage Protector ZNR: 240WV/1W Varistor Zener Diode ZDI: 3.9WV/0.5W ZD Receiver 100Ω receiver 8

9 Transmitter ECM mic. 9

10 Touch Tone Telephone Application (for reference only) TIP 240V ZNR OFF HOOK D3 D1 D4 D2 D1-D4: IN4004X4 2mA Current Source RING HOOK SWITCH ON HOOK 10µF/10WV + ZD 3V9/ 0.5W VOICE NETWORK R1 VDD MUTE MUTE 1 AC COUPLE EXAMPLE * 0 # R2 R3 R4 NT95088 TONE OSC K2 3K µF 0.033µF C3 C2 C1 VSS OSC1 2 DC COUPLE EXAMPLE OSC 100pF x2 1K2 1K µFx2 220Ω TR:2N5551 Note: AC couple and DC couple interfacing is determined by matching with the voice network. Test Circuits (A) (B) (C) Ordering Information Part No. NT95088 Package 14L DIP 10

11 Package Information DIP 14L Outline Dimensions unit: inches/mm D 14 8 E1 1 7 S E A A2 C A1 Base Plane L Seating Plane B B1 e1 α ea Symbol Dimensions in inches Dimensions in mm A Max Max. A Min Min. A ± ±0.25 B B C D Typ. (0.770 Max.) Typ. (19.56 Max.) E 0.300± ±0.25 E Typ. (0.262 Max.) 6.35 Typ. (6.65 Max.) e ± ±0.25 L 0.130± ±0.25 α 0 ~ 15 0 ~ 15 ea 0.345± ±0.89 S Max Max. Notes: 1. The maximum value of dimension D includes end flash. 2. Dimension E1 does not include resin fins. 3. Dimension S includes end flash. 11