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| NT95089 Tone Dialer Features T Wide operating voltage range: 2.5V - 10V T Optimum use with a constant operating supply voltage T Tone T T T TV T T T (typically 3.5V ) amplitude stability of 1.5dB within the suggested operating temperature range Device power may be derived directly from telephone lines or from small batteries Low total harmonic distortion crystal standard (3.58MHz) is used to derive all frequencies, providing high accuracy and stability Specifically designed for electronic telephone applications Interfaces directly with a standard push-button telephone keyboard with common terminal Dual tone/single tone capability General Description The NT95089 DTMF generator is specifically designed for applications requiring a fixed supply operating voltage and a high stability tone output, making it ideal for electronic telephone applications. The NT95089 interfaces directly to a standard push-button telephone keyboard (common terminal connected to VSS) and operates directly from telephone lines. All necessary dual-tone frequencies are derived from the widely-used TV crystal standard, providing high accuracy and stability. The required sinusoidal waveform for individual tones is digitally synthesized on the chip, resulting in a waveform with low total harmonic distortion. A voltage reference which is stable over the operating temperature range is generated on the chip; this reference is used to regulate the dual tone frequency levels to ensure that they meet recommended telephone industry specifications. Pin Configuration Keyboard Assignments 1 4 7 * C1 2 5 8 0 C2 3 6 9 # C3 A B C D C4 R1 R2 R3 R4 1 NT95089 Block Diagram Absolute Maximum Ratings* Power Supply Voltage (VDD - VSS) . . . . -0.3V to +10.5V Input Voltage (VIN). . . . . . . . . . . . . -0.3V to VDD + 0.3V Maximum Power Dissipation (at 25C). . . . . . . . 500mW Operating Temperature. . . . . . . . . . . . . . -20C to +70C Storage Temperature. . . . . . . . . . . . . . -55C to +150C *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 (TOP = 25C, FOSC = 3.579MHz, unless otherwise specified.) Parameter Symbol Min. Typ. Max. Unit Conditions Valid key input (tone output mode) AKD outputs vary with key input (non-tone output mode) Test CKT. VDD1 Operating Voltage VDD2 2.5 10 V B 1.6 10 V 2 NT95089 DC Electrical Characteristics (continued) Parameter Symbol Min. Typ. Max. Unit Conditions VDD = 3V, one key input, all outputs unloaded VDD = 10V, one key input, all outputs unloaded VDD = 3V, no key input, all outputs unloaded VDD = 10V, no key input, all outputs unloaded Test CKT. IDD1 Supply Operating Current IDD2 1.0 1.4 mA B 6.6 10 mA ISD1 Standby Current ISD2 AKD Output Sink Current AKD Output off Leadage Current 1 20 A A 5 100 A IOL 0.5 1 mA VDD = 3V, VOL = 0.5V C IOH VIH VIL 0.8 0 30 100 760 2028 VOR 550 1520 Twist DIS% IOH1 0.13 1 1 10 1 0.2 A VDD VDD A A mVP-P mVP-P mVP-P mVP-P dB % mA VDD = 10V C Input Voltage Range - Row & Column Input Current (Pull-up) IIH IIH VOC 90 300 830 2200 600 1650 2 1 0.31 150 500 900 2380 650 1780 3 5 VDD = 3V, VIH = 0V VDD = 10V, VIH = 0V VDD = 2.5V, RL = 10K VDD = 10V, RL = 100K VDD = 2.5V, RL = 10K VDD = 10V, RL = 100K B Single Column Tone Output Amplitude Single Row Tone Output Amplitude Pre-Emphasis Distortion B B VDD = 5V, * Note VDD = 3V, VOH = 2.5V, one key input VDD = 10V, VOH = 9.5V, one key input B C Oscillator Output Drive Current IOH2 0.42 1.1 mA C 3 NT95089 DC Electrical Characteristics (continued) Parameter Symbol Min. Typ. Max. Unit Conditions VDD = 3V, VOH = 0.5V, one key input VDD = 10V, VOH = 0.5V, one key input VDD = 3V VDD = 10V Test CKT. C IOL1 Oscillator Output Sink Current IOL2 C1/01 C1/02 0.21 0.52 mA 0.8 2.1 12 10 16 14 mA pF pF C - Input/Output Capacitance Note: DIS% = 100 * (V 12 + V 2 2 +...+ VN 2 )1/2 (VIL2 + VIH 2 )1/2 1. V1. . . . Vn are the intermodulations or the harmonic frequencies in the 500Hz to 3400Hz band. 2. VIL and VIH are the individual frequency components of the DTMFsignal. AC Characteristics Parameter Oscillator Start up Time Tone Output Rise Time Pre-Digit Pause Symbol TSTART TR TPDP Min. Typ. 2 2 0 Max. 5 5 0 Unit ms ms ms Conditions VDD = 3.0V - 10.0V Frequency Tolerance of the Output Tones for DTMF Signaling R/C R1 R2 R3 R4 C1 C2 C3 C4 Spec. 697 770 852 941 1,209 1,336 1,477 1,633 Actual 699.2 766.27 847.54 948.09 1,216 131.8 1,472 1,645 Error(%) +0.32 -0.48 -0.64 -0.75 +0.58 -0.33 -0.34 +0.73 Unit Hz Hz Hz Hz Hz Hz Hz Hz FOSC = 3.579MHZ Conditions 4 NT95089 Pin Description Pin No. 1 6 Designation VDD VSS Description Positive power supply input Negative power supply input The NT95089 is designed to operate within a range of 2.5V to 10.0V. Chip enable input The chip enable input has an internal pullup to VDD. When this input is left unconnected or connected to VDD, the NT95089 operates normally. When this input is connected to VSS, tone generation is inhibited; however, all other chip functions continue to operate normally. Keyboard inputs Internal pullup resistors are present on the row and column inputs (20K - 10K); low levels on a particular row and column input correspond to a key entry. The NT95089 interfaces with the standard push-button telephone keyboard (see Figure 1).(Keyboard common terminal must be connected to VSS). Oscillator input Oscillator output The NT95089 contains an oscillator circuit with the necessary parasitic capacitances and feedback resistor on chip, making it necessary to connect only a standard 3.58MHz TV crystal across the OSCI and OSCO terminals to implement the oscillator function. The oscillator is enabled whenever a row input is activated. Any key down output The AKD output consists of an open drain N-channel device. When no keys are pressed, the AKD output is open. When a key is pressed, the AKD output = VSS. Single tone inhibit input The STI input is used to inhibit the generation of tones other than dual tones. It has an internal pull-down to VSS. When this input is left unconnected or connected to VSS, the SINGLE TONE mode is disabled. When this input is connected to VDD, single as well as dual tones may be generated as follows: DUAL TONE mode: When one row and one column are selected, a dual tone output consisting of an appropriate low group tone and high group tone is generated. If two digit keys that are not in the same row or same column are pressed, the dual tone mode is disabled and no output is provided. SINGLE TONE mode: Low group tones can be generated by pressing two digit keys in the appropriate row. High group tones can be generated by pressing two digit keys in the appropriate column, i.e., selecting the appropriate column input and pressing two row inputs in that column. 2 CE 3 - 5, 9 11 - 14 C1 - C4 R4 - R1 7 8 OSCI OSCO 10 AKD 15 STI 5 NT95089 Pin Descriptions (continued) Pin No. 16 Designation TONE Description DTMF signal output The NT95089 uses a Johnson counter and resistor ladder network (see block diagram) to synthesize the two desired frequencies in sinewaves. The ladder network is then used to mix the two. The NT95089 uses a bipolar NPN transistor, connected as emitter follower, to allow proper impedance transformation and at the same time preserve signal level Functional Description Crystal Specification Standard TV color burst crystals have a much tighter tolerance specification than is necessary for tone generation applications. Because the required tolerance specification for this type of application is more relaxed, lower-cost crystals can be used. Crystals with the following specifications are suggested for use with the NT95089: Frequency: 3.58MHz 0.02%. RS 100, LM = 96 mH, CM = 0.02pF, CH = 5pF, CL = 12pF. AKD Output Structure DTMF Generator The NT95089 has a well designed, digitally-synthesized sinewave with an 8-level, 16-segment structure. (See Figure 2.) Reference Voltage The structure of the reference voltage employed in the NT95089 is shown in Figure 3. It has the following characteristics: a) V is proportional to the supply voltage. Output tone amplitude, which is a function of (VDD - VREF), increases with supply voltage. (Figure 4). b) The temperature coefficient of VREF is low due to a single VBE drop. Use of a resistor divider also contributes to providing an accuracy of better than 10%. As a result, tone amplitude variations over temperature and unit to unit differences are held to less than 1.0dB. c) Resistor values in the divider network are chosen so that VREF is above the VBE drop of the tone output transistor even at the low end of the supply voltage range. This eliminates tone output clipping at low supply voltage and improves distortion performance. N-CHANNEL OPEN DRAIN OUTPUT 6 NT95089 C2 1 R1 2 5 8 0 3 6 R2 4 7 R3 9 # R4 COMMON (CONNECT TO V S S) * C1 R O N (Contact Resistance) C3 1 K MECHANICAL LINKAGE Figure 1. Standard Telephone Push-Button Keyboard (1) R1 Single Tone (2) C1 Single Tone (3) DTMF Figure 2. DTMF Waveforms 7 NT95089 xAA (c) AIA NAEAI OIAE AINIEOOAAE *I O (c)xAA(R)xOAEC OIAE AINIEOOAAE ix (c)oio * (c)OINAE ixx *I O I O xOAEC (c) * OONNIU xIOAEAE (c)xIOO Figure 3. Structure of the Reference Voltage Figure 4. Typical Single Tone Output Amplitude vs. Supply Voltage (RL = 10K) Timing Waveform CE KEY INPUT TONE AKD OSC T START 8 NT95089 Application Circuit (for reference only) L1 ON- HOOK ON- HOOK L2 RINGER NETWORK 150 SPEECH NETWORK C2 pin 4 .0047 F 250V 1 16 Q1 12V o 22K 100 1 R1 2 3 4 5 6 R2 pin 13 NT95089 10 AKD 7 R3 8 9 6 15 7 8 * 0 # R4 pin 11 3.579 MHz XTAL SS ) COMMON (CONNECT TO V C1 pin 3 R O N (Contact Resistance) C3 pin 5 MECHANICAL LINKAGE 1K Standard Telephone Push Button Keyboard 9 NT95089 Test Circuits (A) (B) (C) Ordering Information Part No. NT95089 Package 16L DIP 10 NT95089 Package Information DIP 16L Outline Dimensions D 16 9 unit: inches/mm E1 1 S 8 E C A2 A A1 Base Plane Seating Plane B B1 e1 eA L Symbol A A1 A2 B Dimensions in inches 0.175 Max. 0.010 Min. 0.1300.010 0.018 +0.004 -0.002 0.060 +0.004 -0.002 0.010 +0.004 -0.002 0.750 Typ. (0.770 Max.) 0.3000.010 0.250 Typ. (0.262 Max.) 0.1000.010 0.1300.010 0 ~ 15 0.3450.035 0.040 Max. Dimensions in mm 4.45 Max. 0.25 Min. 3.300.25 0.46 +0.10 -0.05 1.52 +0.10 -0.05 0.25 +0.10 -0.05 19.05 Typ. (19.56 Max.) 7.620.25 6.35 Typ. (6.65 Max.) 2.540.25 3.300.25 0 ~ 15 8.760.89 1.02 Max. B1 C D E E1 e1 L eA S 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 |
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