UM92870 UMC | Alldatasheet
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Technical content
E Integrated DTMF Receiver c Full DTMF receiver in single 18-pin package ® Uses inexpensive 3.5795 MHz crystal “® Single 5-volt power supply ™ CMOS for low power consumption
8 Internal gain setting amplifier ™ Tristate outputs
® Adjustable guard time ™ Early steering output ® Built-in dialtone filter General Description ‘The UM92870 is a complete DTMF receiver designed the dualtone signal into low-group and high-group fo detect standard DTMF signals. It includes a tones. The decoder decodes all 16 DTMF tone pairs into ifferential input amplifier, fiter section, — decoder ‘a four bit code. The steering logic circuits allow the fgection, and steering logic circuits. The differential designer to tailor system parameters such as talk-off input amplifier allows adjustment of gain and choice and noise immunity, The UM92870 is packaged in 3 ‘of input configuration. The filter section provides a standard 18-pin DIP configurations and requires only dial tone filter for dialtone rejection and separates a few external passive components. Pin Configurations amps 18 1) Yp0 sis(e ae 1) Yoo vw : 10 DP) Yoo. awe a7 Pisver aw}? 17 Psver aw}? a Psever ef] as Dest es(]s as Dest esC]s as Dest am (] Ss as Dee eaC]s as Doe mnC]s i as Dae eat] a Des por(] ¢ as Des por(je ax Des osca(] 7 az Dez osei(]? azPjoz osea(}? a De oscz(]s afe escz(]e ade osc2[]s a Det ‘es 2 so Pree ve] 2 10 ree Yes C] ® 10 [v0
@2 ous wr) ear! bone Pe, ' HE mL ow oot exert cece =) co Pu surecenomsite | nercorcn | | ceventen [=eno Fitter 2a LR LGR Tet an =a “> wes = a [=o We Hive ow ae oa seat ma neo rag Pin Description Gain select. Gives access to output of front end differential amplifier for connection of feedback resistor. VREF Reference Voltage output, May be used to bias the inputs at midrail, Von / 2. INH: DTMF signal controlWhen this pin is pulled high, detection of tone pairs containing the 1633Hz component is inhibited. To detect all 16 standard digits this pin must be pulled low. 8/ H = Digital output format control. When this pin is pulled low, the UM92870 output is given in hexadecimal code. When input is high, output is in 2-018 binary code. Output codes are shown in Table 1. INH , B/ H PDI: power down input. To enter power down mode, this pin must be PDI pulled high, UMS2870A Pin No. 5,6 INH, B/H
D n_ (Continued) if = fox [em [ee [ome a osc2 Clock output. A 3.5795 MHz crystal connected betwwen OSC1 and OSC2 completes the oscillator circuit, 10 TOE Three-state output enable. Logic high enables the output from Q1 through O4. a1-08 Three-state output. When enabled by TOE, provides the code which corresponds to the last valid tone-pair received. See Table 1. Delayed steering output, Presents a logic high when a received tone- ie) pair has been registered and the output latch updated; returns to logic low when the voltage on St/Gt falls below VTsT. Early steering output. Presents a logic high once the digital est . fe) algorithm has detected a valid tone pair, Any subsequent loss of signal condition will cause ESt to return to a logic low. Steering input/guard time output (bidirectional). A voltage greater than Vrst detected at St causes the device to register the detected 7 St/GT yo tone pair and update the output latch. A voltage less than V1st ‘output acts to reset the external steering time constant; its state is a function of ESt and the voitage on St. fe [ve [ol Pee venoen pee!
Table 1. DTMF Signal Output Codes
‘ment of gain with the feedback resistor, R5. Figure 1. Single Ended Input Configuration Figure 2. Differential input Configuration form, is then split into its individual high and low will be two rectangular waves.