View FX105A_5904674.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

FX105A tone detector ? 1999 consumer microcircuits limited d/105a/5 september 1999 1.0 features provisional issue operates in high noise conditions adjustable bandwidth 3 3 36db signal input range adjustable frequency high sensitivity wide voltage range (2.7v to 5.5v) low power single and multitone system applications 1.1 brief description the FX105A is a monolithic cmos tone operated switch, designed for tone decoding in single and multitone signalling systems. the FX105A uses decoding techniques which allow a tone to be recognised in the presence of high noise levels or strong adjacent signals. detection centre frequency and bandwidth can each be independently adjusted. the design is immune to high levels of harmonic and sub-harmonic interference. excellent noise immunity and constant bandwidth are maintained over a wide range of input signal levels.
tone detector FX105A ? 1999 consumer microcircuits limited 2 d/105a/5 contents section page 1.0 features ................................ ................................ ................................ ...... 1 1.1 brief description ................................ ................................ ......................... 1 1.2 block diagram ................................ ................................ ............................ 3 1.3 signal list ................................ ................................ ................................ ... 4 1.4 external components ................................ ................................ ................. 5 1.5 general description ................................ ................................ .................... 6 1.6 application notes ................................ ................................ ....................... 7 1.6.1 general ................................ ................................ ........................ 7 1.6.2 method for calculating external component values ................ 7 1.6.3 replacement for fx105 ................................ ............................. 11 1.7 performance specification ................................ ................................ ....... 12 1.7.1 electrical performance ................................ .............................. 12 1.7.2 packaging ................................ ................................ .................. 14
tone detector FX105A ? 1999 consumer microcircuits limited 3 d/105a/5 1.2 block diagram figure 1 block diagram
tone detector FX105A ? 1999 consumer microcircuits limited 4 d/105a/5 1.3 signal list package d4/p3 signal description pin no. name type 1 input amp in i/p ac couple to this input of the input buffer amplifier. 2 input amp out o/p the input buffer amplifier output. 3 rw i/p the input to the detect/word filter. 4 rv i/p the input to the vco loop filter. 5 c3a o/p word filter capacitor pin a. 6 c3b o/p word filter capacitor pin b. 7 c2a o/p vco loop filter capacitor pin a. 8 c2b o/p vco loop filter capacitor pin b. 9 detect out o/p open drain cmos output, active on detect. note that a load resistor to v ss is required. 10 v ss power ground. 11 r2hi i/p bandwidth control resistor pin a. 12 r2lo i/p bandwidth control resistor pin b. 13 c1b o/p vco capacitor b. 14 c1a o/p vco capacitor a. 15 r1 i/p vco discharge resistor. when potentiometer tuning is required, a series resistor is recommended to prevent possible shorting to ground. 16 v dd power power supply. notes: i/p = input o/p = output
tone detector FX105A ? 1999 consumer microcircuits limited 5 d/105a/5 1.4 external components
tone detector FX105A ? 1999 consumer microcircuits limited 6 d/105a/5 1.5 general description the input signal to the FX105A is ac coupled to the buffer amplifier input, which is internally biased at 50% of supply voltage. the signal appears at the output of the buffer amplifier as an ac voltage superimposed on the dc bias level. the signal is then coupled via r v and r w to the voltage controlled oscillator (vco) and word sampling switches, which cyclically connect c 2 and c 3 into the circuit to form four sample-and-hold rc circuit integrators. see figure 3. with no input signal level, each capacitor charges to the dc bias level so differential voltages are zero. when an input signal is applied each capacitor receives an additional charge. this charge is determined by the integrated average of the signal waveform during the time the capacitor is switched into the circuit. figure 3 shows the operating sequence of the vco sa mpling switches and their relationship to a locked-on in-band signal. c 2a and c 2b should not receive any additional charge since they always sample the input as it crosses the dc bias level. should the signal not be locked to the vco, a positive or negative charge voltage will appear on c 2a or c 2b . this voltage, when differentially amplified, is applied to the vco as an error correcting signal to enable the vco to ? lock. ? figure 3 also shows the operating sequence of the ? word ? sampling switches and th eir relationship to a locked-on in-band signal. as the figure shows, the charge applied to c 3a should always be positive, and the charge applied to c 3b should always be negative (with respect to the common bias level). these capacitor potentials are differentially amplified and applied to a dc comparator, which switches at a pre-determined threshold voltage v th (known as the word filter sensitivity). the comparator output is a logic signal used to control a counter. this counter switches the FX105A output on when the comparator output is maintained in the ? word present ? state for a minimum number of consecutive signal samples. the activated output switch reduces the comparator threshold by 50%, introducing threshold hysteresis. output chatter with marginal input signal amplitudes is thereby minimised. figure 3 sampling clocks of commutating filters
tone detector FX105A ? 1999 consumer microcircuits limited 7 d/105a/5 1.6 application notes 1.6.1 general the external components shown in figure 2 are used to adjust the various performance parameters of the FX105A. the signal-to-noise performance, response time and signal bandwidth are all interrelated factors which should be optimised to meet the requirements of the application. by selecting component values in accordance with the following formulae, optimum circuit performance is obtained for any given application. first define the following application parameters: (a ) the input frequency to be detected (f 0 ). the free running frequency of the vco is set to 6 times this frequency by observing the output across c 1 or r 1 . (the frequency observed at pin 15 (r 1 ) is 6 x f 0 and the frequency observed at pins 13 or 14 (c 1a or c 1b ) is 3 x f 0 ). (b ) the FX105A minimu m usable bandwidth (mubw). this is obtained by taking into account the worst case tolerances ( d f 0 ) of the input frequency and the variations in the FX105A vco frequency due to supply voltage ( d v dd ) and temperature ( d temp) variation of the FX105A and its supporting components. (c ) the maximum permissible FX105A response time. (d ) the minimum input signal amplitude. (this must be larger than the threshold voltage, v th ). (e ) the maximum input signal amplitude. using this information the appropriate component values can be calculated, and the signal-to-noise performance can be read from a chart. do not add large safety margins for response time and minimum signal amplitude: reasonable margins are already included in the formulae. excessive margins may result in reduced noise immunity. 1.6.2 method for calculating external component values the example on the following pages demonstrates the calculation of component values for any given application. for the purpose of this example, the values below are used: (a ) f 0 = 2800hz (b) d temp = 100c, d v dd = 1v, d f 0 = 0.5% (c) maximum allowe d response time t on = 50msec (d) minimum input signal amplitude v in min = 200mvrms (e) maximum input signal amplitude v in max = 400mvrms 1.6.2. 1 calculate r 1 c 1 (c 1a = c 1b ) the components r 1 , c 1a and c 1b set the free running frequency of the vco and therefore the f 0 of the FX105A. as shown below, the frequency of 2800hz corresponds to a capacitor value of 220pf and a resistor value of 385 k w . this resistance can be achieved with a 330 k w fixed resistor and a 100 k w potentiometer. r 1 should lie in the range 100 k w to 680 k w . r 1 c 1a = 1/ [2kf 0 ] = 1/ (2 x 2.1 x 2800 ) = 85sec where k is a constan t = 2.1 5%. note that the values of c 1a and c 1b need to include the stray capacitance attributable to the package style and printed circuit board layout. a typical value of 6.6pf per pin should be assumed. if c 1a = c 1b = 233.2pf, then r 1 ? 364 k o h m
tone detector FX105A ? 1999 consumer microcircuits limited 8 d/105a/5 1.6.2.2 calculate minimum usable bandwidth (%) minimum usable bandwidth (mubw) is the total (%) bandwidth required for the following: (a) input signal frequency tolerance ( d f 0 ) (b) FX105A vco temperature coefficient (t c = - 100ppm/oc) (c) FX105A vco supply voltage coefficient (v c = 2330ppm/v) add (a), (b) and (c) and express as total (%) bandwidth, not as a (%) value. mubw = d f 0 + |t c | d temp + v c d v dd mubw = 0.5 + 0.01 x 100 + 0.233 x 1 ? 2% 1.6.2.3 calculate the recommended operating bandwidth note again that this is the total (%) bandwidth: bw = ? [10 + mubw] = ? (10 + 2) = 6% 1.6.2.4 select r 2 for operating bw r 2 = 4.8 bw/ [10.35 - bw] = 4.8 x 6/ (10.35 - 6) ? 6.8k w the exact bandwidth given by any value of r 2 will vary slightly. in applications where an exact bandwidth is required, r 2 should be a variable resistor to permit adjustment. 1.6.2.5 calculate r v c 2a (c 2a = c 2b ) use nearest preferred values r v c 2a ? 100/ [3 f 0 bw] ? 100/ (3 x 2800 x 6) ? 2msec therefore r v ? 200k w for c 2a = c 2b = 10nf 1.6.2.6 define the maximum allowed response time the maximum response time (t on ) is the sum of the vco lock time (t lock ) and the word integration time (t word ). the FX105A?s t on must not exceed the maximum time allowed for the application, but a value lying near the maximum gives the best s/n performance. (a) calculate t lock t lock = 150/ [f 0 bw] = 150/ (2800 x 6) ? 9msec note: t lock may vary from near zero to the value given, causing corresponding variations in actual t on . (b) calculate maximum allowable t word t word = t on max - t lock = 50 - 9 = 41msec note: since the maximum allowed response time (t on ) is 50msec, a maximum word integration time of 41msec is available.
tone detector FX105A ? 1999 consumer microcircuits limited 9 d/105a/5 1.6.2.7 calculate r w c 3a (c 3a = c 3b ) use nearest preferred values. r w c 3a ? t word / [ - 3in (1 - v th / v in min ) ] where v th is the word filter sensitivit y, see section 1.7.1 a signal amplitude of 200mv and a resistor value r w of 465k w with a 220nf capacitor for c 3a and c 3b will yield a t word time of 41msec. this in turn yields a response time of 9msec + 41msec = 50msec. 1.6.2.8 calculate the maximum de-response time t off ? - 3 r w c 3a in (v th / v in max ) where v th is the word filter sensitivity, see section 1.7.1 for improved de-response time, a diode (1n914 or si milar) can be placed between pins 5 and 6, as shown in figure 2. the formula and figure below show the approximate time the FX105A will take to turn off after an in-band signal has been removed. the effect of this diode is to greatly reduce the turn-off time with signal input amplitudes greater than 300mv rms . figure 4 is for v dd = 5v; for lower v dd then k dt increases. t off ? k dt r w c 3a so for a maximum signal amplitude of 400mv, a resistor value r w of 465k w with a 220nf capacitor for c 3a and c 3b and a diode between pins 5 and 6, a de-response time of ? 363msec is obtained. figure 4 k dt factor for t off vs. signal input amplitude
tone detector FX105A ? 1999 consumer microcircuits limited 10 d/105a/5 1.6.2.9 calculate signal to noise performance worst-case s/n calculations depend on calculation of a value ? m ? using the formula shown below: m = r w c 3a / [3 r v c 2a ] substituting our example values, m = 465 x 0.22 / (3 x 200 x 0.01) = 17.05 by substituting this value for m in figure 5 th e minimum required s/n of an in band tone with respect to an adjacent interfering tone can be found. this has to be increased if the required tone amplitude is close to the word filter sensitivity v th . figure 5 s/n vs. bw separation the following formula expresses the reduction in noise immunity as the input signal approaches the word filter sensitivity v th . required s/n = 20 log (v in / [v in - v th ] ) + s/n figure 5 if this s/n is better than required for the application, r w c 3a can be reduced, or the operating bandwidth can be increased to obtain a faster tone detection time. if the s/n performance is not adequate, the operating bandwidth can be reduced toward the mubw, or r w c 3a can be increased to improve s/n performance at the expense of a slower response time.
tone detector FX105A ? 1999 consumer microcircuits limited 11 d/105a/5 1.6.2.10 calculation of pll filter phase shift capacitor c 4 is used to phase shift the input to the vco commutating filter by 30, thus shifting the sampling clocks by the same amount. this enables the "word" sampling filter to sample and integrate at the maxima and minima of the input tone. c 4 = tan (30) / [2 p f 0 r v ] ? 0.092 / [f 0 r v ] ? 164pf 1.6.3 replacement for fx105 figure 6 depicts the circuit changes required to replace a fx105 with a FX105A device. a 5v zener diode and a resistor can be used to generate a 5v supply voltage from an existing 12v supply. if the detect output needs to pull up beyond the 5v supply, a transistor amplifier following the output can be used. figure 6 circuit changes for 12v to 5v conversion
tone detector FX105A ? 1999 consumer microcircuits limited 12 d/105a/5 1.7 performance specification 1.7.1 electrical performance absolute maximum ratings exceeding these maximum ratings can result in damage to the device. min. max. units supply (v dd - v ss ) -0.3 7.0 v voltage on any pin to v ss -0.3 v dd + 0.3 v current into or out of v dd and v ss pins -30 +30 ma current into or out of any other pin -20 +20 ma maximum output switch load current +10 ma p3/d4 package min. max. units total allowable power dissipation at tamb = 25c 800 mw ... derating 13 mw/c storage temperature -55 +125 c operating temperature -40 +85 c operating limits correct operation of the device outside these limits is not implied. notes min. max. units supply (v dd - v ss ) 2.7 5.5 v operating temperature -40 +85 c
tone detector FX105A ? 1999 consumer microcircuits limited 13 d/105a/5 operating characteristics for the following conditions unless otherwise specified: v dd = 3.0v to 5.0v, tamb = - 40c to +85c, load resistance on decoder output pin = 20k w notes min. typ. max. units static parameters i dd 2 - 0.9 3.0 ma amplifier input impedance - 200 - k w digital output impedance - 500 - w analogue output impedance - 1000 - w dynamic parameters input signal amplitude 2 - - 1.0 vrms frequency 40 - 20,000 hz response threshold 1,2 - 30 - mvrms deresponse threshold 1,2 - 10 - mvrms bw range 4 5.6 - 10 %f 0 signal to noise performance -6 -9 - db (f 0 /2) subharmonic rejection - 30 - db (5 f 0 ) harmonic rejection - 20 - db vco frequency 3 240 - 120,000 hz frequency stability (t c ) - -100 - ppm/c frequency stability (v c ) - 2330 - ppm/v amplifier open loop gain - 60 - db gain bandwidth product - 1.0 - mhz closed loop gain - 0 - db word commutating filter sensitivity (v th ) 2 - 25.0 - mvrms notes: 1. with diode (d 1 ) fitted. 2. for v dd = 5v. multiply by v dd /5v for other supply values. 3. observing pins 13, 14 or 15 (d4/p3 package) will cause a frequency shift due to additional loading. if tuning the centre frequency by observing the vco, design in a buffer amplifier between pin 15 and the probe/calibration point and tune with no input signal. otherwise, tune by observing the detect output band edges while sweeping the input signal. the frequency at pin 15 is 6xfo, while at pins 13 and 14 the frequency is 3xfo. 4. adjust according to equation for r 2 in section 1.6.2.
tone detector FX105A ? 1999 consumer microcircuits limited 14 d/105a/5 1.7.2 packaging figure 7 - soic mechanical outline: order as part no. FX105Ad4 figure 8 - dil mechanical outline: order as part no. FX105Ap3
tone detector FX105A handling precautions: this product includes input protection, however, precautions should be taken to prevent device damage from electro-static discharge. cml does not assume any responsibility for the use of any circuitry described. no ipr or circuit patent licences are implied. cml reserves the right at any time without notice to change the said circuitry and this product specification. cml has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product specification. specific testing of all circuit parameters is not necessarily performed. oval park - langford maldon - essex cm9 6wg - england telephone: +44 (0)1621 875500 telefax: +44 (0)1621 875600 e-mail: sales@cmlmicro.co.uk http:// www.cmlmicro.co.uk

▲Up To Search▲

Price & Availability of FX105A

	To Download FX105A Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .