that corporation; 45 sumner street; milford, massachusetts 01757-1656; usa tel: +1 508 478 9200; fax: +1 508 478 0990; web: www.thatcorp.com that corporation ingenius ? line receiver ic demonstration system that 1200-demo description the that1200 demonstration system is a self-contained circuit board that simplifies evaluation of the that1200, that1203, and that1206 ingenius? line receiver ics. com - pletely assembled and tested, this system comes with xlr connectors for signal input and output, and a 3 pin header for connection to an external regulated dc power supply. j1 is a female xlr connector that can ac - cept a balanced or unbalanced input signal, while p1, a male xlr connector, delivers an unbalanced output from the ic line receiver. an external 15v power supply should be con - nected via header p2 (labeled cn1 on some older revisions of the pcb fabrication). c1-c3 shunt unwanted rfi currents to chassis ground. the "t" arrangement of these components minimizes cmrr degradation at high frequencies resulting from any mismatch between c1 and c2, (the shunt paths for each input share c3, and c3's impedance domi - nates that of c1 and c2). r2 and r3 further improve rfi rejection. ingenius circuit operation is enabled by bootstrapping the ic?s common mode input impedance via c4. cmout is the output of an on-board amplifier connected to sample the common mode voltage at pins 2 and 3. cmin uses the ac coupled version of this voltage to bootstrap the internal resistors provided to reference the inputs to the ref pin (typically connected to ground) and to provided a return for the input bias currents when the ic is ac c1 470p c2 470p c3 100p c4 220u r6 4k75 r1 51r 1 in- 2 in+ 3 cmin 5 4 8 7 out 6 u1 that1206 5 4 3 1 2 2 3 1 j1 (input) xlr-female 5 4 3 1 2 12 3 p1 (output) xlr-m -15 +15 c5 100n c6 100n c7 22u c8 22u r2 100r r3 100r r4 0r d1 1n4004 d2 1n4004 +15 -15 r5 0r rfi protection 1 2 3 p2 input power tp1 tp2 tp3 tp4 tp5 tp6 see applications section of the that1200 datsheet for alternatives ref vcc cmout vee figure 1. that1200 demonstration system schematic 600036 rev. 00d
that corporation; 45 sumner street; milford, massachusetts 01757-1656; usa tel: +1 508 478 9200; fax: +1 508 478 0990; web: www.thatcorp.com 600036 rev. 00d ingenius? line receiver ic demonstration system coupled. the net effect is to make the ic nearly immune to imbalances in common mode source impedances over the audio fre - quency range. putting an unbalanced imped - ance in the location of r2 or r3 is a useful way to test this feature. while c4 provides a means to bootstrap the ic?s internal input impedance, it does nothing for external impedances (like the capacitors in the rfi protection). r6 improves this situa - tion under many circumstances. at frequencies where the impedance of r6 is substantially less than that of c3 (and the that120x has sufficient gbw product), the common node of c1-3 and r6 will be driven by a replica of the common mode voltage found on pins 2 and 3. since the common mode voltage cannot de - velop across c1 and c2, there cannot be any current associated with this common mode voltage, and as a consequence, these compo - nents cannot load any potentially unbalanced common mode source impedance. without this loading, there cannot be any common mode to differential conversion that might oth - erwise be associated with un-bootstrapped loads. to ease prototyping of specific applications, spare circuit board area is perforated with plated through holes. this makes this board particularly useful for experimentation. with a that1200 demonstration system and standard audio cables, an engineer can begin evaluating the performance of the that1200 series of ingenius? line receivers in seconds, and try out new circuit ideas in minutes. that 1200 series demo board tp5 tp4 p1 c4 c5 u1 r1 c6 d2 c8 tp3 tp2 d1 c7 tp1 r4 r6 c3 r3 j1 r2 c2 c1 r5 input v+ v- p2 1 + output + + 4.000 3.800 .200 3.000 2.600 0.200 xlr connector 4-40 threaded (4 pl) standoff molex male header #22-23-2031 mating housing: molex #22-01-2037 and crimp terminal #2759 or equivalent standoff is tp6 d7 d8 d4 d3 d5 d6 circuit design ? 2003 that corporation figure 2. that1200 demonstration system outline drawing
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