Help with IC pin terminology - Page 1
Forum section: electronics / beginners

author: algorithm
author_rank: Regular Contributor
timestamp: May 16, 2020, 09:43:26 am
content: Can anybody tell me what "Peaking Capacitor" pins are?I also am unsure what "Variable" pins are referencing.I believe I understand the rest.To clarify in case its relevant, this is a dolby noise reduction IC.But no other datasheets Ive seen have "Peaking Capacitor" or "Variable" pins.I assume there are relevant/equivalent terms that Im unaware to relate.I had guesses, but figured I should ask people who actually know. haha.I want to know whats intended to connect to those 4 respective pins.Thanks in advance.& Sorry if this is a "How does X work" topic, but Im not sure of a better place to post this, as its not a repair. & My ignorance is a sign of a "beginner".Just looking for insight or answers.

author: Cubdriver
author_rank: Unknown
timestamp: May 16, 2020, 07:07:41 pm
content: Can you tell us the part number, or link to a data sheet for the device? That information is likely in there, though it may not be immediately obvious. Without seeing it, we probably can't be much help.-Pat

author: amyk
author_rank: Super Contributor
timestamp: May 16, 2020, 09:26:31 pm
content: Searching for that phrase reveals NJM2063AM as the possible part,along with some schematics showing its use.See also:http://www.ic72.com/pdf_file/-/88147.pdfhttp://www.ti.com/lit/an/snoa670c/snoa670c.pdf

author: algorithm
author_rank: Regular Contributor
timestamp: May 17, 2020, 05:59:55 am
content: Yes, amyk is correct, its an NJM2063https://pdf1.alldatasheet.com/datasheet-pdf/view/7240/NJRC/NJM2063.htmlI guess I should have mentioned that in OP, but was just focused on those 2 sets of pins.As you might see the datasheet available is pretty lacking. I guess they didnt want people knowing much about the pinout. lolQuote from: Cubdriver on May 16, 2020, 07:07:41 pmQuote from: amyk on May 16, 2020, 09:26:31 pmThank you. Ok, so looking at the wm ex356 service manual, it looks like variable pins 7/10 are connected to "Mix IN"."Peaking Capacitor" pins 5/12 are going to "Min-Max" through flex? and "Pre-Out" respectively?Or would pin 5 be going through to pin 19 of LA4582 "H.P.1"?(which I couldnt actually find what H.P. stood for as the datasheet didnt have a description on pinout) (I assume Head.Playback.1 ?)Looking at the snoa670c and various other dolby schematics, it seems "peaking capacitor" might be in reference to peak detection?But I also read most cassette players have a "peaking capacitor" across the playback head?Looking at the datasheet for LM1112 it has pins labeled as "Variable Impedance Control".Datasheet for NE5241 has "VARZ 1 & 2" pins, "Variable Impedance" for 2 channels. but also has a pin for "Variable impedance reference resistor".Looking at the service manual for Walkman Wm EX55, it has peaking capacitor pins both going to 0.047uf caps then to "Pre GND" on LA4581M. but pin 12 also seems to wrap back down to pin 13 on njm2063 "Monitor Out 1".So amyk, how do the peaking capacitor and variable pins correlate to the pins for CXA15XX you linked?Thanks again.

author: helius
author_rank: Super Contributor
timestamp: May 17, 2020, 07:57:18 am
content: A peaking capacitor is used to de-tune a resonant circuit so it does not enter self-oscillation as easily as it would otherwise. This can be needed in some sensitive amplifier circuits, such as with magnetic tape heads. Magnetic tapes are recorded with "bias", a strong, fixed frequency or tone above the audible range. This bias would overload the amplifier if it was not suitably damped.I'm sorry that I don't know about your other questions.

author: algorithm
author_rank: Regular Contributor
timestamp: May 18, 2020, 03:26:43 am
content: Quote from: helius on May 17, 2020, 07:57:18 amThank you for the informative response. Its ok.Looking at the WM-EX356 service manual again, I noticed MM1038 IC has pin 7 labeled as "P.C.".Could that be for "Peaking Capacitor" I wonder? The ic is for driving a motor though afaik.Still oblivious as to what pins on the CXA1553 ic amyk linked are relative to peaking or variable though...& Maybe they arent. the CXA IC claims to require fewer external parts.Maybe the NJM2063 requires those mysterious pins while the CXA doesnt need/use them?I mean vref isnt the same as iref is it?Maybe my questions are in futility. But hoping someone who knows could clarify.

author: magic
author_rank: Super Contributor
timestamp: May 18, 2020, 08:46:28 am
content: What are you actually trying to do with this chip?

author: algorithm
author_rank: Regular Contributor
timestamp: May 18, 2020, 01:08:00 pm
content: Quote from: magic on May 18, 2020, 08:46:28 amWell I cant do much without understanding, but I want to add dolby c nr, which if I could match those pins I asked about with the cxa1553 pinout I could.& Maybe matching them isnt necessary, but I imagine they are there for a reason.But just those 4 pins are mysterious to me, I know how to hook the rest up by comparing.