CEM3365 CES | Alldatasheet

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: CURTIS ELECTROMUSIC SPECIALTIES CEM3365 FAST DUAL DAC MULTIPLIER Preliminary, November 1985 .

Description

The CEM 3365 is a dual high speed one quandrant multiplier intended to scale the output of fast bipolar DACs in digital audio applications. Each half of the 3365 contains a very fast op amp and a high speed current input / current output gain cell . whose gain is controlled by the output of the op amp; a full scale multiplication with settling of the cell output to 12 bits can occur in 158 ns (2@@ ns max.). This response is in contrast to the many microseconds which would result from changing the reference input of even the fastest bipolar multiplying DACs. As both inputs and output of the op amp are externally available, two modes of operation are possible. One is to configure the op amp as the current-to-voltage converter of a second bipolar . control DAC, so the gain may be controlled directly by a data word. Effective resolution of the result is the sum of the resolutions of the two DACs (24 bits for two 12 bit DACs). The second mode is to configure the op amp simply as-a voltage follower, allowing the gain to be controlled by a voltage (from a Sample and Hold, for instance). Although the input to the gain cell is limited to a unipolar : current, the output may be made bipolar simply by connecting a properly valued resistor from the op amp output to the gain cell output. Additional versatility is provided by the reference voltage pin, which accurately sets the op amp output voltage required for maximum gain. A typical application for the 3365 would be to control the 7 amplitude of digitally generated audio signals in a multiplexed system. When used in conjunction with a CEM 5519 Fast Octal Sample and Hold, for instance, 8 channels of digital audio with individual amplitude control and 24 bits resolution can be produced in less than 2 uS (598 nS per channel). Fast, flexible, and requiring few support components, the CEM 3365 offers an inexpensive alternative to the high speed hardware digital multipliers required in multiplexed digital audio systems.

Features: | o Fast multiplication of bipolar DAC outputs: setting to .825% of input in < 208 ns © Gain controllable by another DAC or by a voltage © Two independent multipliers in a single 14 pin DIP” : © Adjustable voltage level required for maximum gain . o Unipolar or bipolar outputs ‘

. To From DAC TO OP AtAP SI6NAL DAC REFERANCE or - sob O~ 2mA GRIN CV, O TO+SV : . H12N [se ] | re | I4 13) i2| i lo q 8 eal C7 ro aml | Vt — i BIAS | ; . CA REF + | Lo | Co I A 2 3 4 Ss 6] 7 { ; GND) Tog} Tinal Voal -/NA} tal Vee = Sk | 2.5K “~ -sv TO op AMP | On i E510 To From To From SIGNAL DAC contre. DAC O- 2mA O- 2A CEM336S Fast DAC MULTIPLIER ; 10 [8S . |

APPLICATION IDEAS - CRS ! Generating 8 Channels of Digital Audio with Individual Envelope f Control on Each Channel lok INH | Veer = +5V : = + 7 RF i VREer cH.Gg ¥ 3 & 8 ee ° < —-|--—- . i wave Form ray in VREF 1 “1s to | eH. 3 : DATA b | bo Les cHa | Bes fw > Inu & en S | ; a on by i) cH. 6 ~ 9 ' ¥ 24 CHT —__! 1m I 4 eu oo T l= ! as ‘ tok | 1g = : t xv = 1 ne Veer LL ¥ Io 4 y = ENVELOPE a = bata D | / b : o i WAVE FORM, —— i x Bara XXX ENVELOPE x | DATA _ XX eg ADS6G ADDRESS We AM 6012 INH ee eee ee Gee This approach requires special hardware to update both DACs : (simultaneously) every 500 ns (for maximum throughput) :

Generating 8 Channels of Digital Audio with Individual Envelope Control on Each Channel Veer = +SV INH lok fit r Lens = vic —ers CH. I + r--lan-74 Sige su | s CH. 2 Veer , _ er 1 SN IE Sto G CH. 3 wy < To : Inv iy Fee Ss AVE FORM Ve. | Vv iS) e CH. G cate pn | I | 2x 3u cH.7 oe | \\e “ ABC s] b'S De = is} % FAST BIPOLAR = 3 we /\\ I e295. ADS66 | | AM 6ol2 fee | 1 {i/o a a Veer - 4651 ic} & y L YO YLYZ 3 ¥4 Ys Yo7C} c ENVELOPE Ss AND OTHER INH PARAMETER, b OG O} O2 03 OF OS 06 07 DATA iv) do A, lo a + xv g CEMSS360 4, a ? Vine Ag Ae & CMOS TYPE OR As fis 2.4, ADTS 41 CEM55@8B Da ba DAC (218

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TO OTHER V.C. PARAMETERS 2-9 V.C.F FREQUENCY & RESONANCE Advantage of this approach is envelope and parameter data needs updating only once every 1 - 10 mS.