CEM3345

CEM3340 CES | Alldatasheet

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Voltage Controlled Oscillator The CEM 3340 and CEM 3345 tiple control voltages to be Psion cues i Nes ace ae are completely self contained, mixed within the device itself. oO a oe precision voltage controlled Also included is provision for | 52), a oe a oscillators, featuring both ex- hard and soft synchronization of 353 Re ce ponential and linear contro! the frequency, and an output ce + Ea es scales and up to four buffered for easy adjustment of high fre- aS Be Pe pS output waveforms: triangle, quency tracking. Special care in & aL a a sawtooth, square, and pulse with __ the design ensures oscillation aS 1] Yi ao L voltage controllable pulse width. start-up under any power-on Lei \\ a att Full temperature compensation _sequence and supply conditions. | ENR NIP al Pe makes these VCOs extremely Although a low voltage pei eae? a be stable, and eliminates the need process has been used to reduce ae 45S b ale oi! “lee ae for a temperature compensation _die size, cost, and leakage cur- eae MSD Re ne resistor. The highly accurate rents, an on-chip 6.5 volt zener BESO inice Bea. ss aeieee eeeene exponential and linear control diode allows the device to fe ck eee ne Sg. ten oe inputs are virtual ground operate off +15 volt supplies, ee summing nodes, allowing mul- as well as +16,-5 volt supplies. “water LUST ane ae CEM 3340 Circuit Block and Connection Diagram ee Features . wear FM ad yu. “sv paid 50,000:1 min. ws yoy xs baiaad ov YN wut @ Fully Temperature 83 838 m Sfky Compensated; No Q81 ame = _ cr | Resistor Required ow uk IH = Four Output Waveforms our iia banal _ Available; No waveform T [Yo Mn To ME To To rd ud wd 20 vatian'e; ‘ = ow T_T trimming required. pS [o> B Summing Node Inputs for N7 \\Ja2 Frequency Control “ Za High Exponential Scale | PRECISION i Te Bs) Accuracy ro? LTIPLTER ~, RI ia view |) c 2 2 2 g ® Low Temperature Drift ~ a3 B Voltage Controlled Pulse ES AW Te Width Ea (er) Gl SAW, @ Hard and Soft Sync Inputs vy, ay — ® Linear FM Ju a a es @ Buffered, Short Circuit TO TO wm Pie) tO he) sO Protected Outputs OF +} ® +15 Volt Supplies 7 a ax stack | 10K s12v Pav “ CNTL, SYNC, WooF Ww = SCALE ADJ.

Electrical Characteristics Application Hints : Since the device can withstand i no more than 24 volts between Exponential Scale Error, Untrimmed? - 0.2 1 % been provided to allow the i Exponential Scale Error, Trimmed? ~ 0.05 03 % chip to operate off virtually any i Multiplier Gain Error2 - 0,0005 0.008 eA negative supply voltage. If the { Tempo Cancellation -150 0 +150 ppm | negative supply is between -4.5 i Oscillator Drift4 - 450 +200 ppm | and -6.0 volts, it may be con- ~ nected directly to the negative Triangle Buffer Input Current - 03 3 A | supply pin (pin 3). For voltages j Triangle Waveform Upper Level 485 5.0 5.15 v greater than -7.5 volts, a series i Triangle Waveform Lower Level 15 0 5 mV | current limiting resistor must Triangle Waveform Symmetry 45 50 55 % be added between pin 3 and { Sawtooth Waveform Upper Level 04 10.0 106 Vv the negative supply, Its value is Sawtooth Waveform Lower Level 25 0 +25 mv | calculated as follows: j Triangle Output Sink Capability 400 550 750 uA Ree = (Vee - 7.2) / 008 Sawtooth Output Sink Capability 640 800 1000 uA Although the circuit was de- Triangle & Sawtooth Output Impedance> 65 100 150 Q signed for a positive supply of Pulse Output Source Capability at +10V 28 35 46 mA +15 volts, it may be operated Squarewave Output Levels8, CEM 3345 48-04 -13,0 -0.8,404 v anywhere betweor a0 and 118 : _ volts. The only effect is on the PWM Input Pin Current? / 6 15 35 BA positive peak Ymnplitude Of the i PWM Input Voltage for 0% Pulse Width “15 0 15 ™ | Qutput waveforms in accordance PWM Input Voltage for 100% Pulse Width 46 5.0 54 v to the following: The triangle H Input Bias Current at Reference and peak is one third of the supply, i Control Current Inputs 80 200 400 nA the sawtooth peak is two thirds Tempco of Input Bias Currents -1000 0 +1000 ppm of the supply, and the pulse Offset Voltage at Reference and Control peak is 1.5 volts below the Current Inputs 5 0 +5 mV supply. Hard Syne Reference Voltage -2.3 25 -2.8 v . Positive Supply Current 4 5 65 mA "vy . . Positive Supply Voltage Range +10 H8 v The exponential generator is Negative Supply Voltage Range® 4S -18 v unipiving there ee J . into the frequency control pin ; Note 1: This error represents the percentage difference in scale factors (volts per frequency {pin 15 on the CEM3340, pin ratio) of the exponential generator anywhere over the exponential generator current 17 on the CEM3345) times a range of 50nA to 100A. Most of this error occurs at the range extremities, coefficient directly proportional Note 2: This error represents the percentage difference in multiplier gains at any two input cur- to the absolute temperature. rents, within the range of 20 uA to 180 WA, per uA difference between the two As this control current is applied ; corresponding outputs, to the exponential generator, Note 3: This spec represents the difference between the actual tempco of the multiplier output its coefficient cancels that of the voltage (expressed relative to the maximum output excursions) and the tempco required exponential generator, q/KT. I to precisely cancel the tempco of the exponential scale factor (q/KT). This coefficient is produced by i Note 4: The multiplier output is grounded. the tempco generator using the { Note 5: For exponential generator currents less than 10 #A; above 10 A, impedance drops to same mechanisms that create it 1/3 this value as the highest current is approached, in the exponential generator: i Note 6: With respect to the hard sync input reference voltage. cancellation is therefore nearly i Note 7: For PWM control inputs between ~1 and +6 volts. This current is significantly greater perfect. i for inputs outside of this range. The output of the precision Note 8: Current limiting resistor required for negative supplies greater than -6 volts. multiplier (pin 14 on the 3340, 3 2 E

pin 16 on the 3345) internally i connects to the control input Voltage Between Vcc and Veg Pins +24V,-0.5V of the exponential generator Voltage Between Vcc and Ground Pins +18V, -0.5V ; tone OE Thus output isa Voltage Between Veg and Ground Pins -6.0V,#0.5V Voltage Between Frequency Control Pin _ 22Vy or Reference Current Pin and Ground Pin +6.0V | lom =—— (1 -I¢Rz/3.0) i Ry Voltage Between Multiplier Output Pin i and Ground Pin +6.0V, -1V i ea. Tw la eithe Current through Any Pin £40mA total current flowing into the Storage Temperature Range ~55°C to +150°C : frequency control pin and must . 0 0, remain pesitive for prover Operating Temperature Range -25°C to +75°C i operation (a negative input current will produce the same | . . ‘ output as a zero input current). CEM 3345 Circuit Block and Connection Diagram i Since the frequency control input pin is a virtual ground eure eur summing node, any number of ay av VAN sort control voltages may be summed wll oul TP w ame. simply with input resistors to woe 32 3085 1m S 1.8m this pin. Rg our) = cr a The current output of the 4702 +18v uk We 7000p o0.F multiplier is converted to the OF an required drive voltage with a Toss pee ee ee resistor from the multiplier > Pr re { output pin to ground. For V7 GV (2) > greatest multiplier accuracy, Thea 1 this resistor, Rg, should be 1.8k we aS ox and the current flowing out 1) (.* ial of pin 2, 22V7/Rr, should be view close to the current flowing ZX Y7 Ta } out of pin 1, 3.0/Rz. oF f Since the components asso- oe (en) rt VY ciated with the tempco generator i io, and multiplier determine the : po $—}— —_ + 1-3 possible at the base of Qy, they 2 1 one FAEo. should be selected to provide the oak nee Nay pa woe aE nay | desired frequency control range . Rg sau carl, <4 Sy H of the oscillator. The exponen: me] | iG wor Te sry i w/ | tial generator itself is capable of sone avo wan aw delivering a current for charging ADs src. and discharging the timing ——" : capacitor from greater than H .5mA down to less than the Cr, the timing capacitor. The itor, such as mica, should be input bias current of the buffer, oscillation frequency is given by: used for Ce). thus allowing for a typical fre- = C, Next the reference current i quency range greater than F=Sleg/2Voc Cr) for the exponential generator 500,000:1. The most accurate where leg is the output current (Current into pin 13 on the | portion of this current range, from the exponential generator. 3340, pin 15 on the 3345) is from 50nA to 100A, should be If, for instance, the most impor- _ selected. This current ideally i used for the most critical portion tant frequency range is from should be the geometric mean i of the desired frequency range. 5Hz to 10kHz, then Ce should of the selected generator current Hl Consideration of this critical be 1000pF at Veg = +15V (a range, but consideration of i range determines the value of low leakage, low tempco capac- the temperature coefficient of i 3 : i

the bias current for op amp A2 usually dictates a higher value POSITIVE HARD SYNC. NEGATIVE HARD SYNC. i for the reference current. Al- 4, : though this bias current has g5 i been temperature compensated, ES gy it could have a worst cast POSITIVE AND NEGATIVE HARO SYNC. tempco of 1000ppm and maxi- zt mum value of 400nA. Under 4 these conditions, a reference 33 current of 104A through Qy, v j for instance, would have a wav i tempco of 40ppm. It is recom- 3B mended that, in general, the 25 réference current be selected in wv the 3uA to 154A range. { Since the reference current 35 i pin is a virtual ground summing a2 : node, the reference current may be set up with a temperature Froune +: outeur waveronus | stable resistor to Voc, or other positive stable voltage source. quency at some initial value is best accomplished by bypass- A negative current into this pin with no control voltages applied. ing Rg to ground with a capac- will simply gate the exponen- The frequency control scale —_itor, where the corner rolloff i tial generator completely off. is determined by the value of frequency is given by: fip = With the value of Ce and the input resistor to the control —_1/(27RgC). reference current now selected, pin, the value of the Q, base the voltage excursion at the resistor, Rg, and the multiplier . + muttiplier output, which drives current gain. Since the multiplier rimming The Scale the base of Qy, is now deter- current gain, set by the ratio of mined for the desired frequency the pin 2 current to pin 1 cur- There are two basic sources control range. If this range were rent, should be near unity and producing exponential con- i 1Hz to 20kHz, the exponential "Re should be 1.8K, the control __formity error in the control i generator current, leg, would input resistor is the component _ scale: One is the exponential } have to range from 10nA to which should be selected for the —_current generator and the 200)1A in the above example, desired control scale. For the other is the precision multiplier. requiring the base drive voltage, industry standard scale of 1 The error from the exponen- Vp, to vary from +180mV to octave/volt, the input summing _tial converter is due partly to the | ~78mV, since resistors become 100k. The bulk emitter resistance of Qp, leg = Ince o7¥8/VT recommended method for becoming significant at gener- EG © UREF trimming the control scale is ator currents greater than 100A, The most positive voltage at to tweek the multiplier current and partly to the comparator H the base of Qy occurs when the gain by adjusting the value of switching delay, becoming sig- H control current, Ic, is zero, and Rz £20% about the nominal nificant at frequencies greater is 22V7 Rg/Ry. Therefore, in value, than 5KHz. These two effects the above example, Rt = 22Vy- Both the multiplier and the cause the oscillator frequency ‘ 1.8K/.18V = 5.72K, and Rz = exponential generator are com- to go flat, but only at the 4 3.0R-7/22V7 = 30K nominal. pensated with the 470 -.01uF — uppermost octaves. ‘ Finally, since the multiplier networks shown in the Block Circuitry has been provided ; output current must range from Diagrams and are therefore to correct for these effects. The +100HA to -43yA to produce necessary in any application. output of the hi-frequency i this desired voltage excursion at Since the bandwidth of the track pin (pin 7 on the 3340, i ‘the multiplier output and on the multiplier extends beyond the pin 8 on the 3345) is a current base of Qj, the control input audio range, it may be desirable which is one fourth the gen- i current, Ic, ranges from 0 to to limit the bandwidth to re- erator output current, leg. 143A. A resistor from Voc to duce possible noise at the base This current may be converted } the control input pin may be of Qy, thereby reducing FM with a grounded resistor toa i used to set the oscillator fre- noise and frequency jitter. This voltage, a portion of which is i 4 i

me SSSSSSSSSSSSSSsSssseseeee EE then fed back to the control octave, the scale factor could be Qoanoo00 3 : input pin. As the frequency is 0.4% different worst case, pro- i . increased, this feedback voltage ducing a volts/octave error of b wom | i will tend to sharpen the control 0.4% x 18mV = 72yV. This fifth a ‘ scale, but only at the upper octave would thus be 0.28% end, since the feedback voltage (5 cents) sharp or flat. Note that * j becomes significant only at if octaves above the adjusted nv | the higher generator currents. octaves were sharp, those Mw 12K ov { The amount of voltage fed octaves below the adjusted i . back is adjusted so the scale octave would become increas- = : is sharpened just enough to ingly flat, and vice versa. noo 0 0000 H compensate for the inherent Typically the error produced cena : high end flatness by the multiplier is much less P, The method recommended __ than the above example. How- TOUS UT TO : for trimming the control scale is__ ever, if maintaining a tighter 3.9K: DI ‘ as follows: The hi-frequency tolerance is required for the Ve ree . track adjust is first set so that particular application, the mul- > : no correction voltage is fed to tiplier error may be trimmed out " 12K votTase i the control input. The oscilla- for each device. The trimming Love Steve" : tor frequency is set around procedure requires that both Rz ~ : 200Hz and the scale adjust and Rg be made adjustable FIGURE 2: CLAMPING PULSE UPPER LEVEL : trimmer is adjusted for the 30% about the nominal value; desired scale factor (e.g. 1.000 Rz is first adjusted so that the could lower the frequency by octave/voit), Then the oscillator Multiplier gain is constant over 150/100K = 0.15% (2.5 cents} i frequency is set to around the selected input current worst case. A load capacitance 10KHz, and the hi-frequency range; then Rg is adjusted for will act like a resistor with a track trimmer is adjusted for the _ the desired scale factor (adjust- value 1/(2fC,) and requires the . same scale factor. ing Rg will reintroduce some same considerations as above. \\ The source of error from the error, so Rz may have to be A continuous load no greater b : precision multiplier is due to the Teadjusted). than 10K and/or 1000pF to : multiplier’s gain (nominally Should for some reason it be —_ ground is recommended. : unity) changing as the control desired not to use the tempera- Since the sawtooth output : input current changes. This type ture compensation circuitry, the __ is buffer isolated from the . of error causes the frequency to‘ multiplier/tempco generator oscillator circuitry, it can sink become increasingly sharp or flat May be bypassed simply by at least .6mA and source over 1 as the control current is in- leaving pin 1, pin 2, and the several mA with no effect on : creased, The percentage differ- control input pin open, and oscillator performance, and only H t ence in multiplier gains, and applying the control voltage to. —_ negligible effect on sawtooth ' hence scale factors, at any two the base of Qy via the multiplier — waveshape. Stray capacitance at i . inputs to the multiplier may be output pin. this output greater than 40pF, ‘ calculated as the percentage however, will cause a small high i ‘ error given in the specifications Waveform Outputs frequency oscillation. A 1002 : times the difference in uA All waveform outputs are short- _ resistor between the output and ‘ between the two corresponding _ circuit protected and may be load is all that is required to i outputs. For example, suppose shorted continuously to any isolate more than .01uF. 1 the scale were adjusted for supply without damaging the precisely 1 octave/volt at mid- device. Each output, however, i range. At one octave above this has differing drive capabilities. 9-0-0-0-0-0-9.-0 i : adjusted octave, with the mul- Although the triangle output b ‘ tiplier output 10uA different, can sink at least .4mA and i the scale factor could be .08% source over several mA, care TOTP eT oS i ; different worst case. This must be exercised in loading ruse neu i A would produce a volts/octave this output. Becatise the output our wok" o-sv i error at the base of Qy of .08% has a finite impedance and aK m i i x 18mV = 14.4uV, which would drives the comparator, a change j cause this octave to be .06% in toad will change the frequency = : t (1 cent) sharp or flat. At five of the oscillator. Adding a 100K FIGURE 3: ADDING HYSTERESIS TO PULSE SHAPER. octaves above the adjusted resistor to ground, for instance, 5 i

a oonaon to finite comparator gain. It 3 volts maximum for best ° may be speeded up considerably operation. b cme | by adding hysteresis as shown in Another method of hard — Figure 3. Care should be exer- synchronizing the oscillator is 5 ro and insta cised in the layout to prevent shown in Figure 5. Negative vee yy Dt stray capacitive coupling be- pulses only are coupled into the 10: tween the pulse output and base of the PNP transistor, with ut ony” the PWM input,as this can cause —_a peak amplitude of 8 to 10 isy POSITIVE NEGATIVE = comparator oscillation. volts for best results at Voc = SYNC ‘Sync The square wave output (pin +15V. This method will produce Woven) (even) 7) from the CEM 3345 also the same waveforms generated FIGURE 4: METHOD FOR SYNC OW RISING OR FALLING EDGE. "requires a pull down resistor to by the conventionally syn- any negative supply greater chronized sawtooth oscillators. The pulse output is an open than -4 volts, It provides an Finally, the oscillator may NPN emitter, and therefore output swing from nominally be soft synchronized by negative requires a pull-down resistor to 1.3 volts below the hard sync pulses applied to the threshold ground or to any negative reference voltage to a level voltage pin (pin 9 on the 3340, voltage. Any pull-down voltage nominally the same as the hard pin 10 on the 3345). These . between ground and .5 volt sync reference voltage. The pulses cause the triangle upper above the voltage on the negative Block Diagram shows a con- peak to reverse direction pre- supply pin will precisely deter- venient way of generating a maturely, causing the oscillation mine the lower level of the full swing square wave from period to be an integral multiple pulse wave. For pull-down this output. The current pulled of the pulse period. The peak voltages more negative than this, down from this output should amplitude of these negative the lower level will be nearly also be limited to a maximum pulses should be limited to 5 the negative supply pin voltage. of 3mA. volts maximum and positive The nominal upper level of the or pulses should be avoided en- pulse wave is given by: Voc - Frequency Synchronization tirely. If this input is not used 0.3V -1.3K = Ipp for!pip > ‘The oscillator frequency may be _ for synchronization purposes, it 0.6mA, and Vcc ~ 0.9V for hard synchronized in several is recommended that it be by- IpLp<0.6mA, where Ip_p is the different ways. One way is to passed with a 0.1uF capacitor pull down current. A maximum couple positive pulses, negative to ground to prevent synchroni- value of 3mA for Ip_p is recom- pulses, or both, into the hard zation or jitter to noise pulses mended. For those applications sync input pin (pin 6 on the ‘on the Ve¢ supply line. which require a more stable, well 3340 and 3345). A positive . EM defined upper level, the circuits sync pulse will cause the triangle Linear shown in Figure 2 may be used. —_ wave to reverse directions only —_—The reference current input The pulse width of the pulse during the rising portion of the pin may be used for linear output may be set from 0 to triangle, while a negative sync modulation of the frequency. 100% with a 0 to +5V external pulse will cause direction reversal The external input is summed voltage (Vec = +15V) applied only during the falling portion, __ with the reference current to the PWM control input pin” The resulting waveforms are simply through a resistor ter- (pin 5 on the 3340 and 3345). shown in Figure 1, and provide a_—_minating at this pin. For audio The fall time of the pulse wave wider variety of synchronized FM, it is recommended that a is slower than the rise time due sounds than possible through coupling capacitor be used to conventionally synchronized prevent frequency shift when From a oscillators. Simple capacitive connecting to the external SAWTOOTH > vv; coupling as shown in the Block source. The value of the input OsTPUTOF Diagrams allows hard synchron- _ resistor should be selected so that Conse THINS ization on both the rising and the maximum peak to peak input Eau. am falling edge of a rectangle wave. signal produces a plus and minus our. Figure 4 shows circuitry for current equal to the reference pooooone |... allowing only one or the other current. ) T of the edges to synchronize the = oscillator. The peak amplitude TTTTUUTO of the pulses actually appearing FIGURE S: CONVENTIONAL HARD SYRC on the sync pin should be re- stricted to 1 volt minimum and CURTIS ELECTROMUSIC SPECIALTIES Curtis Electromusic Specialties (CES}assumes no responsibility for use of any circuitry described. No circuit licenses are implied. CES reserves the right, at any time without notice, to change said circuitry. Printed U.S.A. © 1980 6 :