NE/SE DESCRIPTION The NE/SE is a versatile, high guaranteed frequency phase-locked loop designed for operation up to 0MHz. As shown in the Block Diagram, the NE/SE consists of a VCO, limiter, phase comparator, and post detection processor. PIN CONFIGURATIONS D, N Packages V+ TTL OUTPUT FEATURES Operation with single V supply TTL-compatible inputs and outputs Guaranteed operation to 0MHz External loop gain control Reduced carrier feedthrough No elaborate filtering needed in FSK applications Can be used as a modulator Variable loop gain (externally controlled) APPLICATIONS High speed modems FSK receivers and transmitters Frequency Synthesizers LOOP GAIN CONTROL INPUT TO PHASE COMP FROM VCO LOOP FILTER LOOP FILTER FM/RF INPUT BIAS FILTER GND Signal generators Various satcom/tv systems pin configuration 0 9 TOP VIEW HYSTERESIS SET ANALOG OUT FREQ. SET CAP FREQ. SET CAP VCO OUT V+ Figure. Pin Configuration VCO OUT TTL SR00 ORDERING INFORMATION DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG # -Pin Plastic Small Outline (SO) Package 0 to +0 C NED SOT09- -Pin Plastic Dual In-Line Package (DIP) 0 to +0 C NEN SOT- -Pin Plastic Dual In-Line Package (DIP) - to + C SEN SOT- BLOCK DIAGRAM V + LIMITER 9 0 PHASE COMPARATOR VCO AMPLIFIER DC RETRIEVER POST DETECTION PROCESSOR SCHMITT TRIGGER Figure. Block Diagram SR00 99 Aug -090 0
NE/SE ABSOLUTE MAXIMUM RATINGS SYMBOL PARAMETER RATING UNITS V+ Supply voltage Pin Pin 0 I OUT Sink Max (Pin 9) and sourcing (Pin ) ma I BIAS Bias current adjust pin (sinking) ma P D Power dissipation 00 mw T A Operating ambient temperature NE 0 to +0 C SE - to + C T STG Storage temperature range - to +0 C NOTE: Operation above V will require heatsinking of the case. DC AND AC ELECTRICAL CHARACTERISTICS V CC = V; T A = 0 to C; f O = MHz, I = 00µA; unless otherwise specified. LIMITS LIMITS SYMBOL PARAMETER TEST CONDITIONS SE NE UNITS MIN TYP MAX MIN TYP MAX Maximum VCO frequency C = 0 (stray) 0 0 MHz V V Lock range Input > 00 T A = C T A = C T A = - C T A = 0 o C T A = 0 C 0 0 0 0 0 0 0 0 0 0 % of f O Capture range Input > 00, R = Ω 0 0 0 0 % of f O VCO frequency drift with temperature VCO free-running frequency VCO frequency change with supply voltage Demodulated output voltage f O = MHz, T A = - C to + C T A = 0 to +0 C = 0 to +0 C f O = MHz, T A = - C to + C T A = 0 to +0 C C = 9pF R C = 00Ω Internal 00 00 00 00 00 00 PPM/ o C.. MHz V CC =.V to.v % of f O Modulation frequency: khz f O = MHz, input deviation: %T = C %T = C %T = 0 C %T = - C %T = 0 C %T = C Distortion Deviation: % to % % S/N Signal-to-noise ratio Std. condition, % to 0% dev. 0 0 db AM rejection Std. condition, 0% AM db Demodulated output at operating voltage Modulation frequency: khz f O = MHz, input deviation: % V CC =.V V CC =.V I CC Supply current V CC = V I, I 0 0 0 ma 0 Output output leakage current 0 output voltage V OUT = V, Pins, 9 I OUT = ma, Pins, 9 I OUT = ma, Pins, 9 0. 0. 0 0. 0. 0. 0. 0 0. 0. µa V V 99 Aug
NE/SE TYPICAL PERFORMANCE CHARACTERISTICS 000 Lock Range vs Signal Input INPUT SIGNAL LEVEL mv 00 I PIN = 0 0µA I PIN = 0µA CAPACITANCE pf 0 0 0 0 0 0 VCO Capacitor vs Frequency V CC V f o = MHz. 0 0 0 0 0 FREQUENCY khz 0 0. 0. 0.9.0... NORMALIZED LOCK RANGE Typical Noirmalized VCO Frequency as a Function of Pin Bias Current Typical Noirmalized VCO Frequency as a Function of Pin Bias Current Typical Noirmalized VCO Frequency as a Function of Temperature NORMALIZED VCO FREQUENCY.0.00 0.99 0.9 0.9 0.9 FREQUENCY: 0MHz NORMALIZED VCO FREQUENCY.0.0.00 0.9 0.90 VCO FREQUENCY: 0MHz NORMALIZED VCO FREQUENCY.0.0.00 0.9 0.90 BIAS CURRENT: 00µA FREQUENCY: MHz FREQUENCY: 00MHz BIAS CURRENT: 00µA 00µA 00 00 0 +00 BIAS CURENT (µa), PIN 00µA 00 00 0 +00 +00 BIAS CURENT (µa), PIN 0 0 0 00 TEMPERATURE (IN o C) Figure. Typical Performance Characteristics SR00 99 Aug
NE/SE TYPICAL PERFORMANCE CHARACTERISTICS (Continued) V D PHASE COMPARATOR S OUTPUT VOLTAGE IN mv 00 00 00 I BIAS = 00µA I BIAS = 00µA I BIAS = 00µA I BIAS = 0µA f o =.0MHz VCO FREQUENCY IN MHz.. I BIAS = 00µA I BIAS = 00µA 00. 00 0 0 00 0 0 0 0 PHASE ERROR IN DEGREES 0 00 00 00 00 00 00 V DIN mv. 00. 00 00 Variation of the Comparator s Output Voltage vs Phase Error and Bias Current (K D ) Figure. Typical Performance Characteristics (cont.) VCO Output Frequency as a Function of Input Voltage and Bias Current (K O ) SR00 TEST CIRCUIT +V R K R INPUT C 0.µF K 0 9 pf 90 VCO OUYPUT DEMODULATED C C 0pF R 0pF R 0.µF C OUTPUT Figure. Test Circuit SR009 99 Aug
NE/SE FUNCTIONAL DESCRIPTION (Figure ) The NE is a monolithic phase-locked loop with a post detection processor. The use of Schottky clamped transistors and optimized device geometries extends the frequency of operation to greater than 0MHz. In addition to the classical PLL applications, the NE can be used as a modulator with a controllable frequency deviation. The output of the PLL can be written as shown in the following equation: V O = (f IN - f O ) K VCO () K VCO = conversion gain of the VCO f IN = frequency of the input signal f O = free-running frequency of the VCO The process of recovering FSK signals involves the conversion of the PLL output into logic compatible signals. For high data rates, a considerable amount of carrier will be present at the output of the PLL due to the wideband nature of the loop filter. To avoid the use of complicated filters, a comparator with hysteresis or Schmitt trigger is required. With the conversion gain of the VCO fixed, the output voltage as given by Equation varies according to the frequency deviation of f IN from f O. Since this differs from system to system, it is necessary that the hysteresis of the Schmitt trigger be capable of being changed, so that it can be optimized for a particular system. This is accomplished in the by varying the voltage at Pin which results in a change of the hysteresis of the Schmitt trigger. For FSK signals, an important factor to be considered is the drift in the free-running frequency of the VCO itself. If this changes due to temperature, according to Equation it will lead to a change in the DC levels of the PLL output, and consequently to errors in the digital output signal. This is especially true for narrowband signals where the deviation in f IN itself may be less than the change in f O due to temperature. This effect can be eliminated if the DC or average value of the signal is retrieved and used as the reference to the comparator. In this manner, variations in the DC levels of the PLL output do not affect the FSK output. VCO Section Due to its inherent high-frequency performance, an emitter-coupled oscillator is used in the VCO. In the circuit, shown in the equivalent schematic, transistors Q and Q with current sources Q - Q form the basic oscillator. The approximate free-running frequency of the oscillator is shown in the following equation: f O R C (C + C S ) R C = R 9 = R 0 = 00Ω (INTERNAL) C = external frequency setting capacitor C S = stray capacitance Variation of V D (phase detector output voltage) changes the frequency of the oscillator. As indicated by Equation, the frequency of the oscillator has a negative temperature coefficient due to the monolithic resistor. To compensate for this, a current I R with negative temperature coefficient is introduced to achieve a low frequency drift with temperature. () Phase Comparator Section The phase detection processor consists of a doubled-balanced modulator with a limiter amplifier to improve AM rejection. Schottky-clamped vertical PNPs are used to obtain TTL level inputs. The loop gain can be varied by changing the current in Q and Q which effectively changes the gain of the differential amplifiers. This can be accomplished by introducing a current at Pin. Post Detection Processor Section The post detection processor consists of a unity gain transconductance amplifier and comparator. The amplifier can be used as a DC retriever for demodulation of FSK signals, and as a post detection filter for linear FM demodulation. The comparator has adjustable hysteresis so that phase jitter in the output signal can be eliminated. As shown in the equivalent schematic, the DC retriever is formed by the transconductance amplifier Q - Q together with an external capacitor which is connected at the amplifier output (Pin ). This forms an integrator whose output voltage is shown in the following equation: V O = g M V () C IN dt g M = transconductance of the amplifier C = capacitor at the output (Pin ) V IN = signal voltage at amplifier input With proper selection of C, the integrator time constant can be varied so that the output voltage is the DC or average value of the input signal for use in FSK, or as a post detection filter in linear demodulation. The comparator with hysteresis is made up of Q 9 - Q 0 with positive feedback being provided by Q - Q. The hysteresis is varied by changing the current in Q with a resulting variation in the loop gain of the comparator. This method of hysteresis control, which is a DC control, provides symmetric variation around the nominal value. Design Formula The free-running frequency of the VCO is shown by the following equation: f O R C (C + C S ) R C = 00Ω C = external cap in farads C S = stray capacitance The loop filter diagram shown is explained by the following equation: f S = + src (First Order) R = R = R =.kω (Internal)* By adding capacitors to Pins and, a pole is added to the loop transfer at ω = RC NOTE: *Refer to Figure. () () 99 Aug
NE/SE EQUIVALENT SCHEMATIC Figure. Equivalent Schematic SR000 LOCK RANGE ADJUSTMENT I 0.0µF FM INPUT f O = MHz f M = khz BIAS FILTER 0.µF.0µF k LOOP FILTER 0.0µF ANALOG OUT khz POST DETECTION FILTER 0.µF 0 9 0pF f O = MHz FREQUENCY SET CAP k V V Figure. FM Demodulator at V SR00 99 Aug
NE/SE APPLICATIONS V FM Demodulator The NE can be used as an FM demodulator. The connections for operation at V and V are shown in Figures and, respectively. The input signal is AC coupled with the output signal being extracted at Pin. Loop filtering is provided by the capacitors at Pins and with additional filtering being provided by the capacitor at Pin. Since the conversion gain of the VCO is not very high, to obtain sufficient demodulated output signal the frequency deviation in the input signal should be % or higher. Modulation Techniques The NE phase-locked loop can be modulated at either the loop filter ports (Pins and ) or the input port (Pin ) as shown in Figure 9. The approximate modulation frequency can be determined from the frequency conversion gain curve shown in Figure 0. This curve will be appropriate for signals injected into Pins and as shown in Figure 9. MODULATING INPUT khz khz 0.µF.0µF V k k I 0 9 k 0pF f O = MHz FREQUENCY SET CAP FINE FREQUENCY ADJUSTMENT I LOCK RANGE ADJUSTMENT 0.0µF V MODULATED OUTPUT (TTL) Figure 9. Modulator SR00 FM INPUT f O = MHz f M = khz BIAS FILTER.0µF 0.µF.0µF k LOOP FILTER 0.0µF ANALOG OUT khz POST DETECTION 0.µF FILTER 0 9 0pF f O = MHz FREQUENCY SET CAP 00 k The lock range graph indicates that the +.0MHz frequency deviations will be within the lock range for input signal levels greater than approximately 0mV with zero Pin bias current. (While strictly this figure is appropriate only for 0MHz, it can be used as a guide for lock range estimates at other f O frequencies). The hysteresis was adjusted experimentally via the 0kΩ potentiometer and kω bias arrangement to give the waveshape shown in Figure for 0k, 00k, M baud rates with square wave FSK modulation. Note the magnitude and phase relationships of the phase comparators output voltages with respect to each other and to the FSK output. The high-frequency sum components of the input and VCO frequency also are viable as noise on the phase comparator s outputs. V Figure. FM Demodulator at V SR00 FSK Demodulation The PLL is particularly attractive for FSK demodulation since it contains an internal voltage comparator and VCO which have TTL compatible inputs and outputs, and it can operate from a single V power supply. Demodulated DC voltages associated with the mark and space frequencies are recovered with a single external capacitor in a DC retriever without utilizing extensive filtering networks. An internal comparator, acting as a Schmitt trigger with an adjustable hysteresis, shapes the demodulated voltages into compatible TTL output levels. The high-frequency design of the enables it to demodulate FSK at high data rates in excess of.0m baud. Figure 0 shows a high-frequency FSK decoder designed for input frequency deviations of +.0MHz centered around a free-running frequency of 0.MHz. the value of the timing capacitance required was estimated from Figure to be approximately 0pF. A trimmer capacitor was added to fine tune f O 0.MHz. OUTLINE OF SETUP PROCEDURE. Determine operating frequency of the VCO: IF N in feedback loop, then f O = N x f IN.. Calculate value of the VCO frequency set capacitor: C O 00 f O. Set I (current sinking into Pin ) for 00µA. After operation is obtained, this value may be adjusted for best dynamic behavior, and replace with fixed resistor value of R = V CC.V. I B. Check VCO output frequency with digital counter at Pin 9 of device (loop open, VCO to φ det.). Adjust C O trim or frequency adj. Pins - for exact center frequency, if needed.. Close loop and inject input signal to Pin. Monitor Pins and with two-channel scope. Lock should occur with φ - equal to 90 o (phase error). 99 Aug
NE/SE. If pulsed burst or ramp frequency is used for input signal, special loop filter design may be required in place of simple single capacitor filter on Pins and. (See PLL application section). The input signal to Pin and the VCO feedback signal to Pin must have a duty cycle of 0% for proper operation of the phase detector. Due to the nature of a balanced mixer if signals are not 0% in duty cycle, DC offsets will occur in the loop which tend to create an artificial or biased VCO.. For multiplier circuits where phase jitter is a problem, loop filter capacitors may be increased to a value of 0-0µF on Pins,. Also, careful supply decoupling may be necessary. This includes the counter chain V CC lines. +V k BIAS ADJ 0k 0.µF 0.µF HYSTERESIS ADJUST 0k k.k FSK OUTPUT *NOTE: Use R 9- only if rise time is critical. FSK INPUT +V 0.µF 0.µF 0Ω *0Ω k 00pF 00pF k 9 0 NE pf Figure 0. 0.MHz FSK Decoder Using the 0µF/V 0 0pF SR00 99 Aug
NE/SE SR00 Figure. Phase Comparator (Pins and ) and FSK (Pin ) Outputs BIAS ADJUST 0k +V.µF CER..µF CER. I k.µf INPUT SIGNAL f T kω.µf DET. 0 NE 9 VCO.µF *0Ω Nxf T LOOP FILTER 0Ω VCO OUTPUT *NOTE: Use R 9- only if rise time is critical. C O f = Nxf T N Figure. NE Phase-Locked Frequency Multiplier 99 Aug 9