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MAX038CPP+
High-Frequency Waveform Generator
AVAILABLE
General DescriptionThe MAX038 is a high-frequency, precision function
generator producing accurate, high-frequency triangle,
sawtooth, sine, square, and pulse waveforms with a
minimum of external components. The output frequency
can be controlled over a frequency range of 0.1Hz to
20MHz by an internal 2.5V bandgap voltage
reference and an external resistor and capacitor. The
duty cycle can be varied over a wide range by applying
a ±2.3V control signal, facilitating pulse-width modula-
tion and the generation of sawtooth waveforms.
Frequency modulation and frequency sweeping are
achieved in the same way. The duty cycle and frequen-
cy controls are independent.
Sine, square, or triangle waveforms can be selected at
the output by setting the appropriate code at two
TTL-compatible select pins. The output signal for all
waveforms is a 2VP-Psignal that is symmetrical around
ground. The low-impedance output can drive up
to ±20mA.
The TTL-compatible SYNC output from the internal
oscillator maintains a 50% duty cycle—regardless of
the duty cycle of the other waveforms—to synchronize
other devices in the system. The internal oscillator can
be synchronized to an external TTL clock connected
to PDI.
ApplicationsPrecision Function Generators
Voltage-Controlled Oscillators
Frequency Modulators
Pulse-Width Modulators
Phase-Locked Loops
Frequency Synthesizer
FSK Generator—Sine and Square Waves
Features0.1Hz to 20MHz Operating Frequency RangeTriangle, Sawtooth, Sine, Square, and Pulse
WaveformsIndependent Frequency and Duty-Cycle
Adjustments350 to 1 Frequency Sweep Range15% to 85% Variable Duty CycleLow-Impedance Output Buffer: 0.1ΩLow 200ppm/°C Temperature Drift
High-Frequency Waveform GeneratorOUT
GNDA1
GND
REF
TOP VIEW
MAX038
DV+
DGND
SYNC
PDIFADJ
DADJ
GND
COSC
PDO
GNDIIN
GND
DIP/SO
Pin Configuration
Ordering Information* Contact factory prior to design.
PARTTEMP RANGEPIN-PACKAGEMAX038CPP0°C to +70°C20 Plastic DIP
MAX038CWP0°C to +70°C20 SO
MAX038C/D*0°C to +70°CDice
MAX038
High-Frequency Waveform Generator
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, GND = DGND= 0V, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, CF= 100pF,
RIN= 25kΩRL= 1kΩ, CL= 20pF, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
V+ to GND ...............................................................-0.3V to +6V
DV+ to DGND...........................................................-0.3V to +6V
V- to GND.................................................................+0.3V to -6V
Pin Voltages
IIN, FADJ, DADJ, PDO.....................(V- - 0.3V) to (V+ + 0.3V)
COSC ......................................................................+0.3V to V
A0, A1, PDI, SYNC, REF.............................................-0.3V to V+
GND to DGND ...................................................................±0.3V
Maximum Current into Any Pin ........................................±50mA
OUT, REF Short-Circuit Duration to GND, V+, V- ..................30s
Continuous Power Dissipation (TA = +70°C)
Plastic DIP (derate 11.11mW/°C above +70°C) .........889mW
SO (derate 10.00mW/°C above +70°C).......................800mW
CERDIP (derate 11.11mW/°C above +70°C)...............889mW
Operating Temperature Ranges
MAX038C_ _ ......................................................0°C to +70°C
Maximum Junction Temperature ....................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
FREQUENCY CHARACTERISTICSMaximum Operating FrequencyFoCF ≤ 15pF, IIN = 500µA20.040.0MHz
VFADJ = 0V2.50750Frequency Programming
CurrentIINVFADJ = -3V1.25375µA
IIN Offset VoltageVIN±1.0±2.0mV
ΔFo/°CVFADJ = 0V600Frequency Temperature
CoefficientFo/°CVFADJ = -3V200ppm/°C
(ΔFo/Fo)
ΔV+V- = -5V, V+ = 4.75V to 5.25V±0.4±2.00
Frequency Power-Supply
Rejection(ΔFo/Fo)
ΔV-V+ = 5V, V- = -4.75V to -5.25V±0.2±1.00
%/V
OUTPUT AMPLIFIER (applies to all waveforms)Output Peak-to-Peak SymmetryVOUT±4mV
Output ResistanceROUT0.10.2Ω
Output Short-Circuit CurrentIOUTShort circuit to GND40mA
SQUARE-WAVE OUTPUT (RL = 100Ω)AmplitudeVOUT1.92.02.1VP-P
Rise TimetR10% to 90%12ns
Fall TimetF90% to 10%12ns
Duty CycledcVDADJ = 0V, dc = tON/t x 100%475053%
TRIANGLE-WAVE OUTPUT (RL = 100Ω)AmplitudeVOUT1.92.02.1VP-P
NonlinearityFO = 100kHz, 5% to 95%0.5%
Duty CycledcVDADJ = 0V (Note 1)475053%
SINE-WAVE OUTPUT (RL = 100Ω)VOUT1.92.02.1VP-P
Total Harmonic DistortionTHDCF = 1000pF, FO = 100kHz2.0%
MAX038
High-Frequency Waveform Generator
Note 1:Guaranteed by duty-cycle test on square wave.
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, GND = DGND= 0V, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, CF= 100pF,
RIN= 25kΩRL= 1kΩ, CL= 20pF, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
SYNC OUTPUTOutput Low VoltageVOLISINK = 3.2mA0.30.4V
Output High VoltageVOHISOURCE = 400µA2.83.5V
Rise TimetR10% to 90%, RL = 3kΩ, CL = 15pF10ns
Fall TimetF90% to 10%, RL = 3kΩ, CL = 15pF10ns
Duty CycledcSYNC50%
DUTY-CYCLE ADJUSTMENT (DADJ)DADJ Input CurrentIDADJ190250320µA
DADJ Voltage RangeVDADJ±2.3V
Duty-Cycle Adjustment Rangedc-2.3V ≤ VDADJ ≤ +2.3V1585%
DADJ Nonlinearitydc/VFADJ-2V ≤ VDADJ ≤ +2V24%
Change in Output Frequency
with DADJFo/VDADJ-2V ≤ VDADJ ≤ +2V±2.5±8%
Maximum DADJ Modulating
FrequencyFDC2MHz
FREQUENCY ADJUSTMENT (FADJ)FADJ Input CurrentIFADJ190250320µA
FADJ Voltage RangeVFADJ±2.4V
Frequency Sweep RangeFo-2.4V ≤ VFADJ ≤ +2.4V±70%
FM Nonlinearity with FADJFo/VFADJ-2V ≤ VFADJ ≤ +2V±0.2%
Change in Duty Cycle with FADJdc/VFADJ-2V ≤ VFADJ ≤ +2V±2%
Maximum FADJ Modulating
FrequencyFF2MHz
VOLTAGE REFERENCEOutput VoltageVREFIREF = 02.482.502.52V
Temperature CoefficientVREF/°C20ppm/°C
0mA ≤ IREF ≤ 4mA (source)12Load RegulationVREF/IREF-100µA ≤ IREF ≤ 0µA (sink)14mV/mA
Line RegulationVREF/V+4.75V ≤ V+ ≤ 5.25V (Note 2)12mV/V
LOGIC INPUTS (A0, A1, PDI)Input Low VoltageVIL0.8V
Input High VoltageVIH2.4V
Input Current (A0, A1)IIL, IIHVA0, VA1 = VIL, VIH±5µA
Input Current (PDI)IIL, IIHVPDI = VIL, VIH±25µA
POWER SUPPLYPositive Supply VoltageV+4.755.25V
SYNC Supply VoltageDV+4.755.25V
Negative Supply VoltageV-4.75-5.25V
Positive Supply CurrentI+3545mA
SYNC Supply CurrentIDV+12mA
Negative Supply CurrentI4555mA
MAX038
High-Frequency Waveform Generator
Typical Operating Characteristics(Circuit of Figure 1, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, RL= 1kΩ/, CL= 20pF, TA= +25°C, unless
otherwise noted.)
OUTPUT FREQUENCY
vs. IIN CURRENT
MAX038-08
IIN CURRENT (μA)
OUTPUT FREQUENCY (Hz)
10k
100k
10M
100M
100μF
47μF
10μF
3.3μF
1μF
100nF
33nF
3.3nF
330pF
100pF
33pF
NORMALIZED OUTPUT FREQUENCY
vs. FADJ VOLTAGE
MAX038-09
VFADJ (V)
OUT
NORMALIZED
IIN = 100μA, COSC = 1000pF
NORMALIZED OUTPUT FREQUENCY
vs. DADJ VOLTAGE
MAX038-17
DADJ (V)
NORMALIZED OUTPUT FREQUENCY
IIN = 10μA
IIN = 25μA
IIN = 50μA
IIN = 100μA
IIN = 250μA
IIN = 500μA
DUTY-CYCLE LINEARITY
vs. DADJ VOLTAGE
MAX038-18
DADJ (V)
DUTY-CYCLE LINEARITY ERROR (%)1.5
IIN = 10μA
IIN = 25μA
IIN = 50μA
IIN = 100μA
IIN = 250μA
IIN = 500μA2
DUTY CYCLE vs. DADJ VOLTAGEMAX038-16B
DADJ (V)
DUTY CYCLE (%)-11
IIN = 200μA
MAX038
High-Frequency Waveform Generator
SINE-WAVE OUTPUT (50Hz)TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
CF = 1μF
TRIANGLE-WAVE OUTPUT (50Hz)TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
CF = 1μF
SQUARE-WAVE OUTPUT (50Hz)TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
SINE-WAVE OUTPUT (20MHz)IIN = 400μA
CF = 20pF
TRIANGLE-WAVE OUTPUT (20MHz)IIN = 400μA
CF = 20pF
SINE WAVE THD vs. FREQUENCYMAX038 toc01
FREQUENCY (Hz)
THD (%)100k10k1k
10010M
Typical Operating Characteristics (continued)(Circuit of Figure 1, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, RL= 1kΩ/, CL= 20pF, TA= +25°C, unless
otherwise noted.)
MAX038
High-Frequency Waveform Generator
Typical Operating Characteristics (continued)(Circuit of Figure 1, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, RL= 1kΩ/, CL= 20pF, TA= +25°C, unless
otherwise noted.)
FREQUENCY MODULATION USING FADJTOP: OUTPUT
BOTTOM: FADJ
0.5V
-0.5V
FREQUENCY MODULATION USING IINTOP: OUTPUT
BOTTOM: IIN
FREQUENCY MODULATION USING IINTOP: OUTPUT
BOTTOM: IIN
PULSE-WIDTH MODULATION USING DADJTOP: SQUARE-WAVE OUT, 2VP-P
BOTTOM: VDADJ, -2V to +2.3V
+1V
-1V
+2V
-2V
SQUARE-WAVE OUTPUT (20MHz)IIN = 400μA
CF = 20pF
MAX038
High-Frequency Waveform GeneratorOUTPUT SPECTRUM, SINE WAVE
(Fo = 11.5MHz)
MAX038-12A
FREQUENCY (MHz)
ATTENUATION (dB)80
RIN = 15kΩ (VIN = 2.5V), CF = 20pF, VDADJ = 40mV, VFADJ = -3V
OUTPUT SPECTRUM, SINE WAVE
(Fo = 5.9kHz)
MAX038
12B
FREQUENCY (kHz)
ATTENUATION (dB)40
RIN = 51kΩ (VIN = 2.5V), CF = 0.01μF, VDADJ = 50mV, VFADJ = 0V
Pin Description
Typical Operating Characteristics (continued)(Circuit of Figure 1, V+ = DV+ = 5V, V- = -5V, VDADJ= VFADJ= VPDI= VPDO= 0V, RL= 1kΩ/, CL= 20pF, TA= +25°C, unless
otherwise noted.)
PINNAMEFUNCTIONREF2.50V bandgap voltage reference output
2, 6, 9,
11, 18GNDGround*A0Waveform selection input; TTL/CMOS compatibleA1Waveform selection input; TTL/CMOS compatibleCOSCExternal capacitor connectionDADJDuty-cycle adjust inputFADJFrequency adjust inputIINCurrent input for frequency controlPDOPhase detector output. Connect to GND if phase detector is not used.PDIPhase detector reference clock input. Connect to GND if phase detector is not used.SYNCTTL/C M O S - com p ati b l e outp ut, r efer enced b etw een D G N D and D V + . P er m i ts the i nter nal osci l l ator to b e
synchronized with an external signal. Leave open if unused.DGNDDigital groundDV+Digital +5V supply input. Can be left open if SYNC is not used.V++5V supply inputOUTSine, square, or triangle outputV--5V supply input
*The five GND pins are not internally connected. Connect all five GND pins to a quiet ground close to the device. A ground plane is
recommended (see Layout Considerations).
MAX038
Detailed DescriptionThe MAX038 is a high-frequency function generator
that produces low-distortion sine, triangle, sawtooth, or
square (pulse) waveforms at frequencies from less than
1Hz to 20MHz or more, using a minimum of external
components. Frequency and duty cycle can be inde-
pendently controlled by programming the current, volt-
age, or resistance. The desired output waveform is
selected under logic control by setting the appropriate
code at the A0 and A1 inputs. A SYNC output and
phase detector are included to simplify designs requir-
ing tracking to an external signal source.
The MAX038 operates with ±5V ±5% power supplies.
The basic oscillator is a relaxation type that operates by
alternately charging and discharging a capacitor, CF,
with constant currents, simultaneously producing a tri-
angle wave and a square wave (Figure 1). The charg-
ing and discharging currents are controlled by the cur-
rent flowing into IIN, and are modulated by the voltages
applied to FADJ and DADJ. The current into IIN can be
varied from 2µA to 750µA, producing more than two
decades of frequency for any value of CF. Applying
±2.4V to FADJ changes the nominal frequency (with
VFADJ= 0V) by ±70%; this procedure can be used for
fine control.
Duty cycle (the percentage of time that the output wave-
form is positive) can be controlled from 10% to 90% by
applying ±2.3V to DADJ. This voltage changes the CF
charging and discharging current ratio while maintain-
ing nearly constant frequency.
High-Frequency Waveform GeneratorMAX038
OSCILLATOR
OSCILLATOR
CURRENT
GENERATOR
2.5V
VOLTAGE
REFERENCE
OSC B
OSC A
TRIANGLE
SINE
SHAPER
COMPARATOR
COMPARATOR
PHASE
DETECTOR
MUX
COSC
GNDCF
FADJ
DADJ
IIN
REF1
2, 9, 11, 18
GNDRDRIN
+5V
-5V
-250μA
SINE
TRIANGLE
SQUAREA1
OUT
SYNC
PDO
PDI4
DGNDDV+16
+5V
= SIGNAL DIRECTION, NOT POLARITY
= BYPASS CAPACITORS ARE 1μF CERAMIC OR 1μF ELECTROLYTIC IN PARALLEL WITH 1nF CERAMIC.
Figure 1. Block Diagram and Basic Operating Circuit
MAX038
A stable 2.5V reference voltage, REF, allows simple
determination of IIN, FADJ, or DADJ with fixed resistors,
and permits adjustable operation when potentiometers
are connected from each of these inputs to REF. FADJ
and/or DADJ can be grounded, producing the nominal
frequency with a 50% duty cycle.
The output frequency is inversely proportional to
capacitor CF. CF values can be selected to produce
frequencies above 20MHz.
A sine-shaping circuit converts the oscillator triangle
wave into a low-distortion sine wave with constant
amplitude. The triangle, square, and sine waves are
input to a multiplexer. Two address lines, A0 and A1,
control which of the three waveforms is selected. The
output amplifier produces a constant 2VP-P amplitude
(±1V), regardless of wave shape or frequency.
The triangle wave is also sent to a comparator that pro-
duces a high-speed square-wave SYNC waveform that
can be used to synchronize other oscillators. The SYNC
circuit has separate power-supply leads and can be
disabled.
Two other phase-quadrature square waves are gener-
ated in the basic oscillator and sent to one side of an
"exclusive-OR" phase detector. The other side of the
phase-detector input (PDI) can be connected to an
external oscillator. The phase-detector output (PDO) is
a current source that can be connected directly to
FADJ to synchronize the MAX038 with the external
oscillator.
Waveform SelectionThe MAX038 can produce either sine, square, or trian-
gle waveforms. The TTL/CMOS-logic address pins (A0
and A1) set the waveform, as shown below:
X = Don’t care.
Waveform switching can be done at any time, without
regard to the phase of the output. Switching occurs
within 0.3µs, but there may be a small transient in the
output waveform that lasts 0.5µs.
Waveform Timing
Output FrequencyThe output frequency is determined by the current
injected into the IIN pin, the COSC capacitance (to
VFADJ= 0V, the fundamental output frequency (Fo) is
given by the formula:
Fo (MHz) = IIN(µA) ÷CF(pF) [1]
The period (to) is:
to (µs) = CF(pF) ÷IIN(µA) [2]
where:
IIN= current injected into IIN (between 2µA and
750µA) = capacitance connected to COSC and GND
(20pF to >100µF).
For example:
0.5MHz = 100µA ÷200pF
and
2µs = 200pF ÷100µA
Optimum performance is achieved with IIN between
10µA and 400µA, although linearity is good with IIN
between 2µA and 750µA. Current levels outside of this
range are not recommended. For fixed-frequency oper-
ation, set IIN to approximately 100µA and select a suit-
able capacitor value. This current produces the lowest
temperature coefficient, and produces the lowest fre-
quency shift when varying the duty cycle.
The capacitance can range from 20pF to more than
100µF, but stray circuit capacitance must be minimized
by using short traces. Surround the COSC pin and the
trace leading to it with a ground plane to minimize cou-
pling of extraneous signals to this node. Oscillation
above 20MHz is possible, but waveform distortion
increases under these conditions. The low frequency
limit is set by the leakage of the COSC capacitor and
by the required accuracy of the output frequency.
Lowest frequency operation with good accuracy is usu-
ally achieved with 10µF or greater non-polarized
capacitors.
An internal closed-loop amplifier forces IIN to virtual
ground, with an input offset voltage less than ±2mV. IIN
may be driven with either a current source (IIN), or a
voltage (VIN) in series with a resistor (RIN). (A resistor
between REF and IIN provides a convenient method of
generating IIN: IIN= VREF/RIN.) When using a voltage in
series with a resistor, the formula for the oscillator fre-
quency is:
Fo (MHz) = VIN ÷[RINx CF(pF)][3]
and:
to (µs) = CF(pF) x RIN÷VIN[4]
High-Frequency Waveform GeneratorA1WAVEFORM1Sine wave0Square wave0Triangle wave
MAX038
