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PDF MAX038 Data sheet ( Hoja de datos )
| Número de pieza | MAX038 | |
| Descripción | High-Frequency Waveform Generator | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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AVAILABLE
MAX038
High-Frequency Waveform Generator
General Description
The 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-P signal 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.
Features
♦ 0.1Hz to 20MHz Operating Frequency Range
♦ Triangle, Sawtooth, Sine, Square, and Pulse
Waveforms
♦ Independent Frequency and Duty-Cycle
Adjustments
♦ 350 to 1 Frequency Sweep Range
♦ 15% to 85% Variable Duty Cycle
♦ Low-Impedance Output Buffer: 0.1Ω
♦ Low 200ppm/°C Temperature Drift
Ordering Information
PART
TEMP RANGE
MAX038CPP
0°C to +70°C
MAX038CWP
0°C to +70°C
MAX038C/D*
0°C to +70°C
* Contact factory prior to design.
PIN-PACKAGE
20 Plastic DIP
20 SO
Dice
Functional Diagrams
Applications
Precision Function Generators
Voltage-Controlled Oscillators
Frequency Modulators
Pulse-Width Modulators
Phase-Locked Loops
Frequency Synthesizer
FSK Generator—Sine and Square Waves
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configuration
TOP VIEW
REF 1
GND 2
A0 3
A1 4
COSC 5
GND 6
DADJ 7
FADJ 8
GND 9
IIN 10
MAX038
20 V-
19 OUT
18 GND
17 V+
16 DV+
15 DGND
14 SYNC
13 PDI
12 PDO
11 GND
DIP/SO
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-0266; Rev 7; 8/07
1 page  
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.)
SINE WAVE THD vs. FREQUENCY
7
SINE-WAVE OUTPUT (50Hz)
6
5
4
3
2
1
0
100
1k 10k 100k 1M
FREQUENCY (Hz)
10M
SINE-WAVE OUTPUT (20MHz)
TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
CF = 1μF
TRIANGLE-WAVE OUTPUT (50Hz)
IIN = 400μA
CF = 20pF
TRIANGLE-WAVE OUTPUT (20MHz)
TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
CF = 1μF
SQUARE-WAVE OUTPUT (50Hz)
IIN = 400μA
CF = 20pF
Maxim Integrated
TOP: OUTPUT 50Hz = Fo
BOTTOM: SYNC
IIN = 50μA
CF = 1μF
5
5 Page 
MAX038
High-Frequency Waveform Generator
–5V +5V
PRECISION DUTY-CYCLE ADJUSTMENT CIRCUIT
FREQUENCY
C1
1μF
RIN
20kΩ
R1
12kΩ
1 REF
C3
1nF
20 17 4
V- V+ A1
3
AO
7 DADJ MAX038
10
IIN
8
FADJ
5 COSC
19
OUT
DV+ 16
DGND 15
SYNC 14
13
PDI
12
PDO
GND GND GND GND GND
CF 6 2 9 11 18
C2
1μF
R2
50Ω
N.C.
N.C.
–2.5V R4
100kΩ
SINE-WAVE
OUTPUT
2 x 2.5V
Fo = RIN x CF
R7
100kΩ
R6
5kΩ
R3 +2.5V
100kΩ
REF
R5
100kΩ
MAX038
DADJ
ADJUST R6 FOR MINIMUM SINE-WAVE DISTORTION
Figure 2. Operating Circuit with Sine-Wave Output and 50% Duty Cycle; SYNC and FADJ Disabled
With FADJ disabled, the output frequency can still be
changed by modulating IIN.
Swept Frequency Operation
The output frequency can be swept by applying a vary-
ing signal to IIN or FADJ. IIN has a wider range, slightly
slower response, lower temperature coefficient, and
requires a single polarity current source. FADJ may be
used when the swept range is less than ±70% of the
center frequency, and it is suitable for phase-locked
loops and other low-deviation, high-accuracy closed-
loop controls. It uses a sweeping voltage symmetrical
about ground.
Connecting a resistive network between REF, the volt-
age source, and FADJ or IIN is a convenient means of
offsetting the sweep voltage.
Duty Cycle
The voltage on DADJ controls the waveform duty cycle
(defined as the percentage of time that the output
waveform is positive). Normally, VDADJ = 0V, and the
duty cycle is 50% (Figure 2). Varying this voltage from
+2.3V to -2.3V causes the output duty cycle to vary
from 15% to 85%, about -15% per volt. Voltages
beyond ±2.3V can shift the output frequency and/or
cause instability.
DADJ can be used to reduce the sine-wave distortion.
The unadjusted duty cycle (VDADJ = 0V) is 50% ±2%;
any deviation from exactly 50% causes even order har-
monics to be generated. By applying a small
adjustable voltage (typically less than ±100mV) to
VDADJ, exact symmetry can be attained and the distor-
tion can be minimized (see Figure 2).
The voltage on DADJ needed to produce a specific
duty cycle is given by the formula:
VDADJ = (50% - dc) x 0.0575
[11]
or:
VDADJ = (0.5 - [tON ÷ to]) x 5.75 [12]
where:
VDADJ = DADJ voltage (observe the polarity)
dc = duty cycle (in %)
tON = ON (positive) time
to = waveform period.
Conversely, if VDADJ is known, the duty cycle and ON
time are given by:
dc = 50% - (VDADJ x 17.4)
[13]
tON = to x (0.5 - [VDADJ x 0.174]) [14]
Maxim Integrated
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX038.PDF ] | |
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