Hig h -Fre q u e n c y Wa ve fo rm Ge n e ra t o r
3
4
A0
A1
TRIANGLE
OSC A
5
6
COSC
GND
SINE
SINE
SHAPER
OSCILLATOR
C
F
OSC B
OUT
19
MAX038
TRIANGLE
SQUARE
MUX
R
L
C
L
FADJ
DADJ
8
7
OSCILLATOR
CURRENT
GENERATOR
COMPARATOR
10 IIN
MAX038
R
F
R
D
R
IN
-250µA
SYNC
14
COMPARATOR
2.5V
REF
1
VOLTAGE
REFERENCE
*
12
13
PDO
PDI
17
20
V+
V-
+5V
-5V
PHASE
DETECTOR
GND
2, 9, 11, 18
DGND
15
DV+
16
*
= SIGNAL DIRECTION, NOT POLARITY
= BYPASS CAPACITORS ARE 1µF CERAMIC OR 1µF ELECTROLYTIC IN PARALLEL WITH 1nF CERAMIC.
+5V
*
Figure 1. Block Diagram and Basic Operating Circuit
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
_______________De t a ile d De s c rip t io n
The 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.
decades of frequency for any value of C . Applying
F
±2.4V to FADJ changes the nominal frequency (with
V
FADJ
= 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 C
F
The MAX038 operates with ±5V ±5% power supplies.
The basic oscillator is a relaxation type that operates by
charging and discharging current ratio while maintaining
nearly constant frequency.
alternately charging and discharging a capacitor, C ,
F
8
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