MAX038 Просмотр технического описания (PDF) - Maxim Integrated
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MAX038 Datasheet PDF : 16 Pages
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High-Frequency Waveform Generator
5 COSC
TRIANGLE
OSCILLATOR OSC A
CF
6 GND
OSC B
8 FADJ
7 DADJ
10 IIN
RF RD RIN
OSCILLATOR
CURRENT
GENERATOR
-250µA
*
+5V
-5V
1 REF
17 V+
20 V-
2, 9, 11, 18 GND
2.5V
VOLTAGE
REFERENCE
3
4
A0
A1
SINE
SINE
SHAPER
TRIANGLE
MUX
SQUARE
COMPARATOR
OUT 19
RL
CL
COMPARATOR
MAX038
SYNC 14
PHASE
DETECTOR
PDO 12
PDI 13
DGND
DV+
15
16
= SIGNAL DIRECTION, NOT POLARITY
*
+5V
* = BYPASS CAPACITORS ARE 1µF CERAMIC OR 1µF ELECTROLYTIC IN PARALLEL WITH 1nF CERAMIC.
Figure 1. Block Diagram and Basic Operating Circuit
_______________Detailed Description
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.
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 maintaining
nearly constant frequency.
8 _______________________________________________________________________________________
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