LT1713IMS8 Ver la hoja de datos (PDF) - Linear Technology
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LT1713IMS8 Datasheet PDF : 16 Pages
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LT1713/LT1714
TYPICAL APPLICATIO
forte of this particular implementation is that it is rail-to-
rail allowing a full-scale analog input. Once the triangle
wave is achieved, the remainder of the pulse width modu-
lator is easy, and is constituted by doing a simple compari-
son using the second half of the LT1714. The triangle wave
and the relatively slow moving analog signal (the one to be
modulated or to do the modulation, depending on how you
look at it) are fed into the inputs of comparator B, whose
output is then the PWM representation of the analog input
voltage. The higher the analog input voltage, the wider the
output pulse. The time averaged output level is thus
proportional to the analog input voltage. This binary
output can then be fed into power transistors with direct
control over motor or speaker winding current, for
example, with their inherent lowpass characteristic. Care
must be taken to avoid cross conduction in the output
power transistors.
The linearity of the pulse width modulated signal can easily
be ascertained by putting a simple 2-pole RC filter at the
output (as shown in Figure 9). This demodulates the signal
which can then be viewed and compared with the original
input signal on an oscilloscope. Using a spectrum analyzer
and a 1kHz reference signal, this circuit’s distortion prod-
ucts were measured as better than – 50dBc (0.3%) to
about 3.5VP-P, degrading to – 30dBc (3%) as the circuit
clips at 5VP-P on a single 5V supply.
V+
R2
2k
R3
2k
R1
26.1Ω
V+
2+
4
14
A
1/2 LT1714
1–
16
15
3
V+
V+ = 2.7V TO 7V
ANTIALIASING
C1
500pF
ANALOG
INPUT
1k FILTER
C4
0.001µF
V+
16kHz ANALOG FILTER
FOR LINEARITY MEASUREMENT
R4
13 499Ω
R5
1k
2– 1
V+
7
6
LT1809
3+
4
21Ω
C3
100pF
7+
5
11
B
1/2 LT1714 12
8–
10
9
6
1k
C5
0.01µF
10k
C6
0.001µF
171314 F09
C2
R6
0.01µF 1k
1MHz
TRIANGLE
WAVE
COMPLEMENTARY
1MHz PWM
OUTPUTS
Figure 9. Rail-to-Rail 1MHz Pulse Width Modulator
RELATED PARTS
PART NUMBER
LT1016
LT1116
LT1394
LT1671
LT1711/LT1712
LT1719
LT1720/LT1721
DESCRIPTION
UltraFast Precision Comparator
12ns Single Supply Ground Sensing Comparator
7ns, UltraFast Single Supply Comparator
60ns, Low Power, Single Supply Comparator
Single/Dual, 4.5ns, 3V/5V/±5V Rail-to-Rail Comparators
4.5ns, Single Supply 3V/5V Comparator
Dual/Quad, 4.5ns, Single Supply Comparator
COMMENTS
Industry Standard 10ns Comparator
Single Supply Version of the LT1016
6mA Single Supply Comparator
450µA Single Supply Comparator
Faster Versions of LT1713/LT1714
4mA Comparator with Rail-to-Rail Outputs
Dual/Quad Version of the LT1719
16 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX:(408)434-0507 q www.linear-tech.com
171314f LT/TP 0501 4K • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2000
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