LT1016_03 Datasheet, PDF (20/20 Pages) Linear Technology – UltraFast Precision 10ns Comparator

LT1016
APPLICATIO S I FOR ATIO
1Hz to 10MHz V-to-F Converter
The LT1016 and the LT1122 FET input amplifier combine
to form a high speed V-to-F converter in Figure 16. A
variety of techniques is used to achieve a 1Hz to 10MHz
output. Overrange to 12MHz (V_IN = 12V) is provided. This
circuit’s dynamic range is 140dB, or seven decades, which
is wider than any commercially available unit. The 10MHz
full-scale frequency is 10 times faster than monolithic
V-to-F’s now available. The theory of operation is based on
the identity Q = CV.
Each time the circuit produces an output pulse, it feeds
back a fixed quantity of charge, Q, to a summing node, S.
The circuit’s input furnishes a comparison current at the
summing node. This difference current is integrated in
INPUT
0V TO 10V
Q1
15pF
(POLYSTYRENE)
A1’s 68pF feedback capacitor. The amplifier controls the
circuit’s output pulse generator, closing feedback loop
around the integrating amplifier. To maintain the sum-
ming node at zero, the pulse generator runs at a frequency
that permits enough charge pumping to offset the input
signal. Thus, the output frequency is linearly related to the
input voltage.
To trim this circuit, apply 6.000V at the input and adjust the
2kW pot for 6.000MHz output. Next, excite the circuit with
a 10.000V input and trim the 20k resistor for 10.000MHz
output. Repeat these adjustments until both points are
fixed. Linearity of the circuit is 0.03%, with full-scale drift
of 50ppm/∞C. The LTC1050 chopper op amp servos the
integrator’s noninverting input and eliminates the need for
a zero trim. Residual zero point error is 0.05Hz/∞C.
OUTPUT
1Hz TO 10MHz
5V REF 15V
15V
–15V
Q2
2k
6MHz
TRIM _10k*
10k
5V
–
A1
LT1122
+
68pF
8
100Ω
– 5V
150pF
15V
1.2k
5V – 5V
+
A2
LT1016
–
= 2N2369
= 74HC14
* = 1% METAL FILM/10ppm/°C
BYPASS ALL ICs WITH 2.2µF ON
EACH SUPPLY DIRECTLY AT PINS
5V
–
LTC1050
+
– 5V
1k
5pF
0.02µF
36k
+
1k
10µF
4.7µF
0.1µF
A4
LT1010
A3
LT1006
470Ω
100k*
6.8Ω
100k*
LM134
2.2M*
LT1034-1.2V
LT1034-2.5V
Q3
10M
10MHz ^20k
TRIM
Q4
1016 F16
Figure 16. 1Hz to 10MHz V-to-F Converter. Linearity is Better Than 0.03% with 50ppm/∞C Drift
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20 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ^● FAX:[phone] ^● www.linear-tech.com
sn1016 1016fcs LT/TP 0601 1.5K REV C • PRINTED IN USA
„ LINEAR TECHNOLOGY CORPORATION 1991