CA3524E Intersil, CA3524E Datasheet - Page 14

• Manufacturer Part Number: CA3524E
• Description: REGUL. PULSE WIDTH MODULATOR
• Manufacturer: Intersil

Specifications of CA3524E

• Rohs Status: RoHS non-compliant
• Other names: CA3524

Digital Readout Scale
The CA1524 can be used as the driving source for an
electronic scale application. The circuit shown in Figures 24
and 25 uses half (Q2) of the CA1524 output in a low-voltage
switching regulator (2.2V) application to drive the LED’s
displaying the weight. The remaining output stage (Q1) is
used as a driver for the sampling plates PL1 and PL2. Since
the CA1524 contains a 5V internal regulator and a wide
operating range of 8V to 40V, a single 9V battery can power
the total system. The two plates, PL1 and PL2, are driven
with opposite phase signals (frequency held constant but
duty cycle may change) from the pulse-width modulator lC
(CA1524). The sensor, S, is located between the two plates.
Plates PL1, S and PL2 form an effective capacitance bridge-
type divider network. As plate S is moved according to the
A
B
C
OSCILLATOR
(PART OF CA1524)
ADJUSTMENT
2.5V
ADJUSTMENT
INPUTS:
GAIN
20KHz
HIGH
LOW
ZERO
FULL SCALE
NO WEIGHT
11
10
50K
FIGURE 25. SCHEMATIC DIAGRAM OF DIGITAL READOUT SCALE (CONT’D)
8
13
CA3162E
0.27
10K
9
F
12 14
7
OUTPUTS
DRIVERS
16
15
1
2
5
3
4
FIGURE 24. BASIC DIGITAL READOUT SCALE
DIGIT
0.1
BCD
F
PL1
PL2
S
CA1524, CA2524, CA3524
SCALE MECHANISM
6
2
1
7
COUPLED TO
MECHANICAL
CA3161E
8
16
+5V
3
AC
AMP
CA3130
13
12
11
10
15
14
14
9
object’s weight, a change in capacitance is noted between
PL1, S and PL2. This change is reflected as a voltage to the
ac amplifier (CA3160). At the null position the signals from
PL1 and PL2 as detected by S are equal in amplitude, but
opposite in phase. As S is driven by the scale mechanism
down toward PL2, the signal at S becomes greater. The
CA3160 ac amplifier provides a buffer for the small signal
change noted at S. The output of the CA3160 is converted to
a dc voltage by a peak-to-peak detector. A peak-to-peak
detector is needed, since the duty cycle of the sampled
waveform is subject to change. The detector output is filtered
further and displayed via the CA3161E and CA3162E digital
readout system, indicating the weight on the scale.
MSD
(PART OF CA1524)
PEAK TO PEAK
DISPLAY DRIVE
DETECTOR
NSD
NOTE:
1. FAIRCHILD FND507 OR EQUIVALENT
LSD
LOW PASS
POWER 2N2907
OR EQUIVALENT
FILTER
DIGITAL METER
AND DISPLAY
COMMON-
ANODE LED
DISPLAYS
(NOTE 1)
VOLTAGE
DC