HA17901A_15 Datasheet, PDF (13/18 Pages) Renesas Technology Corp – Quadruple Comparators

HA17901A Series
3. Voltage Controlled Oscillator
In the circuit in figure 5, comparator A₁ operates as an integrator, A₂ operates as a comparator with hysteresis, and
A₃ operates as the switch that controls the oscillator frequency. If the output Vout1 is at the low level, the A₃ output
will go to the low level and the A1 inverting input will become a lower level than the A1 noninverting input. The
A₁ output will integrate this state and its output will increase towards the high level. When the output of the
integrator A₁ exceeds the level on the comparator A₂ inverting input, A₂ inverts to the high level and both the output
Vout1 and the A₃ output go to the high level. This causes the integrator to integrate a negative state, resulting in its
output decreasing towards the low level. Then, when the A₁ output level becomes lower than the level on the A₂
noninverting input, the output Vout1 is once again inverted to the low level. This operation generates a square wave
on Vout1 and a triangular wave on Vout2.
100 k
+V_C
Frequency
control
voltage
input
0.1 µ
20 k
50 k
10
20 k
V_CC
500 p
−
A₁
HA17901A
+
V_CC
A₃
−
V_CC
3k
0.01 µ
5.1 k
V_CC/2
V_CC/2
V_CC = 30 V
+250 mV < +V_C < +50 V
700 Hz < / < 100 kHz
HA17901A
+
100 k
V_CC
+
A₂
HA17901A
−
Figure 5 Voltage Controlled Oscillator
V_CC
3k
Output 1
Output 2
4. Basic Comparator
The circuit shown in figure 6 is a basic comparator. When the input voltage V_IN exceeds the reference voltage V_REF,
the output goes to the high level.
V_CC
Vin
V_REF
+
HA17901A
−
3 kΩ
Figure 6 Basic Comparator
Rev.1.00 Mar 10, 2006 page 11 of 15