MC1455 Ver la hoja de datos (PDF) - ON Semiconductor

Número de pieza

componentes Descripción

Fabricante

MC1455

Timers

ON Semiconductor 

MC1455, MC1455B, NCV1455B

APPLICATIONS INFORMATION

Linear Voltage Ramp

In the monostable mode, the resistor can be replaced by a

constant current source to provide a linear ramp voltage. The

capacitor still charges from 0 VCC to 2/3 VCC. The linear

ramp time is given by:

t = 2 VCC , where I = VCC − VB − VBE

31

RE

If VB is much larger than VBE, then t can be made

independent of VCC.

Missing Pulse Detector

The timer can be used to produce an output when an input

pulse fails to occur within the delay of the timer. To

accomplish this, set the time delay to be slightly longer than

the time between successive input pulses. The timing cycle

is then continuously reset by the input pulse train until a

change in frequency or a missing pulse allows completion of

the timing cycle, causing a change in the output level.

+VCC (5.0 V to 15 V)

VCC

Reset 4 8 VCC

Digital 3

Output

MC1455

RE 2N4403 R1

7

VE

or Equiv

VB

I

6

2

Trigger

5

Sweep

Output

C

R2

1 0.01 mF Control

Voltage

RL

3

Output

Input

2

Trigger

Reset

4

VCC

8

Discharge

MC1455

1

7

Threshold

6 Control

5 Voltage

0.01 mF

RA

C

2N4403

or Equiv

Figure 20. Linear Voltage Sweep Circuit

Figure 21. Missing Pulse Detector

t = 100 ms/cm

(RE = 10 kW, R2 = 100 kW, R1 = 39 kW, C = 0.01 mF, VCC = 15 V)

Figure 22. Linear Voltage Ramp Waveforms

t = 500 ms/cm

(RA = 2.0 kW, RL = 1.0 kW, C = 0.01 mF, VCC = 15 V)

Figure 23. Missing Pulse Detector Waveforms

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