HCF4047B

6/12

APPLICATION INFORMATION

1 - CIRCUIT DESCRIPTION

Astable operation is enabled by a high level on the

ASTABLE input. The period of the square wave at

the Q and Q Outputs in this mode of operation is a

function of the external components employed.

"True" input pulses on the ASTABLE input or

"Complement" pulses on the ASTABLE input

allow the circuit to be used as a gatable

multivibrator. The OSCILLATOR output period will

be half of the Q terminal output in the astable

mode. However, a 50% duty cycle is not

guaranteed at this output. In the monostable

mode, positive-edge triggering is accomplished by

application

of a

leading-edge pulse

to

the

+TRIGGER input and a low level to the -TRIGGER

input. For negative-edge triggering, a trailing-edge

pulse is applied to the -TRIGGER and a high level

is applied to the +TRIGGER. Input pulses may be

of any duration relative to the output pulse. The

multivibrator can be retriggered (on the leading

edge only) by applying a common pulse to both

the RETRIGGER and +TRIGGER inputs. In this

mode the output pulse remains high as long as the

input pulse period is shorter than the period

determined by the RC components. An external

countdown

option

can

be

implemented

by

Symbol

Parameter

Test Condition

Value (*)

Unit

Min.

Typ.

Max.

Time

Astable, Astable

to Osc. Out

5

200

400

ns

10

100

200

15

80

160

Astable, Astable

to Q, Q

5

350

700

10

175

350

15

125

250

+ or - Trigger to

Q, Q

5

500

1000

10

225

450

15

150

300

Retrigger to Q, Q

5

300

600

10

150

300

15

100

200

External Reset

to Q, Q

5

250

500

10

100

200

15

70

140

5

100

200

ns

10

50

100

15

40

80

Input Pulse Width

+ Trigger

- Trigger

5

200

400

ns

10

80

160

15

50

100

Reset

5

100

200

10

50

100

15

30

60

Retrigger

5

300

600

10

115

230

15

75

150

Input Rise and Fall Time All Inputs

5

Unlimited

µs

10

15

Q or Q Deviation from 50% Duty

Factor

5

±0.5

±1

%

10

±0.5

±1

15

±0.1

±0.5