HCF4047B datasheet(7/12 Pages) STMICROELECTRONICS

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HCF4047B

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coupling "Q" to an external "N" counter and

resetting the counter with the trigger pulse. The

counter output pulse is fed back to the ASTABLE

input and has a duration equal to N times the

period of the multivibrator. A high level on the

EXTERNAL RESET input assures no output pulse

during an "ON" power condition. This input can

also be activated to terminate the output pulse at

any time. In the monostable mode, a high-level or

power-on reset pulse, must be applied to the

EXTERNAL RESET whenever VDD is applied.

2 - ASTABLE MODE

The

following

analysis

presents

worst-case

variations from unit-to-unit as a function of

transfer-voltage (VTR) shift (33% - 67% VDD) for

free-running (astable) operation.

ASTABLE MODE WAVEFORMS

Typ : VTR = 0.5 VDD tA = 4.40 RC

Min : VTR = 0.33 VDD tA = 4.62 RC

Max : VTR = 0.67 VDD tA = 4.62 RC

thus if tA = 4.40 RC is used, the maximum

variation will be (+ 5.0%, -0.0%)

In addition to variations from unit-to-unit, the

astable period may vary as a function of frequency

with respect to VDD and temperature.

3 - MONOSTABLE MODE

The

following

analysis

presents

worst-case

variations from unit-to-unit as a function of

transfer-voltage (VTR) shift (33% - 67% VDD) for

one-shot (monostable) operation.

MONOSTABLE WAVEFORMS

VTR

t1 = -RC In —————

VDD + VTR

VDD - VTR

t2 = -RC In —————

2VDD - VTR

(VTR)(VDD - VTR)

t3 = 2(t1+t2)= -2RC In ———————————

(VDD + VTR)(2VDD - VTR)

VTR

t1 = -RC In ———

2VDD

VDD - VTR

t2 = -RC In —————

2VDD - VTR

(VTR)(VDD - VTR)

tM = (t1+t2)= -RC In —————————

(2VDD - VTR)(2VDD)

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