CD4047BE Low-Power Monostable/Astable Multivibrator

Description:

CD4047B consists of a gatable astable multivibrator with logic techniques incorporated to permit positive or negative edge-triggered monostable multivibrator action with retriggering and external counting options.

Inputs include +TRIGGER, -TRIGGER, ASTABLE, ASTABLE\, RETRIGGER, and EXTERNAL RESET. Buffered outputs are Q\, Q and OSCILLATOR. In all modes of operation, and external capacitor must be connected between C-Timing and RC-Common terminal, and an external resistor must be connected between the R-Timing and RC-Common terminals.

Astable operation is enabled by a high level on the STABLE input or a low level on the ASTABLE\ input, or both. 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.

The CD4047B triggers in the monostable mode when a positive-going edge occurs on the +TRIGGER-input while the -TRIGGER is held low. INput pulses may be of any duration relative to the output pulse.

If retrigger capability is desired, the RETRIGGER input is pulsed. The retriggerable mode of operation is limited to positive-going edge. The CD4047B will retrigger as long as the RETRIGGER-input is high, with or without transitions (See Fig. 34).

An external countdown option can be implemented by 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 ensures no output pulse during an "ON" power condition. This input can also be activated to terminate the output pulse at any tine. For monostable operation, whenever V_DD is applied, an internal power-on reset circuit will clock the Q output low within one output period (t_M).

Features:

• Lower power consumption: special CMOS oscillator configuration
• Monostable (one-shot) or astable (free-running) operation
• True and complemented buffered outputs
• Only one external R anc C required
• Buffered inputs
• 100% tested for quiescent current at 20 V
• Standardized, symmetrical output characteristics
• 5-V, 10-V, and 15-V parametric ratings
• Meets all requirements of JEDEC Tentative Standard No. 13B, "Standard Specifications for Description of 'B' Series CMOS Devices"
• Monostable Multivibrator Features:
  • Positive-or negative-edge trigger
  • Output pulse width independent of trigger pulse duration
  • Retriggerable option for pulse width expansion
  • Internal power-on reset circuit
  • Long pulse widths possible using small RC components by means of external counter provision
  • Fast recovery time essentially independent of pulse width
  • Pulse-width accuracy maintained at duty cycles approaching 100%
• Astable Multivibrator Features:
• Free-running or gatable operating modes
• 50% duty cycle
• Oscillator output available
• Good astable frequency stability:
     Frequency deviation:
       = ±2% + 0.03%/°C @ 100 kHz
       = ±0.5% +0.015%/°C @ 10 kHz (circuits "trimmed" to frequency V_DD = 10 V ± 10%

Applications:

• Digital equipment where low-power dissipation and/or high noise immunity are primary design requirements:
• Envelope detection
• Frequency multiplication
• Frequency division
• Frequency discriminators
• Timing circuits
• Time-delay applications