The IC 4047 is one of those devices which promises an unlimited range of circuit application solutions. The IC is so versatile that on many occasions it easily outsmarts it's close rival, the IC 555, let's study the datasheet and pinout details of this versatile chip.
Main Datasheet and Specifications:
In-built oscillator with variable frequency option through an external RC network.
Complementary push-pull outputs with a separate active clock output, the clock output is actually an extension of the internal oscillator frequency output.
Duty cycle locked to 50% for precision, fail proof operation of the external stages.
The IC 4047 can be configured as a free running astable MV, and also as a monostable MV.
In the astable mode the chip provides the option of integrating external triggering inputs, also called true gating and complement gating modes.
The monostable mode enables positive edge triggering as well as negative edge triggering of the IC.
It further allows retriggerable feature for extending the output timing to the desired calculated level. Meaning after the normal trigger is applied to the IC, more number subsequent triggers can be applied so that the output adds up the timing, generating further delay at the output.
Internal Logic Diagram
The following explanation suggests how the pinouts of the IC 4047 may be configured for implementing the above discussed operating modes:
In the free running astable mode, connect pins 4, 5, 6, 14 to positive or Vdd, connect pins 7, 8, 9, 12 to ground or Vss.
Vdd must be supplied with a recommended 3V to 15V and maximum 18V (absolute).
In gated astable mode connect pins 4, 6, 14 to positive or Vdd, connect pins 7, 8, 9, 12 to ground or Vss, connect pin 5 to the reset pin of the external trigger IC, while output of the external chip to pin 4 of the IC 4047.
For the above modes, the output may be obtained across pin 10, 11 (push-pull) while clocks at pin 13.
In positive trigger monostable mode, connect pins 4, 14 to positive or Vdd, connect pins 5, 6, 7, 9, 12 to ground or Vss, connect pin 8 to the reset pin of the external trigger IC, while output of the external chip to pin 6 of the IC 4047.
For the above modes, the output may be obtained across pin 10, 11.
Fundamental Free Running Astable Mode Circuit Diagram Using IC 4047
As shown in the figure above, the IC 4047 can be used as a free running astable multivibrator or oscillator by configuring the chip in the above suggested method.
Here R1, P1 and C1 determine the oscillator frequency of the IC and the output at pin10, 11 and 13.
Basically R1, P1 togeter must not be less than 10K, and above 1M, while C1 should not be less than 100pF (higher value have no restrictions) in order to maintain proper functioning of the chip.
Pin 10 and 11 are complementary outputs which behave in a push-pull manner, meaning when pin10 is high pin11 is low and vice versa.
Pin 13 is the clock output of the IC 4047, each high pulse measured at this output enables pin10/11 to change positions with their logic levels, while low logics does not influence any response on pin10/11.
Pin13 is normally kept open when not in use, it may be applied in cases where a frequency or pulsed output may be required for the other stages of the circuit for enhancing purposes, such as for making modified PWM based inverters etc.
The IC is best suited for all types of inverter, converter, SMPS and timer applications.
One typical simple square wave inverter application using the IC 4047 can be witnessed below:
The formula for calculating the frequency or the RC components are:
f = 1/8.8RC at pin#10 and pin#11
f = 1/4.4RC at pin#13
Where f is in Hz, R in Ohms and C in Farads.
Pulse time may be obtained by solving:
t = 2.48RC where t is in seconds, R in Ohms and C in Farads