HEF4047BF Philips Semiconductors, HEF4047BF Datasheet - Page 13

• Manufacturer Part Number: HEF4047BF
• Description: Monostable/astable multivibrator
• Manufacturer: Philips Semiconductors

Philips Semiconductors
5. Timing component limitations
The capacitor used in the circuit should be non-polarized and have low leakage (i.e. the parallel resistance of the
capacitor should be an order of magnitude greater than the external resistor used).
There is no upper or lower limit for either R
However, in consideration of accuracy, C
this capacitance can be measured and taken into account).
R
The recommended values for R
should be:
6. Power consumption
In the standby mode (monostable or astable), power dissipation will be a function of leakage current in the circuit.
For dynamic operation, the power needed to charge the external timing capacitor C
Because the power dissipation does not depend on R
of C
Typical power consumption in astable mode is shown in Figs 10, 11 and 12.
January 1995
Astable mode:
Monostable mode:
t
Monostable/astable multivibrator
must be much larger than the LOCMOS ‘ON’ resistance in series with it, which typically is hundreds of ohms.
t
. The value of R would depend on the desired period (within the limitations discussed previously).
C
10 k
t
100 pF, up to any practical value,
R
t
1 M .
P = 2 C
P = 4 C
P =
-------------------------------------------------------------------- - f at output pins 10 and 11
2 9 C
t
t
V
V
t
and C
2
2
f (f at output pin 13)
f (f at output pins 10 and 11)
t
V
2
t
T
to maintain agreement with previously calculated formulae without trimming
t
duty cycle
must be much larger than the inherent stray capacitance in the system (unless
t
or C
t
value to maintain oscillation.
t
, a design for minimum power dissipation would be a small value
13
t
is given by the following formulae:
Product specification
HEF4047B
MSI