Datasheet

TLC555, TLC555Y
LinCMOS TIMERS
SLFS043C – SEPTEMBER 1983 – REVISED SEPTEMBER 1997
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
The equations below provide better agreement with measured values.
t
c(H)
C
T
(R
A
R
B
)In 3–exp
–t
PLH
C
T
(R
B
r
on
)
t
PHL
t
c(L)
C
T
(R
B
r
on
)In
3–exp
–t
PHL
C
T
(R
A
R
B
)
t
PLH
These equations and those given earlier are similar in that a time constant is multiplied by the logarithm of a number
or function. The limit values of the logarithmic terms must be between In 2 at low frequencies and In 3 at extremely
high frequencies. For a duty cycle close to 50%, an appropriate constant for the logarithmic terms can be substituted
with good results. Duty cycles less than 50%
t
c(H)
t
c(H)
t
c(L)
require that
t
c(H)
t
c(L)
<1 and possibly R
A
≤ r
on
. These
conditions can be difficult to obtain.
In monostable applications, the trip point on TRIG can be set by a voltage applied to CONT. An input voltage between
10% and 80% of the supply voltage from a resistor divider with at least 500-µA bias provides good results.