TLC551 Datasheet, PDF (11/16 Pages) Texas Instruments – LinCMOSE TIMERS

TLC551, TLC551Y
LinCMOS™ TIMERS
SLFS044B – FEBRUARY 1984 – REVISED SEPTEMBER 1997
APPLICATION INFORMATION
The equations below provide better agreement with measured values.
ƪ ǒ Ǔƫ + ) ₎ tc(H)
CT (RA
RB) In
3 – exp
– tPLH
CT (RB ron)
) tPHL
ƪ ǒ Ǔƫ + ) ₎ tc(L)
CT (RB
ron) In
3 – exp
– tPHL
CT (RA RB)
) tPLH
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%
tc(H)
tc(H) tc(L)
require
that
tc(H)
tc(L)
<1
and
possibly
R_A
≤
r_on.
These
conditions can be difficult to obtain.
In monostable applications, the trip point of the trigger input 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.
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