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APPLICATION INFORMATION

0.1

µF

0.1

µF

Output

GND

TRIG

THRES

RESET

DISCH

CONT

OUT

GND

CIRCUIT

TRIGGER AND THRESHOLD VOLTAGE WAVEFORM

TLC555

6

1

3

8

5

4

7

2

t

c(H) [

C

T

(R

A )

R

B

) In 2 (In 2 + 0.693)

t

c(L) [

C

T

R

B

In 2

Period + tc(H) ) tc(L) [ CT (RA ) 2RB) In 2

Output driver duty cycle +

t

c(L)

t

c(H) )

t

c(L)

[ 1 –

R

B

R

A )

2R

B

Output waveform duty cycle +

t

c(H)

t

c(H) )

t

c(L)

[

R

B

R

A )

2R

B

TLC555-Q1

LinCMOS™ TIMER

SLFS078 – OCTOBER 2006

Figure 3. Astable Operation

as shown in the following equations.

The 0.1-

µF capacitor at CONT in Figure 3 decreases the period by about 10%.

The formulas shown above do not allow for any propagation delay times from the TRIG and THRES inputs to

DISCH. These delay times add directly to the period and create differences between calculated and actual

9

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