TLC551, TLC551Y

LinCMOS

™ TIMERS

SLFS044B – FEBRUARY 1984 – REVISED SEPTEMBER 1997

10

POST OFFICE BOX 655303

APPLICATION INFORMATION

0.1

µF

0.1

µF

CT

CL

RL

Output

RB

RA

GND

TRIG

THRES

RESET

DISCH

CONT

VDD

OUT

VDD

2/3 VDD

1/3 VDD

GND

tPHL

tPLH

tc(H)

tc(L)

CIRCUIT

TRIGGER AND THRESHOLD VOLTAGE WAVEFORM

TLC551

3

8

5

4

7

6

2

1

VDD

Figure 3. Astable Operation

shown in the equations below.

t

c(H) [

C

T

(R

A )

R

B

)In2 (In 2

+ 0.693)

t

c(L) [

C

T

R

B

In 2

Period

+ t

c(H) )

t

c(L) [

C

T

(R

A )

2R

B

)In2

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

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 TRIG and THRES to DISCH. These

delay times add directly to the period and create differences between calculated and actual values that increase with