Datasheet SN74ls122 Datasheet

RETRIGGERABLE MONOSTABLE MULTIVIBRATORS

SN54/74LS122 SN54/74LS123

These dc triggered multivibrators feature pulse width control by three methods. The basic pulse width is programmed by selection of external resistance and capacitance values. The LS122 has an internal timing resistor that allows the circuits to be used with only an external capacitor. Once triggered, the basic pulse width may be extended by retriggering the gated low-level-active (A) or high-level-active (B) inputs, or be reduced by use of the overriding clear.

• Overriding Clear Terminates Output Pulse

• Compensated for V

and Temperature Variations

CC

• DC Triggered from Active-High or Active-Low Gated Logic Inputs

• Retriggerable for Very Long Output Pulses, up to 100% Duty Cycle

• Internal Timing Resistors on LS122

SN54/74LS123 (TOP VIEW)

(SEE NOTES 1 THRU 4)

1R

ext/

1

C

V

CC

16 15

123456

1A

C

ext

1B 1

1Q 2Q

ext

14 13 12 11 10 9

Q

CLR

1Q

CLR

SN54/74LS122 (TOP VIEW)

(SEE NOTES 1 THRU 4)

R

ext/

C

V

CC 14 13 12 11 10 9

ext

NC C

ext

CLR

Q Q

2Q 2

C

NC R

R

2

ext

int

Q

R

int

2B

7

2

ext/

C

ext

Q 8

2A

8

GND

RETRIGGERABLE MONOSTABLE

MULTIVIBRATORS

LOW POWER SCHOTTKY

J SUFFIX

CERAMIC

16

1

16

1

16

1

14

1

14

1

CASE 620-09

N SUFFIX

PLASTIC

CASE 648-08

D SUFFIX

SOIC

CASE 751B-03

J SUFFIX

CERAMIC

CASE 632-08

N SUFFIX

PLASTIC

CASE 646-06

Q

CLR

123456

A1 A2 B1 B2 CLR Q

NC — NO INTERNAL CONNECTION.

NOTES:

1. An external timing capacitor may be connected between C

2. To use the internal timing resistor of the LS122, connect R

3. For improved pulse width accuracy connect an external resistor between R VCC with R

4. T o obtain variable pulse widths, connect an external variable resistance between R and VCC.

open-circuited.

int

and R

ext

to VCC.

int

7

GND

ext/Cext

(positive).

ext/Cext

FAST AND LS TTL DAT A

5-1

and

int/Cext

D SUFFIX

14

1

SOIC

CASE 751A-02

ORDERING INFORMATION

SN54LSXXXJ Ceramic SN74LSXXXN Plastic SN74LSXXXD SOIC

SN54/74LS122 • SN54/74LS123

LS122

FUNCTIONAL TABLE

INPUTS OUTPUTS

CLEAR A1 A2 B1 B2 Q Q

L X X X X L H X H HXXLH X XXLXLH

X XXXLLH H LX↑H H LXH↑ H XL↑H H XLH↑ H H↓HH H ↓ ↓HH H ↓HHH

↑ LXHH ↑ XLHH

TYPICAL APPLICATION DATA

The output pulse tW is a function of the external components, C of C

and R

ext

≥1000 pF, the output pulse at VCC = 5.0 V and VRC =

ext

or C

ext

and R

on the LS122. For values

int

5.0 V (see Figures 1, 2, and 3) is given by

If C

ext

The C

tW = K R

ext Cext

is on pF and R

terminal of the LS122 and LS123 is an internal

ext

where K is nominally 0.45

is in kΩ then tW is in nanoseconds.

ext

connection to ground, however for the best system performance C

Care should be taken to keep R

should be hard-wired to ground.

ext

and C

as close to the

ext

monostable as possible with a minimum amount of inductance between the R

ext/Cext

junction and the R

ext/Cext

pin. Good groundplane and adequate bypassing should be designed into the system for optimum performance to insure that no false triggering occurs.

It should be noted that the C

pin is internally connected

ext

to ground on the LS122 and LS123, but not on the LS221. Therefore, if C

is hard-wired externally to ground, substitu-

ext

tion of a LS221 onto a LS123 socket will cause the LS221 to become non-functional.

The switching diode is not needed for electrolytic capacitance application and should not be used on the LS122 and LS123.

To find the value of K for C

≥ 1000 pF, refer to Figure 4.

ext

V ariations on VCC or VRC can cause the value of K to change, as can the temperature of the LS123, LS122. Figures 5 and 6 show the behavior of the circuit shown in Figures 1 and 2 if

LS123

FUNCTIONAL TABLE

INPUTS OUTPUTS

CLEAR A B Q Q

L X X L H X H XLH

X X LLH H L ↑ H ↓ H ↑ L H

separate power supplies are used for VCC and VRC. If VCC is tied to VRC, Figure 7 shows how K will vary with VCC and temperature. Remember, the changes in R

ext

and C

ext

with

temperature are not calculated and included in the graph.

As long as C (SN74LS122/123) or 5K ≤ R the change in K with respect to R

If C

≤ 1000 pF the graph shown on Figure 8 can be used

ext

≥ 1000 pF and 5K ≤ R

ext

≤ 160 K (SN54LS122/123),

ext

is negligible.

ext

≤ 260K

ext

to determine the output pulse width. Figure 9 shows how K will change for C

≤ 1000 pF if VCC and VRC are connected to the

ext

same power supply. The pulse width tW in nanoseconds is approximated by

tW = 6 + 0.05 C

(pF) + 0.45 R

ext

(kΩ) C

+ 1 1.6 R

ext

In order to trim the output pulse width, it is necessary to include a variable resistor between VCC and the R or between VCC and the R and 12 show how this can be done. R

pin of the LS122. Figure 10, 1 1,

ext

remote should be kept

ext

ext/Cext

as close to the monostable as possible.

Retriggering of the part, as shown in Figure 3, must not occur before C have any effect. The discharge time of C guaranteed to be less than 0.22 C C

(pF).

ext

is discharged or the retrigger pulse will not

ext

in nanoseconds is

ext

(pF) and is typically 0.05

For the smallest possible deviation in output pulse widths from various devices, it is suggested that C

be kept

ext

≥ 1000 pF.

FAST AND LS TTL DATA

5-2

SN54/74LS122 • SN54/74LS123

GUARANTEED OPERATING RANGES

Symbol Parameter Min Typ Max Unit

V

CC

T

A

I

OH

I

OL

R

ext

C

ext

R

ext/Cext

Supply Voltage 54

Operating Ambient Temperature Range 54

Output Current — High 54, 74 –0.4 mA Output Current — Low 54

External Timing Resistance 54

External Capacitance 54, 74 No Restriction Wiring Capacitance at R

ext/Cext

Terminal 54, 74 50 pF

74

4.5

4.75 –55

0

5.0

5.0 25

25

5.5

5.25 125

70

4.0

8.0

180 260

WAVEFORMS

V

°C

mA

kΩ

B INPUT

Q OUTPUT

RETRIGGER

PULSE

t

W

(See Application Data)

OUTPUT WITHOUT RETRIGGER

EXTENDING PULSE WIDTH

B INPUT

CLEAR INPUT CLEAR PULSE

OUTPUT WITHOUT CLEAR PULSE

Q OUTPUT

OVERRIDING THE OUTPUT PULSE

FAST AND LS TTL DATA

5-3

SN54/74LS122 • SN54/74LS123

VILI

LOW Volt

V

pg

VOHOutput HIGH Volt

CC

,

OH

,

IN IH

VOLOutput LOW Volt

V

IIHI

HIGH C

t

ICCP

t

A

V

MAX

PLH

pg y,

C

ext

0

PLH

pg y,

ext

PLH

pg y,

ext

p,

ext

,

DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)

Limits

Symbol Parameter

V

IH

V

IK

I

IL

I

OS

Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.

Input HIGH Voltage 2.0 V

nput

Input Clamp Diode Voltage –0.65 –1.5 V VCC = MIN, IIN = –18 mA

nput

Input LOW Current –0.4 mA VCC = MAX, VIN = 0.4 V Short Circuit Current (Note 1) –20 –100 mA VCC = MAX

ower Supply Curren

age

urren

54 0.7 74 0.8

54 2.5 3.5 V 74 2.7 3.5 V

54, 74 0.25 0.4 V IOL = 4.0 mA

74 0.35 0.5 V IOL = 8.0 mA

LS122 11 LS123 20

Min Typ Max

20 µA VCC = MAX, VIN = 2.7 V

0.1 mA VCC = MAX, VIN = 7.0 V

Unit Test Conditions

Guaranteed Input HIGH Voltage for All Inputs

Guaranteed Input LOW Voltage for All Inputs

VCC = MIN, IOH = MAX, VIN = V or VIL per Truth Table

m

CC

=

IH

VCC = VCC MIN,

=

or

IN

IL

per Truth Table

IH

AC CHARACTERISTICS (T

Symbol Parameter

t

PLH

t

PHL

t

PLH

t

PHL

t

PLH

t

PHL

t

Wmin

tWQ A to B to Q 4.0 4.5 5.0 µs

Propagation Delay, A to Q Propagation Delay, A to Q

Propagation Delay, B to Q Propagation Delay, B to Q

Propagation Delay, Clear to Q Propagation Delay, Clear to Q

A or B to Q 116 200 ns

AC SETUP REQUIREMENTS (T

Symbol Parameter

t

W

Pulse Width 40 ns

= 25°C, VCC = 5.0 V)

A

= 25°C, VCC = 5.0 V)

A

Limits

Min Typ Max

23 33 32 45 23 44 34 56 28 45 20 27

Limits

Min Typ Max

Unit Test Conditions

ns

C

= 0

ext

CL = 15 pF

ns

Unit Test Conditions

R

= 5.0 kΩ

ext

RL = 2.0 kΩ

C

= 1000 pF, R

ext

CL = 15 pF, RL = 2.0 kΩ

= 10 kΩ,

ext

FAST AND LS TTL DATA

5-4

SN54/74LS122 • SN54/74LS123

V

CC

0.1

µ

F

/

V

CC

Q

P

out

C

ext

CLR B2 B1 A2 A1

C

ext

V

RC

R

ext

R C

LS122

GND

ext ext

V

CC

P

in

51

Ω

V

RC

R

ext

C

ext

C

extRext

CLR

1/2 LS123

B

A

C

ext

GND

V

CC

0.1

µ

F

/

V

CC

Q

P

out

P

in

CC

51

Ω

Figure 1 Figure 2

P

in

P

out

t

W

10

1

µ

ext

0.1

EXTERNAL CAPACITANCE, C ( F)

0.01

0.001

0.3 0.35 0.4 0.45 0.5 0.55

Figure 3

5K ≤ R

K

Figure 4

RETRIGGER

≤ 260K

ext

FAST AND LS TTL DATA

5-5

SN54/74LS122 • SN54/74LS123

0.55 VRC = 5 V

C

= 1000 pF

ext

0.5 –55

°

0

25°C 70°C

125

°

100000

C

V

CC

K

0.45

0.4

0.35

4.5 5 5.5

Figure 5. K versus V

0.55

0.5

VCC = 5 V C

= 1000 pF

ext

–55°C

0°C

K

0.45

0.4

0.35

4.5 5 5.5

70°C

125°C

V

RC

Figure 6. K versus V

RC

25°C

0.55 C

= 1000 pF

ext

0.5

K

0.45

0.4

0.35

4.5 5 5.5

–55

°

C

°

C

0

°

C

25 70

°

C

125°C

VCC = V

RC

Figure 7. K versus VCC and V

RC

10000

1000

, OUTPUT PULSE WIDTH (ns)

W

t

100

10

1 10 100 1000

R

ext

R

ext

= 260 k = 160 k

Ω Ω

R

= 80 k

Ω

ext

R

= 40 k

Ω

ext

R

= 20 k

Ω

ext

R

= 10 k

Ω

ext

R

= 5 k

Ω

ext

C

, EXTERNAL TIMING CAPACITANCE (pF)

ext

Figure 8

FAST AND LS TTL DATA

5-6

0.65

SN54/74LS122 • SN54/74LS123

C

= 200 pF

ext

–55

°

C

0.6

K

0.55

0.5

4.5 4.75 5 5.25 5.5

25

70

125

0°C

°

C

VCC VOLTS

Figure 9

R PIN 7 OR 15

C

PIN 6 OR 14

ext

Figure 10. LS123 Remote Trimming Circuit

FAST AND LS TTL DATA

5-7

V

CC

R

ext

REMOTE

SN54/74LS122 • SN54/74LS123

PIN 9

PIN 13

PIN 11

OPEN

C

ext

R

ext

V

CC

R

ext

REMOTE

Figure 11. LS122 Remote Trimming Circuit Without R

PIN 9 PIN 13

PIN 11

Figure 12. LS122 Remote Trimming Circuit with R

ext

V

CC

R

ext

REMOTE

int

FAST AND LS TTL DATA

5-8