74HC4538 [HITACHI]

Dual Precision Retriggerable/Resettable Monostable Multivibrators; 双路精密可重触发/复式单稳态多谐振荡器


型号：	74HC4538
厂家：	HITACHI SEMICONDUCTOR
描述：	Dual Precision Retriggerable/Resettable Monostable Multivibrators 双路精密可重触发/复式单稳态多谐振荡器振荡器
文件：	总16页 (文件大小：83K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

HD74HC4538

Dual Precision Retriggerable/Resettable Monostable

Multivibrators

Description

Each multivibrator features both a negative, A, and a positive, B, transition triggered input, either of which

can be used as an inhibit input. Also included is a clear input that when taken low resets the one short. The

HD74HC4538 is retriggerable. That is, it may be triggered repeatedly while their outputs are generating a

pulse and the pulse will be extended.

Pulse width stability over a wide range of temperature. The output pulse equation is simply: t_w= 0.7 (R)

(C).

Features

•

High Speed Operation: t_pd(A or B to Y) = 22 ns typ (C_L= 50 pF)

High Output Current: Fanout of 10 LSTTL Loads

Wide Operating Voltage: V_CC= 2 to 6 V

Low Input Current: 1 µA max

Low Quiescent Supply Current

Function Table

Inputs

Outputs

C_D

Not triggered

X :

Irrelevant

HD74HC4538

Pin Arrangement

T_1A

T_2A

CD_A

A_A

16 V_CC

15 T_1B

14 T_2B

13 CD_B

12 A_B

11 B_B

10 Q_B

T₁

T₂

T₁

T₂

B_A

Q_A

GND

Q_B

(Top view)

HD74HC4538

Block Diagram

C_X

R_X

V_CC

T_1A

T_2A

Q_A

A_A

B_A

C_DA

C_X

R_X

V_CC

T_1B

T_2B

Q_B

A_B

B_B

C_DB

R_Xand C_Xare external components

HD74HC4538

Absolute Maximum Ratings

Item

Symbol

V_CC

Rating

Unit

Supply voltage range

Input voltage

–0.5 to +7.0

–0.5 to V_CC+ 0.5

±20

Vin

Output voltage

Vout

I_IK

DC input diode current

DC input diode current pin 2, 14

DC output diode current

DC current drain per pin

DC current drain per V_CC, GND

Power dissipation per package

Storage temperature

°C

I_IK

±30

I_OK

±20

Iout

I_CC, I_GND

P_T

±25

±50

500

Tstg

–65 to +150

HD74HC4538

DC Characteristics

Ta = –40 to

Ta = 25°C

+85°C

Item

Symbol V_CC(V) Min Typ Max Min Max Unit Test Conditions

Input voltage

V_IH

2.0

4.5

6.0

2.0

4.5

6.0

2.0

4.5

6.0

4.5

6.0

2.0

4.5

6.0

4.5

6.0

1.5

—

0.5

1.5

3.15

4.2

—

3.15 —

—

4.2

—

V_IL

0.5

1.35

1.8

—

1.35 —

1.8

—

Output voltage

V_OH

1.9 2.0

4.4 4.5

5.9 6.0

4.18 —

5.68 —

1.9

4.4

5.9

4.13

5.63

—

Vin = V_IHor V_ILI_OH= –20 µA

—

I_OH= –4 mA

I_OH= –5.2 mA

—

V_OL

—

0.0 0.1

0.1

0.33

Vin = V_IHor V_ILI_OL= 20 µA

—

0.26 —

I_OL= 4 mA

I_OL= 5.2 mA

Input current

Iin

±0.1 —

±1.0 µA

220 µA

Vin = V_CCor GND

Quiescent supply I_CC

current

130 —

Vin = V_CCor GND,

Q_A= Q_B= GND, Iout = 0 µA

(standby state)

Current drain

(active state)

I_CC

6.0

—

130 —

220 µA

Vin = V_CCor GND,

Q_A= Q_B= V_CC

Pin 2, 14 = 0.5 V_CC

HD74HC4538

AC Characteristics (C_L= 50 pF, Input t_r= t_f= 6 ns)

Ta = –40 to

+85°C

Ta = 25°C

Symbol V_CC(V) Min Typ Max Min Max Unit Test Conditions

Item

Propagation delay t_PLH

time

2.0

4.5

6.0

2.0

4.5

6.0

2.0

4.5

6.0

2.0

4.5

6.0

2.0

4.5

6.0

3.0

5.0

3.0

5.0

3.0

5.0

3.0

5.0

—

235 —

295 ns

A or B to Q

C_Dto Q

22 47

—

t_PHL

t_PLH

260 —

325 ns

23 52

—

235 —

295 ns

17 47

—

235 —

295 ns

C_Dto Q

—

100

—

Pulse width

t_w

—

A, B, C_D

Output pulse width t_WQ

150 —

100 —

µs

R_X= 1 kΩ, C_X= 12 pF

—

1.3

—

R_X= 10 kΩ, C_X= 100 pF

R_X= 10 kΩ, C_X= 1000 pF

R_X= 10 kΩ, C_X= 10000 pF

R_X= 10 kΩ, C_X= 1000 pF

—

Pulse width match ∆t_WQ

between circuits in

the same package

±0.1 —

Caution in use: In order to prevent any malfunctions due to noise, connect a high frequency performance

capacitor between V_CCand GND, and keep the wiring between the External components and

Cext, Rext/Cext pins as short as possible.

HD74HC4538

Circuit Operation

Fig. 3 shows the HC4538 configured in the retriggerable mode. Briefly, the device operates as follows

(refer to Fig. 1): In the quiescent state, the external timing capacitor, C_X, is charged to V_CC. When a trigger

occurs, the Q output goes high and C_Xdischarges quickly to the lower references voltage (Vref Lower 1/3

V_CC). C_Xthen charges, through R_X, back up to the upper reference voltage (Vref Upper 2/3 V _CC), at

which point the one-shot has timed out and the Q output goes low.

The following, more detailed description of the circuit operation refers to both the function diagram (Fig. 1)

and the timing diagram (Fig. 2)

Quiescent State

In the quiescent state, before an input trigger appears; the output latch is high and the reset latch is high (1

in Fig. 2). Thus the Q output (pin 6 or 10) of the monostable multivibrator is low (2 Fig. 2).

The output of the trigger-control circuit is low (3), and transistors M1, M2, and M3 are turned off. The

external timing capacitor, C_X, is charged to V_CC(4), and the upper reference circuit has a low output (5).

Transistor M4 is turned on and analog switch S1 is turned off. Thus the lower reference circuit has V_CCat

the noninverting input and a resulting low output (6).

In addition, the output of the trigger-control reset circuit is low.

Trigger Operation

The HC4538 is triggered by either a rising-edge signal as input A (7) or a falling-edge signal at input B (8),

with the unused trigger input and the Reset input held at the voltage levels shown in the Function Table.

Either trigger signal will cause the output of the trigger-control circuit to go high (9). The trigger-control

circuit going high simultaneously initiates three events. First, the output latch goes low, thus taking the Q

output of the HC4538 to a high state (10). Second, transistor M3 is turned on, which allows the external

timing capacitor, C_X, to rapidly discharge toward ground (11). (Note that the voltage across C_Xappears at

the input of the upper reference circuit comparator). Third, transistor M4 is turned off and analog switch

S1 is turned on, thus allowing the voltage across C_Xto also appear at the input of the lower reference circuit

comparator.

When C_Xdischarges to the reference voltage of the lower reference circuit (12), the outputs of both

reference circuits will be high (13). The trigger-control circuit flip-flop to a low state (14). This turns

transistor M3 off again, allowing C_Xto begin to charge back up toward V_CC, with a time constant t = R_XC_X

(15). In addition, transistor M4 is turned on and analog switch S1 is turned off. Thus a high voltage level

is applied to the input of the lower reference circuit comparator, causing its output to go low (16). The

monostable multivibrator may be retriggered at any time after the trigger-control circuit goes low.

When C_Xcharges up to the reference voltage of the upper reference circuit (17), the output of the upper

reference circuit goes low (18). This causes the output latch to toggle, taking the Q output of the HC4538

to a low state (19), and completing the time-out cycle.

HD74HC4538

Reset Operation

A low voltage applied to the Reset pin always forces the Q output of the HC4538 to a low state.

The timing diagram illustrates the case in which reset occurs (20) while C_Xis charging up toward the

reference voltage of the upper reference circuit (21). When a reset occurs, the output of the reset latch goes

low (22), turning on transistor M1. Thus C_Xis allowed to quickly charge up to V_CC(23) to await the next

trigger signal.

Retrigger Operation

When used in the retriggerable mode (Fig. 3), the HC4538 may be retriggered during timing out of the

output pulse at any time after the trigger-control circuit flip-flopw has been reset (24). Because the trigger-

control circuit flip-flop resets shortly after C_Xhas discharged to the reference voltage of the lower reference

circuit (25), the minimum retrigger time, t_rr(Switching Waveform 1) is a function of internal propagation

delays and the discharge time of C_X:

Fig. 4 shows the device configured in the non-retriggerable mode.

Power-Down Considerations

Large values of C_Xmay cause problems when powering down the HC4538 because of the amount of

energy stored in the capacitor. When a system containing this device is powered down, the capacitor may

discharge from V_CCthrough the input protection diodes at pin 2 or pin 14. Current through the protection

diodes must be limited to 30 mA; therefore, the turn-off time of the V_CCpower supply must not be faster

than t = V_CC•C_X/(30 mA). For example, if V_CC= 5 V and C_X= 15 µF, the V_CCsupply must turn off no

faster than t = (5 V)•(15 µF)/30 mA = 2.5 ms. This is usually not a problem because power supplies are

heavily filtered and cannot discharge at this rate.

When a more rapid decrease of V_CCto zero voltage occurs, the HC4538 may sustain damage. To avoid this

possibility, use an external clamping diode.

HD74HC4538

VCC

2, 14

VCC

Upper Reference

Circuit

Output Latch

2kΩ

–

Vref Upper

6, 10

Lower Reference

Circuit

VCC

M⁴

7, 9

–

Trigger-Control Circuit

4, 12

5, 11

Vref Lower

Trigger-Control

Reset Circuit

3, 13

C^D

Reset Latch

Fig. 1 Function Diagram

HD74HC4538

Quiescent

State

Trigger Cycle (A Input) Trigger Cycle (B Input)

Reset

Retrigger

trr

Trigger Input A

(Pin 4 or 12)

Trigger Input B

(Pin 5 or 11)

Reset Input C

(Pin 3 or 13)

Trigger-Control

Circuit Output

T₂Input

(Pin 2 or 14)

Vref Upper

Vref Lower

Upper Reference

Circuit Output

Lower Reference

Circuit Output

Reset Latch

Output

Q Output

(Pin 6 or 10)

t_WQ

t_WQ+t_rr

t_{W (H)}

50%

t_{W (L)}

50%

t_PLH

t_WQ

t_PLH

50%

t_PHL

50%

t_f

t_r

90%

10%

50%

t_{W (L)}

t_PHL

50%

t_WQ+t_rr

(Retriggered Pulse)

t_TLH

90%

10%

50%

t_THL

90%

t_PLH

50%

10%

Fig. 2 Timing Diagram

HD74HC4538

C_X

R_X

V_CC

T₁

T₂

Rising-Edge

Trigger

C_D

C_X

R_X

V_CC

T₁

T₂

Rising-Edge

Trigger

C_D

Fig. 3 Retriggerable Monostable Circuitry

HD74HC4538

C_X

R_X

V_CC

T₁

T₂

Falling-Edge

Trigger

C_D

C_X

R_X

V_CC

T₁

T₂

Falling-Edge

Trigger

C_D

Fig. 4 Nonritriggerable Monostable Circuitry

Unit: mm

19.20

20.00 Max

1.3

1.11 Max

7.62

+ 0.13

– 0.05

0.25

2.54 ± 0.25

0.48 ± 0.10

0° – 15°

Hitachi Code

DP-16

JEDEC

EIAJ

Conforms

Weight (reference value) 1.07 g

Unit: mm

10.06

10.5 Max

+ 0.20

7.80

– 0.30

0.80 Max

1.15

0° – 8°

1.27

0.70 ± 0.20

*0.42 ± 0.08

0.40 ± 0.06

0.15

0.12

Hitachi Code

JEDEC

EIAJ

FP-16DA

—

Conforms

*Dimension including the plating thickness

Base material dimension

Weight (reference value) 0.24 g

Unit: mm

9.9

10.3 Max

1.27

+ 0.10

6.10

– 0.30

1.08

0.635 Max

0° – 8°

+ 0.67

0.60

– 0.20

*0.42 ± 0.08

0.40 ± 0.06

0.15

0.25

Hitachi Code

JEDEC

EIAJ

FP-16DN

Conforms

*Dimension including the plating thickness

Base material dimension

Weight (reference value) 0.15 g

Cautions

1. Hitachi neither warrants nor grants licenses of any rights of Hitachi’s or any third party’s patent,

Hitachi bears no responsibility for problems that may arise with third party’s rights, including

intellectual property rights, in connection with use of the information contained in this document.

2. Products and product specifications may be subject to change without notice. Confirm that you have

received the latest product standards or specifications before final design, purchase or use.

3. Hitachi makes every attempt to ensure that its products are of high quality and reliability. However,

contact Hitachi’s sales office before using the product in an application that demands especially high

quality and reliability or where its failure or malfunction may directly threaten human life or cause risk

of bodily injury, such as aerospace, aeronautics, nuclear power, combustion control, transportation,

traffic, safety equipment or medical equipment for life support.

4. Design your application so that the product is used within the ranges guaranteed by Hitachi particularly

for maximum rating, operating supply voltage range, heat radiation characteristics, installation

conditions and other characteristics. Hitachi bears no responsibility for failure or damage when used

beyond the guaranteed ranges. Even within the guaranteed ranges, consider normally foreseeable

failure rates or failure modes in semiconductor devices and employ systemic measures such as fail-

safes, so that the equipment incorporating Hitachi product does not cause bodily injury, fire or other

consequential damage due to operation of the Hitachi product.

5. This product is not designed to be radiation resistant.

6. No one is permitted to reproduce or duplicate, in any form, the whole or part of this document without

written approval from Hitachi.

7. Contact Hitachi’s sales office for any questions regarding this document or Hitachi semiconductor

products.

Hitachi, Ltd.

Semiconductor & Integrated Circuits.

Nippon Bldg., 2-6-2, Ohte-machi, Chiyoda-ku, Tokyo 100-0004, Japan

Tel: Tokyo (03) 3270-2111 Fax: (03) 3270-5109

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For further information write to:

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(America) Inc.

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74HC4538 [HITACHI]

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