1. General description The 74HC123; 74HCT123 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output pulse width control by three methods: 1. The basic pulse time is programmed by selection of an external resistor (R EXT ) and capacitor (C EXT ). 2. Once triggered, the basic output pulse width may be extended by retriggering the gated active LOW-going edge input (n A) or the active HIGH-going edge input (nB). By repeating this process, the output pulse period (nQ = HIGH, n Q = LOW) can be made as long as desired. Alternatively an output delay can be terminated at any time by a LOW-going edge on input n RD, which also inhibits the triggering. 3. An internal connection from n RD to the input gates makes it possible to trigger the circuit by a HIGH-going signal at input n RD as shown in the function table. Schmitt-trigger action in the n A and nB inputs, makes the circuit highly tolerant to slower input rise and fall times. The 74HC123; 74HCT123 is identical to the 74HC423; 74HCT423 but can be triggered via the reset input. 2. Features ■ DC triggered from active HIGH or active LOW inputs ■ Retriggerable for very long pulses up to 100 % duty factor ■ Direct reset terminates output pulse ■ Schmitt-trigger action on all inputs except for the reset input ■ ESD protection: ◆ HBM EIA/JESD22-A114-B exceeds 2000 V ◆ MM EIA/JESD22-A115-A exceeds 200 V. ■ Specified from -40 °C to +80 °C and from -40 °C to +125 °C. 74HC123; 74HCT123 Dual retriggerable monostable multivibrator with reset Rev. 03 — 11 May 2004 Product data sheet
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74HC123; 74HCT123 Dual retriggerable monostable ...The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output pulse width control by three methods: 1. The basic
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1. General description
The 74HC123; 74HCT123 are high-speed Si-gate CMOS devices and are pin compatiblewith low power Schottky TTL (LSTTL). They are specified in compliance with JEDECstandard no. 7A.
The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with outputpulse width control by three methods:
1. The basic pulse time is programmed by selection of an external resistor (REXT) andcapacitor (CEXT).
2. Once triggered, the basic output pulse width may be extended by retriggering thegated active LOW-going edge input (nA) or the active HIGH-going edge input (nB). Byrepeating this process, the output pulse period (nQ = HIGH, nQ = LOW) can be madeas long as desired. Alternatively an output delay can be terminated at any time by aLOW-going edge on input nRD, which also inhibits the triggering.
3. An internal connection from nRD to the input gates makes it possible to trigger thecircuit by a HIGH-going signal at input nRD as shown in the function table.
Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slowerinput rise and fall times.
The 74HC123; 74HCT123 is identical to the 74HC423; 74HCT423 but can be triggeredvia the reset input.
2. Features
DC triggered from active HIGH or active LOW inputs
Retriggerable for very long pulses up to 100 % duty factor
Direct reset terminates output pulse
Schmitt-trigger action on all inputs except for the reset input
ESD protection:
HBM EIA/JESD22-A114-B exceeds 2000 V
MM EIA/JESD22-A115-A exceeds 200 V.
Specified from −40 °C to +80 °C and from −40 °C to +125 °C.
74HC123; 74HCT123Dual retriggerable monostable multivibrator with resetRev. 03 — 11 May 2004 Product data sheet
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
3. Quick reference data
[1] CPD is used to determine the dynamic power dissipation (PD in µW):
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
[1] For other REXT and CEXT combinations see Figure 10. If CEXT > 10 nF, the next formula is valid:
tW = K × REXT × CEXT, where:
tW = typical output pulse width in ns;
REXT = external resistor in kΩ;
CEXT = external capacitor in pF;
K = constant = 0.45 for VCC = 5.0 V and 0.48 for VCC = 2.0 V.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is approximately 7 pF.
[2] The time to retrigger the monostable multivibrator depends on the values of REXT and CEXT. The output pulse width will only beextended when the time between the active-going edges of the trigger input pulses meets the minimum retrigger time. If CEXT >10 pF,the next formula (at VCC = 5.0 V) for the set-up time of a retrigger pulse is valid:
trt = 30 + 0.19 × REXT × CEXT0.9 + 13 × REXT
1.05, where:
trt = retrigger time in ns;
CEXT = external capacitor in pF;
REXT = external resistor in kΩ.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[3] When the device is powered-up, initiate the device via a reset pulse, when CEXT < 50 pF.
[4] CPD is used to determine the dynamic power dissipation (PD in µW):
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
[1] For other REXT and CEXT combinations see Figure 10. If CEXT > 10 nF, the next formula is valid:
tW = K × REXT × CEXT, where:
tW = typical output pulse width in ns;
REXT = external resistor in kΩ;
CEXT = external capacitor in pF;
K = constant = 0.45 for VCC = 5.0 V and 0.48 for VCC = 2.0 V.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is approximately 7 pF.
[2] The time to retrigger the monostable multivibrator depends on the values of REXT and CEXT. The output pulse width will only beextended when the time between the active-going edges of the trigger input pulses meets the minimum retrigger time. If CEXT >10 pF,the next formula (at VCC = 5.0 V) for the set-up time of a retrigger pulse is valid:
trt = 30 + 0.19 × REXT × CEXT0.9 + 13 × REXT
1.05, where:
trt = typical retrigger time in ns;
CEXT = external capacitor in pF;
REXT = external resistor in kΩ.
The inherent test jig and pin capacitance at pins 15 and 7 (nREXT/CEXT) is 7 pF.
[3] When the device is powered-up, initiate the device via a reset pulse, when CEXT < 50 pF.
[4] CPD is used to determine the dynamic power dissipation (PD in µW):
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
13.2 Power-up considerationsWhen the monostable is powered-up it may produce an output pulse, with a pulse widthdefined by the values of REXT and CEXT. This output pulse can be eliminated using thecircuit shown in Figure 13.
13.3 Power-down considerationsA large capacitor CEXT may cause problems when powering-down the monostable due tothe energy stored in this capacitor. When a system containing this device ispowered-down or a rapid decrease of VCC to zero occurs, the monostable may sustaindamage, due to the capacitor discharging through the input protection diodes. To avoidthis possibility, use a damping diode (DEXT) preferably a germanium or Schottky typediode able to withstand large current surges and connect as shown in Figure 14.
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
15. Revision history
Table 11: Revision history
Document ID Release date Data sheet status Change notice Order number Supersedes
74HC_HCT123_3 20040511 Product data - 9397 750 13024 74HC_HCT123_2
Modifications: • The format of this data sheet has been redesigned to comply with the current presentation andinformation standard of Philips Semiconductors.
• Section 2 on page 1: ESD clause added
• Section 8 on page 6, Section 9 on page 7, and Section 10 on page 7: These sections replacereferences to family specifications
• Table note 1 on page 13: Changed ‘K’ factor from 0.55 to 0.45
• Table note 1 on page 15: Changed ‘K’ factor from 0.55 to 0.45
Philips Semiconductors 74HC123; 74HCT123Dual retriggerable monostable multivibrator with reset
16. Data sheet status
[1] Please consult the most recently issued data sheet before initiating or completing a design.
[2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet atURL http://www.semiconductors.philips.com.
[3] For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.
17. Definitions
Short-form specification — The data in a short-form specification isextracted from a full data sheet with the same type number and title. Fordetailed information see the relevant data sheet or data handbook.
Limiting values definition — Limiting values given are in accordance withthe Absolute Maximum Rating System (IEC 60134). Stress above one ormore of the limiting values may cause permanent damage to the device.These are stress ratings only and operation of the device at these or at anyother conditions above those given in the Characteristics sections of thespecification is not implied. Exposure to limiting values for extended periodsmay affect device reliability.
Application information — Applications that are described herein for anyof these products are for illustrative purposes only. Philips Semiconductorsmake no representation or warranty that such applications will be suitable forthe specified use without further testing or modification.
18. Disclaimers
Life support — These products are not designed for use in life supportappliances, devices, or systems where malfunction of these products canreasonably be expected to result in personal injury. Philips Semiconductorscustomers using or selling these products for use in such applications do soat their own risk and agree to fully indemnify Philips Semiconductors for anydamages resulting from such application.
Right to make changes — Philips Semiconductors reserves the right tomake changes in the products - including circuits, standard cells, and/orsoftware - described or contained herein in order to improve design and/orperformance. When the product is in full production (status ‘Production’),relevant changes will be communicated via a Customer Product/ProcessChange Notification (CPCN). Philips Semiconductors assumes noresponsibility or liability for the use of any of these products, conveys nolicense or title under any patent, copyright, or mask work right to theseproducts, and makes no representations or warranties that these products arefree from patent, copyright, or mask work right infringement, unless otherwisespecified.
19. Contact information
For additional information, please visit: http://www.semiconductors.philips.com
Level Data sheet status [1] Product status [2] [3] Definition
I Objective data Development This data sheet contains data from the objective specification for product development. PhilipsSemiconductors reserves the right to change the specification in any manner without notice.
II Preliminary data Qualification This data sheet contains data from the preliminary specification. Supplementary data will be publishedat a later date. Philips Semiconductors reserves the right to change the specification without notice, inorder to improve the design and supply the best possible product.
III Product data Production This data sheet contains data from the product specification. Philips Semiconductors reserves theright to make changes at any time in order to improve the design, manufacturing and supply. Relevantchanges will be communicated via a Customer Product/Process Change Notification (CPCN).