SCHA005B January   2015  – December 2022 74AC11074 , 74AC16373 , 74AC16374 , 74ACT11074 , 74ACT11373 , 74ACT11374 , 74ACT16373 , 74ACT16374 , 74ACT16823 , 74ACT16841 , CD4006B-MIL , CD4013B , CD4013B-MIL , CD4014B , CD4014B-MIL , CD4015B , CD4015B-MIL , CD40174B , CD40174B-MIL , CD40175B , CD40175B-MIL , CD40194B , CD4021B , CD4021B-MIL , CD4021B-Q1 , CD4027B , CD4027B-MIL , CD4031B , CD4031B-MIL , CD4034B , CD4034B-MIL , CD4035B , CD4035B-MIL , CD4042B , CD4042B-MIL , CD4043B , CD4043B-MIL , CD4044B , CD4044B-MIL , CD4076B , CD4076B-MIL , CD4094B , CD4094B-MIL , CD4099B , CD4099B-MIL , CD4508B , CD4508B-MIL , CD4517B , CD4517B-MIL , CD4724B , CD4724B-MIL , CD54AC109 , CD54AC112 , CD54AC164 , CD54AC273 , CD54AC299 , CD54AC373 , CD54AC374 , CD54AC573 , CD54AC574 , CD54AC74 , CD54ACT109 , CD54ACT112 , CD54ACT164 , CD54ACT174 , CD54ACT273 , CD54ACT299 , CD54ACT373 , CD54ACT374 , CD54ACT573 , CD54ACT574 , CD54ACT74 , CD54HC107 , CD54HC109 , CD54HC112 , CD54HC164 , CD54HC165 , CD54HC166 , CD54HC173 , CD54HC174 , CD54HC175 , CD54HC194 , CD54HC259 , CD54HC273 , CD54HC299 , CD54HC373 , CD54HC374 , CD54HC377 , CD54HC4015 , CD54HC4094 , CD54HC533 , CD54HC534 , CD54HC563 , CD54HC564 , CD54HC573 , CD54HC574 , CD54HC597 , CD54HC73 , CD54HC74 , CD54HC75 , CD54HCT109 , CD54HCT112 , CD54HCT164 , CD54HCT165 , CD54HCT166 , CD54HCT173 , CD54HCT174 , CD54HCT175 , CD54HCT259 , CD54HCT273 , CD54HCT299 , CD54HCT373 , CD54HCT374 , CD54HCT377 , CD54HCT533 , CD54HCT534 , CD54HCT564 , CD54HCT573 , CD54HCT574 , CD54HCT74 , CD54HCT75 , CD74AC109 , CD74AC112 , CD74AC164 , CD74AC174 , CD74AC175 , CD74AC273 , CD74AC299 , CD74AC323 , CD74AC373 , CD74AC374 , CD74AC534 , CD74AC573 , CD74AC574 , CD74AC74 , CD74ACT109 , CD74ACT112 , CD74ACT164 , CD74ACT174 , CD74ACT175 , CD74ACT273 , CD74ACT299 , CD74ACT373 , CD74ACT374 , CD74ACT573 , CD74ACT574 , CD74ACT74 , CD74ACT74-Q1 , CD74FCT273 , CD74FCT374 , CD74FCT843A , CD74HC107 , CD74HC109 , CD74HC112 , CD74HC164 , CD74HC165 , CD74HC166 , CD74HC173 , CD74HC174 , CD74HC175 , CD74HC194 , CD74HC195 , CD74HC259 , CD74HC273 , CD74HC299 , CD74HC373 , CD74HC374 , CD74HC377 , CD74HC4015 , CD74HC4094 , CD74HC533 , CD74HC534 , CD74HC563 , CD74HC564 , CD74HC573 , CD74HC574 , CD74HC595 , CD74HC597 , CD74HC670 , CD74HC73 , CD74HC74 , CD74HC75 , CD74HCT107 , CD74HCT109 , CD74HCT112 , CD74HCT164 , CD74HCT165 , CD74HCT166 , CD74HCT173 , CD74HCT174 , CD74HCT175 , CD74HCT194 , CD74HCT259 , CD74HCT273 , CD74HCT299 , CD74HCT373 , CD74HCT374 , CD74HCT377 , CD74HCT4094 , CD74HCT533 , CD74HCT534 , CD74HCT563 , CD74HCT564 , CD74HCT573 , CD74HCT574 , CD74HCT574-EP , CD74HCT574-Q1 , CD74HCT597 , CD74HCT670 , CD74HCT73 , CD74HCT74 , CD74HCT75 , CY54FCT273T , CY54FCT373T , CY54FCT374T , CY54FCT377T , CY54FCT573T , CY54FCT574T , CY54FCT841T , CY74FCT2373T , CY74FCT2573T , CY74FCT2574T , CY74FCT273T , CY74FCT373T , CY74FCT374T , CY74FCT573T , CY74FCT574T , SN54107 , SN54166 , SN54173 , SN5472 , SN5476 , SN54ABT16373A , SN54ABT16374A , SN54ABT273 , SN54ABT373 , SN54ABT374 , SN54ABT377 , SN54ABT533 , SN54ABT534 , SN54ABT573 , SN54ABT574 , SN54ABT821 , SN54ABT823 , SN54ABT841 , SN54ABT843 , SN54AC373 , SN54AC373-SP , SN54AC374 , SN54AC574 , SN54AC74 , SN54AC74-SP , SN54ACT16373 , SN54ACT373 , SN54ACT373-SP , SN54ACT374 , SN54ACT374-SP , SN54ACT573 , SN54ACT74 , SN54AHC273 , SN54AHC373 , SN54AHC374 , SN54AHC573 , SN54AHC574 , SN54AHC74 , SN54AHCT373 , SN54AHCT374 , SN54AHCT573 , SN54AHCT574 , SN54AHCT74 , SN54ALS109A , SN54ALS112A , SN54ALS174 , SN54ALS175 , SN54ALS259 , SN54ALS273 , SN54ALS29821 , SN54ALS299 , SN54ALS323 , SN54ALS373A , SN54ALS374A , SN54ALS563B , SN54ALS564B , SN54ALS573C , SN54ALS574B , SN54ALS576B , SN54ALS580B , SN54ALS74A , SN54ALS873B , SN54ALS874B , SN54ALS996 , SN54AS174 , SN54AS175B , SN54AS374 , SN54AS573A , SN54AS574 , SN54AS74A , SN54AS821A , SN54AS823A , SN54AS825A , SN54BCT373 , SN54BCT374 , SN54BCT574 , SN54BCT8374A , SN54F109 , SN54F373 , SN54F374 , SN54F74 , SN54HC109 , SN54HC109-SP , SN54HC112 , SN54HC164 , SN54HC164-SP , SN54HC165 , SN54HC166 , SN54HC166-SP , SN54HC174 , SN54HC175 , SN54HC195 , SN54HC259 , SN54HC273 , SN54HC273-DIE , SN54HC273-SP , SN54HC373 , SN54HC373-DIE , SN54HC373-SP , SN54HC374 , SN54HC374-SP , SN54HC377 , SN54HC573A , SN54HC573A-SP , SN54HC574 , SN54HC595 , SN54HC595-SP , SN54HC74 , SN54HC74-SP , SN54HCT373 , SN54HCT373-SP , SN54HCT374 , SN54HCT74 , SN54LS109A , SN54LS112A , SN54LS164 , SN54LS164-SP , SN54LS165A , SN54LS165A-SP , SN54LS166A , SN54LS173A , SN54LS174 , SN54LS175 , SN54LS194A , SN54LS195A , SN54LS273 , SN54LS273-SP , SN54LS279A , SN54LS299 , SN54LS323 , SN54LS373 , SN54LS373-SP , SN54LS374 , SN54LS375 , SN54LS377 , SN54LS378 , SN54LS379 , SN54LS595 , SN54LS597 , SN54LS670 , SN54LS673 , SN54LS674 , SN54LS73A , SN54LS74A , SN54LS74A-SP , SN54LS75 , SN54LS76A , SN54LS91 , SN54LVC373A , SN54LVC374A , SN54LVC573A , SN54LVC574A , SN54LVC74A , SN54LVC74A-SP , SN54LVTH162373-SP , SN54LVTH162374-SP , SN54LVTH16373 , SN54LVTH373 , SN54LVTH374 , SN54LVTH573 , SN54LVTH574 , SN54LVTH574-SP , SN54S112 , SN54S174 , SN54S175 , SN54S194 , SN54S373 , SN54S374 , SN54S74 , SN74ABT162823A , SN74ABT162841 , SN74ABT16373A , SN74ABT16373A-EP , SN74ABT16374A , SN74ABT16821 , SN74ABT16823 , SN74ABT16841 , SN74ABT16843 , SN74ABT273 , SN74ABT373 , SN74ABT374A , SN74ABT377A , SN74ABT533A , SN74ABT534A , SN74ABT573A , SN74ABT574A , SN74ABT821A , SN74ABT823 , SN74ABT841A , SN74ABT843 , SN74ABTH162260 , SN74ABTH16260 , SN74ABTH16823 , SN74AC373 , SN74AC373-EP , SN74AC374 , SN74AC533 , SN74AC534 , SN74AC563 , SN74AC564 , SN74AC573 , SN74AC574 , SN74AC74 , SN74AC74-EP , SN74ACT16373-EP , SN74ACT16374-EP , SN74ACT373 , SN74ACT373-EP , SN74ACT374 , SN74ACT533 , SN74ACT534 , SN74ACT563 , SN74ACT564 , SN74ACT573 , SN74ACT574 , SN74ACT74 , SN74ACT74-EP , SN74AHC16373 , SN74AHC16374 , SN74AHC174 , SN74AHC273 , SN74AHC373 , SN74AHC374 , SN74AHC573 , SN74AHC574 , SN74AHC594 , SN74AHC595 , SN74AHC595-Q1 , SN74AHC74 , SN74AHC74-EP , SN74AHC74Q-Q1 , SN74AHCT16373 , SN74AHCT16374 , SN74AHCT174 , SN74AHCT273 , SN74AHCT373 , SN74AHCT374 , SN74AHCT573 , SN74AHCT574 , SN74AHCT594 , SN74AHCT595 , SN74AHCT74 , SN74AHCT74-EP , SN74AHCT74Q-Q1 , SN74ALS109A , SN74ALS112A , SN74ALS164A , SN74ALS165 , SN74ALS166 , SN74ALS174 , SN74ALS175 , SN74ALS259 , SN74ALS273 , SN74ALS29821 , SN74ALS299 , SN74ALS323 , SN74ALS373A , SN74ALS374A , SN74ALS533A , SN74ALS534A , SN74ALS563B , SN74ALS564B , SN74ALS573C , SN74ALS574B , SN74ALS575A , SN74ALS576B , SN74ALS577A , SN74ALS580B , SN74ALS666 , SN74ALS667 , SN74ALS74A , SN74ALS841 , SN74ALS843 , SN74ALS873B , SN74ALS874B , SN74ALS990 , SN74ALS992 , SN74ALS996 , SN74ALVCH162260 , SN74ALVCH162373 , SN74ALVCH162374 , SN74ALVCH16260 , SN74ALVCH162721 , SN74ALVCH162841 , SN74ALVCH16373 , SN74ALVCH16374 , SN74ALVCH16721 , SN74ALVCH16820 , SN74ALVCH16821 , SN74ALVCH16823 , SN74ALVCH16841 , SN74ALVCH373 , SN74ALVCH374 , SN74AS109A , SN74AS174 , SN74AS175B , SN74AS194 , SN74AS373 , SN74AS374 , SN74AS573A , SN74AS574 , SN74AS576 , SN74AS74A , SN74AS874 , SN74AUC16373 , SN74AUC16374 , SN74AUC1G74 , SN74AUC1G79 , SN74AUC1G80 , SN74AUC2G79 , SN74AUC2G80 , SN74AUC74 , SN74AUCH16374 , SN74AUP1G74 , SN74AUP1G79 , SN74AUP1G80 , SN74AUP2G79 , SN74AUP2G80 , SN74AVC16373 , SN74AVC16374 , SN74AVC16722 , SN74BCT374 , SN74BCT573 , SN74BCT574 , SN74F109 , SN74F112 , SN74F174A , SN74F175 , SN74F299 , SN74F373 , SN74F374 , SN74F377A , SN74F573 , SN74F574 , SN74F74 , SN74HC109 , SN74HC112 , SN74HC164 , SN74HC165 , SN74HC165-EP , SN74HC165-Q1 , SN74HC166 , SN74HC166A-EP , SN74HC166A-Q1 , SN74HC174 , SN74HC175 , SN74HC259 , SN74HC273 , SN74HC273-Q1 , SN74HC373 , SN74HC374 , SN74HC377 , SN74HC563 , SN74HC573A , SN74HC573A-Q1 , SN74HC574 , SN74HC594 , SN74HC595 , SN74HC595-EP , SN74HC74 , SN74HC74-EP , SN74HC74-Q1 , SN74HCT273 , SN74HCT373 , SN74HCT374 , SN74HCT377 , SN74HCT573 , SN74HCT574 , SN74HCT74 , SN74LS107A , SN74LS109A , SN74LS112A , SN74LS164 , SN74LS165A , SN74LS166A , SN74LS173A , SN74LS174 , SN74LS175 , SN74LS194A , SN74LS259B , SN74LS273 , SN74LS279A , SN74LS299 , SN74LS373 , SN74LS374 , SN74LS375 , SN74LS377 , SN74LS378 , SN74LS594 , SN74LS595 , SN74LS597 , SN74LS598 , SN74LS670 , SN74LS673 , SN74LS674 , SN74LS73A , SN74LS74A , SN74LS75 , SN74LV164A , SN74LV165A , SN74LV165A-EP , SN74LV165A-Q1 , SN74LV166A , SN74LV174A , SN74LV175A , SN74LV273A , SN74LV373A , SN74LV373A-Q1 , SN74LV373AT , SN74LV374A , SN74LV374A-EP , SN74LV374A-Q1 , SN74LV374AT , SN74LV573A , SN74LV573AT , SN74LV574A , SN74LV594A , SN74LV595A , SN74LV595A-EP , SN74LV595A-Q1 , SN74LV74A , SN74LV74A-EP , SN74LV74A-Q1 , SN74LV8153 , SN74LV8153-Q1 , SN74LVC112A , SN74LVC16373 , SN74LVC16373A , SN74LVC16373A-EP , SN74LVC16374 , SN74LVC16374A , SN74LVC1G175 , SN74LVC1G175-EP , SN74LVC1G373 , SN74LVC1G374 , SN74LVC1G374-Q1 , SN74LVC1G74 , SN74LVC1G79 , SN74LVC1G79-EP , SN74LVC1G80 , SN74LVC2G74 , SN74LVC2G74-EP , SN74LVC2G74-Q1 , SN74LVC2G79 , SN74LVC2G80 , SN74LVC373A , SN74LVC373A-EP , SN74LVC374A , SN74LVC374A-EP , SN74LVC374A-Q1 , SN74LVC573A , SN74LVC573A-EP , SN74LVC573A-Q1 , SN74LVC574A , SN74LVC574A-EP , SN74LVC574A-Q1 , SN74LVC74A , SN74LVC74A-EP , SN74LVC74A-Q1 , SN74LVC821A , SN74LVC823A , SN74LVC841A , SN74LVCH16373A , SN74LVCH16374A , SN74LVCH32373A , SN74LVTH162373 , SN74LVTH162373-EP , SN74LVTH162374 , SN74LVTH16373 , SN74LVTH16373-EP , SN74LVTH16374 , SN74LVTH16374-EP , SN74LVTH273 , SN74LVTH273-EP , SN74LVTH373 , SN74LVTH373-EP , SN74LVTH374 , SN74LVTH374-EP , SN74LVTH573 , SN74LVTH573-EP , SN74LVTH574 , SN74LVTH574-EP , SN74S112A , SN74S175 , SN74S374 , SN74S74

PRODMIX  

  1.   Power-Up Behavior of Clocked Devices
  2. 1Unknown States at Power-Up
  3. 2Solutions to Unknown States at Power-Up
    1. 2.1 Use a Device with Clear or Preset Pins
    2. 2.2 Delay the Clock Edge with an RC Circuit and Schmitt Trigger Buffer
    3. 2.3 Wait Until VCC Has Ramped
  4. 3Trademarks
  5. 4Revision History

1 Unknown States at Power-Up

The CD74HC4094 is an example of a device that does not have guaranteed output levels upon power-up. Before a valid clock edge, thresholds within the device can cause the internal logic chains to product high or low signals. This effect can vary with voltage, temperature, manufacturing lot, and more. As a result, the outputs Qn will be determined by unpredictable power-up states determined by these internal thresholds and should not be considered valid logic signals. However, once a valid clock edge has occurred, the outputs behave normally according to the truth table in the datasheet. For this particular device, 8 clock edges are required to shift the unknown data out of the device and ensure that all Qn outputs are valid.

Another important consideration is the rise of the CLK signal simultaneously with VCC. Although the clock signal will be seen as an appropriate edge on an oscilloscope, the device may not consider it a valid clock. As VCC rises, the VIH threshold of the clock signal also rises. If the two rise simultaneously, the clock signal may or may not cross the appropriate thresholds required to be considered valid. Capacitance within the circuit will also cause subtle and unpredictable differences in the timing of CLK and VCC. Therefore, it is not recommended to produce a clock edge until VCC has risen to a recommended level as specified in the device datasheet.