CD4045B CMOS 21-Stage Counter |

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CMOS 21-Stage Counter

CMOS 21-Stage Counter - CD4045B


CD4045B is a timing circuit consisting of 21 counter stages, two output-shaping flip-flops, two inverter output drivers, and input inverters for use in a crystal oscillator. The CD4045B configuration provides 21 flip-flop counting stages, and two flip-flops for shaping the output waveform for a 3.125% duty cycle. Push-pull operation is provided by the inverter output drivers.

The first inverter is intended for use as a crystal oscillator/amplifier. However, it may be used as a normal logic inverter if desired. A crystal oscillator circuit can be made less sensitive to voltage-supply variations by the user of source resistors. In this device, the sources of the p and n transistors have been brought out to package terminals. If external resistors are not required, the sources must be shorted to their respective substrates (Sp to VDD, Sn to VSS). See Fig. 1. The first inverter in conjunction with an outboard inverter, such as 1/6 CD4069, and RX, CX, and RS can also be used to construct an RC oscillator. The following data is supplied as a guide in the selection of values for RX, RS, and CX used in Fig. 11:

  1. RX max = 10 M and CX = 50 pF
  2. CX max = 25 µF with RS = 560 k

The CD4045B types are supplied in 16-lead dual-in-line plastic packages (E suffix), 16-lead small-outline package (NSR suffix), and 16-lead thin shrink small-outline packages (PW and PWR suffixes).


  • Very low operating dissipation . . . . . <1 mW (typ.) @ VDD = 5 V, f = 1 MHz
  • Output drivers with sink or source capability . . . . . 7 mA (typ.) @ VDD = 5 V
  • Medium speed (typ.) . . . f = 25 MHz @ VDD = 10 V
  • 100% tested for quiescent current at 20 V
  • 5-V, 10-V, and 15-V parametric ratings
  • Meets all requirements of JEDEC Tentative Standard No. 13B, "Standard Specifications for Description of 'B' Series CMOS Devices"
  • Applications
    • Digital equipment in which ultra-low dissipation and/or operation using a battery source is required.
    • Accurate timing from a crystal oscillator for timing applications such as wall clocks, table clocks, automobile clocks, and digital timing references in any circuit requiring accurately timed outputs at various intervals in the counting sequence.
    • Driving miniature synchronous motors, stepping motors, or external bipolar transistors in push-pull fashion.


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Part number Order Technology Family VCC (Min) (V) VCC (Max) (V) Bits (#) Voltage (Nom) (V) F @ nom voltage (Max) (MHz) ICC @ nom voltage (Max) (mA) tpd @ nom Voltage (Max) (ns) IOL (Max) (mA) IOH (Max) (mA) Function Type Rating Operating temperature range (C) Package Group
CD4045B Order now CD4000     3     18     2     5
8     0.03     2700     10.5     -10.5     Counter     Other     Catalog     -55 to 125     PDIP | 16