Presettable synchronous 4-bit binary up/down counter

The 74HC191 is an asynchronously presettable 4-bit binary up/down counter. It contains four master/slave flip-flops with internal gating and steering logic to provide asynchronous preset and synchronous count-up and count-down operation. Asynchronous parallel load capability permits the counter to be preset to any desired value. Information present on the parallel data inputs (D0 to D3) is loaded into the counter and appears on the outputs when the parallel load (PL) input is LOW. This operation overrides the counting function. Counting is inhibited by a HIGH level on the count enable (CE) input. When CE is LOW internal state changes are initiated synchronously by the LOW-to-HIGH transition of the clock input. The up/down (U/D) input signal determines the direction of counting as indicated in the function table. The CE input may go LOW when the clock is in either state, however, the LOW-to-HIGH CE transition must occur only when the clock is HIGH. Also, the U/D input should be changed only when either CE or CP is HIGH. Overflow/underflow indications are provided by two types of outputs, the terminal count (TC) and ripple clock (RC). The TC output is normally LOW and goes HIGH when a circuit reaches zero in the count-down mode or reaches '15' in the count-up-mode. The TC output will remain HIGH until a state change occurs, either by counting or presetting, or until U/D is changed. Do not use the TC output as a clock signal because it is subject to decoding spikes. The TC signal is used internally to enable the RC output. When TC is HIGH and CE is LOW, the RC output follows the clock pulse (CP). This feature simplifies the design of multistage counters as shown in Figure 1 and Figure 2. In Figure 1, each RC output is used as the clock input to the next higher stage. It is only necessary to inhibit the first stage to prevent counting in all stages, since a HIGH on CE inhibits the RC output pulse. The timing skew between state changes in the first and last stages is represented by the cumulative delay of the clock as it ripples through the preceding stages. This can be a disadvantage of this configuration in some applications. Figure 2 shows a method of causing state changes to occur simultaneously in all stages. The RC outputs propagate the carry/borrow signals in ripple fashion and all clock inputs are driven in parallel. In this configuration the duration of the clock LOW state must be long enough to allow the negative-going edge of the carry/borrow signal to ripple through to the last stage before the clock goes HIGH. Since the RC output of any package goes HIGH shortly after its CP input goes HIGH there is no such restriction on the HIGH-state duration of the clock. In Figure 3, the configuration shown avoids ripple delays and their associated restrictions. Combining the TC signals from all the preceding stages forms the CE input for a given stage. An enable must be included in each carry gate in order to inhibit counting. The TC output of a given stage it not affected by its own CE signal therefore the simple inhibit scheme of Figure 1 and Figure 2 does not apply. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

Features and benefits

  • Wide supply voltage range from 2.0 to 6.0 V

  • CMOS low power dissipation

  • High noise immunity

  • Latch-up performance exceeds 100 mA per JESD 78 Class II Level B

  • CMOS input levels

  • Synchronous reversible counting

  • Asynchronous parallel load

  • Count enable control for synchronous expansion

  • Single up/down control input

  • Complies with JEDEC standards:

    • JESD8C (2.7 V to 3.6 V)

    • JESD7A (2.0 V to 6.0 V)

  • ESD protection:

    • HBM JESD22-A114F exceeds 2000 V

    • MM JESD22-A115-A exceeds 200 V

  • Specified from -40 °C to +85 °C and -40 °C to +125 °C


Type number Product status VCC (V) Output drive capability (mA) Logic switching levels tpd (ns) Power dissipation considerations Tamb (°C) Rth(j-a) (K/W) Ψth(j-top) (K/W) Rth(j-c) (K/W) Package name
74HC191PW Production 2.0 - 6.0 ± 5.2 CMOS 22 low -40~125 102 1.0 28.6 TSSOP16


Type number Orderable part number, (Ordering code (12NC)) Status Marking Package Package information Reflow-/Wave soldering Packing
74HC191PW 74HC191PW,118
Active HC191 SOT403-1

Environmental information

Type number Orderable part number Chemical content RoHS RHF-indicator
74HC191PW 74HC191PW,118 74HC191PW rohs rhf rhf
Quality and reliability disclaimer

Documentation (14)

File name Title Type Date
74HC191 Presettable synchronous 4-bit binary up/down counter Data sheet 2021-09-08
AN11044 Pin FMEA 74HC/74HCT family Application note 2019-01-09
74HC191PW_Nexperia_Product_Reliability 74HC191PW Nexperia Product Reliability Quality document 2023-05-29
HCT_USER_GUIDE HC/T User Guide User manual 1997-10-31
SOT403-1 3D model for products with SOT403-1 package Design support 2020-01-22
Nexperia_package_poster Nexperia package poster Leaflet 2020-05-15
TSSOP16_SOT403-1_mk plastic, thin shrink small outline package; 16 leads; 0.65 mm pitch; 5 mm x 4.4 mm x 1.1 mm body Marcom graphics 2017-01-28
SOT403-1_118 TSSOP16; Reel pack for SMD, 13"; Q1/T1 product orientation Packing information 2020-04-21
SOT403-1_128 TSSOP16; Reel pack; SMD, 13", Turned Q4/T2 180 deg product orientation Orderable part number ending ,128 or HP Ordering code (12NC) ending 128 Packing information 2020-04-27
SOT403-1_623 TSSOP16; Reel pack; SMD, 13"; Q1 Standard product orientation; Orderable part number ending, 623 or HL; Ordering code (12NC) ending 623 Packing information 2020-04-27
SOT403-1_653 TSSOP16; Reel pack; SMD, 13"; Q1 Standard product orientation; Orderable part number ending, 653 or HL; Ordering code (12NC) ending 653 Packing information 2020-04-27
SSOP-TSSOP-VSO-WAVE Footprint for wave soldering Wave soldering 2009-10-08


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File name Title Type Date
SOT403-1 3D model for products with SOT403-1 package Design support 2020-01-22

Ordering, pricing & availability

Type number Orderable part number Ordering code (12NC) Status Packing Packing Quantity Buy online
74HC191PW 74HC191PW,118 935188370118 Active SOT403-1_118 2,500 Order product


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Orderable parts

Type number Orderable part number Ordering code (12NC) Package Buy from distributors
74HC191PW 74HC191PW,118 935188370118 SOT403-1 Order product