Features: · Internal Look-Ahead Circuitry for Fast Counting
· Carry Output for n-Bit Cascading
· Synchronous Counting
· Synchronously Programmable
· Package Options Include Plastic
Small-Outline (D) and Shrink Small-Outline
(DB) Packages, Ceramic Chip Carriers (FK),
Standard Plastic (N) and Ceramic (J) DIPsPinout
SpecificationsSupply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 V to 7 V
Input voltage range, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.5 V to 7 V
Package thermal impedance, qJA (see Note 1): D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73°C/W
DB package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82°C/W
N package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67°C/W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65°C to 150°C
† Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: The package thermal impedance is calculated in accordance with JESD 51.DescriptionThese synchronous, presettable, 4-bit decade and binary counters feature an internal carry look-ahead circuitry for application in high-speed counting designs. The SN54ALS162B is a 4-bit decade counter. The SN54ALS161B, SN54ALS162B, SN54ALS163B, SN54AS161, and SN54AS163 are 4-bit binary counters. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincidentally with each other when instructed by the count-enable (ENP, ENT) inputs and internal gating. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters. A buffered clock (CLK) input triggers the four flip-flops on the rising (positive-going) edge of the clock input waveform.
SN54ALS161B, SN54ALS162B, SN54ALS163B, SN54AS161, and SN54AS163 are fully programmable; they can be preset to any number between 0 and 9 or 15. Because presetting is synchronous, setting up a low level at the load (LOAD) input disables the counter and causes the outputs of SN54ALS161B, SN54ALS162B, SN54ALS163B, SN54AS161, and SN54AS163 to agree with the setup data after the next clock pulse, regardless of the levels of the enable inputs.
The clear function for the 'ALS161B and 'AS161 devices is asynchronous. A low level at the clear (CLR) input sets all four of the flip-flop outputs low, regardless of the levels of the CLK, LOAD, or enable inputs. The clear function for the SN54ALS162B, 'ALS163B, and 'AS163 devices is synchronous, and a low level at CLR sets all four of the flip-flop outputs low after the next clock pulse, regardless of the levels of the enable inputs. This synchronous clear allows the count length to be modified easily by decoding the Q outputs for the maximum count desired. The active-low output of the gate used for decoding is connected to CLR to synchronously clear the counter to 0000 (LLLL).
The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without additional gating. ENP and ENT inputs and a ripple-carry (RCO) output are instrumental in accomplishing this function. Both ENP and ENT must be high to count, and ENT is fed forward to enable RCO. RCO, thus enabled,produces a high-level pulse while the count is maximum (9 or 15, with QA high). The high-level overflow ripple-carry pulse can be used to enable successive cascaded stages. Transitions at ENP or ENT are allowed, regardless of the level of CLK.
These counters of SN54ALS161B, SN54ALS162B, SN54ALS163B, SN54AS161, and SN54AS163 feature a fully independent clock circuit. Changes at control inputs (ENP, ENT, or LOAD) that modify the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter (whether enabled, disabled, loading, or counting) is dictated solely by the conditions meeting the stable setup and hold times.
The c are characterized for operation over the full military temperature range of 55°C to 125°C. The SN74ALS161B, SN74ALS163B, SN74AS161, and SN74AS163 are characterized for operation from 0°C to 70°C.
SN54AS163 Data Sheet
