SN54HC161, SN74HC161 4-BIT SYNCHRONOUS BINARY COUNTERS

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Rolf French
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1 Internal Look-head for Fast ounting arry Output for n-it ascading Synchronous ounting Synchronously Programmable Package Options Include Plastic Small-Outline () and eramic Flat (W) Packages, eramic hip arriers (FK), and Standard Plastic (N) and eramic (J) 300-mil IPs description SN54H161...J OR W PKGE SN74H OR N PKGE (TOP VIEW) GN V RO Q Q Q Q LO These synchronous, presettable counters feature an internal carry look-ahead for application in high-speed counting designs. The H161 are 4-bit binary counters. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the count-enable (, ) inputs and internal gating. This mode of operation eliminates the output counting spikes that are normally associated with synchronous (ripple-clock) counters. buffered clock () input triggers the four flip-flops on the rising (positive-going) edge of the clock waveform. These counters are fully programmable; that is, they can be preset to any number between 0 and 9 or 15. s presetting is synchronous, setting up a low level at the load input disables the counter and causes the outputs to agree with the setup data after the next clock pulse, regardless of the levels of the enable inputs. SN54H FK PKGE (TOP VIEW) The clear function for the H161 is asynchronous. low level at the clear () input sets all four of the flip-flop outputs low, regardless of the levels of the, load (LO), or enable inputs. The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without additional gating. Instrumental in accomplishing this function are,, and a ripple-carry output (RO). oth and must be high to count, and is fed forward to enable RO. Enabling RO produces a high-level pulse while the count is maximum (9 or 15 with Q high). This high-level overflow ripple-carry pulse can be used to enable successive cascaded stages. Transitions at or are allowed, regardless of the level of. These counters feature a fully independent clock circuit. hanges at control inputs (,, or LO) 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 SN54H161 is characterized for operation over the full military temperature range of 55 to 125. The SN74H161 is characterized for operation from 40 to 85. N N GN N LO RO V N No internal connection Q Q N Q Q Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PROUTION T information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. opyright 1997, Texas Instruments Incorporated POST OFFIE OX LLS, TEXS

2 logic symbol LO TRIV16 T=0 M2 G3 5/2,3,4+ 3T=15 15 RO ,5 [1] [2] [4] [8] Q Q Q Q This symbol is in accordance with NSI/IEEE Std and IE Publication Pin numbers shown are for the, J, N, and W packages. 2 POST OFFIE OX LLS, TEXS 75265

3 logic diagram (positive logic) LO L K 15 RO 2 1 R K L G2 3 1, 2T/13 3 4R 14 Q G2 4 1, 2T/13 3 4R 13 Q G2 5 1, 2T/13 3 4R 12 Q G2 6 1, 2T/13 3 4R 11 Q For simplicity, routing of complementary signals L and K is not shown on this overall logic diagram. The uses of these signals are shown on the logic diagram of the /T flip-flops. Pin numbers shown are for the, J, N, and W packages. POST OFFIE OX LLS, TEXS

4 logic symbol, each /T flip-flop L (Load) TE (Toggle Enable) G2 K (lock) (Inverted ata) R (Inverted Reset) 1, 2T/13 3 4R Q (Output) logic diagram, each /T flip-flop (positive logic) K L TE L TG L TG TG TG Q K TG K TG K K R The origins of L and K are shown in the logic diagram of the overall device. 4 POST OFFIE OX LLS, TEXS 75265

5 typical clear, preset, count, and inhibit sequence The following sequence is illustrated below: 1. lear outputs to zero (asynchronous) 2. Preset to binary ount to 13, 14, 15, 0, 1, and 2 4. Inhibit LO ata Inputs Q ata Outputs Q Q Q RO sync lear Sync lear Preset ount Inhibit POST OFFIE OX LLS, TEXS

6 absolute maximum ratings over operating free-air temperature range Supply voltage range, V V to 7 V Input clamp current, I IK (V I < 0 or V I > V ) (see Note 1) ±20 m Output clamp current, I OK (V O < 0 or V O > V ) (see Note 1) ±20 m ontinuous output current, I O (V O = 0 to V ) ±25 m ontinuous current through V or GN ±50 m Package thermal impedance, θ J (see Note 2): package /W N package /W Storage temperature range, T stg to 150 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. NOTES: 1. The input and output voltage ratings may be exceeded if the input and output current ratings are observed. 2. The package thermal impedance is calculated in accordance with JES 51, except for through-hole packages, which use a trace length of zero. recommended operating conditions SN54H161 SN74H161 UNIT MIN NOM MX MIN NOM MX Supply voltage V = 2 V VIH High-level input voltage = 4.5 V V = 6 V = 2 V VIL Low-level input voltage = 4.5 V V = 6 V VI Input voltage 0 0 V VO Output voltage 0 0 V = 2 V tt Input transition (rise and fall) time = 4.5 V ns = 6 V T Operating free-air temperature If this device is used in the threshold region (from VILmax = 0.5 V to VIHmin = 1.5 V), there is a potential to go into the wrong state from induced grounding, causing double clocking. Operating with the inputs at tt = 1000 ns and = 2 V does not damage the device; however, functionally, the inputs are not ensured while in the shift, count, or toggle operating modes. 6 POST OFFIE OX LLS, TEXS 75265

7 electrical characteristics over recommended operating free-air temperature range (unless otherwise noted) PRMETER TEST ONITIONS T = 25 SN54H161 SN74H161 MIN TYP MX MIN MX MIN MX 2 V IOH = 20 µ 4.5 V VOH VI = VIH or VIL 6 V V IOH = 4 m 4.5 V IOH = 5.2 m 6 V V IOL = 20 µ 4.5 V VOL VI = VIH or VIL 6 V V IOL = 4 m 4.5 V IOL = 5.2 m 6 V II VI = or 0 6 V ±0.1 ±100 ±1000 ±1000 n I VI = or 0, IO = 0 6 V µ i 2 V to 6 V pf UNIT timing requirements over recommended operating free-air temperature range (unless otherwise noted) T = 25 SN54H161 SN74H161 MIN MX MIN MX MIN MX 2 V fclock lock frequency 4.5 V MHz tw tsu Pulse duration Setup time before 6 V V high or low 4.5 V V V low 4.5 V V V ,,, or 4.5 V V V LO low 4.5 V V V , 4.5 V V V inactive 4.5 V V V th Hold time, all synchronous inputs after 4.5 V ns 6 V UNIT ns ns POST OFFIE OX LLS, TEXS

8 switching characteristics over recommended operating free-air temperature range, L = 50 pf (unless otherwise noted) (see Figure 1) PRMETER FROM (INPUT) TO (OUTPUT) T = 25 SN54H161 SN74H161 MIN TYP MX MIN MX MIN MX 2 V fmax 4.5 V MHz 6 V V RO 4.5 V V V tpd ny Q 4.5 V ns tphl 6 V V RO 4.5 V V V ny Q 4.5 V V V RO 4.5 V V V tt ny 4.5 V ns 6 V UNIT ns operating characteristics, T = 25 PRMETER TEST ONITIONS TYP UNIT pd Power dissipation capacitance No load 60 pf 8 POST OFFIE OX LLS, TEXS 75265

9 PRMETER MESUREM INFORMTION From Output Under Test Test Point L = 50 pf (see Note ) High-Level Pulse Low-Level Pulse tw 0 V 0 V LO IRUIT VOLTGE WVEFORMS PULSE URTIONS Input 0 V tplh tphl Reference Input ata Input 10% tsu th 90% 90% tr 0 V 10% 0 V tf In-Phase Output Out-of-Phase Output 10% tphl 90% 90% 90% tr 10% 10% tf tplh VOH 10% VOL tf VOH 90% VOL tr VOLTGE WVEFORMS SETUP N HOL N INPUT RISE N FLL TIMES VOLTGE WVEFORMS PROPGTION ELY N OUTPUT TRNSITION TIMES NOTES:. L includes probe and test-fixture capacitance.. Phase relationships between waveforms were chosen arbitrarily. ll input pulses are supplied by generators having the following characteristics: PRR 1 MHz, ZO = 50 Ω, tr = 6 ns, tf = 6 ns.. For clock inputs, fmax is measured when the input duty cycle is.. The outputs are measured one at a time with one input transition per measurement. E. tplh and tphl are the same as tpd. Figure 1. Load ircuit and Voltage Waveforms POST OFFIE OX LLS, TEXS

10 n-bit synchronous counters PPLITION INFORMTION This application demonstrates how the look-ahead carry circuit can be used to implement a high-speed n-bit counter. The H161 count in binary. Virtually any count mode (modulo-n, N 1 -to-n 2, N 1 -to-maximum) can be used with this fast look-ahead circuit. The application circuit shown in Figure 2 is not valid for clock frequencies above 18 MHz (at 25 and 4.5-V V ). The reason for this is that there is a glitch that is produced on the second stage s RO and every succeeding stage s RO. This glitch is common to all H vendors that Texas Instruments has evaluated, in addition to the bipolar equivalents (LS, LS, S). 10 POST OFFIE OX LLS, TEXS 75265

11 lear (L) ount (H)/ isable (L) LO LS TR T=0 3T=MX G3 5/2,3,4+ RO Load (L) ount (H)/ isable (L) lock 1,5 [1] [2] [3] [4] Q Q Q Q LO TR T=0 3T=MX G3 5/2,3,4+ RO 1,5 [1] [2] [3] [4] Q Q Q Q LO TR T=0 3T=MX G3 5/2,3,4+ RO 1,5 [1] [2] [3] [4] Q Q Q Q LO TR T=0 3T=MX G3 5/2,3,4+ RO 1,5 [1] [2] [3] [4] Q Q Q Q To More Significant Stages Figure 2 POST OFFIE OX LLS, TEXS

12 The glitch on RO is caused because the propagation delay of the rising edge of Q of the second stage is shorter than the propagation delay of the falling edge of. RO is the product of, Q, Q, Q, and Q ( Q Q Q Q ). The resulting glitch is about 7 12 ns in duration. Figure 3 shows the condition in which the glitch occurs. For simplicity, only two stages are being considered, but the results can be applied to other stages. Q, Q, and Q of the first and second stage are at logic one, and Q of both stages are at logic zero ( ) after the first clock pulse. On the rising edge of the second clock pulse, Q and RO of the first stage go high. On the rising edge of the third clock pulse, Q and RO of the first stage return to a low level, and Q of the second stage goes to a high level. t this time, the glitch on RO of the second stage appears because of the race condition inside the chip Q1, Q1, Q1 Q1 RO1, 2 Q2, Q2, Q2 Q2 RO2 Glitch (7 12 ns) Figure 3 The glitch causes a problem in the next stage (stage three) if the glitch is still present when the next rising clock edge appears (clock pulse 4). To ensure that this does not happen, the clock frequency must be less than the inverse of the sum of the clock-to-ro propagation delay and the glitch duration (t g ). In other words, f max = 1/(t pd -to-ro + t g ). For example, at 25 at 4.5-V V, the clock-to-ro propagation delay is 43 ns and the maximum duration of the glitch is 12 ns. Therefore, the maximum clock frequency that the cascaded counters can use is 18 MHz. The following tables contain the f clock, t w, and f max specifications for applications that use more than two H161 devices cascaded together. 12 POST OFFIE OX LLS, TEXS 75265

13 timing requirements over recommended operating free-air temperature range (unless otherwise noted) T = 25 SN54H161 SN74H161 MIN MX MIN MX MIN MX 2 V fclock lock frequency 4.5 V MHz 6 V V tw Pulse duration, high or low 4.5 V ns 6 V UNIT switching characteristics over recommended operating free-air temperature range, L = 50 pf (unless otherwise noted) (see Note 3) PRMETER NOTE 3: FROM (INPUT) TO (OUTPUT) T = 25 SN54H161 SN74H161 MIN MX MIN MX MIN MX 2 V fmax 4.5 V MHz 6 V These limits apply only to applications that use more than two H161 devices cascaded together. If the H161 are used as a single unit, or only two cascaded together, then the maximum clock frequency that the device can use is not limited because of the glitch. In these situations, the device can be operated at the maximum specifications. glitch can appear on RO of a single H161 device, depending on the relationship of to. ny application that uses RO to drive any input except an of another cascaded H161 must take this into consideration. UNIT POST OFFIE OX LLS, TEXS

14 IMPORTNT NOTIE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. ll products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. ERTIN PPLITIONS USING SEMIONUTOR PROUTS MY INVOLVE POTIL RISKS OF ETH, PERSONL INJURY, OR SEVERE PROPERTY OR ENVIRONML MGE ( RITIL PPLITIONS ). TI SEMIONUTOR PROUTS RE NOT ESIGNE, UTHORIZE, OR WRRNTE TO E SUITLE FOR USE IN LIFE-SUPPORT EVIES OR SYSTEMS OR OTHER RITIL PPLITIONS. INLUSION OF TI PROUTS IN SUH PPLITIONS IS UNERSTOO TO E FULLY T THE USTOMER S RISK. In order to minimize risks associated with the customer s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI s publication of information regarding any third party s products or services does not constitute TI s approval, warranty or endorsement thereof. opyright 1998, Texas Instruments Incorporated

SN54HC191, SN74HC191 4-BIT SYNCHRONOUS UP/DOWN BINARY COUNTERS

SN54HC191, SN74HC191 4-BIT SYNCHRONOUS UP/DOWN BINARY COUNTERS Single Down/Up Count-Control Line Look-Ahead Circuitry Enhances Speed of Cascaded Counters Fully Synchronous in Count Modes Asynchronously Presettable With Load Control Package Options Include Plastic