HD74HCT688 8-bit Magnitude Comparator Description The HD74HCT688 compares bit for bit two 8-bit words and indicate whether or not they are equal. The P=Q output indicates equality when it is low. A single active low enable is provided to facilitate cascading of several packages and enable comparison of words greater than 8 bits. This device is useful in memory block decoding applications, where memory block enable signals must be generated from computer address information. Features • • • • • • LSTTL Output Logic Level Compatibility as well as CMOS Output Compatibility High Speed Operation: tpd (Data to P=Q) = 18 ns typ (CL = 50 pF) High Output Current: Fanout of 10 LSTTL Loads Wide Operating Voltage: VCC = 4.5 to 5.5 V Low Input Current: 1 µA max Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C) Function Table Inputs Data P, Q Enable G P=Q P=Q L L P>Q L H P<Q L H X H H HD74HCT688 Pin Arrangement G 1 20 VCC P0 2 19 P=Q Q0 3 18 Q7 P1 4 17 P7 Q1 5 16 Q6 P2 6 15 P6 Q2 7 14 Q5 P3 8 13 P5 Q3 9 12 Q4 GND 10 11 P4 (Top view) 2 HD74HCT688 Block Diagram P0 Q0 P1 Q1 P2 Q2 P3 Q3 P4 P=Q Q4 P5 Q5 P6 Q6 P7 Q7 G 3 HD74HCT688 DC Characteristics Ta = –40 to +85°C Ta = 25°C Test Conditions Item Symbol Min Typ Max Min Max Unit VCC (V) Input voltage VIH 2.0 — — — V 4.5 to 5.5 VIL — — 0.8 — 0.8 V 4.5 to 5.5 VOH 4.4 — — 4.4 — V 4.5 Vin = VIH or VIL I OH = –20 µA 4.18 — — 4.13 — 4.5 I OH = –4 mA — — 0.1 — 0.1 — — 0.26 — 0.33 Iin — — ±0.1 — ±1.0 µA 5.5 Vin = VCC or GND Quiescent current I CC — — 4.0 — 40 µA 5.5 Vin = VCC or GND, Iout = 0 µA Output voltage VOL Input current 2.0 V 4.5 Vin = VIH or VIL I OL = 20 µA 4.5 I OL = 4 mA AC Characteristics (CL = 50 pF, Input tr = tf = 6 ns) Ta = –40 to +85°C Ta = 25°C Test Conditions Min Typ Max Min Max Unit VCC (V) Propagation delay t PLH — 17 42 — 53 ns 4.5 time t PHL — 19 42 — 53 t PLH — 9 24 — 30 t PHL — 12 24 — 30 Output rise/fall time t TLH t THL — 5 15 — 19 ns 4.5 Input capacitance Cin — 5 10 — 10 pF — Item 4 Symbol Por Q to output 4.5 ns 4.5 4.5 Enable to output Unit: mm 24.50 25.40 Max 6.30 11 1 7.00 Max 20 10 1.30 2.54 ± 0.25 0.48 ± 0.10 0.51 Min 1.27 Max 2.54 Min 5.08 Max 0.89 7.62 + 0.11 0.25 – 0.05 0° – 15° Hitachi Code JEDEC EIAJ Weight (reference value) DP-20N — Conforms 1.26 g Unit: mm 12.6 13 Max 11 1 10 1.27 *0.42 ± 0.08 0.40 ± 0.06 0.10 ± 0.10 0.80 Max *0.22 ± 0.05 0.20 ± 0.04 2.20 Max 5.5 20 0.20 7.80 +– 0.30 1.15 0° – 8° 0.70 ± 0.20 0.15 0.12 M *Dimension including the plating thickness Base material dimension Hitachi Code JEDEC EIAJ Weight (reference value) FP-20DA — Conforms 0.31 g Unit: mm 12.8 13.2 Max 11 1 10 0.20 ± 0.10 0.935 Max 1.27 *0.42 ± 0.08 0.40 ± 0.06 *0.27 ± 0.05 0.25 ± 0.04 2.65 Max 7.50 20 0.25 10.40 +– 0.40 1.45 0° – 8° 0.57 0.70 +– 0.30 0.15 0.12 M *Dimension including the plating thickness Base material dimension Hitachi Code JEDEC EIAJ Weight (reference value) FP-20DB Conforms — 0.52 g Cautions 1. Hitachi neither warrants nor grants licenses of any rights of Hitachi’s or any third party’s patent, copyright, trademark, or other intellectual property rights for information contained in this document. Hitachi bears no responsibility for problems that may arise with third party’s rights, including intellectual property rights, in connection with use of the information contained in this document. 2. Products and product specifications may be subject to change without notice. Confirm that you have received the latest product standards or specifications before final design, purchase or use. 3. Hitachi makes every attempt to ensure that its products are of high quality and reliability. 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Even within the guaranteed ranges, consider normally foreseeable failure rates or failure modes in semiconductor devices and employ systemic measures such as failsafes, so that the equipment incorporating Hitachi product does not cause bodily injury, fire or other consequential damage due to operation of the Hitachi product. 5. This product is not designed to be radiation resistant. 6. No one is permitted to reproduce or duplicate, in any form, the whole or part of this document without written approval from Hitachi. 7. Contact Hitachi’s sales office for any questions regarding this document or Hitachi semiconductor products. Hitachi, Ltd. Semiconductor & Integrated Circuits. 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