SN74LS85N - 4-Bit Magnitude Comparator | Texas Instruments
MPN： SN74LS85N ✓ 啟用中SN74LS85N 概覽
A magnitude comparator is a combinational logic IC that determines the relative ordering of two unsigned binary or coded words. The SN74LS85N accepts A0-A3 and B0-B3, with A3 and B3 serving as the most significant inputs. Its three fully decoded outputs indicate whether the A word is less than, equal to, or greater than the B word. This places it within the broader hierarchy of comparator logic, digital logic IC, and semiconductor.
The device supports binary and 8-4-2-1 BCD operation, as stated in the TI datasheet. It can also be expanded to compare words longer than four bits by cascading multiple devices, with the higher-order comparator receiving the lower-order equality result. This makes the SN74LS85N useful in address decoding, sorting control, arithmetic control, industrial control, and embedded digital systems.
The SN74LS85N is identified as a 16-pin PDIP by the distributor data. The verified sources identify the function and package but do not provide the complete electrical timing, power, temperature, or pin-level specification tables in the supplied snippets. Those values are therefore marked as data needed rather than inferred. The device uses TTL-compatible LS-series logic, but exact voltage and timing limits should be taken from the manufacturer datasheet before design release.
Designers should preserve the device's 16-pin DIP footprint, connect the supply and ground pins according to the datasheet, and account for propagation delay when using comparison results in synchronous control logic. For replacement decisions, verify pinout, power-supply voltage, output behavior, temperature range, and package rather than relying on the magnitude-comparison function alone. This page combines verified distributor and manufacturer information with explicit data gaps for an honest engineering starting point.
直接替換替代品，適用於 SN74LS85N — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： SN74LS85N （相同外形與佔位） — 差異在於 Expansion, Logic Family, Mounting Type, Package, Supported Codes.
SN74LS85NS
✅ 直接替換📋 參考替代品（不在目錄中）
DM74LS85N
✅ 直接替換📋 參考替代品（不在目錄中）
SN74LS85N 最大額定值與電氣特性
| Product Type | 4-bit magnitude comparator |
| Logic Family | 74LS TTL series |
| Comparison Width | 4 bits |
| Input Word A | A0-A3 |
| Input Word B | B0-B3 |
| Most Significant Inputs | A3 and B3 |
| Decision Outputs | A<B, A=B, A>B |
| Supported Codes | Straight binary and straight BCD (8-4-2-1) |
| Logic Type | Combinational magnitude comparator |
| 封裝 | 16-pin PDIP |
| 安裝類型 | Through-hole |
| Output Polarity | Active high |
| Expansion | Fully expandable to words longer than 4 bits by cascading |
SN74LS85N 16-pin pdip 腳位配置指南
SN74LS85N（16-pin pdip 封裝）的腳位配置。 此類比元件具有輸入、輸出與電源腳位。偏移歸零、補償與致能腳位配置請參閱製造商資料表。適用於訊號調理與放大器電路。
無詳細腳位定義資料： SN74LS85N.
請參閱 資料表 以查看完整腳位配置。
典型應用
SN74LS85N 適用於 6 應用s: Industrial Address Decoding, BCD Counter and Display Control, Embedded Digital Sorting Control, Arithmetic and Threshold Control, Legacy Digital Logic Repair, Multi-Bit Comparison Cascades.
Industrial Address Decoding
The SN74LS85N fits industrial address-decoding and control logic because it compares two 4-bit words and produces active-high A<B, A=B, and A>B decisions. It can be placed after a bus decoder or latch to determine whether an address equals, precedes, or follows a programmed value. The 16-pin PDIP footprint is useful for through-hole industrial controller boards and legacy equipment repairs. Designers should use the manufacturer pinout and timing data when connecting the comparator, and should include propagation delay in control timing budgets.
推薦
BCD Counter and Display Control
The SN74LS85N is suitable for comparing straight BCD 8-4-2-1 values in decimal-counter and display-control systems. A digit-value comparator can determine whether a counter has reached a threshold, while its A=B output can trigger count-state sequencing. Because the device is specifically documented for straight BCD, it aligns with systems that represent decimal digits directly. Validate valid BCD states and include comparator propagation delay before sampling the decision outputs.
推薦
Embedded Digital Sorting Control
The SN74LS85N can provide a hardware comparison stage in embedded sorting, threshold, and ranking control. The A and B input words are compared, and the three decision outputs identify the ordering without requiring a software comparison at that stage. This can reduce decision latency in small control systems, although the actual system speed is bounded by the device's propagation delay and the surrounding register or latch timing. The 16-pin PDIP package suits repairable and through-hole controller platforms.
推薦
Arithmetic and Threshold Control
Use the SN74LS85N where a digital system must make threshold decisions from two 4-bit values, such as detecting when one internal state is above, below, or equal to another. Its three decoded outputs make it possible to implement separate greater-than, less-than, and equality actions with standard logic signals. This is useful in stepper-motor indexing, batch-control, and legacy automation circuits. Confirm supply and timing limits from the TI datasheet and add margin for any downstream gate delays.
推薦
Legacy Digital Logic Repair
The SN74LS85N is a practical replacement candidate for legacy through-hole boards requiring a 4-bit magnitude-comparison function. Its documented 16-pin PDIP package and standard 74LS logic family make it convenient for repair inventories and DIP-compatible assemblies. The part should not be selected solely because a board contains a comparator symbol; verify pin numbering, supply voltage, pinout, timing, and any previous manufacturer-specific substitutions. Compare against the original device's datasheet before installation.
推薦
Multi-Bit Comparison Cascades
The SN74LS85N can be cascaded to evaluate words wider than four bits, allowing a system to compare an 8-bit, 12-bit, or larger value by combining lower- and higher-order comparator stages. The lower stage supplies the equality result used by the higher stage after the more significant bits are evaluated. This architecture reduces the amount of comparison logic required in a controller while retaining explicit A<B, A=B, and A>B outputs at the final stage. Timing closure and expansion wiring must be validated carefully.
推薦
推薦產品摘要
工程參考資料，適用於 SN74LS85N — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | SN74LS85NS | DM74LS85N |
|---|---|---|---|
| Product Type | 4-bit magnitude comparator | 74LS85-family comparator | 4-bit comparator |
| Package | 16-pin PDIP | 16-pin PDIP - same package designation in verified comparison result | 16-pin PDIP - indicated by Futurlec result |
| Brand | Texas Instruments | Texas Instruments | onsemi |
主要差異化特點
- Explicit binary and BCD comparison support (對比SN74LS85NS)
- Fully expandable comparison architecture (對比DM74LS85N)
- Three decoded decision outputs (對比DM74LS85N)
設計說明
Use the manufacturer pinout before laying out or repairing a board. The verified data confirms a 16-pin PDIP package but does not provide the complete pin-number table, so do not infer pin assignments from signal names. Keep the comparator's data inputs and expansion connections short where possible, and place any logic used to interpret A<B, A=B, and A>B close to the device. Confirm ground and supply connections against the TI datasheet.
The comparison result is valid only after the propagation delay through the logic path. Treat the three decision outputs as changing within a specified interval rather than assuming an instantaneous relationship between input transitions and outputs. In a cascaded multi-bit comparator, the higher-order stage must receive the lower-stage equality signal with enough timing margin. Add downstream gate delay and board interconnect margin when the comparison controls synchronous machinery.
Do not treat any 74LS85-family part as automatically interchangeable without checking supply voltage, pinout, timing, temperature, and output behavior. SN74LS85NS appears in the supplied comparison data, and DM74LS85N is listed as a possible equivalent, but the snippets do not establish complete electrical equivalence. For production substitution, compare the official datasheets and validate the assembled circuit at maximum intended input rates.
合規資訊
The supplied verified web data does not state compliance or regulatory status for SN74LS85N. Confirm current declarations with Texas Instruments or an authorized distributor.