74HC541 — Octal Non-Inverting 3-State Buffer (Flow-Through Pinout)

Overview

The 74HC541 (SN74HC541 / 74HCT541) is a high-speed silicon-gate CMOS octal non-inverting buffer / line driver IC manufactured by Texas Instruments, Nexperia, and onsemi. Housed in a 20-pin through-hole DIP-20 and surface-mount SOIC-20 / TSSOP-20 package, it was specifically created to solve the messy PCB routing challenges of the older 74HC244 by providing an optimal flow-through pin architecture.

In the 74HC541, all eight data inputs ( $A_0 \dots A_7$ ) are situated consecutively along one side of the chip (Pins 2–9), while all eight corresponding non-inverting outputs ( $Y_0 \dots Y_7$ ) align straight across on the opposite side (Pins 18–11). Both active-LOW output enable pins ( $\bar{OE}_1$ and $\bar{OE}_2$ ) are gated together: when both are LOW, data passes straight through; if either is HIGH, all outputs enter high impedance (Z). Operating from $2.0\text{V}$ to $6.0\text{V}$ DC with a rapid propagation delay of $10\text{ ns}$ , the 74HC541 is the modern standard for microprocessor memory bus buffering, parallel port buffering, microcontroller GPIO line protection, and straight-line LED display drivers.

Quick reference


Logic Family	High-Speed CMOS (74HC) / TTL-Compatible (74HCT)
Function	Octal Non-Inverting 3-State Buffer (Flow-Through Layout)
Bus Architecture	Full 8-Bit Unidirectional Flow-Through Bus
Package	20-pin DIP (DIP-20 / PDIP-20) / 20-pin SOIC / TSSOP-20
Supply Voltage ( $V_{CC}$ )	$2.0\text{ V}$ to $6.0\text{ V}$ (74HC) / $4.5\text{ V} \dots 5.5\text{ V}$ (74HCT)
Propagation Delay ( $t_{pd}$ )	$10\text{ ns}$ typ ( $23\text{ ns}$ max) at $V_{CC} = 5.0\text{ V}$
Output Drive Current ( $I_{OH}/I_{OL}$ )	$\pm 6.0\text{ mA}$ at $5.0\text{ V}$ (15 LSTTL loads)
Controls	Dual Active-LOW Gated Enables ( $\bar{OE}_1$ on Pin 1, $\bar{OE}_2$ on Pin 19)
Alternative Standard	74HC244 (Staggered Pinout Legacy Buffer)

Pinout (DIP-20 Flow-Through Layout)

text

                            ┌───┴───┐
       (Active-Low) /OE1   1│ 1   20│ VCC (+2V to +6V)
             (Data In) A0  2│       │19 /OE2 (Active-Low)
             (Data In) A1  3│ 74HC  │18 Y0 (Data Out)
             (Data In) A2  4│  541  │17 Y1 (Data Out)
             (Data In) A3  5│ DIP-20│16 Y2 (Data Out)
             (Data In) A4  6│       │15 Y3 (Data Out)
             (Data In) A5  7│       │14 Y4 (Data Out)
             (Data In) A6  8│       │13 Y5 (Data Out)
             (Data In) A7  9│       │12 Y6 (Data Out)
                     GND  10│       │11 Y7 (Data Out)
                            └───────┘

Pin	Name	Type	Description
1	`/OE1`	Control Input	Output Enable 1 (Active-LOW; must be LOW with `/OE2` to enable outputs)
2 – 9	`A0 – A7`	Data Inputs	8 Unidirectional Parallel Data Inputs
10	`GND`	Power	Common Ground reference ( $0\text{ V}$ )
11 – 18	`Y7 – Y0`	Data Outputs	8 Non-Inverting 3-State Data Outputs (Ordered $Y_7 \dots Y_0$ )
19	`/OE2`	Control Input	Output Enable 2 (Active-LOW; must be LOW with `/OE1` to enable outputs)
20	`VCC`	Power	Positive Supply Voltage ( $+2.0\text{ V}$ to $+6.0\text{ V}$ )

Function / Truth Table

Enable $\bar{OE}_1$	Enable $\bar{OE}_2$	Data Input ( $A_n$ )	Output ( $Y_n$ )	Bus State
L	L	L	L	Non-Inverting Buffer Active
L	L	H	H	Non-Inverting Buffer Active
H	X	X	Z	High-Impedance (Disabled / Disconnected)
X	H	X	Z	High-Impedance (Disabled / Disconnected)

Comparison: 74HC541 vs 74HC244

Feature	74HC244	74HC541
Input Pins	Pins 2, 4, 6, 8, 11, 13, 15, 17 (Staggered across both sides)	Pins 2–9 (All on Left Side)
Output Pins	Pins 3, 5, 7, 9, 12, 14, 16, 18 (Interleaved)	Pins 11–18 (All on Right Side)
PCB Trace Crossing	High (Requires vias / trace jumping)	Zero (Clean Straight Flow-Through)
Bus Control	Two separate 4-bit enables	Full 8-bit gated enable

Common mistakes

Leaving one OE pin floating or HIGH: The 74HC541 requires BOTH $\bar{OE}_1$ and $\bar{OE}_2$ to be held LOW (GND) to enable the outputs. If either enable pin is pulled HIGH or left floating, all eight outputs will float in high impedance.
Overlooking inverted pin numbering on output side: Note that Pin 2 ( $A_0$ ) corresponds to Pin 18 ( $Y_0$ ), and Pin 9 ( $A_7$ ) corresponds to Pin 11 ( $Y_7$ ).

Notes

74HCT541 Variant: Provides TTL-compatible input levels ( $V_{IH} = 2.0\text{V}$ ), functioning as an 8-bit $3.3\text{V} \to 5.0\text{V}$ unidirectional level shifter for microcontrollers driving 5V legacy bus hardware.