1. Operating Frequency: - HEF4541: 36MHz - CD4541: 100kHz The internal oscillator frequency limit of the HEF4541 is significantly higher than that of the CD4541. If the original circuit uses this high frequency to achieve high-precision, short-duration timing pulses or as a clock source, the replacement device will either fail to oscillate or produce severely incorrect output frequencies. The CD4541 is only suitable for relatively low-frequency, long-delay timing applications. 2. Supply Voltage Range: - HEF4541: 4.5V to 15.5V - CD4541: 3V to 20V The CD4541 offers a wider voltage tolerance. Its lower limit of 3V supports modern 3.3V logic systems, whereas the HEF4541 cannot operate reliably below 4.5V. The upper limit of 20V also gives the CD4541 an advantage in industrial high-voltage environments. When substituting, verify that the original design voltage falls within the overlapping range of both devices (4.5V to 15.5V). 3. Operating Temperature Range: - HEF4541: -40°C to 85°C - CD4541: -55°C to 125°C The CD4541 is a military/industrial-grade device suitable for harsher environments (e.g., automotive, aerospace, high-temperature industrial equipment). The HEF4541 is a standard industrial/extended commercial-grade part. Substitution is generally acceptable in typical industrial or consumer products, but for extreme environments, the CD4541 is the more reliable choice. 4. Internal Structure and Current Consumption (Implicit Differences): The HEF4541 datasheet specifies a typical current consumption (500µA), while the CD4541 does not. Although both belong to the CMOS 4000 series, differences in internal circuit design (such as oscillator structure and output drive) between manufacturers can lead to variations in dynamic power consumption, power-up behavior, and noise immunity. In low-power or noise-sensitive applications, system stability after substitution should be verified through actual testing. 5. Manufacturer and Internal Counter Structure: The CD4541BE parameters note “Count: 65536” (i.e., a 16-bit binary counter), whereas the HEF4541 does not explicitly state this. Both devices are functionally compatible in terms of basic programmable frequency division/timing, but subtle timing differences may exist in internal counter stages and programming methods (e.g., reset behavior, initial state). In applications requiring strict synchronization or specific power-up timing, review the timing diagrams in both datasheets.