iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A switched-capacitor filter’s cutoff or center frequency is tied to its switching clock by a ratio set by the specific device. Because the filter samples its input, frequencies above half the clock rate can alias into the band you want to keep. If the source may contain such energy, consider analog filtering before the switched-capacitor stage; an input RC network can help, but its own response must not remove wanted signal. External-component requirements also vary by part and operating range, so use the selected device’s datasheet and application circuit rather than assuming one standard design.
What does the clock rate do?
A switched-capacitor circuit uses periodic switching to emulate frequency-dependent behavior. Its characteristic frequency—such as a low-pass cutoff or a filter’s center frequency—therefore tracks the switching clock. The exact relationship is device-specific: the clock is not simply interchangeable with the filter cutoff, and there is no one universal clock-to-cutoff ratio for all switched-capacitor filters.
Texas Instruments describes the center or cutoff frequency as proportional to the clock and notes that it can be varied over a wide range without changing external circuitry. Its filter introduction also discusses different ratios used by different devices. A clock-frequency change consequently shifts the filter’s characteristic frequency in proportion to the device’s ratio. Clock error or instability likewise affects that frequency.
Free tools Windows power users keep installed
One-click scans. No signup required.
Use the chosen part’s ratio, not a class-wide rule
The TLC04 is one concrete example: its listed clock-to-cutoff ratio is 50:1. With that ratio, a 30 kHz cutoff corresponds to a 1.5 MHz clock, calculated as 30 kHz × 50. TI lists a cutoff-frequency range of 0.1 Hz to 30 kHz under the supply conditions shown on its product information page. Those figures describe this device and its listed conditions, not every switched-capacitor filter. Check its datasheet for the permitted clock range and other operating limits before selecting a clock.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
A separate example in Analog Devices’ historical Design Note 16 uses an LTC1064-1 as an eighth-order Cauer low-pass filter with a 40 kHz cutoff and a 4 MHz clock. The figures describe that particular circuit; they do not establish a general ratio for other parts. The note’s example is available in Design Note 16.
Translate a target frequency into a clock choice
- Define the wanted response. Identify whether the application needs a low-pass cutoff, a high-pass response, a notch, or a band-pass center frequency, and determine the useful passband and transition width.
- Find the device’s stated ratio and clock limits. Use the selected part’s datasheet and application circuit. Do not infer its ratio from a different part’s example.
- Calculate the corresponding clock. For a stated clock-to-cutoff ratio, multiply the desired cutoff by that ratio. Verify that the result lies within the part’s specified operating range.
- Check clock quality and system effects. Account for clock stability and frequency error, then inspect the device documentation for clock ripple, feedthrough, noise, distortion, and supply requirements relevant to the system.
This sequence helps distinguish two related but different questions: whether the clock can place the filter response where needed, and whether the sampled-data behavior and clock-related artifacts are acceptable in the full signal path.
Why can aliasing happen?
A switched-capacitor filter is a sampled-data system. Sampling can make some higher-frequency input content appear at a lower apparent frequency. TI’s filter introduction identifies input frequencies higher than one-half the clock frequency as a source of aliasing in switched-capacitor filters. Analog Devices explains the system consequence in its anti-aliasing article: if an out-of-band signal aliases into the band of interest, downstream processing cannot recover which part of the observed signal came from the original in-band content and which came from the aliased input.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
That is why a filter’s intended passband alone does not establish protection from all unwanted input frequencies. Consider the input spectrum as well as the filter response. A source may carry energy far above the useful passband; if that energy reaches the sampling operation and folds into the band you care about, the switched-capacitor filter cannot restore the original distinction afterward.
Does every design need an anti-alias filter?
Not automatically. The need depends on the signal the source can deliver, the selected filter and clock, and how much aliased energy the application can tolerate. If input content above half the clock rate is negligible, or the system’s signal and rejection requirements otherwise permit it, a separate input filter may not be needed. If significant out-of-band energy could alias into a sensitive band, address it in the analog path before the switched-capacitor stage.
Anti-alias filtering has to occur before the sampling operation. Once aliasing has happened, filtering after that stage cannot generally distinguish the aliased component from genuine signal at the same apparent frequency. Analog Devices states the principle directly: “Anti-aliasing must be done in the analog domain, before the signal is sampled.”
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Can a simple RC filter go before the switched-capacitor filter?
An input RC low-pass is one possible way to reduce unwanted high-frequency energy before sampling. It is not a universal fix: its corner frequency and attenuation have to suit both the source spectrum and the rejection the application needs. A single RC choice cannot be assumed to remove every possible alias-producing component while preserving every desired signal.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →The main trade-off is that the RC network also changes the signal you want to pass. Texas Instruments cautions that adding a low-pass ahead of a high-pass or notch filter may be a poor fit if it trims useful bandwidth. For any topology, make sure the added attenuation and phase or amplitude change across the wanted region are acceptable; select the network from the actual signal requirements rather than from the switched-capacitor clock alone.
Practical checks before choosing an RC network
- Establish the useful input band and the highest out-of-band energy the source may contain.
- Identify which out-of-band components could alias into a frequency region that matters.
- Set the required reduction for those components and check whether a simple RC response can supply it.
- Check the RC network’s effect across the wanted passband, especially before a high-pass or notch function.
- Verify the complete source-to-filter response in the intended circuit; do not treat the RC section as a substitute for checking the selected device’s datasheet and application circuit.
The sources do not establish a universal RC corner frequency. It depends on the input spectrum, desired response, and acceptable alias rejection for the particular system.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
What external components does a switched-capacitor filter need?
Requirements differ by device and sometimes by operating range or response requirement. Some filters may need no external components for a stated function or range; others need support components to meet a response condition. Always confirm the pin connections, clock, supply, input and output constraints, and any required capacitors in the selected part’s current datasheet and application circuit.
Two device examples show why the datasheet matters
- LTC1064-1: Analog Devices’ Design Note 16 says no external components are required for cutoff frequencies up to 20 kHz in the described use. Above 20 kHz, it specifies two small capacitors to maintain passband flatness. Its eighth-order Cauer example has a 40 kHz cutoff and uses a 4 MHz clock. These are part- and circuit-specific details in a historical design note, not a rule for the entire filter category.
- TLC04: TI describes a fourth-order Butterworth low-pass with a 50:1 clock-to-cutoff ratio and a listed 0.1 Hz to 30 kHz cutoff range under its stated supply conditions. Those product details do not, by themselves, replace checking the full datasheet for the circuit’s external-component and operating requirements.
The TLC04 figures are on TI’s product information page; the LTC1064-1 guidance is in Design Note 16. Neither example should be generalized to unrelated parts. Current lifecycle and inventory status are not established by those technical examples.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11What clock-related artifacts should I check?
A switched-capacitor filter is not identical to an ideal continuous-time filter. Analog Devices’ filter primer notes that the output may contain clock-rate steps or spikes, and that the response can depart from an ideal continuous-time model as the filter pole approaches the clock. The amount and significance depend on the design; these observations should prompt a device-specific check, not an assumption that every filter has the same artifact level.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Analog Devices’ application note AN40 illustrates clock feedthrough, sidebands around the clock, and an input harmonic that appears as an alias in LTC1064-1 examples. These examples make the relevant inspection points concrete, but they do not specify fixed artifact levels for other parts or implementations. See AN40 and the chosen device’s documentation when deciding whether such behavior falls within the system’s bandwidth or noise limits.
How should I compare clock and filter options?
Compare candidates against the application’s actual signal and response needs rather than choosing the highest available clock or copying a ratio from another part. A useful comparison includes:
- the desired passband, cutoff or center frequency, and transition width;
- the device-specific clock-to-characteristic-frequency ratio and supported clock range;
- clock stability and the resulting effect of frequency error on the filter response;
- the expected out-of-band input content and the alias rejection the application requires;
- whether pre-sampling analog filtering can reduce that content without compromising the wanted response;
- external components needed for the chosen part and operating conditions; and
- clock ripple or feedthrough, noise, distortion, and supply requirements relevant to the application.
Manufacturer sources provide examples, not a universal optimum ratio or a universal anti-alias RC corner. Decide first what the input and passband require, then use the chosen device’s specifications to determine whether its clock and any supporting circuitry fit.
Recommended Free Tools
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
