Features and Benefits
- Up to 10MHz Center Frequency on a Single 3V Supply
- Easy to Use—A Single Resistor Value Sets Lowpass Cutoff Frequency (200kHz < fC < 5MHz), Unequal Resistor Values Extend Cutoff Frequency Up to 10MHz
- Extremely Flexible—Different Resistor Values Allow Lowpass Transfer Functions with or Without Gain
- SNR = 92dB (fC = 2MHz, 2VP-P)
- THD = –84dB (fC = 2MHz, 1VP-P)
- Internal Capacitors Trimmed to ±0.75%
- Single 4-Pole Lowpass Filter or Matched Pair of 2-Pole Lowpass Filters
- Can be Connected as a Bandpass Filter
- Single-Ended or Differential Output
- Operates from Single 3V (2.7V Min) to ±5V Supply
- Rail-to-Rail Input and Output Voltages
The LT1568 is an easy-to-use, active-RC filter building block with rail-to-rail inputs and outputs. The internal capacitors of the IC and the GBW product of the internal low noise op amps are trimmed such that consistent and repeatable filter responses can be achieved. With a single resistor value, the LT1568 provides a pair of matched 2-pole Butterworth lowpass filters with unity gain suitable for I/Q channels.
By using unequal-valued external resistors, the two 2-pole sections can create different frequency responses or gains. In addition, the two stages may be cascaded to create a single 4-pole filter with a programmable response. Capable of cutoff frequencies up to 10MHz, the LT1568 is ideal for antialiasing or channel filtering in high speed data communications systems. The LT1568 can also be used as a bandpass filter.
The LT1568 features very low noise, supporting signal-to-noise ratios of over 90dB. It also provides single-ended to differential signal conversion for directly driving high speed A/D converters. The LT1568 has a shutdown mode that reduces supply current to approximately 0.5mA on a 5V supply.
The LT1568 is available in a narrow 16-lead SSOP package.
- Replaces Discrete RC Active Filters and LC Filter Modules
- Antialiasing/Reconstruction Filters
- Dual or I-and-Q Channels (Two Matched 2nd Order Filters in One Package)
- Single-Ended to Differential Conversion
- Video Signal Processing
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit DC675C is for the evaluation of filter circuits using an LT1568. The LT1568 is a dual 2nd order active-RCfilterbuildingblockwithprecision ±0.75% capacitors and low noise op amps with 180MHz GBW trimmed to ±10% maximum variation. The ±10% GBW variation of the LT1568 op amps allows for minimizing the higher frequency error by decreasing resistor values. The cutoff or center frequency (fC) range of an LT1568 filter is 200kHz to 10MHz (5MHz for a bandpass filter). The low limit of 200kHz was chosen only to minimize resistor noise and DC offsets (using external capacitors the fC frequency can be less than 200kHz).
For testing and evaluation, the DC675C assembly is configured as a single 4th order, 500kHz narrow passband bandpass filter.
For other possible LT1568 configurations, the DC675C has unused pads for 0805 surface mount resistors and capacitors preconfigured with PCB traces to allow for the following high accuracy LT1568 filter circuits:
- 4th order lowpass filter
- 5th order lowpass filter
- 4th order narrow passband bandpass
- 4th order wide passband bandpass
- 4th order highpass filter
Refer to the LT1568 data sheet for additional information about filter circuit configurations.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.