説明

The LTC1562-2 is a low noise, low distortion continuous time filter with rail-to-rail inputs and outputs, optimized for a center frequency (fO) of 20kHz to 300kHz. Unlike most monolithic filters, no clock is needed. Four independent 2nd order filter blocks can be cascaded in any combination, such as one 8th order or two 4th order filters. Each block’s response is programmed with three external resistors for center frequency, Q and gain, using simple design formulas. Each 2nd order block provides lowpass and bandpass outputs. Highpass response is available if an external capacitor replaces one of the resistors. Allpass, notch and elliptic responses can also be realized. The LTC1562-2 is designed for applications where dynamic range is important. For example, by cascading 2nd order sections in pairs, the user can configure the IC as a dual 4th order Butterworth lowpass filter with 90dB signal-to-noise ratio from a single 5V power supply. Low level signals can exploit the built-in gain capability of the LTC1562-2. Varying the gain of a section can achieve a dynamic range as high as 114dB with a ±5V supply. Other cutoff frequency ranges can be provided upon request. Please contact LTC Marketing.

 

特徴

Continuous Time—No Clock

Four 2nd Order Filter Sections, 20kHz to 300kHz Center Frequency

Butterworth, Chebyshev, Elliptic or Equiripple Delay Response

Lowpass, Bandpass, Highpass Responses

99dB Typical S/N, ±5V Supply (Q = 1)

93dB Typical S/N, Single 5V Supply (Q = 1)

Rail-to-Rail Input and Output Voltages

DC Accurate to 3mV (Typ)

±0.5% Typical Center Frequency Accuracy

“Zero-Power” Shutdown Mode

Single or Dual Supply, 5V to 10V Total

Resistor-Programmable fO, Q, Gain

 

アプリケーション

High Resolution Systems (14 Bits to 18 Bits)

Antialiasing/Reconstruction Filters

Data Communications, Equalizers

Dual or I-and-Q Channels (Two Matched 4th Order Filters in One Package)

Linear Phase Filtering

Replacing LC Filter Modules

 

アプリケーション情報

The LTC1562-2 contains four matched, 2nd order, 3-terminal universal continuous-time filter blocks, each with a virtual-ground input node (INV) and two rail-to-rail outputs (V1, V2). In the most basic application, one such block and three external resistors provide 2nd order lowpass and bandpass responses simultaneously (Figure 3, with a resistor for ZIN). The three external resistors program fO, Q and gain. A combination of internal precision components and external resistor R2 sets the center frequency fO of each 2nd order block. The LTC1562-2 is trimmed at manufacture so that fO will be 200kHz ±0.5% if the external resistor R2 is exactly 7958W. The LTC15622 is a higher frequency, pin compatible variant of the LTC1562, with different internal R and C values and higher speed amplifiers. However, lowpass/bandpass filtering is only one specific application for the 2nd order building blocks in the LTC1562-2. Highpass response results if the external impedance ZIN in Figure 3 becomes a capacitor CIN (whose value sets only gain, not critical frequencies) as described below. Responses with zeroes (e.g, elliptic or notch responses) are available by feedforward connections with multiple 2nd order blocks (see Typical Applicatons). Moreover, the virtual-ground input gives each 2nd order section the built-in capability for analog operations such as gain (preamplification), summing and weighting of multiple inputs, or accepting current or charge signals directly. These Operational FilterTM frequency-selective building blocks are nearly as versatile as op amps. The user who is not copying exactly one of the Typical Applications schematics shown later in this data sheet is urged to read carefully the next few sections through at least Signal Swings, for orientation about the LTC1562-2, before attempting to design custom application circuits. Also available free from LTC, and recommended for designing custom filters, is the general-purpose analog filter design software FilterCADTM for Windows®. This software includes tools for finding the necessary f0, Q and gain parameters to meet target filter specifications such as frequency response.