Final Electrical Specifications LT1567 1.4nV/√Hz 175MHz Op Amp and Inverter / Filter Building Block August 2001 U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Single-Ended to Differential Conversion Low Noise: 1.4nV/√Hz 20µVRMS Total Wideband Noise Filter with 2MHz fC Dynamic Range: 104dB SNR at ±5V Supply Voltage 2.7V to 12V Total Rail-to-Rail Outputs DC Accurate: Op Amp VOS 1mV (Typ) Trimmed Bandwidth for Accurate Filters MSOP-8 Surface-Mount Package No External Clock Required U APPLICATIO S ■ ■ ■ ■ ■ Low Noise, High Speed Filters to 5MHz Cellular Base Stations Communication Channel or Roofing Filters Antialias or Reconstruction Filtering Video Signal Processing Single-Ended to Differential Conversion In addition to low noise and high speed LT1567 features single-ended to differential conversion for direct driving of high speed A/D converters. The LT1567 operates from a total power-supply voltage of 2.7V to 12V and can support signal-to-noise ratios above 100dB. The LT1567 is available in an 8-lead MSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ The LT®1567 is an analog building block optimized for very low-noise high-frequency filter applications. It contains two wideband operational amplifiers, one of them internally configured as a unity-gain inverter. With the addition of two capacitors, the LT1567 becomes a flexible second-order filter section with cutoff frequency (fC) up to 5MHz, ideal for antialiasing or for channel filtering in highspeed data communications systems. TYPICAL APPLICATIO 2MHz 3-Pole Antialias Filter with Single-Ended to Differential Conversion Frequency Response V+ 0.1µF 536Ω 6 0 270pF 536Ω VIN 1 8 2 7 147Ω 270pF 0.1µF 3 4 LT1567 6 5 +AIN ADC 270pF –AIN 147Ω GAIN (dB) 536Ω 12 –6 –12 –18 –24 LTC1420 –30 0.1µF V– NOTE: THIS IS RESPONSE FROM SINGLE-ENDED VIN TO DIFFERENTIAL VOLTAGE ACROSS ADC INPUT, SO THERE IS A BUILT-IN 6dB GAIN. –36 100 96dB DIFFERENTIAL SNR AT 3V TOTAL SUPPLY. 1567 TA01 1M FREQUENCY (Hz) 10M 1567 TA01a Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 1 LT1567 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Total Supply Voltage (V+ to V –) ............................ 12.6V Input Voltage (Note 2) ............................................. ±VS Input Current (Note 2) .......................................... ±5mA Operating Temperature Range ..................... 0°C to 70°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW OAOUT OAIN BYPASS V– 1 2 3 4 8 7 6 5 LT1567CMS8 V+ INVOUT INVIN GND MS8 PART MARKING MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 40°C, θJA = 160°C/W LTWH Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = ±2.5V, RL = 1K, VOUT = 0 both amplifiers unless otherwise noted. PARAMETER CONDITIONS MIN Total Supply Voltage TYP 2.7 MAX UNITS 12 V 15 16 19 mA mA mA Supply Current VS = ±1.5V VS = ±2.5V VS = ±5V ● ● ● OA Output Positive Voltage Swing VS = ±1.5V, RL = 1k VS = ±2.5V, RL = 1k VS = ±2.5V, RL=100 VS = ±5V, RL = 1k ● ● ● ● 1.30 2.20 2.00 4.70 1.45 2.40 2.25 4.85 V V V V OA Output Negative Voltage Swing VS = ±1.5V, RL = 1k VS = ±2.5V, RL = 1k VS = ±2.5V, RL=100 VS = ±5V, RL = 1k ● ● ● ● –1.30 –2.20 –2.00 –4.70 –1.45 –2.44 –2.20 –4.90 V V V V INV Output Positive Voltage Swing VS = ±1.5V, RL = 1k VS = ±2.5V, RL = 1k VS = ±5V, RL = 1k ● ● ● 1.30 2.20 4.60 1.40 2.40 4.90 V V V INV Output Negative Voltage Swing VS = ±1.5V, RL = 1k VS = ±2.5V, RL = 1k VS = ±5V, RL = 1k ● ● ● –1.30 –2.20 –4.50 –1.40 –2.40 –4.80 V V V Common Mode (GND) Input Voltage Range (See Pin Functions) VS = ±1.5V VS = ±5V ● ● –0.25 –2.5 DC Common Mode Rejection Ratio (CMRR) VS = ±1.5V, VCM = –0.25V to 0.25V VS = ±5V, VCM = –2.5V to 2.5V ● ● 90 75 90 dB dB VS = ±1.5V to ±5V, VCM = 0V ● 80 100 dB DC Power-Supply Rejection Ratio (PSRR) 8.5 9 11 0.25 2.5 V V OA Input Offset Voltage Magnitude ● 1 3 mV INV Output Offset Voltage Magnitude ● 6 9 mV 2 LT1567 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = ±2.5V, RL = 1K, VOUT = 0 both amplifiers unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS OA Input Bias Current ● 3 10 µA GND Input Bias Current ● 6 15 µA OA DC Open-Loop Gain VS = ±1.5V, RL = 1k, VO = –1V to 1V VS = ±2.5V, RL = 1k, VO= –2V to 2V VS = ±2.5V, RL = 100, VO = –1.5V to 1.5V VS = ±5V, RL = 1k, VO = –4V to 4V ● ● ● ● 7.5 10 1.2 15 INV DC Gain Magnitude VS = ±1.5V, RL = 1k, VIN = –1V to 1V VS = ±2.5V, RL = 1k, VIN = –2V to 2V VS = ±2.5V, RL = 100, VIN = –1.5V to 1.5V VS = ±5V, RL = 1k, VIN = –4V to 4V ● ● ● ● 0.97 0.97 0.97 0.97 INV DC Input Resistance VS = ±2.5V, RL = 1k, VIN = –2V to 2V ● 450 600 OA Gain-Bandwidth Product Measured at 2MHz, VS = ±1.5V Measured at 2MHz, VS = ±2.5V Measured at 2MHz, VS = ±5V ● ● ● 100 110 120 160 175 190 INV AC Gain Magnitude Measured at 2MHz ● 0.96 1.0 OA Slew Rate Magnitude 23 35 4.0 40 V/mV V/mV V/mV V/mV 1.04 1.04 1.04 1.04 750 V/V V/V V/V V/V Ω MHz MHz MHz 1.05 V/V 49 V/µsec f = 100kHz 1.4 nV/√Hz OA Input Current Noise Density f = 100kHz 1.0 pA/√Hz Wideband Output Noise for a Second-Order Filter (Figure 1) fC = 2MHz, BW = 4MHz fC = 5MHz, BW = 10MHz 20 30 µVRMS µVRMS Total Harmonic Distortion (THD) for a Second-Order Filter (Figure 1) f = 1MHz, fC = 2MHz, VOUT = 1VRMS f = 2.5MHz, fC = 5MHz, VOUT = 1VRMS –88 –70 dB dB 35 mA 0.1 Ω OA Input Voltage Noise Density Output Short-Circuit Current (Either Output) Output Impedance f = 100kHz, OA Connected as Unity-Gain Inverter Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The inputs of each op amp are protected by back-to-back diodes. If either differential input voltage exceeds 1.4V, the input current should be limited to less than 5mA. 3 LT1567 U U U PI FU CTIO S OAOUT (Pin 1): Output of the Uncommitted Op Amp (OA). As with most wideband op amps, it is important to avoid connecting heavy capacitive loads (above about 10pF) directly to this output. Such loads, exhibiting low impedance (circa 100Ω) at the op amp’s unity-gain crossover frequency (circa 100MHz), will impair AC stability. GND (Pin 5): DC Ground Input. Sets the noninverting inputs for the two internal amplifiers; designed for use as a DC reference, not a signal input.The GND input includes a small series resistor, both to balance DC offsets in the presence of input bias currents and also to suppress the “Q” factor of possible parasitic high-frequency resonant circuits introduced by wiring inductance. The on-chip ground reference at the noninverting inputs of the two amplifiers is decoupled for very high frequencies with a small internal capacitor to the chip substrate, nominally 7pF. An external capacitor, typically 0.1µF, to a nearby ground plane should be added at the BYPASS pin for a clean wideband ground reference. OAIN (Pin 2): Inverting or “–” Input of the Uncommitted Op Amp (OA) in the LT1567. The noninverting or “+” input of this amplifier is shared with that of the INV amplifier and accessed via the GND and BYPASS pins. The OA amplifier is optimized for minimal wideband noise. BYPASS (Pin 3): AC Ground Bypass. Designed for a decoupling capacitor, typically 0.1µF, to a printed circuit ground plane using the shortest possible wiring. Use GND for DC connection of the amplifier noninverting inputs as described in the GND (Pin 5) description. INVIN (Pin 6): Unity-Gain Inverter Input. The “inverter” (INV) amplifier in the LT1567 is connected to internal resistors (nominally 600Ω each) to form a closed-loop amplifier with a wideband voltage gain of nominally –1. The amplifier in this position is similar to the uncommitted op amp (OA) but is optimized for high frequency linearity. Power Supply Pins (Pins 4, 8): The V – and V+ pins should be bypassed with 0.1µF capacitors to an adequate analog ground plane using the shortest possible wiring. Electrically clean supplies and a low impedance ground are important for the high dynamic range and bandwidth available from the LT1567. Low noise linear power supplies are recommended. Switching supplies are not recommended because of the inevitable risk of their switching noise coupling into the signal path, reducing dynamic range. INVOUT (Pin 7): Output of the INV or “Inverter” Amplifier, with a Nominal Gain of –1 from the INVIN Pin. As with most wideband op amps, it is important to avoid connecting heavy capacitive loads (above about 10pF) directly to this output. Such loads, exhibiting low impedance (circa 100 ohms) at the op amp’s unity-gain crossover frequency (circa 100MHz), will impair AC stability. W BLOCK DIAGRA Block Diagram with Top View of Pins OAIN 2 BYPASS 3 – 1 + OAOUT 8 V+ 7 INVOUT 6 INVIN 5 GND + – 600Ω 7pF V– 4 4 600Ω 150Ω LT1567 U W U U APPLICATIO S I FOR ATIO Functional Description Dealing with High Source Impedances The LT1567 contains two low-noise wideband operational amplifiers, one of them connected internally as a unitygain inverter. These two amplifiers can form a secondorder multiple-feedback filter configuration (Figure 1) for megahertz signal frequencies, with exceptionally low total noise. The amplifier in the dedicated inverter (INV) is optimized for better high frequency linearity while the uncommitted operational amplifier (OA) is optimized for lower input noise voltage, according to the different sensitivities to these effects in the filter section. This combination produces a low-noise filter with better distortion performance than would be possible with identical amplifiers. The voltage VIN in Figure 1 , on the left side of R1, is the signal voltage that the filter sees. If a voltage source with significant internal impedance drives the VIN node in Figure 1, then the filter input VIN may differ from the source’s open-circuit output, and the difference can be complex, because the filter presents a complex impedance to VIN. A rule of thumb is that a source impedance is negligibly “low” if it is much smaller than R1 at frequencies of interest. Otherwise, the source impedance (resistive or reactive) effectively adds to R1 and may change the signal frequency response compared to that with a low source impedance. If the source is resistive and predictable, then it may be possible to design for it by reducing R1. Unpredictable or nonresistive source impedances that are not well below R1 should be buffered. Signal Ground Both operational amplifiers within the LT1567 are designed for inverting operation (constant common mode input) and they share a single ground reference node on the chip. Two pins permit access to this node: GND and BYPASS. For a clean on-chip ground reference over a wide bandwidth, the normal procedure is to connect GND to a DC ground potential and BYPASS to a decoupling capacitor that returns to a ground plane. Differential Output Feature The multiple-feedback filter section of Figure 1 inherently includes two outputs of opposite signal polarity: a DCinverting output from the OA (Pin 1) and a DC noninverting output from the INV block (Pin 7). These two outputs maintain equal gain and 180º phase shift over a wide frequency range. This feature permits choosing the signal polarity in single-ended applications, and also performs single-ended-to-differential conversion. The latter property is useful in an antialias filter to drive standard monolithic A/D converters having differential inputs, as illustrated on page 1. Construction and Instrumentation Cautions Electrically clean construction is important in applications seeking the full dynamic range and bandwidth of the LT1567. Using the shortest possible wiring or printedcircuit paths will minimize parasitic capacitance and inductance. High quality supply bypass capacitors of 0.1µF near the chip, connected to a ground plane, provide good decoupling from a clean, low inductance power source. But several inches of wire (i.e., a few microhenrys of inductance) from the power supplies, unless decoupled by substantial capacitance (≥10µF) near the chip, can cause a high Q LC resonance in the hundreds of kHz in the chip’s supplies or ground reference. This may impair filter performance at those frequencies. In stringent filter applications we have often found that a compact, carefully laid out printed circuit board with good ground plane makes a difference in both stopband rejection and distortion. Finally, equipment to measure filter performance can itself introduce distortion or noise floors. Checking for these limits with a wire replacing the filter is a prudent routine procedure. 5 LT1567 U U W U APPLICATIO S I FOR ATIO R2 VIN R1 C1 R3 VOUT (INVERTING) – VOUT2 (NONINVERTING) (OPTIONAL) –1 C2 VS/2 + LT1567 1567 F01 RESPONSE 0.1dB CHEBYSHEV, 1MHz 0.1dB CHEBYSHEV, 2MHz 0.1dB CHEBYSHEV, 5MHz BUTTERWORTH, 2MHZ C1 120pF 120pF 120pF 180pF C2 180pF 180pF 180pF 180pF R1, R2 1050Ω 523Ω 205Ω 604Ω R3 1180Ω 590Ω 232Ω 309Ω Figure 1. Basic 2nd-Order Lowpass Section Using One LT1567 U TYPICAL APPLICATIO 2nd Order Bandpass Filter fCENTER = 1MHz, –3dB BW = 0.707MHZ C2 470pF R3 475Ω C1 470pF R1 475Ω – VIN –1 VS/2 R2 475Ω VOUT + LT1567 1567 TA02 fCENTER IF R2 = R3 = R AND C1 = C2 = C, fCENTER = √(R/R1) + 1, –3dB BW = √(R/R1) + 1 2πRC GAIN AT fCENTER = R/R1, MAXIMUM fCENTER IS 6 5MHz GAIN LT1567 U PACKAGE DESCRIPTIO MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) 1 2 3 4 0.043 (1.10) MAX 0.007 (0.18) 0.034 (0.86) REF 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.009 – 0.015 (0.22 – 0.38) 0.0256 (0.65) BSC 0.005 ± 0.002 (0.13 ± 0.05) MSOP (MS8) 1100 * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 7 LT1567 U TYPICAL APPLICATIO Single Supply Single-Ended to Differential First Order Lowpass Filter with Gain VOUT+ R2 VOUT– C1 150pF R1 VIN 1 8 2 7 0.1µF 3 LT1567 4 V+ 0.1µF 6 5 GAIN = R2/R1 f– 3dB = 1/(2π R2 C1) f– 3dB MAX = 5MHz 2.49k 2.49k 1567 TA03 RELATED PARTS PART NUMBER DESCRIPTION LTC1565-31 Differential 650kHz Lowpass Filter For CDMA Base Stations LTC1566-1 Differential 2.3MHz Lowpass Filter For WCDMA Base Stations LTC1564 10kHz to 150kHz Digitally Controlled Filter and 4-Bit PGA Continuous Time Low Noise 8th Order Filter and PGA 8 Linear Technology Corporation COMMENTS 1567i LT/TP 0801 1.5K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2001