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Final Electrical Specifications
LT1567 1.4nV/Hz 175MHz Op Amp and Inverter / Filter Building Block
August 2001
FEATURES
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DESCRIPTIO
Single-Ended to Differential Conversion Low Noise: 1.4nV/Hz 20VRMS 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
The LT(R)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. 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.
APPLICATIO S
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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
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
2MHz 3-Pole Antialias Filter with Single-Ended to Differential Conversion
V+ 536 270pF 1 2 270pF 0.1F 3 4 0.1F LT1567 8 7 6 5 270pF +AIN ADC -AIN 147 LTC1420
-30 12
0.1F
6 0
536 VIN
536
GAIN (dB)
147
-6 -12 -18 -24 NOTE: THIS IS RESPONSE FROM SINGLE-ENDED VIN TO DIFFERENTIAL VOLTAGE ACROSS ADC INPUT, SO THERE IS A BUILT-IN 6dB GAIN. 1M FREQUENCY (Hz) 10M
1567 TA01a
V-
-36 100
96dB DIFFERENTIAL SNR AT 3V TOTAL SUPPLY.
1567 TA01
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.
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Frequency Response
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LT1567
ABSOLUTE
(Note 1)
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PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW OAOUT OAIN BYPASS V- 1 2 3 4 8 7 6 5 V+ INVOUT INVIN GND
Total Supply Voltage (V+ to V -) ............................ 12.6V Input Voltage (Note 2) ............................................. VS Input Current (Note 2) .......................................... 5mA Operating Temperature Range ..................... 0C to 70C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
LT1567CMS8 MS8 PART MARKING LTWH
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 40C, JA = 160C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 2.5V, RL = 1K, VOUT = 0 both amplifiers unless otherwise noted.
PARAMETER Total Supply Voltage Supply Current VS = 1.5V VS = 2.5V VS = 5V VS = 1.5V, RL = 1k VS = 2.5V, RL = 1k VS = 2.5V, RL=100 VS = 5V, RL = 1k VS = 1.5V, RL = 1k VS = 2.5V, RL = 1k VS = 2.5V, RL=100 VS = 5V, RL = 1k VS = 1.5V, RL = 1k VS = 2.5V, RL = 1k VS = 5V, RL = 1k VS = 1.5V, RL = 1k VS = 2.5V, RL = 1k VS = 5V, RL = 1k VS = 1.5V VS = 5V VS = 1.5V, VCM = -0.25V to 0.25V VS = 5V, VCM = -2.5V to 2.5V VS = 1.5V to 5V, VCM = 0V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN 2.7
TYP 8.5 9 11
MAX 12 15 16 19
UNITS V mA mA mA V V V V V V V V V V V V V V
OA Output Positive Voltage Swing
1.30 2.20 2.00 4.70 -1.30 -2.20 -2.00 -4.70 1.30 2.20 4.60 -1.30 -2.20 -4.50 -0.25 -2.5 90 75 80
1.45 2.40 2.25 4.85 -1.45 -2.44 -2.20 -4.90 1.40 2.40 4.90 -1.40 -2.40 -4.80 0.25 2.5 90 100 1 6 3 9
OA Output Negative Voltage Swing
INV Output Positive Voltage Swing
INV Output Negative Voltage Swing
Common Mode (GND) Input Voltage Range (See Pin Functions) DC Common Mode Rejection Ratio (CMRR) DC Power-Supply Rejection Ratio (PSRR) OA Input Offset Voltage Magnitude INV Output Offset Voltage Magnitude
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LT1567
The q denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 2.5V, RL = 1K, VOUT = 0 both amplifiers unless otherwise noted.
PARAMETER OA Input Bias Current GND Input Bias Current 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 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 VS = 2.5V, RL = 1k, VIN = -2V to 2V Measured at 2MHz, VS = 1.5V Measured at 2MHz, VS = 2.5V Measured at 2MHz, VS = 5V Measured at 2MHz f = 100kHz f = 100kHz fC = 2MHz, BW = 4MHz fC = 5MHz, BW = 10MHz f = 1MHz, fC = 2MHz, VOUT = 1VRMS f = 2.5MHz, fC = 5MHz, VOUT = 1VRMS f = 100kHz, OA Connected as Unity-Gain Inverter CONDITIONS
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ELECTRICAL CHARACTERISTICS
MIN
TYP 3 6
MAX 10 15
UNITS A A V/mV V/mV V/mV V/mV
7.5 10 1.2 15 0.97 0.97 0.97 0.97 450 100 110 120 0.96
23 35 4.0 40 1.04 1.04 1.04 1.04 600 160 175 190 1.0 49 1.4 1.0 20 30 -88 -70 35 0.1 1.05 750
INV DC Gain Magnitude
V/V V/V V/V V/V MHz MHz MHz V/V V/sec nV/Hz pA/Hz VRMS VRMS dB dB mA
INV DC Input Resistance OA Gain-Bandwidth Product
INV AC Gain Magnitude OA Slew Rate Magnitude OA Input Voltage Noise Density OA Input Current Noise Density Wideband Output Noise for a Second-Order Filter (Figure 1) Total Harmonic Distortion (THD) for a Second-Order Filter (Figure 1) Output Short-Circuit Current (Either Output) Output Impedance
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.
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LT1567
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 100) at the op amp's unity-gain crossover frequency (circa 100MHz), will impair AC stability. 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 0.1F, 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. Power Supply Pins (Pins 4, 8): The V - and V+ pins should be bypassed with 0.1F 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. 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 0.1F, to a nearby ground plane should be added at the BYPASS pin for a clean wideband ground reference. INVIN (Pin 6): Unity-Gain Inverter Input. The "inverter" (INV) amplifier in the LT1567 is connected to internal resistors (nominally 600 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. 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.
BLOCK DIAGRA
BYPASS V-
3 7pF 4 150
4
-
OAIN
2
+
-
OAOUT
1
+
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Block Diagram with Top View of Pins
8 7 600 600 6 5
V+ INVOUT INVIN GND
LT1567
APPLICATIO S I FOR ATIO
Functional Description
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. 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 180 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.
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Dealing with High Source Impedances 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. 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 0.1F 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 (10F) 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.
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LT1567
APPLICATIO S I FOR ATIO
R2 R1 R3
VIN
C2 VS/2
RESPONSE 0.1dB CHEBYSHEV, 1MHz 0.1dB CHEBYSHEV, 2MHz 0.1dB CHEBYSHEV, 5MHz BUTTERWORTH, 2MHZ
Figure 1. Basic 2nd-Order Lowpass Section Using One LT1567
TYPICAL APPLICATIO
2nd Order Bandpass Filter fCENTER = 1MHz, -3dB BW = 0.707MHZ
C2 470pF
R1 475 VIN
C1 470pF
VS/2 R2 475
fCENTER IF R2 = R3 = R AND C1 = C2 = C, fCENTER = (R/R1) + 1, -3dB BW = (R/R1) + 1 2RC GAIN AT fCENTER = R/R1, MAXIMUM fCENTER IS 5MHz GAIN
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C1 VOUT (INVERTING)
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-
-1
+
LT1567
VOUT2 (NONINVERTING) (OPTIONAL)
1567 F01
C1 120pF 120pF 120pF 180pF
C2 180pF 180pF 180pF 180pF
R1, R2 1050 523 205 604
R3 1180 590 232 309
R3 475
-
-1 VOUT
+
LT1567
1567 TA02
LT1567
PACKAGE DESCRIPTIO
0.007 (0.18) 0.021 0.006 (0.53 0.015)
* 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
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MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.118 0.004* (3.00 0.102) 8 76 5 0.193 0.006 (4.90 0.15) 0.118 0.004** (3.00 0.102) 1 0.043 (1.10) MAX 0 - 6 TYP SEATING PLANE 23 4 0.034 (0.86) REF 0.009 - 0.015 (0.22 - 0.38) 0.0256 (0.65) BSC 0.005 0.002 (0.13 0.05)
MSOP (MS8) 1100
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LT1567
TYPICAL APPLICATIO
RELATED PARTS
PART NUMBER LTC1565-31 LTC1566-1 LTC1564 DESCRIPTION Differential 650kHz Lowpass Filter Differential 2.3MHz Lowpass Filter 10kHz to 150kHz Digitally Controlled Filter and 4-Bit PGA COMMENTS For CDMA Base Stations For WCDMA Base Stations Continuous Time Low Noise 8th Order Filter and PGA
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q www.linear.com
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Single Supply Single-Ended to Differential First Order Lowpass Filter with Gain
R2 C1 150pF 1 R1 VIN 0.1F 3 4 2 LT1567 8 7 6 5 2.49k 0.1F V+ VOUT+ VOUT- GAIN = R2/R1 f- 3dB = 1/(2 R2 C1) f- 3dB MAX = 5MHz 2.49k
1567 TA03
1567i LT/TP 0801 1.5K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2001

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