LTC6404 600MHz, Low Noise, High Precision Fully Differential Input/Output Amplifier/Driver FEATURES DESCRIPTION n The LTC(R)6404 is a family of AC precision, very low noise, low distortion, fully differential input/output amplifiers optimized for 3V, single supply operation. n n n n n n n n n n n Fully Differential Input and Output Low Noise: 1.5nV/Hz RTI Very Low Distortion: LTC6404-1 (2VP-P , 10MHz): -91dBc LTC6404-2 (2VP-P , 10MHz): -96dBc LTC6404-4 (2VP-P , 10MHz): -101dBc Closed-Loop -3dB Bandwidth: 600MHz Slew Rate: 1200V/s (LTC6404-4) Adjustable Output Common Mode Voltage Rail-to-Rail Output Swing Input Range Extends to Ground Large Output Current: 85mA (Typ) DC Voltage Offset < 2mV (Max) Low Power Shutdown Tiny 3mm x 3mm x 0.75mm 16-Pin QFN Package APPLICATIONS n n n n Differential Input A/D Converter Driver Single-Ended to Differential Conversion/Amplification Common Mode Level Translation Low Voltage, Low Noise, Signal Processing The LTC6404-1 is unity-gain stable. The LTC6404-2 is designed for closed-loop gains greater than or equal to 2V/V. The LTC6404-4 is designed for closed-loop gains greater than or equal to 4V/V. The LTC6404 closed-loop bandwidth extends from DC to 600MHz. In addition to the normal unfiltered outputs (OUT+ and OUT-), the LTC6404 has a built-in 88.5MHz differential single-pole lowpass filter and an additional pair of filtered outputs (OUTF+, OUTF-). An input referred voltage noise of 1.5nV/Hz make the LTC6404 able to drive state-of-the-art 16-/18-bit ADCs while operating on the same supply voltage, saving system cost and power. The LTC6404 is characterized, and maintains its performance for supplies as low as 2.7V and can operate on supplies up to 5.25V. It draws only 27.3mA, and has a hardware shutdown feature which reduces current consumption to 250A. The LTC6404 family is available in a compact 3mm x 3mm 16-pin leadless QFN package and operates over a -40C to 125C temperature range. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION LTC6404-4 Distortion vs Frequency Single-Ended Input to Differential Output with Common Mode Level Shifting -40 0.5VP-P -50 0V -60 100 50 402 3V 0.1F 71.5 SIGNAL GENERATOR HD2, HD3 (dBc) VS 1VP-P + 1.5VDC 1.5VDC VOCM 0.1F 130 - 1.5VDC 402 1VP-P 6404 TA01 VCM = VOCM = MID-SUPPLY VS = 3V VOUT = 2VP-P RI = 100, RF = 402 DIFFERENTIAL INPUT SINGLE-ENDED INPUT -70 -80 -90 HD2 -100 HD2 -110 -120 -130 0.1 HD3 HD3 1 10 FREQUENCY (MHz) 100 64044 G16 6404f 1 LTC6404 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) OUTF- OUT- IN+ NC TOP VIEW 16 15 14 13 2 V- 3 VOCM 4 12 V- 11 V+ 17 10 V+ 9 5 6 7 8 OUTF+ V+ OUT+ 1 NC SHDN IN- Total Supply Voltage (V+ to V-) ................................5.5V Input Voltage: IN+, IN-, VOCM, SHDN (Note 2) ...................... V+ to V- Input Current: IN+, IN-, VOCM, SHDN (Note 2) ........................10mA Output Short-Circuit Duration (Note 3) ............ Indefinite Output Current (Continuous): (OUTF+, OUTF-) DC + ACRMS ...........................40mA Operating Temperature Range (Note 4).. -40C to 125C Specified Temperature Range (Note 5) .. -40C to 125C Junction Temperature ........................................... 150C Storage Temperature Range................... -65C to 150C V- UD PACKAGE 16-LEAD (3mm s 3mm) PLASTIC QFN TJMAX = 150C, JA = 68C/W, JC = 4.2C/W EXPOSED PAD (PIN 17) IS V-, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LTC6404CUD-1#PBF LTC6404CUD-1#TRPBF LCLW 16-Lead (3mm x 3mm) Plastic QFN 0C to 70C LTC6404IUD-1#PBF LTC6404IUD-1#TRPBF LCLW 16-Lead (3mm x 3mm) Plastic QFN -40C to 85C LTC6404HUD-1#PBF LTC6404HUD-1#TRPBF LCLW 16-Lead (3mm x 3mm) Plastic QFN -40C to 125C LTC6404CUD-2#PBF LTC6404CUD-2#TRPBF LCLX 16-Lead (3mm x 3mm) Plastic QFN 0C to 70C LTC6404IUD-2#PBF LTC6404IUD-2#TRPBF LCLX 16-Lead (3mm x 3mm) Plastic QFN -40C to 85C LTC6404HUD-2#PBF LTC6404HUD-2#TRPBF LCLX 16-Lead (3mm x 3mm) Plastic QFN -40C to 125C LTC6404CUD-4#PBF LTC6404CUD-4#TRPBF LCLY 16-Lead (3mm x 3mm) Plastic QFN 0C to 70C LTC6404IUD-4#PBF LTC6404IUD-4#TRPBF LCLY 16-Lead (3mm x 3mm) Plastic QFN -40C to 85C LTC6404HUD-4#PBF LTC6404HUD-4#TRPBF LCLY 16-Lead (3mm x 3mm) Plastic QFN -40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 6404f 2 LTC6404 LTC6404 DC ELECTRICAL CHARACTERISTICS +The l denotes the specifications which apply over - the full operating temperature range, otherwise specifications are at TA = 25C. V = 3V, V = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RL = OPEN, RBAL = 100k (See Figure 1). For the LTC6404-1: RI = 100, RF = 100. For the LTC6404-2: RI = 100, RF = 200. For the LTC6404-4: RI = 100, RF = 402, unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined (VIN+ + VIN-)/2. VOUTDIFF is defined (VOUT+ - VOUT-). VINDIFF = (VINP - VINM) SYMBOL VOSDIFF PARAMETER Differential Offset Voltage (Input Referred) VOSDIFF/T Differential Offset Voltage Drift (Input Referred) Input Bias Current (Note 6) IB Input Bias Current Drift (Note 6) IB/T CONDITIONS VS = 2.7V to 5.25V VS = 2.7V to 5.25V MIN TYP 0.5 1 MAX 2 UNITS mV V/C -60 -23 0.01 0 A A/C 1 1000 3 1 1.5 3 10 A k k pF nV/Hz pA/Hz l VS = 2.7V to 5.25V VS = 2.7V to 5.25V l VS = 2.7V to 5.25V Common Mode Differential Mode l IOS RIN Input Offset Current (Note 6) Input Resistance CIN en in enVOCM Input Capacitance Differential Input Referred Noise Voltage Density Input Noise Current Density Input Referred Common Mode Noise Voltage Density VICMR (Note 7) CMRRI (Note 8) Input Signal Common Mode Range Input Common Mode Rejection Ratio (Input Referred) VICM/VOSDIFF VS = 3V, VCM = 0.75V VS = 5V, VCM = 1.25V 60 60 nV/Hz nV/Hz nV/Hz V V dB dB CMRRIO (Note 8) PSRR (Note 9) PSRRCM (Note 9) Output Common Mode Rejection Ratio (Input Referred) VOCM/VOSDIFF Differential Power Supply Rejection (VS/VOSDIFF) Output Common Mode Power Supply Rejection (VS/VOSCM) VS = 5V, VOCM = 1V 66 dB GCM BAL VOSCM f = 1MHz f = 1MHz f = 1MHz, Referred to VOCM Pin LTC6404-1 LTC6404-2 LTC6404-4 VS = 3V VS = 5V 9 10.5 27 l l 0 0 1.6 3.6 VS = 2.7V to 5.25V l 60 94 dB VS = 2.7V to 5.25V LTC6404-1 LTC6404-2 LTC6404-4 l l l 50 50 40 63 63 51 dB dB dB Common Mode Gain (VOUTCM/VOCM) VS = 5V, VOCM = 1V LTC6404-1 LTC6404-2 LTC6404-4 l l l 1 1 0.99 V/V V/V V/V Common Mode Gain Error VS = 5V, VOCM = 1V LTC6404-1 LTC6404-2 LTC6404-4 l l l VOUTDIFF = 2V, Single-Ended Input LTC6404-1 LTC6404-2 LTC6404-4 Output Balance (VOUTCM/VOUTDIFF) Common Mode Offset Voltage (VOUTCM - VOCM) VOUTDIFF = 2V, Differential Input LTC6404-1 LTC6404-2 LTC6404-4 VS = 2.7V to 5.25V LTC6404-1 LTC6404-2 LTC6404-4 -0.6 -0.6 -1.6 -0.125 -0.25 -1 0.1 0.1 -0.4 % % % l l l -60 -60 -53 -40 -40 -40 dB dB dB l l l -66 -66 -66 -40 -40 -40 dB dB dB l l l 10 20 40 25 50 100 mV mV mV 6404f 3 LTC6404 LTC6404 DC ELECTRICAL CHARACTERISTICS +The l denotes the specifications which apply over - the full operating temperature range, otherwise specifications are at TA = 25C. V = 3V, V = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RL = OPEN, RBAL = 100k (See Figure 1). For the LTC6404-1: RI = 100, RF = 100. For the LTC6404-2: RI = 100, RF = 200. For the LTC6404-4: RI = 100, RF = 402, unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined (VIN+ + VIN-)/2. VOUTDIFF is defined (VOUT+ - VOUT-). VINDIFF = (VINP - VINM) SYMBOL VOSCM/T PARAMETER Common Mode Offset Voltage Drift VOUTCMR (Note 7) Output Signal Common Mode Range (Voltage Range for the VOCM Pin) RINVOCM Input Resistance, VOCM Pin VMID VOUT Voltage at the VOCM Pin Output Voltage High, Either Output Pin (Note 10) Output Voltage Low, Either Output Pin (Note 10) ISC Output Short-Circuit Current, Either Output Pin (Note 11) AVOL VS IS Large-Signal Voltage Gain Supply Voltage Range Supply Current (LTC6404-1) Supply Current (LTC6404-2) Supply Current (LTC6404-4) ISHDN Supply Current in Shutdown (LTC6404-1) Supply Current in Shutdown (LTC6404-2) Supply Current in Shutdown (LTC6404-4) CONDITIONS VS = 2.7V to 5.25V LTC6404-1 LTC6404-2 LTC6404-4 VS = 3V LTC6404-1 LTC6404-2 LTC6404-4 VS = 5V LTC6404-1 LTC6404-2 LTC6404-4 LTC6404-1 LTC6404-2 LTC6404-4 VS = 3V VS = 3V, IL = 0mA VS = 3V, IL = 5mA VS = 3V, IL = 20mA VS = 5V, IL = 0mA VS = 5V, IL = 5mA VS = 5V, IL = 20mA VS = 3V, IL = 0mA VS = 3V, IL = -5mA VS = 3V, IL = -20mA VS = 5V, IL = 0mA VS = 5V, IL = -5mA VS = 5V, IL = -20mA VS = 2.7V VS = 3V VS = 5V VS = 3V VS = 2.7V, VSHDN = VS - 0.6V VS = 3V, VSHDN = VS - 0.6V VS = 5V, VSHDN = VS - 0.6V VS = 2.7V, VSHDN = VS - 0.6V VS = 3V, VSHDN = VS - 0.6V VS = 5V, VSHDN = VS - 0.6V VS = 2.7V, VSHDN = VS - 0.6V VS = 3V, VSHDN = VS - 0.6V VS = 5V, VSHDN = VS - 0.6V VS = 2.7V, VSHDN = VS - 2.1V VS = 3V, VSHDN = VS - 2.1V VS = 5V, VSHDN = VS - 2.1V VS = 2.7V, VSHDN = VS - 2.1V VS = 3V, VSHDN = VS - 2.1V VS = 5V, VSHDN = VS - 2.1V VS = 2.7V, VSHDN = VS - 2.1V VS = 3V, VSHDN = VS - 2.1V VS = 5V, VSHDN = VS - 2.1V MIN TYP MAX 10 20 20 UNITS V/C V/C V/C l l l 1.1 1.1 1.1 2 2 1.7 V V V l l l 4 4 3.7 32 20 10 V V V l l l 1.1 1.1 1.1 15 8 4 l 1.45 l l l l l l l l l l l l l l l 35 40 55 l 2.7 l l l l l l l l l l l l l l l l l l 23.5 14 7 1.5 325 360 480 460 500 650 120 140 200 175 200 285 60 65 85 90 27.2 27.3 27.8 29.7 29.8 30.4 30.0 30.2 31.0 0.22 0.25 0.35 0.22 0.25 0.35 0.28 0.30 0.50 1.55 550 600 750 700 750 1000 230 260 350 320 350 550 5.25 35.5 35.5 36.5 38.5 38.5 39.5 39 39 40 1 1 2 1 1 2 1.2 1.2 2.4 k k k V mV mV mV mV mV mV mV mV mV mV mV mV mA mA mA dB V mA mA mA mA mA mA mA mA mA mA mA mA mA mA mA mA mA mA 6404f 4 LTC6404 LTC6404 DC ELECTRICAL CHARACTERISTICS +The l denotes the specifications which apply over - the full operating temperature range, otherwise specifications are at TA = 25C. V = 3V, V = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RL = OPEN, RBAL = 100k (See Figure 1). For the LTC6404-1: RI = 100, RF = 100. For the LTC6404-2: RI = 100, RF = 200. For the LTC6404-4: RI = 100, RF = 402, unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined (VIN+ + VIN-)/2. VOUTDIFF is defined (VOUT+ - VOUT-). VINDIFF = (VINP - VINM) SYMBOL VIL VIH RSHDN tON tOFF PARAMETER SHDN Input Logic Low SHDN Input Logic High SHDN Pin Input Impedance Turn-On Time Turn-Off Time CONDITIONS VS = 2.7V to 5V VS = 2.7V to 5V VS = 5V, VSHDN = 2.9V to 0V VS = 3V, VSHDN = 0.5V to 3V VS = 3V, VSHDN = 3V to 0.5V MIN TYP MAX V+ - 2.1 66 750 300 94 l l l V+ - 0.6 38 UNITS V V k ns ns LTC6404-1 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V+ = 3V, V- = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RI = 100, RF = 100, RL = 200 (See Figure 2) unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined as (VIN+ + VIN-)/2. VOUTDIFF is defined as (VOUT+ - VOUT-). VINDIFF = (VINP - VINM). SYMBOL SR GBW PARAMETER Slew Rate Gain-Bandwidth Product f3dB HDSEIN -3dB Frequency (See Figure 2) 10MHz Distortion HDDIFFIN IMD10M OIP310M tS NF f3dBFILTER 10MHz Distortion Third-Order IMD at 10MHz f1 = 9.5MHz, f2 = 10.5MHz OIP3 at 10MHz (Note 12) Settling Time 2V Step at Output Noise Figure, RS = 50 Differential Filter 3dB Bandwidth (Note 13) CONDITIONS VS = 3V to 5V VS = 3V to 5V, RI = 100, RF = 499, fTEST = 500MHz VS = 3V to 5V VS = 3V, VOUTDIFF = 2VP-P Single-Ended Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P Differential Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P 1% Settling 0.1% Settling 0.01% Settling f = 10MHz l MIN TYP 450 500 MAX UNITS V/s MHz 300 600 MHz -88 -91 dBc dBc -102 -91 -93 dBc dBc dBc 50 10 13 17 13.4 dBm ns ns ns dB 88.5 MHz 6404f 5 LTC6404 LTC6404-2 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V+ = 3V, V- = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RI = 100, RF = 200, RL = 200 (See Figure 2) unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined as (VIN+ + VIN-)/2. VOUTDIFF is defined as (VOUT+ - VOUT-). VINDIFF = (VINP - VINM). SYMBOL SR GBW PARAMETER Slew Rate Gain-Bandwidth Product f3dB HDSEIN -3dB Frequency (See Figure 2) 10MHz Distortion HDDIFFIN IMD10M OIP310M tS NF f3dBFILTER 10MHz Distortion Third-Order IMD at 10MHz f1 = 9.5MHz, f2 = 10.5MHz OIP3 at 10MHz (Note 12) Settling Time 2V Step at Output Noise Figure, RS = 50 Differential Filter 3dB Bandwidth (Note 13) CONDITIONS VS = 3V to 5V VS = 3V to 5V, RI = 100, RF = 499, fTEST = 500MHz VS = 3V to 5V VS = 3V, VOUTDIFF = 2VP-P Single-Ended Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P Differential Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P l MIN TYP 700 900 300 600 MHz -95 -96 dBc dBc -98 -99 -100 dBc dBc dBc 53 9 12 15 10 88.5 dBm ns ns ns dB MHz 1% Settling 0.1% Settling 0.01% Settling f = 10MHz MAX UNITS V/s MHz LTC6404-4 AC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V+ = 3V, V- = 0V, VCM = VOCM = VICM = Mid-Supply, VSHDN = OPEN, RI = 100, RF = 402, RL = 200 (See Figure 2) unless otherwise noted. VS is defined (V+ - V-). VOUTCM = (VOUT+ + VOUT-)/2. VICM is defined as (VIN+ + VIN-)/2. VOUTDIFF is defined as (VOUT+ - VOUT-). VINDIFF = (VINP - VINM). SYMBOL SR GBW PARAMETER Slew Rate Gain-Bandwidth Product f3dB HDSEIN -3dB Frequency (See Figure 2) 10MHz Distortion HDDIFFIN IMD10M OIP310M tS NF f3dBFILTER 10MHz Distortion Third-Order IMD at 10MHz f1 = 9.5MHz, f2 = 10.5MHz OIP3 at 10MHz (Note 12) Settling Time 2V Step at Output Noise Figure, RS = 50 Differential Filter 3dB Bandwidth (Note 13) CONDITIONS VS = 3V to 5V VS = 3V to 5V, RI = 100, RF = 499, fTEST = 500MHz VS = 3V to 5V VS = 3V, VOUTDIFF = 2VP-P Single-Ended Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P Differential Input 2nd Harmonic 3rd Harmonic VS = 3V, VOUTDIFF = 2VP-P 1% Settling 0.1% Settling 0.01% Settling f = 10MHz l MIN TYP 1200 1700 MAX UNITS V/s MHz 300 530 MHz -97 -98 dBc dBc -100 -101 -101 dBc dBc dBc 54 8 11 14 8 88.5 dBm ns ns ns dB MHz 6404f 6 LTC6404 ELECTRICAL CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The inputs IN+, IN- are protected by a pair of back-to-back diodes. If the differential input voltage exceeds 1.4V, the input current should be limited to less than 10mA. Input pins (IN+, IN-, VOCM and SHDN) are also protected by steering diodes to either supply. If the inputs should exceed either supply voltage, the input current should be limited to less than 10mA. Note 3: A heat sink may be required to keep the junction temperature below the absolute maximum rating when the output is shorted indefinitely. Long-term application of output currents in excess of the absolute maximum ratings may impair the life of the device. Note 4: The LTC6404C/LTC6404I are guaranteed functional over the operating temperature range -40C to 85C. The LTC6404H is guaranteed functional over the operating temperature range -40C to 125C. Note 5: The LTC6404C is guaranteed to meet specified performance from 0C to 70C. The LTC6404C is designed, characterized, and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LTC6404I is guaranteed to meet specified performance from -40C to 85C. The LTC6404H is guaranteed to meet specified performance from -40C to 125C. Note 6: Input bias current is defined as the average of the input currents flowing into Pin 6 and Pin 15 (IN- and IN+). Input offset current is defined as the difference of the input currents flowing into Pin 15 and Pin 6 (IOS = IB+ - IB-) Note 7: Input common mode range is tested using the test circuit of Figure 1 by measuring the differential gain with a 1V differential output with VICM = mid-supply, and with VICM at the input common mode range limits listed in the Electrical Characteristics table, verifying the differential gain has not deviated from the mid-supply common mode input case by more than 1%, and the common mode offset (VOSCM) has not deviated from the zero bias common mode offset by more than 15mV (LTC6404-1), 20mV (LTC6404-2) or 40mV (LTC6404-4). The voltage range for the output common mode range is tested using the test circuit of Figure 1 by applying a voltage on the VOCM pin and testing at both mid-supply and at the Electrical Characteristics table limits to verify that the the common mode offset (VOSCM) has not deviated by more than 15mV (LTC6404-1), 20mV (LTC6404-2) or 40mV (LTC6404-4). Note 8: Input CMRR is defined as the ratio of the change in the input common mode voltage at the pins IN+ or IN- to the change in differential input referred voltage offset. Output CMRR is defined as the ratio of the change in the voltage at the VOCM pin to the change in differential input referred voltage offset. These specifications are strongly dependent on feedback ratio matching between the two outputs and their respective inputs, and is difficult to measure actual amplifier performance. (See "The Effects of Resistor Pair Mismatch" in the Applications Information section of this data sheet. For a better indicator of actual amplifier performance independent of feedback component matching, refer to the PSRR specification. Note 9: Differential power supply rejection (PSRR) is defined as the ratio of the change in supply voltage to the change in differential input referred voltage offset. Common mode power supply rejection (PSRRCM) is defined as the ratio of the change in supply voltage to the change in the common mode offset, VOUTCM - VOCM. Note 10: This parameter is pulse tested. Output swings are measured as differences between the output and the respective power supply rail. Note 11: This parameter is pulse tested. Extended operation with the output shorted may cause junction temperatures to exceed the 125C limit and is not recommended. See Note 3 for more details. Note 12: Since the LTC6404 is a voltage feedback amplifier with low output impedance, a resistive load is not required when driving an ADC. Therefore, typical output power is very small. In order to compare the LTC6404 with amplifiers that require 50 output loads, output swing of the LTC6404 driving an ADC is converted into an "effective" OIP3 as if the LTC6404 were driving a 50 load. Note 13: The capacitors used to set the filter pole might have up to 15% variation. The resistors used to set the filter pole might have up to 12% variation. 6404f 7 LTC6404 LTC6404-1 TYPICAL PERFORMANCE CHARACTERISTICS Active Supply Current vs Temperature 30 Shutdown Supply Current vs Temperature 29 VCM = VOCM = MID-SUPPLY 0.6 VS = 5V 27 26 0.4 VOSDIFF (mV) VS = 2.7V ICC (mA) VS = 3V 0.3 VS = 3V 0.2 0.2 0 -0.2 -0.4 VS = 2.7V -0.6 0.1 25 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V 0.8 0.4 VS = 5V 28 ICC (mA) 1.0 0.5 VCM = VOCM = MID-SUPPLY Differential Voltage Offset (Input Referred) vs Temperature -0.8 24 -75 -50 -25 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 64041 G01 6 SHDN Supply Current vs Supply Voltage and Temperature 0.5 30 VCM = VOCM = MID-SUPPLY + 25 SHDN = V 4 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 0.4 20 ICC (mA) 2 0 -2 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 15 10 -4 -6 5 -8 -10 -75 -50 -25 0 0 0 25 50 75 100 125 150 TEMPERATURE (C) ICC (mA) VOSCM (mV) 64041 G03 Active Supply Current vs Supply Voltage and Temperature 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V 8 0 25 50 75 100 125 150 TEMPERATURE (C) 64041 G02 Common Mode Voltage Offset vs Temperature 10 -1.0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 1 3 2 VSUPPLY (V) 4 0.3 0.2 0.1 VCM = VOCM = MID-SUPPLY SHDN = V- 0 0 5 1 2 3 VSUPPLY (V) 64041 G05 4 5 64041 G06 64041 G04 30 VCM = VOCM = MID-SUPPLY VS = 3V -5 25 -10 20 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C -15 -20 -25 -30 0 0.5 1.5 2.5 1.0 2.0 SHDN PIN VOLTAGE (V) 3.0 64041 G07 ICC (mA) SHDN PIN CURRENT (A) 0 Supply Current vs SHDN Pin Voltage and Temperature Small-Signal Frequency Response 5 VCM = VOCM = MID-SUPPLY VS = 3V 0 GAIN (dB) SHDN Pin Current vs SHDN Pin Voltage and Temperature TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 15 10 5 0 0 0.5 1.0 1.5 2.0 2.5 SHDN PIN VOLTAGE (V) 3.0 VS = 3V VS = 5V CF = 0pF CF = 1.8pF -5 -10 -15 UNFILTERED OUTPUTS VCM = VOCM = MID-SUPPLY TA = 25C RF = RI = 100, CF IN PARALLEL WITH RF -20 10 100 1000 FREQUENCY (MHz) 64041 G08 64041 G09 6404f 8 LTC6404 LTC6404-1 TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Frequency Response vs Gain Setting Resistor Values and Supply Voltage 5 10 0 5 Small-Signal Frequency Response vs Temperature 10 CLOAD = 10pF TA = -45C 5 RF = RI = 100 0 GAIN (dB) RF = RI = 200 -10 RF = RI = 499 -15 VS = 3V VS = 5V -20 UNFILTERED OUTPUTS -25 VCM = VOCM = MID-SUPPLY TA = 25C VS = 3V AND VS = 5V -30 10 100 FREQUENCY (MHz) 1000 0 CLOAD = 5pF CLOAD = 0pF -5 UNFILTERED OUTPUTS -10 VCM = VOCM = MID-SUPPLY TA = 25C RF = RI = 100 -15 VS = 3V AND VS = 5V RLOAD = 200, (EACH OUTPUT TO GROUND) -20 10 100 FREQUENCY (MHz) 1000 Large-Signal Step Response TA = 25C FILTERED DIFFERENTIAL OUTPUT -10 -15 TA = 90C -20 TA = 25C TA = -45C -25 FILTERED OUTPUT = MID-SUPPLY V =V -30 RCM= R =OCM F I 100 VS = 3V AND VS = 5V -35 10 100 FREQUENCY (MHz) 1.0 0.5 VINDIFF VOUTDIFF 0 -0.5 VCM = VOCM = MID-SUPPLY RF = RI = 100 -1.5 1000 0 VOUTDIFF 0 -0.25 3 6 9 TIME (ns) 12 0 15 Distortion vs Input Common Mode Voltage -80 -90 HD2 HD3 -100 VS = 3V RF = RI = 100 -50 V = 2V IN P-P fIN = 10MHz -60 DIFFERENTIAL INPUT SINGLE-ENDED -70 INPUT -80 -100 -110 HD3 -120 0.1 -110 1.0 10 FREQUENCY (MHz) HD2 -90 HD2 100 64041 G16 9 6 TIME (ns) 12 Distortion vs Output Amplitude VCM = VOCM = MID-SUPPLY -40 VS = 3V TA = 25oC C = 0pF -50 F RF = RI = 1007 V = FULLY DIFFERENTIAL INPUT -60 IN fIN = 10MHz -70 -80 HD3 -90 HD2 HD3 15 -30 HD2, HD3 (dBc) DIFFERENTIAL INPUT SINGLE-ENDED INPUT HD2, HD3 (dBc) -70 3 64041 G15 -40 -60 VCM = VOCM = MID-SUPPLY RF = RI = 100 -0.50 64041 G14 -40 VCM = VOCM = MID-SUPPLY VS = 3V VOUTDIFF = 2VP-P RF = RI = 100 VINDIFF 0.25 -1.0 Distortion vs Frequency HD2, HD3 (dBc) Small-Signal Step Response 0.50 64041 G13 -50 1000 64041 G12 VOUTDIFF (OUT+ - OUT-) (V) GAIN (dB) -5 UNFILTERED OUTPUTS -15 VCM = VOCM = MID-SUPPLY RF = RI = 100 VS = 3V AND VS = 5V -20 10 100 FREQUENCY (MHz) 1.5 VOUTDIFF (OUT+ - OUT-) (V) 0 TA = 90C 64041 G11 Small-Signal Frequency Response vs Temperature UNFILTERED DIFFERENTIAL OUTPUT TA = 25C -5 -10 64041 G10 5 GAIN (dB) -5 GAIN (dB) Small-Signal Frequency Response vs CLOAD HD2 -100 HD3 -110 0 0.5 1.0 1.5 2.0 2.5 3.0 DC COMMON MODE INPUT (AT IN+ AND IN- PINS) (V) 64041 G17 0 1 2 3 4 VOUTDIFF (VP-P) 5 6 64041 G18 6404f 9 LTC6404 LTC6404-1 TYPICAL PERFORMANCE CHARACTERISTICS VCM = VOCM = 1.7V VS = 3.3V RF = RI = 100 VIN = 2VP-P DIFFERENTIAL fSAMPLE = 105Msps 10MHz, 4092 POINT FFT FUNDAMENTAL = -1dBFS HD2 = -98.8dBc HD3 = -90.2dBc -20 -40 -70 -80 -60 HD2 -80 HD3 -100 0 VCM = VOCM = 1.5V VS = 3V RF = RI = 100 VIN = 2VP-P DIFFERENTIAL fSAMPLE = 105Msps 10MHz, 65536 POINT FFT FUNDAMENTAL = -1dBFS HD2 = -90.7dBc HD3 = -86.6dBc -20 -40 (dB) 0 VCM = VOCM = MID-SUPPLY -40 VS = 3V TA = 25C RF = RI = 100 -50 VIN = SINGLE-ENDED INPUT f = 10MHz -60 IN (dB) HD2, HD3 (dBc) -30 -60 -80 -90 -100 LTC6404-1 Driving LTC2207 16-Bit ADC LTC6404-1 Driving LTC2207 16-Bit ADC Distortion vs Output Amplitude HD9 HD2 HD3 HD7 HD5 HD2 -100 HD8 HD9 HD4 HD3 HD7 HD4 HD5 -120 -110 -120 0 1 2 3 VOUTDIFF (VP-P) 4 5 0 10 20 30 40 FREQUENCY (MHz) 64041 G19 NOISE FIGURE (dB) VOLTAGE NOISE DENSITY (nV/Hz) COMMON MODE 0.1 1 10 FREQUENCY (MHz) 20 30 40 FREQUENCY (MHz) 50 64041 G21 28 DIFFERENTIAL INPUT REFERRED 1 0.01 10 LTC6404-1 Noise Figure vs Frequency VCM = VOCM = MID-SUPPLY VS = 3V TA = 25C RF = RI = 100 10 0 64041 G20 Voltage Noise Density vs Frequency 100 50 VCM = VOCM = MID-SUPPLY V = 3V 24 T S = 25C A SEE FIGURE 2 CIRCUIT 20 16 12 8 4 100 1000 0 10 100 FREQUENCY (MHz) 1000 64041 G22 64041 G23 6404f 10 LTC6404 LTC6404-2 TYPICAL PERFORMANCE CHARACTERISTICS Active Supply Current vs Temperature 33 Shutdown Supply Current vs Temperature 1.0 0.5 VCM = VOCM = MID-SUPPLY 32 Differential Voltage Offset (Input Referred) vs Temperature VCM = VOCM = MID-SUPPLY 0.6 0.4 VS = 5V VS = 5V 0.4 30 VS = 2.7V VOSDIFF (mV) ICC (mA) ICC (mA) 31 VS = 3V 0.3 VS = 3V 0.2 0 -0.2 0.2 29 VS = 2.7V -0.4 -0.6 0.1 28 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V 0.8 -0.8 27 -75 -50 -25 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 64042 G01 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C VCM = VOCM = MID-SUPPLY SHDN = V+ 35 0.4 30 0 -2 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 20 15 -4 10 -6 5 -8 -10 -75 -50 -25 0 0 25 50 75 100 125 150 TEMPERATURE (C) 0 1 2 3 VSUPPLY (V) 4 64042 G03 0.1 0 5 10 -30 0 0.5 1.5 2.5 1.0 2.0 SHDN PIN VOLTAGE (V) 3.0 64042 G07 2 3 VSUPPLY (V) 4 5 64042 G06 CF = 0pF CF = 1pF 20 GAIN (dB) ICC (mA) VS = 3V VS = 5V 5 25 -10 -25 1 Small-Signal Frequency Response VCM = VOCM = MID-SUPPLY VS = 3V 30 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C VCM = VOCM = MID-SUPPLY SHDN = V- 0 15 35 -5 -20 0.2 Supply Current vs SHDN Pin Voltage and Temperature VCM = VOCM = MID-SUPPLY VS = 3V -15 0.3 64042 G05 SHDN Pin Current vs SHDN Pin Voltage and Temperature 0 ICC (mA) 25 2 ICC (mA) VOSCM (mV) SHDN Supply Current vs Supply Voltage and Temperature 0.5 40 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V 4 SHDN PIN CURRENT (A) 64042 G03 Active Supply Current vs Supply Voltage and Temperature 10 6 0 25 50 75 100 125 150 TEMPERATURE (C) 64042 G02 Common Mode Voltage Offset (Input Referred) vs Temperature 8 -1.0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 15 10 5 0 0 0.5 1.0 1.5 2.0 2.5 SHDN PIN VOLTAGE (V) 3.0 64042 G08 0 -5 -10 UNFILTERED OUTPUTS VCM = VOCM = MID-SUPPLY -15 TA = 25C RI = 100, RF = 200, CF IN PARALLEL WITH RF -20 10 100 FREQUENCY (MHz) 1000 64042 G09 6404f 11 LTC6404 LTC6404-2 TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Frequency Response vs CLOAD Small-Signal Frequency Response vs Gain Setting Resistor Values 25 RI = 100, RF = 200 CLOAD = 5pF 15 5 GAIN (dB) RI = 200, RF = 402 0 RI = 499, RF = 1k -5 VS = 3V VS = 5V -10 UNFILTERED OUTPUTS -20 VCM = VOCM = MID-SUPPLY TA = 25C VS = 3V AND VS = 5V -25 10 100 FREQUENCY (MHz) 1000 5 10 CLOAD = 0pF 5 UNFILTERED OUTPUTS VCM = VOCM = MID-SUPPLY T = 25C -5 RA = 100, R = 200 I F VS = 3V AND VS = 5V -10 R LOAD = 200, (EACH OUTPUT TO GROUND) -15 10 100 FREQUENCY (MHz) 0 1000 64042 G10 FILTERED GAIN (dB) 0 FILTERED DIFFERENTIAL OUTPUT -10 TA = 90C TA = 25C -15 TA = -45C -20 VCM = VOCM = MID-SUPPLY -25 RI = 100, RF = 200 VS = 3V -30 10 100 FREQUENCY (MHz) VINDIFF 0 -0.5 -1.0 VCM = VOCM = MID-SUPPLY RI = 100, RF = 200 -1.5 0 1000 6 9 TIME (ns) 3 12 HD2 -100 -110 -120 -130 -140 0.1 HD3 -0.50 -0.75 VCM = VOCM = MID-SUPPLY RI = 100, RF = 200 -1.00 0 3 9 6 TIME (ns) -80 HD2 -100 -110 64042 G16 15 64042 G15 Distortion vs Output Amplitude VS = 3V -50 VCM = VOCM = MID-SUPPLY RI = 100, RF = 200 -60 VIN = DIFFERENTIAL INPUT fIN = 10MHz HD3 100 12 -40 VS = 3V VCM = VOCM = MID-SUPPLY -50 R = 100, R = 200 I F VIN = 1VP-P -60 fIN = 10MHz DIFFERENTIAL INPUT SINGLE-ENDED INPUT -70 -90 HD2 HD3 1 10 FREQUENCY (MHz) -0.25 HD2, HD3 (dBc) DIFFERENTIAL INPUT SINGLE-ENDED INPUT VINDIFF 0 -40 HD2, HD3 (dBc) HD2, HD3 (dBc) -90 0.25 Distortion vs Input Common Mode Voltage VCM = VOCM = MID-SUPPLY VS = 3V VOUTDIFF = 2VP-P RF = 100, RI = 200 -80 15 VOUTDIFF 0.50 64042 G14 -40 -70 0.75 0.5 Distortion vs Frequency -60 Small-Signal Step Response 1.0 64042 G13 -50 1000 1.00 VOUTDIFF TA = 25C -5 UNFILTERED OUTPUTS -5 VCM = VOCM = MID-SUPPLY TA = 25C RI = 100, RF = 200 -10 VS = 3V AND VS = 5V RLOAD = 200, (EACH OUTPUT TO GROUND) -15 10 100 FREQUENCY (MHz) Large-Signal Step Response UNFILTERED DIFFERENTIAL OUTPUT 5 TA = 90C 0 64042 G12 1.5 VOUTDIFF (OUT+ - OUT-) (V) 10 TA = 25C 64042 G11 Small-Signal Frequency Response vs Temperature 15 TA = -45C 10 VOUTDIFF (OUT+ - OUT-) (V) 10 15 CLOAD = 10pF 20 GAIN (dB) 15 GAIN (dB) Small-Signal Frequency Response vs Temperature -70 HD3 -80 HD2 -90 -100 -110 HD3 HD2 -120 0 0.5 1.0 1.5 2.0 2.5 DC COMMON MODE INPUT (AT IN+ AND IN- PINS) (V) 64042 G17 0 1 2 3 4 VOUTDIFF (VP-P) 5 6 64042 G18 6404f 12 LTC6404 LTC6404-2 TYPICAL PERFORMANCE CHARACTERISTICS 0 VS = 3.3V VOUTDIFF = 2VP-P VCM = VOCM = 1.25V RI = 1007, RF = 2007 10.1MHz, 16184 POINT FFT fSAMPLE = 105Msps FUNDAMENTAL = -1dBFS HD2 = -92.4dBc HD3 = -93.02dBc -20 -40 -70 (dB) HD2, HD3 (dBc) VS = 3V -50 VCM = VOCM = MID-SUPPLY RI = 100, RF = 200 -60 VIN = SINGLE-ENDED INPUT fIN = 10MHz -80 HD2 -60 HD2 HD3 HD7 -100 HD3 VS = 3.3V VINDIFF = 1VP-P FULLY DIFFERENTIAL VOUTDIFF = 2VP-P VCM = VOCM = 1.25V RI = 100, RF = 200 16184 POINT FFT fSAMPLE = 105Msps TONE1, TONE2 = -7dBFS IM3U IM3U = -106.8dBc IM3L = -107.7dBc -20 -40 -60 -80 IM3L -80 -100 -110 0 (dB) -40 -90 LTC6404-2 Driving LTC2207 16-Bit ADC (Two Tones) LTC6404-2 Driving LTC2207 16-Bit ADC (Single Tone) Distortion vs Output Amplitude HD4 HD5 -100 -120 -120 -120 2 3 4 VOUTDIFF (VP-P) 5 6 0 10 20 30 40 FREQUENCY (MHz) 50 64042 G19 Voltage Noise Density vs Frequency 100 28 24 COMMON MODE 10 DIFFERENTIAL INPUT REFERRED 0.1 1 10 FREQUENCY (MHz) 10 20 30 40 FREQUENCY (MHz) 50 64042 G21 LTC6404-2 Noise Figure vs Frequency VS = 3V VCM = VOCM = MID-SUPPLY RI = 100, RF = 200 TA = 25C 1 0.01 0 64042 G20 NOISE FIGURE (dB) 1 VOLTAGE NOISE DENSITY (nV/Hz) 0 VCM = VOCM = MID-SUPPLY VS = 3V TA = 25C SEE FIGURE 2 CIRCUIT 20 16 12 8 4 100 1000 0 10 100 FREQUENCY (MHz) 1000 64042 G22 64042 G23 6404f 13 LTC6404 LTC6404-4 TYPICAL PERFORMANCE CHARACTERISTICS Active Supply Current vs Temperature 33 Shutdown Supply Current vs Temperature Differential Voltage Offset (Input Referred) vs Temperature 1.0 0.7 VCM = VOCM = MID-SUPPLY VCM = VOCM = MID-SUPPLY 32 0.6 VS = 5V VS = 5V 0.5 30 VS = 2.7V 0.4 VOSDIFF (mV) VS = 3V ICC (mA) 0.4 VS = 3V 0.3 VS = 2.7V 29 0.2 -0.4 0.1 27 -75 -50 -25 -0.8 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 40 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V SHDN Supply Current vs Supply Voltage and Temperature 0.7 VCM = VOCM = MID-SUPPLY SHDN = V+ 35 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 0.6 30 20 0.5 25 10 ICC (mA) VOSCM (mV) 64044 G03 Active Supply Current vs Supply Voltage and Temperature 50 30 0 -10 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 20 15 -20 10 -30 5 -40 -50 -75 -50 -25 0 0 25 50 75 100 125 150 TEMPERATURE (C) 1 0 2 3 VSUPPLY (V) 4 0.3 0.2 0.1 VCM = VOCM = MID-SUPPLY SHDN = V+ 0 1 0 2 3 4 64044 G06 Supply Current vs SHDN Pin Voltage and Temperature 35 VCM = VOCM = MID-SUPPLY VS = 3V Small-Signal Frequency Response 20 VCM = VOCM = MID-SUPPLY VS = 3V 30 5 VSUPPLY (V) 64044 G05 SHDN Pin Current vs SHDN Pin Voltage and Temperature -5 0.4 5 64044 G04 0 0 25 50 75 100 125 150 TEMPERATURE (C) 64044 G02 Common Mode Voltage Offset (Input Referred) vs Temperature 40 -1.0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C) 64044 G01 VS = 3V VS = 5V 15 25 CF = 0pF 10 -10 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C -15 -20 -25 0 0.5 1.0 1.5 2.0 SHDN PIN VOLTAGE (V) 2.5 3.0 64044 G07 20 GAIN (dB) CF = 1pF ICC (mA) SHDN PIN CURRENT (A) 0 -0.6 28 -30 0.2 -0.2 ICC (mA) ICC (mA) 31 5 REPRESENTATIVE UNITS VCM = VOCM = MID-SUPPLY VS = 3V 0.8 0.6 TA = 125C TA = 105C TA = 90C TA = 75C TA = 50C TA = 25C TA = -10C TA = -45C TA = -60C 15 10 5 5 0 -5 -10 -15 0 0 0.5 2.0 1.5 2.5 1.0 SHDN PIN VOLTAGE (V) 3.0 64044 G08 VCM = VOCM = MID-SUPPLY RI = 100, RF = 402, CF IN PARALLEL WITH RF 10 100 FREQUENCY (MHz) 1000 64044 G09 6404f 14 LTC6404 LTC6404-4 TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Frequency Response vs CLOAD Small-Signal Frequency Response vs Gain Setting Resistor Values 20 CLOAD = 10pF 20 15 RI = 200, RF = 800 0 VS = 3V VS = 5V VCM = VOCM = MID-SUPPLY VS = 3V AND VS = 5V CLOAD = 0pF 5 0 VS = 3V VS = 5V VCM = VOCM = MID-SUPPLY RI = 100, RF = 402 VS = 3V AND VS = 5V -5 -10 -15 100 FREQUENCY (MHz) 1000 10 100 FREQUENCY (MHz) TA = 25C TA = -45C TA = 90C -15 VCM = VOCM = MID-SUPPLY -20 RI = 100, RF = 402 VS = 3V -25 100 10 FREQUENCY (MHz) VOUTDIFF VOUTDIFF 1.5 1.0 VINDIFF 0.5 0 -0.5 -1.5 VCM = VOCM = MID-SUPPLY VS = 3V RI = 100, RF = 402 -2.0 -2.5 1000 VCM = VOCM = MID-SUPPLY VS = 3V VOUT = 2VP-P RI = 100, RF = 402 3 0 9 6 TIME (ns) -80 -90 HD2 -100 -130 0.1 HD3 12 VCM = VOCM = MID-SUPPLY VS = 3V RI = 100, RF = 402 -0.50 -0.75 0 15 3 -70 DIFFERENTIAL INPUT SINGLE-ENDED INPUT HD2 -90 -60 VCM = VOCM = MID-SUPPLY VS = 3V RI = 100, RF = 402 fIN = 10MHz -70 DIFFERENTIAL INPUT SINGLE-ENDED INPUT -50 -80 -80 HD3 HD3 -90 HD2 -100 HD2 -110 1 10 FREQUENCY (MHz) 100 64044 G16 15 12 Distortion vs Output Amplitude -40 -100 HD3 6 9 TIME (ns) 64044 G15 HD3 HD2 -110 -120 -60 VCM = VOCM = MID-SUPPLY VS = 3V RI = 100, RF = 402 fIN = 10MHz -50 HD2, HD3 (dBc) HD2, HD3 (dBc) -40 DIFFERENTIAL INPUT SINGLE-ENDED INPUT VINDIFF 0 Distortion vs Input Common Mode Voltage -40 -70 0.25 64044 G14 Distortion vs Frequency -60 0.50 -0.25 -1.0 64044 G13 -50 Small-Signal Step Response VOUTDIFF (OUT+ - OUT-) (V) VOUTDIFF (OUT+ - OUT-) (V) FILTERED GAIN (dB) FILTERED DIFFERENTIAL OUTPUT 1000 0.75 2.0 5 -10 TA = 90C 0 Large-Signal Step Response 10 -5 TA = 25C 64044 G12 2.5 UNFILTERED DIFFERENTIAL OUTPUT AT 25C 0 5 64044 G11 Small-Signal Frequency Response vs Temperature 15 TA = -45C VCM = VOCM = MID-SUPPLY -10 R = 100, R = 402 I F VS = 3V AND VS = 5V -15 10 100 FREQUENCY (MHz) 1000 64044 G10 20 10 -5 HD2, HD3 (dBc) 10 10 GAIN (dB) GAIN (dB) GAIN (dB) RI = 140, RF = 562 5 -15 15 CLOAD = 5pF 15 10 -10 20 25 RI = 100, RF = 402 -5 Small-Signal Frequency Response vs Temperature HD3 HD2 -110 -120 0.5 1.0 2.0 2.5 0 1.5 DC COMMON MODE INPUT (AT IN+ AND IN- PINS) (V) 64044 G17 -120 0 1 2 4 3 VOUTDIFF (VP-P) 5 6 64044 G18 6404f 15 LTC6404 LTC6404-4 TYPICAL PERFORMANCE CHARACTERISTICS LTC6404-4 Driving LTC2207 16-Bit ADC (Two Tones) LTC6404-4 Driving LTC2207 16-Bit ADC (Single Tone) 0 -40 -60 -80 VS = 3.3V VOUTDIFF = 2VP-P VCM = VOCM = 1.4V RI = 100, RF = 402 64k POINT FFT fSAMPLE = 105Msps 9.5MHz, 10.5MHz = -7dBFS IMD3L = -100.8dBc IMD3U = -102dBc -20 AMPLITUDE (dBFS) -20 AMPLITUDE (dBFS) 0 VS = 3.3V VOUTDIFF = 2VP-P VCM = VOCM = 1.25V RI = 100, RF = 402 10.1MHz, 64k POINT FFT fSAMPLE = 105Msps FUNDAMENTAL = -1dBFS HD2 = -98.9dBc HD3 = -99.6dBc -100 -120 -40 -60 -80 IMD3L IMD3U -100 -120 -140 -140 10 0 20 30 40 50 10 0 FREQUENCY (MHz) 20 30 40 64044 G19 64044 G20 LTC6404-4 Noise Figure vs Frequency Voltage Noise Density vs Frequency 28 VCM = VOCM = MID-SUPPLY VS = 3V RI = 100, RF = 402 TA = 25C COMMON MODE 10 DIFFERENTIAL INPUT REFERRED 0.1 1 10 FREQUENCY (MHz) 24 NOISE FIGURE (dB) VOLTAGE NOISE DENSITY (nV/Hz) 100 1 0.01 50 FREQUENCY (MHz) VCM = VOCM = MID-SUPPLY VS = 3V TA = 25C SEE FIGURE 2 CIRCUIT 20 16 12 8 4 100 1000 64044 G21 0 10 100 FREQUENCY (MHz) 1000 64044 G22 PIN FUNCTIONS SHDN (Pin 1): When SHDN is floating or directly tied to V+, the LTC6404 is in the normal (active) operating mode. When Pin 1 is pulled a minimum of 2.1V below V+, the LTC6404 enters into a low power shutdown state. See Applications Information for more details. V+, V- (Pins 2, 10, 11 and Pins 3, 9, 12): Power Supply Pins. Three pairs of power supply pins are provided to keep the power supply inductance as low as possible to prevent degradation of amplifier 2nd harmonic performance. See the Layout Considerations section for more detail. VOCM (Pin 4): Output Common Mode Reference Voltage. The voltage on VOCM sets the output common mode voltage level (which is defined as the average of the voltages on the OUT+ and OUT- pins). The VOCM pin is the midpoint of an internal resistive voltage divider between the supplies, developing a (default) mid-supply voltage potential to maximize output signal swing. In general, the VOCM pin can be overdriven by an external voltage reference capable of driving the input impedance presented by the VOCM pin. On the LTC6404-1, the VOCM pin has a input resistance of approximately 23.5k to a mid-supply 6404f 16 LTC6404 PIN FUNCTIONS potential. On the LTC6404-2, the VOCM pin has a input resistance of approximately 14k. On the LTC6404-4, the VOCM pin has a input resistance of approximately 7k. The VOCM pin should be bypassed with a high quality ceramic bypass capacitor of at least 0.01F, (unless you are using split supplies, then connect directly to a low impedance, low noise ground plane) to minimize common mode noise from being converted to differential noise by impedance mismatches both externally and internally to the IC. that the continuous (DC + ACRMS) output current be limited to under 50mA. OUTF+, OUTF- (Pins 8, 13): Filtered Output Pins. These pins have a series 50 resistor connected between the filtered and unfiltered outputs and three 12pF capacitors. Both OUTF+ and OUTF- have 12pF to V-, plus an additional 12pF differentially between OUTF+ and OUTF-. This filter creates a differential lowpass frequency response with a -3dB bandwidth of 88.5MHz. For long-term device reliability, it is recommended that the continuous (DC + ACRMS) output current be limited to under 40mA. NC (Pins 5, 16): No Connection. These pins are not connected internally. OUT+, OUT- (Pins 7, 14): Unfiltered Output Pins. Besides driving the feedback network, each pin can drive an additional 50 to ground with typical short-circuit current limiting of 65mA. Each amplifier output is designed to drive a load capacitance of 10pF. This basically means the amplifier can drive 10pF from each output to ground or 5pF differentially. Larger capacitive loads should be decoupled with at least 25 resistors in series with each output. For long-term device reliability, it is recommended IN+, IN- (Pins 15, 6): Noninverting and Inverting Input Pins of the Amplifier, Respectively. For best performance, it is highly recommended that stray capacitance be kept to an absolute minimum by keeping printed circuit connections as short as possible, and if necessary, stripping back nearby surrounding ground plane away from these pins. Exposed Pad (Pin 17): Tie the pad to V- (Pins 3, 9, and 12). If split supplies are used, do not tie the pad to ground. BLOCK DIAGRAM 16 15 NC V+ 14 IN+ V- V- 1 V+ 2 50 2 * RVOCM V- V- V+ VOCM 2 * RVOCM 12pF V+ 50 - 12pF V- 4 V- 12 V- V+ 11 + VOCM V- 3 V+ 12pF V+ V+ V+ 66k SHDN OUTF- V- V+ V+ 13 OUT- V+ 10 V- V- 9 V- V- V- V+ V- 5 NC 6 IN- V+ V+ 7 OUT+ 8 OUTF+ 6404 BD IC 2 * RVOCM 47k LTC6404-1 28k LTC6404-2 14k LTC6404-4 6404f 17 LTC6404 APPLICATIONS INFORMATION VIN+ RI IL VOUT- RF + VOUTF- VINP - 16 NC 15 14 IN+ OUT- 13 SHDN 12pF SHDN VSHDN 50 V+ V+ 2 0.1F + 3 12pF V+ VOCM V- V- - V- VOCM 0.1F VOUTCM 0.1F 10 V- 12pF V- 0.1F 5 NC VINM 6 IN- VIN- RI 7 OUT+ VOUT+ RF 0.1F OUTF+ 8 RBAL V- 9 0.01F 0.1F V+ V+ 4 + RBAL V- V- V+ 11 50 VOCM - V- 12 1 V+ VCM OUTF- LTC6404 VOUTF+ IL 6404 F01 Figure 1. DC Test Circuit 0.01F RI VIN+ VOUT- RF 100 0.01F VOUTF- 16 NC 15 IN+ 14 OUT- 13 SHDN VIN - * * VSHDN 1 50 V+ V+ V+ 2 0.1F V- + V- V- 4 5 RI NC 6 VIN- IN- RF 7 OUT+ VOUT+ 8 50 0.1F V- 0.1F V- 0.1F OUTF+ VOUTF+ 0.1F MINI-CIRCUITS TCM4-19 V+ 9 0.01F 0.01F 0.1F V+ 10 50 12pF V- V- V + 11 V+ - V- 3 12pF VOCM VOCM VOCM V- 12 * + 12pF SHDN * 50 MINI-CIRCUITS TCM4-19 OUTF- LTC6404 100 0.01F 6404 F02 Figure 2. AC Test Circuit (-3dB BW testing) 6404f 18 LTC6404 APPLICATIONS INFORMATION Functional Description The LTC6404 is a small outline, wide band, low noise, and low distortion fully-differential amplifier with accurate output phase balancing. The LTC6404 is optimized to drive low voltage, single-supply, differential input 14-bit to 18-bit analog-to-digital converters (ADCs). The LTC6404's output is capable of swinging rail-to-rail on supplies as low as 2.7V, which makes the amplifier ideal for converting ground referenced, single-ended signals into DC level-shifted differential signals in preparation for driving low voltage, single-supply, differential input ADCs. Unlike traditional op amps which have a single output, the LTC6404 has two outputs to process signals differentially. This allows for two times the signal swing in low voltage systems when compared to single-ended output amplifiers. The balanced differential nature of the amplifier also provides even-order harmonic distortion cancellation, and less susceptibility to common mode noise (e.g., power supply noise). The LTC6404 can be used as a single-ended input to differential output amplifier, or as a differential input to differential output amplifier. The LTC6404's output common mode voltage, defined as the average of the two output voltages, is independent of the input common mode voltage, and is adjusted by applying a voltage on the VOCM pin. If the pin is left open, there is an internal resistive voltage divider that develops a potential halfway between the V+ and V- pins. Whenever this pin is not hard tied to a low impedance ground plane, it is recommended that a high quality ceramic capacitor is used to bypass the VOCM pin to a low impedance ground plane (See Layout Considerations in this document). The LTC6404's internal common mode feedback path forces accurate output phase balancing to reduce even order harmonics, and centers each individual output about the potential set by the VOCM pin. VOUTCM = VOCM = VOUT + + VOUT - 2 The outputs (OUT+ and OUT-) of the LTC6404 are capable of swinging rail-to-rail. They can source or sink up to approximately 65mA of current. Additional outputs (OUTF+ and OUTF-) are available that provide filtered versions of the OUT+ and OUT- outputs. An on-chip single pole RC passive filter band limits the filtered outputs to a -3dB frequency of 88.5MHz. The user has a choice of using the unfiltered outputs, the filtered outputs, or modifying the filtered outputs to adjust the frequency response by adding additional components. In applications where the full bandwidth of the LTC6404 is desired, the unfiltered outputs (OUT+ and OUT-) should be used. The unfiltered outputs OUT+ and OUT- are designed to drive 10pF to ground (or 5pF differentially). Capacitances greater than 10pF will produce excess peaking, and can be mitigated by placing at least 25 in series with each output pin. Input Pin Protection The LTC6404's input stage is protected against differential input voltages which exceed 1.4V by two pairs of backto-back diodes connected in anti-parallel series between IN+ and IN- (Pins 6 and 15). In addition, the input pins have steering diodes to either power supply. If the input pair is overdriven, the current should be limited to under 10mA to prevent damage to the IC. The LTC6404 also has steering diodes to either power supply on the VOCM and SHDN pins (Pins 4 and 1), and if forced to voltages which exceed either supply, they too, should be current-limited to under 10mA. SHDN Pin If the SHDN pin (Pin 1) is pulled 2.1V below the positive supply, circuitry is activated which powers down the LTC6404. The pin will have the Thevenin equivalent impedance of approximately 66k to V+. If the pin is left unconnected, an internal pull-up resistor of 150k will keep the part in normal active operation. Care should be taken to control leakage currents at this pin to under 1A to prevent inadvertently putting the LTC6404 into shutdown. In shutdown, all biasing current sources are shut off, and the output pins, OUT+ and OUT-, will each appear as open collectors with a non-linear capacitor in parallel and steering diodes to either supply. Because of the non-linear capacitance, the outputs still have the ability to sink and source small amounts of transient current if driven by significant voltage transients. The inputs (IN+, and IN-) appear as anti-parallel diodes which can conduct 6404f 19 LTC6404 APPLICATIONS INFORMATION if voltage transients at the input exceed 1.4V. The inputs also have steering diodes to either supply. The turn-on and turn-off time between the shutdown and active states is typically less than 1s. of single ended signals to differential output signals to drive differential input ADCs. Effects of Resistor Pair Mismatch In the circuit of Figure 3, it is possible the gain setting resistors will not perfectly match. Assuming infinite open loop gain, the differential output relationship is given by the equation: General Amplifier Applications As levels of integration have increased and correspondingly, system supply voltages decreased, there has been a need for ADCs to process signals differentially in order to maintain good signal to noise ratios. These ADCs are typically supplied from a single supply voltage which can be as low as 3V (2.7V min), and will have an optimal common mode input range near mid-supply. The LTC6404 makes interfacing to these ADCs easy, by providing both single-ended to differential conversion as well as common mode level shifting. The front page of this data sheet shows a typical application. Referring to Figure 1, the gain to VOUTDIFF from VINM and VINP is: VOUTDIFF = VOUT + - VOUT - VOUTDIFF = VOUT + - VOUT - * VINCM - *V AVG AVG OCM where: RI2 1 RI1 AVG = * + 2 RI1 + RF1 RI2 + RF 2 RF is the average of RF1, and RF2, and RI is the average of RI1, and RI2. RF * ( VINP - VINM ) RI AVG is defined as the average feedback factor (or gain) from the outputs to their respective inputs: Note from the above equation, the differential output voltage (VOUT+ - VOUT-) is completely independent of input and output common mode voltages, or the voltage at the common mode pin. This makes the LTC6404 ideally suited for pre-amplification, level shifting and conversion RI2 is defined as the difference in feedback factors: = RI2 RI1 - RI2 + RF 2 RI1 + RF1 RF2 VOUT- VOUTF- + VINP 16 - NC 15 IN+ 14 OUT- 13 SHDN OUTF- LTC6404 V- 12 SHDN VSHDN 1 V- V+ 11 V+ V+ 2 0.1F V- V+ + 3 V+ VOCM V- V- VOCM VVOCM - VINM + V- 0.1F 4 0.1F 0.1F V- V- 9 0.01F 5 RI1 NC 6 IN- RF1 7 OUT+ 8 0.1F OUTF+ VOUTF+ 0.1F V+ V+ 10 - V- RF *V + RI INDIFF 6404 F03 VOUT+ Figure 3. Basic Differential Amplifier with Feedback Resistor Pair Mismatch 6404f 20 LTC6404 APPLICATIONS INFORMATION VINCM is defined as the average of the two input voltages VINP, and VINM (also called the source-referred input common mode voltage): 1 VINCM = * ( VINP + VINM ) 2 and VINDIFF is defined as the difference of the input voltages: VINDIFF = VINP - VINM When the feedback ratios mismatch (), common mode to differential conversion occurs. Setting the differential input to zero (VINDIFF = 0), the degree of common mode to differential conversion is given by the equation: VOUTDIFF = VOUT+ - VOUT - ( VINCM - VOCM ) * AVG VINDIFF = 0 In general, the degree of feedback pair mismatch is a source of common mode to differential conversion of both signals and noise. Using 1% resistors or better will mitigate most problems, and will provide about 34dB worst-case of common mode rejection. Using 0.1% resistors will provide about 54dB of common mode rejection. A low impedance ground plane should be used as a reference for both the input signal source, and the VOCM pin. A direct short of VOCM to this ground or bypassing the VOCM with a high quality 0.1F ceramic capacitor to this ground plane, will further prevent common mode signals from being converted to differential. There may be concern on how feedback ratio mismatch affects distortion. Distortion caused by feedback ratio mismatch using 1% resistors or better is negligible. However, in single supply level shifting applications where there is a voltage difference between the input common mode voltage and the output common mode voltage, resistor mismatch can make the apparent voltage offset of the amplifier appear higher than specified. The apparent input referred offset induced by feedback ratio mismatch is derived from the following equation: VOSDIFF(APPARENT) (VICM - VOCM) * Using the LTC6404-1 in a single supply application on a single 5V supply with 1% resistors, and the input common mode grounded, with the VOCM pin biased at mid-supply, the worst-case DC offset can induce 25mV of apparent offset voltage. With 0.1% resistors, the worst case apparent offset reduces to 2.5mV. Input Impedance and Loading Effects The input impedance looking into the VINP or VINM input of Figure 1 depends on whether the sources VINP and VINM are fully differential. For balanced input sources (VINP = -VINM), the input impedance seen at either input is simply: RINP = RINM = RI For single ended inputs, because of the signal imbalance at the input, the input impedance increases over the balanced differential case. The input impedance looking into either input is: RINP = RINM = RI 1 RF 1- 2 * R + R I F Input signal sources with non-zero output impedances can also cause feedback imbalance between the pair of feedback networks. For the best performance, it is recommended that the source's output impedance be compensated for. If input impedance matching is required by the source, R1 should be chosen (see Figure 4): R1 = RINM * RS RINM - RS RINM RS VS RI RF R1 R1 CHOSEN SO THAT R1 || RINM = RS R2 CHOSEN TO BALANCE R1 || RS RI - + + - RF 6404 F04 R2 = RS || R1 Figure 4. Optimal Compensation for Signal Source Impedance 6404f 21 LTC6404 APPLICATIONS INFORMATION With singled ended inputs, there is an input signal component to the input common mode voltage. Applying only VINP (setting VINM to zero), the input common voltage is approximately: According to Figure 4, the input impedance looking into the differential amp (RINM) reflects the single ended source case, thus: RINM = RI 1 RF 1- 2 * R + R I F VICM = RF VINP VCM * + 2 RF + RI R2 is chosen to balance R1 || RS: R2 = RI * RS RI + RS RF * RF + RI Output Common Mode Voltage Range The output common mode voltage is defined as the average of the two outputs: Input Common Mode Voltage Range The LTC6404's input common mode voltage (VICM) is defined as the average of the two input voltages, VIN+, and VIN-. It extends from V- to 1.4V below V+. The operating input common mode range depends on the circuit configuration (gain), VOCM and VCM (Refer to Figure 5). For fully differential input applications, where VINP = -VINM, the common mode input voltage is approximately: VICM = RI VIN+ + VIN- VOCM * + 2 RI + RF VOUTCM = VOCM = VOUT + + VOUT - 2 The VOCM pin sets this average by an internal common mode feedback loop which internally forces VOUT+ = -VOUT-. The output common mode range extends from 1.1V above V- to 1V below V+ (see the Electrical Characteristics table for the LTC6404-4 output common mode voltage range). The VOCM pin sits in the middle of a voltage divider which sets the default mid-supply open circuit potential. RI VIN+ + VIN- VOCM * + 2 RI + RF RF VCM * RF + RI RI RF VOUT- VOUTF- + VINP 16 - NC 15 IN+ 14 OUT- 13 SHDN OUTF- LTC6404 V- 12 SHDN VSHDN 1 V- V+ V+ VCM 0.1F V- V+ 2 + 3 V+ VOCM V- V- V- VOCM VVOCM - 4 0.01F 5 NC 6 IN- RI RF 7 OUT+ 8 0.1F V+ 0.1F 0.1F V- 9 VINM + 0.1F V+ 10 - V- V+ 11 V- 0.1F OUTF+ 6404 F05 VOUTF+ VOUT+ Figure 5. Circuit for Common Mode Range 6404f 22 LTC6404 APPLICATIONS INFORMATION In single supply applications, where the LTC6404 is used to interface to an ADC, the optimal common mode input range to the ADC is often determined by the ADC's reference. If the ADC makes a reference available for setting the input common mode voltage, it can be directly tied to the VOCM pin, but must be capable of driving the input impedance presented by the VOCM as listed in the Electrical Characteristics Table. This impedance can be assumed to be connected to a mid-supply potential. If an external reference drives the VOCM pin, it should still be bypassed with a high quality 0.01F or larger capacitor to a low impedance ground plane to filter any thermal noise and to prevent common mode signals on this pin from being inadvertently converted to differential signals. Output Filter Considerations and Use Filtering at the output of the LTC6404 is often desired to provide either anti-aliasing or improved signal to noise ratio. To simplify this filtering, the LTC6404 includes an additional pair of differential outputs (OUTF+ and OUTF-) which incorporate an internal lowpass filter network with a -3dB bandwidth of 88.5MHz (Figure 6). These pins each have a DC output impedance of 50. Internal capacitances are 12pF to V- on each filtered output, plus an additional 12pF capacitor connected differentially between the two filtered outputs. This resistor/capacitor combination creates filtered outputs that look like a series 50 resistor with a 36pF capacitor shunting each filtered output to AC ground, providing a -3dB bandwidth of 88.5MHz, and a noise bandwidth of 139MHz. The filter cutoff frequency is easily modified with just a few external components. To increase the cutoff frequency, simply add 2 equal value resistors, one between OUT+ and OUTF+ and the other between OUT- and OUTF- (Figure 7). These resistors, in parallel with the internal 50 resistor, lower the overall resistance and therefore increase filter bandwidth. For example, to double the filter bandwidth, add two external 50 resistors to lower the series filter resistance to 25. The 36pF of capacitance remains unchanged, so filter bandwidth doubles. Keep in mind, the series resistance also serves to decouple the outputs from load capacitance. The unfiltered outputs of the LTC6404 are designed to drive 10pF to ground or 5pF differentially, so care should be taken to not lower the effective impedance between OUT+ and OUTF+ or OUT- and OUTF- below 25. To decrease filter bandwidth, add two external capacitors, one from OUTF+ to ground, and the other from OUTF- to ground. A single differential capacitor connected between OUTF+ and OUTF- can also be used, but since it is being driven differentially it will appear at each filtered output as a single-ended capacitance of twice the value. To halve the filter bandwidth, for example, two 36pF capacitors could be added (one from each filtered output to ground). Alternatively, one 18pF capacitor could be added between the filtered outputs, again halving the filter bandwidth. Combinations of capacitors could be used as well; a three 49.9 LTC6404 LTC6404 14 OUT- 13 OUT- 13 50 OUTF- 12pF OUTF- 12pF V- 12 50 V- 12 V- + V- + FILTERED OUTPUT (88.5MHz) 12pF - 14 - 50 - 12pF V V- 50 - 12pF V V- 9 9 7 OUT+ FILTERED OUTPUT (176MHz) 12pF 8 OUTF+ 7 OUT+ 8 OUTF+ 6404 F07 49.9 6404 F06 Figure 6. LTC6404 Internal Filter Topology Figure 7. LTC6404 Filter Topology Modified for 2x Filter Bandwidth (2 External Resistors) 6404f 23 LTC6404 APPLICATIONS INFORMATION capacitor solution of 12pF from each filtered output to ground plus a 12pF capacitor between the filtered outputs would also halve the filter bandwidth (Figure 8). LTC6404 14 OUT- 13 OUTF- Noise Considerations The LTC6404's input referred voltage noise is on the order of 1.5nV/Hz. Its input referred current noise is on the order of 3pA/Hz. In addition to the noise generated by the amplifier, the surrounding feedback resistors also contribute noise. A noise model is shown in Figure 9. The output noise generated by both the amplifier and the feedback components is governed by the equation: 12pF 12pF V- 12 50 V- 2 + 12pF - RF 2 eni * 1+ R + 2 * (In * RF ) + I FILTERED OUTPUT (44.25MHz) 12pF eno = 50 - 12pF V V- 12pF 2 R 2 * enRI * F + 2 * enRF 2 RI 9 7 OUT+ 8 OUTF+ 6404 F08 A plot of this equation, and a plot of the noise generated by the feedback components for the LTC6404 is shown in Figure 10. Figure 8. LTC6404 Filter Topology Modified for 1/2x Filter Bandwidth (3 External Capacitors) enRI22 RI2 RF2 enRF22 in+2 16 NC 15 14 IN+ OUT- 13 SHDN OUTF- LTC6404 V- 12 SHDN 1 V- V+ 11 V+ V+ V+ 2 + V- 3 V+ VOCM V- V+ enof2 eno2 V- V- 2 encm V+ 10 - V- V- VOCM 4 9 NC 5 6 IN- 7 OUT+ 8 V- OUTF+ 6404 F09 in-2 eni2 enRI12 RI1 RF1 enRF12 Figure 9. Noise Model of the LTC6404 6404f 24 LTC6404 APPLICATIONS INFORMATION Layout Considerations 100 TOTAL (AMPLIFIER AND FEEDBACK NETWORK) OUTPUT NOISE nV/Hz 10 FEEDBACK RESISTOR NETWORK NOISE ALONE 1 0.1 10 100 1k 10k RF = RI () 6404 F10 Figure 10. LTC6404-1 Output Spot Noise vs Spot Noise Contributed by Feedback Network Alone The LTC6404's input referred voltage noise contributes the equivalent noise of a 140 resistor. When the feedback network is comprised of resistors whose values are less than this, the LTC6404's output noise is voltage noise dominant (See Figure 10.): R eno eni * 1+ F RI Because the LTC6404 is a very high speed amplifier, it is sensitive to both stray capacitance and stray inductance. Three pairs of power supply pins are provided to keep the power supply inductance as low as possible to prevent degradation of amplifier 2nd Harmonic performance. It is critical that close attention be paid to supply bypassing. For single supply applications (Pins 3, 9 and 12 grounded) it is recommended that 3 high quality 0.1F surface mount ceramic bypass capacitor be placed between pins 2 and 3, between pins 11and 12, and between pins10 and 9 with direct short connections. Pins 3, 9 and 10 should be tied directly to a low impedance ground plane with minimal routing. For dual (split) power supplies, it is recommended that at least two additional high quality, 0.1F ceramic capacitors are used to bypass pin V+ to ground and V- to ground, again with minimal routing. For driving large loads (<200), additional bypass capacitance may be needed for optimal performance. Keep in mind that small geometry (e.g. 0603) surface mount ceramic capacitors have a much higher self resonant frequency than do leaded capacitors, and perform best in high speed applications. Lower resistor values (<100) always result in lower noise at the penalty of increased distortion due to increased loading of the feedback network on the output. Higher resistor values (but still less than 400) will result in higher output noise, but improved distortion due to less loading on the output. The optimal feedback resistance for the LTC6404 runs between 100 to 400. Higher resistances are not recommended. Any stray parasitic capacitances to ground at the summing junctions IN+, and IN- should be kept to an absolute minimum even if it means stripping back the ground plane away from any trace attached to this node. This becomes especially true when the feedback resistor network uses resistor values >400 in circuits with RF = RI. Excessive peaking in the frequency response can be mitigated by adding small amounts of feedback capacitance (0.5pF to 2pF) around RF. Always keep in mind the differential nature of the LTC6404, and that it is critical that the load impedances seen by both outputs (stray or intended) should be as balanced and symmetric as possible. This will help preserve the natural balance of the LTC6404, which minimizes the generation of even order harmonics, and preserves the rejection of common mode signals and noise. The differential filtered outputs OUTF+ and OUTF- will have a little higher spot noise than the unfiltered outputs (due to the two 50 resistors which contribute 0.9nV/Hz each), but actually will provide superior Signal-to-Noise in noise bandwidths exceeding 139MHz due to the noise-filtering function the filter provides. It is highly recommended that the VOCM pin be either hard tied to a low impedance ground plane (in split supply applications), or bypassed to ground with a high quality ceramic capacitor whose value exceeds 0.01F. This will help stabilize the common mode feedback loop as well as prevent thermal noise from the internal voltage divider and Feedback networks consisting of resistors with values greater than about 200 will result in output noise which is resistor noise and amplifier current noise dominant. eno 2 * (In * RF )2 + 1+ RRF * 4 * k * T * RF I 6404f 25 LTC6404 APPLICATIONS INFORMATION other external sources of noise from being converted to differential noise due to divider mismatches in the feedback networks. It is also recommended that the resistive feedback networks be comprised of 1% resistors (or better) to enhance the output common mode rejection. This will also prevent VOCM referred common mode noise of the common mode amplifier path (which cannot be filtered) from being converted to differential noise, degrading the differential noise performance. Feedback factor mismatch has a weak effect on distortion. Using 1% or better resistors should prevent mismatch from impacting amplifier linearity. However, in single supply level shifting applications where there is a voltage difference between the input common mode voltage and the output common mode voltage, resistor mismatch can make the apparent voltage offset of the amplifier appear worse than specified. In general, the apparent input referred offset induced by feedback factor mismatch is given by the equation: VOSDIFF(APPARENT) (VINCM - VOCM) * where = RI2 RI1 - RI2 + RF 2 RI1 + RF1 VIN 2VP-P 100 16 NC 15 IN+ 14 OUT- 13 SHDN OUTF- LTC6404-1 V- 12 1 V- V+ 11 V+ V+ 2 0.1F + V+ VOCM V- 3 The LTC6404's rail-to-rail output and fast settling time make the LTC6404 ideal for interfacing to low voltage, single supply, differential input ADCs. The sampling process of ADCs create a sampling glitch caused by switching in the sampling capacitor on the ADC front end which momentarily "shorts" the output of the amplifier as charge is transferred between the amplifier and the sampling cap. The amplifier must recover and settle from this load transient before this acquisition period ends for a valid representation of the input signal. In general, the LTC6404 will settle much more quickly from these periodic load impulses than from a 2V input step, but it is a good idea to either use the filtered outputs to drive the ADC (Figure 11 shows an example of this), or to place a discrete R-C filter network between the differential unfiltered outputs of the LTC6404 and the input of the ADC to help absorb the charge transfer required during the ADC sampling process. The capacitance of the filter network serves as a charge reservoir to provide high frequency charging during the sampling process, while the two resistors of the filter network are used to dampen and attenuate any charge kickback from the ADC. The selection of the R-C time constant is trial and error for a given ADC, but the following guidelines are recommended: Choosing too large of a resistor in the decoupling network (leaving insufficient settling time) 100 SHDN 3.3V Interfacing the LTC6404 to A/D Converters V+ 10 - V- V- V- VOCM 4 CONTROL VCM 2.2F 0.1F LTC2207 3.3V 0.1F D15 * * D0 AIN+ AIN- GND 3.3V VDD 1F 1F 9 0.1F 5 NC 100 6 IN- 7 OUT+ 8 OUTF+ 6404 F11 100 Figure 11. Interfacing the LTC6404-1 to a High Speed 105Msps ADC 6404f 26 LTC6404 APPLICATIONS INFORMATION will create a voltage divider between the dynamic input impedance of the ADC and the decoupling resistors. Choosing too small of a resistor will possibly prevent the resistor from properly damping the load transient caused by the sampling process, prolonging the time required for settling. 16-bit applications typically require a minimum of 11 R-C time constants. It is recommended that the capacitor chosen have a high quality dielectric (for example, C0G multilayer ceramic). PACKAGE DESCRIPTION UD Package 16-Lead Plastic QFN (3mm x 3mm) (Reference LTC DWG # 05-08-1691) 0.70 0.05 3.50 0.05 1.45 0.05 2.10 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 0.10 (4 SIDES) BOTTOM VIEW--EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP OR 0.25 x 45 CHAMFER R = 0.115 TYP 0.75 0.05 15 16 PIN 1 TOP MARK (NOTE 6) 0.40 0.10 1 1.45 0.10 (4-SIDES) 2 (UD16) QFN 0904 0.200 REF 0.00 - 0.05 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.25 0.05 0.50 BSC 6404f 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. 27 LTC6404 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1809/LT1810 Single/Dual 180Mhz, 350V/s Rail-to-Rail Input and Output Low Distortion Op Amps 180MHz, 350V/s Slew Rate, Shutdown LTC1992/LTC1992-x Fully Differential Input/Output Amplifiers Programmable Gain or Fixed Gain (G = 1, 2, 5, 10) LT1994 Low Noise, Low Distortion Fully differential Input/Output Amplifier/Driver Low Distortion, 2VP-P, 1MHz: -94dBc, 13mA, Low Noise: 3nV/Hz LTC6400-20 1.8GHz Low Noise, Low Distortion, Differential ADC Driver AV = 20dB, 90mA Supply Current, IMD3 = -65dBc at 300MHz LTC6400-26 1.9GHz Low Noise, Low Distortion, Differential ADC Driver AV = 26dB, 85mA Supply Current, IMD3 = -71dBc at 300MHz LTC6401-8 2.2GHz Low Noise, Low Distortion, Differential ADC Driver AV = 8dB, 45mA Supply Current, IMD3 = -80dBc at 140MHz LTC6401-20 1.3GHz Low Noise, Low Distortion, Differential ADC Driver AV = 20dB, 50mA Supply Current, IMD3 = -74dBc at 140MHz LTC6401-26 1.6GHz Low Noise, Low Distortion, Differential ADC Driver AV = 26dB, 45mA Supply Current, IMD3 = -72dBc at 140MHz LT6402-12 300MHz Low Distortion, Low Noise Differential Amplifier/ADC AV = 4V/V, NF = 15dB, OIP3 = 43dBm at 20MHz Driver LTC6406 3GHz Low Noise, Rail-to-Rail Input Differential ADC Driver Low Noise: 1.6nV/Hz, Low Power: 18mA LT6600-2.5 Very Low Noise, Fully Differential Amplifier and 2.5MHz Filter 86dB S/N with 3V Supply, SO-8 Package LT6600-5 Very Low Noise, Fully Differential Amplifier and 5MHz Filter 82dB S/N with 3V Supply, SO-8 Package LT6600-10 Very Low Noise, Fully Differential Amplifier and 10MHz Filter 82dB S/N with 3V Supply, SO-8 Package LT6600-15 Very Low Noise, Fully Differential Amplifier and 15MHz Filter 76dB S/N with 3V Supply, SO-8 Package LT6600-20 Very Low Noise, Fully Differential Amplifier and 20MHz Filter 76dB S/N with 3V Supply, SO-8 Package LTC6403-1 200MHz Low Noise, Low Distortion Differential ADC Driver 10.8mA Supply Current, -95dB Distortion at 3MHz 6404f 28 Linear Technology Corporation LT 0608 * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2008