LT1993-2 800MHz Low Distortion, Low Noise Differential Amplifier/ ADC Driver (AV = 2V/V) DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®1993-2 is a low distortion, low noise Differential Amplifier/ADC driver for use in applications from DC to 800MHz. The LT1993-2 has been designed for ease of use, with minimal support circuitry required. Exceptionally low input-referred noise and low distortion products (with either single-ended or differential inputs) make the LT1993-2 an excellent solution for driving high speed 12bit and 14-bit ADCs. In addition to the normal unfiltered outputs (+OUT and –OUT), the LT1993-2 has a built-in 175MHz differential low pass filter and an additional pair of filtered outputs (+OUTFILTERED, –OUTFILTERED) to reduce external filtering components when driving high speed ADCs. The output common mode voltage is easily set via the VOCM pin, eliminating either an output transformer or AC-coupling capacitors in many applications. 800MHz –3dB Bandwidth Fixed Gain of 2V/V (6dB) Low Distortion: 38dBm OIP3, –70dBc HD3 (70MHz, 2VP-P) 51dBm OIP3, –94dBc HD3 (10MHz, 2VP-P) Low Noise: 12.3dB NF, en = 3.8nV/√Hz (70MHz) Differential Inputs and Outputs Additional Filtered Outputs Adjustable Output Common Mode Voltage DC- or AC-Coupled Operation Minimal Support Circuitry Required Small 0.75mm Tall 16-Lead 3 × 3 QFN Package U APPLICATIO S ■ ■ ■ ■ ■ ■ ■ Differential ADC Driver for: Imaging Communications Differential Driver/Receiver Single Ended to Differential Conversion Differential to Single Ended Conversion Level Shifting IF Sampling Receivers SAW Filter Interfacing/Buffering The LT1993-2 is designed to meet the demanding requirements of communications transceiver applications. It can be used as a differential ADC driver, a general-purpose differential gain block, or in any other application requiring differential drive. The LT1993-2 can be used in data acquisition systems required to function at frequencies down to DC. The LT1993-2 operates on a 5V supply and consumes 100mA. It comes in a compact 16-lead 3 × 3 QFN package and operates over a –40°C to 85°C temperature range. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO 4-Tone WCDMA Waveform, LT1993-2 Driving LTC2255 14-Bit ADC at 92.16Msps 4-Channel WCDMA Receive Channel –INB • • –INA 0.1µF MINI-CIRCUITS TCM4-19 0 32768 POINT FFT –10 TONE CENTER FREQUENCIES –20 AT 62.5MHz, 67.5MHz, 72.5MHz, 77.5MHz –30 0.1µF 12.2Ω –OUT –OUTFILTERED LT1993-2 +OUTFILTERED +INB +OUT +INA VOCM ENABLE 2.2V AIN– 82nH 52.3pF LTC2255 ADC AIN+ 12.2Ω LTC2255 125Msps 14-BIT ADC SAMPLING AT 92.16Msps 19932 TA01a AMPLITUDE (dBFS) 70MHz IF IN 1:4 Z-RATIO –40 –50 –60 –70 –80 –90 –100 –110 –120 0 5 10 15 20 25 30 35 FREQUENCY (MHz) 40 45 19932 TA01b 19932fa 1 LT1993-2 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) –INB –INA +INB +INA TOP VIEW 16 15 14 13 VCCC 1 12 VEEC VOCM 2 11 ENABLE 17 VCCA 3 10 VCCB VEEA 4 6 7 8 +OUT –OUTFILTERED –OUT 9 5 +OUTFILTERED Total Supply Voltage (VCCA/VCCB/VCCC to VEEA/VEEB/VEEC) ...................................................5.5V Input Current (+INA, –INA, +INB, –INB, VOCM, ENABLE)................................................±10mA Output Current (Continuous) (Note 6) +OUT, –OUT (DC) ..........................................±100mA (AC) ..........................................±100mA +OUTFILTERED, –OUTFILTERED (DC) .............±15mA (AC) .............±45mA Output Short Circuit Duration (Note 2) ............ Indefinite Operating Temperature Range (Note 3) ... –40°C to 85°C Specified Temperature Range (Note 4) .... –40°C to 85°C Storage Temperature Range................... –65°C to 125°C Junction Temperature ........................................... 125°C Lead Temperature Range (Soldering 10 sec) ........ 300°C VEEB UD PACKAGE 16-LEAD (3mm × 3mm) PLASTIC QFN TJMAX = 125°C, θJA = 68°C/W, θJC = 4.2°C/W EXPOSED PAD IS VEE (PIN 17) MUST BE SOLDERED TO THE PCB ORDER PART NUMBER UD PART MARKING* LT1993CUD-2 LT1993IUD-2 LBJG Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCCA = VCCB = VCCC = 5V, VEEA = VEEB = VEEC = 0V, ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), VOCM = 2.2V, Input common mode voltage = 2.2V, no RLOAD unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input/Output Characteristics (+INA, +INB, –INA, –INB, +OUT, –OUT, +OUTFILTERED, –OUTFILTERED) GDIFF Gain Differential (+OUT, –OUT), VIN = ±0.8V Differential ● 5.8 6.08 6.3 dB 0.25 0.35 0.5 V V VSWINGMIN Single-Ended +OUT, –OUT, +OUTFILTERED, –OUTFILTERED. VIN = ±2.2V Differential ● VSWINGMAX Single-Ended +OUT, –OUT, +OUTFILTERED, –OUTFILTERED. VIN = ±2.2V Differential 3.6 3.5 3.75 ● VSWINGDIFF Output Voltage Swing Differential (+OUT, –OUT), VIN = ±2.2V Differential 6.5 6 7 ● VP-P VP-P IOUT Output Current Drive (Note 5) ● ±40 ±45 mA VOS Input Offset Voltage –6.5 –10 1 ● TCVOS Input Offset Voltage Drift TMIN to TMAX ● IVRMIN Input Voltage Range, MIN Single-Ended ● IVRMAX Input Voltage Range, MAX Single-Ended ● 5.1 RINDIFF Differential Input Resistance ● 170 200 CINDIFF Differential Input Capacitance 1 pF CMRR Common Mode Rejection Ratio ● 45 70 dB Input Common Mode –0.1V to 5.1V V V 6.5 10 2.5 mV mV µV/°C –0.1 V V 240 Ω 19932fa 2 LT1993-2 DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCCA = VCCB = VCCC = 5V, VEEA = VEEB = VEEC = 0V, ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), VOCM = 2.2V, Input common mode voltage = 2.2V, no RLOAD unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS ROUTDIFF Output Resistance 0.3 Ω COUTDIFF Output Capacitance 0.8 pF Common Mode Voltage Control (VOCM Pin) GCM Common Mode Gain Differential (+OUT, –OUT), VOCM = 1.1V to 3.6V Differential (+OUT, –OUT), VOCM = 1.3V to 3.4V ● VOCMMIN Output Common Mode Voltage Adjustment Range, MIN Measured Single-Ended at +OUT and –OUT VOCMMAX Output Common Mode Voltage Adjustment Range, MAX Measured Single-Ended at +OUT and –OUT VOSCM Output Common Mode Offset Voltage Measured from VOCM to Average of +OUT and –OUT IBIASCM VOCM Input Bias Current ● RINCM VOCM Input Resistance ● CINCM VOCM Input Capacitance 0.9 0.9 1 ● ● 3.6 3.4 ● –30 0.8 1.1 1.1 V/V V/V 1.1 1.3 V V V V 4 30 mV 5 15 µA 3 MΩ 1 pF ENABLE Pin VIL ENABLE Input Low Voltage ● VIH ENABLE Input High Voltage ● IIL ENABLE Input Low Current ENABLE = 0.8V ● IIH ENABLE Input High Current ENABLE = 2V ● 0.8 V 2 V 0.5 µA 1 3 µA Power Supply ● 4 5 5.5 V ENABLE = 0.8V ● 88 100 112 mA Supply Current (Disabled) ENABLE = 2V ● 250 500 µA Power Supply Rejection Ratio 4V to 5.5V ● VS Operating Range IS Supply Current ISDISABLED PSRR 55 90 dB AC ELECTRICAL CHARACTERISTICS TA = 25°C, VCCA = VCCB = VCCC = 5V, VEEA = VEEB = VEEC = 0V, ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), VOCM = 2.2V, Input common mode voltage = 2.2V, no RLOAD unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP 500 MAX UNITS Input/Output Characteristics –3dBBW –3dB Bandwidth 200mVP-P Differential (+OUT, –OUT) 800 MHz 0.1dBBW Bandwidth for 0.1dB Flatness 200mVP-P Differential (+OUT, –OUT) 50 MHz 0.5dBBW Bandwidth for 0.5dB Flatness 200mVP-P Differential (+OUT, –OUT) 100 MHz SR Slew Rate 3.2VP-P Differential (+OUT, –OUT) 1100 V/µs ts1% 1% Settling Time 1% Settling for a 1VP-P Differential Step (+OUT, –OUT) tON tOFF 4 ns Turn-On Time 40 ns Turn-Off Time 250 ns Common Mode Voltage Control (VOCM Pin) –3dBBWCM Common Mode Small-Signal –3dB Bandwidth 0.1VP-P at VOCM, Measured Single-Ended at +OUT and –OUT 300 MHz SRCM Common Mode Slew Rate 1.3V to 3.4V Step at VOCM 500 V/µs 19932fa 3 LT1993-2 AC ELECTRICAL CHARACTERISTICS TA = 25°C, VCCA = VCCB = VCCC = 5V, VEEA = VEEB = VEEC = 0V, ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), VOCM = 2.2V, Input common mode voltage = 2.2V, no RLOAD unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Noise/Harmonic Performance Input/output Characteristics 1kHz Signal Second/Third Harmonic Distortion Third-Order IMD OIP31k Output Third-Order Intercept en1k Input Referred Noise Voltage Density 1dB Compression Point 2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –100 dBc 2VP-P Differential (+OUT, –OUT) –100 dBc 2VP-P Differential (+OUT, –OUT), RL = 100Ω –100 dBc 3.2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –91 dBc 3.2VP-P Differential (+OUT, –OUT) –91 dBc 3.2VP-P Differential (+OUT, –OUT), RL = 100Ω –91 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 0.95kHz, f2 = 1.05kHz –102 dBc 2VP-P Differential Composite (+OUT, –OUT), RL = 100Ω, f1 = 0.95kHz, f2 = 1.05kHz –102 dBc 3.2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 0.95kHz, f2 = 1.05kHz –93 dBc Differential (+OUTFILTERED, –OUTFILTERED), f1 = 0.95kHz, f2 = 1.05kHz 54 dBm 3.5 nV/√Hz RL = 100Ω 22.7 dBm 10MHz Signal Second/Third Harmonic Distortion Third-Order IMD 2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –94 dBc 2VP-P Differential (+OUT, –OUT) –94 dBc 2VP-P Differential (+OUT, –OUT), RL = 100Ω –86 dBc 3.2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –85 dBc 3.2VP-P Differential (+OUT, –OUT) –85 dBc 3.2VP-P Differential (+OUT, –OUT), RL = 100Ω –77 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 9.5MHz, f2 = 10.5MHz –96 dBc 2VP-P Differential Composite (+OUT, –OUT), RL = 100Ω, f1 = 9.5MHz, f2 = 10.5MHz –96 dBc 3.2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 9.5MHz, f2 = 10.5MHz –87 dBc 51 dBm OIP310M Output Third-Order Intercept Differential (+OUTFILTERED, –OUTFILTERED), f1 = 9.5MHz, f2 = 10.5MHz NF Noise Figure Measured Using DC800A Demo Board en10M Input Referred Noise Voltage Density 11.3 dB 3.5 nV/√Hz 1dB Compression Point RL = 100Ω 22.6 dBm Second/Third Harmonic Distortion 2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –77 dBc 2VP-P Differential (+OUT, –OUT) –77 dBc 2VP-P Differential (+OUT, –OUT), RL = 100Ω –74 dBc 3.2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –68 dBc 3.2VP-P Differential (+OUT, –OUT) –65 50MHz Signal dBc 19932fa 4 LT1993-2 AC ELECTRICAL CHARACTERISTICS TA = 25°C, VCCA = VCCB = VCCC = 5V, VEEA = VEEB = VEEC = 0V, ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), VOCM = 2.2V, Input common mode voltage = 2.2V, no RLOAD unless otherwise noted. SYMBOL PARAMETER Third-Order IMD CONDITIONS MIN TYP MAX UNITS 3.2VP-P Differential (+OUT, –OUT), RL = 100Ω –65 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 49.5MHz, f2 = 50.5MHz –84 dBc 2VP-P Differential Composite (+OUT, –OUT), RL = 100Ω, f1 = 49.5MHz, f2 = 50.5MHz –88 dBc 3.2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 49.5MHz, f2 = 50.5MHz –75 dBc 45 dBm OIP350M Output Third-Order Intercept Differential (+OUTFILTERED, –OUTFILTERED), f1 = 49.5MHz, f2 = 50.5MHz NF Noise Figure Measured Using DC800A Demo Board en50M Input Referred Noise Voltage Density 11.8 dB 3.65 nV/√Hz 1dB Compression Point RL = 100Ω 19.7 dBm Second/Third Harmonic Distortion 2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –70 dBc 2VP-P Differential (+OUT, –OUT) –61 dBc 2VP-P Differential (+OUT, –OUT), RL = 100Ω –61 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 69.5MHz, f2 = 70.5MHz –70 dBc 2VP-P Differential Composite (+OUT, –OUT), RL = 100Ω, f1 = 69.5MHz, f2 = 70.5MHz –72 dBc 38 dBm 70MHz Signal Third-Order IMD OIP370M Output Third-Order Intercept Differential (+OUTFILTERED, –OUTFILTERED), f1 = 69.5MHz, f2 = 70.5MHz NF Noise Figure Measured Using DC800A Demo Board 12.3 dB en70M Input Referred Noise Voltage Density 3.8 nV/√Hz 1dB Compression Point RL = 100Ω 18.5 dBm Second/Third Harmonic Distortion 2VP-P Differential (+OUTFILTERED, –OUTFILTERED) –56 dBc 2VP-P Differential (+OUT, –OUT) –54 dBc 100MHz Signal Third-Order IMD 2VP-P Differential (+OUT, –OUT), RL = 100Ω –51 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 99.5MHz, f2 = 100.5MHz –58 dBc 2VP-P Differential Composite (+OUT, –OUT), RL = 100Ω, f1 = 99.5MHz, f2 = 100.5MHz –59 dBc 32 dBm OIP3100M Output Third-Order Intercept Differential (+OUTFILTERED, –OUTFILTERED), f1 = 99.5MHz, f2 = 100.5MHz NF Noise Figure Measured Using DC800A Demo Board en100M Input Referred Noise Voltage Density 1dB Compression Point RL = 100Ω Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: As long as output current and junction temperature are kept below the Absolute Maximum Ratings, no damage to the part will occur. Note 3: The LT1993C-2 is guaranteed functional over the operating temperature range of –40°C to 85°C. Note 4: The LT1993C-2 is guaranteed to meet specified performance from 12.8 dB 4.1 nV/√Hz 17.8 dBm 0°C to 70°C. It is designed, characterized and expected to meet specified performance from –40°C and 85°C but is not tested or QA sampled at these temperatures. The LT1993I-2 is guaranteed to meet specified performance from –40°C to 85°C. Note 5: This parameter is pulse tested. Note 6: This parameter is guaranteed to meet specified performance through design and characterization. It has not been tested. 19932fa 5 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Frequency Response RLOAD = 400Ω Frequency Response vs CLOAD, RLOAD = 400Ω 12 21 9 Frequency Response RLOAD = 100Ω 12 VIN = 100mVP-P UNFILTERED OUTPUTS 18 9 UNFILTERED OUTPUTS UNFILTERED OUTPUTS 0 –3 V = 100mV IN P-P UNFILTERED: R = 400Ω –6 FILTERED: R LOAD LOAD = 350Ω (EXTERNAL) + –9 50Ω (INTERNAL, FILTERED OUTPUTS) –12 1 100 1000 10 FREQUENCY (MHz) 15 6 12 3 GAIN (dB) FILTERED OUTPUTS 3 GAIN (dB) 9 6 3 0pF 2pF 5pF 10pF 0 –3 10000 1 10 100 1000 FREQUENCY (MHz) 19932 G01 –3 V = 100mV IN P-P UNFILTERED: R = 100Ω –6 FILTERED: R LOAD LOAD = 50Ω (EXTERNAL) + –9 50Ω (INTERNAL, FILTERED OUTPUTS) –12 1 100 1000 10 FREQUENCY (MHz) Third Order Intermodulation Distortion vs Frequency Differential Input, RLOAD = 100Ω –10 –10 –10 –30 –30 –30 –50 –60 FILTERED OUTPUTS –70 2 TONES, 2VP-P COMPOSITE –20 1MHz TONE SPACING 2 TONES, 2VP-P COMPOSITE –20 1MHz TONE SPACING THIRD ORDER IMD (dBc) 2 TONES, 2VP-P COMPOSITE –20 1MHz TONE SPACING –80 UNFILTERED OUTPUTS –40 –50 –60 FILTERED OUTPUTS –70 –80 UNFILTERED OUTPUTS –40 –50 –60 –100 –100 –100 –110 –110 20 40 60 80 100 FREQUENCY (MHz) 120 140 –110 0 20 40 60 80 100 FREQUENCY (MHz) 19932 G04 60 40 FILTERED OUTPUTS 35 45 UNFILTERED OUTPUTS 40 35 FILTERED OUTPUTS UNFILTERED OUTPUTS 40 25 25 25 40 60 80 100 FREQUENCY (MHz) 120 140 19932 G07 20 20 0 20 40 60 80 100 FREQUENCY (MHz) 120 140 19932 G08 FILTERED OUTPUTS 35 30 20 140 45 30 0 120 50 30 20 40 60 80 100 FREQUENCY (MHz) 2 TONES, 2VP-P COMPOSITE 1MHz TONE SPACING 55 OUTPUT IP3 (dBm) OUTPUT IP3 (dBm) OUTPUT IP3 (dBm) 60 50 UNFILTERED OUTPUTS 20 Output Third Order Intercept vs Frequency, Differential Input, RLOAD = 100Ω 2 TONES, 2VP-P COMPOSITE 1MHz TONE SPACING 55 50 45 0 19932 G06 Output Third Order Intercept vs Frequency, Differential Input, RLOAD = 400Ω 2 TONES, 2VP-P COMPOSITE 1MHz TONE SPACING 55 140 19932 G05 Output Third Order Intercept vs Frequency, Differential Input, No RLOAD 60 120 UNFILTERED OUTPUTS –80 –90 0 FILTERED OUTPUTS –70 –90 –90 10000 19932 G02 Third Order Intermodulation Distortion vs Frequency Differential Input, RLOAD = 400Ω –40 FILTERED OUTPUTS 0 19932 G03 Third Order Intermodulation Distortion vs Frequency Differential Input, No RLOAD THIRD ORDER IMD (dBc) 10000 THIRD ORDER IMD (dBc) GAIN (dB) 6 0 20 40 60 80 100 FREQUENCY (MHz) 120 140 19932 G09 19932fa 6 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Distortion (Filtered) vs Frequency Differential Input, RLOAD = 400Ω Distortion (Filtered) vs Frequency Differential Input, No RLOAD –10 –10 –10 –30 –30 –30 –40 –40 –40 DISTORTION (dBc) DISTORTION (dBc) HD3 –50 –60 HD2 –70 –80 FILTERED OUTPUTS –20 VOUT = 2VP-P HD3 –50 –60 HD2 –70 –80 –70 –80 –90 –100 –100 –100 –110 –110 –110 10 100 FREQUENCY (MHz) 1 1000 1000 –10 Distortion (Unfiltered) vs Frequency, Differential Input, RLOAD = 100Ω –10 –10 UNFILTERED OUTPUTS –20 VOUT = 2VP-P UNFILTERED OUTPUTS –20 VOUT = 2VP-P –30 HD3 DISTORTION (dBc) HD2 –60 –70 –80 –30 HD3 –40 DISTORTION (dBc) UNFILTERED OUTPUTS –20 VOUT = 2VP-P –50 –50 HD2 –60 –70 –80 –50 –70 –80 –90 –100 –100 –100 –110 1000 –110 10 100 FREQUENCY (MHz) 1 19932 G13 –50 –50 –55 –55 HD3 UNFILTERED OUTPUTS –70 –75 –80 HD2 FILTERED OUTPUTS –85 HD3 FILTERED OUTPUTS –90 –50 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 11 19932 G16 –55 HD3 UNFILTERED OUTPUTS –60 –60 –65 HD2 UNFILTERED OUTPUTS –65 –70 –75 –80 –85 HD2 FILTERED OUTPUTS –100 HD3 UNFILTERED OUTPUTS HD3 FILTERED OUTPUTS –70 –75 –80 HD2 UNFILTERED OUTPUTS –85 –90 HD3 FILTERED OUTPUTS –95 –1 Distortion vs Output Amplitude 70MHz Differential Input, RLOAD = 100Ω –90 –95 –100 DISTORTION (dBc) HD2 UNFILTERED OUTPUTS 1000 19932 G15 Distortion vs Output Amplitude 70MHz Differential Input, RLOAD = 400Ω –65 10 100 FREQUENCY (MHz) 1 19932 G14 Distortion vs Output Amplitude 70MHz Differential Input, No RLOAD –60 1000 DISTORTION (dBc) 10 100 FREQUENCY (MHz) HD2 –60 –90 –110 HD3 –40 –90 1 1000 19932 G12 Distortion (Unfiltered) vs Frequency, Differential Input, RLOAD = 400Ω Distortion (Unfiltered) vs Frequency, Differential Input, No RLOAD –40 10 100 FREQUENCY (MHz) 1 19932 G11 19932 G10 –30 HD2 –60 –90 10 100 FREQUENCY (MHz) HD3 –50 –90 1 DISTORTION (dBc) DISTORTION (dBc) FILTERED OUTPUTS –20 VOUT = 2VP-P FILTERED OUTPUTS –20 VOUT = 2VP-P DISTORTION (dBc) Distortion (Filtered) vs Frequency Differential Input, RLOAD = 100Ω –1 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 11 19932 G17 HD2 FILTERED OUTPUTS –95 –100 –1 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 11 19932 G18 19932fa 7 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Distortion (Filtered) vs Frequency Single-Ended Input, No RLOAD –10 –10 –30 –30 –40 –40 HD3 –50 HD2 –70 –80 FILTERED OUTPUTS –20 VOUT = 2VP-P –30 HD3 –50 HD2 –60 –70 –80 –50 –70 –80 –90 –100 –100 –100 –110 –110 –110 10 100 FREQUENCY (MHz) 1 1000 1000 –10 –10 UNFILTERED OUTPUTS –20 VOUT = 2VP-P UNFILTERED OUTPUTS –20 VOUT = 2VP-P –30 DISTORTION (dBc) HD3 HD2 –70 –80 –30 HD3 –40 DISTORTION (dBc) –30 DISTORTION (dBc) Distortion (Unfiltered) vs Frequency, Single-Ended Input, RLOAD = 100Ω –10 UNFILTERED OUTPUTS –20 VOUT = 2VP-P –60 –50 HD2 –60 –70 –80 –50 –70 –80 –90 –90 –100 –100 –110 1000 –110 10 100 FREQUENCY (MHz) 1 19932 G22 19932 G23 –50 –50 –55 –55 HD3 UNFILTERED OUTPUTS DISTORTION (dBc) –65 HD3 FILTERED OUTPUTS –70 –75 –80 –85 HD2 UNFILTERED OUTPUTS –90 –95 –100 –1 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 19932 G24 –50 19932 G25 –55 HD3 UNFILTERED OUTPUTS –60 –65 HD3 FILTERED OUTPUTS –65 –70 –75 –80 –85 HD2 UNFILTERED OUTPUTS –100 HD3 UNFILTERED OUTPUTS HD3 FILTERED OUTPUTS –70 –75 –80 HD2 UNFILTERED OUTPUTS –85 HD2 FILTERED OUTPUTS –90 HD2 FILTERED OUTPUTS –95 11 1000 Distortion vs Output Amplitude 70MHz Single-Ended Input, RLOAD = 100Ω –60 –90 HD2 FILTERED OUTPUTS 10 100 FREQUENCY (MHz) 1 Distortion vs Output Amplitude 70MHz Single-Ended Input, RLOAD = 400Ω Distortion vs Output Amplitude 70MHz Single-Ended Input, No RLOAD –60 1000 DISTORTION (dBc) 10 100 FREQUENCY (MHz) HD2 –60 –90 –110 HD3 –40 –100 1 1000 19932 G21 Distortion (Unfiltered) vs Frequency, Single-Ended Input, RLOAD = 400Ω Distortion (Unfiltered) vs Frequency, Single-Ended Input, No RLOAD –50 10 100 FREQUENCY (MHz) 1 19932 G20 19932 G19 –40 HD2 –60 –90 10 100 FREQUENCY (MHz) HD3 –40 –90 1 DISTORTION (dBc) DISTORTION (dBc) DISTORTION (dBc) DISTORTION (dBc) –10 FILTERED OUTPUTS –20 VOUT = 2VP-P FILTERED OUTPUTS –20 VOUT = 2VP-P –60 Distortion (Filtered) vs Frequency Single-Ended Input, RLOAD = 100Ω Distortion (Filtered) vs Frequency Single-Ended Input, RLOAD = 400Ω –95 –1 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 11 19932 G26 –100 –1 1 3 5 7 9 OUTPUT AMPLITUDE (dBm) 11 19932 G27 19932fa 8 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Output 1dB Compression vs Frequency 25 20 RLOAD = 100Ω 20 15 10 5 15 10 0 5 –5 –10 0 10 100 FREQUENCY (MHz) VCC = 5V MEASURED USING DC800A DEMO BOARD 10 1000 100 FREQUENCY (MHz) 19932 G28 INPUT IMPEDANCE (MAGNITUDE Ω, PHASE°) –50 ISOLATION (dB) –60 –70 –80 –90 –100 –110 10 100 1000 FREQUENCY (MHz) 2 0 100 IMPEDANCE MAGNITUDE 150 100 50 0 10 1 IMPEDANCE PHASE –100 0.1 1 10 100 FREQUENCY (MHz) 1 1000 –25 –30 –35 –40 –45 –50 PSRR, CMRR vs Frequency 100 MEASURED USING DC800A DEMO BOARD –5 90 –10 80 –15 70 –20 –25 –30 –35 19932 G34 UNFILTERED OUTPUTS CMRR 60 50 40 30 –40 20 –45 10 PSRR 0 –50 1000 1000 19932 G33 PSRR, CMRR (dB) –20 10 100 FREQUENCY (MHz) 19932 G32 OUTPUT REFLECTION COEFFICIENT (S22) –15 UNFILTERED OUTPUTS –50 0 –10 1000 19932 G30 Output Reflection Coefficient vs Frequency MEASURED USING DC800A DEMO BOARD 100 FREQUENCY (MHz) Differential Output Impedance vs Frequency 200 10000 –5 100 FREQUENCY (MHz) 4 250 Input Reflection Coefficient vs Frequency 10 6 10 300 19932 G31 0 8 Differential Input Impedance vs Frequency UNFILTERED OUTPUTS 1 10 19932 G29 Isolation vs Frequency –40 12 1000 OUTPUT IMPEDANCE (Ω) 1 INPUT REFLECTION COEFFICIENT (S11) INPUT REFERRED NOISE VOLTAGE (nV/√Hz) 25 UNFILTERED OUTPUTS RLOAD = 400Ω NOISE FIGURE (dB) OUTPUT 1dB COMPRESSION (dBm) 30 Input Referred Noise Voltage vs Frequency Noise Figure vs Frequency 10 100 FREQUENCY (MHz) 1000 19932 G35 1 10 100 FREQUENCY (MHz) 1000 19932 G36 19932fa 9 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Small-Signal Transient Response Large-Signal Transient Response 3.0 RLOAD = 100Ω PER OUTPUT Overdrive Recovery Time 4.0 RLOAD = 100Ω PER OUTPUT 2.8 3.5 2.24 2.6 3.0 2.22 2.20 2.18 2.16 2.14 OUTPUT VOLTAGE (V) 2.26 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 2.28 2.4 2.2 2.0 1.8 1.6 2.12 2.5 5 10 15 20 25 30 35 40 45 50 TIME (ns) 1.5 1.0 0 5 10 15 20 25 30 35 40 45 50 TIME (ns) 19932 G37 0 19932 G39 Turn-On Time Turn-Off Time 4 4 +OUT +OUT 3 –66 3 2 –OUT HD3 –72 –OUT 1 0 RLOAD = 100Ω PER OUTPUT 4 2 –74 –76 1.2 VOLTAGE (V) VOLTAGE (V) DISTORTION (dBc) 2 –70 25 50 75 100 125 150 175 200 225 250 TIME (ns) 19932 G38 FILTERED OUTPUTS, NO RLOAD VOUT = 70MHz 2VP-P –68 –OUT 0.5 0 Distortion vs Output Common Mode Voltage LT1993-2 Driving LTC2249 14-Bit ADC –64 RLOAD = 100Ω PER OUTPUT 2.0 1.4 0 +OUT 1 0 4 ENABLE 2 ENABLE HD2 0 0 –2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 OUTPUT COMMON MODE VOLTAGE (V) 19932 G40 0 125 250 375 TIME (ns) 500 625 19932 G41 RLOAD = 100Ω PER OUTPUT –2 0 125 250 375 TIME (ns) 500 625 19932 G42 19932fa 10 LT1993-2 U W TYPICAL PERFOR A CE CHARACTERISTICS 50MHz 8192 Point FFT, LT1993-2 Driving LTC2249 14-Bit ADC 0 8192 POINT FFT –10 fIN = 50MHz, –1dBFS –20 FILTERED OUTPUTS –10 –30 –30 –30 –50 –60 –70 –80 0 –40 –50 –60 –70 –80 –40 –50 –60 –70 –80 –90 –90 –90 –100 –100 –100 –110 –110 –110 –120 –120 5 10 15 20 25 30 FREQUENCY (MHz) 35 40 0 5 10 15 20 25 30 FREQUENCY (MHz) –120 35 19932 G46 –40 –50 –60 –70 –80 –30 –40 –50 –60 –70 –80 –60 –70 –80 –90 –100 –100 –110 –110 –110 –120 –120 15 20 25 30 FREQUENCY (MHz) 35 40 0 5 10 15 20 25 30 35 FREQUENCY (MHz) 40 –50 –100 10 35 –40 –90 5 15 20 25 30 FREQUENCY (MHz) 0 32768 POINT FFT –10 TONE CENTER FREQUENCIES –20 AT 62.5MHz, 67.5MHz, 72.5MHz, 77.5MHz –30 –90 0 10 19932 G48 0 32768 POINT FFT –10 TONE CENTER FREQUENCIES –20 AT 67.5MHz, 72.5MHz AMPLITUDE (dBFS) –30 5 4-Tone WCDMA Waveform, LT1993-2 Driving LTC2255 14-Bit ADC at 92.16Msps 2-Tone WCDMA Waveform, LT1993-2 Driving LTC2255 14-Bit ADC at 92.16Msps 32768 POINT FFT TONE 1 AT 69.5MHz, –7dBFS TONE 2 AT 70.5MHz, –7dBFS FILTERED OUTPUTS –20 0 AMPLITUDE (dBFS) 0 40 19932 G47 70MHz 2-Tone 32768 Point FFT, LT1993-2 Driving LTC2249 14-Bit ADC –10 8192 POINT FFT fIN = 70MHz, –1dBFS FILTERED OUTPUTS –20 AMPLITUDE (dBFS) –40 0 AMPLITUDE (dBFS) 70MHz 8192 Point FFT, LT1993-2 Driving LTC2249 14-Bit ADC 0 8192 POINT FFT –10 fIN = 30MHz, –1dBFS –20 FILTERED OUTPUTS AMPLITUDE (dBFS) AMPLITUDE (dBFS) 30MHz 8192 Point FFT, LT1993-2 Driving LTC2249 14-Bit ADC 40 45 19932 G50 –120 0 5 10 15 20 25 30 35 FREQUENCY (MHz) 40 45 19932 G51 19932 G49 19932fa 11 LT1993-2 U U U PI FU CTIO S VOCM (Pin 2): This pin sets the output common mode voltage. Without additional biasing, both inputs bias to this voltage as well. This input is high impedance. VCCA, VCCB, VCCC (Pins 3, 10, 1): Positive Power Supply (Normally Tied to 5V). All three pins must be tied to the same voltage. Bypass each pin with 1000pF and 0.1µF capacitors as close to the package as possible. Split supplies are possible as long as the voltage between VCC and VEE is 5V. VEEA, VEEB, VEEC (Pins 4, 9, 12): Negative Power Supply (Normally Tied to Ground). All three pins must be tied to the same voltage. Split supplies are possible as long as the voltage between VCC and VEE is 5V. If these pins are not tied to ground, bypass each pin with 1000pF and 0.1µF capacitors as close to the package as possible. +OUT, –OUT (Pins 5, 8): Outputs (Unfiltered). These pins are high bandwidth, low-impedance outputs. The DC output voltage at these pins is set to the voltage applied at VOCM. +OUTFILTERED, –OUTFILTERED (Pins 6, 7): Filtered Outputs. These pins add a series 25Ω resistor from the unfiltered outputs and three 12pF capacitors. Each output has 12pF to VEE, plus an additional 12pF between each pin (See the Block Diagram). This filter has a –3dB bandwidth of 175MHz. ENABLE (Pin 11): This pin is a TTL logic input referenced to the VEEC pin. If low, the LT1993-2 is enabled and draws typically 100mA of supply current. If high, the LT1993-2 is disabled and draws typically 250µA. +INA, +INB (Pins 15, 16): Positive Inputs. These pins are normally tied together. These inputs may be DC- or ACcoupled. If the inputs are AC-coupled, they will self-bias to the voltage applied to the VOCM pin. –INA, –INB (Pins 14, 13): Negative Inputs. These pins are normally tied together. These inputs may be DC- or ACcoupled. If the inputs are AC-coupled, they will self-bias to the voltage applied to the VOCM pin. Exposed Pad (Pin 17): Tie the pad to VEEC (Pin 12). If split supplies are used, DO NOT tie the pad to ground. 19932fa 12 LT1993-2 W BLOCK DIAGRA 200Ω –INA 200Ω 12pF – 14 –INB VEEA VCCA +OUT 5 A 200Ω +OUTFILTERED + 13 6 25Ω VEEA VCCC 200Ω VOCM + 2 C 12pF – VEEC 200Ω 25Ω +INA 7 + 16 +INB –OUTFILTERED VCCB 200Ω –OUT 8 B 200Ω – 15 12pF VEEB VEEB 200Ω BIAS 3 10 VCCA 1 VCCB 11 VCCC 4 ENABLE 9 VEEA 19932 BD 12 VEEB VEEC 19932fa 13 LT1993-2 U W U U APPLICATIO S I FOR ATIO Circuit Description Input Impedance and Matching Networks The LT1993-2 is a low-noise, low-distortion differential amplifier/ADC driver with: Because of the internal feedback network, calculation of the LT1993-2’s input impedance is not straightforward from examination of the block diagram. Furthermore, the input impedance when driven differentially is different than when driven single-ended. When driven differentially, the LT1993-2’s input impedance is 200Ω (differential); when driven single-ended, the input impedance is 133Ω. • DC to 800MHz –3dB bandwidth • Fixed gain of 2V/V (6dB) independent of RLOAD • 200Ω differential input impedance • Low output impedance • Built-in, user adjustable output filtering • Requires minimal support circuitry Referring to the block diagram, the LT1993-2 uses a closedloop topology which incorporates 3 internal amplifiers. Two of the amplifiers (A and B) are identical and drive the differential outputs. The third amplifier (C) is used to set the output common mode voltage. Gain and input impedance are set by the 200Ω resistors in the internal feedback network. Output impedance is low, determined by the inherent output impedance of amplifiers A and B, and further reduced by internal feedback. The LT1993-2 also includes built-in single-pole output filtering. The user has the choice of using the unfiltered outputs, the filtered outputs (175MHz –3dB lowpass), or modifying the filtered outputs to alter frequency response by adding additional components. Many lowpass and bandpass filters are easily implemented with just one or two additional components. The LT1993-2 has been designed to minimize the need for external support components such as transformers or AC-coupling capacitors. As an ADC driver, the LT1993-2 requires no external components except for power-supply bypass capacitors. This allows DC-coupled operation for applications that have frequency ranges including DC. At the outputs, the common mode voltage is set via the VOCM pin, allowing the LT1993-2 to drive ADCs directly. No output AC-coupling capacitors or transformers are needed. At the inputs, signals can be differential or single-ended with virtually no difference in performance. Furthermore, DC levels at the inputs can be set independently of the output common mode voltage. These input characteristics often eliminate the need for an input transformer and/or AC-coupling capacitors. For single-ended 50Ω applications, an 80.6Ω shunt matching resistor to ground will result in the proper input termination (Figure 1). For differential inputs there are several termination options. If the input source is 50Ω differential, then input matching can be accomplished by either a 67Ω shunt resistor across the inputs (Figure 3), or a 33Ω shunt resistor on each of the inputs to ground (Figure 2). If additional AC gain is desired, a 1:4 impedance ratio transformer (like the Mini-Circuits TCM4-19) can also be used to better match impedances and to provide an additional 6dB of gain (Figure 4). With a 1:4 impedance ratio transformer, ideal matching impedance at the transformer output is 200Ω, so no termination resistors are required to match the LT1993-2’s 200Ω input impedance. 13 14 –INB –INA –OUT 8 0.1µF LT1993-2 15 IF IN 16 80.6Ω +INB +OUT +INA 5 ZIN = 50Ω SINGLE-ENDED 19932 F01 Figure 1. Input Termination for Single-Ended 50Ω Input Impedance 13 IF IN– ZIN = 50Ω DIFFERENTIAL 14 –INB –INA –OUT 8 33Ω LT1993-2 15 IF IN+ 16 33Ω +INB +INA +OUT 5 19932 F02 Figure 2. Input Termination for Differential 50Ω Input Impedance 19932fa 14 LT1993-2 U U W U APPLICATIO S I FOR ATIO 13 IF IN– 14 ZIN = 50Ω DIFFERENTIAL –OUT –INA 67Ω 8 high impedance inputs of these differential ADCs. If the filtered outputs are used, then cutoff frequency and the type of filter can be tailored for the specific application if needed. 5 Wideband Applications (Using the +OUT and –OUT Pins) LT1993-2 15 IF IN+ –INB 16 +INB +OUT +INA 19932 F02 Figure 3. Alternate Input Termination for Differential 50Ω Input Impedance 13 14 –INB –INA 0.1µF ZIN = 50Ω DIFFERENTIAL 8 LT1993-2 15 16 1:4 TRANSFORMER (MINI-CIRCUITS TCM4-19) –OUT +INB +INA +OUT 5 19932 F04 Figure 4. Input Termination for Differential 50Ω Input Impedance with 6dB Additional Gain In applications where the full bandwidth of the LT1993-2 is desired, the unfiltered output pins (+OUT and –OUT) should be used. They have a low output impedance; therefore, gain is unaffected by output load. Capacitance in excess of 5pF placed directly on the unfiltered outputs results in additional peaking and reduced performance. When driving an ADC directly, a small series resistance is recommended between the LT1993-2’s outputs and the ADC inputs (Figure 5). This resistance helps eliminate any resonances associated with bond wire inductances of either the ADC inputs or the LT1993-2’s outputs. A value between 10Ω and 25Ω gives excellent results. Single-Ended to Differential Operation –OUT The LT1993-2’s performance with single-ended inputs is comparable to its performance with differential inputs. This excellent single-ended performance is largely due to the internal topology of the LT1993-2. Referring to the block diagram, if the +INA and +INB pins are driven with a single-ended signal (while –INA and –INB are tied to AC ground), then the +OUT and –OUT pins are driven differentially without any voltage swing needed from amplifier C. Single-ended to differential conversion using more conventional topologies suffers from performance limitations due to the common mode amplifier. Driving ADCs The LT1993-2 has been specifically designed to interface directly with high speed Analog to Digital Converters (ADCs). In general, these ADCs have differential inputs, with an input impedance of 1k or higher. In addition, there is generally some form of lowpass or bandpass filtering just prior to the ADC to limit input noise at the ADC, thereby improving system signal to noise ratio. Both the unfiltered and filtered outputs of the LT1993-2 can easily drive the 8 10Ω TO 25Ω LT1993-2 ADC 10Ω TO 25Ω +OUT 5 19932 F05 Figure 5. Adding Small Series R at LT1993-2 Output Filtered Applications (Using the +OUTFILTERED and –OUTFILTERED Pins) Filtering at the output of the LT1993-2 is often desired to provide either anti-aliasing or improved signal to noise ratio. To simplify this filtering, the LT1993-2 includes an additional pair of differential outputs (+OUTFILTERED and –OUTFILTERED) which incorporate an internal lowpass filter network with a –3dB bandwidth of 175MHz (Figure 6). These pins each have an output impedance of 25Ω. Internal capacitances are 12pF to VEE on each filtered output, plus an additional 12pF capacitor connected differentially between the two filtered outputs. This resistor/capacitor combination creates filtered outputs 19932fa 15 LT1993-2 U U W U APPLICATIO S I FOR ATIO that look like a series 25Ω resistor with a 36pF capacitor shunting each filtered output to AC ground, giving a –3dB bandwidth of 175MHz. LT1993-2 VEE 25Ω 8 –OUT 12pF 7 –OUTFILTERED FILTERED OUTPUT (175MHz) 12pF 25Ω 6 +OUTFILTERED 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 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). 12pF VEE LT1993-2 5 +OUT VEE 8 –OUT 19932 F06 25Ω Figure 6. LT1993-2 Internal Filter Topology –3dB BW ≈175MHz 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 +OUTFILTERED and the other between –OUT and –OUTFILTERED (Figure 7). These resistors are in parallel with the internal 25Ω resistor, lowering the overall resistance and increasing filter bandwidth. To double the filter bandwidth, for example, add two external 25Ω resistors to lower the series resistance to 12.5Ω. The 36pF of capacitance remains unchanged, so filter bandwidth doubles. LT1993-2 8 –OUT VEE 25Ω 25Ω 12pF 12pF 12pF 7 –OUTFILTERED 12pF 12pF FILTERED OUTPUT (87.5MHz) 25Ω 6 +OUTFILTERED 12pF 12pF VEE 5 +OUT 19932 F08 Figure 8. LT1993-2 Internal Filter Topology Modified for 1/2x Filter Bandwidth (3 External Capacitors) Bandpass filtering is also easily implemented with just a few external components. An additional 120pF and 39nH, each added differentially between +OUTFILTERED and –OUTFILTERED creates a bandpass filter with a 71MHz center frequency, –3dB points of 55MHz and 87MHz, and 1.6dB of insertion loss (Figure 9). 7 –OUTFILTERED FILTERED OUTPUT (350MHz) 12pF 25Ω LT1993-2 VEE 6 +OUTFILTERED 12pF 25Ω 25Ω 8 –OUT 12pF 7 –OUTFILTERED VEE 5 +OUT 19932 F07 Figure 7. LT1993-2 Internal Filter Topology Modified for 2x Filter Bandwidth (2 External Resistors) 12pF 39nH FILTERED OUTPUT 120pF (71MHz BANDPASS, –3dB @ 55MHz/87MHz) 25Ω 6 +OUTFILTERED 12pF To decrease filter bandwidth, add two external capacitors, one from +OUTFILTERED to ground, and the other from –OUTFILTERED to ground. A single differential capacitor connected between +OUTFILTERED and –OUTFILTERED can also be used, but since it is being driven differentially VEE 5 +OUT 19932 F09 Figure 9. LT1993-2 Output Filter Topology Modified for Bandpass Filtering (1 External Inductor, 1 External Capacitor) 19932fa 16 LT1993-2 U W U U APPLICATIO S I FOR ATIO Output Common Mode Adjustment The LT1993-2’s output common mode voltage is set by the VOCM pin. It is a high-impedance input, capable of setting the output common mode voltage anywhere in a range from 1.1V to 3.6V. Bandwidth of the VOCM pin is typically 300MHz, so for applications where the VOCM pin is tied to a DC bias voltage, a 0.1µF capacitor at this pin is recommended. For best distortion performance, the voltage at the VOCM pin should be between 1.8V and 2.6V. When interfacing with most ADCs, there is generally a VOCM output pin that is at about half of the supply voltage of the ADC. For 5V ADCs such as the LTC17XX family, this VOCM output pin should be connected directly (with the addition of a 0.1µF capacitor) to the input VOCM pin of the LT1993-2. For 3V ADCs such as the LTC22XX families, the LT1993-2 will function properly using the 1.65V from the ADC’s VCM reference pin, but improved Spurious Free Dynamic Range (SFDR) and distortion performance can be achieved by level-shifting the LTC22XX’s VCM reference voltage up to at least 1.8V. This can be accomplished as shown in Figure 10 by using a resistor divider between the LTC22XX’s VCM output pin and VCC and then bypassing the LT1993-2’s VOCM pin with a 0.1µF capacitor. For a common mode voltage above 1.9V, AC coupling capacitors are recommended between the LT1993-2 and LTC22XX 11k 1.9V 13 14 –INB –INA VOCM +OUTFILTERED 0.1µF 31 1.5V 6 LT1993-2 15 IF IN 16 –OUTFILTERED +INB 4.02k 2 10Ω 1 7 VCM AIN+ LTC22xx 10Ω 2 AIN– +INA 80.6Ω Figure 10. Level Shifting 3V ADC VCM Voltage for Improved SFDR Large Output Voltage Swings The LT1993-2 has been designed to provide the 3.2VP-P output swing needed by the LTC1748 family of 14-bit low-noise ADCs. This additional output swing improves system SNR by up to 4dB. Typical performance curves and AC specifications have been included for these applications. Input Bias Voltage and Bias Current The input pins of the LT1993-2 are internally biased to the voltage applied to the VOCM pin. No external biasing resistors are needed, even for AC-coupled operation. The input bias current is determined by the voltage difference between the input common mode voltage and the VOCM pin (which sets the output common mode voltage). At both the positive and negative inputs, any voltage difference is imposed across 200Ω, generating an input bias current. For example, if the inputs are tied to 2.5V with the VOCM pin at 2.2V, then a total input bias current of 1.5mA will flow into the LT1993-2’s +INA and +INB pins. Furthermore, an additional input bias current totaling 1.5mA will flow into the –INA and –INB inputs. Application (Demo) Boards 3V 0.1µF ADCs because of the input voltage range constraints of the ADC. 19932 F10 The DC800A Demo Board has been created for stand-alone evaluation of the LT1993-2 with either single-ended or differential input and output signals. As shown, it accepts a single-ended input and produces a single-ended output so that the LT1993-2 can be evaluated using standard laboratory test equipment. For more information on this Demo Board, please refer to the Demo Board section of this data sheet. There are also additional demo boards available that combine the LT1993-2 with a variety of different Linear Technology ADCs. Please contact the factory for more information on these demo boards. 19932fa 17 LT1993-2 U TYPICAL APPLICATIO 19932fa 18 LT1993-2 U PACKAGE DESCRIPTIO UD Package 16-Lead Plastic QFN (3mm × 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 × 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 19932fa 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. 19 LT1993-2 U TYPICAL APPLICATIO Demo Circuit DC800A Schematic (AC Test Circuit) R18 0Ω R17 0Ω VCC VCC GND VCC 1 SW1 TP1 ENABLE 2 3 R16 0Ω 2 C17 1000pF 1 2 1 C18 0.01µF 1 1 J1 –IN T1 5 1:4 Z-RATIO 4 MINICIRCUITS TCM 4-19 14 2 C1 0.1µF R5 0Ω 16 2 R3 [1] 9 VCCB VEEB –INB –OUT –INA –OUTFILTERED +INB +OUTFILTERED +INA VCCC 1 VCC C10 2 0.01µF 1 10 ENABLE VOCM VCCA +OUT VEEA 2 3 4 2 C12 1000pF C9 2 1000pF 1 1 C4 0.1µF R10 8 24.9Ω 7 LT1993-2 15 3 VCC 11 VEEC +6dB 2 1 R1 1Ω 13 C21 0.1µF 1 • • 0dB R6 0Ω 2 1 J2 +IN 12 C2 0.1µF 6 5 1 R8 [1] R7 [1] R9 24.9Ω L1 [1] 1 C11 [1] 2 R14 0Ω R12 75Ω 2 J4 –OUT T2 3 1:4 Z-RATIO 4 2 C8 [1] 1 R15 [1] +10.8dB +6dB 2 1 C3 0.1µF 1 R11 75Ω MINI5 0dB CIRCUITS TCM 4-19 J5 +OUT 2 1 VCC 2 1 • R4 [1] • R2 0Ω 2 C16 [1] 2 1 C22 0.1µF R13 [1] C13 0.01µF R19 14k J6 TEST IN 1 T3 1:4 5 1 1 2 • • TP2 VCC C5 0.1µF C19, 0.1µF 1 4 MINICIRCUITS TCM 4-19 C7 0.01µF R21 [1] 2 C6 0.1µF 2 R22 [1] 4 J7 TEST OUT 2 1 2 1 3 1 T4 4:1 3 C20, 0.1µF 2 • 2 R20 11k • J3 VOCM MINI5 CIRCUITS TCM 4-19 VCC 1 2 1 TP3 GND C14 4.7µF 2 1 C15 1µF NOTES: UNLESS OTHERWISE SPECIFIED, [1] DO NOT STUFF. 1 19932 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1993-4 900MHz Differential Amplifier/ADC Driver AV = 4V/V, NF = 14.5dB, OIP3 = 40dBm at 70MHz LT1993-10 700MHz Differential Amplifier/ADC Driver AV = 10V/V, NF = 12.7dB, OIP3 = 40dBm at 70MHz LT5514 Ultralow Distortion IF Amplifier/ADC Driver Digitally Controlled Gain Output IP3 47dBm at 100MHz LT6600-2.5 Very Low Noise Differential Amplifier and 2.5MHz Lowpass Filter 86dB S/N with 3V Supply, SO-8 Package LT6600-5 Very Low Noise Differential Amplifier and 5MHz Lowpass Filter 82dB S/N with 3V Supply, SO-8 Package LT6600-10 Very Low Noise Differential Amplifier and 10MHz Lowpass Filter 82dB S/N with 3V Supply, SO-8 Package LT6600-20 Very Low Noise Differential Amplifier and 20MHz Lowpass Filter 76dB S/N with 3V Supply, SO-8 Package 19932fa 20 Linear Technology Corporation LT/LT 1005 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005