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LTC6400-14

640014fb

FREQUENCY (MHz)

050

OUTPUT IP3 (dBm)

100 150 200

640020 TA01b

250 300

(NOTE 7)

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

2.4GHz Low Noise, Low

Distortion Differential ADC

Driver for 300MHz IF

The LTC

6400-14 is a high-speed differential ampliﬁ er

targeted at processing signals from DC to 300MHz. The

part has been speciﬁ cally designed to drive 12-, 14- and

16-bit ADCs with low noise and low distortion, but can also

be used as a general-purpose broadband gain block.

The LTC6400-14 is easy to use, with minimal support

circuitry required. The output common mode voltage is

set using an external pin, independent of the inputs, which

eliminates the need for transformers or AC-coupling ca-

pacitors in many applications. The gain is internally ﬁ xed

at 14dB (5V/V).

The LTC6400-14 saves space and power compared to

alternative solutions using IF gain blocks and transformers.

The LTC6400-14 is packaged in a compact 16-lead 3mm ×

3mm QFN package and operates over the –40°C to 85°C

temperature range.

Equivalent Output IP3 vs

Frequency

2.4GHz –3dB Bandwidth

Fixed Gain of 5V/V (14dB)

–97dBc IMD3 at 70MHz (Equivalent OIP3 = 52.4dBm)

–66dBc IMD3 at 300MHz (Equivalent OIP3 = 36.9dBm)

1.1nV/√Hz Internal Op Amp Noise

2.5nV/√Hz Total Input Noise

7.5dB Noise Figure

Differential Inputs and Outputs

200Ω Input Impedance

2.85V to 3.5V Supply Voltage

85mA Supply Current (255mW)

1V to 1.6V Output Common Mode Voltage,

Adjustable

DC- or AC-Coupled Operation

Max Differential Output Swing 4.8V

P-P

Small 16-Lead 3mm × 3mm × 0.75mm QFN Package

Differential ADC Driver

Differential Driver/Receiver

Single Ended to Differential Conversion

IF Sampling Receivers

SAW Filter Interfacing

29Ω

68.5Ω

0.1μF

64014 TA01a

LTC6400-14

LTC2208

15Ω

0.1μF

1000pF

3.3V3.3V

15Ω

10Ω

100Ω

OCM

0.1μF

1.25V

33pF

COILCRAFT

0603CS

33pF

24nH

33pF

–IN

+IN

+OUT

–OUT

–

AIN

–

LTC2208

130Msps

16-Bit ADC

Single-Ended to Differential ADC Driver

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Summary of content (16 pages)

PAGE 1
LTC6400-14 2.4GHz Low Noise, Low Distortion Differential ADC Driver for 300MHz IF FEATURES DESCRIPTION n The LTC®6400-14 is a high-speed differential ampliﬁer targeted at processing signals from DC to 300MHz. The part has been speciﬁcally designed to drive 12-, 14- and 16-bit ADCs with low noise and low distortion, but can also be used as a general-purpose broadband gain block. n n n n n n n n n n n n n n 2.4GHz –3dB Bandwidth Fixed Gain of 5V/V (14dB) –97dBc IMD3 at 70MHz (Equivalent OIP3 = 52.
PAGE 2
LTC6400-14 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) +IN +IN –IN –IN TOP VIEW Supply Voltage (V+ – V –) .........................................3.6V Input Current (Note 2)..........................................±10mA Operating Temperature Range (Note 3) ...............................................–40°C to 85°C Speciﬁed Temperature Range (Note 4) ...............................................–40°C to 85°C Storage Temperature Range...................
PAGE 3
LTC6400-14 DC ELECTRICAL CHARACTERISTICS + The l –denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. V = 3V, V = 0V, +IN = –IN = VOCM = 1.25V, ENABLE = 0V, No RL unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX 14 14.5 UNITS Input/Output Characteristic GDIFF Gain VIN = ±200mV Differential l TCGAIN Gain Temperature Drift VIN = ±200mV Differential l –0.
PAGE 4
LTC6400-14 AC ELECTRICAL CHARACTERISTICS ENABLE = 0V, No RL unless otherwise noted. Speciﬁcations are at TA = 25°C. V+ = 3V, V– = 0V, VOCM = 1.25V, SYMBOL PARAMETER CONDITIONS MIN TYP –3dBBW –3dB Bandwidth 200mVP-P, OUT (Note 6) 1.2 2.37 MAX UNITS GHz 0.1dBBW Bandwidth for 0.1dB Flatness 200mVP-P, OUT (Note 6) 200 MHz 0.5dBBW Bandwidth for 0.
PAGE 5
LTC6400-14 AC ELECTRICAL CHARACTERISTICS ENABLE = 0V, No RL unless otherwise noted. SYMBOL Speciﬁcations are at TA = 25°C. V+ = 3V, V– = 0V, VOCM = 1.25V, PARAMETER CONDITIONS MIN TYP MAX UNITS Second/Third Order Harmonic Distortion 2VP-P, OUT, RL = 200Ω –78/–74 dBc 2VP-P, OUT, No RL –81/–79 dBc 140MHz Input Signal HD2,140M/HD3,140M IMD3,140M Third-Order Intermodulation (f1 = 139.5MHz f2 = 140.
PAGE 6
LTC6400-14 AC ELECTRICAL CHARACTERISTICS ENABLE = 0V, No RL unless otherwise noted. SYMBOL Speciﬁcations are at TA = 25°C. V+ = 3V, V– = 0V, VOCM = 1.25V, PARAMETER CONDITIONS MIN TYP MAX UNITS Second/ Third-Order Harmonic Distortion 2VP-P, OUT, RL = 200Ω –61/–51 dBc 2VP-P, OUT, No RL –61/–55 dBc 300MHz Input Signal HD2,300M/HD3,300M IMD3,300M Third-Order Intermodulation (f1 = 299.5MHz f2 = 300.
PAGE 7
LTC6400-14 TYPICAL PERFORMANCE CHARACTERISTICS 20 18 12 10 8 6 4 0 TEST CIRCUIT B 10 100 1000 FREQUENCY (MHz) 3000 0 TEST CIRCUIT B –50 PHASE GROUP DELAY –200 10 100 1000 FREQUENCY (MHz) 225 IMPEDANCE MAGNITUDE (Ω) –10 –20 –30 –40 –50 – 60 S11 S22 S11 200 ZOUT 150 100 50 –40 100 FREQUENCY (MHz) 50 30 10 –100 1000 0 1 13 4.0 12 3.5 3.0 EN 2.5 10 9 2.0 NOISE FIGURE 1.5 7 1.0 6 0.
PAGE 8
LTC6400-14 TYPICAL PERFORMANCE CHARACTERISTICS 1% Settling Time for 2V Output Step RL = 87.5Ω PER OUTPUT 4 TEST CIRCUIT B +IN 4.5 4 4.0 3 3.5 1 3.0 –IN 0 –1 2.5 2.0 +OUT –2 1.5 –3 1.
PAGE 9
LTC6400-14 TYPICAL PERFORMANCE CHARACTERISTICS Equivalent Output 1dB Compression Point vs Frequency Equivalent Output Third Order Intercept vs Frequency 70 IMD3 vs VICM and VOCM –85 NO RL 200Ω RL 60 SWEEP VOCM INPUT AC-COUPLED –88 18 17 DIFFERENTIAL INPUT 16 R = 375Ω L TEST CIRCUIT A (NOTE 7) 15 0 50 100 150 200 FREQUENCY (MHz) 50 IMD3 (dBc) OUTPUT IP3 (dBm) 19 40 30 250 300 0 VOUT = 2VP-P COMPOSITE at 100MHz DIFFERENTIAL INPUT NO RL DIFFERENTIAL INPUT (NOTE 7) –100 0 50 100 150 200 FREQU
PAGE 10
LTC6400-14 PIN FUNCTIONS V+ (Pins 1, 3, 10): Positive Power Supply (Normally tied to 3V or 3.3V). All three pins must be tied to the same voltage. Bypass each pin with 1000pF and 0.1μF capacitors as close to the pins as possible. VOCM (Pin 2): This pin sets the output common mode voltage. A 0.1μF external bypass capacitor is recommended. V – (Pins 4, 9, 12, 17): Negative Power Supply (GND). All four pins must be connected to same voltage/ground. –OUT, +OUT (Pins 5, 8): Unﬁltered Outputs.
PAGE 11
LTC6400-14 APPLICATIONS INFORMATION Circuit Operation The LTC6400-14 is a low noise and low distortion fully differential op amp/ADC driver with: • Operation from DC to 2.4GHz (–3dB bandwidth) • Fixed gain of 5V/V (14dB) • Differential input impedance 200Ω • Differential output impedance 25Ω • On-Chip 590MHz output ﬁlter The LTC6400 is composed of a fully differential ampliﬁer with on chip feedback and output common mode voltage control circuitry.
PAGE 12
LTC6400-14 APPLICATIONS INFORMATION RS 50Ω 1000Ω 100Ω 12.5Ω 13 +IN VIN + – LTC6400-14 0.1μF +OUT 8 50Ω RT 68.5Ω IN+ OUT– +OUTF 7 14 +IN 0.1μF 50Ω 15 –IN 0.1μF RT 29Ω IN– 2.7pF –OUTF 6 OUT+ 1000Ω 100Ω 12.5Ω –OUT 5 16 –IN 640014 F03 Figure 3. Input Termination for Single-Ended 50Ω Input Impedance In general, the single-ended input impedance and termination resistor RT are determined by the combination of RS, RG and RF.
PAGE 13
LTC6400-14 APPLICATIONS INFORMATION –40 SINGLE-ENDED INPUT fS = 122.8Msps –50 DRIVER V OUT = 2VP-P COMPOSITE –60 IMD3 (dBc) which is dominated by a low pass ﬁlter connected to the VOCM pin and is aimed to reduce common mode noise generation at the outputs. The internal common mode feedback loop has a –3dB bandwidth around 400MHz, allowing fast common mode rejection at the outputs of the LTC6400-14. The VOCM pin should be tied to a DC bias voltage with a 0.1μF bypass capacitor.
PAGE 14
LTC6400-14 APPLICATIONS INFORMATION network analyzer. There are also series resistors at the output to present the LTC6400 with a 375Ω differential load, optimizing distortion performance. Due to the input and output transformers, the –3dB bandwidth is reduced from 2.4GHz to approximately 1.8GHz. Test Circuit B uses a 4-port network analyzer to measure S-parameters and gain/phase response.
PAGE 15
LTC6400-14 TYPICAL APPLICATIONS Test Circuit B, 4-Port Analysis V+ 1000pF V– 0.1μF 11 V– V+ ENABLE 12 10 9 LTC6400-14 BIAS CONTROL RF 500Ω RG 100Ω +IN 13 PORT 1 (50Ω) ROUT 12.5Ω RFILT 50Ω 0.1μF 1/2 AGILENT E5O71A +IN 14 200Ω IN+ PORT 3 (50Ω) IN– CFILT 2.7pF 1/2 AGILENT E5O71A –OUTF 6 OUT+ RF 500Ω RG 100Ω –IN 16 0.1μF +OUTF 7 OUT– RFILT 50Ω –IN 15 PORT 2 (50Ω) +OUT 37.4Ω 8 ROUT 12.5Ω –OUT 37.4Ω PORT 4 (50Ω) 5 0.1μF 0.1μF COMMON MODE CONTROL 1 1000pF 2 V+ 3 VOCM 0.
PAGE 16
LTC6400-14 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS High-Speed Differential Ampliﬁers/Differential Op Amps LT®1993-2 800MHz Differential Ampliﬁer/ADC Driver AV = 2V/V, OIP3 = 38dBm at 70MHz LT1993-4 900MHz Differential Ampliﬁer/ADC Driver AV = 4V/V, OIP3 = 40dBm at 70MHz LT1993-10 700MHz Differential Ampliﬁer/ADC Driver AV = 10V/V, OIP3 = 40dBm at 70MHz LT1994 Low Noise, Low Distortion Differential Op Amp 16-Bit SNR and SFDR at 1MHz, Rail-to-Rail Outputs LT5514 Ultralow Distortion IF Am