Datasheet

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LT6604-10

660410fb

TYPICAL APPLICATION

DESCRIPTION

Dual Very Low Noise,

Differential Ampliﬁ er and

10MHz Lowpass Filter

The LT

6604-10 consists of two matched, fully differential

ampliﬁ ers, each with a 4th order, 10MHz lowpass ﬁ lter. The

ﬁ xed frequency lowpass ﬁ lter approximates a Chebyshev

response. By integrating a ﬁ lter and a differential ampli-

ﬁ er, distortion and noise are made exceptionally low. At

unity gain, the measured in band signal-to-noise ratio is

an impressive 82dB. At higher gains, the input referred

noise decreases, allowing the part to process smaller

input differential signals without signiﬁ cantly degrading

the signal-to-noise ratio.

Gain and phase are highly matched between the two chan-

nels. Gain for each channel is independently programmed

using two external resistors. The LT6604-10 enables level

shifting by providing an adjustable output common mode

voltage, making it ideal for directly interfacing to ADCs.

The LT6604-10 is fully speciﬁ ed for 3V operation. The

differential design enables outstanding performance at

a 2V

P-P

signal level for a single 3V supply. See the back

page of this data sheet for a complete list of related single

and dual differential ampliﬁ ers with integrated 2.5MHz to

20MHz lowpass ﬁ lters.

Channel to Channel Gain Matching, V

= 5V

FEATURES

APPLICATIONS

Dual Differential Ampliﬁ er with 10MHz Lowpass Filters

4th Order Filters

Approximates Chebyshev Response

Guaranteed Phase and Gain Matching

Resistor-Programmable Differential Gain

82dB Signal-to-Noise (3V Supply, 2V

P-P

Output)

Low Distortion, 2V

P-P

, 800 Load

1MHz: 88dBc 2nd, 97dBc 3rd

5MHz: 74dBc 2nd, 77dBc 3rd

Speciﬁ ed for Operation with 3V, 5V and ±5V Supplies

Fully Differential Inputs and Outputs

Adjustable Output Common Mode Voltage

Small 4mm × 7mm × 0.75mm QFN Package

Dual Differential ADC Driver Plus Filter

Single-Ended to Differential Converter

Matched, Dual, Differential Filter Stage

Common Mode Translation of Differential Signals

High Speed ADC Antialiasing and DAC Smoothing in

Wireless Infrastructure or Networking Applications

High Speed Test and Measurement Equipment

Medical Imaging

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

All other trademarks are the property of their respective owners.

402

–

660410 TA01

–

DOUTAIN

LT6604-10 LTC22xx

–

402

–OUTA

+OUTA

–OUTB

+OUTB

+INA

MIDB

MIDA

+INB

OCMA

OCMB

–INA

–INB

–

DOUTAIN

–

50

DUAL ADC

50

18pF

0.01µF

0.15

660410 TA01b

–0.1–0.15

0.05–0.05 0.1 0.2

0.25

GAIN MATCH (dB)

50 TYPICAL UNITS

= 25°C

GAIN = 1

= 10MHz

Summary of content (16 pages)

PAGE 1
LT6604-10 Dual Very Low Noise, Differential Amplifier and 10MHz Lowpass Filter DESCRIPTION FEATURES n n n n n n n The LT®6604-10 consists of two matched, fully differential ampliﬁers, each with a 4th order, 10MHz lowpass ﬁlter. The ﬁxed frequency lowpass ﬁlter approximates a Chebyshev response. By integrating a ﬁlter and a differential ampliﬁer, distortion and noise are made exceptionally low. At unity gain, the measured in band signal-to-noise ratio is an impressive 82dB.
PAGE 2
LT6604-10 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) 31 V– 32 V– 34 VMIDA 33 NC TOP VIEW Total Supply Voltage .................................................11V Operating Temperature Range (Note 6).... –40°C to 85°C Speciﬁed Temperature Range (Note 7) .... –40°C to 85°C Junction Temperature ........................................... 150°C Storage Temperature Range................... –65°C to 150°C Input Current +IN, –IN, VOCM, VMID (Note 8) .........................
PAGE 3
LT6604-10 ELECTRICAL CHARACTERISTICS The l denotes speciﬁcations that apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. Unless otherwise speciﬁed VS = 5V (V+ = 5V, V– = 0V), RIN = 402Ω, and RLOAD = 1k.
PAGE 4
LT6604-10 ELECTRICAL CHARACTERISTICS The l denotes speciﬁcations that apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. Unless otherwise speciﬁed VS = 5V (V+ = 5V, V– = 0V), RIN = 402Ω, and RLOAD = 1k.
PAGE 5
LT6604-10 TYPICAL PERFORMANCE CHARACTERISTICS Amplitude Response Passband Gain and Group Delay 10 1 VS = 5V GAIN = 1 0 60 0 55 GAIN –1 50 GAIN (dB) –30 –40 ( GAIN 20LOG –20 –50 –60 –70 –80 100k 1M 10M FREQUENCY (Hz) 100M –2 45 –3 40 –4 –5 35 GROUP DELAY 30 –6 25 –7 V = 5V S –8 GAIN = 1 TA = 25°C –9 0.5 20 15 60 80 10 65 VS = 5V 75 GAIN = 1 VIN = 1VP-P 70 TA = 25°C 45 8 40 35 GROUP DELAY 6 30 5 25 4 V = 5V S 3 GAIN = 4 TA = 25°C 2 0.
PAGE 6
LT6604-10 TYPICAL PERFORMANCE CHARACTERISTICS Distortion vs Signal Level VS = 3V, RL = 800Ω at Each Output, TA = 25°C, Gain = 1 –60 –70 –80 –90 –60 –70 –80 –90 –100 –110 –100 0 1 2 3 INPUT LEVEL (VP-P) 4 1 0 5 2 38 –3 2 3 –1 0 1 –2 INPUT COMMON MODE VOLTAGE RELATIVE TO VMID (V) 660410 G11 Transient Response, Differential Gain = 1 –70 –80 TA = 85°C VOUT+ 50mV/DIV 36 34 TA = 25°C DIFFERENTIAL INPUT 200mV/DIV 32 30 TA = –40°C 28 –90 100ns/DIV 660410 G14 26 –3 24 2 3 –1 0 1 –2 INPUT CO
PAGE 7
LT6604-10 PIN FUNCTIONS +INA and –INA (Pins 2, 4): Channel A Input Pins. Signals can be applied to either or both input pins through identical external resistors, RIN. The DC gain from differential inputs to the differential outputs is 402Ω/RIN. VOCMA (Pin 6): DC Common Mode Reference Voltage for the 2nd Filter Stage in Channel A. Its value programs the common mode voltage of the differential output of the ﬁlter.
PAGE 8
LT6604-10 BLOCK DIAGRAM VMIDA NC 34 33 NC 1 VIN+A RIN +INA VIN A RIN –INA V– 32 31 30 NC 11k 2 402Ω 11k NC 3 – V+A V– 4 NC 5 V– + OP AMP VOCM – 200Ω – PROPRIETARY LOWPASS FILTER STAGE 200Ω + – VOCM + 200Ω – + 200Ω VOCMA 6 29 –OUTA 28 NC 27 +OUTA 26 NC 25 V+A 402Ω V+B V– 7 24 V– 11k VMIDB 8 402Ω 11k RIN +INB 10 + OP AMP VOCM – RIN –INB + – VOCM + 200Ω NC 11 VIN–B 22 NC 200Ω – 23 NC 200Ω V– NC 9 VIN+B PROPRIETARY LOWPASS FILTER STAGE 21 –OU
PAGE 9
LT6604-10 APPLICATIONS INFORMATION Interfacing to the LT6604-10 operating with a single 3.3V supply and unity passband gain; the input signal is DC coupled. The common mode input voltage is 0.5V, and the differential input voltage is 2VP-P. The common mode output voltage is 1.65V, and the differential output voltage is 2VP-P for frequencies below 10MHz. The common mode output voltage is determined by the voltage at VOCM. Since VOCM is shorted to VMID, the output common mode is the mid-supply voltage.
PAGE 10
LT6604-10 APPLICATIONS INFORMATION In Figure 3 the LT6604-10 is providing 12dB of gain. The gain resistor has an optional 62pF in parallel to improve the passband ﬂatness near 10MHz. The common mode output voltage is set to 2V. The voltage at VMID, for VS = 3.3V, is 1.65V. The voltage at the DAC pins is given by: VDAC = VMID • Use Figure 4 to determine the interface between the LT6604-10 and a current output DAC. The gain, or “transimpedance,” is deﬁned as A = VOUT/IIN.
PAGE 11
LT6604-10 APPLICATIONS INFORMATION 2.5V 0.1μF NETWORK ANALYZER SOURCE 50Ω COILCRAFT TTWB-1010 1:1 388Ω 4 53.6Ω 25 – 27 34 1/2 + LT6604-10 6 2 388Ω – + 7 29 COILCRAFT TTWB-16A 4:1 402Ω NETWORK ANALYZER INPUT 50Ω 402Ω 0.1μF 660410 F05 –2.5V Figure 5 Figure 5 is a laboratory setup that can be used to characterize the LT6604-10 using single-ended instruments with 50Ω source impedance and 50Ω input impedance.
PAGE 12
LT6604-10 APPLICATIONS INFORMATION The LT6604-10 was designed to process a variety of input signals including signals centered on the mid-supply voltage and signals that swing between ground and a positive voltage in a single supply system (Figure 1). The range of allowable input common mode voltage (the average of VIN+ and VIN– in Figure 1) is determined by the power supply level and gain setting (see the Electrical Characteristics section).
PAGE 13
LT6604-10 APPLICATIONS INFORMATION Power Dissipation The LT6604-10 ampliﬁers combine high speed with large signal currents in a small package. There is a need to ensure that the die’s junction temperature does not exceed 150°C. The LT6604-10 has an exposed pad (pin 35) which is connected to the lower supply (V–). Connecting the pad to a ground plane helps to dissipate the heat generated by the chip.
PAGE 14
LT6604-10 TYPICAL APPLICATION Dual, Matched, 5th Order, 10MHz Lowpass Filter V+ 0.1μF VINA– R R C VINA+ C= R R 4 25 – 27 34 1/2 + LT6604-10 6 VOUTA+ – 29 VOUTA– 2 + 7 0.1μF 1 2π • R • 10MHz GAIN = 402Ω , MAXIMUM GAIN = 4 V– 2R V+ 0.1μF VINB– VINB+ C= R R R 12 17 VOUTB+ C – 19 8 1/2 + LT6604-10 14 R 10 – 21 VOUTB– 1 2π • R • 10MHz + 24 GAIN = 402Ω , MAXIMUM GAIN = 4 V– 2R 0.
PAGE 15
LT6604-10 PACKAGE DESCRIPTION UFF Package 34-Lead Plastic QFN (4mm × 7mm) (Reference LTC DWG # 05-08-1758 Rev Ø) 0.70 ± 0.05 1.90 ± 0.05 4.50 ± 0.05 PACKAGE OUTLINE 1.83 ± 0.05 3.10 ± 0.05 1.50 REF 1.90 ± 0.05 1.47 ± 0.05 2.64 ± 0.05 1.29 ± 0.05 0.25 ± 0.05 0.50 BSC 6.00 REF 6.10 ± 0.05 7.50 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ± 0.10 PIN 1 NOTCH R = 0.30 OR 0.25 × 45° CHAMFER R = 0.10 TYP 0.75 ± 0.05 1.50 REF 33 34 0.40 ± 0.
PAGE 16
LT6604-10 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1562-2 Very Low Noise, 8th Order Filter Building Block Lowpass and Bandpass Filters Up to 300kHz LTC1565-31 650kHz Linear Phase Lowpass Filter Continuous Time, 7th Order, Differential LTC1566-1 Low Noise, 2.