Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLinear IC - Op-amp, differential amplifier Differential QFN 16 EP (3x3)

LT1993-10

199310fb

4-Tone WCDMA Waveform,

LT1993-10 Driving LTC2255

14-Bit ADC at 92.16Msps

700MHz Low Distortion, Low

Noise Differential Ampliﬁ er/

ADC Driver (A

= 10

The LT

1993-10 is a low distortion, low noise Differential

Ampliﬁ er/ADC driver for use in applications from DC to

700MHz. The LT1993-10 has been designed for ease of

use, with minimal support circuitry required. Exception-

ally low input-referred noise and low distortion products

(with either single-ended or differential inputs) make the

LT1993-10 an excellent solution for driving high speed

12-bit and 14-bit ADCs. In addition to the normal unﬁ ltered

outputs (+OUT and –OUT), the LT1993-10 has a built-in

175MHz differential lowpass ﬁ lter and an additional pair

of ﬁ ltered outputs (+OUTFILTERED, –OUTFILTERED) to

reduce external ﬁ ltering components when driving high

speed ADCs. The output common mode voltage is easily set

via the V

OCM

pin, eliminating either an output transformer

or AC-coupling capacitors in many applications.

The LT1993-10 is designed to meet the demanding require-

ments of communications transceiver applications. It can

be used as a differential ADC driver, a general-purpose

differential gain block, or in any other application requir-

ing differential drive. The LT1993-10 can be used in data

acquisition systems required to function at frequencies

down to DC.

The LT1993-10 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.

■

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

■

700MHz –3dB Bandwidth

■

Fixed Gain of 10V/V (20dB)

■

Low Distortion:

40dBm OIP3, –70dBc HD3 (70MHz 2V

P-P

)

50.5dBm OIP3, –91dBc (10MHz 2V

P-P

)

■

Low Noise: 12.7dB NF, e

= 1.9nV/√Hz

■

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

4-Channel WCDMA Receive Channel

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

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

All other trademarks are the property of their respective owners.

•

2.2V 20dB Gain

199310 TA01

MA/COM

ETC 1-1-13

1:1

Z-RATIO

LTC2255 125Msps

14-BIT ADC SAMPLING

AT 92.16Msps

70MHz

IF IN

52.3pF82nH

LT1993-10

–INA

–INB

–OUTFILTERED

–OUT

+OUTFILTERED

+OUT

+INB

+INA

OCM

ENABLE

LTC2255

ADC

AIN–

AIN+

FREQUENCY (MHz)

–120

AMPLITUDE (dBFS)

–100

–80

–60

–40

10 15 25

199310 • TA02

3520 30 40 45

–20

–110

–90

–70

–50

–30

–10

32768 POINT FFT

TONE CENTER FREQUENCIES

AT 62.5MHz, 67.5MHz,

72.5MHz, 77.5MHz

Summary of content (16 pages)

PAGE 1
LT1993-10 700MHz Low Distortion, Low Noise Differential Amplifier/ ADC Driver (AV = 10V/V) DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®1993-10 is a low distortion, low noise Differential Ampliﬁer/ADC driver for use in applications from DC to 700MHz. The LT1993-10 has been designed for ease of use, with minimal support circuitry required.
PAGE 2
LT1993-10 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 12 VEEC VCCC 1 VOCM 2 11 ENABLE 17 VCCA 3 10 VCCB VEEA 4 5 6 7 8 +OUT –OUTFILTERED –OUT 9 +OUTFILTERED Total Supply Voltage (VCCA/VCCB/VCCC to VEEA/VEEB/VEEC) ...................................................5.5V Input Current (+INA, –INA, +INB, –INB, VOCM, ENABLE)................................................
PAGE 3
LT1993-10 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 ● MAX UNITS CMRR Common Mode Rejection Ratio 70 dB ROUTDIFF Output Resistance 0.
PAGE 4
LT1993-10 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 SRCM Common Mode Slew Rate 1.2V to 3.
PAGE 5
LT1993-10 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 –63 dBc 2VP-P Differential Composite (+OUTFILTERED, –OUTFILTERED), f1 = 49.5MHz, f2 = 50.
PAGE 6
LT1993-10 U W TYPICAL PERFOR A CE CHARACTERISTICS Frequency Response RLOAD = 400Ω Frequency Response vs CLOAD RLOAD = 400Ω 26 32 UNFILTERED OUTPUTS 20 29 11 VIN = 20mVP-P 8 UNFILTERED: RLOAD = 400Ω FILTERED: RLOAD = 350Ω 5 (EXTERNAL) + 50Ω (INTERNAL, FILTERED OUTPUTS) 2 1 100 1000 10 FREQUENCY (MHz) 10pF 5pF 23 1.
PAGE 7
LT1993-10 U W TYPICAL PERFOR A CE CHARACTERISTICS Distortion (Filtered) vs Frequency Differential Input, No RLOAD –10 FILTERED OUTPUTS VOUT = 2VP-P –20 –30 –30 –40 –40 DISTORTION (dBc) HD3 –50 –60 HD2 –70 –80 –55 –60 HD3 –50 –60 HD2 –70 –80 –85 –90 –90 –95 –110 10 100 FREQUENCY (MHz) 10 100 FREQUENCY (MHz) ''! / NOISE FIGURE (dB) 5 15 10 0 5 –5 –10 0 10 100 FREQUENCY (MHz) 1 10 1000 100 FREQUENCY (MHz) INPUT IMPEDANCE (MAGNITUDE Ω, PHASE°) UNFILTERED OUTPUTS –50 –60
PAGE 8
LT1993-10 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Reﬂection Coefﬁcient vs Frequency 0 –5 –10 –15 –20 –25 –30 –35 –40 –45 MEASURED USING DC800A DEMO BOARD –5 90 –10 80 –15 70 –20 –25 –30 –35 10 100 FREQUENCY (MHz) 100 FREQUENCY (MHz) 2.14 Overdrive Recovery Time 4.0 RLOAD = 1009 PER OUTPUT 2.6 2.4 2.2 2.0 1.8 1.6 2.12 0 5 0 5 1.
PAGE 9
LT1993-10 U W TYPICAL PERFOR A CE CHARACTERISTICS 50MHz 8192 Point FFT, LT1993-10 Driving LTC2249 14-Bit ADC 30MHz 8192 Point FFT, LT1993-10 Driving LT2249 14-Bit ADC 0 0 8192 POINT FFT fIN = 30MHz, –1dBFS FILTERED OUTPUTS –10 –20 0 8192 POINT FFT fIN = 50MHz, –1dBFS FILTERED OUTPUTS –10 –20 –20 –50 –60 –70 –80 –30 AMPLITUDE (dBFS) AMPLITUDE (dBFS) –40 –40 –50 –60 –70 –80 –40 –50 –60 –70 –80 –90 –90 –90 –100 –100 –100 –110 –110 –110 –120 –120 –120 0 5 10 15 20 25 30 FREQUENCY (
PAGE 10
LT1993-10 U U U PI FU CTIO S +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. –INA, –INB (Pins 14, 13): Negative Inputs. These pins are normally tied together. These inputs may be DC- or ACcoupled.
PAGE 11
LT1993-10 U W U U APPLICATIO S I FOR ATIO Circuit Description Input Impedance and Matching Networks The LT1993-10 is a low noise, low distortion differential ampliﬁer/ADC driver with: Because of the internal feedback network, calculation of the LT1993-10’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.
PAGE 12
LT1993-10 U W U U APPLICATIO S I FOR ATIO Single-Ended to Differential Operation The LT1993-10’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 LT1993-10.
PAGE 13
LT1993-10 U U W U APPLICATIO S I FOR ATIO LT1993-10 LT1993-10 8 –OUT VEE 259 VEE 259 12pF 259 7 –OUTFILTERED FILTERED OUTPUT (350MHz) 12pF 12pF 39nH 6 +OUTFILTERED 12pF 259 259 VEE Figure 6. LT1993-10 Internal Filter Topology Modiﬁed for 2x Filter Bandwidth (2 External Resistors) To decrease ﬁlter bandwidth, add two external capacitors, one from +OUTFILTERED to ground, and the other from –OUTFILTERED to ground.
PAGE 14
LT1993-10 U U W U APPLICATIO S I FOR ATIO 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 100Ω, 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 3mA will ﬂow into the LT1993-10’s +INA and +INB pins.
PAGE 15
LT1993-10 U TYPICAL APPLICATIO 199310fb 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.
PAGE 16
LT1993-10 U TYPICAL APPLICATIO Demo Circuit DC800A Schematic (AC Test Circuit) R18 0W R17 0W GND 1 SW1 TP1 ENABLE VCC VCC VCC 3 2 R16 0W 2 2 C17 1000pF 1 1 C18 0.01mF 1 1 J1 –IN T1 5 1:1 Z-RATIO 4 MA/COM ETC1-1-13 C1 0.1mF 1 R5 0W +INB 16 +INA VCCC 1 VCC C10 0.01mF VCC 2 1 R7 [1] 6 +OUTFILTERED VOCM VCCA +OUT VEEA 2 3 4 2 C12 1000pF C9 2 1000pF 1 1 1 R8 [1] 7 –OUTFILTERED C4 0.1mF R10 8 24.