LT5568-2EUF-PBF_技术文档

LT5568-2

GSM/EDGE Optimized,

High Linearity Direct

Quadrature Modulator

U

DESCRIPTIO

FEATURES

The LT^®5568-2 is a direct I/Q modulator designed for high

performance wireless applications, including wireless

infrastructure. It allows direct modulation of an RF signal

using differential baseband I and Q signals. It supports

GSM, EDGE, CDMA, CDMA2000 and other systems that

operate in the 850MHz to 965MHz band. It may be conﬁg-

ured as an image reject upconverting mixer, by applying

90° phase-shifted signals to the I and Q inputs. The I/Q

baseband inputs consist of voltage-to-current converters

that in turn drive double-balanced mixers. The outputs of

these mixers are summed and applied to an on-chip RF

transformer, which converts the differential mixer signals

to a 50Ω single-ended output. The four balanced I and Q

baseband input ports are intended for DC coupling from a

source with a common mode voltage level of about 0.5V.

The LO path consists of an LO buffer with single-ended

input, and precision quadrature generators that produce

the LO drive for the mixers. The supply voltage range is

4.5V to 5.25V.

■

Optimized Image Rejection for 850MHz to 965MHz

■

High OIP3: +22.9dBm at 900MHz

■

Low Output Noise Floor at 5MHz Offset:

No RF: –159.4dBm/Hz

P

OUT

= 4dBm: –153dBm/Hz

■

Integrated LO Buffer and LO Quadrature Phase

Generator

■

50Ω AC-Coupled Single-Ended LO and RF Ports

50Ω DC Interface to Baseband Inputs

Low Carrier Leakage: –43dBm at 900MHz

High Image Rejection: –52dBc at 900MHz

16-Lead 4mm × 4mm QFN Package

U

APPLICATIO S

■

Infrastructure Tx for GSM/Cellular Bands

■

Image Reject Up-Converters for Cellular Bands

■

Low-Noise Variable Phase-Shifter for 700MHz to

1050MHz Local Oscillator Signals

RFID Reader

■

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

All other trademarks are the property of their respective owners.

U

TYPICAL APPLICATIO

GSM EVM and Noise

vs RF Output Power at 900MHz

850MHz to 965MHz Direct Conversion Transmitter Application

5

4

–96

–98

5V

100nF

x 2

V

CC

LT5568-2

RF = 850MHz

TO 965MHz

I-DAC

V-I

I-CHANNEL

3

–100

PA

NOISE

0°

EN

90°

BALUN

2

1

0

–102

–104

–106

Q-CHANNEL

V-I

Q-DAC

EVM

4

55682 TA01

BASEBAND

GENERATOR

–10 –8 –6 –4 –2

0

2

6

VCO/SYNTHESIZER

GSM RF OUTPUT POWER (dBm)

55682 TA02

55682f

1

LT5568-2

W W U W

ABSOLUTE AXI U RATI GS

PIN CONFIGURATION

(Note 1)

TOP VIEW

Supply Voltage.........................................................5.5V

Common Mode Level of BBPI, BBMI and

BBPQ, BBMQ .......................................................2.5V

Operating Ambient Temperature

16 15 14 13

EN

GND

LO

1

2

3

4

12 GND

11 RF

17

(Note 2) ............................................... –40°C to 85°C

Storage Temperature Range................... –65°C to 125°C

Voltage on Any Pin

GND

10

9

GND

5

6

7

8

Not to Exceed...................... –500mV to V + 500mV

CC

UF PACKAGE

16-LEAD (4mm × 4mm) PLASTIC QFN

= 125°C, θ = 37°C/W

CAUTION: This part is sensitive to ESD. It is very

important that proper ESD precautions be observed

when handling the LT5568-2.

T

JMAX

JA

EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

TAPE AND REEL

PART MARKING

PACKAGE DESCRIPTION

16-Lead (4mm × 4mm) Plastic QFN

TEMPERATURE RANGE

–40°C to 85°C

LT5568-2EUF#PBF

LT5568-2EUF#TRPBF

55682

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

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/

ELECTRICAL CHARACTERISTICS

V

= 5V, EN = High, T = 25°C, f = 900MHz, f = 902MHz, P = 0dBm.

A LO RF LO

CC

BBPI, BBMI, BBPQ, BBMQ inputs 0.54V , Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper side-band selection).

DC

P

= –10dBm, unless otherwise noted. (Note 3)

RF, OUT

SYMBOL

RF Output (RF)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

f

RF Frequency Range

–3dB Bandwidth

–1dB Bandwidth

0.6 to 1.1

0.7 to 1

GHz

RF

S

RF Output Return Loss

RF Output Noise Floor

EN = High (Note 6)

EN = Low (Note 6)

–16

–18

dB

22, ON

22, OFF

NFloor

No Input Signal (Note 8)

–159.4

–153

–152.6

dBm/Hz

P

= 4dBm (Note 9)

= 4dBm (Note 10)

OUT

G

Conversion Power Gain

P

/P

–9

–6.8

–2.8

–23

8.6

–3

dB

P

OUT IN, I&Q

Conversion Voltage Gain

Absolute Output Power

20 • Log (V

/V

)

V

OUT, 50Ω IN, DIFF, I or Q

P

OUT

1V

CW Signal, I and Q

dBm

dB

P-P DIFF

G

3 • LO Conversion Gain Difference

Output 1dB Compression

Output 2nd Order Intercept

Output 3rd Order Intercept

(Note 17)

(Note 7)

3LO vs LO

OP1dB

OIP2

dBm

(Notes 13, 14)

(Notes 13, 15)

59

OIP3

22.9

55682f

2

LT5568-2

ELECTRICAL CHARACTERISTICS

V

= 5V, EN = High, T = 25°C, f = 900MHz, f = 902MHz, P = 0dBm.

A LO RF LO

CC

BBPI, BBMI, BBPQ, BBMQ inputs 0.54V , Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper side-band selection).

DC

P

= –10dBm, unless otherwise noted. (Note 3)

RF, OUT

SYMBOL

IR

PARAMETER

CONDITIONS

= 100kHz (Note 16)

MIN

TYP

MAX

UNITS

Image Rejection

f

–52

dBc

BB

LOFT

Carrier Leakage

(LO Feedthrough)

EN = High, P = 0dBm (Note 16)

–43

–65

dBm

LO

EN = Low, P = 0dBm (Note 16)

LO

LO Input (LO)

f

LO Frequency Range

0.6 to 1.1

0

GHz

dBm

dB

LO

P

S

LO Input Power

–10

5

LO

LO Input Return Loss

EN = High (Note 6)

EN = Low (Note 6)

(Note 5) at 900MHz

–15

–2.5

14.7

–3

11, ON

11, OFF

LO Input Return Loss

dB

NF

LO Input Referred Noise Figure

LO to RF Small Signal Gain

LO Input 3rd Order Intercept

dB

LO

G

dB

LO

IIP3

dBm

LO

Baseband Inputs (BBPI, BBMI, BBPQ, BBMQ)

BW

Baseband Bandwidth

–3dB Bandwidth

(Note 4)

380

0.54

47

MHz

V

BB

V

DC Common Mode Voltage

Single-Ended Input Resistance

Carrier Feedthrough on BB

Input 1dB Compression Point

CMBB

Ω

R

(Note 4)

IN, SE

P

OUT

= 0 (Note 4)

–38

4.3

dBm

LO2BB

IP1dB

Differential Peak-to-Peak (Notes 7, 18)

V

P-P, DIFF

Power Supply (V

)

CC

V

Supply Voltage

4.5

80

5

5.25

145

100

V

mA

µA

µs

CC

I

t

Supply Current

EN = High

110

CC, ON

CC, OFF

ON

Supply Current, Sleep Mode

Turn-On Time

EN = 0V

EN = Low to High (Note 11)

EN = High to Low (Note 12)

0.3

1.4

Turn-Off Time

µs

OFF

Enable (EN), Low = Off, High = On

Enable

Input High Voltage

Input High Current

EN = High

EN = 5V

1.0

V

µA

245

Sleep

Input Low Voltage

Input Low Current

EN = Low

EN = 0V

0.5

V

µA

0.01

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: Speciﬁcations over the –40°C to 85°C temperature range are assured

by design, characterization and correlation with statistical process controls.

Note 10: At 5MHz offset from the CW signal frequency.

Note 11: RF power is within 10% of ﬁnal value.

Note 12: RF power is at least 30dB lower than in the ON state.

Note 13: Baseband is driven by 2MHz and 2.1MHz tones. Drive level is set

in such a way that the two resulting RF tones are –10dBm each.

Note 14: IM2 measured at LO frequency + 4.1MHz.

Note 15: IM3 measured at LO frequency + 1.9MHz and LO frequency + 2.2MHz.

Note 16: Amplitude average of the characterization data set without image

or LO feedthrough nulling (unadjusted).

Note 3: Tests are performed as shown in the conﬁguration of Figure 7.

Note 4: On each of the four baseband inputs BBPI, BBMI, BBPQ and BBMQ.

Note 5: V(BBPI) – V(BBMI) = 1V , V(BBPQ) – V(BBMQ) = 1V

.

DC

Note 6: Maximum value within 850MHz to 965MHz.

Note 17: The difference in conversion gain between the spurious signal at

f = 3 • LO – BB versus the conversion gain at the desired signal at f = LO +

BB for BB = 2MHz and LO = 900MHz.

Note 7: An external coupling capacitor is used in the RF output line.

Note 8: At 20MHz offset from the LO signal frequency.

Note 9: At 20MHz offset from the CW signal frequency.

Note 18: The input voltage corresponding to the output P1dB.

55682f

3

LT5568-2

U W

V

CC

= 5V, EN = High, T = 25°C, f = 900MHz,

A LO

TYPICAL PERFOR A CE CHARACTERISTICS

P

= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54V , Baseband Input Frequency f = 2MHz, I&Q 90° shifted. f = f + f (upper

DC BB RF BB LO

LO

sideband selection). P

= –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)

RF, OUT

RF Output Power vs LO Frequency

Supply Current vs Supply Voltage

at 1V Differential Baseband Drive

Voltage Gain vs LO Frequency

P-P

120

110

100

90

–4

–6

0

–2

85°C

–8

–4

25°C

–10

–12

–14

–16

–18

–6

–8

–40°C

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

–10

–12

–14

5V, 85°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

4.5

5

5.5

550 650 750 850 950 1050 1150 1250

LO FREQUENCY (MHz)

SUPPLY VOLTAGE (V)

LO FREQUENCY (MHz)

55682 G03

55682 G02

55682 G01

Output 1dB Compression

vs LO Frequency

Output IP3 vs LO Frequency

Output IP2 vs LO Frequency

26

24

22

20

18

16

14

12

70

65

60

55

50

45

10

8

f

= 2MHz

= 2.1MHz

BB, 1

BB, 2

f

= f

+ f

IM2 BB, 1 BB, 2 LO

= 2MHz

BB, 1

BB, 2

= 2.1MHz

6

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

4

5V, 85°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

2

550 650 750 850 950 1050 1150 1250

LO FREQUENCY (MHz)

55682 G04

55682 G06

55682 G05

LO Feedthrough to RF Output

vs LO Frequency

2 • LO Leakage to RF Output

vs 2 • LO Frequency

3 • LO Leakage to RF Output

vs 3 • LO Frequency

–38

–40

–42

–44

–46

–45

–50

–55

–60

–65

–45

–50

–55

–60

–65

–70

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, 85°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

550 650 750 850 950 1050 1150 1250

LO FREQUENCY (MHz)

1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5

2 • LO FREQUENCY (GHz)

1.65 1.95 2.25 2.55 2.85 3.15 3.45 3.75

3 • LO FREQUENCY (GHz)

55682 G07

55682 G08

55682 G09

55682f

4

LT5568-2

U W

TYPICAL PERFOR A CE CHARACTERISTICS

V

= 5V, EN = High, T = 25°C, f = 900MHz,

A LO

CC

P

= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54V , Baseband Input Frequency f = 2MHz, I&Q 90° shifted. f = f + f (upper

DC BB RF BB LO

LO

sideband selection). P

= –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)

RF, OUT

LO and RF Port Return Loss

vs RF Frequency

Noise Floor vs RF Frequency

Image Rejection vs LO Frequency

–158

–159

–160

–161

–163

–30

0

–10

–20

–30

–40

5V, –40°C

5V, 25°C

LO PORT, EN = LOW

f

= 900MHz

LO

(FIXED)

NO RF

5V, 85°C

–35

–40

–45

–50

–55

4.5V, 25°C

5.5V, 25°C

LO PORT, EN = HIGH,

P

= 0dBm

LO

RF PORT,

EN = LOW

RF PORT,

EN = HIGH,

= 0dBm

5V, –40°C

5V, 25°C

P

LO

5V, 85°C

LO PORT,

4.5V, 25°C

5.5V, 25°C

EN = HIGH,

RF PORT, EN = HIGH, No LO

f

= 100kHz

P

= 10dBm

BB

LO

550 650 750 850 950 1050 1150 1250

RF FREQUENCY (MHz)

LO FREQUENCY (MHz)

RF FREQUENCY (MHz)

55682 G11

55682 G12

55682 G10

LO Feedthrough to RF Output

vs LO Input Power

Image Rejection vs LO Input Power

Voltage Gain vs LO Power

–38

–35

–40

–45

–50

–55

–4

–6

P

BB

= –10dBm

= 100kHz

RF

f

–40

–42

–44

–46

–48

–50

–8

–10

–12

–14

–16

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, 85°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

4.5V, 25°C

5.5V, 25°C

–20 –16 –12

–8

–4

0

4

8

–20 –16 –12 –8

–4

0

4

8

–20 –16 –12

–8

–4

0

4

8

LO INPUT POWER (dBm)

55682 G13

55682 G14

55682 G15

RF CW Output Power, HD2 and

HD3 vs CW Baseband Voltage

and Temperature

RF CW Output Power, HD2 and

HD3 vs CW Baseband Voltage

and Supply Voltage

Output IP3 vs LO Power

–10

–20

–30

–40

–50

–60

–70

–80

10

–10

–20

–30

–40

–50

–60

–70

–80

10

0

25

23

21

19

17

15

13

f

= 2MHz

= 2.1MHz

RF

BB, 1

BB, 2

RF

0

–40°C

25°C

4.5V

5V

–10

–20

–30

–40

–50

–60

–10

–20

–30

–40

–50

–60

25°C

85°C

–40°C

HD3

85°C

HD3

HD2

25°C

–40°C

5V

HD2

5.5V

4.5V

5V, –40°C

5V, 25°C

85°C

5V, 85°C

4.5V, 25°C

5.5V, 25°C

0

1

2

3

4

5

)

0

1

2

3

4

5

)

–20 –16 –12

–8

–4

0

4

8

I AND Q BASEBAND VOLTAGE (V

P–P, DIFF

I AND Q BASEBAND VOLTAGE (V

LO INPUT POWER (dBm)

P–P, DIFF

55682 G16

HD2 = MAX POWER AT f + 2 • f OR f – 2 • f

LO

BB

LO

BB

HD2 = MAX POWER AT f + 2 • f OR f – 2 • f

BB

LO

BB

LO

HD3 = MAX POWER AT f + 3 • f OR f – 3 • f

55682 G17

LO

BB

LO

HD3 = MAX POWER AT f + 3 • f OR f – 3 • f

LO

BB

LO

BB 55682 G18

55682f

5

LT5568-2

U W

V

= 5V, EN = High, T = 25°C, f = 900MHz,

A LO

TYPICAL PERFOR A CE CHARACTERISTICS

CC

P

= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.54V , Baseband Input Frequency f = 2MHz, I&Q 90° shifted. f = f + f (upper

DC BB RF BB LO

LO

sideband selection). P

= –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)

RF, OUT

RF Two-Tone Power (Each Tone),

IM2 and IM3 vs Baseband Voltage

and Temperature

LO Feedthrough to RF Output

vs CW Baseband Voltage

Image Rejection

vs CW Baseband Voltage

10

0

–36

–38

–40

–42

–44

–45

–50

–55

5V, –40°C

5V, 25°C

5V, –40°C

5V, 25°C

5V, 85°C

4.5V, 25°C

5.5V, 25°C

RF

85°C

–40°C

25°C

5V, 85°C

–10

–20

–30

–40

–50

–60

–70

–80

4.5V, 25°C

5.5V, 25°C

–40°C

25°C

85°C

25°C

IM3

–40°C

85°C

IM2

f

= 2MHz, 2.1MHz, 0°

= 2MHz, 2.1MHz, 90°

BBI

BBQ

f

= 100kHz

BB

0.1

1

10

0

1

2

3

4

5

)

0

0.5

1

1.5

2

2.5

3

I AND Q BASEBAND VOLTAGE (V

)

P–P, DIFF, EACH TONE

I AND Q BASEBAND VOLTAGE (V

)

P-P,DIFF

IM2 = POWER AT f + 4.1MHz

55682 G19

55682 G20

LO

IM3 = MAX POWER AT f + 1.9MHz OR f + 2.2MHz

LO

RF Two-Tone Power (Each Tone),

IM2 and IM3 vs Baseband Voltage

and Supply Voltage

Gain Distribution

Noise Floor Distribution

10

0

35

30

25

20

15

10

5

25

20

15

10

5

–40°C

25°C

85°C

–40°C

25°C

85°C

RF

4.5V

–10

–20

–30

–40

–50

–60

–70

–80

5V, 5.5V

4.5V

IM3

5V

5.5V

IM2

4.5V

f

= 2MHz, 2.1MHz, 0°

= 2MHz, 2.1MHz, 90°

BBI

BBQ

0

0.1

1

10

–160.4

–159.6

–159.2

–158.8

–160

–9

–7.5 –7 –6.5 –6 –5.5

–8.5 –8

I AND Q BASEBAND VOLTAGE (V

)

NOISE FLOOR (dBm/Hz)

P–P, DIFF, EACH TONE

GAIN (dB)

55682 G24

55682 G23

IM2 = POWER AT f + 4.1MHz

LO

IM3 = MAX POWER AT f + 1.9MHz OR f + 2.2MHz

LO

LO Leakage Distribution

Image Rejection Distribution

25

20

15

10

5

40

35

30

25

20

15

10

5

–40°C

25°C

85°C

–40°C

25°C

85°C

0

< –70

–62 –58 –54 –50 –46

< –54

–46 –42 –38 –34 –30

–66

–50

55682 G26

IMAGE REJECTION (dBc)

LO LEAKAGE (dBm)

55682 G25

55682f

6

LT5568-2

U

PI FU CTIO S

BBPQ,BBMQ(Pins7,5):BasebandInputsfortheQ-chan-

nel, each 50Ω input impedance. Internally biased at about

0.54V. Applied voltage must stay below 2.5V.

EN (Pin 1): Enable Input. When the enable pin voltage is

higher than 1V, the IC is turned on. When the input voltage

is less than 0.5V, the IC is turned off.

V

(Pins 8, 13): Power Supply. Pins 8 and 13 are con-

GND (Pins 2, 4, 6, 9, 10, 12, 15): Ground. Pins 6, 9, 15

and 17 (exposed pad) are connected to each other inter-

nally. Pins 2 and 4 are connected to each other internally

and function as the ground return for the LO signal. Pins

10 and 12 are connected to each other internally and

function as the ground return for the on-chip RF balun.

For best RF performance, pins 2, 4, 6, 9, 10, 12, 15 and

the Exposed Pad 17 should be connected to the printed

circuit board ground plane.

CC

nected to each other internally. It is recommended to use

0.1µF capacitors for decoupling to ground on each of

these pins.

RF (Pin 11): RF Output. The RF output is an AC-coupled

single-ended output with approximately 50Ω output im-

pedance at RF frequencies. Externally applied DC voltage

should be within the range –0.5V to V + 0.5V in order

to avoid turning on ESD protection diodes.

CC

LO(Pin3):LOInput.TheLOinputisanAC-coupledsingle-

ended input with approximately 50Ω input impedance at

RF frequencies. Externally applied DC voltage should be

BBPI, BBMI (Pins 14, 16): Baseband Inputs for the

I-channel,eachwith50Ωinputimpedance.Internallybiased

at about 0.54V. Applied voltage must stay below 2.5V.

within the range –0.5V to V + 0.5V in order to avoid

CC

Exposed Pad (Pin 17): Ground. This pin must be soldered

to the printed circuit board ground plane.

turning on ESD protection diodes.

55682f

7

LT5568-2

W

BLOCK DIAGRA

V

CC

8

13

LT5568-2

BBPI 14

BBMI 16

V-I

11 RF

0°

90°

BALUN

BBPQ

BBMQ

7

5

1

EN

2

4

6

9

3

10

12

15

17

55682 BD

GND

LO

GND

U

W U U

APPLICATIO S I FOR ATIO

The LT5568-2 consists of I and Q input differential volt-

age-to-current converters, I and Q up-conversion mixers,

an RF output balun, an LO quadrature phase generator

and LO buffers.

External I and Q baseband signals are applied to the dif-

ferential baseband input pins, BBPI, BBMI, and BBPQ,

BBMQ.Thesevoltagesignalsareconvertedtocurrentsand

translated to RF frequency by means of double-balanced

up-converting mixers. The mixer outputs are combined

in an RF output balun, which also transforms the output

impedance to 50Ω. The center frequency of the resulting

RF signal is equal to the LO signal frequency. The LO input

drives a phase shifter which splits the LO signal into in-

phaseandquadratureLOsignals.TheseLOsignalsarethen

applied to on-chip buffers which drive the up-conversion

mixers. Both the LO input and RF output are single-ended,

50Ω-matched and AC coupled.

LT5568-2

RF

= 5V

C

V

CC

BALUN

FROM

Q

LOMI

CM

LOPI

R1A

25Ω

R1B

23Ω

R2B

23Ω

R2A

25Ω

BBPI

R3

R4

12pF

Baseband Interface

V

REF

= 540mV

BBMI

Thebasebandinputs(BBPI,BBMI),(BBPQ,BBMQ)present

adifferentialinputimpedanceofabout100Ω.Ateachofthe

fourbasebandinputs,aﬁrst-orderlowpassﬁlterusing25Ω

55682 F01

GND

Figure1. SimpliﬁedCircuitSchematicoftheLT5568-2

(Only I-Half is Drawn)

55682f

8

LT5568-2

U

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APPLICATIO S I FOR ATIO

and 12pF to ground is incorporated (see Figure 1), which Thebasebandinputsshouldbedrivendifferentially;other-

limits the baseband bandwidth to approximately 330MHz wise, the even-order distortion products will degrade the

(–1dB point). The common mode voltage is about 0.54V overall linearity severely. Typically, a DAC will be the signal

and is approximately constant over temperature.

source for the LT5568-2. Reconstruction ﬁlters should

be placed between the DAC output and the LT5568-2’s

baseband inputs. In Figure 3, a typical baseband interface

schematicforGSMisdrawn.Itshowsagroundreferenced

DACoutputinterfacefollowedbya3rdorderactiveOpAmp

RC lowpass ﬁlter with a 400kHz cutoff frequency (–3dB).

The DAC in this example sources a current from 0mA to

20mA, with a voltage compliance range of at least 0V to

1V. This interface is DC coupled, which allows adjust-

ment of the DAC’s differential output current to minimize

the LO feedthrough. The voltage swing at the LT5568-2

Itisimportantthattheappliedcommonmodevoltagelevel

of the I and Q inputs is about 0.54V in order to properly

bias the LT5568-2. Some I/Q test generators allow setting

the common mode voltage independently. In this case, the

common mode voltage of those generators must be set

to 0.27V to match the LT5568-2 internal bias, because for

DC signals, there is no –6dB source-load voltage division

(see Figure 2).

50Ω

48Ω

baseband inputs is about 2V

, which results in a

P-P,DIFF

0.27V

0.54V

DC

1.2dBm GSM RF output power at 900MHz with noise ﬂoor

of –154.3dBm/Hz at 6MHz offset (= –104.3dBm/100kHz).

The RMS EVM is about 0.6%. The LT1819, which houses

two LT1818s, can be used instead of U2 and U3. The total

current in the positive supply is about 157mA and the

current in the negative supply is about 40mA.

+

DC

0.54V

DC

–

50Ω

GENERATOR

LT5568-2

55682 F02

Figure 2. DC Voltage Levels for a Generator Programmed at

0.27V for a 50Ω Load and the LT5568-2 as a Load

DC

C3

1nF

V

= 4.5 TO 5.25V

CC

RF =

1.2dBm,

GSM

R7

200Ω

R9

249Ω

R14

50Ω

LT5568-2

V

7

CC

+

3

BALUN

0.54V

6

FROM

Q

C

U2

C1

1.2nF

C5

LT1818

10nF

–

LOPI

R11

LOMI

2

249Ω

4

R5

V

SS

CC

0mA to 20mA

53.6Ω

0.54V

R13

499Ω

GND

DAC

R1

45Ω

R2

45Ω

R6

53.6Ω

BBPI

V

7

R12

249Ω

CM

2

–

R3

R4

33Ω

16mA

C2

1.2nF

C6

10nF

U3

LT1818

33Ω

V

0.54V

R15

50Ω

R8

200Ω

R10

249Ω

6

= 540mV

REF

+

BBMI

0.54V

3

4

C4

1nF

V

SS

U1

55682 F03

V

= –2V to –5.25V

SS

GND

Figure 3. LT5568-2 GSM Baseband Interface with 3rd Order Lowpass Filter and Ground Referenced DAC (Only I-Channel is Shown)

55682f

9

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APPLICATIO S I FOR ATIO

Table 1. LO Port Input Impedance vs Frequency for EN = High

LO Section

and P = 0dBm

LO

The internal LO input ampliﬁer performs single-ended to

differential conversion of the LO input signal. Figure 4

shows the equivalent circuit schematic of the LO input.

Frequency

MHz

Input Impedance

S

11

Ω

Mag

Angle

95.0

37.8

–3.41

–31.7

–53.2

–68.7

–79.4

–90.0

500

600

700

800

900

1000

1100

1200

47.5 + j12.1

59.4 + j8.4

0.126

0.115

0.140

0.185

0.232

0.252

0.258

0.297

V

CC

66.2 – j1.14

67.2 – j13.4

61.1 – j23.9

53.3 – j26.8

48.2 – j26.1

42.0 – j27.4

20pF

LO

INPUT

51Ω

5568 F04

If the part is in shutdown mode, the input impedance of

the LO port will be different. The LO input impedance for

EN = Low is given in Table 2.

Figure 4. Equivalent Circuit Schematic of the LO Input

Theinternal,differentialLOsignalisthensplitintoin-phase

and quadrature (90° phase shifted) signals that drive LO

buffer sections. These buffers drive the double balanced I

andQmixers.ThephaserelationshipbetweentheLOinput

and the internal in-phase LO and quadrature LO signals

is ﬁxed, and is independent of start-up conditions. The

internal phase shifters are designed to deliver accurate

quadrature signals. For LO frequencies signiﬁcantly be-

low 650MHz or above 1.25GHz, however, the quadrature

accuracy will diminish, causing the image rejection to

degrade. The LO pin input impedance is about 50Ω, and

the recommended LO input power is 0dBm. For lower

LO input power, the gain, OIP2, OIP3 and noise ﬂoor at

Table 2. LO Port Input Impedance vs Frequency for EN = Low and

P

= 0dBm

LO

Frequency

MHz

Input Impedance

S

11

Ω

Mag

Angle

85.4

49.8

19.6

–6.8

–29.6

–45.5

–65.6

–79.7

500

600

700

800

900

1000

1100

1200

33.6 + j41.3

59.8 + j69.1

140 + j89.8

225 – j62.6

92.9 – j128

39.8 – j95.9

22.8 – j72.7

16.0 – j57.3

0.477

0.539

0.606

0.659

0.704

0.735

0.755

0.763

P

RF

= 4dBm will degrade, especially for P below –2dBm

LO

RF Section

and at T = 85°C. For high LO input power (e.g., +5dBm),

A

Afterup-conversion,theRFoutputsoftheIandQmixersare

combined. An on-chip balun performs internal differential

tosingle-endedoutputconversion,whiletransformingthe

output signal impedance to 50Ω. Table 3 shows the RF

port output impedance vs frequency.

the image rejection will degrade with no improvement in

linearity or gain. Harmonics present on the LO signal can

degrade the image rejection because they can introduce a

small excess phase shift in the internal phase splitter. For

the second (at 1.8GHz) and third harmonics (at 2.7GHz) at

–20dBc,theresultingsignalattheimagefrequencyisabout

–61dBc or lower, corresponding to an excess phase shift

of much less than 1 degree. For the second and third LO

harmonics at –10dBc, the introduced signal at the image

frequencyisabout–51dBc.Higherharmonicsthanthethird

will have less impact. The LO return loss typically will be

betterthan11dBoverthe700MHzto1.05GHzrange.Table

1 shows the LO port input impedance vs frequency.

Table 3. RF Port Output Impedance vs Frequency for EN = High

and P = 0dBm

LO

Frequency

MHz

Input Impedance

S

22

Ω

Mag

Angle

164.2

141.3

117.5

90.6

–94.7

–117.0

–130.7

–141.6

500

600

700

800

900

1000

1100

1200

22.0 + j5.7

28.2 + j12.5

38.8 + j14.8

49.4 + j7.2

49.3 – j5.1

42.5 – j11.1

36.7 – j11.7

33.0 – j10.3

0.395

0.317

0.206

0.072

0.051

0.143

0.202

0.238

55682f

10

LT5568-2

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APPLICATIO S I FOR ATIO

The RF output S with no LO power applied is given in Note that an ESD diode is connected internally from the

22

Table 4.

RF output to ground (see Figure 5). For strong output

RF signal levels (higher than 3dBm), this ESD diode can

degrade the linearity performance if the 50Ω termination

impedanceisconnecteddirectlytoground.Topreventthis,

a coupling capacitor can be inserted in the RF output line.

This is strongly recommended during a 1dB compression

measurement.

Table 4. RF Port Output Impedance vs Frequency for EN = High

and No LO Power Applied

Frequency

MHz

Input Impedance

S

22

Ω

Mag

Angle

164.0

500

600

22.7 + j5.6

29.7 + j11.6

40.5 + j11.6

47.3 + j2.2

44.1 – j6.7

38.2 – j9.8

34.0 – j9.4

31.5 – j7.8

0.381

0.290

0.164

0.037

0.094

0.171

0.218

0.245

142.0

700

121.9

800

139.6

Enable Interface

900

–126.9

–133.9

–143.1

–151.6

Figure 6 shows a simpliﬁed schematic of the EN pin

interface. The voltage necessary to turn on the LT5568-2

is 1V. To disable (shut down) the chip, the enable voltage

must be below 0.5V. If the EN pin is not connected, the

chip is disabled. This EN = Low condition is assured by

the 75k on-chip pull-down resistor. It is important that

1000

1100

1200

For EN = Low the S is given in Table 5.

22

Table 5. RF Port Output Impedance vs Frequency for EN = Low

the voltage at the EN pin does not exceed V by more

CC

Frequency

MHz

Input Impedance

S

22

than 0.5V. If this should occur, the supply current could

be sourced through the EN pin ESD protection diodes,

which are not designed to carry the full supply current,

and damage may result.

Ω

Mag

Angle

164.9

142.5

118.1

87.4

500

600

21.2 + j5.4

26.6 + j12.5

36.6 + j16.6

49.2 + j11.6

52.9 – j2.0

46.4 – j11.2

39.3 – j13.2

34.4 – j12.1

0.409

0.340

0.241

0.116

0.034

0.121

0.188

0.231

700

800

900

–33.1

–101.1

–120.6

–133.8

1000

1100

1200

V

CC

V

CC

EN

75k

25k

21pF

RF

OUTPUT

7nH

1pF

51Ω

55682 F06

55682 F05

Figure 6. EN Pin Interface

Figure 5. Equivalent Circuit Schematic of the RF Output

55682f

11

LT5568-2

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APPLICATIO S I FOR ATIO

Evaluation Board

R1 (optional) limits the EN pin current in the event that

the EN pin is pulled high while the V inputs are low. In

CC

Figure 7 shows the evaluation board schematic. A good

ground connection is required for the exposed pad. If this

is not done properly, the RF performance will degrade. Ad-

ditionally,theexposedpadprovidesheatsinkingforthepart

and minimizes the possibility of the chip overheating.

Figures 8 and 9 the silk screens and the PCB board layout

are shown.

J1

J2

BBMI

BBPI

V

CC

C2

16

BBMI GND BBPI

EN

15

14

13

100nF

R1

V

CC

100Ω

1

2

3

4

12

GND

RF

V

EN

CC

J3

11

10

9

RF

OUT

GND

LO

J4

LO

IN

LT5568-2

GND

17

BBMQ GND BBPQ

V

CC

5

6

7

8

C1

100nF

J5

J6

BBMQ

GND

BBPQ

BOARD NUMBER: DC1178A

55682 F07

Figure 7. Evaluation Circuit Schematic

Figure 8. Component Side of Evaluation Board

55682 F09

Figure 9. Bottom Side of Evaluation Board

55682f

12

LT5568-2

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APPLICATIO S I FOR ATIO

Application Measurements

Because of the LT5568-2’s very high dynamic range, the

test equipment can limit the accuracy of the ACPR mea-

surement. See Application Note 99. Consult the factory

for advice on the ACPR measurement, if needed.

The LT5568-2 is recommended for base-station applica-

tionsusingvariousmodulationformats.Figure10showsa

typicalapplication.Figure11showstheACPRperformance

for CDMA2000 using 1- and 3-carrier modulation. Figures

12 and 13 illustrate the 1- and 3-carrier CDMA2000 RF

spectrum. To calculate ACPR, a correction is made for the

spectrum analyzer noise ﬂoor. If the output power is high,

theACPRwillbelimitedbythelinearityperformanceofthe

part. If the output power is low, the ACPR will be limited

by the noise performance of the part. In the middle, an

optimum ACPR is observed.

TheACPRperformanceissensitivetotheamplitudematch

of the BBPI and BBMI (or BBPQ and BBMQ) inputs. This

is because a difference in AC current amplitude will give

rise to a difference in amplitude between the even-order

harmonic products generated in the internal V-I converter.

As a result, they will not cancel out entirely. Therefore, it

is important to keep the currents in those pins exactly

–50

–60

–70

–80

–90

–125

–135

–145

–155

–165

5V

100nF

DOWNLINK TEST MODEL 64 DPCH 1-CH.

ACPR

V

CC 8, 13

LT5568-2

14

16

x2

RF = 850MHz

TO 965MHz

I-DAC

V-I

I-CHANNEL

3-CH. ACPR

11

PA

0°

1

EN

90°

BALUN

3-CH. AltCPR

1-CH. AltCPR

Q-CHANNEL

V-I

7

5

Q-DAC

3-CH. NOISE

1-CH. NOISE

BASEBAND

GENERATOR

55682 F10

3

VCO/SYNTHESIZER

2, 4, 6, 9, 10, 12, 15, 17

–30

–25

–20

–15

–10

–5

RF OUTPUT POWER PER CARRIER (dBm)

55682 F11

Figure 10. 850MHz to 965MHz Direct

Conversion Transmitter Application

Figure 11. ACPR, AltCPR and Noise

CDMA2000 Modulation

–30

–40

DOWNLINK TEST

DOWNLINK

TEST

MODEL 64

DPCH

–40

–50

–60

–70

–80

–90

MODEL 64 DPCH

–50

–60

–70

–80

UNCORRECTED

SPECTRUM

–90

CORRECTED

SPECTRUM

UNCORRECTED

SPECTRUM

–100

–110

–120

–130

–100

–110

–120

–130

CORRECTED

SPECTRUM

SPECTRUM ANALYSER

NOISE FLOOR

SPECTRUM ANALYSER NOISE FLOOR

896.25 897.75 899.25 900.75 902.25 903.75

894

896

898

900

902

904

906

RF FREQUENCY (MHz)

55682 F13

55682 F12

Figure 12. 1-Carrier CDMA2000 Spectrum

Figure 13. 3-Carrier CDMA2000 Spectrum

55682f

13

LT5568-2

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APPLICATIO S I FOR ATIO

the same (but of opposite sign). The current will enter change.ThisisillustratedinFigure14.TheLOfeedthrough

the LT5568-2’s common-base stage, and will ﬂow to the and image rejection can also change as a function of the

mixer upper switches. This can be seen in Figure 1 where baseband drive level, as is depicted in Figure 15. In Figure

the internal circuit of the LT5568-2 is drawn.

16 the GSM EVM and noise performance vs RF output

power is drawn.

After calibration when the temperature changes, the LO

feedthrough and the image rejection performance will

–50

10

CALIBRATED WITH P = –10dBm

RF

–40°C

P

85°C

0

–10

–20

–30

–40

–50

–60

–70

–80

–90

RF

IMAGE REJECTION

25°C

–60

–70

–80

–90

LO FEED-

THROUGH

LOFT

85°C

IR

–40°C

85°C

25°C

–40°C

EN = High

25°C

f

= 900MHz

= f + f

LO

V

f

BBQ

= 5V

= 2MHz, 0°

= 2MHz, 90°

LO

CC

RF BB LO

P

BBI

= 0dBm

f

–40 –20

0

20

40

60

80

0

1

2

3

4

5

TEMPERATURE (°C)

I AND Q BASEBAND VOLTAGE (V

)

P-P, DIFF

55682 F14

f

V

= 2MHz, 0°

= 2MHz, 90°

= 5V

f

= 900MHz

= f + f

RF BB LO

LO

BBI

BBQ

LO

Figure 14. LO Feedthrough and Image Rejection

vs Temperature after Calibration at 25°C

f

P

= 0dBm

CC

EN = High

Figure 15. LO Feedthrough and Image Rejection

vs Baseband Drive Voltage after Calibration at 25°C

5

4

–96

–98

3

–100

–102

NOISE

2

1

0

EVM

–104

–106

–10 –8 –6 –4 –2

0

2

4

6

GSM RF OUTPUT POWER (dBm)

55682 F16

Figure 16. GSM EVM and Noise vs RF Output Power at 900MHz

55682f

14

LT5568-2

U

PACKAGE DESCRIPTIO

UF Package

16-Lead Plastic QFN (4mm × 4mm)

(Reference LTC DWG # 05-08-1692)

0.72 0.05

4.35 0.05

2.90 0.05

2.15 0.05

(4 SIDES)

PACKAGE OUTLINE

0.30 0.05

0.65 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

BOTTOM VIEW—EXPOSED PAD

PIN 1 NOTCH R = 0.20 TYP

OR 0.35 × 45° CHAMFER

0.75 0.05

R = 0.115

TYP

4.00 0.10

(4 SIDES)

15

16

0.55 0.20

PIN 1

TOP MARK

(NOTE 6)

1

2

2.15 0.10

(4-SIDES)

(UF16) QFN 10-04

0.200 REF

0.30 0.05

0.65 BSC

0.00 – 0.05

NOTE:

1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)

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

55682f

InformationfurnishedbyLinearTechnologyCorporationisbelievedtobeaccurateandreliable.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.

15

LT5568-2

RELATED PARTS

PART NUMBER DESCRIPTION

Infrastructure

COMMENTS

LT5514

LT5515

LT5516

Ultralow Distortion, IF Ampliﬁer/ADC Driver with 850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range

Digitally Controlled Gain

1.5GHz to 2.5GHz Direct Conversion Quadrature 20dBm IIP3, Integrated LO Quadrature Generator

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0.8GHz to 1.5GHz Direct Conversion Quadrature 21.5dBm IIP3, Integrated LO Quadrature Generator

Demodulator

LT5517

LT5518

40MHz to 900MHz Quadrature Demodulator

21dBm IIP3, Integrated LO Quadrature Generator

1.5GHz to 2.4GHz High Linearity Direct

Quadrature Modulator

22.8dBm OIP3 at 2GHz, –158.2dBm/Hz Noise Floor, 50Ω Single-Ended LO and RF

Ports, 4-Ch W-CDMA ACPR = –64dBc at 2.14GHz

LT5519

LT5520

LT5521

LT5522

0.7GHz to 1.4GHz High Linearity Upconverting

Mixer

17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50Ω Matching,

Single-Ended LO and RF Ports Operation

1.3GHz to 2.3GHz High Linearity Upconverting

Mixer

15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50Ω Matching,

Single-Ended LO and RF Ports Operation

10MHz to 3700MHz High Linearity Upconverting 24.2dBm IIP3 at 1.95GHz, NF = 12.5dB, 3.15V to 5.25V Supply, Single-Ended LO

Mixer

Port Operation

600MHz to 2.7GHz High Signal Level

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4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB, 50Ω Single-Ended RF

and LO Ports

LT5525

LT5526

High Linearity, Low Power Downconverting Mixer Single-Ended 50Ω RF and LO Ports, 17.6dBm IIP3 at 1900MHz, I = 28mA

CC

High Linearity, Low Power Downconverting Mixer 3V to 5.3V Supply, 16.5dBm IIP3, 100kHz to 2GHz RF, NF = 11dB, I = 28mA,

CC

–65dBm LO-RF Leakage

LT5527

LT5528

LT5557

LT5558

400MHz to 3.7GHz High Signal Level

Downconverting Mixer

IIP3 = 23.5dBm and NF = 12.5dB at 1900MHz, 4.5V to 5.25V Supply, I = 78mA

CC

1.5GHz to 2.4GHz High Linearity Direct

Quadrature Modulator

21.8dBm OIP3 at 2GHz, –159.3dBm/Hz Noise Floor, 50Ω, 0.5V Baseband Interface,

DC

4-Ch W-CDMA ACPR = –66dBc at 2.14GHz

400MHz to 3.8GHz, 3.3V, Very High Linearity

Downconverting Mixer

IIP3 = 24.7dBm at 1.9GHz, 23.5dBm at 3.5GHz, Conversion Gain = 2.9dB at 1.9GHz,

3.3V at 82mA, –3dB LO Drive

600MHz to 1100MHz High Linearity Direct

Quadrature Modulator

22.4dBm OIP3 at 900MHz, –158dBm/Hz Noise Floor, 3kΩ, 2.1V Baseband

DC

Interface, 3-Ch CDMA2000 ACPR = –70.4dBc at 900MHz

LT5560

LT5568

Ultra-Low Power Active Mixer

10mA Supply Current, 10dBm IIP3, 10dB NF, Usable as Up- or Down-Converter

700MHz to 1050MHz High Linearity Direct

Quadrature Modulator

22.9dBm OIP3 at 850MHz, –160.3dBm/Hz Noise Floor, 50Ω, 0.5V Baseband

DC

Interface, 3-Ch CDMA2000 ACPR = –71.4dBc at 850MHz

LT5572

LT5575

1.5GHz to 2.5GHz High Linearity Direct

Quadrature Modulator

21.6dBm OIP3 at 2GHz, –158.6dBm/Hz Noise Floor, High-Ohmic 0.5V Baseband

DC

Interface, 4-Ch W-CDMA ACPR = –67.7dBc at 2.14GHz

800MHz to 2.7GHz High Linearity Direct

Conversion Quadrature Demodulator

28dBm IIP3 and 13.2dBm P1dB at 900MHz, 60dBm IIP2 and 12.7dB NF

at 1900MHz

RF Power Detectors

LTC^®5505

LTC5507

LTC5508

LTC5509

LTC5530

LTC5531

LTC5532

LT5534

RF Power Detectors with >40dB Dynamic Range 300MHz to 3GHz, Temperature Compensated, 2.7V to 6V Supply

100kHz to 1000MHz RF Power Detector

300MHz to 7GHz RF Power Detector

100kHz to 1GHz, Temperature Compensated, 2.7V to 6V Supply

44dB Dynamic Range, Temperature Compensated, SC70 Package

36dB Dynamic Range, Low Power Consumption, SC70 Package

300MHz to 3GHz RF Power Detector

300MHz to 7GHz Precision RF Power Detector

Precision V

Offset Control, Shutdown, Adjustable Gain

Offset Control, Shutdown, Adjustable Offset

Offset Control, Adjustable Gain and Offset

OUT

50MHz to 3GHz Log RF Power Detector with

60dB Dynamic Range

1dB Output Variation over Temperature, 38ns Response Time

LTC5536

LT5537

Precision 600MHz to 7GHz RF Detector with Fast 25ns Response Time, Comparator Reference Input, Latch Enable Input, –26dBm to

Comparator

+12dBm Input Range

Wide Dynamic Range Log RF/IF Detector

Low Frequency to 800MHz, 83dB Dynamic Range, 2.7V to 5.25V Supply

55682f

LT 0307 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

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型号：	LT5568-2EUF-PBF
厂家：	Linear
描述：	GSM/EDGE Optimized, High Linearity Direct Quadrature Modulator GSM / EDGE优化，高线性度直接正交调制器 GSM
文件：	总16页 (文件大小：300K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT5568-2EUF-PBF [Linear]

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