LINER LT5528 1.5ghz to 2.4ghz high linearity direct quadrature modulator Datasheet

LT5528
1.5GHz to 2.4GHz
High Linearity Direct
Quadrature Modulator
DESCRIPTIO
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FEATURES
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The LT®5528 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
PHS, GSM, EDGE, TD-SCDMA, CDMA, CDMA2000,
W-CDMA and other systems. It may also be configured
as an image reject up-converting 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.
Direct Conversion to 1.5GHz to 2.4GHz
High OIP3: 21.8dBm at 2GHz
Low Output Noise Floor at 5MHz Offset:
No RF: –159.3dBm/Hz
POUT = 4dBm: –151.8dBm/Hz
4-Ch W-CDMA ACPR: –66dBc at 2.14GHz
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: –42dBm at 2GHz
High Image Rejection: 45dB at 2GHz
16-Lead QFN 4mm × 4mm Package
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APPLICATIO S
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Infrastructure Tx for DCS, PCS and UMTS Bands
Image Reject Up-Converters for PCS and UMTS
Bands
Low-Noise Variable Phase-Shifter for 1.5GHz to
2.4GHz Local Oscillator Signals
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
1.5GHz to 2.4GHz Direct Conversion Transmitter Application
with LO Feed-Through and Image Calibration Loop
5V
VCC 8, 13
–55
V-I
EN
90°
5
PA
0°
1
7
Q-DAC
11
Q-CHANNEL
BALUN
LO FEED-THROUGH CAL OUT
V-I
IMAGE CAL OUT
CAL
BASEBAND
DSP
4-CH ACPR
–65
2-CH AltCPR
–70
–150
2-CH ACPR
4-CH AltCPR
–155
1-CH ACPR
1-CH AltCPR
–75 4-CH NOISE
2, 4, 6, 9, 10, 12, 15, 17
–160
3
VCO/SYNTHESIZER
–80
–42
ADC
–140
–145
–60
I-CHANNEL
ACPR, AltCPR (dBc)
16
DOWNLINK TEST MODEL 64 DPCH
RF = 1.5GHz
TO 2.4GHz
1-CH NOISE
–38
–34
–30
–26
–22
–18
NOISE FLOOR AT 30MHz OFFSET (dBm/Hz)
LT5528
14
I-DAC
W-CDMA ACPR, AltCPR and Noise vs RF Output
Power at 2140MHz for 1, 2 and 4 Channels
–165
–14
RF OUTPUT POWER PER CARRIER (dBm)
5528 TA01a
5528 TA01b
5528f
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LT5528
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ABSOLUTE
AXI U RATI GS
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W
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PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
VCC
BBPI
BBMI
GND
TOP VIEW
Supply Voltage .........................................................5.5V
Common-Mode Level of BBPI, BBMI and
BBPQ, BBMQ .......................................................2.5V
Operating Ambient Temperature
(Note 2) ...............................................–40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
Voltage on Any Pin
Not to Exceed...................... –500mV to VCC + 500mV
16 15 14 13
EN 1
LT5528EUF
12 GND
GND 2
11 RF
17
LO 3
10 GND
GND 4
6
7
8
BBMQ
GND
BBPQ
VCC
9
5
GND
UF PART
MARKING
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
5528A
TJMAX = 125°C, θJA = 37°C/W
EXPOSED PAD IS GROUND (PIN 17)
MUST BE SOLDERED TO PCB.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2GHz, fRF = 2.002GHz, PLO = 0dBm.
BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper sideband selection).
PRF, OUT = –10dBm, unless otherwise noted. (Note 3)
SYMBOL
RF Output (RF)
fRF
S22, ON
S22, OFF
NFloor
GP
GV
POUT
G3LO vs LO
OP1dB
OIP2
OIP3
IR
LOFT
LO Input (LO)
fLO
PLO
S11, ON
S11, OFF
NFLO
GLO
IIP3LO
PARAMETER
CONDITIONS
RF Frequency Range
RF Frequency Range
–3dB Bandwidth
–1dB Bandwidth
RF Output Return Loss
RF Output Return Loss
RF Output Noise Floor
EN = High (Note 6)
EN = Low (Note 6)
No Input Signal (Note 8)
POUT = 4dBm (Note 9)
POUT = 4dBm (Note 10)
POUT/PIN, I&Q
20 • Log (VOUT, 50Ω/VIN, DIFF, I or Q)
1VP-P DIFF CW Signal, I and Q
(Note 17)
(Note 7)
(Notes 13, 14)
(Notes 13, 15)
(Note 16)
EN = High, PLO = 0dBm (Note 16)
EN = Low, PLO = 0dBm (Note 16)
Conversion Power Gain
Conversion Voltage Gain
Absolute Output Power
3 • LO Conversion Gain Difference
Output 1dB Compression
Output 2nd Order Intercept
Output 3rd Order Intercept
Image Rejection
Carrier Leakage
(LO Feed-Through)
LO Frequency Range
LO Input Power
LO Input Return Loss
LO Input Return Loss
LO Input Referred Noise Figure
LO to RF Small Signal Gain
LO Input 3rd Order Intercept
MIN
MAX
1.5 to 2.4
1.7 to 2.2
1.5 to 2.4
0
–17
–5.5
14.4
20.4
–10
UNITS
GHz
GHz
–15
–12
–159.3
–151.8
–151.8
–6.5
–6
–2.1
–28
7.9
49
21.8
–45
–42
–57.8
–10
EN = High (Note 6)
EN = Low (Note 6)
(Note 5) at 2GHz
(Note 5) at 2GHz
(Note 5) at 2GHz
TYP
dB
dB
dBm/Hz
dBm/Hz
dBm/Hz
dB
dB
dBm
dB
dBm
dBm
dBm
dBc
dBm
dBm
5
GHz
dBm
dB
dB
dB
dB
dBm
5528f
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LT5528
ELECTRICAL CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2GHz, fRF = 2.002GHz, PLO = 0dBm.
BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency = 2MHz, I&Q 90° shifted (upper sideband selection).
PRF, OUT = –10dBm, unless otherwise noted. (Note 3)
SYMBOL
PARAMETER
Baseband Inputs (BBPI, BBMI, BBPQ, BBMQ)
BWBB
Baseband Bandwidth
VCMBB
RIN, SE
PLO2BB
IP1dB
ΔGI/Q
ΔϕI/Q
Power Supply (VCC)
VCC
ICC, ON
DC Common Mode Voltage
Single-Ended Input Resistance
Carrier Feed-Through on BB
Input 1dB Compression Point
I/Q Absolute Gain Imbalance
I/Q Absolute Phase Imbalance
CONDITIONS
MIN
–3dB Bandwidth
(Note 4)
(Note 4)
POUT = 0 (Note 4)
Differential Peak-to-Peak (Note 7)
Supply Voltage
Supply Current
ICC, OFF
Supply Current, Sleep Mode
tON
Turn-On Time
tOFF
Turn-Off Time
Enable (EN), Low = Off, High = On
Enable
Input High Voltage
Input High Current
Sleep
Input Low Voltage
4.5
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Specifications over the –40°C to 85°C temperature range are
assured by design, characterization and correlation with statistical process
controls.
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) = 1VDC, V(BBPQ) – V(BBMQ) = 1VDC.
Note 6: Maximum value within –1dB bandwidth.
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.
MAX
400
0.525
45
–40
3.2
0.05
0.5
EN = High
EN = 0V
EN = Low to High (Note 11)
EN = High to Low (Note 12)
EN = High
EN = 5V
EN = Low
TYP
UNITS
MHz
V
Ω
dBm
VP-P, DIFF
dB
Deg
5
5.25
V
125
0.05
0.25
1.3
145
50
mA
µA
µs
µs
1.0
240
0.5
V
µA
V
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 feed-through nulling (unadjusted).
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 = 2GHz.
5528f
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LT5528
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TYPICAL PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO
= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper
sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)
Gain and Output 1dB
Compression vs LO Frequency
and Supply Voltage
Gain and Output 1dB Compression
vs LO Frequency and Temperature
Supply Current vs Supply Voltage
140
10
10
85°C
25°C
120
–40°C
110
0
–5
–10
GAIN
–15
5.0
SUPPLY VOLTAGE (V)
–20
1.3
5.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
5528 G01
OIP3 (dBm)
–148
OIP3
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
–150
16
–152
14
–154
12
10
NOISE FLOOR
NO BASEBAND SIGNAL
20MHz OFFSET NOISE
–156
8
6
1.3
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
2.5
–20
1.3
2.7
22
20
18
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
OIP3
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
–148
–150
–152
14
–154
12
10
–160
8
6
1.3
NOISE FLOOR
NO BASEBAND SIGNAL
20MHz OFFSET NOISE
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
–156
–158
2.5
–162
2.7
5528 G05
2.7
65
60
55
50
45
40
–160
1.5
2.5
Output IP2 vs LO Frequency
16
–158
–162
2.7
5528 G04
4.5V
5V
5.5V
5528 G03
NOISE FLOOR (dBm/Hz)
18
2.5
–142
4.5V
5V –144
5.5V
–146
24
NOISE FLOOR (dBm/Hz)
20
26
OIP3 (dBm)
22
GAIN
Output IP3 and Noise Floor vs
LO Frequency and Supply Voltage
–142
–40°C
25°C –144
85°C
–146
24
–10
5528 G02
Output IP3 and Noise Floor vs
LO Frequency and Temperature
26
–5
–15
–40°C
25°C
85°C
1.5
OP1dB
0
OIP2 (dBm)
100
4.5
5
OP1dB
GAIN (dB), OP1dB (dBm)
GAIN (dB), OP1dB (dBm)
SUPPLY CURRENT (mA)
5
130
35
1.3
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
fIM2 = fBB,1 + fBB,2 + fLO
fBB, 1 = 2MHz
2.5
2.7
fBB, 2 = 2.1MHz
5528 G06
5528f
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LT5528
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TYPICAL PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO
= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper
sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)
2 • LO Leakage to RF Output vs
2 • LO Frequency
3 • LO Leakage to RF Output vs
3 • LO Frequency
–25
–30
LO to RF Output Feed-Through vs
LO Frequency
–30
–36
–35
–38
–40
–45
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
–50
–55
2.6
3.0
3.4 3.8 4.2 4.6 5.0
2 • LO FREQUENCY (GHz)
5.4
–44
–50
–46
–55
–60
–65
–70
3.9
4.5
0.3
ABSOLUTE I/Q GAIN IMBALANCE (dB)
IMAGE REJECTION (dBc)
–32
–34
–36
–38
–40
–42
–44
–46
–48
1.3
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
2.5
2.7
5528 G10
8.1
–54
1.3
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
Absolute I/Q Phase Imbalance vs
LO Frequency
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
0.2
0.1
0
1.3
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
2.5
2.7
2.5
5528 G09
Absolute I/Q Gain Imbalance vs
LO Frequency
–26
–30
–52
5528 G08
Image Rejection vs LO Frequency
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
–50
5.1 5.7 6.3 6.9 7.5
3 • LO FREQUENCY (GHz)
5528 G07
–28
–48
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
2.7
5528 G11
5
ABSOLUTE I/Q PHASE IMBALANCE (DEG)
–40
–42
–45
LOFT (dBm)
P(3 • LO) (dBm)
P(2 • LO) (dBm)
–40
–35
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
4
3
2
1
0
1.3
1.5
1.7 1.9 2.1 2.3
LO FREQUENCY (GHz)
2.5
2.7
5528 G12
5528f
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LT5528
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TYPICAL PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO
= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper
sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)
Gain vs LO Power
RF Output Power, HD2 and HD3
at 2140MHz vs Baseband Voltage
and Temperature
Output IP3 vs LO Power
–4
22
–10
–6
–20
–12
–14
12
10
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
–16
–18
–16
–12
–8
–4
0
LO POWER (dBm)
4
HD2, HD3 (dBc)
14
OIP3 (dBm)
GAIN (dB)
16
–10
8
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
6
4
2
0
–20
8
–16
–12
–8
–4
0
LO POWER (dBm)
4
–30
–10
–40
–20
HD2
–50
–30
–60
–40°C –40
25°C
85°C
–50
1
2
3
4
5
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
–70
8
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
5528 G13
0
HD3
0
RF OUTPUT POWER (dBm)
18
–8
–20
–20
10
RF
20
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB
HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB
5528 G14
5528 G15
RF Output Power, HD2 and HD3
at 2140MHz vs Baseband Voltage
and Supply Voltage
–10
LO Feed-Through and Image
Rejection at 2140MHz vs Baseband
Voltage and Temperature
10
–25
–40°C
25°C
85°C
RF
0
HD2, HD3 (dBc)
–30
–10
–40
–20
HD2
–50
–30
–60
–70
0
4.5V –40
5V
5.5V
–50
1
2
3
4
5
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
HD2 = MAX POWER AT fLO + 2 • fBB OR fLO – 2 • fBB
HD3 = MAX POWER AT fLO + 3 • fBB OR fLO – 3 • fBB
RF OUTPUT POWER (dBm)
HD3
–30
LOFT (dBm), IR (dBc)
–20
LOFT
–35
–40
IR
–45
–50
0
1
2
3
4
5
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
5528 G17
5528 G16
5528f
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LT5528
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = High, TA = 25°C, fLO = 2.14GHz, PLO
= 0dBm. BBPI, BBMI, BBPQ, BBMQ inputs 0.525VDC, Baseband Input Frequency fBB = 2MHz, I&Q 90° shifted. fRF = fBB + fLO (upper
sideband selection). PRF, OUT = –10dBm (–10dBm/tone for 2-tone measurements), unless otherwise noted. (Note 3)
LO Feed-Through and Image
Rejection at 2140MHz vs Baseband
Voltage and Supply Voltage
4.5V
5V
5.5V
–2
–35
–40
–20
–30
RF PORT,
EN = HIGH,
PLO = OFF
IR
–45
–50
1
2
3
4
5
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
–50
1.3
LO PORT,
EN = HIGH
RF PORT,
EN = HIGH,
PLO = 0dBm
–40
0
0
LO PORT, EN = LOW
–10
LOFT
S11 (dB)
LOFT (dBm), IR (dBc)
–30
0
1.5
RF OUTPUT POWER (dBm)
–25
RF Output Power vs
RF Frequency at 1VP-P
Differential Baseband Drive
LO and RF Port Return Loss vs
RF Frequency
–4
–6
–8
–10
RF PORT,
EN = LOW
1.7 1.9 2.1 2.3
RF FREQUENCY (GHz)
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
–12
2.5
2.7
5528 G19
VBBI = 1VP-P, DIFF
VBBQ = 1VP-P, DIFF
–14
1.3 1.5 1.7 1.9 2.1 2.3
RF FREQUENCY (GHz)
2.5
2.7
5528 G20
5528 G18
U
U
U
PI FU CTIO S
EN (Pin 1): Enable Input. When the EN 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.
BBPQ, BBMQ (Pins 7, 5): Baseband Inputs for the Q-channel, each 45Ω input impedance. Internally biased at about
0.525V. Applied voltage must stay below 2.5V.
GND (Pins 2, 4, 6, 9, 10, 12, 15): Ground. Pins 6, 9, 15
and 17 (exposed pad) are connected to each other internally. 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.
VCC (Pins 8, 13): Power Supply. Pins 8 and 13 are connected to each other internally. It is recommended to use
0.1µF capacitors for decoupling to ground on each of
these pins.
LO (Pin 3): LO Input. The LO input is an AC-coupled singleended input with approximately 50Ω input impedance at
RF frequencies. Externally applied DC voltage should be
within the range –0.5V to VCC + 0.5V in order to avoid
turning on ESD protection diodes.
RF (Pin 11): RF Output. The RF output is an AC-coupled
single-ended output with approximately 50Ω output impedance at RF frequencies. Externally applied DC voltage
should be within the range –0.5V to VCC + 0.5V in order
to avoid turning on ESD protection diodes.
BBPI, BBMI (Pins 14, 16): Baseband Inputs for the
I-channel, each with 45Ω input impedance. These pins are
internally biased at about 0.525V. Applied voltage must
stay below 2.5V.
Exposed Pad (Pin 17): Ground. This pin must be soldered
to the printed circuit board ground plane.
5528f
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LT5528
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BLOCK DIAGRA
VCC
8
13
LT5528
BBPI 14
V-I
BBMI 16
11 RF
0°
90°
BALUN
BBPQ 7
1 EN
V-I
BBMQ 5
2
4
6
9
3
LO
GND
10
12
15
17
5528 BD
GND
U
U
W
U
APPLICATIO S I FOR ATIO
The LT5528 consists of I and Q input differential voltageto-current converters, I and Q up-conversion mixers, an
RF output balun, an LO quadrature phase generator and
LO buffers.
LT5528
RF
C
VCC = 5V
BALUN
FROM
Q
LOMI
R1A
20Ω
R1B
23Ω
LOPI
R2B
23Ω
BBPI
R2A
20Ω
CM
12pF
R3
R4
12pF
Baseband Interface
VREF = 0.52V
BBMI
5528 F01
GND
Figure 1. Simplified Circuit Schematic of the LT5528
(Only I-Half is Drawn)
External I and Q baseband signals are applied to the differential baseband input pins, BBPI, BBMI, and BBPQ,
BBMQ. These voltage signals are converted to currents and
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 inphase and quadrature LO signals. These LO signals are then
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.
The baseband inputs (BBPI, BBMI), (BBPQ, BBMQ) present
a differential input impedance of about 90Ω. At each of the
four baseband inputs, a first-order low-pass filter using 20Ω
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and 12pF to ground is incorporated (see Figure 1), which
limits the baseband bandwidth to approximately 330MHz
(–1dB point). The common-mode voltage is about 0.52V
and is approximately constant over temperature.
It is important that the applied common-mode voltage level
of the I and Q inputs is about 0.52V in order to properly
bias the LT5528. 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 0.26V to match the LT5528 internal bias, because for
DC signals, there is no –6dB source-load voltage division
(see Figure 2).
50Ω
+
–
50Ω
0.26VDC
0.52VDC
50Ω
+
–
GENERATOR
45Ω
0.52VDC
0.52VDC
0.52VDC
GENERATOR
+
–
LT5528
5528 F02
Figure 2. DC Voltage Levels for a Generator Programmed at
0.26VDC for a 50Ω Load and the LT5528 as a Load
It is recommended that the part be driven differentially;
otherwise, the even-order distortion products will degrade the overall linearity severely. Typically, a DAC will
be the signal source for the LT5528. To prevent aliasing,
a filter should be placed between the DAC output and the
LT5528’s baseband inputs. In Figure 3, an example interface
schematic shows a commonly used DAC output interface
followed by a passive 5th order ladder filter. The DAC in
this example sources a current from 0mA to 20mA. The
interface may be DC coupled. This allows adjustment of
the DAC’s differential output current to minimize the LO
feed-through. Optionally, transformer T1 can be inserted
to improve the current balance in the BBPI and BBMI pins.
This will improve the second-order distortion performance
(OIP2).
The maximum single sideband CW RF output power at
2GHz using 20mA drive to both I and Q channels with the
configuration shown in Figure 3 is about –2.5dBm. The
maximum CW output power can be increased by connecting resistors R5 and R6 to –5V instead of GND, and
changing their values to 550Ω. In that case, the maximum
single sideband CW RF output power at 2GHz will be about
2.3dBm. In addition, the ladder filter component values
require adjustment for a higher source impedance.
VCC = 5V
LT5528
BALUN
RF = –2.5dBm, MAX
C
LOMI
0.5V
0mA TO 20mA
L1A
L2A
C2
GND
R6, 50Ω
L1B
L2B
R4
R3
C3
VREF = 0.52V
•
0mA TO 20mA
R2
45Ω
R1
45Ω
CM
•
C1
BBPI
T1
1:1
R5, 50Ω
DAC
OPTIONAL
LOPI
BBMI
0.5V
5528 F03
GND
Figure 3. LT5528 5th Order Filtered Baseband Interface with Common DAC (Only I-Channel is Shown)
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Table 1. LO Port Input Impedance vs Frequency for EN = High
LO Section
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.
VCC
20pF
LO
INPUT
ZIN ≈ 57Ω
Frequency
MHz
1000
1400
1600
1800
2000
2200
2400
2600
Input Impedance
Ω
49.9 + j18.5
68.1 + j8.8
71.0 + j2.0
70.0 – j8.6
62.0 – j12.8
53.8 – j13.6
47.3 – j12.4
41.1 – j12.0
S11
Mag
0.182
0.171
0.175
0.182
0.156
0.135
0.128
0.161
Angle
80
22
4.8
–6.6
–40
–66
–95
–119
5528 F04
Figure 4. Equivalent Circuit Schematic of the LO Input
The internal, differential LO signal is then split into inphase and quadrature (90° phase shifted) signals that
drive LO buffer sections. These buffers drive the double
balanced I and Q mixers. The phase relationship between
the LO input and the internal in-phase LO and quadrature
LO signals is fixed, and is independent of start-up conditions. The phase shifters are designed to deliver accurate
quadrature signals for an LO frequency near 2GHz. For
frequencies significantly below 1.8GHz or above 2.4GHz,
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 dynamicrange will degrade, especially below –5dBm and at TA =
85°C. For high LO input power (e.g. 5dBm), the LO feedthrough will increase 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
4GHz) and third harmonics (at 6GHz) at –20dBc level, the
introduced signal at the image frequency is about –56dBc
or lower, corresponding to an excess phase shift much
below 1 degree. For the second and third harmonics at
–10dBc, the introduced signal at the image frequency is
about –47dBc. Higher harmonics than the third will have
less impact. The LO return loss typically will be better than
17dB over the 1.7GHz to 2.3GHz range. Table 1 shows the
LO port input impedance vs. frequency.
If the part is in shut-down mode, the input impedance of
the LO port will be different. The LO input impedance for
EN = Low is given in Table 2.
Table 2. LO Port Input Impedance vs Frequency for EN = Low
Frequency
MHz
1000
1400
1600
1800
2000
2200
2400
2600
Input Impedance
Ω
46.6 + j47.6
136 + j44.5
157 – j24.5
114 – j70.6
70.7 – j72.1
45.3 – j59.0
31.2 – j45.2
22.8 – j34.2
S11
Mag
0.443
0.507
0.526
0.533
0.533
0.528
0.527
0.543
Angle
67.8
13.8
–6.2
–24.6
–43.2
–62.8
–83.5
–103
RF Section
After up-conversion, the RF outputs of the I and Q mixers are
combined. An on-chip balun performs internal differential
to single-ended output conversion, while transforming the
output signal impedance to 50Ω. Table 3 shows the RF
port output impedance vs. frequency.
Table 3. RF Port Output Impedance vs Frequency for EN = High
and PLO = 0dBm
Frequency
MHz
1000
1400
1600
1800
2000
2200
2400
2600
Output Impedance
Ω
23.1 + j7.9
34.4 + j20.7
45.8 + j22.3
54.5 + j12.4
48.7 + j1.7
39.1 + j1.0
32.9 + j4.4
29.7 + j7.4
S22
Mag
0.382
0.298
0.231
0.125
0.022
0.123
0.213
0.269
Angle
158
113
87.6
63.2
127
174
163
155
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The RF output S22 with no LO power applied is given in
Table 4.
Table 4. RF Port Output Impedance vs Frequency for EN = High
and No LO Power Applied
Frequency
MHz
1000
1400
1600
1800
2000
2200
2400
2600
Output Impedance
Ω
23.7 + j8.1
37.7 + j18.5
47.0 + j14.3
46.0 + j5.5
39.2 + j3.7
34.2 + j6.2
31.0 + j9.4
29.6 + j11.6
Enable Interface
S22
Mag
0.371
0.248
0.149
0.071
0.127
0.201
0.260
0.292
Angle
157
112
93.6
123
159
154
147
142
For EN = Low the S22 is given in Table 5.
Table 5. RF Port Output Impedance vs Frequency for EN = Low
Frequency
MHz
1000
1400
1600
1800
2000
2200
2400
2600
Output Impedance
Ω
22.8 + j7.7
32.4 + j20.8
42.4 + j25.1
54.6 + j20.1
55.3 + j6.0
44.7 + j0.0
36.0 + j1.9
31.3 + j4.8
coupling capacitor can be inserted in the RF output line.
This is strongly recommended during a 1dB compression
measurement.
Figure 6 shows a simplified schematic of the EN pin interface. The voltage necessary to turn on the LT5528 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 guaranteed
by the 75k on-chip pull-down resistor. It is important that
the voltage at the EN pin does not exceed VCC by more
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.
S22
Mag
0.386
0.321
0.274
0.193
0.076
0.056
0.164
0.237
VCC
Angle
158
116
91.7
66.2
45.3
180
171
162
To improve S22 for lower frequencies, a shunt capacitor
can be added to the output. At higher frequencies, a shunt
inductor can improve the S22. Figure 5 shows the equivalent
circuit schematic of the RF output.
EN
75k
25k
5528 F06
Figure 6. EN Pin Interface
Evaluation Board
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.
J1
Note that an ESD diode is connected internally from
the RF output to ground. For strong output RF signal
levels (higher than 3dBm), this ESD diode can degrade
the linearity performance if the 50Ω termination impedance is connected directly to ground. To prevent this, a
J2
BBIM
BBIP
VCC
16
R1
100Ω 1
VCC EN
2
J4
LO
IN
3
4
VCC
15
14
C2
100nF
13
BBMI GND BBPI VCC
EN
GND
GND
RF
LT5528
LO
GND
GND
GND
GND
BBMQ GND BBPQ VCC
20pF
5
RF
OUTPUT
3nH
21pF
52.5Ω
6
7
12
BBQM
RF
OUT
10
9
17
8
C1
100nF
J5
J3
11
GND
J6
BBQP
5528 F05
BOARD NUMBER: DC729A
Figure 5. Equivalent Circuit Schematic of the RF Output
5528 F07
Figure 7. Evaluation Circuit Schematic
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Additionally, the exposed pad provides heat sinking for the
part and minimizes the possibility of the chip overheating.
If improved LO and Image suppression are required, an LO
feed-through calibration and an Image suppression calibration can be performed. The evaluation board schematic
of the calibration hardware, the calibration procedure and
the results are described in an application note.
R1 (optional) limits the Enable pin current in the event
that the Enable pin is pulled high while the VCC inputs are
low. In Figures 8, 9, 10 and 11, the silk screens and the
PCB board layout are shown.
Figure 8. Component Side Silk Screen of Evaluation Board
Figure 9. Component Side Layout of Evaluation Board
Figure 10. Bottom Side Silk Screen of Evaluation Board
Figure 11. Bottom Side Layout of Evaluation Board
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Application Measurements
Because of the LT5528’s very high dynamic-range, the
test equipment can limit the accuracy of the ACPR measurement. Consult the factory for advice on the ACPR
measurement, if needed.
The LT5528 is recommended for base-station applications
using various modulation formats. Figure 12 shows a typical application. The CAL box in Figure 12 allows for LO
feed-through and Image suppression calibration.
The ACPR performance is sensitive to the amplitude match
of the BBIP and BBIM (or BBQP and BBQM) 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 the
same (but of opposite sign). The current will enter the
LT5528’s common-base stage, and will flow to the mixer
upper switches. This can be seen in Figure 1 where the
Figure 13 shows the ACPR performance for W-CDMA using
one, two or four channel modulation. Figures 14, 15 and 16
illustrate the 1-, 2- and 4-channel W-CDMA measurement.
To calculate ACPR, a correction is made for the spectrum
analyzer noise floor. If the output power is high, the ACPR
will be limited by the linearity performance of the 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 obtained.
5V
VCC 8, 13
LT5528
EN
90°
7
Q-DAC
PA
BALUN
LO FEED-THROUGH CAL OUT
V-I
5
IMAGE CAL OUT
CAL
BASEBAND
GENERATOR
4-CH ACPR
–65
2-CH AltCPR
–70
1-CH AltCPR
–150
2-CH ACPR
4-CH AltCPR
–155
1-CH ACPR
–75 4-CH NOISE
3
VCO/SYNTHESIZER
2, 4, 6, 9, 10, 12, 15, 17
–80
–42
ADC
–140
–145
–60
11
0°
Q-CHANNEL
DOWNLINK TEST MODEL 64 DPCH
5528 F12
–160
1-CH NOISE
NOISE FLOOR AT 30MHz OFFSET (dBm/Hz)
I-CHANNEL
1
–55
RF = 1.5GHz
TO 2.4GHz
V-I
16
ACPR, AltCPR (dBc)
14
I-DAC
–165
–26 –22 –18 –14
RF OUTPUT POWER PER CARRIER (dBm)
–38
–34
–30
5528 F13
Figure 12. 1.5GHz to 2.4GHz Direct Conversion Transmitter Application with
LO Feed-Through and Image Calibration Loop
–50
–60
–70
UNCORRECTED
SPECTRUM
CORRECTED
SPECTRUM
–90
–100
–110
–120
2127.5
2152.5
5528 F14
Figure 14: 1-Channel W-CDMA Spectrum
–40
DOWNLINK TEST
–40 MODEL 64
DPCH
–50
–60
–70
–80
UNCORRECTED
SPECTRUM
CORRECTED
SPECTRUM
–90
–100
–110
SYSTEM
NOISE FLOOR
2132.5 2137.5 2142.5 2147.5
RF FREQUENCY (MHz)
POWER IN 30kHz BW (dBm)
POWER IN 30kHz BW (dBm)
–40
–80
–30
DOWNLINK TEST
MODEL 64 DPCH
–120
2125
2135 2140 2145 2150
RF FREQUENCY (MHz)
DOWNLINK
–50 TEST
MODEL 64
–60 DPCH
–70
–80
–90
2155
5528 F15
Figure 15: 2-Channel W-CDMA Spectrum
UNCORRECTED
SPECTRUM
CORRECTED
SPECTRUM
–100
–110
–120
SYSTEM
NOISE FLOOR
2130
POWER IN 30kHz BW (dBm)
–30
Figure 13: W-CDMA APCR, AltCPR and Noise
vs RF Output Power at 2140MHz for 1, 2 and
4 Channels
SYSTEM
NOISE FLOOR
CORRECTED SPECTRUM
–130
2115
2125
2135
2145
2155
RF FREQUENCY (MHz)
2165
5528 F16
Figure 16: 4-Channel W-CDMA Spectrum
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internal circuit of the LT5528 is drawn. For best results,
a high ohmic source is recommended; for example, the
interface circuit drawn in Figure 3, modified by pulling
resistors R5 and R6 to a –5V supply and adjusting their
values to 550Ω, with T1 omitted.
secondary in combination with the required impedance
match. The secondary center tap should not be connected,
which allows some voltage swing if there is a singleended input impedance difference at the baseband pins.
As a result, both currents will be equal. The disadvantage
is that there is no DC coupling, so the LO feed-through
calibration cannot be performed via the BB connections.
After calibration when the temperature changes, the LO
feed-through and the Image Rejection performance will
change. This is illustrated in Figure 17. The LO feed-through
and Image Rejection can also change as a function of the
baseband drive level, as is depicted in Figure 18. The RF
output power, IM2 and IM3 vs a two-tone baseband drive
are given in Figure 19.
Another method to reduce current mismatch between
the currents flowing in the BBIP and BBIM pins (or the
BBQP and BBQM pins) is to use a 1:1 transformer with
the two windings in the DC path (T1 in Figure 3). For DC,
the transformer forms a short, and for AC, the transformer
will reduce the common-mode current component, which
forces the two currents to be better matched. Alternatively,
a transformer with 1:2 impedance ratio can be used, which
gives a convenient DC separation between primary and
–50
–20
LOFT (dBm), IR (dBc)
–60
–65
–70 IMAGE REJECTION
–75
–80
CALIBRATED WITH PRF = –10dBm
–85
–40
–20
0
20
40
TEMPERATURE (°C)
EN = HIGH
VCC = 5V
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
0
–30
LO FEED-THROUGH
60
–40
fLO = 2.14GHz
fRF = fBB + fLO
PLO = 0dBm
IR
–60
Figure 17: LO Feed-Through and Image Rejection vs Temperature
after Calibration at 25°C
PRF, EACH TONE (dBm), IM2, IM3 (dBm)
10
0
–10
–30
–70
–40
–80
–40°C –50
25°C
85°C
–60
1
2
3
4
5
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
0
EN = HIGH
VCC = 5V
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
5528 F18
–10
–20
–50
–90
80
LOFT
PRF (dBm)
LOFT (dBm), IR (dB)
–55
10
PRF
fLO = 2.14GHz
fRF = fBB + fLO
PLO = 0dBm
5528 F18
Figure 18: LO Feed-Through and Image Rejection vs Baseband
Drive Voltage after Calibration at 25°C
PRF
IM3
–20
–30
–40
–50
IM2
–60
–70
–80
–40°C
25°C
85°C
–90
1
0.1
10
I AND Q BASEBAND VOLTAGE (VP-P, DIFF EACH TONE)
EN = HIGH
fLO = 2.14GHz
VCC = 5V
fRF = fBB + fLO
PLO = 0dBm
fBBI = 2MHz, 2.1MHz, 0°
fBBQ = 2MHz, 2.1MHz, 90°
IM2 = POWER AT fLO + 4.1MHz
IM3 = MAX POWER AT fLO + 1.9MHz OR
fLO + 2.2MHz
5528 F19
Figure 19: RF Two-Tone Power, IM2 and IM3 at 2140MHz vs Baseband Voltage
5528f
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LT5528
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PACKAGE DESCRIPTIO
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
0.72 ±0.05
4.35 ± 0.05
2.15 ± 0.05
2.90 ± 0.05 (4 SIDES)
PACKAGE OUTLINE
0.30 ±0.05
0.65 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
4.00 ± 0.10
(4 SIDES)
0.75 ± 0.05
R = 0.115
TYP
PIN 1
TOP MARK
(NOTE 6)
0.55 ± 0.20
15
16
1
2.15 ± 0.10
(4-SIDES)
2
(UF) QFN 1103
0.200 REF
0.00 – 0.05
0.30 ± 0.05
0.65 BSC
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
5528f
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.
15
LT5528
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
Infrastructure
LT5511
High Linearity Upconverting Mixer
RF Output to 3GHz, 17dBm IIP3, Integrated LO Buffer
LT5512
DC-3GHz High Signal Level Downconverting
Mixer
DC to 3GHz, 17dBm IIP3, Integrated LO Buffer
LT5514
Ultralow Distortion, IF Amplifier/ADC Driver
with Digitally Controlled Gain
850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range
LT5515
1.5GHz to 2.5GHz Direct Conversion Quadrature 20dBm IIP3, Integrated LO Quadrature Generator
Demodulator
LT5516
0.8GHz to 1.5GHz Direct Conversion Quadrature 21.5dBm IIP3, Integrated LO Quadrature Generator
Demodulator
LT5517
40MHz to 900MHz Quadrature Demodulator
21dBm IIP3, Integrated LO Quadrature Generator
LT5519
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
LT5520
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
LT5521
10MHz to 3700MHz High Linearity
Upconverting Mixer
24.2dBm IIP3 at 1.95GHz, NF = 12.5dB, 3.15V to 5.25V Supply, Single-Ended LO
Port Operation
LT5522
600MHz to 2.7GHz High Signal Level
Downconverting Mixer
4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB, 50Ω Single-Ended RF
and LO Ports
LT5524
Low Power, Low Distortion ADC Driver with
Digitally Programmable Gain
450MHz Bandwidth, 40dBm OIP3, 4.5dB to 27dB Gain Control
LT5526
High Linearity, Low Power Downconverting
Mixer
3V to 5.3V Supply, 16.5dBm IIP3, 100kHz to 2GHz RF, NF = 11dB, IS = 28mA,
–65dBm LO-RF Leakage
RF Power Detectors
LT5504
800MHz to 2.7GHz RF Measuring Receiver
80dB Dynamic Range, Temperature Compensated, 2.7V to 5.25V Supply
LTC5505
RF Power Detectors with >40dB Dynamic
Range
300MHz to 3GHz, Temperature Compensated, 2.7V to 6V Supply
LTC5507
100kHz to 1000MHz RF Power Detector
100kHz to 1GHz, Temperature Compensated, 2.7V to 6V Supply
LTC5508
300MHz to 7GHz RF Power Detector
44dB Dynamic Range, Temperature Compensated, SC70 Package
LTC5509
300MHz to 3GHz RF Power Detector
36dB Dynamic Range, Low Power Consumption, SC70 Package
LTC5530
300MHz to 7GHz Precision RF Power Detector
Precision VOUT Offset Control, Shutdown, Adjustable Gain
LTC5531
300MHz to 7GHz Precision RF Power Detector
Precision VOUT Offset Control, Shutdown, Adjustable Offset
LTC5532
300MHz to 7GHz Precision RF Power Detector
Precision VOUT Offset Control, Adjustable Gain and Offset
LT5534
50MHz to 3GHz RF Power Detector with 60dB
Dynamic Range
±1dB Output Variation over Temperature, 38ns Response Time
Low Voltage RF Building Blocks
LT5500
1.8GHz to 2.7GHz Receiver Front End
1.8V to 5.25V Supply, Dual-Gain LNA, Mixer, LO Buffer
LT5502
400MHz Quadrature IF Demodulator with RSSI
1.8V to 5.25V Supply, 70MHz to 400MHz IF, 84dB Limiting Gain, 90dB RSSI Range
LT5503
1.2GHz to 2.7GHz Direct IQ Modulator and
Upconverting Mixer
1.8V to 5.25V Supply, Four-Step RF Power Control, 120MHz Modulation Bandwidth
LT5506
500MHz Quadrature Demodulator with VGA
1.8V to 5.25V Supply, 40MHz to 500MHz IF, –4dB to 57dB Linear Power Gain,
8.8MHz Baseband Bandwidth
LT5546
500MHz Quadrature Demodulator with VGA and 17MHz Baseband Bandwidth, 40MHz to 500MHz IF, 1.8V to 5.25V Supply, –7dB to
17MHz Baseband Bandwidth
56dB Linear Power Gain
Wide Bandwidth ADCs
LTC1749
12-Bit, 80Msps
500MHz BW S/H, 71.8dB SNR
LTC1750
14-Bit, 80Msps
500MHz BW S/H, 75.5dB SNR
5528f
16 Linear Technology Corporation
LT/TP 1104 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2004