LT5528
1
5528f
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 confi gured
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
P
OUT = 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
1.5GHz to 2.4GHz Direct Conversion Transmitter Application
with LO Feed-Through and Image Calibration Loop
90°
0°
LT5528
BASEBAND
DSP
CAL
LO FEED-THROUGH CAL OUT
IMAGE CAL OUT
PA
VCO/SYNTHESIZER
RF = 1.5GHz
TO 2.4GHz
EN
2, 4, 6, 9, 10, 12, 15, 17
5V
V-I
V-I
I-CHANNEL
Q-CHANNEL BALUN
14
16
1
7
5
8, 13
VCC
11
3
5528 TA01a
I-DAC
Q-DAC
ADC
1.5GHz to 2.4GHz
High Linearity Direct
Quadrature Modulator
■ 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
RF OUTPUT POWER PER CARRIER (dBm)
–38–42
ACPR, AltCPR (dBc)
–55
–60
–65
–70
–75
–80
NOISE FLOOR AT 30MHz OFFSET (dBm/Hz)
–140
–150
–145
–155
–165
–160
5528 TA01b
–14–18–22–26–30–34
4-CH ACPR 2-CH ACPR
1-CH ACPR
4-CH AltCPR
2-CH AltCPR
DOWNLINK TEST MODEL 64 DPCH
1-CH AltCPR
4-CH NOISE
1-CH NOISE
W-CDMA ACPR, AltCPR and Noise vs RF Output
Power at 2140MHz for 1, 2 and 4 Channels
APPLICATIO S
U
FEATURES DESCRIPTIO
U
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
LT5528
2
5528f
ORDER PART
NUMBER
UF PART
MARKING
TJMAX = 125°C, θJA = 37°C/W
EXPOSED PAD IS GROUND (PIN 17)
MUST BE SOLDERED TO PCB.
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
5528A
LT5528EUF
(Note 1)
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
V
CC = 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 CONDITIONS MIN TYP MAX UNITS
RF Output (RF)
fRF RF Frequency Range –3dB Bandwidth 1.5 to 2.4 GHz
RF Frequency Range –1dB Bandwidth 1.7 to 2.2 GHz
S22, ON RF Output Return Loss EN = High (Note 6) –15 dB
S22, OFF RF Output Return Loss EN = Low (Note 6) –12 dB
NFloor RF Output Noise Floor No Input Signal (Note 8) –159.3 dBm/Hz
P
OUT = 4dBm (Note 9) –151.8 dBm/Hz
P
OUT = 4dBm (Note 10) –151.8 dBm/Hz
GP Conversion Power Gain POUT/PIN, I&Q –6.5 dB
GV Conversion Voltage Gain 20 • Log (VOUT, 50Ω/VIN, DIFF, I or Q) –6 dB
POUT Absolute Output Power 1VP-P DIFF CW Signal, I and Q –2.1 dBm
G3LO vs LO 3 • LO Conversion Gain Difference (Note 17) –28 dB
OP1dB Output 1dB Compression (Note 7) 7.9 dBm
OIP2 Output 2nd Order Intercept (Notes 13, 14) 49 dBm
OIP3 Output 3rd Order Intercept (Notes 13, 15) 21.8 dBm
IR Image Rejection (Note 16) –45 dBc
LOFT Carrier Leakage EN = High, PLO = 0dBm (Note 16) –42 dBm
(LO Feed-Through) EN = Low, PLO = 0dBm (Note 16) –57.8 dBm
LO Input (LO)
fLO LO Frequency Range 1.5 to 2.4 GHz
PLO LO Input Power –10 0 5 dBm
S11, ON LO Input Return Loss EN = High (Note 6) –17 dB
S11, OFF LO Input Return Loss EN = Low (Note 6) –5.5 dB
NFLO LO Input Referred Noise Figure (Note 5) at 2GHz 14.4 dB
GLO LO to RF Small Signal Gain (Note 5) at 2GHz 20.4 dB
IIP3LO LO Input 3rd Order Intercept (Note 5) at 2GHz –10 dBm
ELECTRICAL CHARACTERISTICS
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
16 15 14 13
5 6 7 8
TOP VIEW
9
10
11
12
4
3
2
1EN
GND
LO
GND
GND
RF
GND
GND
BBMI
GND
BBPI
VCC
BBMQ
GND
BBPQ
VCC
17
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
LT5528
3
5528f
V
CC = 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)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Specifi cations 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 confi guration 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.
Note 10: At 5MHz offset from the CW signal frequency.
Note 11: RF power is within 10% of fi nal 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.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Baseband Inputs (BBPI, BBMI, BBPQ, BBMQ)
BWBB Baseband Bandwidth –3dB Bandwidth 400 MHz
VCMBB DC Common Mode Voltage (Note 4) 0.525 V
RIN, SE Single-Ended Input Resistance (Note 4) 45 Ω
PLO2BB Carrier Feed-Through on BB POUT = 0 (Note 4) –40 dBm
IP1dB Input 1dB Compression Point Differential Peak-to-Peak (Note 7) 3.2 VP-P, DIFF
ΔGI/Q I/Q Absolute Gain Imbalance 0.05 dB
ΔϕI/Q I/Q Absolute Phase Imbalance 0.5 Deg
Power Supply (VCC)
VCC Supply Voltage 4.5 5 5.25 V
ICC, ON Supply Current EN = High 125 145 mA
ICC, OFF Supply Current, Sleep Mode EN = 0V 0.05 50 µA
tON Turn-On Time EN = Low to High (Note 11) 0.25 µs
tOFF Turn-Off Time EN = High to Low (Note 12) 1.3 µs
Enable (EN), Low = Off, High = On
Enable Input High Voltage EN = High 1.0 V
Input High Current EN = 5V 240 µA
Sleep Input Low Voltage EN = Low 0.5 V
ELECTRICAL CHARACTERISTICS
LT5528
4
5528f
LO FREQUENCY (GHz)
1.3
OIP3 (dBm)
26
24
22
18
20
16
14
12
10
8
6
NOISE FLOOR (dBm/Hz)
–142
–144
–146
–150
–148
–152
–154
–156
–158
–160
–162
5528 G05
1.91.71.5 2.1 2.3 2.72.5
4.5V
5V
5.5V
NOISE FLOOR
NO BASEBAND SIGNAL
20MHz OFFSET NOISE
OIP3
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
LO FREQUENCY (GHz)
1.3
OIP3 (dBm)
26
24
22
18
20
16
14
12
10
8
6
NOISE FLOOR (dBm/Hz)
–142
–144
–146
–150
–148
–152
–154
–156
–158
–160
–162
5528 G04
1.91.71.5 2.1 2.3 2.72.5
NOISE FLOOR
NO BASEBAND SIGNAL
20MHz OFFSET NOISE
OIP3
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
–40°C
25°C
85°C
LO FREQUENCY (GHz)
1.3
GAIN (dB), OP1dB (dBm)
10
5
0
–5
–10
–15
–20
5528 G02
1.91.71.5 2.1 2.3 2.
7
2.5
–40°C
25°C
85°C
GAIN
OP1dB
LO FREQUENCY (GHz)
1.3
GAIN (dB), OP1dB (dBm)
10
5
0
–5
–10
–15
–20
5528 G03
1.91.71.5 2.1 2.3 2.
7
2.5
GAIN
OP1dB
4.5V
5V
5.5V
LO FREQUENCY (GHz)
1.3
OIP2 (dBm)
65
60
55
50
45
40
35
5528 G06
1.91.71.5 2.1 2.3 2.
7
2.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
fIM2 = fBB,1 + fBB,2 + fLO
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
SUPPLY VOLTAGE (V)
4.5
SUPPLY CURRENT (mA)
140
130
120
110
100
5528 G01
5.0 5.5
85°C
25°C
–40°C
Supply Current vs Supply Voltage
Gain and Output 1dB Compression
vs LO Frequency and Temperature
Gain and Output 1dB
Compression vs LO Frequency
and Supply Voltage
Output IP3 and Noise Floor vs
LO Frequency and Temperature
Output IP3 and Noise Floor vs
LO Frequency and Supply Voltage Output IP2 vs LO Frequency
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)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
LT5528
5
5528f
2 • LO FREQUENCY (GHz)
2.6
P(2 • LO) (dBm)
–25
–30
–35
–40
–45
–50
–55
5528 G07
3.83.43.0 4.2 4.6 5.45.0
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
3 • LO FREQUENCY (GHz)
3.9
P(3 • LO) (dBm)
–30
–35
–40
–45
–50
–70
–65
–60
–55
5528 G08
5.75.14.5 6.3 6.9 8.17.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
LO FREQUENCY (GHz)
1.3
LOFT (dBm)
–36
–38
–40
–42
–44
–46
–54
–48
–50
–52
5528 G09
1.91.71.5 2.1 2.3 2.
7
2.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
LO FREQUENCY (GHz)
1.3
IMAGE REJECTION (dBc)
–26
–28
–34
–32
–30
–36
–38
–40
–42
–44
–46
–48
5528 G10
1.91.71.5 2.1 2.3 2.
7
2.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
LO FREQUENCY (GHz)
1.3
ABSOLUTE I/Q GAIN IMBALANCE (dB)
5528 G11
1.91.71.5 2.1 2.3 2.
7
2.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
0.3
0.2
0.1
0
2 • LO Leakage to RF Output vs
2 • LO Frequency
3 • LO Leakage to RF Output vs
3 • LO Frequency
LO to RF Output Feed-Through vs
LO Frequency
Image Rejection vs LO Frequency
Absolute I/Q Gain Imbalance vs
LO Frequency
Absolute I/Q Phase Imbalance vs
LO Frequency
LO FREQUENCY (GHz)
1.3
ABSOLUTE I/Q PHASE IMBALANCE (DEG)
5528 G12
1.91.71.5 2.1 2.3 2.
7
2.5
5
4
3
2
1
0
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
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)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
LT5528
6
5528f
Gain vs LO Power
RF Output Power, HD2 and HD3
at 2140MHz vs Baseband Voltage
and Temperature
LO Feed-Through and Image
Rejection at 2140MHz vs Baseband
Voltage and Temperature
Output IP3 vs LO Power
LO POWER (dBm)
–20
GAIN (dB)
5528 G13
–8–12–16 –4 0 84
–4
–6
–8
–10
–12
–14
–16
–18
–20
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
–20 –8–12–16 –4 0 84
LO POWER (dBm)
OIP3 (dBm)
22
20
18
16
12
14
10
8
6
4
2
0
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
5528 G14
fBB, 1 = 2MHz
fBB, 2 = 2.1MHz
RF Output Power, HD2 and HD3
at 2140MHz vs Baseband Voltage
and Supply Voltage
0123 54
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
HD2, HD3 (dBc)
–10
–20
–30
–40
–60
–50
–70
RF OUTPUT POWER (dBm)
10
0
–10
–20
–30
–40
–50
–40°C
25°C
85°C
5528 G15
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
HD2
RF
HD3
0123 54
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
LOFT (dBm), IR (dBc)
–25
–30
–40
–45
–35
–50
–40°C
25°C
85°C
5528 G17
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
IR
LOFT
0123 54
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
HD2, HD3 (dBc)
–10
–20
–30
–40
–60
–50
–70
RF OUTPUT POWER (dBm)
10
0
–10
–20
–30
–40
–50
5528 G16
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
HD2
RF
HD3
4.5V
5V
5.5V
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)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
LT5528
7
5528f
LO and RF Port Return Loss vs
RF Frequency
0123 54
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
LOFT (dBm), IR (dBc)
–25
–30
–40
–45
–35
–50
5528 G18
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
IR
LOFT
4.5V
5V
5.5V
RF FREQUENCY (GHz)
1.3
S11 (dB)
5528 G19
1.91.71.5 2.1 2.3 2.
7
2.5
0
–10
–20
–30
–40
–50
RF PORT,
EN = HIGH,
PLO = OFF
RF PORT,
EN = LOW
LO PORT,
EN = HIGH
LO PORT, EN = LOW
RF PORT,
EN = HIGH,
PLO = 0dBm
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.
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.
LO (Pin 3): LO Input. The LO input is an AC-coupled single-
ended 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.
BBPQ, BBMQ (Pins 7, 5): Baseband Inputs for the Q-chan-
nel, each 45Ω input impedance. Internally biased at about
0.525V. Applied voltage must stay below 2.5V.
VCC (Pins 8, 13): Power Supply. Pins 8 and 13 are con-
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 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.
LO Feed-Through and Image
Rejection at 2140MHz vs Baseband
Voltage and Supply Voltage
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)
RF Output Power vs
RF Frequency at 1VP-P
Differential Baseband Drive
RF FREQUENCY (GHz)
1.3
RF OUTPUT POWER (dBm)
0
–2
–4
–6
–8
–10
–14
–12
5528 G20
1.91.71.5 2.1 2.3 2.
7
2.5
4.5V, 25°C
5V, –40°C
5V, 25°C
5V, 85°C
5.5V, 25°C
VBBI = 1VP-P, DIFF
VBBQ = 1VP-P, DIFF
TYPICAL PERFOR A CE CHARACTERISTICS
UW
PI FU CTIO S
UUU
LT5528
8
5528f
90°
0°
LT5528
V-I
V-I
BALUN
VCC
RF
LO
5528 BD
11
EN
1
396
GND
42
5
7
16
14
813
BBPI
BBMI
BBPQ
BBMQ
1715
GND
1210
The LT5528 consists of I and Q input differential voltage-
to-current converters, I and Q up-conversion mixers, an
RF output balun, an LO quadrature phase generator and
LO buffers.
RF
VCC = 5V
BBPI
BBMI
C
GND
LOMI LOPI
R4
FROM
Q
5528 F01
BALUN
CM
VREF = 0.52V
R3
R1B
23Ω
R1A
20Ω
12pF
R2A
20Ω
R2B
23Ω
12pF
LT5528
Figure 1. Simplifi ed Circuit Schematic of the LT5528
(Only I-Half is Drawn)
External I and Q baseband signals are applied to the dif-
ferential 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 in-
phase 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.
Baseband Interface
The baseband inputs (BBPI, BBMI), (BBPQ, BBMQ) present
a differential input impedance of about 90Ω. At each of the
four baseband inputs, a fi rst-order low-pass fi lter using 20Ω
BLOCK DIAGRA
W
APPLICATIO S I FOR ATIO
WUUU
LT5528
9
5528f
••
RF = –2.5dBm, MAX
VCC = 5V
C
GND
LOMI LOPI
R4
5528 F03
LT5528
GND
CM
VREF = 0.52V
R3
R1
45Ω
T1
1:1
C2
BBPI
OPTIONAL
BBMI
L1A
L1B
C1 C3
R2
45Ω
0.5V
R5, 50Ω
0.5V
R6, 50Ω
DAC
0mA TO 20mA
0mA TO 20mA
L2A
L2B
BALUN
Figure 3. LT5528 5th Order Filtered Baseband Interface with Common DAC (Only I-Channel is Shown)
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 de-
grade the overall linearity severely. Typically, a DAC will
be the signal source for the LT5528. To prevent aliasing,
a fi lter 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 fi lter. 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
confi guration shown in Figure 3 is about –2.5dBm. The
maximum CW output power can be increased by con-
necting 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 fi lter component values
require adjustment for a higher source impedance.
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).
5528 F02
45Ω50Ω
LT5528GENERATOR
0.52VDC
0.52VDC
0.52VDC +
–
+
–
50Ω
50Ω
GENERATOR
0.52VDC
0.26VDC
+
–
APPLICATIO S I FOR ATIO
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LT5528
10
5528f
LO Section
The internal LO input amplifi er performs single-ended to
differential conversion of the LO input signal. Figure 4
shows the equivalent circuit schematic of the LO input.
Table 1. LO Port Input Impedance vs Frequency for EN = High
Frequency Input Impedance S11
MHz Ω Mag Angle
1000 49.9 + j18.5 0.182 80
1400 68.1 + j8.8 0.171 22
1600 71.0 + j2.0 0.175 4.8
1800 70.0 – j8.6 0.182 –6.6
2000 62.0 – j12.8 0.156 –40
2200 53.8 – j13.6 0.135 –66
2400 47.3 – j12.4 0.128 –95
2600 41.1 – j12.0 0.161 –119
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 Input Impedance S11
MHz Ω Mag Angle
1000 46.6 + j47.6 0.443 67.8
1400 136 + j44.5 0.507 13.8
1600 157 – j24.5 0.526 –6.2
1800 114 – j70.6 0.533 –24.6
2000 70.7 – j72.1 0.533 –43.2
2200 45.3 – j59.0 0.528 –62.8
2400 31.2 – j45.2 0.527 –83.5
2600 22.8 – j34.2 0.543 –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 Output Impedance S22
MHz Ω Mag Angle
1000 23.1 + j7.9 0.382 158
1400 34.4 + j20.7 0.298 113
1600 45.8 + j22.3 0.231 87.6
1800 54.5 + j12.4 0.125 63.2
2000 48.7 + j1.7 0.022 127
2200 39.1 + j1.0 0.123 174
2400 32.9 + j4.4 0.213 163
2600 29.7 + j7.4 0.269 155
LO
INPUT
20pF
ZIN ≈ 57Ω
5528 F04
VCC
The internal, differential LO signal is then split into in-
phase 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 fi xed, and is independent of start-up condi-
tions. The phase shifters are designed to deliver accurate
quadrature signals for an LO frequency near 2GHz. For
frequencies signifi cantly 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 dynamic-
range will degrade, especially below –5dBm and at TA =
85°C. For high LO input power (e.g. 5dBm), the LO feed-
through 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.
Figure 4. Equivalent Circuit Schematic of the LO Input
APPLICATIO S I FOR ATIO
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LT5528
11
5528f
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 Output Impedance S22
MHz Ω Mag Angle
1000 23.7 + j8.1 0.371 157
1400 37.7 + j18.5 0.248 112
1600 47.0 + j14.3 0.149 93.6
1800 46.0 + j5.5 0.071 123
2000 39.2 + j3.7 0.127 159
2200 34.2 + j6.2 0.201 154
2400 31.0 + j9.4 0.260 147
2600 29.6 + j11.6 0.292 142
For EN = Low the S22 is given in Table 5.
Table 5. RF Port Output Impedance vs Frequency for EN = Low
Frequency Output Impedance S22
MHz Ω Mag Angle
1000 22.8 + j7.7 0.386 158
1400 32.4 + j20.8 0.321 116
1600 42.4 + j25.1 0.274 91.7
1800 54.6 + j20.1 0.193 66.2
2000 55.3 + j6.0 0.076 45.3
2200 44.7 + j0.0 0.056 180
2400 36.0 + j1.9 0.164 171
2600 31.3 + j4.8 0.237 162
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.
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 imped-
ance is connected directly to ground. To prevent this, a
coupling capacitor can be inserted in the RF output line.
This is strongly recommended during a 1dB compression
measurement.
Enable Interface
Figure 6 shows a simplifi ed schematic of the EN pin in-
terface. 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.
Figure 7. Evaluation Circuit SchematicFigure 5. Equivalent Circuit Schematic of the RF Output
Figure 6. EN Pin Interface
RF
OUTPUT
20pF
21pF3nH 52.5Ω
5528 F05
VCC
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.
EN
75k
5528 F06
VCC
25k
BBIPBBIM
J1
16 15 14 13
VCC
VCC EN
9
10
11
12
4
3
2
1
5678
5528 F07
17
BBQM
BBQP
BOARD NUMBER: DC729A
C1
100nF J6
RF
OUT
J3
LO
IN
J4
GND
J5
C2
100nF
J2
BBMI
LT5528
BBPI VCC
BBMQ GND
GND
BBPQ VCC
GND
GND
RF
GND
GND
LO
GND
EN
GND
100Ω
R1
APPLICATIO S I FOR ATIO
WUUU
LT5528
12
5528f
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 calibra-
tion 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 10. Bottom Side Silk Screen of Evaluation Board
Figure 9. Component Side Layout of Evaluation Board
Figure 11. Bottom Side Layout of Evaluation Board
APPLICATIO S I FOR ATIO
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LT5528
13
5528f
Application Measurements
The LT5528 is recommended for base-station applications
using various modulation formats. Figure 12 shows a typi-
cal application. The CAL box in Figure 12 allows for LO
feed-through and Image suppression calibration.
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 fl oor. 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.
Because of the LT5528’s very high dynamic-range, the
test equipment can limit the accuracy of the ACPR mea-
surement. Consult the factory for advice on the ACPR
measurement, if needed.
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 fl ow to the mixer
upper switches. This can be seen in Figure 1 where the
Figure 12. 1.5GHz to 2.4GHz Direct Conversion Transmitter Application with
LO Feed-Through and Image Calibration Loop
90°
0°
LT5528
BASEBAND
GENERATOR
CAL
LO FEED-THROUGH CAL OUT
IMAGE CAL OUT
PA
VCO/SYNTHESIZER
RF = 1.5GHz
TO 2.4GHz
EN
2, 4, 6, 9, 10, 12, 15, 17
5V
V-I
V-I
I-CHANNEL
Q-CHANNEL BALUN
14
16
1
7
5
8, 13
VCC
11
3
5528 F12
I-DAC
Q-DAC
ADC
Figure 14: 1-Channel W-CDMA Spectrum
RF FREQUENCY (MHz)
2127.5
POWER IN 30kHz BW (dBm)
5528 F14
2142.52137.52132.5 2147.5 2152.5
–30
–40
–60
–70
–80
–90
–120
–110
–100
–50
SYSTEM
NOISE FLOOR
CORRECTED
SPECTRUM
DOWNLINK TEST
MODEL 64 DPCH
UNCORRECTED
SPECTRUM
Figure 15: 2-Channel W-CDMA Spectrum
RF FREQUENCY (MHz)
2125
POWER IN 30kHz BW (dBm)
5528 F15
214021352130 2145 21552150
–30
–40
–60
–70
–80
–90
–120
–110
–100
–50
UNCOR-
RECTED
SPECTRUM
SYSTEM
NOISE FLOOR
CORRECTED
SPECTRUM
DOWNLINK TEST
MODEL 64
DPCH
Figure 13: W-CDMA APCR, AltCPR and Noise
vs RF Output Power at 2140MHz for 1, 2 and
4 Channels
RF OUTPUT POWER PER CARRIER (dBm)
–38–42
ACPR, AltCPR (dBc)
–55
–60
–65
–70
–75
–80
NOISE FLOOR AT 30MHz OFFSET (dBm/Hz)
–140
–150
–145
–155
–165
–160
5528 F13
–14–18–22–26–30–34
4-CH ACPR 2-CH ACPR
1-CH ACPR
4-CH AltCPR
2-CH AltCPR
DOWNLINK TEST MODEL 64 DPCH
1-CH AltCPR
4-CH NOISE
1-CH NOISE
Figure 16: 4-Channel W-CDMA Spectrum
DOWNLINK
TEST
MODEL 64
DPCH
RF FREQUENCY (MHz)
2115
POWER IN 30kHz BW (dBm)
5528 F16
214521352125 2155 2165
–40
–60
–70
–80
–90
–130
–120
–110
–100
–50
UNCOR-
RECTED
SPECTRUM
SYSTEM
NOISE FLOOR
CORRECTED SPECTRUM
CORRECTED
SPECTRUM
APPLICATIO S I FOR ATIO
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LT5528
14
5528f
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, modifi ed by pulling
resistors R5 and R6 to a –5V supply and adjusting their
values to 550Ω, with T1 omitted.
Another method to reduce current mismatch between
the currents fl owing 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
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 single-
ended 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.
Figure 18: LO Feed-Through and Image Rejection vs Baseband
Drive Voltage after Calibration at 25°C
0123 54
I AND Q BASEBAND VOLTAGE (VP-P, DIFF)
LOFT (dBm), IR (dBc)
–90
–80
–20
–30
–40
–60
–50
–70
PRF (dBm)
10
0
–10
–20
–30
–40
–60
–50
–40°C
25°C
85°C
5528 F18
EN = HIGH
VCC = 5V
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
fLO = 2.14GHz
fRF = fBB + fLO
PLO = 0dBm
IR
PRF
LOFT
Figure 17: LO Feed-Through and Image Rejection vs Temperature
after Calibration at 25°C
–40 –20 0 20 8040 60
TEMPERATURE (°C)
LOFT (dBm), IR (dB)
–85
–80
–50
–55
–60
–70
–65
–75
5528 F18
EN = HIGH
VCC = 5V
fBBI = 2MHz, 0°
fBBQ = 2MHz, 90°
fLO = 2.14GHz
fRF = fBB + fLO
PLO = 0dBm
CALIBRATED WITH PRF = –10dBm
LO FEED-THROUGH
IMAGE REJECTION
Figure 19: RF Two-Tone Power, IM2 and IM3 at 2140MHz vs Baseband Voltage
0.1 110
I AND Q BASEBAND VOLTAGE (VP-P, DIFF EACH TONE)
PRF, EACH TONE (dBm), IM2, IM3 (dBm)
–90
–80
10
0
–20
–10
–30
–40
–60
–50
–70 –40°C
25°C
85°C
5528 F19
EN = HIGH
VCC = 5V
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
fLO = 2.14GHz
fRF = fBB + fLO
PLO = 0dBm
PRF
IM2
IM3
APPLICATIO S I FOR ATIO
WUUU
LT5528
15
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.
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
4.00 ± 0.10
(4 SIDES)
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
PIN 1
TOP MARK
(NOTE 6)
0.55 ± 0.20
1615
1
2
BOTTOM VIEW—EXPOSED PAD
2.15 ± 0.10
(4-SIDES)
0.75 ± 0.05 R = 0.115
TYP
0.30 ± 0.05
0.65 BSC
0.200 REF
0.00 – 0.05
(UF) QFN 1103
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.72 ±0.05
0.30 ±0.05
0.65 BSC
2.15 ± 0.05
(4 SIDES)
2.90 ± 0.05
4.35 ± 0.05
PACKAGE OUTLINE
PACKAGE DESCRIPTIO
U
LT5528
16
5528f
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 Amplifi er/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
Demodulator
20dBm IIP3, Integrated LO Quadrature Generator
LT5516 0.8GHz to 1.5GHz Direct Conversion Quadrature
Demodulator
21.5dBm IIP3, Integrated LO Quadrature Generator
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
17MHz Baseband Bandwidth, 40MHz to 500MHz IF, 1.8V to 5.25V Supply, –7dB to
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
RELATED PARTS
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2004
LT/TP 1104 1K • PRINTED IN USA
