LINER LT5503

Final Electrical Specifications
LT5503
1.2GHz to 2.7GHz Direct
IQ Modulator and Mixer
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Single 1.8V to 5.25V Supply
Direct IQ Modulator with Integrated 90° Phase
Shifter*
Four Step RF Power Control
120MHz Modulation Bandwidth
Independent Double-Balanced Mixer
Modulation Accuracy Insensitive to Carrier Input
Power
Modulator I/Q Inputs Internally Biased
The LT®5503 is a front-end transmitter IC designed for low
voltage operation, and is compatible with the LTC family of
WLAN products. The IC contains a high frequency quadrature modulator with a variable gain amplifier (VGA) and a
balanced mixer. The modulator includes a precision 90°
phase shifter which allows direct modulation of an RF
signal by the baseband I and Q signals.
IEEE 802.11 DSSS and FHSS
High Speed Wireless LAN (WLAN)
Wireless Local Loop (WLL)
PCS Wireless Data
MMDS
The LT5503 modulator output delivers –3dBm at 2.5GHz.
The VGA allows output power reduction in three steps up
to 13dB with digital control. The baseband inputs are
internally biased for maximum input voltage swing at low
supply voltage. If needed, they can be driven with external
bias voltages.
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APPLICATIO S
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October 2001
DESCRIPTIO
FEATURES
, LTC and LT are registered trademarks of Linear Technology Corporation.
*Patent Pending
In a superheterodyne system, the mixer can be used to
generate the high-frequency RF input for the modulator by
mixing the system’s 1st and 2nd local oscillators.
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TYPICAL APPLICATIO
2.45GHz
BPF
–2
MX –
VCCLO2 VCCLO1
MX +
MODIN VCCRF
VCCMOD
OUTPUT POWER (dBm)
BQ+ BQ–
MIXER
ENABLE
MODULATOR
ENABLE
LO2IN
(750MHz)
2.45GHz Modulated Output
Power vs Supply Voltage
VCC1
2V
VCC2
2V
VCCVGA
MIXEN
MODEN
LO2
÷2
MODOUT
VGA
0°
÷1
90°
CONTROL
LOGIC
GND
DMODE
5503 F01
LO1IN (2075MHz)
BI+ BI–
–4
–5
–6
GC1 GC2
LO1
–3
2.45GHz
MODULATED
RFOUT
PLO1 = –12dBm
PLO2 = –18dBm
BASEBAND = 1VP-P
TA = 27°C
1.8
2.4
3.0
3.6
4.2
SUPPLY VOLTAGE (V)
4.8
5.4
5503 TA01b
Figure 1. 2.45GHz Transmitter Application, Carrier for Modulator Generated by Upmixer
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.
1
LT5503
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage ...................................................... 5.5V
Control Voltages .......................... –0.3V to (VCC + 0.3V)
Baseband Voltages (BI+ to BI– and BQ+ to BQ–) ...... ±2V
Baseband Common Mode Voltage .....1V to (VCC – 0.3V)
LO1 Input Power .................................................. 4dBm
LO2 Input Power .................................................. 4dBm
MODIN Input Power ............................................. 4dBm
Operating Temperature Range .................–40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
BQ – 1
20 BI –
BQ+ 2
19 BI+
GC1 3
18 GC2
MODIN 4
ORDER PART
NUMBER
LT5503EFE
17 MODOUT
VCCMOD 5
16 VCCVGA
VCCRF 6
15 VCCLO2
LO1 7
14 LO2
VCCLO1 8
13 MODEN
DMODE 9
12 MIXEN
MX + 10
11 MX –
21
FE PACKAGE
20-LEAD PLASTIC TSSOP
PIN 21 = GND (BACKSIDE)
TJMAX = 150°C, θJA = 38°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
2
LT5503
ELECTRICAL CHARACTERISTICS
(I/Q Modulator)
VCC1 = 3VDC, 2.4GHz matching, MODEN = High, GC1 = GC2 = Low, TA = 27ºC, MODRFIN = 2.45GHz at –16dBm, [I – IB] and [Q – QB] =
100kHz CW signal at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.) (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
RF Carrier Input (MODRFIN)
Frequency Range2
Input VSWR
1.2 to 2.7
ZO = 50Ω
GHz
1.3:1
Input Power
–20 to -10
dBm
120
MHz
1
VP-P
Baseband Inputs (BI +, BI –, BQ +, BQ –)
Frequency Bandwidth (3dB)
Differential Input Voltage for 1dB Compressed Output
DC Common-Mode Voltage
1.4
VDC
Differential Input Resistance
Internally Biased
18
kΩ
Input Capacitance
0.8
pF
Gain Error
±0.2
Phase Error
±1
DEG
–3
dBm
dB
Modulated RF Carrier Output (MODRFOUT)
Output Power, Max Gain
Output VSWR
–6
ZO = 50Ω
1.5:1
Image Suppression
– 26
–34
Carrier Suppression
– 24
–32
dBc
–3
dBm
2
dBm
Output 1dB Compression
Output 3rd Order Intercept
fI = 100kHz, fQ = 120kHz
Output 2rd Order Intercept
fI = 100kHz, fQ = 120kHz
Broadband Noise
20MHz Offset
dBc
16
dBm
–142
dBm/Hz
VGA Control Logic (GC2, GC1)
Switching Time
Input Current
100
ns
2
µA
Input Low Voltage
0.4
Input High Voltage
1.7
VDC
VDC
Output Power Attenuation
GC2 = Low, GC1 = High
4.5
dB
Output Power Attenuation
GC2 = High, GC1 = Low
9
dB
Output Power Attenuation
GC2 = High, GC1 = High
13.5
dB
1
µs
Modulator Enable (MODEN) Low = Off, High = On
Turn ON/OFF Time
Input Current
µA
105
Enable
VCC – 0.4
VDC
Disable
0.4
VDC
5.25
VDC
38
mA
25
µA
Modulator Power Supply Requirements
Supply Voltage
1.8
Modulator Supply Current
MODEN = High
Modulator Shutdown Current
MODEN = Low
29
3
LT5503
ELECTRICAL CHARACTERISTICS
(Mixer)
VCC2 = 3VDC, 2.4GHz matching, MIXEN = High, DMODE = Low (LO2 ÷ 2 mode), TA = 27ºC, LO2IN = 750MHz at –18dBm, LO1IN =
2075MHz at –12dBm. MIXRFOUT measured at 2450MHz, unless otherwise noted. (Test circuit shown in Figure 2.) (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Mixer 2nd LO Input (LO2IN)
Frequency Range
Input VSWR
50 to 1000
ZO = 50Ω
MHz
1.4:1
Input Power
–20 to –12
dBm
1400 to 2400
MHz
Mixer 1st LO Input (LO1IN)
Frequency Range2
Input VSWR
ZO = 50Ω
1.5:1
Input 3rd Order Intercept
–30dBm/Tone, ∆f = 200kHz
–12
dBm
1700 to 2700
MHz
Mixer RF Output (MIXRFOUT)
Frequency Range2
Output VSWR
ZO = 50Ω
Small-Signal Conversion Gain
PLO1 = –30dBm
1.5:1
5
Output Power
LO1 Suppression
–14.7
–12.7
dBm
– 22
– 29
dBc
–15
dBm
–152
dBm/Hz
Output 1dB Compression
Broadband Noise
dB
20MHz Offset
LO2 Divider Mode Control (DMODE) Low = fLO2 ÷ 2, High = fLO2 ÷ 1
Input Current
µA
1
Input Low Voltage (÷2)
0.4
Input High Voltage (÷1)
VCC – 0.4
VDC
VDC
Mixer Enable (MIXEN) Low = Off, High = On
Turn ON/OFF Time
Input Current
Enable
1
µs
130
µA
VCC – 0.4
VDC
Disable
0.4
VDC
5.25
VDC
15.5
mA
Mixer Power Supply Requirements
Supply Voltage
1.8
Supply Current (÷2 mode)
DMODE = Low, MIXEN = High
11.9
Supply Current (÷1 mode)
DMODE = High, MIXEN = High
10.8
Shutdown Current
MIXEN = Low
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: External component values on the final test circuit shown in
Figure 2 are optimized for operation in the 2.4GHz to 2.5GHz band.
4
mA
10
µA
Note 3: Specifications over the –40°C to 85°C temperature range are
assured by design, characterization and correlation with statistical process
controls.
LT5503
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TYPICAL PERFOR A CE CHARACTERISTICS
(I/Q Modulator)
VCC1 = 3VDC, 2.4GHz matching, MODEN = high, GC1 = GC2 = low (max gain), TA = 27°C, MODRFIN = 2.45GHz at –16dBm, (I–IB) and
(Q–QB) = 100kHz sine at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.)
Modulator Supply Current vs
Supply Voltage
MODEN Current vs Enable
Voltage
Modulator Shutdown Current vs
Supply Voltage
38
100
220
MODEN = LOW
32
TA = 27°C
30
28
26
24
180
10
TA = 85°C
1
TA = 27°C
20
1.8
0.1
1.8
5.3
TA = –40°C
TA = 27°C
120
100
TA = –40°C
40
1.8
5.3
4.6
2.5
3.9
3.2
VCC1 SUPPLY VOLTAGE (V)
5503 G01
MODRFIN and MODRFOUT
Return Loss 2.4GHz Matching
–25
–30
–35
MODRFOUT
–10
–10
RETURN LOSS (dB)
–20
DESIRED
SIDEBAND
–5
OUTPUT POWER (dBm)
–15
0
0
3 VDC
1.8 VDC
5.3
4.6
3.9
3.2
MODEN VOLTAGE (V)
5503 G03
Baseband Frequency Response
I/Q Amplitude = 1VP-P
–10
2.5
5503 G02
SSB Output Power vs
I, Q Amplitude
5.25 VDC
140
60
4.6
2.5
3.9
3.2
VCC1 SUPPLY VOLTAGE (V)
0
TA = 85°C
160
80
TA = –40°C
22
–15
–20
–25
–20
–30
–30
MODRFIN
CARRIER
–40
–35
–45
0.1
10
0.01
1
I, Q DIFFERENTIAL INPUT VOLTAGE (VP-P)
–40
0.1
IMAGE
10
1
I, Q INPUT FREQUENCY (MHz)
5503 G04
5503 G05
–40
2050
2250
2450
2650
FREQUENCY (MHz)
2850
5503 G06
Typical SSB Spectrum
0
–10
–20
–30
POUT (dBm)
SSB OUTPUT POWER (dBm)
INPUT CURRENT (µA)
TA = 85°C
34
–5
MODEN = VCC1
200
SHUTDOWN CURRENT (µA)
SUPPLY CURRENT (mA)
36
–40
–50
–60
–70
–80
–90
–100
2449.6 2449.8 2450.0 2450.2 2450.4
FREQUENCY (MHz)
2450.6
5503 G07
5
LT5503
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TYPICAL PERFOR A CE CHARACTERISTICS
(I/Q Modulator)
2.4GHz matching, MODEN = high, GC1 = GC2 = low (max gain), MODRFIN = 2.45GHz, (I–IB) and (Q–QB) = 100kHz sine at 1VP-P
differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.)
–20
–20
–2
TA = –40°C
–8
TA = 85°C
–10
–12
–14
–16
IMAGE SUPPRESSION (dBc)
–6
CARRIER SUPPRESSION (dBc)
TA = 27°C
–4
SSB OUTPUT POWER (dBm)
Image Suppression vs Input
Power VCC1 = 1.8V
Carrier Suppression vs Input Power
VCC1 = 1.8V
SSB Output Power vs Input Power
VCC1 = 1.8V
–30
TA = 27°C
TA = –40°C
–40
TA = 85°C
–30
TA = 27°C
TA = –40°C
–40
TA = 85°C
–18
–20
–24
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
–50
–24
–10
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
5503 G08
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
Carrier Suppression vs Input Power
VCC1 = 3V
0
–10
5503 G10
5503 G09
SSB Output Power vs Input Power
VCC1 = 3V
Image Suppression vs Input Power
VCC1 = 3V
–20
–20
–4 TA = –40°C
–6
–8
TA = 85°C
–10
–12
–14
–30
IMAGE SUPPRESSION (dBc)
CARRIER SUPPRESSION (dBc)
TA = 27°C
–2
SSB OUTPUT POWER (dBm)
–50
–24
–10
TA = 27°C
TA = –40°C
–40
TA = 85°C
–30
TA = 27°C
TA = –40°C
TA = 85°C
–40
–16
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
–50
–24
–10
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
5503 G11
CARRIER SUPPRESSION (dBc)
SSB OUTPUT POWER (dBm)
TA = –40°C
–6
–8
Image Suppression vs Input Power
VCC1 = 5.25V
–20
–20
TA = 27°C
TA = 85°C
–10
–12
–14
–30
TA = 27°C
TA = –40°C
–40
–10
5503 G13
Carrier Suppression vs Input Power
VCC1 = 5.25V
0
–4
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
5503 G12
SSB Output Power vs Input Power
VCC1 = 5.25V
–2
–50
–24
–10
IMAGE SUPPRESSION (dBc)
–18
–24
TA = 85°C
–30
TA = 27°C
TA = –40°C
TA = 85°C
–40
–16
–18
–24
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
–10
5503 G14
6
–50
–24
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
–10
5503 G15
–50
–24
–22 –20 –18 –16 –14 –12
MODRFIN INPUT POWER (dBm)
–10
5503 G16
LT5503
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TYPICAL PERFOR A CE CHARACTERISTICS
(I/Q Modulator)
VCC1 = 3VDC, MODEN = high, TA = 27°C, PMODRFIN = –16dBm, (I–IB) and (Q–QB) = 100kHz sine at 1VP-P differential, Q leads I by 90°,
unless otherwise noted. (Test circuit shown in Figure 2.)
Output Power vs Frequency
1.2GHz Matching
Carrier Feedthrough vs Frequency
1.2GHz Matching
0
–30
–30
GC2, GC1 = 00
–2
GC2, GC1 = 00
–4
GC2, GC1 = 00
01
–8
–10
–12
10
–14
–40
IMAGE (dBm)
–6
CARRIER (dBm)
SSB OUTPUT POWER (dBm)
SSB Image vs Frequency
1.2GHz Matching
01
10
–50
01
–40
10
11
–50
11
–16
11
–18
–20
1000
1100
1200
1300
MODRFIN FREQUENCY (MHz)
–60
1000
1400
1100
1200
1300
MODRFIN FREQUENCY (MHz)
Output Power vs Frequency
1.9GHz Matching
SSB Image vs Frequency
1.9GHz Matching
–30
–30
GC2, GC1 = 00
GC2, GC1 = 00
1400
5503 G19
Carrier Feedthrough vs Frequency
1.9GHz Matching
2
0
1100
1200
1300
MODRFIN FREQUENCY (MHz)
5503 G18
5503 G17
GC2, GC1 = 00
–2
01
01
–6
–8
10
–10
–12
–40
IMAGE (dBm)
–4
CARRIER (dBm)
SSB OUTPUT POWER (dBm)
–60
1000
1400
10
11
–50
01
–40
10
11
–50
11
–14
–16
1750
1850
1950
2050
MODRFIN FREQUENCY (MHz)
–60
1650
2150
1750
1850
1950
2050
MODRFIN FREQUENCY (MHz)
5503 G20
GC2, GC1 = 00
GC2, GC1 = 00
01
CARRIER (dBm)
SSB OUTPUT POWER (dBm)
–30
GC2, GC1 = 00
01
–8
10
–12
–14
SSB Image vs Frequency
2.4GHz Matching
–30
–4
–10
2150
5503 G22
Carrier Feedthrough vs Frequency
2.4GHz Matching
0
–6
1750
1850
1950
2050
MODRFIN FREQUENCY (MHz)
5503 G21
Output Power vs Frequency
2.4GHz Matching
–2
–60
1650
2150
–40
10
IMAGE (dBm)
–18
1650
11
–50
–40
01
10
11
–50
11
–16
–18
2250
2350
2450
2550
MODRFIN FREQUENCY (MHz)
2650
5503 G23
–60
2250
2350
2450
2550
MODRFIN FREQUENCY (MHz)
2650
5503 G24
–60
2250
2350
2450
2550
MODRFIN FREQUENCY (MHz)
2650
5503 G25
7
LT5503
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TYPICAL PERFOR A CE CHARACTERISTICS
(Mixer)
2.4GHz matching, MIXEN = high, DMODE = low (LO2 ÷ 2 mode), LO2IN = 750MHz at –18dBm, LO1IN = 2075MHz. MIXRFOUT measured
at 2450MHz, unless otherwise noted. (Test circuit shown in Figure 2.)
Mixer Supply Current vs Supply
Voltage (LO2 ÷ 2 Mode)
14
14
100
DMODE = HIGH
TA = 85°C
MIXEN = LOW
SUPPLY CURRENT (mA)
TA = 27°C
12
11
TA = –40°C
10
SHUTDOWN CURRENT (µA)
13
13
SUPPLY CURRENT (mA)
Mixer Shutdown Current vs Supply
Voltage
Mixer Supply Current vs Supply
Voltage (LO2 ÷ 1 Mode)
TA = 85°C
12
TA = 27°C
11
10
TA = –40°C
9
9
8
8
10
TA = 85°C
1
TA = 27°C
1.8
5.3
2.5
3.2
3.9
4.6
VCC2 SUPPLY VOLTAGE (V)
0.1
1.8
RF Output Power vs LO1 Input
Power (VCC2 = 1.8V)
–12
–14
MIXRFOUT POWER (dBm)
–18
TA = 27°C
–20
TA = 85°C
–22
–24
–16
–14
TA = –40°C
MIXRFOUT POWER (dBm)
–14
–18
TA = 27°C
–20
TA = 85°C
–22
–24
–26
–26
–28
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–16
TA = –40°C
–18
TA = 27°C
–20
TA = 85°C
–22
–24
–26
–28
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–6
–28
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–6
1195 G30
1195 G29
LO1 Feedthrough vs LO1 Input
Power (VCC2 = 1.8V)
–6
1195 G31
LO1 Feedthrough vs LO1 Input
Power (VCC2 = 5.25V)
LO1 Feedthrough vs LO1 Input
Power (VCC2 = 3V)
–20
–20
–20
5.3
RF Output Power vs LO1 Input
Power (VCC2 = 5.25V)
–12
–12
–16
TA = –40°C
2.5
3.2
3.9
4.6
VCC2 SUPPLY VOLTAGE (V)
5503 G28
RF Output Power vs LO1 Input
Power (VCC2 = 3V)
TA = –40°C
1.8
5503 G27
5503 G26
MIXRFOUT POWER (dBm)
5.3
2.5
3.2
3.9
4.6
VCC2 SUPPLY VOLTAGE (V)
TA = 27°C
TA = 85°C
–30
–35
–40
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–6
1195 G32
8
–25
LO1 FEEDTHROUGH (dBc)
–25
LO1 FEEDTHROUGH (dBc)
LO1 FEEDTHROUGH (dBc)
TA = –40°C
TA = 85°C
TA = 27°C
–30
TA = –40°C
–35
–40
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–6
1195 G33
–25
TA = 27°C
TA = 85°C
TA = –40°C
–30
–35
–40
–30 –27 –24 –21 –18 –15 –12 –9
LO1IN POWER (dBm)
–6
1195 G34
LT5503
U W
TYPICAL PERFOR A CE CHARACTERISTICS
(Mixer)
VCC2 = 3VDC, MIXEN = high, DMODE = low (LO2 ÷ 2mode), TA = 27°C, unless otherwise noted. (Test circuit shown in Figure 2.)
RF Output Power and LO1
Feedthrough 1.9GHz Matching
Small-Signal Conversion Gain
and IIP3 1.9GHz Matching
0
6
–14
–10
4
–16
–20
–18
–30
–12
LO1IN and MIXRFOUT Return Loss
1.9GHz Matching
0
–3
–40
–20
–22
1650
IIP3
LO2IN = 480MHz AT –18dBm
LO1IN = fRF –240MHz AT –30dBm/TONE
–4
1650
1750
1950
2050
1850
RF OUTPUT FREQUENCY (MHz)
5503 G35
6
–10
4
LO1
FEEDTHROUGH
–30
–18
–40
–20
–18
2150
–30
1100 1300 1500 1700 1900 2100 2300 2500
FREQUENCY (MHz)
5503 G37
LO1 and MIXRFOUT Return Loss
2.4GHz Matching
SMALL-SIGNAL
CONVERSION
GAIN
–9
IIP3
0
–12
–15
LO2IN = 750MHz AT –18dBm
LO1IN = fRF –375MHz AT –30dBm/TONE
–4
2250
–5
–6
–2
–50
2650
0
–3
2
LO2IN = 750MHz AT –18dBm
LO1IN = fRF –375MHz AT –12dBm
2350
2550
2450
RF OUTPUT FREQUENCY (MHz)
5503 G38
–18
2650
5503 G39
–10
MIXRFOUT
–15
LO1
–20
–25
–30
1450 1650 1850 2050 2250 2450 2650 2850
FREQUENCY (MHz)
5503 G40
MIXEN Input Current vs Enable
Voltage (MIXEN = VCC2)
300
270
TA = 85°C
240
INPUT CURRENT (µA)
2350
2550
2450
RF OUTPUT FREQUENCY (MHz)
–25
IIP3 (dBm)
–20
–16
CONVERSION GAIN (dB)
0
LO1 (dBc)
RF OUTPUT (dBm)
OUTPUT
POWER
MIXRFOUT
–20
Small-Signal Conversion Gain
and IIP3 2.4GHz Matching
–12
–22
2250
–15
5503 G36
RF Output Power and LO1
Feedthrough 2.4GHz Matching
–14
–10
LO1IN
–15
–2
–50
2150
1750
1950
2050
1850
RF OUTPUT FREQUENCY (MHz)
–12
0
RETURN LOSS (dB)
LO2IN = 480MHz AT –18dBm
LO1IN = fRF –240MHz AT –12dBm
–9
2
RETURN LOSS (dB)
CONVERSION GAIN (dB)
LO1
FEEDTHROUGH
–5
–6
SMALL-SIGNAL
CONVERSION
GAIN
IIP3 (dBm)
LO1 (dBc)
RF OUTPUT (dBm)
OUTPUT
POWER
210
TA = –40°C
180
150
TA = 27°C
120
90
60
30
1.8
2.5
3.9
3.2
MIXEN VOLTAGE (V)
4.6
5.3
5503 G41
9
LT5503
U
U
U
PI FU CTIO S
BQ– (Pin 1): Negative Baseband Input Pin of the Modulator
Q-Channel. This pin is internally biased to 1.4V, but can
also be overdriven with an external DC voltage greater than
1.4V, but less than VCC – 0.4V.
MIXEN (Pin 12): Mixer Enable Pin. When the input voltage
is higher than VCC – 0.4V, the mixer circuits supplied
through pins 8, 10, 11 and 15 are enabled. When the input
voltage is less than 0.4V, these circuits are disabled.
BQ+ (Pin 2): Positive Baseband Input Pin of Modulator QChannel. This pin is internally biased to 1.4V, but can also
be overdriven with an external DC voltage greater than
1.4V, but less than VCC – 0.4V.
MODEN (Pin 13): Modulator Enable Pin. When the input
voltage is higher than VCC – 0.4V, the modulator circuits
supplied through pins 5, 6, 16 and 17 are enabled. When
the input voltage is less than 0.4V, these circuits are
disabled.
GC1 (Pin 3): Gain Control Pin. This pin is the least
significant bit of the four-step modulator gain control.
MODIN (Pin 4): Modulator Carrier Input Pin. This pin is
internally biased and should be AC-coupled. An external
matching network is required for a 50Ω source.
VCCMOD (Pin 5): Power Supply Pin for the I/Q Modulator.
This pin should be externally connected to the other VCC
pins and decoupled with 1000pF and 0.1µF capacitors.
VCCRF (Pin 6): Power Supply Pin for the I/Q Modulator
Input RF Buffer and Phase Shifter. This pin should be
externally connected to the other VCC pins and decoupled
with 1000pF and 0.1µF capacitors.
LO1 (Pin 7): Mixer 1st LO Input Pin. This pin is internally
biased and should be AC-coupled. An external matching
network is required for a 50Ω source.
VCCLO1 (Pin 8): Power Supply Pin for the Mixer LO1
Circuits. This pin should be externally connected to the
other VCC pins and decoupled with 1000pF and 0.1µF
capacitors.
DMODE (Pin 9): Mixer 2nd LO Divider Mode Control Pin.
Low = divide-by-2, High = divide-by-1.
MX+ (Pin 10): Mixer Positive RF Output Pin. This pin must
be connected to VCC through an external matching network.
MX– (Pin 11): Mixer Negative RF Output Pin. This pin must
be connected to VCC through an external matching network.
10
LO2 (Pin 14): Mixer 2nd LO Input Pin. This pin is internally
biased and should be AC-coupled. An external matching
network is not required, but can be used for improved
matching to a 50Ω source.
VCCLO2 (Pin 15): Power Supply Pin for the Mixer LO2
Circuits. This pin should be externally connected to the
other VCC pins and decoupled with 1000pF and 0.1µF
capacitors.
VCCVGA (Pin 16): Power Supply Pin for the Modulator
Variable Gain Amplifier. This pin should be externally
connected to the other VCC pins through a 47Ω resistor
and decoupled with a good high frequency capacitor (2pF
typical) placed close to the pin.
MODOUT (Pin 17): Modulator RF Output Pin. This pin
must be externally biased to VCC through a bias choke. An
external matching network is required to match to 50Ω.
GC2 (Pin 18): Gain Control Pin. This pin is the most
significant bit of the four-step modulator gain control.
BI+ (Pin 19): Positive Baseband Input Pin of the Modulator
I-Channel. This pin is internally biased to 1.4V, but can also
be overdriven with an external DC voltage greater than
1.4V, but less than VCC – 0.4V.
BI– (Pin 20): Negative Baseband Input Pin of the Modulator I-Channel. This pin is internally biased to 1.4V, but can
also be overdriven with an external DC voltage greater than
1.4V, but less than VCC – 0.4V.
GROUND (Backside Contact): Circuit Ground Return for
the Entire IC.
LT5503
W
BLOCK DIAGRA
BQ+
BQ–
1
2
BI–
20
V-I
BI+
19
V-I
VCCMOD 5
16 VCCVGA
VGA
17 MODOUT
VCCRF 6
18 GC2
RF
BUFFER
90°
CONTROL
LOCIC
0°
3 GC1
MODIN 4
VCCLO1 8
MODULATOR BIAS CIRCUITS
13 MODEN
MIXER BIAS CIRCUITS
12 MIXEN
LO1
BUFFER
15 VCCLO2
LIM
LO1 7
21
GND
(BACKSIDE)
10
11
MX+ MX–
÷2
÷1
9
LIM
14 LO2
5503 BD
DMODE
11
LT5503
TEST CIRCUIT
21 (BACKSIDE)
C17
1µF
QB
Q
GND
LT5503
1
BQ –
BI –
20
2
BQ+
BI+
19
C15
1µF
3
GC1
GC1
18
GC2
C18
1µF
IB
I
C16
1µF
GC2
C2
L2
C3
L3
4
MODRFIN
MODIN
MODRFOUT
17
MODOUT
R2
47Ω
C10
5
16
VCCMOD VCCVGA
C4
6
L4
7
LO1IN
VCCRF
15
VCCLO2
LO1
C7
C11
8
C43
8.2pF
9
DMODE
10
C12
1000pF
L5
VCCLO1
MODEN
DMODE
MIXEN
MX +
13
12
VCC1
C19
0.01µF
C22
1000pF
14
LO2
C23
R1
C1
2.2pF
VCC1
C20
1000pF
L1
LO2IN
MODEN
C14
100pF
MIXEN
11
MX –
L6
C13
8.2pF
VCC2
C21
0.01µF
C5
4
2
1
C9
3
C6
5
T1
NOTE: VCC1 AND VCC2 POWER THE
MODULATOR AND UPMIXER
SECTIONS RESPECTIVELY.
MIXRFOUT
5503 F02
Application Dependent Component Values
1.2GHz Matching
(Modulator Only)
1.9GHz Matching
2.4GHz Matching
L1
33nH
22nH
18nH
L2
12nH
5.6nH
2.7nH
L3
12nH
4.7nH
2.7nH
C2, C3, C7
39pF
15pF
8.2pF
C10
2.7pF
1.8pF
1.2pF
C23
n/a
1.5pF
1.5pF
R1
240Ω
390Ω
390Ω
C4
n/a
15pF
8.2pF
C5, C6
n/a
1.8pF
2.2pF
C9
n/a
15pF
2.7pF
C11
n/a
2.2pF
1.2pF
L4
n/a
6.8nH
4.7nH
L5,L6
n/a
5.6nH
2.2nH
T1
n/a
LDB15C101A1900
LDB15C500A2400
Figure 2. Test Schematic for 1.2GHz, 1.9GHz and 2.4GHz Applications
12
LT5503
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The LT5503 consists of a direct quadrature modulator and
a mixer. The mixer operates over the range of 1.7GHz to
2.7GHz, and the modulator operates with an output range
of 1.2GHz to 2.7GHz. The LT5503 is designed specifically
for high accuracy digital modulation with supply voltages
as low as 1.8V. It is suitable for IEEE 802.11b wireless local
area network (WLAN), MMDS and wireless local loop
(WLL) transmitters.
bandpass filter loss. The balanced output from the modulator is applied to a variable gain amplifier (VGA) that
provides a single-ended output. Note that the modulator
can also be used independently of the mixer, freeing the
mixer to be used anywhere in the system. In this case,
MODRFIN will be driven from an external frequency source.
A dual-conversion RF system requires two local oscillators to convert signals between the baseband and RF
domains (see Figure 3). The LT5503’s double-balanced
mixer can be used to generate the LT5503 modulator’s
high frequency carrier input (MODRFIN) by mixing the
systems 1st and 2nd local oscillators (LO1 and LO2). In
this case, a bandpass filter is required to select the desired
mixer output for the modulator input. The mixer’s RF
differential output produces –12dBm typically at 2.45GHz
and the modulator MODIN pin requires ≥ –16dBm, driven
single-ended. This allows approximately 4dB margin for
The baseband I and Q inputs (BI+/BI – and BQ+/BQ –) are
internally biased to 1.4V to maximize the input signal
range at low supply voltage. This bias voltage is stable over
temperature, and increases by approximately 50mV at the
maximum supply voltage. The modulator I and Q inputs
have very wide bandwidth (120MHz typical), making the
LT5503 suitable for even the most wideband modulation
applications. For best carrier suppression and lowest
distortion, differential input drive should be used. Singleended drive is possible too, with the unused inputs ACcoupled to ground.
Modulator Baseband
LT5502
I
A/D
90°
LNA
÷2
0°
Q
1ST LO
A/D
2ND LO
LT5503
VGA
÷2
90°
0°
I
Q
÷1
D/A
D/A
5503 F03
Figure 3. Example System Block Diagram for a Dual Conversion System
13
LT5503
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AC-Coupled Baseband. Figure 4 shows the simplified
circuit schematic of a high-pass AC-coupled baseband
interface.
CCPL
BI+ LT5503
CCPL
BI–
I
18k
0.8pF
Figure 5 shows a simplified circuit schematic for interfacing the LT5503’s baseband inputs to the outputs of a D/A
converter. OIP and OIN are the positive and negative
baseband outputs, respectively, of the converter’s
I-channel. Similarly, OQP and OQN are the positive and
negative baseband outputs, respectively, of the converter’s
Q-channel.
IB
0.8pF
CCPL
BI+ LT5503
IINPUT
BI–
IINPUT
BQ
+
IINPUT
BQ–
BQ+
Q
CCPL
IINPUT
OIP
BQ–
18k
0.8pF
18k
0.8pF
OIN
0.8pF
D/A
QB
0.8pF
OQP
5505 F04
Figure 4. AC-Coupled Baseband Interface
18k
0.8pF
OQN
0.8pF
With approximately 18k of differential input resistance,
the suggested minimum AC-coupling capacitor can be
determined using the following equation:
C CPL =
1
(18 • 103 • π • fC )
where fC is the 3dB cut-off frequency of the baseband input
signal.
A larger capacitor may be used where the settling time of
charging and discharging the AC-coupling capacitor is not
critical.
DC-Coupled Baseband. The baseband inputs’ internal bias
voltage can be overdriven with an external bias circuit.
This facilitates direct interfacing to a D/A converter for
faster transient response. In this case, the LT5503’s
baseband inputs are DC biased by the converter. The
optimal VBIAS is 1.4V, independent of VCC. In general, the
maximum VBIAS should be less than VCC – 0.4V. The DC
load on each converter output can be approximated using
the following equation where IINPUT is the current flowing
into a modulator input:
IINPUT
14
V
− 1.4V
= BIAS
9kΩ
5505 F05
Figure 5. DC-Coupled Baseband Interface
Modulator RF Input (MODRFIN)
The modulator RF input buffer is driven single-ended. An
internal active balun circuit produces balanced signals to
drive the integrated phase shifter. Limiters following the
phase shifter output accommodate a wide range of
MODRFIN power, resulting in minimal degradation of
modulation gain/phase accuracy performance or carrier
feedthrough. This pin is easily matched to a 50Ω source
with the simple lowpass network shown in Figure 2. This
pin is internally biased, therefore an AC-coupling capacitor is required.
Modulator VGA (Variable Gain Amp)
The VGA has two digital selection lines to provide a
nominal 0dB, 4.5dB, 9dB and 13.5dB attenuation from the
maximum modulator output power setting. The logic table
is shown below:
GC2
Attenuation
GC1
Low
High
Low
0dB
9dB
High
4.5dB
13.5dB
LT5503
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APPLICATIO S I FOR ATIO
Pin 16 should be connected externally to VCC through a
low value series resistor (47Ω typical). To assure proper
output power control, a good, local high frequency AC
ground for Pin 16 is essential. The MODOUT port of the
VGA is an open collector configuration. An inductor with
high self resonance frequency is required to connect
Pin 17 to VCC as a DC return path, and as a part of the
output matching network. Additional matching components are required to drive a 50Ω load as shown in
Figure␣ 2. The amplifier is designed to operate in Class A for
low distortion performance. The typical output 1dB compression point (P1dB) is –3dBm at 2.45GHz. When the
differential baseband input voltages are higher than 1VP-P,
the VGA operates in Class AB mode, and the distortion
performance of the modulator is degraded. The logic
control inputs do not draw current when they are low. They
draw about 2µA each when high.
Mixer LO1 Port
The mixer LO1 input port is the linear input to the mixer.
It consists of an active balun amplifier designed to operate
over the 1.4GHz to 2.4GHz frequency range. There is a
linear relationship between LO1 input power and
MIXRFOUT power for LO1 input levels up to approximately
–20dBm. After that, the mixer output begins to compress.
When operated in the recommended –14dBm to –8dBm
input power range, the mixer is well compressed, which in
turn creates a stable output level for the modulator input.
As shown in Figure 2, a simple lowpass matching network
is required to match this pin to 50Ω. This pin is internally
biased, therefore an AC-coupling capacitor is required.
MX + 10
Mixer LO2 Port
The mixer LO2 port is designed to operate in the 50MHz to
1000MHz range. The first stage is a limiting amplifier. This
stage produces the correct output levels to drive the
internal divider circuit reliably, with LO2 input levels down
to –20dBm. The output of the divider then drives another
stage, which in turn switches the nonlinear inputs of the
double-balanced mixer. Note that the mixer output will
produce broadband noise if the LO2 signal level is too low.
The input amplifier is designed for a good match over the
entire frequency range. The only requirement (Figure 2) is
an external AC-coupling capacitor.
Mixer Output Ports (MX+/MX–)
The mixer output is a differential open collector configuration. Bias current is supplied to these two pins through the
center tap of a balun as shown in Figure 2. Simple lowpass
matching is used to transform each leg of the mixer output
to 25Ω for the balun’s 50Ω input impedance.
The balun approach provides the highest output power
and best LO1 suppression, but is not absolutely necessary. It is also possible to match each output to 50Ω and
couple power from one output. The unused output should
be terminated in the same characteristic impedance. In
this case, output power is approximately 2dB lower and
LO1 suppression degrades to approximately 15dBc. A
schematic for this approach is shown in Figure 6 where
inductors LB + and LB – supply bias current to the mixer’s
differential outputs, and resistor RTERM terminates the
unused output.
11 MX –
L5
LB+
VCC
L6
LB–
RTERM
51Ω
C5
1.9GHz
2.4GHz
L5,L6
5.6nH
2.7nH
C5, C6
1.8pF
0.68pF
C9
15pF
8.2pF
C6
C9
MIXRFOUT
CBYPASS
5503 F06
Figure 6. 50Ω Mixer Output Matching Without a Balun
15
LT5503
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EVALUATION BOARD
RF Layout Tips:
Figure 7 shows the circuit schematic of the evaluation
board. The MODRFIN, MODRFOUT and MIXRFOUT ports
are matched to 50Ω at 2.45GHz. The LO1IN port is
matched to 50Ω at 2.1GHz and the LO2IN port is internally
matched.
• Use 50Ω impedance transmission lines up to the
matching networks, use of a ground plane is a must.
A 390Ω resistor is used to reduce the quality factor (Q) of
the modulator output and deliver an output power of
–3dBm typically. A lower value resistor may be used if the
desired output power is lower. For example, the output
power will be 3dB lower if a 200Ω resistor is used.
Inductors with high self-resonance frequency should be
used for L1 to L6.
For simpler evaluation in a lab environment, the evaluation
board includes op amps to convert single-ended I and Q
input signals to differential . The op amp configuration has
a voltage gain of two; therefore the peak baseband input
voltage should be halved to maintain the same RF output
power. The op amp configuration shown will maintain
acceptable differential balance up to 10MHz typically. It is
also possible to bypass the op amps and drive the
modulator’s differential inputs directly by connecting to
the four oversized vias on the board (V1, V2, V3 and V4).
Figure 7 also shows a table of matching network values for
designs centered at 1.9GHz and1.2GHz.
Figure 8 shows the evaluation board with connectors and
ICs. Figure 9 shows the test set-up with the upconverting
mixer and IQ modulator connected in a transmit configuration. Refer to the demo board DC365A Quick Start Guide
for detailed testing information.
16
• Keep the matching networks as close to the pins as
possible.
• Surface mount 0402 outline (or smaller) parts are
recommended to minimize parasitic inductances and
capacitances.
• Isolate the MODOUT pin from the LO2 input by putting
the LO2 transmission line on the bottom side of the
board.
• The only ground connection is through the exposed pad
on the bottom of the package. This exposed pad must
be soldered to the board in such a way to get complete
RF contact.
• Low impedance RF ground connections are essential
and can only be obtained by one or more vias tying
directly into the ground plane.
• VCC lines must be decoupled with low impedance,
broadband capacitors to prevent instability.
• Separate power supply lines should be used to isolate
the MODIN signal and other stray signals from the
MODOUT line. If possible, power planes should be
used.
• Avoid use of long traces whenever possible. Long RF
traces in particular can lead to signal radiation and
degraded isolation, as well as higher losses.
LT5503
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E4
VCC4
J1
VCC4
C33
4.7µF
5
Q-IN
R3
56Ω
1%
R13
510Ω
1%
C27
0.01µF
C32
4.7µF
C34
4.7µF
C28
4.7µF
8
+
R14
510Ω
1%
6
C29
0.01µF
8
7
U2-1
LT1807
–
7
4 R17
510Ω
1%
C16
1µF
C15
R25 1µF
49.9Ω
C35, 39pF
U3-1
LT1807
R28
49.9Ω
VCC4
2
R23
10k
1%
R19
510Ω
1%
–
3
R12
56Ω
1%
C38, 1pF
U2-2
LT1807
C40
4.7µF
R16
510Ω
1%
C36, 39pF
C37, 1pF
R21
10k
1%
I-IN
R15
510Ω
1%
6
–
R18
4
510Ω
1%
J4
5
+
+
C41
1µF
OPT
1
C17
1µF V1
R26
49.9Ω
1
2
V2
3
*C3
J2
*L3
MODRFIN
R20
510Ω
1%
1
C42
1µF
OPT
4
C18
1µF
V3
LT5503
BQ –
BI –
BQ+
BI+
GC1
GC2
20
5
R22
10k
1%
U3-2
LT1807
R27
49.9Ω
+
3
C39
4.7µF
R24
10k
1%
V4
*C2
*L2
18
J5
MODRFOUT
17
MODIN
VCC4
2
19
*L1
MODOUT
*C23
*R1
R2
47Ω
*C10
E1
–
16
VCC1
VCCMOD VCCVGA
VCC1
C20
1000pF
*C4
J3
*L4
LO1IN
C43
8.2pF
E3 R29
10Ω
9
C12
1000pF
10
SW1
12
11
10
9
8
7
R5
20k
R6
20k
15
VCCRF
VCCLO2
14
LO1
C14
100pF
VCC2
J6
LO2IN
LO2
C22
1000pF
13
VCCLO1
MODEN
DMODE
MIXEN
C1
2.2pF
*C7
C19
0.01µF
*C11
C45
0.1µF
1
2
3
4
5
6
7
8
VCC2
VCC3
C24
4.7µF
6
R7
20k
R8
2.7k
R4
2.7k
12
MX +
*L5
GND
21
MX –
*L6
*C5
E2
11
*C6
VCC2
C21
0.01µF
C13
8.2pF
J7
MIXER
OUT
*C9
4
2
1
3
5
T1
5503 F07
L1
L2
L3
C2, C3, C7
C10
C23
R1
C4
C5, C6
C9
C11
L4
L5,L6
T1
*Application Dependent Component Values
1.2GHz Matching
(Modulator Only) 1.9GHz Matching 2.4GHz Matching
33nH
22nH
18nH
12nH
5.6nH
2.7nH
12nH
4.7nH
2.7nH
39pF
15pF
8.2pF
2.7pF
1.8pF
1.2pF
n/a
1.5pF
1.5pF
240Ω
390Ω
390Ω
n/a
15pF
8.2pF
n/a
1.8pF
2.2pF
n/a
15pF
2.7pF
n/a
2.2pF
1.2pF
n/a
6.8nH
4.7nH
n/a
5.6nH
2.2nH
n/a
LDB15C101A1900 LDB15C500A2400
Figure 7. Evaluation Circuit Schematic for 1.2GHz, 1.9GHz and 2.4GHz Applications
17
LT5503
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QIN
IIN
VCC4
GND
VCC1
LT1807
V2
LT1807
V3
V4
V1
MODRFIN
MODRFOUT
LT5503
IC
LO1IN
LO2IN
GND
1
2
3
4
5
6
VCC2
VCC3
5503 F08
MIXRFOUT
Figure 8. LT5503 Evaluation Board Layout
18
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+
–
DUAL SIGNAL
GENERATOR
POWER SUPPLY 4
0°
+
90°
–
QIN
POWER SUPPLY 1
IIN
VCC4
GND
LT1807
MODRFIN
V2
SPECTRUM
ANALYZER
LT1807
V3
V1
V4
MODRFOUT
SIGNAL
GENERATOR 1
SIGNAL
GENERATOR 1
LT5503
IC
1
2
3
4
5
6
LO1IN
GND VCC2
LO2IN
VCC3
+
–
+
POWER SUPPLY 2
POWER SUPPLY 3
MIXRFOUT
–
EXTERNAL 3dB
ATTENUATOR PAD,
OR 2.45GHz BPF
5503 F09
Figure 9. Test Set-Up for Upconverting Mixer and
I/Q Modulator Transmit Chain Measurements.
19
LT5503
U
PACKAGE DESCRIPTIO
FE Package
20-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
6.40 – 6.60*
(.252 – .260)
5.2
(.205)
20 1918 17 16 15 14 1312 11
3.0
6.25 – 6.50
(.118) (.246 – .256)
1 2 3 4 5 6 7 8 9 10
1.15
(.0453)
MAX
4.30 – 4.48**
(.169 – .176)
0° – 8°
.105 – .180
(.0041 – .0071)
.65
(.0256)
BSC
.50 – .70
(.020 – .028)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
.18 – .26
(.0071 – .0102)
.05 – .15
(.002 – .006)
FE20 TSSOP 0501
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
RELATED PARTS
PART NUMBER
DESCRIPTION
LT5502
400MHz Quadrature IF Demodulator with RSSI
20
COMMENTS
Linear Technology Corporation
5503i LT/TP 1001 1.5K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
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www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2001