MAX2450 [MAXIM]
3V, Ultra-Low-Power Quadrature Modulator/Demodulator; 3V ，超低功耗正交调制器/解调器
| 型号： | MAX2450 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 3V, Ultra-Low-Power Quadrature Modulator/Demodulator |
| 文件： | 总8页 (文件大小：109K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0455; Rev 1; 9/98
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
MAX2450
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX2450 combines a quadrature modulator and
quadrature demodulator with a supporting oscillator and
divide-by-8 prescaler on a monolithic IC. It operates
from a single +3V supply and draws only 5.9mA. The
demodulator accepts an amplified and filtered IF signal
in the 35MHz to 80MHz range, and demodulates it into I
and Q baseband signals with 51dB of voltage conver-
sion gain. The IF input is terminated with a 400Ω thin-
film resistor for matching to an external IF filter. The
baseband outputs are fully differential and have 1.2Vp-p
signal swings. The modulator accepts differential I and
Q baseband signals with amplitudes up to 1.35Vp-p
and bandwidths to 15MHz, and produces a differential
IF signal in the 35MHz to 80MHz range.
♦ Combines Quadrature Modulator and
Demodulator
♦ Integrated Quadrature Phase Shifters
♦ On-Chip Oscillator (Requires External Tuning
Circuit)
♦ On-Chip Divide-by-8 Prescaler
♦ Modulator Input Bandwidth Up to 15MHz
♦ Demodulator Output Bandwidth Up to 9MHz
♦ 51dB Demodulator Voltage Conversion Gain
♦ CMOS-Compatible Enable
♦ 5.9mA Operating Supply Current
Pulling the CMOS-compatible ENABLE pin low shuts
down the MAX2450 and reduces the supply current to
less than 1µA. To minimize spurious feedback, the
MAX2450’s internal oscillator is set at twice the IF via
external tuning components. The oscillator and associ-
ated phase shifters produce differential signals exhibit-
ing low a mp litud e a nd p ha s e imb a la nc e , yie ld ing
modulator sideband rejection of 38dB. The MAX2450
comes in a QSOP package.
1µA Shutdown Supply Current
Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
PIN-PACKAGE
MAX2450CEP
0°C to +70°C
20 QSOP
Ap p lic a t io n s
Digital Cordless Phones
Fu n c t io n a l Dia g ra m
GSM and North American Cellular Phones
Wireless LANs
17
I _OUT
16
Digital Communications
I_OUT
DEMODULATOR
Two-Way Pagers
20
IF_IN
BIAS
P in Co n fig u ra t io n
15
14
Q_OUT
Q_OUT
400Ω
TOP VIEW
IF_OUT
IF_OUT
GND
IF_IN
GND
V
1
2
20
19
0°
9
10
11
÷ 2
÷ 4
LO_V
PRE_OUT
CC
PRESCALER
TANK
TANK
QUADRATURE
PHASE
GENERATOR
3
18 CC
12
13
I_IN
I_OUT
4
17
16
15
14
13
12
11
90°
÷ 2
LOCAL
OSCILLATOR
LO_GND
MAX2450
MAX2450
I_IN
I_OUT
Q_OUT
Q_OUT
LO_GND
TANK
5
4
5
I_IN
I_IN
Q_IN
6
1
2
Q_IN
IF_OUT
IF_OUT
7
MODULATOR
Σ
6
7
ENABLE
PRE_OUT
Q_IN
Q_IN
8
9
18
V
CC
MASTER BIAS
BANDGAP BIAS
LO_V
CC
TANK
10
3, 19
GND
8
QSOP
ENABLE
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
ABSOLUTE MAXIMUM RATINGS
V
CC
, LO_V to GND............................................-0.3V to +4.5V
Continuous Power Dissipation (T = +70°C)
A
CC
ENABLE, TANK, TANK, I_IN, I_IN, Q_IN,
Q_IN to GND..................................................-0.3V to (V + 0.3V)
IF_IN to GND .........................................................-0.3V to +1.5V
QSOP (derate 9.1mW/°C above +70°C)......................727mW
Operating Temperature Range ...............................0°C to +70°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10sec) .............................+300°C
CC
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
MAX2450
DC ELECTRICAL CHARACTERISTICS
(V = LO_V = TANK = 2.7V to 3.3V, ENABLE = V - 0.4, GND = LO_GND = 0V, I_IN = I_IN = Q_IN = Q_IN = IF_IN = TANK =
CC
CC
CC
OPEN, T = 0°C to +70°C, unless otherwise noted.)
A
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
, LO_V
CONDITIONS
MIN
TYP
MAX
3.3
UNITS
V
V
CC
2.7
CC
I
5.9
2
8.2
mA
µA
µs
CC(ON)
Shutdown Supply Current
Enable/Disable Time
ENABLE Bias Current
ENABLE High Voltage
ENABLE Low Voltage
I
ENABLE = 0.4V
ENABLE = V
20
CC(OFF)
t
10
1
ON/OFF
I
EN
3
µA
V
CC
V
ENH
V
- 0.4
CC
V
ENL
0.4
V
V
,
I_IN, I_IN, Q_IN, Q_IN
Self-Bias DC Voltage Level
I_IN/I_IN
1.25
35
1.5
44
1.75
V
V
Q_IN/Q_IN
Modulator Differential Input
Impedance
Z
,
I_IN/I_IN
kΩ
Z
Q_IN/Q_IN
IF_OUT, IF_OUT DC Bias Voltage
Demodulator IF Input Impedance
V
V
CC
- 1.5
V
IF_OUT/IF_OUT
Z
320
400
±11
480
±50
Ω
IF_IN
Demodulator I and Q Baseband
DC Offset
mV
V
V
,
I_OUT, I_OUT, Q_OUT, Q_OUT
DC Bias Voltage Level
I_OUT/I_OUT
1.2
V
Q_OUT/Q_OUT
AC ELECTRICAL CHARACTERISTICS
(MAX2450 EV kit, V = LO_V = ENABLE = 3.0V, f = 140MHz, f
= f
Q_IN/Q_IN
= 600kHz, V
= V
= 1.2V
,
CC
CC
LO
I_IN I_IN
I_IN/I_IN
Q_IN/Q_IN
/
p-p
f
= 70.1MHz, V
= 2.82mV , T = +25°C, unless otherwise noted.)
IF_IN A
p-p
IF_IN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DEMODULATOR
I and Q Amplitude Balance
I and Q Phase Accuracy
Voltage Conversion Gain
< ±0.45
< ±1.3
51
dB
degrees
dB
Allowable I and Q Voltage Swing
Noise Figure
(Note 1)
1.35
160
V
p-p
NF
18
-44
-60
9
dB
dBc
I and Q IM3 Level
IM3
IM5
(Note 2)
(Note 2)
I/Q
I/Q
I and Q IM5 Level
dBc
I and Q Signal 3dB Bandwidth
Oscillator Frequency Range
LO Phase Noise
BW
MHz
MHz
dBc/Hz
DEMOD
f
LO
(Notes 1, 3)
10kHz offset
70
-80
0.35
60
PRE_OUT Output Voltage
PRE_OUT Slew Rate
V
R
L
R
L
= 10kΩ, C < 6pF
V
p-p
PRE_OUT
L
SR
= 10kΩ, C < 6pF, rising edge
V/µs
PRE_OUT
L
2
_______________________________________________________________________________________
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
MAX2450
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2450 EV kit, V = LO_V = ENABLE = 3.0V, f = 140MHz, f
= f
Q_IN/Q_IN
= 600kHz, V
= V = 1.2V
,
p-p
CC
CC
LO
I_IN/I_IN
I_IN/I_IN
Q_IN/Q_IN
f
= 70.1MHz, V
= 2.82mV , T = +25°C, unless otherwise noted.)
IF_IN A
p-p
IF_IN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MODULATOR
V
,
I_IN/I_IN
Allowable Differential Input Voltage
(Note 1)
1.35
1.75
V
p-p
V
Q_IN/Q_IN
Input Common-Mode Voltage Range
I and Q Signal 3dB Bandwidth
1.25
V
BW
15
65
MHz
MOD
V
, = V
Q_IN/Q_IN = 1.2Vp-p,
I_IN/I_IN
IF Differential Output Voltage
IF Output IM3 Level
V
mV
p-p
IF_OUT/IF_OUT
R
C
= 200kΩ differential,
< 5pF differential
L
L
V
= 1.35Vp-p composite
I_IN/I_IN
(Note 4)
IM3
IM5
-60
dBc
IF
IF
V
= 1.35Vp-p composite
I_IN/I_IN
IF Output IM5 Level
Sideband Rejection
-60
38
dBc
dBc
dBc
(Note 4)
Carrier Suppression at Modulator
Output
-36
Note 1: Guaranteed by design, not tested.
Note 2: f = 2 tones at 70.10MHz and 70.11MHz. V
= 1.41mVp-p per tone.
IF_IN
IF_IN
Note 3: The frequency range can be extended in either direction, but has not been characterized. At higher frequencies, the
modulator IF output amplitude may decrease and distortions may increase.
Note 4: Q_IN/Q_IN ports are terminated. f
= 2 tones at 550kHz and 600kHz.
I_IN/I_IN
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(MAX2450 EV kit, V = LO_V = ENABLE = 3.0V, f = 140MHz, f
= f
= 600kHz, V
= V = 1.2V
,
CC
CC
LO
I_IN/I_IN
Q_IN/Q_IN
I_IN/I_IN
Q_IN/Q_IN
p-p
f
= 70.1MHz, V
= 2.82mV , T = +25°C, unless otherwise noted.)
IF_IN A
p-p
IF_IN
SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MODULATOR IF OUTPUT
vs. BASEBAND INPUT
-30
-34
7.0
12
10
6.8
6.6
V
CC
= 3.3V
V
CC
= 3.3V
V
CC
= 3.0V
6.4
6.2
6.0
-38
-42
-46
8
6
4
V
CC
= 2.7V
V
CC
= 3.0V
5.8
5.6
dBV
RMS
5.4
5.2
5.0
Vp-p = 2 2 x 10 20 (V)
-50
-54
2
0
V = 2.7V
CC
-26
-22
-18
-14
-10
-6
0
10
20 30 40 50 60 70 80
TEMPERATURE (°C)
0
10 20 30 40
TEMPERATURE (°C)
60 70 80
50
BASEBAND INPUT (dBV
)
RMS
_______________________________________________________________________________________
3
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(MAX2450 EV kit, V = LO_V = ENABLE = 3.0V, f = 140MHz, f
= f
Q_IN/Q_IN
= 600kHz, V
= V = 1.2V
,
CC
CC
LO
I_IN/I_IN
I_IN/I_IN
Q_IN/Q_IN
p-p
f
= 70.1MHz, V
= 2.82mV , T = +25°C, unless otherwise noted.)
IF_IN
IF_IN
A
p-p
MODULATOR IF OUTPUT
vs. SUPPLY VOLTAGE
MODULATOR IF OUTPUT
vs.TEMPERATURE
MODULATOR SIDEBAND REJECTION
vs. IF FREQUENCY
70
70
68
66
64
-30
-32
-34
V
= 1.2Vp-p
V
CC
= 3V
I_IN/I_IN
V
= 1.2Vp-p
Q_IN/Q_IN
68
66
64
MAX2450
T = +70°C
A
-36
-38
-40
T = +25°C
A
T = 0°C
A
62
60
62
60
-42
-44
2.7
2.8
2.9
3.0
3.1
3.2
3.3
45 50 55 60 65 70
IF FREQUENCY (MHz)
0
20
40
60
80
35 40
75 80
V
(V)
TEMPERATURE (°C)
CC
MODULATOR SIDEBAND REJECTION
vs. TEMPERATURE
CARRIER SUPPRESSION
vs. IF FREQUENCY
PRE_OUT WAVEFORM
-36
-38
-40
-30
-32
-34
V
= 1.2Vp-p
= 1.2Vp-p
V
V
= 1.2Vp-p
I_IN/I_IN
I_IN/I_IN
V
= 1.2Vp-p
Q_IN/Q_IN
Q_IN/Q_IN
-36
-38
-40
100mV/
div
-42
-44
R = 10kΩ
L
-42
-44
C < 6pF
L
0
20
40
60
80
45 50 55 60 65 70
IF FREQUENCY (MHz)
35 40
75 80
20ns/div
TEMPERATURE (°C)
0
V
= 1.2Vp-p
= 1.2Vp-p
I_IN/I_IN
-10
-20
-30
V
Q_IN/Q_IN
-40
-50
-60
69.0
69.4
70.0
70.6
71.0
(MHz)
4
_______________________________________________________________________________________
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
MAX2450
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(MAX2450 EV kit, V = LO_V = ENABLE = 3.0V, f = 140MHz, f
= f
Q_IN/Q_IN
= 600kHz, V
= V = 1.2V
,
CC
CC
LO
I_IN/I_IN
I_IN/I_IN
Q_IN/Q_IN
p-p
f
= 70.1MHz, V
= 2.82mV , T = +25°C, unless otherwise noted.)
IF_IN A
p-p
IF_IN
DEMODULATOR VOLTAGE CONVERSION
GAIN vs. TEMPERATURE AND SUPPLY
DEMODULATOR VOLTAGE CONVERSION
GAIN vs. IF FREQUENCY
DEMODULATOR VOLTAGE CONVERSION
GAIN vs. BASEBAND FREQUENCY
51.5
51.4
51.2
51.0
51
50
T = 0°C
A
51.0
50.5
49
48
47
46
45
44
43
42
T = +25°C
A
50.0
49.5
49.0
T = +50°C
A
50.8
50.6
48.5
48.0
T = +70°C
A
2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4
(V)
45 50 55 60 65 70
IF FREQUENCY (MHz)
35 40
75 80
10k
100k
1M
10M
100M
V
CC
BASEBAND FREQUENCY (Hz)
DEMODULATOR I/Q PHASE
AND AMPLITUDE MISMATCH
vs. TEMPERATURE
DEMODULATOR INTERMOD POWER
vs. TEMPERATURE
-40
-45
-50
-55
1.6
IM3
1.4
1.2
PHASE MATCH
f
= 140MHz
= 70.1MHz
= 70.11MHz
OSC
1.0
0.8
0.6
0.4
f
IF1
f
IF2
V
= 2.82mVp-p
IF_IN
-60
-65
IM5
AMPLITUDE MATCH
20
30
40
50
60 70
0
10
20
30
40
50
60 70
0
10
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
______________________________________________________________P in De s c rip t io n
PIN
1
NAME
IF_OUT
IF_OUT
GND
FUNCTION
Modulator IF Output
2
Modulator IF Inverting Output
Ground
3, 19
4
I_IN
Baseband Inphase Input
Baseband Inphase Inverting Input
Baseband Quadrature Input
Baseband Quadrature Inverting Input
Enable Control, active high
MAX2450
5
I_IN
6
Q_IN
7
Q_IN
8
ENABLE
PRE_OUT
9
Local-Oscillator, Divide-by-8, Prescaled Output
Local-Oscillator Supply. Bypass separately from V
10
11
12
13
14
15
16
17
18
20
LO_V
CC
.
CC
TANK
TANK
Local-Oscillator Resonant Tank Input (Figure 4)
Local-Oscillator Resonant Tank Inverting Input (Figure 4)
Local-Oscillator Ground
LO_GND
Q_OUT
Q_OUT
I_OUT
Demodulator Quadrature Inverting Output
Demodulator Quadrature Output
Demodulator Inphase Inverting Output
Demodulator Inphase Output
I_OUT
V
CC
Modulator and Demodulator Supply
Demodulator IF Input
IF_IN
2
2
A/D
CONVERSION
A/D
CONVERSION
DSP
0°
R
90°
T
÷ 8
UP/DOWNCONVERTER
2
2
D/A
Σ
CONVERSION
D/A
CONVERSION
MAX2450
Figure 1. Typical Application Block Diagram
_______________________________________________________________________________________
6
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
MAX2450
LO_V
CC
75
70
R
5k
R
L
5k
L
65
60
55
Q3
Q4
TANK
TANK
50
45
40
35
Q1
Q2
TO
QUADRATURE
GENERATOR AND
PRESCALER
200
1k
10k
100k
LOAD RESISTANCE (Ω)
Figure 2. Local-Oscillator Equivalent Circuit
Figure 3. Modulator Output Level vs. Load Resistance
and should provide 200mVp-p levels. A choke (typically
2.2µH) is required between TANK and TANK. Differ-
ential input impedance at TANK/TANK is 10kΩ. For sin-
g le -e nd e d d rive , c onne c t a n AC b yp a s s c a p a c itor
(1000pF) from TANK to GND, and AC couple TANK to
the source.
_______________De t a ile d De s c rip t io n
The following sections describe each of the functional
blocks shown in the Functional Diagram. They also refer
to the Typical Application Block Diagram (Figure 1).
De m o d u la t o r
The demodulator contains a single-ended-to-differential
converter, two Gilbert-cell multipliers, and two fixed gain
stages. The IF signal should be AC coupled into IF_IN.
Internally, IF_IN is terminated with a 400Ω resistor to
GND and provides a gain of 14dB. This amplified IF sig-
nal is fed into the I and Q mixers for demodulation. The
multipliers mix the IF signal with the quadrature LO sig-
nals, resulting in baseband I and Q signals. The conver-
sion gain of the multipliers is 15dB. These signals are
further amplified by 21dB by the baseband amplifiers.
The baseband I and Q amplifier chains are DC coupled.
Qu a d ra t u re P h a s e Ge n e ra t o r
The quadrature phase generator uses two latches to
divide the local-oscillator frequency by two, and gener-
ates two precise quadrature signals. Internal limiting
amplifiers shape the signals to approximate square
waves to drive the Gilbert-cell mixers. The inphase sig-
nal (at half the local-oscillator frequency) is further
divided by four for the prescaler output.
P re s c a le r
The prescaler output, PRE_OUT, is buffered and swings
typically 0.35V
AC-coupled to the input of a frequency synthesizer.
with a 10kΩ and 6pF load. It can be
p-p
Lo c a l Os c illa t o r
The local-oscillator section is formed by an emitter-cou-
pled differential pair. Figure 2 shows the equivalent
local-oscillator circuit schematic. An external LC reso-
nant tank determines the oscillation frequency, and the
Q of this resonant tank affects the oscillator phase
noise. The oscillation frequency is twice the IF frequen-
cy, so that the quadrature phase generator can use two
latches to generate precise quadrature signals.
Mo d u la t o r
The modulator accepts I and Q differential baseband
signals up to 1.35V with frequencies up to 15MHz,
p-p
and upconverts them to the IF frequency. Since these
inputs are biased internally at around 1.5V, I and Q sig-
nals should be capacitively coupled into these high-
impedance ports (the differential input impedance is
approximately 44kΩ). The self-bias design yields very
low on-chip offset, resulting in excellent carrier sup -
The oscillator may be overdriven by an external source.
The source should be AC coupled into TANK/TANK,
_______________________________________________________________________________________
7
3 V, Ult ra -Lo w -P o w e r Qu a d ra t u re
Mo d u la t o r/De m o d u la t o r
pression. Alternatively, a differential DAC may be con-
nected without AC coupling, as long as a common-
mode voltage range of 1.25V to 1.75V is maintained.
For single-ended drive, connect I_IN and Q_IN via AC-
coupling capacitors (0.1µF) to GND.
To alter the oscillation frequency range, change the
inductance, the capacitance, or both. For best phase-
noise performance keep the Q of the resonant tank as
high as possible:
C
EQ
Q = R
EQ
The IF output is designed to drive a high impedance
(> 20kΩ), s uc h a s a n IF b uffe r or a n up c onve rte r
mixe r. IF_OUT/IF_OUT mus t b e AC c oup le d to the
load. Impedances as low as 200Ω can be driven with a
decrease in output amplitude (Figure 3). To drive a sin-
gle-ended load, AC couple and terminate IF_OUT with
a resistive load equal to the load at IF_OUT.
L
EQ
where R ≈ 10kΩ (Figure 2).
EQ
MAX2450
The oscillation frequency can be changed by altering
the control voltage, V
.
CTRL
Ma s t e r Bia s
During normal operation, ENABLE should remain above
V
CC
- 0.4V. Pulling the ENABLE input low shuts off the
C1 = 33pF
47k
TANK
master bias and reduces the circuit current to less than
2µA. The master bias section includes a bandgap ref-
erence generator and a PTAT (Proportional To Absolute
Temperature) current generator.
1
/
KV1410
2
2
0.1µF
10k
L = 100nH
V
CTRL
__________Ap p lic a t io n s In fo rm a t io n
1
/
KV1410
47k
Figure 4 shows the implementation of a resonant tank
circuit. The inductor, two capacitors, and a dual varac-
tor form the oscillator’s resonant circuit. In Figure 4, the
oscillator frequency ranges from 130MHz to 160MHz.
TANK
C2 = 33pF
To ensure reliable start-up, the inductor is directly con-
nected across the local oscillator’s tank ports. The two
33pF capacitors affect the Q of the resonant circuit.
Other values may be chosen to meet individual appli-
cation requirements. Use the following formula to deter-
mine the oscillation frequency:
Figure 4. Typical Resonant Tank Circuit
1
f
=
o
2π L
C
EQ EQ
where
and
1
1
C
=
+ C
STRAY
EQ
1
2
+
+
C1 C2
C
VAR
L
= L + L
EQ
STRAY
where C
= parasitic capacitance and L
=
STRAY
STRAY
parasitic inductance.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
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