MAX2451 [MAXIM]
3V, Ultra-Low-Power Quadrature Demodulator; 3V ，超低功耗正交解调器
| 型号： | MAX2451 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 3V, Ultra-Low-Power Quadrature Demodulator |
| 文件： | 总6页 (文件大小：60K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0493; Rev 0; 12/95
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re De m o d u la t o r
MAX2451
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The monolithic MAX2451 is a quadrature demodulator
with a supporting oscillator and divide-by-8 prescaler. It
operates from a single +3V supply and draws only
5.5mA. The demodulator accepts an amplified and fil-
tered IF signal in the 35MHz to 80MHz range, and
demodulates it into I and Q baseband signals with
51dB of voltage conversion gain. The IF input is termi-
nated with a 400Ω thin-film resistor for matching to an
external IF filter. The baseband outputs are fully differ-
ential and have 1.2Vp-p signal swings.
♦ Integrated Quadrature Phase Shifters
♦ On-Chip Oscillator (Requires External Tuning
Circuit)
♦ 51dB Voltage Conversion Gain
♦ On-Chip Divide-by-8 Prescaler
♦ Baseband Output Bandwidth Up to 9MHz
♦ CMOS-Compatible Enable
Pulling the CMOS-compatible ENABLE pin low shuts
down the MAX2451 and reduces the supply current to
less than 2µA, typical. To minimize spurious feedback,
the MAX2451’s internal oscillator is set at twice the IF
fre q ue nc y via e xte rna l tuning c omp one nts . The
MAX2451 comes in a 16-pin narrow SO package.
♦ 5.5mA Operating Supply Current
2µA Shutdown Supply Current
______________Ord e rin g In fo rm a t io n
________________________Ap p lic a t io n s
Digital Cordless Phones
PART
TEMP. RANGE
PIN-PACKAGE
MAX2451CSE
0°C to +70°C
16 Narrow SO
GSM and North American Cellular Phones
Wireless LANs
Digital Communications
Pagers
________________Fu n c t io n a l Dia g ra m
14
I
13
__________________P in Co n fig u ra t io n
I
DEMODULATOR
1
IF
BIAS
12
11
TOP VIEW
Q
Q
400Ω
IF
GND
1
2
3
4
5
6
7
8
GND
16
15
14
13
12
0°
6
7
8
V
CC
÷ 2
÷ 4
LO_V
PRE_OUT
CC
PRESCALER
TANK
QUADRATURE
PHASE
GENERATOR
GND
I
9
TANK
N.C.
MAX2451
I
10
90°
÷ 2
LOCAL
LO_GND
MAX2451
ENABLE
PRE_OUT
Q
OSCILLATOR
15
11
10
9
Q
V
CC
MASTER BIAS
LO_V
CC
LO_GND
TANK
BANDGAP
BIAS
TANK
2, 3, 16
GND
5
SO
ENABLE
________________________________________________________________ Maxim Integrated Products
1
Call toll free 1-800-998-8800, or visit our WWW site at http://www.maxim-ic.com
for free samples or the latest literature.
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re 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, I,
Q, Q to GND.............................................-0.3V to (V + 0.3V)
IF to GND...............................................................-0.3V to +1.5V
Narrow SO (derate 8.70mW/°C above +70°C) .............696mW
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.
MAX2451
DC ELECTRICAL CHARACTERISTICS
(V
= LO_V
= TANK = +2.7V to +3.3V, ENABLE = V
- 0.4V, GND = LO_GND = 0V, I = I = Q = Q = IF = TANK = OPEN,
CC
CC
CC
T
A
= 0°C to +70°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
LO_V
,
CC
Supply Voltage Range
2.7
3.3
V
CC
Supply Current
I
5.5
2
7.4
20
mA
µA
µs
µA
V
CC(ON)
Shutdown Supply Current
Enable/Disable Time
ENABLE Bias Current
ENABLE High Voltage
ENABLE Low Voltage
IF Input Impedance
I
Enable = 0.4V
CC(OFF)
t
10
1
ON/OFF
I
EN
3
V
ENH
V
- 0.4
CC
V
ENL
0.4
V
Z
320
400
1.2
480
Ω
IN
V ,
I/I
I, I, Q, Q Voltage Level
V
V
Q/Q
Baseband I and Q DC Offset
±11
±50
mV
AC ELECTRICAL CHARACTERISTICS
V
CC
= LO_V = ENABLE = 3.0V, f = 140MHz, f = 70.1MHz, V = 2.82mVp-p, T = +25°C, unless otherwise noted.)
CC LO IF IF A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Baseband I and Q Amplitude
Balance
< ±0.45
dB
Baseband I and Q Phase Accuracy
Voltage Conversion Gain
Noise Figure
< ±1.3
51
degrees
dB
NF
18
dB
Allowable I and Q Voltage Swing
I and Q IM3 Level
(Note 1)
(Note 2)
(Note 2)
1.35
160
Vp-p
dBc
IM3
-44
-60
9
I/Q
I/Q
I and Q IM5 Level
IM5
dBc
I and Q Signal 3dB Bandwidth
Oscillator Frequency Range
PRE_OUT Output Voltage
PRE_OUT Slew Rate
BW
MHz
MHz
Vp-p
V/µs
3dB
f
(Notes 1, 3)
70
LO
PRE_OUT
V
R
R
= 10kΩ, C < 6pF
0.35
60
L
L
L
SR
= 10kΩ, C < 6pF, rising edge
L
PRE_OUT
Oscillator Phase Noise
Offset = 10kHz
-80
dBc/Hz
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
IF
Note 3: Oscillator frequencies up to 1GHz (500MHz IF) by externally overdriving (see Applications Information).
2
_______________________________________________________________________________________
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re De m o d u la t o r
MAX2451
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = LO_V = ENABLE = 3.0V, f = 140MHz, f = 70.1MHz, V = 2.82mVp-p, T = +25°C, unless otherwise noted.)
CC
CC
LO
IF
IF
A
SUPPLY CURRENT
vs. TEMPERATURE
VOLTAGE CONVERSION GAIN vs.
TEMPERATURE AND SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
6.4
7
6
5
4
3
2
1
0
51.5
51.0
50.5
V
= 3.0V
CC
V = 3.0V
CC
T
A
= 0°C
6.2
6.0
T
A
= +25°C
50.0
49.5
49.0
5.8
5.6
5.4
5.2
T
A
= +50°C
48.5
48.0
T
A
= +70°C
0
10
20
30
40 50
60
70
0
10
20
30
40 50
60
70
2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4
(V)
TEMPERATURE (°C)
TEMPERATURE (°C)
V
CC
VOLTAGE CONVERSION
GAIN vs. IF FREQUENCY
INTERMODULATION POWER
vs. TEMPERATURE
PHASE AND AMPLITUDE
MATCHING vs. TEMPERATURE
52
51
50
49
48
47
46
45
44
43
42
-40
-45
-50
-55
1.6
IM3
1.4
1.2
PHASE MATCH
f
= 140MHz
= 70.10MHz
= 70.11MHz
LO
1.0
0.8
0.6
0.4
f
IF1
f
IF2
V
= 1.41mVp-p per tone
IF_IN
f
= 100kHz
BASEBAND
V
= 40mV = 113mVp-p
LO_INJECT
into 5OΩ
RMS
-60
-65
IM5
AMPLITUDE MATCH
V
= 2.82mV
IF_IN
P-P
0
100
200
300
400
500
20
30
40
50
60 70
0
10
20
30
40
50
60 70
0
10
IF FREQUENCY (MHz)
TEMPERATURE (°C)
TEMPERATURE (°C)
PRE_OUT WAVEFORM
100mV/div
R
L
= 10kΩ
C
L
< 6pF
20ns/div
_______________________________________________________________________________________
3
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re De m o d u la t o r
_____________________P in De s c rip t io n
PIN
NAME
FUNCTION
1
IF
IF Input
Ground
2, 3, 16
GND
No Connect. No internal connec-
tion to this pin.
4
5
6
N.C.
ENABLE
PRE_OUT
Enable Control, active high
MAX2451
Local-Oscillator Divide-by-8
Prescaled Output
DOWNCONVERTER
Local-Oscillator Supply. Bypass
7
8
LO_V
CC
separately from V
.
CC
Local-Oscillator Resonant Tank
Input
TANK
Local-Oscillator Resonant Tank
Inverting Input
9
TANK
2
A/D
POST
PROCESSING
0˚
90˚
10
11
12
13
LO_GND
Local-Oscillator Ground
Baseband Quadrature Inverting
Output
Q
Q
I
2
A/D
Baseband Quadrature Output
MAX2451
Baseband Inphase Inverting
Output
÷8
14
15
I
Baseband Inphase Output
Demodulator Supply
V
CC
Figure 1. Typical Application Block Diagram
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 local-oscillator
equivalent circuit schematic. An external LC resonant
tank determines the oscillation frequency, and the Q of
this resonant tank affects the oscillator phase noise.
The oscillation frequency is twice the IF frequency, for
easy generation of quadrature signals.
_______________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. 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. Internally, IF is terminated with a 400Ω
resistor to GND. The IF input signal is AC coupled into
the input amplifier, which has 14dB of gain. This ampli-
fied IF signal is fed into the I and Q channel mixers for
demodulation. The multipliers mix the IF signal with the
quadrature LO signals, resulting in baseband I and Q
signals. The conversion gain of the multipliers is 15dB.
These signals are further amplified by 21dB by the
baseband amplifiers. The baseband amplifier chains
are DC coupled.
The oscillator may be overdriven by an external source.
The source should be AC coupled into TANK/TANK, and
should provide 200mVp-p levels. A choke (typically
2.2µH) is required between TANK and TANK. Differential
input impedance at TANK/TANK is 10kΩ. For single-
ended drive, connect an AC bypass capacitor (1000pF)
from TANK to GND, and AC couple TANK to the source.
The oscillator can be overdriven at frequencies up to
1GHz (500MHz IF), but conversion gain and prescaler
output levels will be somewhat reduced.
4
_______________________________________________________________________________________
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re De m o d u la t o r
MAX2451
LO_V
CC
R
5k
R
L
5k
L
C1 = 33pF
47k
TANK
Q3
Q4
TANK
TANK
1
/
KV1410
2
2
0.1µF
10k
L = 100nH
V
CTRL
Q1
Q2
1
/
KV1410
47k
TO QUADRATURE
GENERATOR AND
PRESCALER
TANK
C2 = 33pF
Figure 2. Local-Oscillator Equivalent Circuit
Figure 3. Typical Resonant Tank Circuit
cation requirements. The oscillation frequency can be
determined using the following formula:
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.
1
f
=
o
2π L
C
EQ EQ
where
and
1
1
C
=
+ C
STRAY
P re s c a le r
The prescaler output, PRE_OUT, is buffered and swings
typically 0.35Vp-p with a 10kΩ and 6pF load. It can be
AC coupled to the input of a frequency synthesizer.
EQ
1
2
+
+
C1 C2
C
VAR
L
= L + L
EQ
STRAY
Ma s t e r Bia s
During normal operation, ENABLE should be above
where C
parasitic inductance.
= parasitic capacitance and L
=
STRAY
STRAY
V
CC
- 0.4V. Pulling the ENABLE input low shuts off the
master bias and reduces the circuit current to typically
2µA. The master bias section includes a bandgap ref-
erence generator and a PTAT (Proportional To Absolute
Temperature) current generator.
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:
__________Ap p lic a t io n s In fo rm a t io n
Figure 3 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 3, the
oscillator frequency ranges from 130MHz to 160MHz.
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-
C
EQ
Q = R
EQ
L
EQ
where REQ ≈ 10kΩ (Figure 2).
The oscillation frequency can be changed by altering
the control voltage, V
.
CTRL
_______________________________________________________________________________________
5
3 V, Ult ra -Lo w -P o w e r
Qu a d ra t u re De m o d u la t o r
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.053
MAX
0.069
0.010
0.019
0.010
0.157
MIN
1.35
0.10
0.35
0.19
3.80
MAX
1.75
0.25
0.49
0.25
4.00
A
D
A1 0.004
B
C
E
e
0.014
0.007
0.150
0°-8°
A
MAX2451
0.101mm
0.004in.
0.050
1.27
e
H
L
0.228
0.016
0.244
0.050
5.80
0.40
6.20
1.27
A1
C
B
L
INCHES
MILLIMETERS
DIM PINS
Narrow SO
SMALL-OUTLINE
PACKAGE
MIN MAX
MIN
MAX
5.00
8.75
8
0.189 0.197 4.80
D
D
D
E
H
14 0.337 0.344 8.55
16 0.386 0.394 9.80 10.00
21-0041A
(0.150 in.)
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.
6
___________________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
© 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
相关型号：
©2020 ICPDF网 联系我们和版权申明