Maxim MAX2451CSE 3v, ultra-low-power quadrature demodulator Datasheet

19-0493; Rev 0; 12/95
IT
K
ATION
EVALU
BLE
AVAILA
3V, Ultra-Low-Power
Quadrature Demodulator
________________________Applications
Digital Cordless Phones
____________________________Features
♦ 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
♦ 5.5mA Operating Supply Current
2µA Shutdown Supply Current
______________Ordering Information
PART
GSM and North American Cellular Phones
TEMP. RANGE
MAX2451CSE
0°C to +70°C
PIN-PACKAGE
16 Narrow SO
Wireless LANs
Digital Communications
Pagers
________________Functional Diagram
14
13
__________________Pin Configuration
DEMODULATOR
IF
1
400Ω
11
IF 1
16 GND
GND 2
15 VCC
GND 3
N.C. 4
MAX2451
LO_VCC
14 I
TANK
13 I
TANK
ENABLE 5
12 Q
LO_GND
PRE_OUT 6
11 Q
VCC
LO_VCC 7
10 LO_GND
9
TANK 8
SO
7
÷2
8
9
10
I
BIAS
12
TOP VIEW
I
LOCAL
OSCILLATOR
0°
PRESCALER
QUADRATURE
PHASE
GENERATOR
÷ 2 90°
÷4
6
Q
Q
PRE_OUT
MAX2451
15
MASTER BIAS
BANDGAP
BIAS
TANK
2, 3, 16
GND
5
ENABLE
________________________________________________________________ Maxim Integrated Products
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1
MAX2451
_______________General Description
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 filtered 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 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.
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
frequency via external tuning components. The
MAX2451 comes in a 16-pin narrow SO package.
MAX2451
3V, Ultra-Low-Power
Quadrature Demodulator
ABSOLUTE MAXIMUM RATINGS
Continuous Power Dissipation (TA = +70°C)
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
VCC, LO_VCC to GND............................................-0.3V to +4.5V
ENABLE, TANK, TANK, I, I,
Q, Q to GND.............................................-0.3V to (VCC + 0.3V)
IF to GND...............................................................-0.3V to +1.5V
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.
DC ELECTRICAL CHARACTERISTICS
(VCC = LO_VCC = TANK = +2.7V to +3.3V, ENABLE = VCC - 0.4V, GND = LO_GND = 0V, I = I = Q = Q = IF = TANK = OPEN,
TA = 0°C to +70°C, unless otherwise noted.)
PARAMETER
SYMBOL
Supply Voltage Range
VCC,
LO_VCC
CONDITIONS
MIN
TYP
MAX
UNITS
3.3
V
5.5
7.4
mA
2
20
µA
3
µA
2.7
Supply Current
ICC(ON)
Shutdown Supply Current
ICC(OFF)
Enable/Disable Time
tON/OFF
10
ENABLE Bias Current
IEN
1
ENABLE High Voltage
VENH
ENABLE Low Voltage
VENL
IF Input Impedance
I, I, Q, Q Voltage Level
Enable = 0.4V
µs
VCC - 0.4
ZIN
320
VI/I,
VQ/Q
V
400
0.4
V
480
Ω
1.2
Baseband I and Q DC Offset
±11
V
±50
mV
AC ELECTRICAL CHARACTERISTICS
VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fIF = 70.1MHz, VIF = 2.82mVp-p, TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Baseband I and Q Amplitude
Balance
< ±0.45
dB
Baseband I and Q Phase Accuracy
< ±1.3
degrees
51
dB
Voltage Conversion Gain
Noise Figure
NF
Allowable I and Q Voltage Swing
18
(Note 1)
dB
1.35
Vp-p
I and Q IM3 Level
IM3I/Q
(Note 2)
-44
I and Q IM5 Level
IM5I/Q
(Note 2)
-60
dBc
I and Q Signal 3dB Bandwidth
BW3dB
9
MHz
Oscillator Frequency Range
PRE_OUT Output Voltage
PRE_OUT Slew Rate
Oscillator Phase Noise
Note 1:
Note 2:
Note 3:
2
fLO
VPRE_OUT
SRPRE_OUT
(Notes 1, 3)
RL = 10kΩ, CL < 6pF
70
dBc
160
0.35
MHz
Vp-p
RL = 10kΩ, CL < 6pF, rising edge
60
V/µs
Offset = 10kHz
-80
dBc/Hz
Guaranteed by design, not tested.
fIF = 2 tones at 70.10MHz and 70.11MHz, VIF = 1.41mVp-p per tone.
Oscillator frequencies up to 1GHz (500MHz IF) by externally overdriving (see Applications Information).
_______________________________________________________________________________________
3V, Ultra-Low-Power
Quadrature Demodulator
6.0
5.8
5.6
5.4
51.5
MAX2451-02
6
SHUTDOWN ICC (µA)
6.2
VCC = 3.0V
TA = 0°C
51.0
5
TA = +25°C
50.5
GAIN (dBV)
VCC = 3.0V
4
3
50.0
49.5
TA = +50°C
2
49.0
1
48.5
TA = +70°C
0
10
20
30
40
50
60
70
30
40
50
60
VOLTAGE CONVERSION
GAIN vs. IF FREQUENCY
PHASE AND AMPLITUDE
MATCHING vs. TEMPERATURE
49
48
47
46
fBASEBAND = 100kHz
VLO_INJECT = 40mVRMS = 113mVp-p
into 5OΩ
VIF_IN = 2.82mVP-P
42
70
2.6
1.6
PHASE MATCH
1.0
0.8
200
300
400
500
3.2
3.3
3.4
-40
IM3
-45
-50
fLO = 140MHz
fIF1 = 70.10MHz
fIF2 = 70.11MHz
VIF_IN = 1.41mVp-p per tone
-55
IM5
AMPLITUDE MATCH
-65
0
20
10
IF FREQUENCY (MHz)
30
40
50
60
0
70
10
20
30
40
50
60
70
TEMPERATURE (°C)
TEMPERATURE (°C)
PRE_OUT WAVEFORM
MAX2451-07
100
2.9 3.0 3.1
-60
0.6
0.4
0
2.8
INTERMODULATION POWER
vs. TEMPERATURE
1.4
1.2
2.7
VCC (V)
MAX2451-05
MAX2451-04
50
43
20
TEMPERATURE (°C)
51
44
10
TEMPERATURE (°C)
52
45
48.0
0
MATCHING (DEGREES OR dBV)
0
MAX2451-06
5.2
INTERMODULATION (dBc)
ICC (mA)
7
MAX2451-01
6.4
GAIN (dBV)
VOLTAGE CONVERSION GAIN vs.
TEMPERATURE AND SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX2451-03
SUPPLY CURRENT
vs. TEMPERATURE
100mV/div
RL = 10kΩ
CL < 6pF
20ns/div
_______________________________________________________________________________________
3
MAX2451
__________________________________________Typical Operating Characteristics
(VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fIF = 70.1MHz, VIF = 2.82mVp-p, TA = +25°C, unless otherwise noted.)
MAX2451
3V, Ultra-Low-Power
Quadrature Demodulator
_____________________Pin Description
PIN
NAME
1
IF
IF Input
FUNCTION
2, 3, 16
GND
Ground
4
N.C.
No Connect. No internal connection to this pin.
5
ENABLE
Enable Control, active high
6
PRE_OUT
Local-Oscillator Divide-by-8
Prescaled Output
7
LO_VCC
Local-Oscillator Supply. Bypass
separately from VCC.
8
TANK
Local-Oscillator Resonant Tank
Input
9
TANK
Local-Oscillator Resonant Tank
Inverting Input
10
LO_GND
11
Q
Baseband Quadrature Inverting
Output
12
Q
Baseband Quadrature Output
13
I
Baseband Inphase Inverting
Output
14
I
Baseband Inphase Output
15
VCC
DOWNCONVERTER
2
A/D
0˚
90˚
Local-Oscillator Ground
2
POST
PROCESSING
A/D
MAX2451
÷8
Demodulator Supply
Figure 1. Typical Application Block Diagram
_______________Detailed Description
The following sections describe each of the functional
blocks shown in the Functional Diagram. Also refer to
the Typical Application Block Diagram (Figure 1).
Demodulator
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 amplified 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.
4
Local Oscillator
The local-oscillator section is formed by an emitter-coupled 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.
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 singleended 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.
_______________________________________________________________________________________
3V, Ultra-Low-Power
Quadrature Demodulator
MAX2451
LO_VCC
RL
5k
RL
5k
Q3
TANK
C1 = 33pF
TANK
47k
Q4
TANK
1/2 KV1410
10k
L = 100nH
Q1
0.1µF
VCTRL
Q2
1/2 KV1410
TO QUADRATURE
GENERATOR AND
PRESCALER
47k
TANK
Figure 2. Local-Oscillator Equivalent Circuit
C2 = 33pF
Figure 3. Typical Resonant Tank Circuit
Quadrature Phase Generator
The quadrature phase generator uses two latches to
divide the local-oscillator frequency by two, and generates two precise quadrature signals. Internal limiting
amplifiers shape the signals to approximate square
waves to drive the Gilbert-cell mixers. The inphase signal (at half the local oscillator frequency) is further
divided by four for the prescaler output.
cation requirements. The oscillation frequency can be
determined using the following formula:
fo =
Master Bias
During normal operation, ENABLE should be above
VCC - 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 reference generator and a PTAT (Proportional To Absolute
Temperature) current generator.
__________Applications Information
Figure 3 shows the implementation of a resonant tank
circuit. The inductor, two capacitors, and a dual varactor 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 connected 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-
2π LEQCEQ
where
CEQ =
Prescaler
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.
1
1
+ C STRAY
1
1
2
+
+
C1 C2 C VAR
and
LEQ = L + LSTRAY
where CSTRAY = parasitic capacitance and LSTRAY =
parasitic inductance.
To alter the oscillation frequency range, change the
inductance, the capacitance, or both. For best phasenoise performance, keep the Q of the resonant tank as
high as possible:
Q = REQ C EQ
LEQ
where REQ ≈ 10kΩ (Figure 2).
The oscillation frequency can be changed by altering
the control voltage, VCTRL.
_______________________________________________________________________________________
5
MAX2451
3V, Ultra-Low-Power
Quadrature Demodulator
________________________________________________________Package Information
DIM
D
0°-8°
A
0.101mm
0.004in.
e
B
A1
E
C
L
Narrow SO
SMALL-OUTLINE
PACKAGE
(0.150 in.)
H
A
A1
B
C
E
e
H
L
INCHES
MAX
MIN
0.069
0.053
0.010
0.004
0.019
0.014
0.010
0.007
0.157
0.150
0.050
0.244
0.228
0.050
0.016
DIM PINS
D
D
D
8
14
16
MILLIMETERS
MIN
MAX
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
3.80
4.00
1.27
5.80
6.20
0.40
1.27
INCHES
MILLIMETERS
MIN MAX
MIN
MAX
0.189 0.197 4.80
5.00
0.337 0.344 8.55
8.75
0.386 0.394 9.80 10.00
21-0041A
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 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1995 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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