_______________General Description
The monolithic MAX2452 is a quadrature modulator
with supporting oscillator and divide-by-8 prescaler. It
operates from a single +3V supply and draws only
4.1mA. The modulator accepts differential I and Q
baseband signals with amplitudes up to 1.35Vp-p and
bandwidths up to 15MHz. It produces a differential out-
put up to 80MHz.
Pulling the CMOS-compatible ENABLE pin low reduces
the supply current to 2A. To minimize spurious feed-
back, the MAX2452's internal oscillator is set at twice
the IF via external tuning components. The oscillator
and associated phase shifters produce differential sig-
nals exhibiting low amplitude and phase imbalance,
yielding 42dB sideband rejection. The MAX2452 comes
in a 16-pin narrow SO package.
________________________Applications
Digital Cordless Phones
GSM and North American Cellular Phones
Wireless LANs
Digital Communications
Two-Way Pagers
____________________________Features
o
IF Output Frequency up to 80MHz
o
Input Bandwidth up to 15MHz
o
On-Chip Oscillator with External Tuning Circuit
o
On-Chip Divide-by-8 Prescaler
o
Integrated Quadrature Phase Shifters
o
Self-Biased Differential Baseband Inputs
o
CMOS-Compatible Enable
o
4.1mA Operating Supply Current
2A Shutdown Supply Current
MAX2452
3V, Ultra-Low-Power
Quadrature Modulator
________________________________________________________________
Maxim Integrated Products
1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
IF
GND
V
CC
N.C.
PRE_OUT
LO_V
CC
LO_GND
TANK
IF
GND
I
I
Q
Q
ENABLE
TANK
TOP VIEW
MAX2452
SO
MAX2452
MODULATOR
LOCAL
OSCILLATOR
2
2
4
QUADRATURE
PHASE
GENERATOR
90
0
LO_V
CC
TANK
TANK
LO_GND
I
I
Q
Q
V
CC
PRE_OUT
IF
IF
BANDGAP
BIAS
GND
ENABLE
PRESCALER
11
8
9
10
3
4
5
6
14
12
16
1
7
2, 15
MASTER BIAS
__________________Pin Configuration
________________Functional Diagram
Call toll free 1-800-998-8800 for free samples or literature.
PART
MAX2452ISE*
-20C to +85C
TEMP. RANGE
PIN-PACKAGE
16 Narrow SO
EVALUATION KIT
AVAILABLE
______________Ordering Information
19-0425; Rev 1; 9/95
* An alternate marking, MAX2452CSE, has been identically tested.
MAX2452
3V, Ultra-Low-Power
Quadrature Modulator
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(V
CC
= LO_V
CC
= 2.7V to 3.3V, T
A
= -20C to +85C, unless otherwise noted.)
AC ELECTRICAL CHARACTERISTICS
(V
CC
= LO_V
CC
= 3.0V, f
OSC
= 140MHz, ENABLE = 2.6V, f
II
= f
QQ
= 600kHz, T
A
= -20C to +85C, unless otherwise noted.)
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.
Note 1:
Guaranteed by design, not tested.
Note 2:
The frequency range can be extended in either direction, but has not been characterized. At higher frequencies, the IF
output level may decrease and distortions may increase.
V
CC
, LO_V
CC
to GND............................................-0.3V to +4.5V
ENABLE, TANK, TANK, I, I, Q, Q to GND ..................V
CC
+ 0.3V
Continuous Power Dissipation (T
A
= +70C)
SO (derate 8.33mW/C above +70C) ..........................667mW
Operating Temperature Range ...........................-20C to +85C
Storage Temperature Range ............................65C to +165C
Lead Temperature (soldering, 10sec) .............................+300C
Enable = 0.4V
Enable = V
CC
- 0.4V
Enable = V
CC
- 0.4V
CONDITIONS
k
35
44
Z
II
, Z
QQ
Differential Input Impedance
V
1.25
1.5
1.75
V
I
, V
I
, V
Q
, V
Q
I, I, Q, Q Voltage Level
A
2
20
I
CC OFF
Shutdown Supply Current
mA
4.1
7
I
CC ON
V
2.7
3.3
V
CC
, LO_V
CC
Supply Voltage Range
Supply Current
V
LO_V
CC
- 1.1
LO_V
CC
- 0.8
V
TANK
TANK Voltage Level
V
LO_V
CC
- 1.1
LO_V
CC
- 0.8
V
TANK
TANK Voltage Level
V
V
CC
- 1.7
V
CC
- 1.35
V
IF
IF Voltage Level
V
V
CC
- 1.7
V
CC
- 1.35
V
IF
IF Voltage Level
s
10
t
ON/OFF
Enable/Disable Time
A
1
10
I
EN
ENABLE Bias Current
V
0.4
V
ENL
ENABLE Low Voltage
V
V
CC
- 0.4
V
ENH
ENABLE High Voltage
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
R
L
= 10k
, C
L
< 6pF, rising edge,
T
A
= +25C
R
L
= 10k
, C
L
< 6pF
(Notes 1, 2)
V
II
= V
QQ
= 1.2Vp-p
V
II
= V
QQ
= 1.2Vp-p, R
L
= 200k
differential, C
L
< 5pF differential
(Note 1)
(Note 1)
CONDITIONS
V/s
60
SR
PRE_OUT
PRE_OUT Slew Rate
Vp-p
0.35
V
PRE_OUT
PRE_OUT Output Voltage
MHz
70
140
160
f
OSC
Oscillator Frequency Range
dBc
-36
LO Leakage at Output
dB
42
Sideband Rejection
degrees
<3
I/Q Phase Match
dB
<0.3
I/Q Amplitude Match
mVp-p
65
V
IFIFp-p
IF Differential Output Voltage
MHz
15
BW
IQ
I and Q Signal Bandwidth
Vp-p
1.2
1.35
V
IIp-p
, V
QQp-p
Differential Input Voltage
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
MAX2452
3V, Ultra-Low-Power
Quadrature Modulator
_______________________________________________________________________________________
3
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
-30
-10
10
30
50
70
90
MAX2452-01
TEMPERATURE (C)
SUPPLY CURRENT (mA)
SUPPLY CURRENT
vs. TEMPERATURE
V
CC
= 2.7V
V
CC
= 3.3V
V
CC
= 3V
0
2
4
6
8
10
12
14
16
-30
-10
10
30
50
70
90
MAX2452-02
TEMPERATURE (C)
V
CC
= 2.7V
V
CC
= 3.3V
V
CC
= 3V
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
SUPPLY CURRENT (
A)
-30
-34
-38
-42
-46
-50
-54
-26
-22
-18
-14
-10
-6
MAX2452-03
BASEBAND INPUT (dBV
RMS
)
OUTPUT (dBV
RMS
)
IF OUTPUT
vs. BASEBAND INPUT
Vp-p = 2 2 x 10
(V)
dBV
RMS
20
54
56
58
60
62
64
66
68
70
72
74
2.7
MAX2452-04
V
CC
(V)
IF OUTPUT (mVp-p)
2.8
2.9
3.0
3.1
3.2
3.3
T
A
= +85C
T
A
= +70C
T
A
= +25C
T
A
= 0C
T
A
= -25C
IF OUTPUT
vs. SUPPLY VOLTAGE
-50
-48
-46
-44
-42
-40
-38
-36
-34
-32
-30
-30
-10
10
30
50
70
90
MAX2452-07
TEMPERATURE (C)
SIDEBAND REJECTION (dBc)
V
II
= 1.2Vp-p
V
QQ
= 1.2Vp-p
SIDEBAND REJECTION
vs. TEMPERATURE
70
68
66
64
62
60
-30
-10
10
30
50
70
90
MAX2452-05
TEMPERATURE (C)
IF OUTPUT (mVp-p)
V
CC
= 3V
IF OUTPUT
vs. TEMPERATURE
-50
-48
-46
-44
-42
-40
-38
-36
-34
-32
-30
35
40
45
50
55 60
65
70 75
80
MAX2452-06
IF FREQUENCY (MHz)
SIDEBAND REJECTION (dBc)
V
II
= 1.2Vp-p
V
QQ
= 1.2Vp-p
SIDEBAND REJECTION
vs. IF FREQUENCY
-30
-32
-34
-36
-38
-40
-42
-44
80
35
40
45
50
55
60
65
70
75
MAX2452-08
IF FREQUENCY (MHz)
LO LEAKAGE (dBc)
LO LEAKAGE
vs. IF FREQUENCY
__________________________________________Typical Operating Characteristics
(V
CC
= LO_V
CC
= 3.0V, f
OSC
= 140MHz, ENABLE = 2.6V, f
II
= f
QQ
= 600kHz, R
L
(IF, IF) = 200k
differential, C
L
(IF, IF) < 5pF
differential, T
A
= +25C, unless otherwise noted.)
100mV/
div
PRE_OUT WAVEFORM
MAX2452-09
20ns/div
R
L
= 10k
C
L
< 6pF
MAX2452
3V, Ultra-Low-Power
Quadrature Modulator
4
_______________________________________________________________________________________
-60
69.0
70.6
71.0
MODULATOR OUTPUT SPECTRUM
-50
0
MAX2453-10
(MHz)
(dBc)
69.4
70.0
-20
-10
-30
-40
V
II
= 1.2Vp-p
V
QQ
= 1.2Vp-p
____________________________Typical Operating Characteristics (continued)
(V
CC
= LO_V
CC
= 3.0V, f
OSC
= 140MHz, ENABLE = 2.6V, f
II
= f
QQ
= 600kHz, R
L
(IF, IF) = 200k
differential, C
L
(IF, IF) < 5pF
differential, T
A
= +25C, unless otherwise noted.)
NAME
FUNCTION
1
IF
IF Inverting Output
2, 15
GND
Ground
PIN
3
I
Inphase Input
4
I
Inphase Inverting Input
8
TANK
Local-Oscillator Resonant Tank
Input
7
ENABLE
Enable Control, active high
6
Q
Quadrature Inverting Input
5
Q
Quadrature Input
13
N.C.
No Connect, no internal connection
to this pin
12
PRE_OUT
Local-Oscillator Divide-by-8
Prescaled Output
11
LO_V
CC
Local-Oscillator Supply
10
LO_GND
Local-Oscillator Ground
9
TANK
Local-Oscillator Resonant Tank
Inverting Input
_____________________Pin Description
16
IF
IF Output
14
V
CC
Modulator Supply
MAX2452
3V, Ultra-Low-Power
Quadrature Modulator
_______________________________________________________________________________________
5
_______________Detailed Description
The MAX2452 quadrature modulator integrates several
important RF functions on a single chip. It includes dif-
ferential buffers for the baseband inputs, two double-
balanced mixers, a local oscillator, a quadrature phase
generator, and a divide-by-8 prescaler. The prescaler
simplifies the implementation of a phase-locked loop.
Each of the functional blocks (shown in the
Functional
Diagram) is described in detail in the following sec-
tions.
Local Oscillator
The local-oscillator section is formed by an emitter-cou-
pled differential pair. Figure 1 shows the equivalent
local-oscillator circuit schematic. An external LC reso-
nant tank determines the oscillation frequency, and the
Q of this resonant tank determines the phase noise of
the oscillator. The oscillation frequency is twice the IF
frequency, so that the quadrature phase generator can
use two latches to generate precise quadrature signals.
Quadrature Phase Generator
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 in the modulator.
The inphase signal (at half the local-oscillator frequen-
cy) is further divided by four for an external phase-
locked loop.
Modulator
The modulator accepts up to 1.35Vp-p I and Q differen-
tial baseband signals up to 15MHz, and upconverts
them to higher-frequency IF signals. Since these inputs
are biased internally at around 1.5V, you can improve
carrier suppression by externally capacitively coupling
the signals into these high-impedance ports (the differ-
ential input impedance is approximately 44k
). The
self-bias design is for very low on-chip offset, resulting
in excellent carrier suppression. The IF output is
designed to drive a high impedance (>20k
), such as
an IF buffer or an upconverter mixer.
Prescaler
The prescaler output, PRE_OUT, is buffered and
swings typically 0.35Vp-p with a 10k
and 6pF load. It
can be AC-coupled to the input of a frequency synthe-
sizer.
Master Bias
During normal operation, ENABLE should remain above
V
CC
- 0.4V. Pulling the ENABLE input low shuts off the
master bias and reduces the circuit current to 2A. The
master bias section includes a bandgap reference
generator and a PTAT (Proportional To Absolute
Temperature) current generator.
TANK
TANK
Q1
Q2
Q3
Q4
R
L
5k
R
L
5k
L0_V
CC
TO
DIVIDE-BY-2
Figure 1. Local-Oscillator Equivalent Circuit
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