1055.PDF

(65 KB) Pobierz
19-0392; Rev 1; 5/96
NUAL
KIT MA
UATION TA SHEET
EVAL
WS DA
FOLLO
800MHz to 1000MHz Transmitter
_______________General Description
The MAX2402 transmitter integrates a double-balanced
mixer, buffered local oscillator (LO) port, variable gain
stage, and power amplifier into a single IC. It is intend-
ed for use in the 800MHz to 1000MHz band, and is
compatible with both direct-sequence and frequency-
hopping spread-spectrum designs in the 902MHz to
928MHz ISM band.
In a typical application, a digital baseband signal is
mixed with a local oscillator signal to yield a BPSK-
modulated carrier at the antenna. Alternatively, the
baseband input may be grounded and an FSK-
modulated LO signal applied directly to the LO port.
The LO port consists of a limiting amplifier that can
accept a single-ended or differential signal with input
power between -6dBm and +6dBm in the 800MHz to
1000MHz frequency range. The baseband modulation
input is linear over a 2V range, and limits with larger
signal levels within the supply range. The double-
balanced mixer has been optimized for high carrier
rejection. The variable gain stage offers typically 40dB
of adjustment range. The power amplifier provides
more than 20dBm output power and has a bias adjust-
ment, which allows adjustment of efficiency and
harmonic distortion.
A shutdown function reduces the current draw to less
than 2µA in less than 10µs. The MAX2402 comes in a
20-pin SSOP package to minimize board area.
____________________________Features
o
Low-Cost, Flexible Transmitter
o
More than 100mW of Output Power into 50Ω
o
Operates from 800MHz to 1000MHz
o
Single +5V Supply
o
20-Pin SSOP Package
o
Uses Less than 2µA in Power-Down
o
More than 35dB of Power Adjustment Range
o
LO Input Power Range from -6dBm to +6dBm
o
2V Linear Range on Modulation Input
MAX2402
______________Ordering Information
PART
MAX2402EAP*
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
20 SSOP
* An alternate marking, MAX2402CAP, has been identically tested.
________________________Applications
Direct-Sequence Spread-Spectrum Transmitter
Frequency-Hopping Spread-Spectrum
Transmitter
FSK, GMSK, BPSK, and ASK Digital Transmitter
AM and FM Analog Transmitter
__________________Pin Configuration
TOP VIEW
VGC
MOD
GND
V
CC
1
2
3
4
5
6
7
8
9
20 GND
19 V
CC
18 GND
17 GND
________________Functional Diagram
VGC
MODULATION
BUFFER
MOD
MIXER
VGC
POWER
AMPLIFIER
OUT
GND
LO+
LO-
GND
MAX2402
16 OUT
15 GND
14 OUT
13 GND
12 V
CC
11 LGND
LO INPUT
BUFFER
LO+
LO-
SHDN
MASTER BIAS
SHDN
BADJ
BADJ 10
SSOP
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
800MHz to 1000MHz Transmitter
MAX2402
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.3V to +6.5V
Continuous Power Dissipation (T
A
= +70°C)
SSOP (derate 16.7mW/°C above +70°C) ......................1.33W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
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
(V
CC
= 4.75V to 5.5V, BADJ = open, SHDN = V
CC
- 0.5V, VGC = V
CC
, MOD = open, T
A
= -40°C to +85°C, unless otherwise noted.)
PARAMETER
Supply Current
Shutdown Supply Current
Supply Voltage Range
VGC Input Bias Current
MOD Bias Current
SHDN Bias Current
SHDN Low Threshold
SHDN High Threshold
SYMBOL
I
CC
I
CCPD
V
CC
I
VGC
I
MOD
I
PD
V
SHDN
Low
V
SHDN
High
V
CC
- 0.5
VGC = V
CC
MOD = V
CC
MOD = 0V
SHDN = V
CC
-320
10.5
0.5
SHDN = 0.5V
4.75
CONDITIONS
Not transmitting
MIN
TYP
105
0.15
2
5.50
115
325
MAX
UNITS
mA
µA
V
µA
µA
µA
V
V
AC ELECTRICAL CHARACTERISTICS
(MAX2402 evaluation kit, V
CC
= 5.0V, BADJ = 2V, SHDN = V
CC
, MOD = 0V, VGC = V
CC
, R
LOAD
= 35Ω, f
LO
= 900MHz,
LO power = -3dBm, T
A
= -40°C to +85°C, unless otherwise noted.)
PARAMETER
Supply Current
Maximum Output Power
Minimum Output Power
Power Gain from LO
LO Input Power Range
LO Frequency Range
MOD Usable Bandwidth
VGC Control Range
Carrier Suppression
2nd Harmonic Suppression
3rd Harmonic Suppression
Output IP3 (BADJ = 1.0V)
SYMBOL
I
CCAC
P
MAX
P
MIN
P
GAIN
P
LO
f
LO
MODBW
VGC
CS
HS2
HS3
IP3
For max power out (50Ω input term)
(Note 2)
(Note 2)
(Note 2)
(Note 2)
MOD = 5Vp-p @ 100kHz
(Note 1)
(Note 1)
f
LO
= 900MHz + 901MHz
1.0
30
22
25
28.4
-6
800
(Note 1)
VGC = 0V (Note 1)
CONDITIONS
P
OUT
= 20dBm (including current to load)
MIN
TYP
165
21
-19
24
6
1000
25
2.5
MAX
UNITS
mA
dBm
dBm
dB
dBm
MHz
MHz
V
dBC
dBC
dBC
dBm
Note 1:
See
Typical Operating Characteristics
graphs.
Note 2:
Guaranteed by design.
2
_______________________________________________________________________________________
800MHz to 1000MHz Transmitter
__________________________________________Typical Operating Characteristics
(MAX2402 evaluation kit, V
CC
= 5.0V, BADJ = 2V, SHDN = V
CC
, MOD = 0V, VGC = V
CC
, R
LOAD
= 35Ω, f
LO
= 900MHz,
LO power = -3dBm)
OUTPUT POWER vs.
GAIN CONTROL VOLTAGE
MAX2402 TOC 1
MAX2402
OUTPUT POWER vs. FREQUENCY
vs. TEMPERATURE
MAX2402 TOC 2
OUTPUT POWER vs.
TEMPERATURE
MAX2402 TOC 3
25
20
OUTPUT POWER (dBm)
15
10
5
0
-5
-10
-15
-20
-25
1.0
1.5
VGC (V)
2.0
25
-40°C
+24°C
OUTPUT POWER (dBm)
23
+85°C
21
22.0
OUTPUT POWER (dBm)
21.5
21.0
19
17
20.5
900MHz INPUT
15
2.5
800 820 840 860 880 900 920 940 960 980
FREQUENCY (MHz)
20.0
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
OUTPUT POWER vs. BIAS CONTROL VOLTAGE
vs. FREQUENCY
MAX2402 TOC 4
SUPPLY CURRENT vs. BIAS CONTROL VOLTAGE
vs. FREQUENCY
240
SUPPLY CURRENT (mA)
800MHz
220
200
900MHz
180
160
140
120
100
990MHz
MAX2402 TOC 5
25
23
900MHz
OUTPUT POWER (dBm)
21
19
17
15
13
11
9
7
0
1
2
3
990MHz
800MHz
260
4
5
0
1
2
3
4
5
BADJ VOLTAGE (V)
BADJ VOLTAGE (V)
AMPLITUDE OF 3rd & 5th HARMONICS
OF MODULATED WAVEFORM
OUTPUT POWER BELOW FUNDAMENTAL (dBC)
OUTPUT POWER (dBC) BELOW 900.1MHz
(100kHz SINEWAVE MODULATION OF 900MHz LO)
42
T
A
= +85°C
38
T
A
= +24°C
34
900.5MHz
30
T
A
= -40°C
26
T
A
= +85°C
22
900.3MHz
18
T
A
= +24°C
MAX2402 TOC 7
OUTPUT POWER LEVEL OF
2nd AND 3rd HARMONICS OF LO
(LO = 900MHz, -3dBm, MOD = 5V)
39
37
35
33
31
29
27
25
23
21
19
17
15
13
3rd HARMONIC
T = -40°C
A
T
A
= +24°C
MAX2402 TOC 6
T
A
= +85°C
T
A
= +85°C
T
A
= +24°C
T
A
= -40°C
0.5
1.0
1.5
2.0
2.5
2nd HARMONIC
14
10
T
A
= -40°C
1.0 1.5
2.0 2.5
3.0 3.5 4.0
4.5 5.0
3.0
3.5
4.0
MODULATION VOLTAGE, PEAK-TO-PEAK (V)
BADJ VOLTAGE (V)
_______________________________________________________________________________________
3
800MHz to 1000MHz Transmitter
MAX2402
_____________________Pin Description
PIN
1
2
3, 5, 8,
13, 15, 17,
18, 20
4, 12, 19
6
7
9
NAME
VGC
MOD
GND
FUNCTION
Variable Gain Control Input.
Connect to V
CC
for maximum gain.
Baseband Modulation Input to mixer
Ground
Supply Voltage, set between 4.75V
and 5.5V
Local-Oscillator Positive Input
Local-Oscillator Negative Input
Shutdown Control Input.
Low level = off, high level = on.
Bias Adjustment Control for power
amplifier. Connect resistor from
BADJ to V+ or GND (see Table 1).
Connect 27nH inductor from LGND
to GND to maximize output power.
Power-Amplifier Output
MOD Input
The mixer’s other port, the MOD input, remains linear
over a 2V range from about 1.5V to 3.5V at the input.
When driven with digital modulation (0V to 5V), this port
will completely limit, resulting in a hard BPSK-
modulated signal. Since this input is self biasing, carrier
suppression can be improved by externally capacitively
coupling the signal into the port (the MOD input resis-
tance is approximately 10kΩ). This would compensate
for voltage offset or duty-cycle offset at this port, thus
increasing carrier suppression. This MOD self bias is
designed for very low on-chip offset, resulting in excel-
lent carrier suppression. Since this port self biases
when the signal is removed from MOD, the mixer will
attenuate the output power by about 40dB, resulting in
further attenuation past that attained from VGC con-
trol—a useful feature for ASK modulation.
V
CC
LO+
LO-
SHDN
VGC Stage
The mixer output drives the VGC stage. This stage
attenuates through a multiplication technique that does
not distort the signal with increased attenuation. VGC
control is nonattenuating when connected to the V
CC
supply. VGC will attenuate for voltages from 2.5V to
1.0V. Most attenuation occurs between 1V and 2V.
Maximum attenuation is achieved below 0.8V. Typical
maximum attenuation is 40dB. At or beyond 40dB of
attenuation, the signal may be slightly nonmonotonic.
This means that there may be a slight upturn in the sig-
nal level at the low end of the VGC control range (typi-
cally about 1dB). Because of the stability implications,
we suggest that the user not plan on attenuating past
35dB within a feedback loop.
10
BADJ
11
14, 16
LGND
OUT
_______________Detailed Description
The MAX2402 transmitter is a versatile design that inte-
grates several RF functions on a single IC. It has a wide
variety of applications in portable and stationary wire-
less designs. Each of the functional blocks (shown in
the
Functional Diagram)
is described in detail in the fol-
lowing sections.
Power Amplifier
The VGC stage passes the signal to the power amplifi-
er. This class AB stage will produce at least 20dBm of
output power for almost the complete transmit frequen-
cy range (with T
A
= +25°C). See
Typical Operating
Characteristics.
LO Inputs
The LO inputs are internally capacitively coupled and
self biasing. The LO port can be driven differentially or
single ended. When terminated at the LO inputs with
50Ω, the transmitter will provide full output power for LO
inputs from -6dBm to +6dBm with single-ended drive,
and -12dBm to +6dBm with differential drive. Input
power beyond this range may saturate the LO input
buffer, while input power below this range may result in
less output power. The limiter is two cascaded differen-
tial stages, which also isolates the LO input from the
mixer. This will help reduce any frequency-pulling
effects in an external LO due to mixer loading. The lim-
iter output drives one port of a double-balanced Gilbert
mixer.
BADJ Input
The BADJ input adjusts the bias of the output stage.
Increasing this voltage decreases bias current in the
output devices, which increases efficiency, but also
increases harmonic distortion (since the stage will be
pushed further toward class B operation). Decreasing
BADJ’s voltage increases bias current in the output
devices, resulting in higher output power and less har-
monic distortion. Be sure to optimize BADJ for your
application.
4
_______________________________________________________________________________________
800MHz to 1000MHz Transmitter
BADJ can be left open or adjusted with a single pull-
up or pull-down resistor to V
CC
or GND, respectively.
The value of this resistor determines the amount of
adjustment applied. A single resistor results in no cur-
rent flow at BADJ during power-down (whereas a
resistor divider always has current flowing through the
resistors). Table 1 shows the approximate bias adjust
voltage at the pin for different resistor values. At lower
LO frequencies, where the transmitter gain and output
power is the highest, setting BADJ to a low voltage
(maximum bias current) causes excessive current in
the output and can cause unstable behavior in the IC.
At lower LO frequencies (around 800MHz), more than
22dBm of power is easily obtained with BADJ set for
3V or more. If higher bias current and less distortion is
desired in the 800MHz range, using a lower inductor
value on LGND (pin 11) (see the
Typical Application
Circuit)
might make the desired bias level stable. At
higher frequencies (near 1000MHz), a lower bias level
voltage results in more power (see the Output Power vs.
Bias Control Voltage vs. Frequency graph in the
Typical
Operating Characteristics).
Power Amplifier Output
The power amplifier has an open-collector output that
can drive into a load of 30Ω to 50Ω; however, maximum
power transfer is obtained at about 35Ω. 27nH to
ground is recommended on LGND (pin 11), as shown
in the
Typical Application Circuit.
This inductor is used
as a current source on the base of the output stage to
pull stored charge out of the base.
MAX2402
SHDN Input
The SHDN input completely shuts down the current
from the supply and all signal pins when switched
below 0.5V. During normal operation, SHDN should
remain above V
CC
- 0.5V.
The shutdown control shuts down the total current to
below 150nA (typ). Power-up occurs within 10µs.
__________Applications Information
The MAX2402 transmitter operates within the 800MHz
to 1000MHz frequency range. Figure 1 shows a typical
application circuit. Additional applications information
can be obtained from the MAX2402 evaluation kit
manual.
Table 1. Bias-Adjust Voltage for Various
Resistor Values
Resistor
Value (Ω)
10k
20k
30k
40k
50k
100k
200k
300k
400k
500k
1M
BADJ with Resistor
Connected to GND (V)*
0.36
0.63
0.84
1.00
1.13
1.54
1.89
2.05
2.13
2.20
2.31
BADJ with Resistor
Connected to V
CC
(V)
4.54
4.27
4.05
3.89
VARIABLE
GAIN CONTROL
MODULATION
1
VGC
2
3
MOD
GND
V
CC
GND
GND
20
V
CC
19
V
CC
GND
GND
18
17
16
OUT
15
V
CC
14
47nH
39pF
0.01µF
V
CC
39pF
4
5
MAX2402
50Ω
6
VCO
7
50Ω
8
SHUTDOWN
CONTROL
9
10
BADJ
300k
LGND
GND
SHDN
GND
V
CC
13
12
11
39pF
V
CC
LO+
LO-
GND
OUT
3.75
3.34
3.00
2.85
2.75
2.68
2.57
27nH
* Typical variation of BADJ over temperature and process is
less than 5%.
Figure 1. Typical Application Circuit
_______________________________________________________________________________________
5

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin