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19-1350 Rev 3; 12/00
IT
TION K
VALUA
E
BLE
AVAILA
900MHz Image-Reject Receivers
with Transmit Mixer
____________________________Features
o
Receive Mixer with 35dB Image Rejection
o
Adjustable-Gain LNA
o
Up to +2dBm Combined Receiver Input IP3
o
4dB Combined Receiver Noise Figure
o
Optimized for Common Receiver IF Frequencies:
10.7MHz (MAX2424)
70MHz (MAX2426)
o
PA Predriver Provides up to 0dBm
o
Low Current Consumption: 23mA Receive
20mA Transmit
9.5mA Oscillator
o
0.5µA Shutdown Mode
o
Operates from Single +2.7V to +4.8V Supply
________________General Description
The MAX2424/MAX2426 highly integrated front-end ICs
provide the lowest cost solution for cordless and ISM-
band radios operating in the 900MHz band. Both devices
incorporate a receive image-reject mixer (to reduce filter
cost) as well as a versatile transmit mixer. The devices
operate from a +2.7V to +4.8V single power supply,
allowing direct connection to a 3-cell battery stack.
The receive path incorporates an adjustable-gain LNA
and an image-reject downconverter with 35dB image
suppression. These features yield excellent combined
downconverter noise figure (4dB) and high linearity with
an input third-order intercept point (IIP3) of up to +2dBm.
The transmitter consists of a double-balanced mixer and
a power amplifier (PA) predriver that produces up to
0dBm (in some applications serving as the final power
stage). It can be used in a variety of configurations,
including BPSK modulation, direct VCO modulation, and
transmitter upconversion. For devices featuring trans-
mit as well as receive image rejection, refer to the
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
data sheet.
The MAX2424/MAX2426 have an on-chip local oscillator
(LO), requiring only an external varactor-tuned LC tank
for operation. The integrated divide-by-64/65 dual-mod-
ulus prescaler can also be set to a direct mode, in which
it acts as an LO buffer amplifier. Four separate power-
down inputs can be used for system power manage-
ment, including a 0.5µA shutdown mode.
The MAX2424/MAX2426 come in a 28-pin SSOP pack-
age.
MAX2424/MAX2426
_______________Ordering Information
PART
MAX2424EAI
MAX2426EAI
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
___________________Pin Configuration
TOP VIEW
V
CC
1
CAP1 2
RXOUT 3
GND 4
RXIN 5
28 GND
27 GND
26 GND
25 TANK
________________________Applications
Cordless Phones
Wireless Telemetry
Wireless Networks
Spread-Spectrum Communications
Two-Way Paging
V
CC
6
GND 7
GND 8
TXOUT 9
LNAGAIN 10
V
CC
11
TXIN 12
TXIN 13
MAX2424
MAX2426
24 TANK
23 V
CC
22 V
CC
21 PREOUT
20 PREGND
19 MOD
18 DIV1
17 VCOON
16 RXON
15 TXON
Functional Diagram appears at end of data sheet.
CAP2 14
SSOP
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
900MHz Image-Reject Receiver
with Transmit Mixer
MAX2424/MAX2426
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ...........................................................-0.3V to +5.5V
TXIN,
TXIN
Differential Voltage ..............................................+2V
Voltage on TXOUT......................................-0.3V to (V
CC
+ 1.0V)
Voltage on LNAGAIN, TXON, RXON, VCOON,
DIV1, MOD, TXIN,
TXIN............................-0.3V
to (V
CC
+ 0.3V)
RXIN Input Power..............................................................10dBm
TANK,
TANK
Input Power ...................................................2dBm
Continuous Power Dissipation (T
A
= +70°C)
SSOP (derate 9.50mW/°C above +70°C) ......................762mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10s) .................................+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
= +2.7V to +4.8V, no RF signals applied, LNAGAIN = Unconnected, V
TXIN
= V
TXIN
= 2.3V, V
VCOON
= 2.4V, V
RXON
= V
TXON
=
V
MOD
= V
DIV1
= 0.45V, PREGND = GND, T
A
= -40°C to +85°C. Typicals are at T
A
= +25°C, V
CC
= 3.3V, unless otherwise noted.)
(Note 1)
PARAMETER
Supply-Voltage Range
Oscillator Supply Current
Prescaler Supply Current
(÷ 64/65 mode) (Note 2)
Prescaler Supply Current
(buffer mode) (Note 3)
Receive Supply Current (Note 4)
Transmitter Supply Current (Note 5)
Shutdown Supply Current
Digital Input Voltage High
Digital Input Voltage Low
Digital Input Current
Note 1:
Note 2:
Note 3:
Note 4:
V
DIV1
= 2.4V
V
RXON
= 2.4V, PREGND = unconnected
V
RXON
= 0.45V, V
TXON
= 2.4V,
PREGND = unconnected
VCOON = RXON = TXON T
A
= +25°C
= MOD = DIV1 = GND
T
A
= -40°C to +85°C
RXON, TXON, DIV1, VCOON, MOD
RXON, TXON, DIV1, VCOON, MOD
Voltage on any one digital input = V
CC
or GND
±1
2.4
0.45
±10
PREGND = unconnected
CONDITIONS
MIN
2.7
9.5
4.2
5.4
23
20
0.5
10
TYP
MAX
4.8
14
6
8.5
36
32
UNITS
V
mA
mA
mA
mA
mA
µA
V
V
µA
≥25°C
guaranteed by production test, <25°C guaranteed through correlation to worst-case temperature testing.
Calculated by measuring the combined oscillator and prescaler supply current and subtracting the oscillator supply current.
Calculated by measuring the combined oscillator and LO buffer supply current and subtracting the oscillator supply current.
Calculated by measuring the combined receive and oscillator supply current and subtracting the oscillator supply current.
With LNAGAIN = GND, the supply current drops by 4.5mA.
Note 5:
Calculated by measuring the combined transmit and oscillator supply current and subtracting the oscillator supply current.
2
_______________________________________________________________________________________
900MHz Image-Reject Receiver
with Transmit Mixer
AC ELECTRICAL CHARACTERISTICS
(MAX2424/MAX2426 EV kit, V
CC
= +3.3V, f
RXIN
= 915MHz, P
RXIN
= -35dBm, V
TXIN
= V
TXIN
= 2.3V (DC bias), V
TXIN
= 250mVp-p,
f
TXIN
= 1MHz, V
LNAGAIN
= 2V, V
VCOON
= 2.4V, RXON = TXON = MOD = DIV1 = PREGND = GND, T
A
= +25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
MAX2424/MAX2426
RECEIVER
(V
RXON
= 2.4V, f
LO
= 925.7MHz (MAX2424), f
LO
= 985MHz (MAX2426))
Input Frequency Range
IF Frequency Range
Image Frequency Rejection
V
LNAGAIN
= V
CC
,
T
A
= +25°C (Note 8)
Conversion Power Gain
V
LNAGAIN
= V
CC
,
T
A
= -40°C to +85°C (Notes 6, 8)
V
LNAGAIN
= 1V (Note 8)
LNAGAIN = GND (Note 8)
Noise Figure
Input Third-Order Intercept
(IIP3)
Input 1dB Compression
LO to RXIN Leakage
Receiver Turn-On Time
LNAGAIN = V
CC
(Notes 6, 8)
V
LNAGAIN
= 1V (Notes 6, 8)
LNAGAIN = V
CC
(Notes 6, 9)
V
LNAGAIN
= 1V (Notes 6, 9)
LNAGAIN = V
CC
V
LNAGAIN
= 1V
Receiver on or off
(Note 10)
-19
MAX2424
MAX2426
MAX2424
MAX2426
(Notes 6, 7)
MAX2424 (Notes 6, 7)
MAX2426 (Notes 6, 7)
800
8.5
55
26
20
19
19
18
12
-16
4
12
-17
-8
-26
-18
-60
500
5
dB
dB
dBm
dBm
ns
10.7
70
35
22
21
24.5
23.5
25
24
dB
1000
12.5
85
MHz
MHz
dB
TRANSMITTER
(V
TXON
= 2.4V, f
LO
= 915MHz)
Output Frequency Range
Baseband 3dB Bandwidth
Output Power
Output 1dB Compression
Output Third-Order Intercept (OIP3)
Carrier Suppression
Output Noise Density
Transmitter Turn-On Time
(Note 13)
(Note 12)
T
A
= +25°C
T
A
= T
MIN
to T
MAX
(Note 6)
-9.5
-10
-0.5
3.5
30
-140
220
(Notes 6, 11)
800
125
-7
-5
-4.5
1000
MHz
MHz
dBm
dBm
dBm
dBc
dBm/Hz
ns
_______________________________________________________________________________________
3
900MHz Image-Reject Receiver
with Transmit Mixer
MAX2424/MAX2426
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2424/MAX2426 EV kit, V
CC
= +3.3V, f
RXIN
= 915MHz, P
RXIN
= -35dBm, V
TXIN
= V
TXIN
= 2.3V (DC bias), V
TXIN
= 250mVp-p,
f
TXIN
= 1MHz, V
LNAGAIN
= 2V, V
VCOON
= 2.4V, RXON = TXON = MOD = DIV1 = PREGND = GND, T
A
= +25°C, unless otherwise noted.)
PARAMETER
OSCILLATOR AND PRESCALER
Oscillator Frequency Range
Oscillator Phase Noise
(Note 6)
10kHz offset (Note 14)
Standby to TX or Standby to RX
Oscillator Pulling
MAX2424
MAX2426
MAX2424
MAX2426
800
82
72
8
35
70
110
500
T
A
= +25°C
T
A
= -40°C to +85°C
-11
-12
10
0
-8
mVp-p
dBm
ns
ns
kHz
1100
MHz
dBc/Hz
CONDITIONS
MIN
TYP
MAX
UNITS
RX to TX with P
RXIN
=-45dBm (RX mode) MAX2424
to P
RXIN
= 0dBm (TX mode) (Note 15)
MAX2426
Z
L
= 100kΩ
| |
10pF
V
DIV1
= 2.4V, Z
L
= 50Ω,
Z
L
= 50Ω
÷
64/65 mode
÷
64/65 mode
Prescaler Output Level
Oscillator Buffer Output Level
(Notes 6, 14)
Required Modulus Setup Time
(Notes 6, 16)
Required Modulus Hold Time
(Notes 6, 16)
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
Note 16:
Guaranteed by design and characterization.
Image rejection typically falls to 30dBc at the frequency extremes.
Refer to the
Typical Operating Characteristics
for a plot showing Receiver Gain vs. LNAGAIN Voltage, Input IP3 vs.
LNAGAIN Voltage, and Noise Figure vs. LNAGAIN Voltage.
Two tones at P
RXIN
= -45dBm each, f1 = 915.0MHz and f2 = 915.2MHz.
Time delay from V
RXON
= 0.45V to V
RXON
= 2.4V transition to the time the output envelope reaches 90% of its final value.
Output power typically falls to -10dBm at the frequency extremes.
Two tones at V
TXIN
= 125mVp-p, f1 = 1.0MHz, and f2 = 1.2MHz.
Time delay from V
TXON
= 0.45V to V
TXON
= 2.4V transition to the time the output envelope reaches 90% of its final value.
Using tank components L3 = 5.0nH (Coilcraft A02T), C2 = C3 = C26 = 3.3pF, R6 = R7 = 10Ω.
This approximates a typical application in which TXOUT is followed by an external PA and a T/R switch with finite isolation.
Relative to the rising edge of PREOUT.
4
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