Maxim MAX2511EEI Datasheet

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_______________General Description

The MAX2511 is a complete, highly integrated IF trans­ceiver for applications employing a dual-conversion
architecture. Alternatively, the MAX2511 can be used
as a single-conversion transceiver if the RF operating
frequency ranges from 200MHz to 440MHz.

In a typical application, the receiver downconverts a
high IF/RF (200MHz to 440MHz) to a 10.7MHz low IF
using an image-reject mixer. Functions include an
image-reject downconverter with 34dB of image sup­pression followed by an IF buffer that can drive an off­chip IF filter; an on-chip limiting amplifier offering 90dB
of monotonic received-signal-strength indication (RSSI);
and a robust limiter output driver. The transmit image­reject mixer generates a clean output spectrum to mini­mize filter requirements. It is followed by a 40dB
variable-gain amplifier that maintains IM3 levels below

-35dBc. Maximum output power is 2dBm. A VCO and
oscillator buffer for driving an external prescaler are
also included.

The MAX2511 operates from a 2.7V to 5.5V supply and
includes flexible power-management control. Supply
current is reduced to 0.1µA in shutdown mode.

For applications using in-phase (I) and quadrature (Q)
baseband architecture for the transmitter, Maxim offers
a corresponding transceiver product: the MAX2510.
The MAX2510 has features similar to those of the
MAX2511, but upconverts I/Q baseband signals using
a quadrature upconverter.

________________________Applications

PWT1900 Wireless Handsets and
Base Stations

PACS, PHS, DECT and Other PCS
Wireless Handsets and Base Stations

400MHz ISM Transceivers
IF Transceivers
Wireless Data Links

____________________________Features

♦ Single +2.7V to +5.5V Supply
♦ Complete Receive Path:

200MHz to 440MHz (first IF) to
8MHz to 13MHz (second IF)

♦ Limiter with Differential Outputs (adjustable level)
♦ RSSI Function with 90dB Monotonic Dynamic

Range

♦ Complete Transmit Path:

8MHz to 13MHz (second IF) to
200MHz to 440MHz (first IF)

♦ On-Chip Oscillator with Voltage Regulator

and Buffer

♦ Advanced System Power Management

(four modes)

♦ 0.1µA Shutdown Supply Current

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

________________________________________________________________

Maxim Integrated Products

1

28
27
26
25
24
23

21
20

19
18
17
16
15

1LIMIN VREF

MIXOUT
GND
RXIN
TXOUT
TXOUT

V

CC

V

CC

GND

TXEN
RXEN
TXIN
TXIN

CZ
CZ

RSSI

GC

TANK

TANK

GND

OSCOUT

LIMOUT
LIMOUT

V

CC

V

CC

2
3
4
5
6

8

9
10
11
12
13
14

QSOP

TOP VIEW

MAX2511

22 RXINGND 7

__________________Pin Configuration

PART

MAX2511EEI -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

28 QSOP

EVALUATION KIT

AVAILABLE

______________Ordering Information

Typical Operating Circuit appears at end of data sheet.

19-1209; Rev 0; 10/97

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS

(VCC= +2.7V to +5.5V, 0.01µF across CZ and CZ; TANK = TANK; MIXOUT tied to VREF through a 165Ω resistor; GC open, RXIN =

RXIN; TXOUT = TXOUT = V

CC

; TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°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.

VCCto GND .............................................................-0.3V to 8.0V

V

CC

to Any Other VCC........................................................±0.3V

TXIN, TXIN Input Voltage............................-0.3V to (V

CC

+ 0.3V)

TXIN to TXIN Differential Voltage....................................±300mV

RXIN, RXIN Input Voltage........................................-0.3V to 1.6V

TANK, TANK Voltage...............................................-0.3V to 2.0V

LIMIN Voltage .............................(VREF - 1.3V) to (VREF + 1.3V)

LIMOUT, LIMOUT Voltage ..............(V

CC

- 1.6V) to (VCC+ 0.3V)

RXEN, TXEN, GC Voltage...........................-0.3V to (V

CC

+ 0.3V)

RXEN, TXEN, GC Input Current............................................1mA

RSSI Voltage...............................................-0.3V to (VCC+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

QSOP (derate 11mW/°C above 70°C) ...........................909mW

Operating Temperature Range

MAX2511EEI......................................................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +165°C

Lead Temperature (soldering, 10sec).............................+300°C

Internally terminated to 1.35VGC Input Resistance 60 80 125

kΩ

LIMOUT, LIMOUT
Differential Output Impedance

2

kΩ

(Note 1)

RXEN, TXEN

RXEN, TXEN

CONDITIONSPARAMETER MIN TYP MAX UNITS

Digital Input Current Low -5 -1 µA

Digital Input Current High 23 32 µA

VREF Voltage

V

CC

/ 2 - V

CC

/ 2 V

CC

/ 2 +

100mV 100mV

V

Digital Input Voltage High

Operating Voltage Range 2.7 3.0 5.5 V

2.0 V

Digital Input Voltage Low 0.4 V

24

26

9.5

VCC= 3.0V
TA= +25°C

Typical Supply Current

0.1

mA

38.5

45

14.5

VCC= 2.7V to 5.5V,
TA= -40°C to +85°C

Worst-Case Supply Current

5

mA

µA

µA

Rx mode, RXEN = high,
TXEN = low

Tx mode, RXEN = low,
TXEN = high, VGC= 0.5V

Standby mode, RXEN = high,
TXEN = high

Shutdown mode, RXEN = low,
TXEN = low

Rx mode, RXEN = high,
TXEN = low

Tx mode, RXEN = low,
TXEN = high, VGC= 0.5V

Standby mode, RXEN = high,
TXEN = high

Shutdown mode, RXEN = low,
TXEN = low

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

_______________________________________________________________________________________ 3

AC ELECTRICAL CHARACTERISTICS

(MAX2511 test fixture, VCC= +3.0V, RXEN = TXEN = low, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor,
TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded
with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 330pF at RSSI
pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz,

f

LO

= 435.7MHz, f

TXIN, TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

21.5 23.6 25.5

dBm-16

Downconverter Mixer Input 1dB
Compression Level

dBm-11Input Third-Order Intercept

dB25 34Image Rejection

UNITSMIN TYP MAXPARAMETER CONDITIONS

TA= +25°C

(Note 2)

Two tones at 424MHz and 425MHz,

-30dBm per tone
f

IMAGE

= fLO+ fIF= 446.4MHz

Vp-p2MIXOUT Maximum Voltage Swing

µs5Power-Up Time Standby to RX or TX (Note 3)

mVp-p

120 160

Limiter Output Level

VGC= 0.8V (Note 4)

475 625
950 1100

degrees3.6Phase Variation

-75dBm to 5dBm from 50Ω
dB80Minimum Linear RSSI Range

-75dBm to 5dBm from 50Ω
dB90Minimum Monotonic RSSI Range

-80dBm to 10dBm from 50Ω

mV/dB10.6RSSI Slope

-75dBm to 5dBm from 50Ω

dBm-82 -75RSSI Maximum Intercept (Note 5)

µs6.4RSSI Rise Time

Rise time to within 1dB accuracy; using a 100pF
capacitor from RSSI to GND

mV50 90 135Minimum-Scale RSSI Voltage At LIMIN input of -75dBm
mV850 940 1025Maximum-Scale RSSI Voltage At LIMIN input of 5dBm

dBm-65LO Leakage At RXIN port

-12 -9TA= +25°C (Note 8)

µs220Maximum Power-Up Time Shutdown to standby mode (Note 9)

dBc/Hz-88Phase Noise

MHz200 440Frequency Range

kHz±36Maximum LO Frequency Pulling

(Note 7)
At 10kHz offset
Standby mode to TX or RX mode

±1 ±2TA= +25°C

dB14Downconverter Mixer Noise Figure

dB

20 27

Downconverter Mixer Voltage Gain

TA= -40°C to +85°C (Note 1)

dB

±2.5

RSSI Relative Error

TA= -40°C to +85°C (Note 1)

dBm

-13

Oscillator Buffer Output Power

TA= -40°C to +85°C (Notes 1 and 8)

VGC= 2.0V (P

LIMIN

= +5dBm)

VGC= open

DOWNCONVERTER (RXEN = high)

LIMITING AMPLIFIER AND RSSI (RXEN = high)

OSCILLATOR (TXEN = RXEN = high)

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

4 _______________________________________________________________________________________

Note 1: Guaranteed by design and characterization.
Note 2: Driving RXIN or RXIN with a power level greater than the 1dB compression level forces the input stage out of its linear

range, causing harmonic and intermodulation distortion. The RSSI output increases monotonically with increasing input
levels beyond the mixer’s 1dB compression level.

Note 3: Assuming the supply voltage has been applied, this includes settling of the limiter offset correction and the Rx or Tx bias

stabilization time. Guaranteed by design.

Note 4: LIMOUT, LIMOUT loaded with 2kΩ differential. With no load, the output swing is approximately twice as large.
Note 5: The RSSI maximum intercept is the maximum input power (over a statistical sample of parts) at which the RSSI output is 0V.

This point is extrapolated from the linear portion of the RSSI voltage versus limiter input power. This specification and the
RSSI slope define the ideal behavior of the RSSI function (the slope and intercept of a straight line), while the RSSI relative
error specification defines the deviations from this line. See the RSSI Output Voltage vs. Limiter Input Power graph in the

Typical Operating Characteristics

.

Note 6: The RSSI relative error is the deviation from the best-fitting straight line of RSSI output voltage versus limiter input power.

A 0dB relative error is exactly on this line. The limiter input power range for this test is -75dBm to +5dBm from 50Ω. See the
RSSI Relative Error graph in the

Typical Operating Characteristics

.

Note 7: Operation outside this frequency range is possible but has not been characterized. At lower frequencies, it might be

necessary to overdrive the oscillator with an external signal source.

Note 8: If a larger output level is required, a higher value of load resistance (up to 100Ω) may be used.
Note 9: This assumes that the supply voltage has been applied, and includes the settling time of V

REF

, using the

Typical

Operating Circuit.

Note 10: Using two tones at 10.7MHz and 10.8MHz, 50mVp-p per tone at TXIN, TXIN. See

Typical Operating Characteristics

.

-44

Output Power

VGC= 0.5V, TA= +25°C

dBm

-19VGC= open, TA= +25°C

-5 -2VGC= 2.0V, TA= +25°C

-6VGC= 2.0V, TA= -40°C to +85°C (Note 1)

dBc40 30LO Rejection

dBm2Output 1dB Compression Point VGC= 2.0V

UNITSMIN TYP MAXPARAMETER CONDITIONS

AC ELECTRICAL CHARACTERISTICS (continued)

(MAX2511 test fixture, VCC= +3.0V, RXEN = TXEN = low, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor,
TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded
with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 330pF at RSSI
pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz,

f

LO

= 435.7MHz, f

TXIN, TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

-40

Output IM3 Level

0.5V < VGC< 1.87V

-40dBm < P

OUT

< -10dBm (Note 10)

dBc

-35VGC= 2.0V

dBc34 25Image Rejection

TRANSMITTER (TXEN = high, V

TXIN

and V

TXIN

= 100mVp-p differential)

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

_______________________________________________________________________________________

5

40
35

Tx MODE

Rx MODE

STANDBY MODE

0

-40 85

SUPPLY CURRENT

vs. TEMPERATURE

10

5

30
25

MAX2511 TOC01

TEMPERATURE (°C)

I

CC

(mA)

25

20
15

40
35

0

2.7 3.0 5.5

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

10

5

30
25

MAX2511 TOC02

VCC (V)

I

CC

(mA)

4.0 4.5 5.03.5

20
15

STANDBY MODE

Tx MODE

Rx MODE

50

45

20

0 0.4

SUPPLY CURRENT

vs. GC VOLTAGE

40

30

35

MAX2511 TOC03

GC VOLTAGE (V)

I

CC

(mA)

1.6 2.0 2.4 2.8 3.21.20.8

25

Tx MODE

Rx MODE

2.5

0

2.7 3.0 5.5

SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE

0.5

2.0

1.5

MAX2511 TOC04

SUPPLY VOLTAGE (V)

I

CC

(µA)

4.0 4.5 5.03.5

1.0

TA = +85°C

TA = +25°C

TA = -40°C

25

24

23

21

20

22

19

MAX2511-TOC05

VCC (V)

2.7 3.0 3.5 4.0 4.5 5.0 5.5

DOWNCONVERTER MIXER CONVERSION

GAIN vs. SUPPLY VOLTAGE

GAIN (dB)

RXEN = HIGH
TXEN = LOW

TA = +85°C

TA = +25°C

TA = -40°C

22.0

23.0

22.5

23.5

24.5

24.0

RXEN = HIGH
TXEN = LOW

25.0

200 275 350 425

DOWNCONVERTER GAIN

vs. RXIN FREQUENCY

MAX2511/TOC07A

RXIN FREQUENCY (MHz)

VOLTAGE GAIN (dB)

__________________________________________Typical Operating Characteristics

(MAX2511 test fixture, VCC= +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF
through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential,
TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at VREF pin,
Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz, f

LO

= 435.7MHz, f

TXIN,

TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

6 _______________________________________________________________________________________

70

60

50

30

20

40

0

10

MAX2511-TOC09

VCC (V)

DOWNCONVERTER INPUT 1dB

COMPRESSION LEVEL

1dB COMPRESSION LEVEL (mVrms)

TXEN = LOW
RXEN = HIGH

TA = +85°C

TA = +25°C

TA = -40°C

2.7 3.0 3.5 4.0 4.5 5.0 5.5

-250

0

-100

100

-200

50

-50

-150

RX OFF REAL

150

200

250

200 300 400 500

RXIN DIFFERENTIAL INPUT IMPEDANCE

vs. FREQUENCY

MAX2511/TOC10

FREQUENCY (MHz)

REAL AND IMAGINARY IMPEDANCE (Ω)

RX OFF IMAGINARY

RX MODE REAL

RX MODE IMAGINARY

1.2

0

0 0.4

LIMITER OUTPUT LEVEL

vs. GC VOLTAGE

1.0

MAX2511-TOC11

GC VOLTAGE (V)

OUTPUT LEVEL (Vp-p)

1.2 1.60.8 2.4 2.8 3.02.0

.6

.8

.4

.2

TA = -40°C
T

A

= +25°C

TA = +85°C

TXEN = LOW
RXEN = HIGH

____________________________Typical Operating Characteristics (continued)

(MAX2511 test fixture, VCC= +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to

VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differ-
ential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at
VREF pin, Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz, f

LO

= 435.7MHz,

f

TXIN, TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

25

35

30

40

45

200 300 400250 350 425

DOWNCONVERTER IMAGE REJECTION

vs. RXIN FREQUENCY

MAX2511/TOC0A1

FREQUENCY (MHz)

IMAGE REJECTION (dB)

26

28

30

32

34

36

38

40

-40 -20 0 20 40 60 85

DOWNCONVERTER-MIXER IMAGE

REJECTION vs. TEMPERATURE

AND SUPPLY VOLTAGE

MAX2511 TOC0A2

TEMPERATURE (°C)

Rx IMAGE REJECTION (dBc)

VCC = 5.5V

V

CC

= 2.7V

V

CC

= 3.0V

40

0

0 10 20 30 40 50

DOWNCONVERTER IMAGE REJECTION

vs. IF FREQUENCY

30

MAX2511-TOC08

IF FREQUENCY (MHz)

IMAGE REJECTION (dB)

20

10

35

25

15

5

TXEN = LOW
RXEN = HIGH

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

_______________________________________________________________________________________ 7

____________________________Typical Operating Characteristics (continued)

(MAX2511 test fixture, VCC= +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to

VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differ-
ential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at
VREF pin, Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz, f

LO

= 435.7MHz,

f

TXIN, TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

-65

-50

-55

-60

-30

-35

-40

-45

-10

-15

-20

-25

5
0

-5

0 0.4 1.20.8 1.6 2.0 2.4 2.7

TRANSMITTER OUTPUT POWER

vs. GC VOLTAGE (FREQUENCY)

MAX2511TOCB

GC VOLTAGE (V)

Tx P

OUT

(dBm)

205MHz

430MHz

260MHz
350MHz

-1000

-800

Tx OFF REAL

Tx MODE REAL

-900

-600

-700

0

-400

-500

-300

-200

-100

100

200 400300 500

TRANSMITTER DIFFERENTIAL

OUTPUT IMPEDANCE vs. FREQUENCY

MAX2511 TOC21

FREQUENCY (MHz)

REAL AND IMAGINARY IMPEDANCE Ω

Tx OFF
IMAGINARY

Tx MODE
IMAGINARY

-20

-100
0 0.4

UPCONVERTER IM3 LEVELS vs.

GC VOLTAGE (POWERS ARE PER TONE)

-40

MAX2511-TOC16a

GC VOLTAGE (V)

INTERMODULATION POWER (dBm)

1.2 1.60.8 2.4 2.82.0

-60

-30

-50

-70

-80

-90

-50

-45

-40

-30

-35

-20

-25

-15

-10

-5

0

-40 0 20-20 40 60 85

TRANSMITTER OUTPUT POWER

vs. TEMPERATURE, SUPPLY,

AND GC VOLTAGE

MAX2511tocC

TEMPERATURE (°C)

TX PORT (dBm)

VGC = 2V

VGC = OPEN

VGC = 0.5V

VCC = 2.7V
VCC = 5.5V

VCC = 2.7V
VCC = 5.5V

VCC = 5.5V
VCC = 2.7V

-5.0

-4.5

-4.0

-3.0

-3.5

-2.5

-2.0

-1.5

-1.0

-0.5

-40 0 20-20 40 60 85

TRANSMITTER OUTPUT POWER

vs. TEMPERATURE AND SUPPLY

GC VOLTAGE (GC = 2V)

MAX2511TOCD

TEMPERATURE (°C)

Tx P

OUT

(dBm)

VCC = 5.5V

VCC = 2.7V

5

15

10

25

20

30

35

0 10.7 3020 40 50

UPCONVERTER IMAGE REJECTION

vs. IF FREQUENCY

MAX2511 TOC20

IF FREQUENCY (MHz)

IMAGE REJECTION (dB)

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

8 _______________________________________________________________________________________

____________________________Typical Operating Characteristics (continued)

(MAX2511 test fixture, VCC= +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to

VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differ-
ential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at
VREF pin, Rx inputs and Tx outputs differentially coupled, P

RXIN, RXIN

= -28dBm (200Ω system), f

RXIN, RXIN

= 425MHz, f

LO

= 435.7MHz,

f

TXIN, TXIN

= 10.7MHz, TA= +25°C, unless otherwise noted.)

.3
.2
.1

0

.7

.5

.6

.4

.9
.8

1.1
1

-120 -100 -80 -60 -40 -20 0 20

RSSI OUTPUT VOLTAGE vs. LIMIN

INPUT POWER AND TEMPERATURE

MAX2511 TOC13

P

LIMIN

(dBm, 50Ω)

RSSI OUTPUT (V)

TA = +85°C

TA = -40°C

TA = +25°C

-5

-3

-4

0

-1

-2

1

2

4
3

5

-90 -70 -60-80 -50 -40 -30 -20 -10 0 10 20

RSSI RELATIVE ERROR

vs. LIMIN INPUT AND TEMPERATURE

MAX2511 TOC2514

P

LIMIN

(dBm, 50Ω)

RSSI ERROR (dB)

TA = +85°C

TA = -40°C

TA = +25°C

26

28

30

32

34

36

38

40

-40 0 20-20 40 60 85

TRANSMITTER IMAGE REJECTION vs.

TEMPERATURE AND SUPPLY VOLTAGE

MAX2511TOCE

TEMPERATURE (°C)

Tx IMAGE REJECTION (dBc)

VCC = 5.5V

VCC = 2.7V

VCC = 3.3V

1.1

0.1

0.3

0.2

-120 -80-100 -60

MIXER INPUT-REFERRED RSSI VOLTAGE

vs. RXIN INPUT POWER

0.9

MAX2511-TOC15

P

RXIN

(dBm, 50Ω)

RSSI VOLTAGE (V)

-20-40 0 10

0.7

1.0

0.8

0.6

0.5

0.4

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

_______________________________________________________________________________________ 9

______________________________________________________________Pin Description

Oscillator-Buffer Output. OSCOUT provides a buffered oscillator signal (at the oscillator frequency)
for driving an external prescaler. This pin is a current output and must be AC-coupled to a resistive
load. The output power is typically -9dBm into a 50Ω load. If a larger output swing is required, a
larger load resistance (up to 100Ω) can be used.

OSCOUT12

Tank pins. Connect the resonant tank across these pins, as shown in the

Typical Operating Circuit.

TANK, TANK

6, 9

Ground. Connect GND to the PC board ground plane with minimal inductance.GND7, 10
Supply Voltage. Bypass V

CC

directly to GND. See the

Layout Issues

section.V

CC

8, 11

Gain-Control pin in transmit mode. Applying a DC voltage to GC between 0V and 2.0V adjusts the
transmitter gain by 40dB. In receive mode, GC adjusts the limiter output level from 0Vp-p to about
1Vp-p. This pin’s input impedance is typically 80kΩ terminated to 1.35V.

GC5

Receive-Signal-Strength-Indicator Output. The voltage on RSSI is proportional to the signal power at
LIMIN. The RSSI output sources current pulses into an external capacitor (100pF typ). The output is
internally terminated with 6kΩ, and this RC time constant sets the decay time.

RSSI4

PIN

Offset-Correction Capacitor pins. Connect a 0.01µF capacitor between CZ and CZ.CZ, CZ

2, 3

Limiter Input. Connect a 330Ω (typ) resistor to VREF for DC bias, as shown in the

Typical Operating

Circuit.

LIMIN1

FUNCTIONNAME

Receiver Front-End Ground. Connect GND to the PC board ground plane with minimal inductance.GND26
Single-Ended Output of the Image-Reject Downconverter. MIXOUT is high impedance and must be

biased to the VREF pin through an external terminating resistor whose value depends on the inter­stage filter characteristics. See the

Applications Information

section for more details.

MIXOUT27

Reference Voltage pin. VREF is used to provide an external bias voltage for the MIXOUT and LIMIN
pins. Bypass this pin with a 0.1µF capacitor to ground. VREF voltage is equal to VCC/ 2. See the

Typical Operating Circuit

for more information.

VREF28

Bias VCCSupply pins. Decouple these pins to GND. See the

Layout Issues

section.V

CC

19, 21

Receiver/Transmitter Ground pin. Connect to the PC board ground plane with minimal inductance.GND20
Differential Inputs of the Image-Reject Downconverter Mixer. In most applications, an impedance

matching network is required. See the

Applications Information

section for more details.

RXIN, RXIN

22, 25

Differential Outputs of the Image-Reject Upconverter. TXOUT and TXOUT must be pulled up to V

CC

with two external inductors and AC coupled to the load.

TXOUT, TXOUT

23, 24

Transmitter-Enable pin. When high, TXEN enables the transmitter, if RXEN is low. If both TXEN and
RXEN are high, the part is in standby mode; if both are low, the part is in shutdown. See the

Power

Management

section for more details.

TXEN18

Receiver-Enable pin. When high, RXEN enables the receiver if TXEN is low. If both RXEN and TXEN
are high, the part is in standby mode; if both are low, the part is in shutdown. See the

Power

Management

section for more details.

RXEN17

Differential Inputs of the Image-Reject Upconverter Mixer. TXIN and TXIN are high impedance and
must be pulled up to V

CC

through two external resistors whose value is equal to the desired termi-

nating impedance (50Ω to 50kΩ).

TXIN, TXIN

15, 16

Differential Outputs of the Limiting Amplifier. LIMOUT and LIMOUT are open-collector outputs that
are internally pulled up to V

CC

through 1kΩ resistors.

LIMOUT,

LIMOUT

13, 14

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

10 ______________________________________________________________________________________

_______________Detailed Description

The following sections describe each of the blocks
shown in Figure 1.

Receiver

The receiver consists of two basic blocks: the image­reject downconverter mixer and the limiter/RSSI section.

The receiver inputs are the RXIN, RXIN pins, which
should be AC coupled and may require a matching net­work, as shown in the

Typical Operating Circuit.

To
design a matching network for a particular application,
refer to the

Applications Information

section and the

receiver input impedance plots in the

Typical Operating

Characteristics

.

Image-Reject Mixer

The downconverter is implemented using an image­reject mixer consisting of an input buffer with dual out­puts, each of which is fed to a double-balanced mixer.
The LO signal is generated by an on-chip oscillator and
an external tank circuit. The buffered oscillator signal
drives a quadrature phase generator that provides two
outputs with 90° of phase shift between them. This pair
of LO signals is fed to the two receive mixers. The
mixer’s outputs are then passed through a pair of
phase shifters, which provide 90° of phase shift across
their outputs. The resulting two signals are then
summed together. The final phase relationship is such
that the desired signal is reinforced, and the image sig­nal is largely canceled. The downconverter mixer’s

0°

RXIN

RXIN

VREF = V

CC

/ 2

90°

0°

MIXOUT

LIMIN

VREF

CZ CZ

IF BPF

LIMITER

LIMOUT

RSSI

RXEN

TXEN

LIMOUT

VGA

OFFSET

CORRECTION

RECEIVE IMAGE-REJECT MIXER

TRANSMIT IMAGE-REJECT MIXER AND VGA/PA

Σ

Σ

RSSI

90°

TANK

TANK

OSCOUT

TXOUT

PA

VGA

TXOUT

0°

90°

LO PHASE

SHIFTER

TXIN

TXIN

GC

VOLTAGE GAIN

AND BIAS CONTROL

BIAS

GM

MAX2511

Figure 1. Functional Diagram

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

______________________________________________________________________________________ 11

output is buffered and converted to a single-ended cur­rent output at the MIXOUT pin, which can drive a shunt­terminated bandpass filter over a large dynamic range.
MIXOUT can drive a shunt-terminated 330Ω filter (165Ω
load) to more than 2Vp-p over the entire supply range.

Limiter

The signal passes through an external IF bandpass fil­ter into the limiter input (LIMIN). LIMIN is a single­ended input that is centered around the VREF pin
voltage. Open-circuit input impedance is typically
greater than 10kΩ terminated to VREF. For proper oper­ation, LIMIN must be tied to VREF through the filter ter­minating impedance (not more than 1kΩ). The limiter
provides a constant output level, which is largely inde­pendent of the limiter input-signal level over an 80dB
input range.

The adjustable output level allows easy interfacing of
the limiter output to the downstream circuitry. The lim­iter’s output drives a variable-gain amplifier that adjusts
the limited output level from 0Vp-p to typically 1Vp-p as
the GC pin voltage is adjusted from 0.5V to 2.0V. Using
this feature allows the downstream circuitry, such as an
analog-to-digital converter (ADC), to run at optimum
performance by steering the limiter’s output level to
match the desired ADC input level. GC is also used for
transmit (Tx) gain adjustment in Tx mode, so be sure to
keep the voltage at an appropriate value for each mode.

Received-Signal-Strength Indicator

The RSSI output provides a linear indication of the
received power level on the LIMIN input. The RSSI
monotonic dynamic range exceeds 90dB while provid­ing better than 80dB linear range. The RSSI output
pulses current into an external filter capacitor (typically
100pF). The output is internally terminated with 6kΩ to
GND, and this R-C time constant sets the decay time.

Transmitter

The image-reject upconverter mixer operates in a fash­ion similar to the downconverter mixer. The transmit
mixer consists of an input buffer amplifier that drives
on-chip IF phase shifters. The shifted signals are then
input to a pair of double-balanced mixers, which are
driven with the same quadrature (Q) LO source used
by the receiver. The mixer outputs are summed togeth­er, largely canceling the image signal component. The
image-canceled signal from the mixer outputs is fed
through a variable-gain amplifier (VGA) with 40dB of
gain-adjust range.

The VGA output is connected to a driver amplifier with
an output 1dB compression point of 2dBm. The output
power can be adjusted from approximately 2dBm

to less than -40dBm by controlling the GC pin. For
output levels between -10dBm and -40dBm, -40dBc
IM3 levels are maintained. The resulting signal appears
as a differential output on TXOUT and TXOUT, which
expect a 100Ω differential load impedance.

TXOUT and TXOUT are open-collector outputs and
need external pull-up inductors to V

CC

for proper oper­ation. They also need a DC block so the load does not
affect DC biasing. A shunt resistor across TXOUT,
TXOUT can be used to back-terminate an external filter,
as shown in the

Typical Operating Circuit

. It is possible
to use the receiver inputs RXIN and RXIN to provide
this termination, as described in the

Filter Sharing

sec­tion. For single-ended operation, tie the unused input to
VCC.

Local Oscillator and Oscillator Buffer

The on-chip LO requires only an external LC tank circuit
for operation. The tank circuit is connected across
TANK and TANK. A dual varactor diode is typically used
to adjust the frequency in a phase-locked loop (PLL).
See the

Applications Information

section for the tank cir-

cuit design equations. Keep the resonator’s Q as high

VBIAS

V

CC

Figure 2. Simplified Oscillator Equivalent Circuit

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

12 ______________________________________________________________________________________

as possible for lowest phase noise. The tank’s PC board
layout is also critical to good performance (consult the

Layout Issues

section for more information).

The OSCOUT pin buffers the internal oscillator signal
for driving an external PLL. This output should be AC
coupled and terminated at the far end (typically the
input to a prescaler) with a 50Ω load. If a larger output
level is desired, you can use a resistive termination up
to 100Ω. When a controlled-impedance PC board is
used, this trace’s impedance should match the termina­tion impedance.

Power Management

The MAX2511 features four power-supply modes to pre­serve battery life. These modes are selected via the
RXEN and TXEN pins, according to Table 1.

In shutdown mode, all part functions are off. In standby
mode, the LO and the LO buffer are active. This allows
a PLL (implemented externally to the MAX2511) to
remain up and running, avoiding any delay resulting
from PLL loop settling. Transmit (Tx) mode enables the
LO circuitry, upconverter mixer, transmit VGA, and out­put driver amplifier. Receive (Rx) mode enables the LO
circuitry, downconverter mixer, limiting amplifier, and
adjustable output level amplifier.

__________Applications Information

400MHz ISM Applications

The MAX2511 can be used in applications where the
200MHz to 440MHz signal is an RF (rather than an IF)
signal, such as in 400MHz ISM applications. In this
case, we recommend preceding the MAX2511 receiver
section with a low-noise amplifier (LNA) that can oper­ate over the same supply-voltage range. The
MAX2630–MAX2633 family of amplifiers meets this
requirement. But since these parts have single-ended
inputs and outputs, it is necessary to AC terminate the
unused MAX2511 input (RXIN) to ground with 47nF.

Oscillator Tank

The on-chip oscillator circuit requires a parallel reso­nant tank circuit connected across TANK and TANK.
Figure 3 shows an example of an oscillator tank circuit.
Inductor L1 is resonated with the effective total capaci­tance of C1 in parallel with the series combination of
C2, C3, and (CD1) / 2. CD1 is the capacitance of one
of the varactor diodes. Typically, C2 = C3 to maintain
symmetry. The effective parasitic capacitance, C

P

(including PCB parasitics), is approximately 3.5pF. The
total capacitance is given by the following equation:

Using this value for the resonant tank circuit, the oscil­lation frequency is as follows:

EMBED Equation.2

Starting with the inductor recommended in Table 2,
choose the component values according to your appli­cation needs, such as phase noise, tuning range, and
VCO gain. Keep the tank’s Q as high as possible to
reduce phase noise. For most of the MAX2511’s appli­cations (such as a first IF to second IF transceiver), the
oscillator’s tuning range can be quite small, since the IF
frequencies are not tuned for channel selection. This
allows a narrowband oscillator tank to be used, which
typically provides better phase noise and stability per­formance than wideband tank circuits. Careful PC
board layout of the oscillator tank is essential. See the

Layout Issues

section for more information.

To overdrive the oscillator from an external 50Ω source,
see Figure 4.

Rx Input Impedance Matching

The RXIN, RXIN port typically needs an impedance­matching network for proper connection to external cir­cuitry such as a filter. See the

Typical Operating Circuit

for an example circuit topology. A shunt resistor across
RXIN, RXIN can be used to set terminating impedance,
with a slight degradation of the Noise Figure.

The component values used in the matching network
depend on the desired operating frequency as well as
the filter impedance. Table 3 indicates the RXIN, RXIN
differential input impedance in both series and parallel
form. This data is also plotted in the

Typical Operating

Characteristics

.

F =

1

L C

OSC

1 EFF

2π

C =

1

2

C2

2

C

C1 C

EFF

D1

P

+

+ +

RXEN

STATE

Low Low

TXEN

STATE

MODE

Shutdown

Table 1. Power-Supply Mode Selection

Low High Transmit
High Low Receive
High High Standby

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

______________________________________________________________________________________ 13

Filter Sharing

In half-duplex or TDD applications, the number of exter­nal filters can be minimized by combining transmit and
receive filter paths (Figure 5).

The 10.7MHz filter that is usually connected to the
TXIN, TXIN ports can be the same filter that is connect­ed at LIMOUT and LIMOUT. To use the same filter, con­nect TXIN to LIMOUT, and TXIN to LIMOUT.

The 425MHz SAW filter needed at the RXIN, RXIN ports
and the filter needed at TXOUT and TXOUT can be
shared in a similar manner. The RXIN, RXIN ports must
be DC blocked to prevent the bias voltage needed by
the TXOUT and TXOUT pins from entering the receiver.

When sharing filters in this manner, the transmitter out­put port (TXOUT, TXOUT) and receiver input port (RXIN,
RXIN) matching networks must be modified. The receiv­er port’s input impedance must be the parallel combi­nation of the receiver and transmitter ports in Rx mode.
In this case, the receiver port is active, but the transmit­ter port adds an additional parasitic impedance. See
the transmitter and receiver-port impedance graphs in
the

Typical Operating Characteristics

.

When the part is in transmit mode, the RXIN and RXIN
inputs provide back termination for the TXOUT and
TXOUT outputs so that a single IF filter can be connect­ed (Figure 5). With this technique, the matching network
can be adjusted so the input VSWR is less than 1.5:1 in
Rx mode, and the output VSWR is less than 2:1 in Tx
mode.

Receive IF Filter

The interstage 10.7MHz filter, located between the
MIXOUT pin and the LIMIN pin, is not shared. This filter
prevents the limiter from acting on any undesired sig­nals that are present at the mixer’s output, such as LO
feedthrough, out-of-band channel leakage, and other
mixer products. This filter is also set up to pass DC bias
voltage from the the V

REF

pin into the LIMIN and
MIXOUT pins through two filter-termination resistors
(330Ω—see the

Typical Operating Circuit

for more
information). If the filter can provide a DC shunt path,
such as a transformer-capacitor based filter or some L-C
filters, the two resistors can be combined into one par­allel, equivalent resistor (165Ω) to reduce component
count (Figure 5—inset).

______________________Layout Issues

A well-designed PC board is an essential part of an RF
circuit. For best performance, pay attention to power­supply issues, as well as the layout of the matching net­works and tank circuit.

Power-Supply Layout

For minimizing coupling between different sections of the
chip, the ideal power-supply layout is a star configura­tion, which has a heavily decoupled central VCCnode.
The VCCtraces branch out from this node, each going to
one VCCnode on the MAX2511. At the end of each of
these traces is a bypass capacitor that is good at the
RF frequency of interest. This arrangement provides
local decoupling at each VCCpin. At high frequency,
any signal leaking from a supply pin sees a relatively
high impedance (formed by the VCCtrace impedance)
to the central VCCnode, and an even higher imped­ance to any other supply pin.

Place the VREF decoupling capacitor (0.1µF typ) as
close to the MAX2511 as possible for best interstage fil­ter performance. Use a high-quality, low-ESR capacitor
for best results.

Matching Network Layout

The TXOUT, TXOUT port requires a bias network that
consists of two inductors to VCC(for differential drive)
and optionally a back-termination resistor for matching
to an external filter. The RXIN, RXIN port also needs an
impedance-matching network. Both networks should be
symmetrical and as close to the chip as possible. See
the

Typical Operating Circuit

for more details. If you use
a ground-plane PC board, cut out the ground plane
under the matching network components to reduce
parasitic capacitance.

Local-Oscillator Tank Layout

Oscillator-tank circuit layout is critical. Parasitic PC
board capacitance, as well as trace inductance, can
affect oscillation frequency. Keep the tank layout sym­metrical, tightly packed, and as close to the device as
possible. If a ground-plane PC board is used, the
ground plane should be cut out under the oscillator
components to reduce parasitic capacitance.

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

14 ______________________________________________________________________________________

Table 2. Recommended Values for L1

f

LO

(MHz)

200 to 300
300 to 400 12

L1 (µH)

18

400 to 500 8.2

FREQUENCY

(MHz)

100
200

SERIES

IMPEDANCE

(Ω)

395

274-j226
131-j186

79-j138

C (pF)

460 2.85

2.86

300 2.9320

58-j105400 2.9248

48-j82500 2.9188
43-j62600 2.9132

EQUIVALENT PARALLEL

IMPEDANCE

R (Ω)

Figure 4. Overdriving the On-Chip Oscillator

Figure 3. Oscillator Tank Schematic

Table 3. Rx Input Impedance

TANK

10k

C2

10k

P

TANK

TANK

C

P

C1L1C

R = 200Ω

C3

C2 = C3

10k

MINI CIRCUITS

TC4-1Ω

VCO VOLTAGE
FROM PLL

50Ω
SIGNAL SOURCE

TANK

ADJUST R FOR BEST RETURN LOSS AT SIGNAL SOURCE

MAX2511

Low-Voltage IF Transceiver

with Limiter and RSSI

______________________________________________________________________________________ 15

425MHz

BPF

MIXOUT

0.1µF

330Ω 330Ω

LIMIN

TWO-PORT FILTER

10.7 MHz BPF

C

MATCH

C

MATCH

L

MATCH

L

MATCH

R

OPT

V

CC

V

CC

RX

MIXER

RXIN

RXIN

TXIN

TXIN

10.7MHz
BPF

C

BLOCK

C

BLOCK

TXOUT

TXOUT

TX

MIXER

CONTROL

LIMITER

LIMOUT

LIMOUT

GC

ONE PORT FILTER

(LC OR TRANSFORMER-C)

165Ω

0.1µF

MIXOUT VREF LIMIN

MAX2511

VREF

Figure 5. Filter Sharing

MAX2511

Low-Voltage IF Transceiver
with Limiter and RSSI

16 ______________________________________________________________________________________

___________________________________________________Typical Operating Circuit

TXOUT TXIN

TXIN

LIMOUT

RXEN

TXEN

V

CC

GND

TANK

TANK

OSCOUT

V

CC

V

CC

V

CC

GND

VREFLIMIN CZ

CZ

LIMOUT

TXOUT

RXIN

RXIN

GND

RSSI

GC

GND

MIXOUT

24

13

14

18

17

7

6

9

8

V

CC

L

CHOKE

L

CHOKE

C

BLOCK

C

BLOCK

C

MATCH

C

MATCH

V

CC

V

CC

L

MATCH

Tx

OUTPUT

V

CC

Rx

INPUT

R*

D1

10kΩ

10kΩ

10kΩ

23

25

22

20

21

20

4

5

26

27

47nF47nF

0.01µF*

100pF

MAX2511

8.2nH 12pF

6.8 pF

6.8pF

16

15

47nF

1k1k

V

CC

INPUT

10.7MHz Tx

IF OUTPUT

CONTROL
LOGIC

VCO ADJUST
FROM PLL

47nF

10.7MHz Rx

0.1µF

0.1µF

0.1µF

0.1µF

12

TO PRESCALER

GAIN CONTROL VOLTAGE

RSSI OUTPUT

470pF

10

3

2281

0.1µF

330Ω

*

OPTIONAL

330Ω

11

V

CC

47nF

0.01µF

10.7MHz

BPF, Z0 = 330Ω

F

OSC

= 435.7MHz

D1 = ALPHA SMV1204-199

47nF