National Semiconductor LMX2531 Technical data

April 17, 2008

LMX2531
High Performance Frequency Synthesizer System with
Integrated VCO

LMX2531 High Performance Frequency Synthesizer System with Integrated VCO

General Description

The LMX2531 is a low power, high performance frequency
synthesizer system which includes a fully integrated delta­sigma PLL and VCO with fully integrated tank circuit. The third
and fourth poles are also integrated and also adjustable. Also
included are integrated ultra-low noise and high precision
LDOs for the PLL and VCO which give higher supply noise
immunity and also more consistent performance. When com­bined with a high quality reference oscillator, the LMX2531
generates very stable, low noise local oscillator signals for up
and down conversion in wireless communication devices.
The LMX2531 is a monolithic integrated circuit, fabricated in
an advanced BiCMOS process. There are several different
versions of this product in order to accomodate different fre­quency bands.

Device programming is facilitated using a three-wire
MICROWIRE Interface that can operate down to 1.8 volts.

Supply voltage range is 2.8 to 3.2 Volts. The LMX2531 is
available in a 36 pin 6x6x0.8 mm Lead-Free Leadless Lead­frame Package (LLP).

Target Applications

3G Cellular Base Stations (WCDMA, TD-

■

SCDMA,CDMA2000)
2G Cellular Base Stations (GSM/GPRS, EDGE,

■

CDMA1xRTT)
Wireless LAN

■

Broadband Wireless Access

■

Satellite Communications

■

Wireless Radio

■

Automotive

■

CATV Equipment

■

Instrumentation and Test Equipment

■

RFID Readers

■

Features

Multiple Frequency Options Available

■

See Selection Guide Below

—

Frequencies from: 553 MHz - 2790 MHz

—

PLL Features

■

Fractional-N Delta Sigma Modulator Order

—

programmable up to 4th order
FastLock/Cycle Slip Reduction with Timeout Counter

—

Partially integrated, adjustable Loop Filter

—

Very low phase noise and spurs

—

VCO Features

■

Integrated tank inductor

—

Low phase noise

—

Other Features

■

2.8 V to 3.2 V Operation

—

Low Power-Down Current

—

1.8V MICROWIRE Support

—

Package: 36 Lead LLP

—

Part Low Band High Band

LMX2531LQ1146E 553 - 592 MHz 1106 - 1184 MHz

LMX2531LQ1226E 592 - 634 MHz 1184 - 1268 MHz

LMX2531LQ1312E 634 - 680 MHz 1268 - 1360 MHz

LMX2531LQ1415E 680 - 735 MHz 1360 - 1470 MHz

LMX2531LQ1515E 725 - 790 MHz 1450 - 1580 MHz

LMX2531LQ1570E 765 - 818 MHz 1530 - 1636 MHz

LMX2531LQ1650E 795 - 850 MHz 1590 - 1700 MHz

LMX2531LQ1700E 831 - 885 MHz 1662 - 1770 MHz

LMX2531LQ1742 880 - 933 MHz 1760 - 1866 MHz

LMX2531LQ1778E 863 - 920 MHz 1726 - 1840 MHz

LMX2531LQ1910E 917 - 1014 MHz 1834 - 2028 MHz

LMX2531LQ2080E 952 - 1137 MHz 1904 - 2274 MHz

LMX2531LQ2265E 1089 - 1200 MHz 2178 - 2400 MHz

LMX2531LQ2570E 1168 - 1395 MHz 2336 - 2790 MHz

© 2008 National Semiconductor Corporation 201011 www.national.com

Functional Block Diagram

LMX2531

20101101

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Connection Diagrams

LMX2531

36-Pin LLP (LQ) Package, D Version

(LMX2531LQ1146E/1226E/1312E/1415E/1515E)

36-Pin LLP (LQ) Package, A Version

(All Other Versions)

20101104

20101102

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Pin Descriptions

Pin # Pin Name I/O Description

LMX2531

1 VccDIG -

3 GND - Ground

2,4,5,7,

12, 13,

29, 35

6 VregBUF - Internally regulated voltage for the VCO buffer circuitry. Connect to ground with a capacitor.

8 DATA I

9 CLK I

10 LE I

11 CE I

14, 15 NC - No Connect. Do NOT ground.

16 VccVCO -

17 VregVCO -

18 VrefVCO -

19 GND - Ground for the VCO circuitry.

20 GND - Ground for the VCO Output Buffer circuitry.

21 Fout O Buffered RF Output for the VCO.

22 VccBUF -

23 Vtune I

24 CPout O Charge pump output for PLL. For connection to Vtune through an external passive loop filter.

25 FLout O An open drain NMOS output which is used for FastLock or a general purpose output.

26 VregPLL1 -

27 VccPLL -

28 VregPLL2 -

30 Ftest/LD O Multiplexed CMOS output. Typically used to monitor PLL lock condition.

31 OSCin I Oscillator input.

32 OSCin* I

33 Test O This pin is for test purposes and should be grounded for normal operation.

34 GND - Ground

36 VregDIG - Internally regulated voltage for LDO digital circuitry.

NC - No Connect.

Power Supply for digital LDO circuitry. Input may range from 2.8 - 3.2 V. Bypass capacitors should be
placed as close as possible to this pin and ground.

MICROWIRE serial data input. High impedance CMOS input. This pin must not exceed 2.75V. Data is
clocked in MSB first. The last bits clocked in form the control or register select bits.

MICROWIRE clock input. High impedance CMOS input. This pin must not exceed 2.75V. Data is clocked
into the shift register on the rising edge.

MICROWIRE Latch Enable input. High impedance CMOS input. This pin must not exceed 2.75V. Data
stored in the shift register is loaded into the selected latch register when LE goes HIGH.

Chip Enable Input. High impedance CMOS input. This pin must not exceed 2.75V. When CE is brought
high the LMX2531 is powered up corresponding to the internal power control bits. Although the part can
be programmed when powered down, it is still necessary to reprogram the R0 register to get the part to
re-lock.

Power Supply for VCO regulator circuitry. Input may range from 2.8 - 3.2 V. Bypass capacitors should
be placed as close as possible to this pin and ground.

Internally regulated voltage for VCO circuitry. Not intended to drive an external load. Connect to ground
with a capacitor and some series resistance.

Internal reference voltage for VCO LDO. Not intended to drive an external load. Connect to ground with
a capacitor.

Power Supply for the VCO Buffer circuitry. Input may range from 2.8 - 3.2 V. Bypass capacitors should
be placed as close as possible to this pin and ground.

Tuning voltage input for the VCO. For connection to the CPout Pin through an external passive loop
filter.

Internally regulated voltage for PLL charge pump. Not intended to drive an external load. Connect to
ground with a capacitor.

Power Supply for the PLL. Input may range from 2.8 - 3.2 V. Bypass capacitors should be placed as
close as possible to this pin and ground.

Internally regulated voltage for RF digital circuitry. Not intended to drive an external load. Connect to
ground with a capacitor.

Oscillator complimentary input. When a single ended source is used, then a bypass capacitor should be
placed as close as possible to this pin and be connected to ground.

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Connection Diagram

LMX2531

Pin(s) Application Information

VccDIG

VccVCO

VccBUF

VccPLL

VregDIG There is not really any reason to use any other values than the recommended values.

VrefVCO

VregVCO

VregPLL1
VregPLL2

CLK

DATA

Ftest/LD It is an option to use the lock detect information from this pin.

Because the LMX2531 contains internal regulators, the power supply noise rejection is very good and capacitors at
this pin are not critical. If desired, capacitors can be placed at these pins to improve the noise rejection, although may
not be necessary. Recommended values are from open to 1 μF.

If the VregVCO capacitor is changed, it is recommended to keep this capacitor between 1/100 and 1/1000 of the value
of the VregVCO capacitor.

Because this pin is the output of a regulator, there are stability concerns if there is not sufficient series resistance. For
ceramic capacitors, the ESR (Equivalent Series Resistance) is too low, and it is recommended that a series resistance
of 1 - 3.3Ω is necessary. If there is insufficient ESR, then there may be degradation in the phase noise, especially in
the 100 - 300 kHz offset. Recommended values are from 1 μF to 10 μF.

The choice of the capacitor value at this pin involves a trade-off between integer spurs and phase noise in the 100 ­300 kHz offset range. Values in the range of 100 to 470 nF are typical. Some series resistance of about 220 mΩ is
also helpful in improving the phase noise in the 100 - 300 kHz range. If too much series resistance is at this pin, the
spurs at far offsets will be severely degraded. If there is too little, the phase noise may be degraded.

Since the maximum voltage on these pins is less than the minimum Vcc voltage, level shifting may be required if the
output voltage of the microcontroller is too high. This can be accomplished with a resistive divider.

LE

As with the CLK, DATA, and LE pins, level shifting may be required if the output voltage of the microcontroller is too

CE

high. A resistive divider or a series diode are two ways to accomplish this. The diode has the advantage that no current
flows through it when the chip is powered down.

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Pin(s) Application Information

LMX2531

Fout

CPout

Vtune

R2pLF

OSCin This is the crystal oscillator input pin. It needs to be AC coupled.

OSCin* If the device is being driven single-ended, this pin needs to be shunted to ground with a capacitor.

This is the high frequency output. This needs to be AC coupled, and matching may also be required. The value of the
DC blocking capacitor may be changed, depending on the output frequency.

In most cases, it is sufficient to short these together. C1_LF, C2_LF, and R2_LF are used in conjunction with the
internal loop filter to make a fourth order loop filter. However, the user always has the option of adding additional
poles.

This is the fastlock resistor, which can be useful in many cases, since the spurs are often better with low charge pump
currents, and the internal loop filter can be adjusted during fastlock.

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors
for availability and specifications.

Parameter Symbol Ratings Units

V

Power Supply Voltage

Storage Temperature

Range

Lead Temperature (solder 4 sec.)

(VccDIG, VccVCO,

CC

VccBUF, VccPLL)

All other pins (Except

Ground)

T

STG

T

L

-0.3 to 3.5
V

-0.3 to 3.0

-65 to 150 °C

+ 260 °C

Recommended Operating Conditions

Parameter Symbol Min Typ Max Units

Power Supply Voltage

(VccDig, VccVCO, VccBUF)

Serial Interface and Power Control

Voltage

Ambient Temperature

(Note 4)

Vcc 2.8 3.0 3.2 V

V

i

T

A

0 2.75 V

-40 +85 °C

LMX2531

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Recommended Operating Conditions indicate conditions for

which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical
Characteristics. The guaranteed specifications apply only to the test conditions listed.

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Electrical Characteristics (V

= 3.0 V, -40°C ≤ TA ≤ 85 °C; except as specified.)

CC

Symbol Parameter Conditions Min Typ Max Units

LMX2531

Power Supply Current

Current Consumption

Divider Disabled 34 41

(All Parts Except

I

CC

ICCPD

LMX2531LQ2265E,
LMX2531LQ2570E)

Power Supply Current

(LMX2351LQ2265E,

LMX2531LQ2570E)

Power Down Current CE = 0 V, Part Initialized 7 µA

Divider Enabled 37 46

Divider Disabled 38 44

Divider Enabled 41 49

Oscillator

IIHOSC

IILOSC

f

OSCin

v

OSCin

Oscillator Input High Current

Oscillator Input Low Current

Frequency Range 5 80 MHz

Oscillator Sensitivity 0.5 2.0 Vpp

VIH = 2.75 V

V

= 0

IL

100 µA

-100 µA

PLL

f

PD

Phase Detector Frequency 32 MHz

ICP = 0 90 µA

I

CPout

Charge Pump

Output Current Magnitude

ICP = 1 180 µA

ICP = 3 360 µA

ICP = 15 1440 µA

I

CPout

I

CPout

I

CPout

I

CPout

LN(f)

TRI

MM

CP TRI-STATE Current

Charge Pump

Sink vs. Source Mismatch

Charge Pump

V

Current vs. CP Voltage

Variation

CP Current vs. Temperature

T

Variation

Normalized PLL 1/f Noise

LN

PLL_flicker

(Note 2)

Normalized PLL Noise Floor

LN

PLL_flat

(Note 3)

(10 kHz)

0.4 V < V

V

CPout

0.4 V < V

V

CPout

ICP = 1X Charge Pump Gain

ICP = 16X Charge Pump Gain -104

ICP = 1X Charge Pump Gain

ICP = 16X Charge Pump Gain -212

CPout

= 1.2 V

TA = 25°C

CPout

TA = 25°C

= 1.2 V

< 2.0 V

< 2.0 V

2 10 nA

2 8 %

4 %

8 %

-94

-202

dBc/Hz

dBc/Hz

mA

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Symbol Parameter Conditions Min Typ Max Units

VCO Frequencies

LMX2531LQ1146E 1106 1184

LMX2531LQ1226E 1184 1268

LMX2531LQ1312E 1268 1360

LMX2531LQ1415E 1360 1470

LMX2531LQ1515E 1450 1580

Operating Frequency Range

(All options have a frequency

f

divider, this applies before the

Fout

divider. The frequency after the
divider is half of what is shown)

LMX2531LQ1570E 1530 1636

LMX2531LQ1650E 1590 1700

LMX2531LQ1700E 1662 1770

LMX2531LQ1742 1760 1866

MHz

LMX2531LQ1778E 1726 1840

LMX2531LQ1910E 1834 2028

LMX2531LQ2080E 1904 2274

LMX2531LQ2265E 2178 2400

LMX2531LQ2570E 2336 2790

LMX2531

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Symbol Parameter Conditions Min Typ Max Units

Other VCO Specifications

LMX2531

LMX2531LQ1742 65

LMX2531LQ1570E, LMX2531LQ1650E,

ΔT

Maximum Allowable

Temperature Drift for

CL

Continuous Lock

(Note 4)

LMX2531LQ1146E, LMX2531LQ1226E,
LMX2531LQ1312E, LMX2531LQ1415E,

LMX2531LQ1515E

LMX2531LQ1700E, LMX2531LQ1778E,
LMX2531LQ1910E, LMX2531LQ2080E,

90

125

LMX2531LQ2265E,LMX2531LQ2570E

LMX2531LQ1146E 1 4.0 7

LMX2531LQ1226E 1 3.5 7

LMX2531LQ1312E 1 3.5 7

LMX2531LQ1415E 0 3.0 6

LMX2531LQ1515E -1 2.5 5

LMX2531LQ1570E 2 4.5 8

Divider Disabled

LMX2531LQ1650E 2 4.5 8

LMX2531LQ1700E 1 3.5 7

LMX2531LQ1742 1 3.5 7

LMX2531LQ1778E 1 3.5 7

LMX2531LQ1910E 1 3.5 7

LMX2531LQ2080E 1 3.5 7

LMX2531LQ2265E 1 3.5 7

Output Power to a 50 Ω Load

p

Fout

(Applies across entire tuning

range.)

LMX2531LQ2570E 0 3.0 6

LMX2531LQ1146E -1 2.0 5

LMX2531LQ1226E -1 2.0 5

LMX2531LQ1312E -1 1.5 4

LMX2531LQ1415E -2 0.5 3

LMX2531LQ1515E -2 0.5 3

LMX2531LQ1570E 1 3.0 6

Divider Enabled

LMX2531LQ1650E 1 3.0 6

LMX2531LQ1700E 1 3.0 6

LMX2531LQ1742 1 3.0 6

LMX2531LQ1778E 1 3.0 6

LMX2531LQ1910E 1 3.0 6

LMX2531LQ2080E 0 2.5 5

LMX2531LQ2265E 0 2.5 5

LMX2531LQ2570E -1 1.5 4

°C

dBm

dBm

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Symbol Parameter Conditions Min Typ Max Units

LMX2531LQ1146E

2.5

-5.5

LMX2531LQ1226E 3-6

LMX2531LQ1312E 3-6

3.5

-6.5

MHz/V

K

Fine Tuning Sensitivity

(When a range is displayed in
the typical column, indicates the
lower sensitivity is typical at the

Vtune

lower end of the tuning range,
and the higher tuning sensitivity
is typical at the higher end of the

tuning range.)

LMX2531LQ1415E

LMX2531LQ1515E 4-7

LMX2531LQ1570E 4-7

LMX2531LQ1650E 4-7

LMX2531LQ1700E 6-10

LMX2531LQ1742 4-7

LMX2531LQ1778E 6-10

LMX2531LQ1910E 8-14

LMX2531LQ2080E 9-20

LMX2531LQ2265E 10-16

LMX2531LQ2570E 10-23

LMX2531LQ1146E

HS

Harmonic Suppression

(Applies Across Entire Tuning

Fout

Range)

2nd Harmonic

50 Ω Load

3rd Harmonic

50 Ω Load

Divider

Disabled

Divider

Enabled

Divider

Disabled

Divider

Enabled

/1226E/1312E
/1415E/1515E

All Other Options -30 -25

LMX2531LQ1146E

/1226E/1312E
/1415E/1515E

All Other Options -20 -15

LMX2531LQ1146E

/1226E/1312E

All Other Options -40 -35

LMX2531LQ1146E

/1226E/1312E
/1570E/1650E

-35 -25

-30 -20

dBc

-35 -30

-20 -15

All Other Options -25 -20

PUSH

PULL

Z

Fout

Fout

Fout

Frequency Pushing

Frequency Pulling VSWR=2:1, Open Loop ±600 kHz

Output Impedance 50

Creg = 0.1uF, VDD ± 100mV, Open Loop

300 kHz/V

Ω

LMX2531

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