Datasheet LMX2502, LMX2512 Datasheet (National Semiconductor)

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LMX2502/LMX2512

LMX2502/LMX2512 Frequency Synthesizer System with Integrated VCO

June 2003

PLLatinum

™

Frequency Synthesizer System with

Integrated VCO

General Description

LMX2502 and LMX2512 are highly integrated, high perfor­mance, low power frequency synthesizer systems optimized
for Korean PCS and Korean Cellular CDMA (1xRTT, IS-95)
mobile handsets. Using a proprietary digital phase locked
loop technique, LMX2502 and LMX2512 generate very
stable, low noise local oscillator signals for up and down
conversion in wireless communications devices.

LMX2502 and LMX2512 include a voltage controlled oscil­lator (VCO), a loop filter, and a fractional-N RF PLL based on
a delta sigma modulator. In concert these blocks form a
closed loop RF synthesizer system. LMX2502 supports the
Korean PCS band and LMX2512 supports the Korean Cel­lular band.

LMX2502 and LMX2512 include an Integer-N IF PLL also.
For more flexible loop filter designs, the IF PLL includes a
4-level programmable charge pump. Together with an exter­nal VCO and loop filter, LMX2502 and LMX2512 make a
complete closed loop IF synthesizer system.

Serial data is transferred to the device via a three-wire
MICROWIRE interface (DATA, LE, CLK).

Operating supply voltage ranges from 2.7 V to 3.3 V.
LMX2502 and LMX2512 feature low current consumption:
17 mA at 2.8 V.

LMX2502 and LMX2512 are available in a 28-pin leadless
leadframe package (LLP).

Features

n Small Size

5.0 mm X 5.0 mm X 0.75 mm 28-Pin LLP Package

n RF Synthesizer System

Integrated RF VCO
Integrated Loop Filter
Low Spurious, Low Phase Noise Fractional-N RF PLL
Based on 11-Bit Delta Sigma Modulator
10 kHz Frequency Resolution

n IF Synthesizer System

Integer-N IF PLL
Programmable Charge Pump Current Levels
Programmable Frequency

n Supports Various Reference Frequencies

19.20/19.68 MHz

n Fast Lock Time: 500 µs
n Low Current Consumption

17 mA at 2.8 V

n 2.7 V to 3.3 V Operation
n Digital Filtered Lock Detect Output
n Hardware and Software Power Down Control

Applications

n Korean PCS CDMA Systems
n Korean Cellular CDMA Systems

Functional Block Diagram

20068001

PLLatinum™is a trademark of National Semiconductor Corporation.

© 2003 National Semiconductor Corporation DS200680 www.national.com

Connection Diagram

LMX2502/LMX2512

28-Pin LLP (LQ) Package

NOTE: Analog ground connected through exposed die attached pad.

Pin Descriptions

Pin Number Name I/O Description

1 CPout O IF PLL charge pump output

2 NC – Do not connect to any node on the printed circuit board.

3 NC – Do not connect to any node on the printed circuit board.

4V

5 LE I MICROWIRE Latch Enable

6 CLK I MICROWIRE Clock

7 DATA I MICROWIRE Data

8V

9 NC – Do not connect to any node on the printed circuit board.

10 NC – Do not connect to any node on the printed circuit board.

11 NC – Do not connect to any node on the printed circuit board.

12 NC – Do not connect to any node on the printed circuit board.

13 V

14 V

15 RFout O Buffered VCO output

16 V

17 V

18 V

19 LD O Lock Detect

20 CE I Chip Enable control pin

21 GND – Ground for digital circuitry

22 OSCin I Reference frequency input

23 V

24 GND – Ground for digital circuitry

25 V

26 Fin I IF buffer/prescaler input

27 V

28 NC – Do not connect to any node on the printed circuit board.

DD

DD

DD

DD

CC

CC

CC

CC

CC

CC

20068002

– Supply voltage for IF analog circuitry

– Supply voltage for VCO

– Supply voltage for VCO

– Supply voltage for VCO output buffer

– Supply voltage for RF prescaler

– Supply voltage for charge pump

– Supply voltage for RF digital circuitry

– Supply voltage for reference input buffer

– Supply voltage for IF digital circuitry

– Supply voltage for IF buffer/prescaler

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Ordering Information

LMX2502/LMX2512

Part Number RF Min.

(MHz)

LMX2502LQX1635 1619.62 1649.62

LMX2502LQ1635 1619.62 1649.62

LMX2512LQX0967 954.42 979.35

LMX2512LQ0967 954.42 979.35

LMX2512LQX1065 1052.64 1077.57

LMX2512LQ1065 1052.64 1077.57

Part Number Description

RF Max.
(MHz)

RF Center
(MHz)

~

1635 440.76 25021635 4500 units on

~

1635 440.76 25021635 1000 units on

~

967 170.76 25120967 4500 units on

~

967 170.76 25120967 1000 units on

~

1065 367.20 25121065 4500 units on

~

1065 367.20 25121065 1000 units on

IF
(MHz)

Package
Marking

Supplied As

tape and reel

tape and reel

tape and reel

tape and reel

tape and reel

tape and reel

20068003

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Absolute Maximum Ratings (Notes 1,

2, 3)

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

Parameter Symbol Ratings Units

LMX2502/LMX2512

Supply Voltage V

Voltage on any pin
to GND

Storage Temperature
Range

CC,VDD

V

I

T

STG

-0.3 to 3.6 V

-0.3toVCC+0.3 V

-0.3toV

DD

-65 to 150 ˚C

+0.3 V

Recommended Operating
Conditions

Parameter Symbol Min Typ Max Units

Ambient Temperature T

Supply Voltage (to GND) V

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, refer to the Electrical Characteristics section. The guaranteed specifi­cations apply only for the conditions listed.

Note 2: This device is a high performance RF integrated circuit with an ESD

<

rating

2 kV and is ESD sensitive. Handling and assembly of this device

should be done at ESD protected work stations.

Note 3: GND=0V.

A

CC,VDD

-30 25 85 ˚C

2.7 3.3 V

Electrical Characteristics (V

CC=VDD

= 2.8 V, TA= 25 ˚C; unless otherwise noted)

Symbol Parameter Condition Min Typ Max Units

I

PARAMETERS

CC

I

CC+IDD

(I

+

CC

I

DD)RF

I

PD

Total Supply Current OB_CRL [1:0] = 00 17 19 mA

RF PLL Total Supply Current OB_CRL [1:0] = 00 16 18 mA

Power Down Current (Note 4) CE = LOW or

20 µA
RF_EN = 0
IF_EN = 0

REFERENCE OSCILLATOR PARAMETERS

f

OSCin

V

OSCin

Reference Oscillator Input Frequency
(Note 5)

Reference Oscillator Input Sensitivity 0.2 V

19.20 MHz and 19.68
MHz are supported

19.20 19.68 MHz

CC

Vp-p

RF VCO

f

RFout

Frequency Range
(Note 6)

LMX2502LQ1635 RF VCO 1619.62 1649.62 MHz

LMX2512LQ0967 954.42 979.35 MHz

LMX2512LQ1065 1052.64 1077.57 MHz

P

RFout

RF Output Power OB_CRL [1:0] = 11 -2 1 4 dBm

OB_CRL [1:0] = 10 -5 -2 1 dBm

OB_CRL [1:0] = 01 -7 -4 -1 dBm

OB_CRL [1:0] = 00 -9 -6 -3 dBm

Lock Time
(Note 7)

LMX2502LQ1635 30 MHz Band for RF

PLL

LMX2512LQ0967 25 MHz Band for RF

500 800 µs

500 800 µs

PLL

LMX2512LQ1065 25 MHz Band for RF

500 800 µs

PLL

Reference Spurs -75 dBc

RMS Phase Error RF PLL in all band 1.3 degrees

L(f)

RFout

Phase Noise LMX2502LQ1635

LMX2512LQ0967

LMX2512LQ1065

@

100 kHz offset -113 -112 dBc/Hz

@

1.25 MHz offset -138 -136 dBc/Hz

@

100 kHz offset -117 -115 dBc/Hz

@

900 kHz offset -139 -138 dBc/Hz

@

100 kHz offset -117 -115 dBc/Hz

@

900 kHz offset -139 -138 dBc/Hz

2nd Harmonic Suppression -25 dBc

3rd Harmonic Suppression -20 dBc

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LMX2502/LMX2512

Electrical Characteristics (V

CC=VDD

= 2.8 V, TA= 25 ˚C; unless otherwise noted) (Continued)

Symbol Parameter Condition Min Typ Max Units

IF PLL

f

Fin

Operating Frequency
(Note 8)

LMX2502LQ1635 IF_FREQ [1:0] = 10,

Default Value

LMX2512LQ0967 IF_FREQ [1:0] = 00,

440.76 MHz

170.76 MHz

Default Value

LMX2512LQ1065 IF_FREQ [1:0] = 01,

367.20 MHz

Default Value

P

f

ΦIF

I

CPout

Fin

IF Input Sensitivity -10 0 dBm

Phase Detector Frequency 120 kHz

Charge Pump Current IF_CUR [1:0] = 00 100 µA

IF_CUR [1:0] = 01 200 µA

IF_CUR [1:0] = 10 300 µA

IF_CUR [1:0] = 11 800 µA

DIGITAL INTERFACE (DATA, CLK, LE, LD, CE)

V

IH

V

IL

I

IH

I

IL

High-Level Input Voltage 0.8 V

0.8 V

DD

CC

Low-Level Input Voltage 0 0.2 V

0 0.2 V

V

DD

V

CC

DD

CC

High-Level Input Current -10 10 µA

Low-Level Input Current -10 10 µA

V

V

V

V

Input Capacitance 3 pF

V

OH

V

OL

High-Level Output Voltage 0.9 V

0.9 V

DD

CC

Low-Level Output Voltage 0.1 V

0.1 V

V

V

DD

CC

V

V

Output Capacitance 5pF

MICROWIRE INTERFACE TIMING

t

CS

t

CH

t

CWH

t

CWL

t

ES

t

EW

Note 4: In power down mode, set DATA, CLK, and LE pins to 0 V (GND).

Note 5: The reference frequency must also be programmed using the OSC_FREQ control bit. For other reference frequencies, please contact National

Semiconductor.

Note 6: For other frequency ranges, please contact National Semiconductor.

Note 7: Lock time is defined as the time difference between the beginning of the frequency transition and the point at which the frequency remains within +/- 1 kHz

of the final frequency.

Note 8: Frequencies other that the default value can be programmed using Words R4 and R5. See Programming Description for details.

Data to Clock Set Up Time 50 - - ns

Data to Clock Hold Time 10 - - ns

Clock Pulse Width HIGH 50 - - ns

Clock Pulse Width LOW 50 - - ns

Clock to Latch Enable Set Up Time 50 - - ns

Latch Enable Pulse Width 50 - - ns

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Microwire Interface Timing Diagram

LMX2502/LMX2512

20068004

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Functional Description

GENERAL DESCRIPTION

LMX2502/12 is a highly integrated frequency synthesizer
system that generates LO signals for PCS and Cellular
CDMA applications. These devices include all the functional
blocks of a PLL, RF VCO, prescaler, RF phase detector, and
loop filter. The need for external components is limited to a
few passive elements for matching the output impedance
and bypass elements for power line stabilization.

In addition to the RF circuitry, the IC also includes IF fre­quency dividers, and an IF phase detector to complete the IF
synthesis with the external VCO and the loop filter. Table 1
summarizes the counter values used to generate the default
IF frequencies.

Using a low spurious fractional-N synthesizer based on a
delta sigma modulator, the circuit can support 10 kHz chan­nel spacing for PCS and Cellular CDMA systems.

The fractional-N synthesizer enables faster lock time, which
reduces power consumption and system set-up time. Addi­tionally, the loop filter occupies a smaller area as opposed to
the integer-N architecture. This allows the loop filter to be
embedded into the circuit, minimizing the external noise
coupling and total form factor. The delta sigma architecture
delivers very low spurious, which can be a significant prob­lem for other PLL solutions.

The circuit also supports commonly used reference frequen­cies of 19.20 MHz and 19.68 MHz.

FREQUENCY GENERATION

RF-PLL Section

The divide ratio can be calculated using the following equa­tion:

LMX2502 – PCS CDMA:

= {8 x RF_B + RF_A + (RF_FN / f

f

VCO

where (RF_A<RF_B)
LMX2512 – Cellular CDMA:

= {6 x RF_B + RF_A + (RF_FN / f

f

VCO

where (RF_A<RF_B)
where
f

: Output frequency of voltage controlled oscillator (VCO)

VCO

RF_B: Preset divide ratio of binary 4-bit programmable
counter (2 ≤ RF_B ≤ 15)

RF_A: Preset divide ratio of binary 3-bit swallow counter (0 ≤
RF_A ≤ 7 for LMX2502 or 0 ≤ RF_A ≤ 5 for LMX2512)

RF_FN: Preset numerator of binary 11-bit modulus counter

<

(0 ≤ RF_FN
1968 for f

f

: Reference oscillator frequency

OSC

1920 for f

= 19.68 MHz)

OSC

= 19.20 MHz or 0 ≤ RF_FN

OSC

IF-PLL Section

f

= {16 x IF_B + IF_A} x f

VCO

/ IF_R where (IF_A<IF_B)

OSC

where

: Output frequency of the voltage controlled oscillator

f

VCO

(VCO)
IF_B: Preset divide ratio of the binary 9-bit programmable

counter (1 ≤ IF_B ≤ 511)

)x104}xf

OSC

)x104}xf

OSC

OSC

OSC

LMX2502/LMX2512

IF_A: Preset divide ratio of the binary 4-bit swallow counter
(0 ≤ IF_A ≤ 15)

f

: Reference oscillator frequency

OSC

IF_R: Preset divide ratio of the binary 9-bit programmable
reference counter (2 ≤ IF_R ≤ 511)

From the above equation, the LMX2502/12 generates the
fixed IF frequencies as summarized in Table 1.

TABLE 1. IF Frequencies

Device Type F

(MHz)

LMX2502LQ1635 440.76 229 9 120

LMX2512LQ0967 170.67 88 15 120

LMX2512LQ1065 367.20 191 4 120

VCO FREQUENCY TUNING

The center frequency of the RF VCO is determined by the
resonant frequency of the tank circuit. This tank circuit is
implemented on-chip and requires no external inductor. The
LMX2502/12 actively tunes the tank circuit to the required
frequency with the built-in tracking algorithm.

BANDWIDTH CONTROL AND FREQUENCY LOCK

During the frequency acquisition period, the loop bandwidth
is significantly extended to achieve frequency lock. Once
frequency lock occurs, the PLL will return to a steady state
condition with the loop bandwidth set to its nominal value.
The transition between acquisition and lock modes occurs
seamlessly and extremely fast, thereby, meeting the strin­gent requirements associated with lock time and phase
noise. Several controls (BW_DUR, BW_CRL, and BW_EN)
are used to optimize the lock time performance.

SPURIOUS REDUCTION

To improve the spurious performance of the device one of
two types of spurious reduction schemes can be selected:

A continuous optimization scheme, which tracks the en-

•

vironmental and voltage variations, giving the best spuri­ous performance over changing conditions

A one time optimization scheme, which sets the internal

•

compensation values only when the PLL goes into a
locked state.

The spurious reduction can also be disabled, but it is recom­mended that the continuous optimization mode be used for
normal operation.

<

POWER DOWN MODE

The LMX2502 and LMX2512 include a power down mode to
reduce the power consumption. The LMX2502/12 enters into
the power down mode either by taking the CE pin LOW or by
setting the power down bits in Register R1. Table 2 summa­rizes the power down function. If CE is set LOW, the circuit is
powered down regardless of the register values. When CE is
HIGH, the IF and RF circuitry are individually powered down
by setting the register bits.

VCO

IF_B IF_A f

OSC

(kHz)

/IF_R

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Functional Description (Continued)

TABLE 2. Power Down Configuration

CE Pin RF_EN IF_EN RF Circuitry IF Circuitry

0 X X OFF OFF

1 0 0 OFF OFF

LMX2502/LMX2512

1 0 1 OFF ON

1 1 0 ON OFF

111 ON ON

X = Don’t care.

LOCK DETECT

The LD output can be used to indicate the lock status of the
RF PLL. Bit 21 in Register R0 determines the signal that
appears on the LD pin. When the RF PLL is not locked, the

LD pin remains LOW. After obtaining phase lock, the LD pin
will have a logical HIGH level. The output can also be
programmed to be ground at all times.

TABLE 3. Lock Detect Modes

LD Bit Mode

0 Disable (GND)

1 Enable

TABLE 4. Lock Detect Logic

RF PLL Section LD Output

Locked HIGH

Not Locked LOW

FIGURE 1. Lock Detect Timing Diagram Waveform (Notes 9, 10, 11, 12, 13)

Note 9: LD output becomes LOW when the phase error is larger than tW2.

Note 10: LD output becomes HIGH when the phase error is less than t

four or more consecutive cycles.

Note 11: Phase Error is measured on leading edge. Only errors greater than
t

and tW2are labeled.

W1

W1

20068005

Note 12: t

for

Note 13: The lock detect comparison occurs with every 64
f

.

N

and tW2are equal to 10 ns.

W1

th

cycle of fRand

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Functional Description (Continued)

LMX2502/LMX2512

FIGURE 2. Lock Detect Flow Diagram

MICROWIRE INTERFACE

The programmable register set is accessed via the
MICROWIRE serial interface. The interface comprises three
signal pins: CLK, DATA, and LE (Latch Enable). Serial data
(DATA) is clocked into the 24-bit shift register on the rising

20068006

edge of the clock (CLK). The last bits decode the internal
control register address. When the latch enable (LE) transi­tions from LOW to HIGH, data stored in the shift registers is
loaded into the corresponding control register.

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Programming Description

GENERAL PROGRAMMING INFORMATION

The serial interface has a 24-bit shift register to store the incoming data bits temporarily. The incoming data is loaded into the shift
register from MSB to LSB. The data is shifted at the rising edge of the clock signal. When the latch enable signal transitions from
LOW to HIGH, the data stored in the shift register is transferred to the proper register depending on the address bit settings. The
selection of the particular register is determined by the address bits equal to the binary representation of the number of the control

LMX2502/LMX2512

register.
At initial start-up, the MICROWIRE loading requires 4 default words (registers R3, loaded first, to R0, loaded last). After the device

has been initially programmed, the RF VCO frequency can be changed using a single register (R0). If an IF frequency other than
the default value for the device is desired the SPI_DEF bit should be set to 0, the desired values for IF_A, IF_B, and IF_R entered
and words R6 to R0 should be sent.

The control register content map describes how the bits within each control register are allocated to the specific control functions.

COMPLETE REGISTER MAP

MSB SHIFT REGISTER BIT LOCATION LSB

Register

R0
(Default)

R1
(Default)

R2
(Default)

R3
(Default)

R4 0 0 0 1 0 0 0 IF_A

R5 0 0 1 10 00010 IF_R

R6 1 0 0 00 0000000 0 00000011 1 11

NOTE: Bold numbers represent the address bits.

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

SPI_

RF_

DEF

SEL

IF_
FREQ
[1:0]

IF_
CUR[1:0]

BW_
DUR
[1:0]

RF_LD0 RF_B

[3:0]

OSC_
FREQ

0 01 0011101 1 01010001 0 10

BW_
CRL
[1:0]

10 000000SPUR_

BW_EN1011110 1 000110VCO_

RF_A
[2:0]

[3:0]

RDT
[1:0]

RF_FN

[10:0]

0 0 1 0 1 OB_

CRL
[1:0]

IF_B

[8:0]

[8:0]

00

RF_ENIF_EN01

011

CUR
[1:0]

0111

01 1 11

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Programming Description (Continued)

R0 REGISTER

The R0 register address bits (R0 [1:0]) are “00”.
The SPI_DEF bit selects between using the default IF counter values and user programmable values. The use of the default

counter values requires that only words R0 to R3 (registers R3, loaded first, to R0, loaded last) be sent after initial power up.
The RF_LD bit activates the lock detect output of the LD pin (pin 19). The lock detect mode shows the lock status of the RF PLL.

The waveform of the lock detect mode is shown in Figure 1,intheFunctional Description section on LOCK DETECT.
The RF N counter consists of the 4-bit programmable counter (RF_B counter), the 3-bit swallow counter (RF_A counter) and the

11-bit delta sigma modulator (RF_FN counter). The equations for calculating the counter values are presented below.

R0 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 22 21 2019181716151413121110987654321 0

Data Field Address

Register

R0
(Default)

SPI_

RF_

RF_LD0 RF_B

DEF

SEL

Name Functions

SPI_DEF Default Register Selection

RF_SEL RF VCO Selection

RF_LD RF Lock Detect

RF_B [3:0] RF_B Counter

RF_A [2:0] RF_A Counter

RF_FN [10:0] RF Fractional Numerator Counter

[3:0]

RF_A
[2:0]

0 = OFF (Use values set in R0 to R6)
1 = ON (Use default values set in R0 to R3)

0 = LMX2512
1 = LMX2502

0 = Hard zero (GND)
1 = Lock detect

4-bit programmable counter
2 ≤ RF_B ≤ 15

3-bit swallow counter
0 ≤ RF_A ≤ 7 for LMX2502
0 ≤ RF_A ≤ 5 for LMX2512

11-bit programmable counter

<

0 ≤ RF_FN
0 ≤ RF_FN

1920 for f

<

1968 for f

RF_FN

OSC

OSC

[10:0]

= 19.20 MHz
= 19.68 MHz

Field

00

LMX2502/LMX2512

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Programming Description (Continued)

RF N Counter Setting:

Counter Name Symbol Function

Modulus Counter RF_FN RF N Divider

Programmable

LMX2502/LMX2512

Counter

RF_B

Swallow Counter RF_A

Pulse Swallow Function:

= {Prescaler x RF_B + RF_A + (RF_FN / f

f

VCO

)x104}xf

OSC

where
f

: Output frequency of voltage controlled oscillator (VCO)

VCO

Prescaler Values:

Device Type RF Prescaler

LMX2502 8

LMX2512 6

RF_B: Preset divide ratio of binary 4-bit programmable counter (2 ≤ RF_B ≤ 15)
RF_A: Preset divide ratio of binary 3-bit swallow counter (0 ≤ RF_A ≤ 7 for LMX2502, 0 ≤ RF_A ≤ 5 for LMX2512)
RF_FN: Preset numerator of binary 11-bit modulus counter (0 ≤ RF_FN

= 19.68 MHz).

: Reference oscillator frequency

f

OSC

NOTE: For the use of reference frequencies other than those specified, please contact National Semiconductor.

N = Prescaler x RF_B + RF_A + (RF_FN / f

where (RF_A<RF_B)

OSC

<

1920 for f

= 19.20 MHz; 0 ≤ RF_FN<1968 for f

OSC

OSC

)x10

4

OSC

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Programming Description (Continued)

R1 REGISTER

The R1 register address bits (R1 [1:0]) are “01”.
The IF_FREQ bits selects the default IF frequency applicable to the specific CDMA system. For the LMX2502 the default IF

frequency is 440.76 MHz, and for the LMX2512 the default IF frequencies are 367.20 MHz and 170.76 MHz, depending on
variant.

Reference Frequency Selection bit (OSC_FREQ) selects either 19.20 MHz or 19.68 MHz for the reference oscillator frequency.
The internal spurious reduction scheme is controlled by the SPUR_RDT [1:0] bits. There are two different spur reduction

schemes: a continuous tracking mode and a single optimization mode. The continuous tracking mode will adjust for variations in
voltage and temperature. The single optimization mode fixes the internal compensation parameters only when the PLL goes into
the locked state. The spur reduction can also be disabled, but it is recommended that the continuous mode be used for normal
operation.

The OB_CRL [1:0] bits determine the power level of the RF output buffer. The power level can be set according to the system
requirement.

The two bits, RF_EN and IF_EN, logically select the active state of the RF synthesizer system and the IF PLL, respectively. The
entire IC can be placed in a power down state by using the CE control pin (pin 20).

R1 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 2221 201918171615141312 11 109876543 2 1 0

Data Field Address

Register

R1
(Default)

IF_
FREQ
[1:0]

OSC_
FREQ

10000000SPUR_

RDT
[1:0]

0 0101OB_

CRL
[1:0]

RF_ENIF_EN01

Field

LMX2502/LMX2512

Name Functions

IF_FREQ [1:0] IF Frequency Selection

00 = 170.76 MHz (LMX2512LQ0967)
01 = 367.20 MHz (LMX2512LQ1065)
10 = 440.76 MHz (LMX2502LQ1635)

OSC_FREQ Reference Frequency Selection

0 = 19.20 MHz
1 = 19.68 MHz

SPUR_RDT [1:0] Spur Reduction Scheme

00 = No spur reduction
01 = Not Used
10 = Continuous tracking of variation (Recommended)
11 = One time optimization

OB_CRL [1:0] RF Output Power Control

00 = Minimum Output Power
01 =
10 =
11 = Maximum Output Power

RF_EN RF Enable

0=RFOff
1=RFOn

IF_EN IF Enable

0=IFOff
1=IFOn

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Programming Description (Continued)

R2 REGISTER

The R2 Register address bits (R2 [1:0]) are “10”.
The IF_CUR [1:0] bits program the IF charge-pump current. Considering the external IF VCO and loop filter, the user can select

the amount of IF charge pump current to be 100 µA, 200 µA, 300 µA or 800 µA.

LMX2502/LMX2512

MSB SHIFT REGISTER BIT LOCATION LSB

23 22212019181716151413121110987654321 0

Register

R2
(Default)

IF_
CUR[1:0]

R2 REGISTER

Data Field Address

Field

0010011101101010001010

Name Functions

IF_CUR [1:0] IF Charge Pump Current

00 = 100 µA
01 = 200 µA
10 = 300 µA
11 = 800 µA

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Programming Description (Continued)

R3 REGISTER

The R3 register address bits (R3 [2:0]) are “011”.
Register R3 contains the controls for the phase lock bandwidth controls (BW_DUR, BW_CRL, and BW_EN). The duration of the

digital controller portion of the bandwidth control is set by BW_DUR [1:0]. The minimum time set with 00 and increasing durations
to the maximum value set with 11. BW_CRL [1:0] sets the phase offset criterion for the bandwidth controller. Once the phase
offset between the reference clock and the divided VCO signal are within the set criterion, the bandwidth control stops. The
maximum phase offset is set with 00 and decreases to the minimum value set with 11. BW_EN enables the bandwidth control in
the locking state.

The VCO dynamic current is also controlled in register R3 with VCO_CUR [1:0]. The minimum value corresponds to 00 and
increases to a maximum value set at 11.

R3 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 22212019 181716151413121110987654 3 210

Data Field Address

Register

R3
(Default)

BW_
DUR
[1:0]

BW_
CRL
[1:0]

BW_EN10111101000110VCO_

CUR
[1:0]

Field

011

LMX2502/LMX2512

Name Functions

BW_DUR [1:0] Bandwidth Duration

00 = Minimum value (Recommended)
01 =
10 =
11 = Maximum value

BW_CRL [1:0] Bandwidth Control

00 = Maximum phase offset (Recommended)
01 =
10 =
11 = Minimum phase offset

BW_EN Bandwidth Enable

0 = Disable
1 = Enable (Recommended)

VCO_CUR [1:0] VCO Dynamic Current

00 = Minimum value
01 =
10 =
11 = Maximum value (Recommended)

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Programming Description (Continued)

R4 REGISTER

The R4 register address bits (R3 [3:0]) are “0111”.
Register R4 is used to set the IF N counters if the default value is not desired. This register is only active if the SPI_DEF bit in

register R0 is 0.

LMX2502/LMX2512

R4 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 222120191817161514131211109876543210

Data Field Address

Register

R4 0 001000 IF_A

[3:0]

Name Functions

IF_A [3:0] IF A Counter

IF_B [8:0] IF B Counter

IF Frequency Setting:

= {16 x IF_B + IF_A} x f

f

VCO

/ IF_R where (IF_A<IF_B)

OSC

where
f

: Output frequency of IF voltage controlled oscillator (IF VCO)

VCO

IF_B: Preset divide ratio of binary 9-bit programmable counter (1 ≤ IF_B ≤ 511)
IF_A: Preset divide ratio of binary 4-bit swallow counter (0 ≤ IF_A ≤ 15)
IF_R: Preset divide ratio of binary 9-bit programmable reference counter (2 ≤ IF_R ≤ 511)

: Reference oscillator frequency

f

OSC

IF_B
[8:0]

4-bit swallow counter
0 ≤ IF_A ≤ 15

9-bit programmable counter
1 ≤ IF_B ≤ 511

Field

0111

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Programming Description (Continued)

R5 REGISTER

The R5 register address bits (R5 [4:0]) are “01111” .
Register R5 is used to set the IF_R divider if the default value is not desired. This register is only active if the SPI_DEF bit in

register R0 is 0.

R5 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 222120191817161514131211109876543210

Data Field Address

Register

R5 0 011000010 IF_R

[8:0]

Name Functions

IF_R [8:0] IF R Counter

9-bit programmable counter
2 ≤ IF_R ≤ 511

R6 REGISTER

The R6 register address bits (R6 [5:0]) are “011111” .
Register R6 is used for internal testing of the device and is not intended for customer use. This register is only active if the

SPI_DEF bit in register R0 is 0.

Field

01111

LMX2502/LMX2512

R6 REGISTER

MSB SHIFT REGISTER BIT LOCATION LSB

23 222120191817161514131211109876543210

Register

R6 1 00000000000000000011111

Data Field Address Field

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Physical Dimensions inches (millimeters) unless otherwise noted

Leadless Leadframe Package (LLP)

NS Package Number LQA28A

LIFE SUPPORT POLICY

LMX2502/LMX2512 Frequency Synthesizer System with Integrated VCO

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the

2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.

labeling, can be reasonably expected to result in a
significant injury to the user.

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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.