LMX2355TM datasheet(10/23 Pages) NSC

tên linh kiện	LMX2355TM

Giải thích chi tiết về linh kiện	PLLatinum Fractional N RF/ Integer N IF Dual Low Power Frequency Synthesizer

Download	23 Pages

Scroll/Zoom	100%

nhà sản xuất	NSC [National Semiconductor (TI)]

Trang chủ	http://www.national.com

Logo

10 / 23 page

Functional Description

1.0 GENERAL

The basic phase-lock-loop (PLL) configuration consists of a

high-stability crystal reference oscillator, a frequency synthe-

sizer such as the National Semiconductor LMX2354, a volt-

age controlled oscillator (VCO), and a passive loop filter. The

frequency synthesizer includes a phase detector, current

mode charge pump, as well as programmable reference [R]

and feedback [N] frequency dividers. The VCO frequency is

established by dividing the crystal reference signal down via

the R counter to obtain a frequency that sets the comparison

frequency. This reference signal, f

r, is then presented to the

input of a phase/frequency detector and compared with an-

other signal, f

p, the feedback signal, which was obtained by

dividing the VCO frequency down by way of the N counter

and fractional circuitry. The phase/frequency detector’s cur-

rent source outputs pump charge into the loop filter, which

then converts the charge into the VCO’s control voltage. The

phase/frequency comparator’s function is to adjust the volt-

age presented to the VCO until the feedback signal’s fre-

quency (and phase) match that of the reference signal.

When this ‘phase-locked’ condition exists, the RF VCO’s

frequency will be N+F times that of the comparison fre-

quency, where N is the integer divide ratio and F is the

fractional component. The fractional synthesis allows the

phase detector frequency to be increased while maintaining

the same frequency step size for channel selection. The

division value N is thereby reduced giving a lower phase

noise referred to the phase detector input, and the compari-

son frequency is increased allowing faster switching times.

1.1 REFERENCE OSCILLATOR INPUTS

The reference oscillator frequency for the RF and IF PLLs is

provided by an external reference through the OSC

IF pin and

OSC

RF pin. OSCIF/OSCRF block can operate 50 MHz with

an input sensitivity of 0.5 Vpp. The OSC bit (see program-

ming description 4.1.1), selects whether the oscillator input

pins OSC

IF and OSCRF drive the IF and RF R counters

separately or by a common input signal path. When an

external TCXO is connected only at the OSC

IF input pin and

not at the OSC

RF pin, the TCXO drives both IF R counter

and RF R counter. When configured as separate inputs, the

OSC

IF pin drives the IF R counter while the OSCRF drives

the RF R counter. The inputs have a V

CC/2 input threshold

and can be driven from an external CMOS or TTL logic gate.

1.2 REFERENCE DIVIDERS (R COUNTERS)

The RF and IF R Counters are clocked through the oscillator

block either separately or in common. The maximum fre-

quency is 50 MHz. Both R Counters are 15-bit CMOS

counters with a divide range from 3 to 32,767. (See program-

ming description 4.1.3.)

1.3 PROGRAMMABLE DIVIDERS (N COUNTERS)

The RF and IF N Counters are clocked by the small signal fin

RF and fin IF input pins respectively. The RF N Counter can

be configured as a fractional or fully integer counter. The

LMX2354 RF N counter is 19 bits with 15 bits integer divide

and 4 bits fractional. The integer part is configured as a 2-bit

A Counter, a 2-bit B Counter and a 11-bit C Counter. The

LMX2354 is capable of operating from 500 MHz to 1.2 GHz

with the 8/9/12/13 prescaler offering a continuous integer

divide range from 40 to 16,383 in fractional mode and 24 to

262143 in full integer mode. The LMX2354 is capable of

operating from 1.2 GHz to 2.5 GHz with the 16/17/20/21

prescaler offering a continuous integer divide range from 80

to 32,767 in fractional mode and 48 to 52,4287 in full integer

mode. The RF counters for the LMX2354 also contain frac-

tional compensation, programmable in either 1/15 or 1/16

modes. The LMX2354 IF N counter is 15-bit integer divider

configured with a 3-bit A Counter and a 12-bit B Counter

offering a continuous integer divide range from 56 to 32,767

over the frequency range of 10 MHz to 550 MHz. The IF N

counter does not include fractional compensation. The

tables below show the differences between the LMX2354 in

integer mode and in quadruple modulus prescaler with P =

16/17/20/21. Also, the tables show that the bit used for the

lower modulus prescaler values is different between the

LMX2350 and the LMX2354. For the LMX2350 bit N<9> =0

(MSB of the A Word) is used for the 16/17 modulus and for

the LMX2354 bit N<8> =0 is used for the 8/9/12/13 modu-

lus. So if the LMX2354 is replacing a LMX2350 then bits

N<8> and N<9> need to be swapped.

LMX2354 RF N Counter Register in Fractional Mode with P = 16/17/20/21:

C Word

B Word

A Word

Fractional Word

N

19

18

17

16

15

14

13

12

11

10

987

6

5432

1

1–47

Divide ratios less than 48 are impossible since it is required that C

≥3

These bits are used for

the fractional word when

the part is operated in

fractional mode

48–79

Some of these values are legal divide ratios, some are not

80*

000000

0

1

0100

0

81

000000

0

1

0100

0

1

...

1056

000010

0

1000

0

...

......

.

....

.

32,767

111111

1

1111

1

*Minimum continuous divide ratio is P

•[MAX{A,B}+2]

www.national.com

10

Số phần tương tự - LMX2355TM

nhà sản xuất	tên linh kiện	bảng dữ liệu	Giải thích chi tiết về linh kiện
National Semiconductor ...	LMX2350	408Kb / 21P	PLLatinum TM Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
Texas Instruments	LMX2350	449Kb / 23P	[Old version datasheet] PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
National Semiconductor ...	LMX2350TM	408Kb / 21P	PLLatinum TM Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
Texas Instruments	LMX2352	449Kb / 23P	[Old version datasheet] PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
National Semiconductor ...	LMX2352TM	408Kb / 21P	PLLatinum TM Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer

More results

Mô tả tương tự - LMX2355TM

nhà sản xuất	tên linh kiện	bảng dữ liệu	Giải thích chi tiết về linh kiện
Texas Instruments	LMX2350	449Kb / 23P	[Old version datasheet] PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
National Semiconductor ...	LMX2350	408Kb / 21P	PLLatinum TM Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
Texas Instruments	LMV2350	449Kb / 23P	[Old version datasheet] LMX2350/LMX2352 PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency Synthesizer
Hynix Semiconductor	HM6F5201	328Kb / 25P	Dual Fractional-N / Integer-N Frequency Synthesizer
Analog Devices	ADF4251	440Kb / 28P	Dual Fractional-N/Integer-N Frequency Synthesizer REV. 0
National Semiconductor ...	LMX2364	694Kb / 39P	2.6 GHz PLLatinum Fractional RF Frequency Synthesizer with 850 MHz Integer IF Frequency Synthesizer
Analog Devices	ADF4252	476Kb / 28P	Dual Fractional-N/Integer-N Frequency Synthesizer REV. B
	ADF4251	424Kb / 28P	Dual Fractional-N/Integer-N Frequency Synthesizer REV. 0
	ADF4252	497Kb / 28P	Dual Fractional-N/Integer-N Frequency Synthesizer REV. B
	ADF4252	507Kb / 30P	Dual Fractional-N/Integer-N Frequency Synthesizer Rev. E

More results

LMX2355TM bảng dữ liệu(PDF) 10 Page - National Semiconductor (TI)

LMX2355TM bảng dữ liệu(HTML) 10 Page - National Semiconductor (TI)

Số phần tương tự - LMX2355TM

Mô tả tương tự - LMX2355TM

Html Pages

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

bảng dữ liệu tải về

Link URL