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參數(shù)資料
| 型號(hào)： | LMX2324ATM |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | PLL合成/DDS/VCOs |
| 英文描述： | PLL FREQUENCY SYNTHESIZER, 2200 MHz, PDSO16 |
| 封裝： | TSSOP-16 |
| 文件頁(yè)數(shù)： | 8/12頁(yè) |
| 文件大?。?/td> | 157K |
| 代理商： | LMX2324ATM |
1.0 Functional Description
The basic phase-lock-loop (PLL) configuration consists of a
high-stability crystal reference oscillator, a frequency synthe-
sizer such as the National Semiconductor LMX2324A, a
voltage controlled oscillator (VCO), and a passive loop filter.
The frequency synthesizer includes a phase detector, cur-
rent 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 com-
parison frequency. This reference signal, f
r, is then pre-
sented to the input of a phase/frequency detector and com-
pared with another signal, f
p, the feedback signal, which was
obtained by dividing the VCO frequency down by way of the
N counter. The phase/frequency detector’s current 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 voltage
presented to the VCO until the feedback signal’s frequency
(and phase) match that of the reference signal. When this
“phase-locked” condition exists, the RF VCO’s frequency will
be N times that of the comparison frequency, where N is the
divider ratio.
1.1 OSCILLATOR
The reference oscillator frequency for the PLL is provided by
an external reference TCXO through the OSC
in pin. OSCin
block can operate to 40 MHz with a minimum input sensitivity
of 0.4V
PP. The inputs have a VCC/2 input threshold and can
be driven from an external CMOS or TTL logic gate.
1.2 REFERENCE DIVIDERS (R COUNTER)
The R Counter is clocked through the oscillator block. The
maximum frequency is 40 MHz. The R Counter is a 10 bit
CMOS binary counters with a divide range from 2 to 1,023.
See programming description 2.2.1.
1.3 PROGRAMMABLE DIVIDERS (N COUNTER)
The N counter is clocked by the small signal f
IN and fINB input
pins. The LMX2324A RF N counter is 15 bit integer divider.
The N counter is configured as a 5 bit A Counter and a 10 bit
B Counter, offering a continuous integer divide range from
992 to 32,767. The LMX2324A is capable of operating from
100 MHz to 2.0 GHz with a 32/33 prescaler.
1.3.1 Prescaler
The RF inputs to the prescaler consist of the f
IN and fINB pins
which are the complimentary inputs of a differential pair
amplifier. The differential f
IN configuration can operate to
2 GHz with an input sensitivity of 15 dBm. The input buffer
drives the N counter’s ECL D-type flip flops in a dual modu-
lus configuration. A 32/33 prescale ratio is provided for the
LMX2324A. The prescaler clocks the subsequent CMOS
flip-flop chain comprising the fully programmable A and B
counters.
1.4 PHASE/FREQUENCY DETECTOR
The phase(/frequency) detector is driven from the N and R
counter outputs. The maximum frequency at the phase de-
tector inputs is 10 MHz. The phase detector outputs control
the charge pumps. The polarity of the pump-up or pump-
down control is programmed using PD_POL, depending on
whether RF VCO characteristics are positive or negative
(see programming description 2.2.2). The phase detector
also receives a feedback signal from the charge pump, in
order to eliminate dead zone.
1.5 CHARGE PUMP
The phase detector’s current source output pumps charge
into an external loop filter, which then converts the charge
into the VCO’s control voltage. The charge pumps steer the
charge pump output, CP
o,toVP
(pump-up) or Ground
(pump-down). When locked, CP
o is primarily in a TRI-STATE
mode with small corrections. The RF charge pump output
current magnitude is set to 4.0 mA. The charge pump output
can also be used to output divider signals as detailed in
section 2.2.3.
1.6 MICROWIRE SERIAL INTERFACE
The programmable functions are accessed through the
MICROWIRE serial interface. The interface is made of three
functions: clock, data and latch enable (LE). Serial data for
the various counters is clocked in from data on the rising
edge of clock, into the 18-bit shift register. Data is entered
MSB first. The last bit decodes the internal register address.
On the rising edge of LE, data stored in the shift register is
loaded into one of the two appropriate latches (selected by
address bits). A complete programming description is in-
cluded in the following sections.
1.7 POWER CONTROL
The PLL can be power controlled in two ways. The first
method is by setting the CE pin LOW. This asynchronously
powers down the PLL and TRI-STATE the charge pump
output, regardless of the PWDN bit status. The second
method is by programming through MICROWIRE, while
keeping the CE HIGH. Programming the PWDN bit in the N
register HIGH (CE=HIGH) will disable the N counter and
de-bias the f
IN input (to a high impedance state). The R
counter functionality also becomes disabled. The reference
oscillator block powers down when the power down bit is
asserted. The OSC
in pin reverts to a high impedance state
when this condition exists. Power down forces the charge
pump and phase comparator logic to a TRI-STATE condition.
A power down counter reset function resets both N and R
counters. Upon powering up the N counter resumes count-
ing in “close” alignment with the R counter (The maximum
error is one prescaler cycle). The MICROWIRE control reg-
ister remains active and capable of loading and latching in
data during all of the power down modes.
LMX2324A
www.national.com
5
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| LMX2324ATMX | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:PLLatinum? 2.2 GHz Frequency Synthesizer for RF Personal Communications (SL163188) |
| LMX2324SLBX | 功能描述:IC FREQ SYNTH 2.0GHZ 16LAMINATE RoHS:否 類(lèi)別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 時(shí)鐘發(fā)生器，PLL，頻率合成器 系列:PLLatinum™ 標(biāo)準(zhǔn)包裝:39 系列:- 類(lèi)型:* PLL:帶旁路 輸入:時(shí)鐘 輸出:時(shí)鐘 電路數(shù):1 比率 - 輸入:輸出:1:10 差分 - 輸入:輸出:是/是 頻率 - 最大:170MHz 除法器/乘法器:無(wú)/無(wú) 電源電壓:2.375 V ~ 3.465 V 工作溫度:0°C ~ 70°C 安裝類(lèi)型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LMX2324TM | 功能描述:IC FREQ SYNTHESIZER 16-TSSOP RoHS:否 類(lèi)別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 時(shí)鐘發(fā)生器，PLL，頻率合成器 系列:PLLatinum™ 標(biāo)準(zhǔn)包裝:39 系列:- 類(lèi)型:* PLL:帶旁路 輸入:時(shí)鐘 輸出:時(shí)鐘 電路數(shù):1 比率 - 輸入:輸出:1:10 差分 - 輸入:輸出:是/是 頻率 - 最大:170MHz 除法器/乘法器:無(wú)/無(wú) 電源電壓:2.375 V ~ 3.465 V 工作溫度:0°C ~ 70°C 安裝類(lèi)型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LMX2324TMX | 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:Serial-Input Frequency Synthesizer |
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