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參數(shù)資料
| 型號(hào)： | LTC6902CMS |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | XO, clock |
| 英文描述： | Multiphase Oscillator with Spread Spectrum Frequency Modulation |
| 中文描述： | PLL FREQUENCY SYNTHESIZER, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁(yè)數(shù)： | 11/16頁(yè) |
| 文件大小： | 212K |
| 代理商： | LTC6902CMS |
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LTC6902
11
6902f
THEORY OF OPERATIOU
f
MAX
f
MIN
128 STEPS
TIME
69012 F05
3200
f
MASTER
F
τ
STEP
τ
STEP
=
τ
REPEAT
3200 512
f
MASTER
τ
REPEAT
=
Figure 5
APPLICATIOU
W
U
U
SELECTING THE DIVIDER SETTING AND R
SET
VALUE
The LTC6902’s master oscillator has a frequency range
spanning 0.1MHz to 20MHz. However, accuracy may
suffer if the master oscillator is operated at greater than
10MHz with a supply voltage lower than 4V. A program-
mable divider extends the frequency range to greater than
three decades. Additional frequency division may occur
depending on the multiphase mode selected. The
multiphase mode and the parameter M are generally
dependent on the application’s requirement and usually
do not offer any additional design flexibility.
The LTC6902’s master oscillator covers a 200:1 range
while the programmable divider has 10:1 steps (1, 10,
100). This wide frequency range coupled with the part’s
programmable divider yields at least two solutions for any
desired output frequency (the exception being the highest
output frequencies that cannot be divided down). Choos-
ing the best divider setting and the correct R
SET
resistor
value depends on the application.
For spread spectrum frequency modulated (SSFM) appli-
cations, choose the highest divider setting. This forces the
master oscillator to run at its highest frequency. The
pseudorandom signal generator is clocked by the master
oscillator, not the output, and the faster the signal moves
the greater the improvement in EMC performance. For
most applications the multiphase mode is determined by
the specific application’s need. For these applications, the
parameter M is predetermined and fixed. Table 1 lists the
recommended output (f
OUT
) frequency range for each
divider setting when using SSFM.
clock cycle. Note that the shift register clock is the master
oscillator’s output divided by 3200. This results in a some-
what slow moving modulating signal where each step is
separated in time by 3200/f
MASTER
seconds and the pseu-
dorandom sequence repeats every (512 3200)/f
MASTER
seconds.
The servo loop in the LTC6902 cannot respond instanta-
neously to each step due to its limited bandwidth. The
V
MOD
voltage steps are converted to frequency steps by
the servo loop. The servo loop has a bandwidth of about
25kHz that limits the frequency change rate and softens
corners of the waveform. This is beneficial when the
LTC6902 is used to clock switching regulators as will be
discussed in the Applications Information section. Fig-
ure5 illustrates the how the output frequency varies over
time.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC6902CMS#PBF | 功能描述:IC OSC SILICON 20MHZ 10MSOP RoHS:是 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 可編程計(jì)時(shí)器和振蕩器 系列:- 標(biāo)準(zhǔn)包裝:3,000 系列:- 類型:振蕩器 - 晶體 計(jì)數(shù):- 頻率:- 電源電壓:2.3 V ~ 5.5 V 電流 - 電源:1.07mA 工作溫度:-30°C ~ 80°C 封裝/外殼:SOT-665 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:SS迷你型-5D 安裝類型:表面貼裝 其它名稱:AN8955SSMTXLTR |
| LTC6902CMS#PBF | 制造商:Linear Technology 功能描述:Programmable Oscillator IC |
| LTC6902CMS#TR | 功能描述:IC OSC SILICON 20MHZ 10MSOP RoHS:否 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 可編程計(jì)時(shí)器和振蕩器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:45 系列:- 類型:溫度 - 補(bǔ)償晶體振蕩器（TCXO） 計(jì)數(shù):- 頻率:25MHz 電源電壓:3.135 V ~ 3.465 V 電流 - 電源:1.5mA 工作溫度:-40°C ~ 85°C 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 包裝:管件 供應(yīng)商設(shè)備封裝:16-SOIC W 安裝類型:表面貼裝 |
| LTC6902CMS#TRPBF | 功能描述:IC OSC SILICON 20MHZ 10MSOP RoHS:是 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 可編程計(jì)時(shí)器和振蕩器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:45 系列:- 類型:溫度 - 補(bǔ)償晶體振蕩器（TCXO） 計(jì)數(shù):- 頻率:25MHz 電源電壓:3.135 V ~ 3.465 V 電流 - 電源:1.5mA 工作溫度:-40°C ~ 85°C 封裝/外殼:16-SOIC（0.295"，7.50mm 寬） 包裝:管件 供應(yīng)商設(shè)備封裝:16-SOIC W 安裝類型:表面貼裝 |
| LTC6902CMSPBF | 制造商:Linear Technology 功能描述:Programmable oscillator,5K-20MHz |
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