- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄30773 > LTC6909IMS#TRPBF (LINEAR TECHNOLOGY CORP) SPECIALTY ANALOG CIRCUIT, PDSO16 PDF資料下載
參數(shù)資料
| 型號(hào)： | LTC6909IMS#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 模擬信號(hào)調(diào)理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDSO16 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件頁數(shù)： | 3/22頁 |
| 文件大?。?/td> | 0K |
| 代理商： | LTC6909IMS#TRPBF |
LTC6909
11
6909fa
Spread Spectrum Frequency Modulation
The LTC6909 can operate with spread spectrum frequency
modulation(SSFM).Inthismode,theoscillator’sfrequency
is modulated by a pseudorandom noise (PRN) signal
to spread the oscillator’s energy over a wide frequency
band. This spreading decreases the peak electromagnetic
radiationlevelsandimproveselectromaneticcompatibility
(EMC) performance.
Theamountoffrequencyspreadingisfixedat20%(±10%),
where frequency spreading is defined as:
Frequency Spreading (in %) = 100 (fMAX – fMIN)/fOUT
The IMASTER current is a dynamic signal generated by
a multiplying digital-to-analog converter (MDAC) refer-
enced to ISET and lowpass filtered. IMASTER varies in a
psuedorandom noise-like manner between 0.9 ISET and
1.1 ISET. This causes the output frequency to vary in a
pseudorandom noise-like manner between 0.9 fOUT and
1.1 fOUT.
To disable the SSFM, connect one of the active outputs
to the MOD pin. An AC detector circuit shuts down the
modulation circuitry if a frequency in the vicinity of the
output frequency is detected at the MOD pin.
As stated previously, the modulating waveform is a pseu-
dorandomnoise-likewaveform.Thepseudorandomsignal
is generated by a linear feedback shift register that is 15
bits long. The pseudorandom sequence will repeat every
(215 – 1) N clock cycles. This guarantees a repetition
rate below 13Hz for output frequencies up to 6.67MHz.
Seven bits of the shift register are sent in parallel to the
MDAC which produces the modulating current waveform.
Being a digitally generated signal, the output of the MDAC
is not a perfectly smooth waveform, but consists of (27)
discrete steps that change every shift register clock cycle.
Note that the shift register clock is the output frequency,
fOUT, divided by N, where N is the modulation rate divider
setting, which is determined by the state of the MOD pin.
The MOD pin should be tied to ground for the N = 16 set-
ting. Floating the MOD pin selects N = 32. The MOD pin
should be tied to V+ for the N = 64 setting.
The output of the MDAC is then filtered by a lowpass filter
withacornerfrequencysettothemodulationrate(fOUT/N).
This limits the rate of frequency change and softens the
corners of the frequency control signal, but allows the
waveform to fully settle at each frequency step. The rise
and fall times of this single pole filter are approximately
0.35/fCORNER. This is beneficial for clocking switching
regulators, as discussed in the Applications Information
section. Figure 3 illustrates how the output frequency
varies over time.
Figure 3
operAtion
tREPEAT = ((215 – 1) N)/fOUT
tSTEP = N/fOUT
fOUT + 10%
128 STEPS
tREPEAT
tSTEP
fOUT – 10%
TIME
FREQUENCY
6909 F03
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC693ISW | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| LTC695-3.3IJ | 1-CHANNEL POWER SUPPLY MANAGEMENT CKT, CDIP16 |
| LTC693IN#PBF | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDIP16 |
| LTC695CJ | 1-CHANNEL POWER SUPPLY MANAGEMENT CKT, CDIP16 |
| LTC690IJ8 | 1-CHANNEL POWER SUPPLY MANAGEMENT CKT, CDIP8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC690C | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Microprocessor Supervisory Circuits |
| LTC690CN8 | 功能描述:IC MPU SUPERVISORY CIRCUIT 8-DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型:簡(jiǎn)單復(fù)位/加電復(fù)位 監(jiān)視電壓數(shù)目:1 輸出:開路漏極或開路集電極 復(fù)位:高有效 復(fù)位超時(shí):- 電壓 - 閥值:1.8V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:6-TSOP（0.059"，1.50mm 寬）5 引線 供應(yīng)商設(shè)備封裝:5-TSOP 包裝:剪切帶 (CT) 其它名稱:NCP301HSN18T1GOSCT |
| LTC690CN8#PBF | 功能描述:IC MPU SUPERVISORY CIRCUIT 8-DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 其它有關(guān)文件:STM6905 View All Specifications 標(biāo)準(zhǔn)包裝:1 系列:- 類型:多壓監(jiān)控器 監(jiān)視電壓數(shù)目:5 輸出:開路漏極或開路集電極 復(fù)位:低有效 復(fù)位超時(shí):最小為 140 ms 電壓 - 閥值:2.188V，2.955V，可調(diào)，可調(diào)，可調(diào) 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:8-TSSOP 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1197 (CN2011-ZH PDF) 其它名稱:497-8728-6 |
| LTC690CN8PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Microprocessor Supervisory Circuits |
| LTC690CN8-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Microprocessor Supervisory Circuits |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。