参数资料
型号: 5P49EE801NDGI
厂商: IDT, Integrated Device Technology Inc
文件页数: 25/27页
文件大小: 0K
描述: IC CLOCK GENERATOR 28QFN
标准包装: 75
系列: VersaClock™
类型: 时钟发生器
PLL: 带旁路
输入: LVTTL,晶体
输出: LVCMOS,LVDS,LVTTL
电路数: 1
比率 - 输入:输出: 2:7
差分 - 输入:输出: 无/是
频率 - 最大: 150MHz
除法器/乘法器: 是/无
电源电压: 1.71 V ~ 1.89 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 28-VFQFN 裸露焊盘
供应商设备封装: 28-VFQFPN(4x4)
包装: 管件
其它名称: 800-2524
IDT5P49EE801
VERSACLOCK LOW POWER CLOCK GENERATOR
EEPROM CLOCK GENERATOR
IDT VERSACLOCK LOW POWER CLOCK GENERATOR
7
IDT5P49EE801
REV M 072512
SPREAD SPECTRUM GENERATION
(PLLB)
PLLB has spread spectrum generation capability, which
users have the option of turning on and off. Spread
spectrum profile, frequency, and spread are fully
programmable (within limits). The programmable spread
spectrum generation parameters are NC[10:0], MOD[12:0],
and NSS[10:0] bits. To enable spread spectrum, set
SSENB_B=0.
The spread spectrum circuitry was specifically developed to
accommodate video display applications. The spread
modulation frequency can be defined to exactly equal the
horizontal line frequency (HSYNC)
NC[10:0]
These bits are used to determine the number of pulses per
spread spectrum cycle. For video applications, NC is the
number of pixels on the horizontal display row (or integer
multiple of displayed pixels in a row). By matching the
spread period to the screen, no tearing or “shimmer” will be
apparent.
NC must be an even number to insure that the upward
spread transition has the same number of steps as the
downward spread transition.
For non-video applications, this can also be seen as the
number of clock cycles for a complete spread spectrum
period.
MOD[12:0]
These bits relate the VCO frequency to the target average
spread output frequency (FMID).
FMID = (FVCO) / 8
FMAX = FMID + (SS% * FMID)
FMIN = FMID - (SS% * FMID)
MOD = (FREF* NC) / (2 * FMID)
NSS[10:0]
These bits control the amplitude of the spread modulation.
NSS = (NC / 2) + (NC / 8) * (FMAX - FMIN) / FMID
Modulation frequency:
FMOD = FMID / NC (Eq. 11)
Video Example
FREF = 27 MHz, FOUT = 27 MHz, 640 pixels per line, center
spread of ±1%. Using FVCO=432MHz, find the necessary
spread spectrum register settings.
FMID = FVCO/8
NC = 640 (integer number of spread periods/screen)
MOD = (25MHz * 640)/(2 * 54MHz) = 160
NSS = (640/2)+(640/8)*(27.27MHz-26.73MHz)/27MHz =
321.
FMOD = 27MHz/640 = 11.8kHz.
Non-Video Example
FREF = 25MHz, FOUT = 27 MHz, 31.25kHz modulation rate,
center spread of ±1%. Find the necessary spread spectrum
register settings.
FMID = FVCO/ 8
FMOD = 31.25kHz = 50.625MHz/NC.
NC = 1620
MOD = (25MHz * 1620)/(2 * 50.625MHz) = 400
NSS = (1620/2)+(1620/8)*(27.27MHz-26.73MHz)/27MHz =
814.
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