FEMTOC
參數(shù)資料
型號(hào): ICS843020AY-01LF
廠商: IDT, Integrated Device Technology Inc
文件頁數(shù): 12/21頁
文件大?。?/td> 0K
描述: IC SYNTHESIZER LVPECL 32-LQFP
標(biāo)準(zhǔn)包裝: 250
系列: HiPerClockS™, FemtoClock™
類型: 頻率合成器
PLL: 帶旁路
輸入: 晶體
輸出: LVPECL
電路數(shù): 1
比率 - 輸入:輸出: 1:2
差分 - 輸入:輸出: 無/是
頻率 - 最大: 680MHz
除法器/乘法器: 是/無
電源電壓: 3.135 V ~ 3.465 V
工作溫度: 0°C ~ 70°C
安裝類型: 表面貼裝
封裝/外殼: 32-LQFP
供應(yīng)商設(shè)備封裝: 32-TQFP(7x7)
包裝: 托盤
其它名稱: 843020AY-01LF
843020AY-01
www.idt.com
REV. C JULY 26, 2010
2
ICS843020-01
FEMTOCLOCKS 680MHZ, CRYSTAL-TO-
3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
NOTE: The functional description that follows describes op-
eration using a 25MHz crystal. Valid PLL loop divider values
for different crystal or input frequencies are defined in the In-
put Frequency Characteristics, Table 5, NOTE 1.
The ICS843020-01 features a fully integrated PLL and there-
fore requires no external components for setting the loop band-
width. A fundamental crystal is used as the input to the on-
chip oscillator. The output of the oscillator is fed into the phase
detector. A 25MHz crystal provides a 25MHz phase detector
reference frequency. The VCO of the PLL operates over a
range of 560MHz to 680MHz. The output of the M divider is
also applied to the phase detector.
The phase detector and the M divider force the VCO output fre-
quency to be M times the reference frequency by adjusting the
VCO control voltage. Note that for some values of M (either too
high or too low), the PLL will not achieve lock. The output of the
VCO is scaled by a divider prior to being sent to each of the LVPECL
output buffers. The divider provides a 50% output duty cycle.
The ICS843020-01 supports either serial or parallel program-
ming modes to program the M feedback divider and N output
divider. The input divider P can only be changed using the P_DIV
pin. It cannot be changed from the default
÷1 setting using the
serial interface.
Figure 1 shows the timing diagram for each mode.
In parallel mode, the nP_LOAD input is initially LOW. The data
on inputs M0 through M8 and N0 and N1 is passed directly to
the M divider and N output divider. On the LOW-to-HIGH transi-
tion of the nP_LOAD input, the data is latched and the M divider
remains loaded until the next LOW transition on nP_LOAD or
until a serial event occurs. As a result, the M and N bits can be
hardwired to set the M divider and N output divider to a specific
default state that will automatically occur during power-up. The
TEST output is LOW when operating in the parallel input mode.
The relation-ship between the VCO frequency, the crystal fre-
quency and the M divider is defined as follows:
The M value and the required values of M0 through M8 are
shown in Table 3B to program the VCO Frequency Function
Table. Valid M values for which the PLL will achieve lock for a
25MHz reference are defined as 23
≤ M ≤ 27 (P = ÷1). The
frequency out is defined as follows:
Serial operation occurs when nP_LOAD is HIGH and S_LOAD
is LOW. The shift register is loaded by sampling the S_DATA
bits with the rising edge of S_CLOCK. The contents of the
shift register are loaded into the M divider and N output di-
vider when S_LOAD transitions from LOW-to-HIGH. The M
divide and N output divide values are latched on the HIGH-to-
LOW transition of S_LOAD. If S_LOAD is held HIGH, data at
the S_DATA input is passed directly to the M divider and N
output divider on each rising edge of S_CLOCK. The serial
mode can be used to program the M and N bits and test bits
T1 and T0. The internal registers T0 and T1 determine the state
of the TEST output as follows:
FUNCTIONAL DESCRIPTION
T1
T0
TEST Output
0
LOW
0
1
S_Data, Shift Register Input
1
0
Output of M divider
1
CMOS Fout
FIGURE 1. PARALLEL & SERIAL LOAD OPERATIONS
*NOTE: The NULL timing slot must be observed.
Time
SERIAL LOADING
PARALLEL LOADING
M, N, P
t
S
t
H
t
S
t
H
t
S
T1
T0
*NULL
N 1
N 0
M8
M7
M6
M5
M4
M3
M2
M1
M 0
S_CLOCK
S_DATA
S_LOAD
nP_LOAD
M0:M8, N0:N1, P_DIV
nP_LOAD
fVCO = fxtal x M
P
FOUT = fVCO = fxtal x
M
NN x P
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