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S4402A-80/TD 参数 Datasheet PDF下载

S4402A-80/TD图片预览
型号: S4402A-80/TD
PDF下载: 下载PDF文件 查看货源
内容描述: [Clock Generator, 80MHz, BICMOS, PQCC28, PLASTIC, LCC-28]
分类和应用: 时钟信息通信管理外围集成电路晶体
文件页数/大小: 13 页 / 151 K
品牌: AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
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BiCMOS PLL CLOCK GENERATOR  
S4402/S4403  
Enabling Outputs  
Power Supply Considerations  
The S4402 has two output-enable inputs that con-  
trol which outputs toggle. (The S4403 has three  
output-enable inputs.) When held LOW, OUTEN0  
controls the frequency doubler output X2FOUT  
and the half-frequency output HFOUT. OUTEN1  
controls the FOUT0–FOUT3 outputs. The third in-  
put on the S4403, OUTEN2, controls the duplicate  
set of four outputs FOUT0A–FOUT3A. When an  
output enable pin is held High, its associated out-  
puts are disabled and held in a High state.  
Power for the analog portion of the S4402/S4403  
chips must be isolated from the digital power supplies  
to minimize noise on the analog power supply pins.  
This isolation between the analog and digital power  
supplies can be accomplished with a simple external  
power supply filter (Figure 3). The analog power  
planes are connected to the digital power planes  
through single ferrite beads (FB1 and FB2) or induc-  
tors capable of handling 25 mA. The recommended  
value for the inductors is in the range from 5 to  
100µH, and depends upon the frequency spectrum of  
the digital power supply noise. The ferrite beads  
should exhibit 75impedance at 10 MHz.  
Filter  
The FILTER output is a tap between the analog out-  
put of the phase detector and the VCO input. This pin  
allows a simple external filter (Figure 2) to be in-  
cluded in the PLL. AMCC recommends the use of the  
filter component values shown. This filter was chosen  
for its ability to reduce the output jitter and filter out  
noise on the REFCLK input. The filter components  
should be in surface mounted packages with mini-  
mum lead inductance.  
Decoupling capacitors are also very important to mini-  
mize noise. The decoupling capacitors must have low  
lead inductance to be effective, so ceramic chip ca-  
pacitors are recommended. Decoupling capacitors  
should be located as close to the power pins as physi-  
cally possible. And the decoupling should be placed  
on the top surface of the board between the part and  
its connections to the power and ground planes.  
Figure 3. External Power Supply Filter  
Figure 2. External PLL Filter  
20  
FB1  
A +5V  
A VCC  
DIGITAL +5V  
ANALOG +5V  
0.1µF  
10 µF  
Tantalum  
(optional)  
0.1 µF  
S4402  
1.5k  
19  
FB2  
FILTER  
DIGITAL GND  
ANALOG GND  
Test Capabilities  
Reset  
When the RESET pin is pulled low, all the internal  
states go to zero one clock cycle (from the VCO or  
REFCLK in the test mode) before the outputs go low.  
After the chip is reset, the PLL requires a  
resynchronization time of 5ms before lock is again  
achieved.  
The TSTEN input puts the S4402/S4403 into a test  
mode and allows users to bypass the VCO and pro-  
vide their own clock through the REFCLK input.  
When TSTEN is High, the VCO is turned off and the  
REFCLK signal drives the divider/phase adjust cir-  
cuitry, directly sequencing the outputs. The TSTEN  
and REFCLK inputs join the divider circuitry after the  
initial divide-by-two stage. Therefore, REFCLK is di-  
vided by two in the divide-by-four mode and divided  
by four in the divide-by-eight mode.  
Lock Detect  
A lock detect function is provided by the LOCK out-  
put. When REFCLK and FBCLK are within 2–4 ns of  
each other, the PLL is in lock, and the LOCK output  
goes High.  
Applied Micro Circuits Corporation  
6195 Lusk Blvd., San Diego, CA 92121 • (619) 450-9333  
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