IDT
®
Four Output Differential Frequency Generator for PCIe Gen3 and QPI 1681D—04/04/17
9FG430
Four Output Differential Frequency Generator for PCIe Gen3 and QPI
3
Pin Description
PIN # PIN NAME PIN TYPE DESCRIPTION
1 XIN/CLKIN IN Crystal input or Reference Clock input
2 X2 OUT Crystal output, Nominally 14.318MHz
3 VDD PWR Power supply, nominal 3.3V
4 GND PWR Ground pin.
5 REFOUT OUT Reference Clock output
6 vFS2 IN Frequency select pin. This pin has an internal 120k pull down resistor
7 DIF_3 OUT 0.7V differential true clock output
8 DIF_3# OUT 0.7V differential Complementary clock output
9 VDD PWR Power supply, nominal 3.3V
10 GND PWR Ground pin.
11 DIF_2 OUT 0.7V differential true clock output
12 DIF_2# OUT 0.7V differential Complementary clock output
13 SDATA I/O Data pin for SMBus circuitry, 5V tolerant.
14 SCLK IN Clock pin of SMBus circuitry, 5V tolerant.
15 DIF_STOP# IN Active low input to stop differential output clocks.
16 vSPREAD IN
Asynchronous, active high input to enable spread spectrum functionality. This pin
has a 120Kohm pull down resistor.
17 ^SEL14M_25M# IN
Select 14.31818 MHz or 25 Mhz input frequency. This pin has an internal 120kohm
pull up resistor.
1 = 14.31818 MHz, 0 = 25 MHz
18 DIF_1# OUT 0.7V differential Complementary clock output
19 DIF_1 OUT 0.7V differential true clock output
20 GND PWR Ground pin.
21 VDD PWR Power supply, nominal 3.3V
22 DIF_0# OUT 0.7V differential Complementary clock output
23 DIF_0 OUT 0.7V differential true clock output
24 vFS1 IN Frequency select pin.
25 vFS0 IN Frequency select pin.
26 IREF OUT
This pin establishes the reference for the differential current-mode output pairs. It
requires a fixed precision resistor to ground. 475ohm is the standard value for
100ohm differential impedance. Other impedances require different values. See
data sheet.
27 GNDA PWR Ground pin for the PLL core.
28 VDDA PWR 3.3V power for the PLL core.
Note:
^ indicates internal 120K pull up
v indicates internal 120K pull down
