ICS9220 Datasheet, PDF (13/17 Pages) Integrated Device Technology – Programmable RambusTM XDRTM Clock Generator

ICS9220
Input Clock Signal
The ICS9220 receives either a differential or single-ended reference clock (CLK_INT/C). When the reference input clock
is from a differential clock source, it must meet the voltage levels and timing requirements listed in the DC
Characteristics – Inputs and AC Characteristics – Inputs tables.
For a singled-ended clock input, an external voltage divider and a supply voltage, as shown in Figure 2, provide a
reference voltage V_TH at the CLK_INC pin to determine the proper switching point for CLK_INT. The range of V_TH is
specified in the DC Characteristics – Inputs table.
Swing Current
Control
ISET
R_RC
ODCLK_T
Differential Driver
ODCLK_C
V_TS
R₁
R₂
Measurement
Point
Z_CH
R₃
V_TS ^Measurement
Point
R₁
R₂
Z_CH
R₃
V_T
R_T
V_T
R_T
Figure 2. Example System Clock Driver Equivalent Circuit
V_H
80%
V(t)
20%
V_L
t_F
t_R
Figure 3. Input and Output Voltage Waveforms
ODCLK_T
ODCLK_C
1227G—11/05/07
Figure 4. Crossing-point Voltage
13
Vx+
Vx,nom
Vx-