AN408: Termination Options for Any-frequency, Any-output Clock Generators and Clock Buffers

AN408
TERMINATION O P T I O N S FOR A NY - F R E QUE N C Y,
A N Y - O UTPUT C LOCK G ENERATORS A N D C LOCK B UFFERS
1. Introduction
This application note provides termination recommendations for connecting input and output clock signals to the
Si533x and Si5356/55 family of timing ICs and is not applicable to any other Silicon Labs devices.
The Si533x and Si5356/55 family of any-frequency, any-output clock generators and clock buffers greatly simplifies
the task of interfacing between many of today’s common signal types. Both the inputs and the outputs are
compatible with single-ended (LVTTL, CMOS, HSTL, SSTL) and/or differential signals (LVPECL, LVDS, HCSL,
CML) and support multiple supply voltage levels (3.3, 2.5, 1.8, or 1.5 V). All of the inputs and outputs are
configured on a per-port basis offering unprecedented flexibility. Block diagrams of the devices are shown in
Figures 1 and 2. The Si5338 and Si5356 are I2C-configured devices that lock to a crystal or external clock and
generate up to four independent output frequencies. The Si5338 is compatible with both single-ended and
differential clock formats, whereas the Si5356 is limited to single-ended clocks. The Si5334 is a pin-controlled
version of the Si5338 that does not have an I2C interface. Similarly, the Si5355 is a pin-controlled version of the
Si5356. The Si5330 is a non-PLL clock buffer device that provides low jitter clock distribution and level translation.
7, 24
Optional
XTAL
IN1
IN2
V DD
Si5338/34
20
Osc
MultiSynth
÷M0
1
22
÷R0
16
÷P1
IN3
3
MultiSynth
÷M1
PLL
IN4
IN5
IN6
21
2
18
÷R1
4
÷P2
5
MultiSynth
÷M2
6
÷R2
17
INTR/
LOSLOL
12
19
I2C Control
(Si5338 only)
MultiSynth
÷M3
8
23
Si5330
VDDO2
CLK2A
13
CLK2B
21
16
18
LOS
9
VDDO3
CLK3A
CLK3B
V DD
22
IN3
CLK1B
GND
7, 24
20
IN1
IN2
VDDO1
CLK1A
14
10
÷R3
CLK0B
15
11
SCL
SDA
VDDO0
CLK0A
1
17
2
3
VDDO1
CLK1A
CLK1B
VDDO2
14
CLK2A
13
CLK2B
10
9
4, 5, 6, 12, 19, 23
CLK0B
15
11
8
VDDO0
CLK0A
VDDO3
CLK3A
CLK3B
GND
Figure 1. Si5338/34 and Si5330 Block Diagrams
Rev. 0.5 10/13
Copyright © 2013 by Silicon Laboratories
AN408
AN408
7, 24
XTAL
VDD
Si5356
20
Osc
MultiSynth
÷M0
1
22
÷R0
21
2
16
÷P1
CLKin
4
PLL
SCL
SDA
I2C_LSB
OEB
SSC_DIS
INTR
MultiSynth
÷M1
18
÷R1
12
19
MultiSynth
÷M2
3
÷R2
I2C and Pin
Control
6
5
MultiSynth
÷M3
23
VDDOC
CLK4
13
CLK5
9
VDD
Si5355
20
Osc
MultiSynth
÷M0
1
22
÷R0
21
16
÷P1
4
PLL
P4
P5
LOS
MultiSynth
÷M1
18
÷R1
3
12
MultiSynth
÷M2
19
÷R2
VDDOA
CLK0
CLK1
VDDOB
CLK2
CLK3
15
VDDOC
14
CLK4
13
CLK5
Control
11
8
MultiSynth
÷M3
23
10
÷R3
GND
Figure 2. Si5356 and Si5355 Block Diagrams
2
17
5
6
VDDOD
CLK6
CLK7
2
P1
P2
P3
CLK3
GND
7, 24
CLKin
VDDOB
CLK2
14
10
÷R3
CLK1
15
11
8
XTAL
17
VDDOA
CLK0
Rev. 0.5
9
VDDOD
CLK6
CLK7
AN408
2. Inputs
The Si533x and Si5356/55 families support both single-ended and differential inputs. The device supports up to
two single-ended inputs (Pins 3 and 4) and two differential inputs (Pins 1,2, and 5,6). On the Si5338/34 and
Si5356/55 devices, a crystal can be connected to Pins 1 and 2 instead of an input clock. Refer to “AN360: Crystal
Selection Guide for Any-Frequency Devices” for more information on using the crystal input option.
2.1. Single-Ended Inputs
The multi-format single-ended clock inputs of the Si533x and Si5356/55 are ac-coupled internally to remove any dc
bias from the signal. This allows the device to trigger on a signal swing threshold instead of a specific voltage level
(normally specified as VIH and VIL). The receiver accepts any signal with a minimum voltage swing of 800 mVPP
and a maximum of 3.73 VPP regardless of the core VDD supply. For best performance, the slew rate at input Pins 3
and 4 must be greater than 1 V/ns. This makes the inputs 3.3 V-tolerant even when the core voltage is powered
with 1.8 V. An Si5338/34/56/55 should have an input duty cycle no worse than 40/60%. An Si5330 should have an
input duty cycle no worse than 45/55%.
2.1.1. LVTTL/CMOS Inputs
The only termination necessary when interfacing a CMOS driver to the Si533x and Si5356/55 is a source resistor
(Rs) placed near the driver to help match its output impedance to the transmission line impedance. In some cases,
the value for this series resistor may be zero as it depends upon the CMOS driver characteristics. The CMOS
drivers in the Si533x and Si5356/55 are designed to work optimally into a 50  transmission line without an
external source resistor. A typical CMOS signal connection is illustrated in Figure 3. Using this configuration, the
receiver is capable of interfacing to 3.3, 2.5, or 1.8 V CMOS clock signals.
Si533x/56/55
V DD = 3.3 V, 2.5 V, 1.8 V
Rs
50
LVTTL/
CMOS
Figure 3. Interfacing to an LVTTL/CMOS Input Signal
Rev. 0.5
3
AN408
2.1.2. Single-Ended SSTL and HSTL Inputs
HSTL and SSTL single-ended clock inputs should be input to the differential inputs, pins 1 and 2, of the Si533x with
the circuit shown in Figure 4.
Some drivers may require a series 25  resistor. If the SSTL/HSTL input is being driven by another Si533x device,
the 25  series resistor is not required as this is integrated on-chip. The maximum recommended input frequency
in this case is 350 MHz.
Keep termination close to
input pin of the Si533x
VTT
50
0.4 to 1.2 V pk-pk
0.1 uF
Si533x
50
1
Differential
Input
VDD
R1
0.1 uF
VTT
0.1 uF
R2
SSTL_2, SSTL_18, HSTL
R1 = 2.43 k
R2 = 2 k
SSTL_3
R1 = 2.43 k
R2 = 2 k
Figure 4. Single-Ended SSTL/HSTL Input to Pins 1 and 2
4
Rev. 0.5
2
AN408
2.1.3. Applying a Single-Ended Signal to a Differential Input
It is possible to interface any single-ended signal to the differential input pins (IN1/IN2 or IN5/IN6). The
recommended interface for a signal that requires a 50  load is shown in Figure 5. On these inputs, it is important
that the signal level be less than 1.2 VPP SE and greater than 0.4 VPP SE. The maximum recommended input
frequency in this case is 350 MHz.
Keep termination close to
input pin of the Si533x
0.1 uF
0.4 to 1.2V pk-pk
Si533x
50
50
0.1 uF
Figure 5. Single-Ended Input Signal with 50  Termination
2.2. Differential Inputs
The multi-format differential clock inputs of the Si533x will interface with today’s most common differential signals,
such as LVDS, LVPECL, CML, and HCSL. The differential inputs are internally self-biased and must be ac-coupled
externally with a 0.1 µF capacitor. The receiver will accept a signal with a voltage swing between 400 mV and
2.4 VPP differential. Each half of the differential signal must not exceed 1.2 VPP at the input to the Si533x or else
the 1.3 V dc voltage limit may be exceeded.
2.2.1. LVDS Inputs
When interfacing the Si533x device to an LVDS signal, a 100  termination is required at the input along with the
required dc blocking capacitors as shown in Figure 6.
Must be ac coupled
Keep termination close to
input pin of the Si533x
0.1 uF
Si533x
50
100
LVDS
50
0.1 uF
Figure 6. LVDS Input Signal
2.2.2. LVPECL Inputs
Since the differential receiver of the Si533x is internally self biased, an LVPECL signal may not be dc-coupled to
the device. Figure 7 shows some common LVPECL connections that should not be used because of the dc levels
they present at the receiver’s input.
Rev. 0.5
5
AN408
VDD
DC Coupled with
Thevenin Termination
R1
V DD
V DD
AC Coupled with
Thevenin Re-Biasing
R1
V DD
R1
R1
R2
R2
50
50
50
50
LVPECL
LVPECL
R2
R2
Rb
Rb
Not Recommended
Figure 7. Common LVPECL Connections that May be Destructive to the Si533x Input
Recommended configurations for interfacing an LVPECL input signal to the Si533x are shown in Figure 8. Typical
values for the bias resistors (Rb) range between 120 and 200  depending on the LVPECL driver. The 100 
resistor provides line termination. Because the receiver is internally self-biased, no additional external bias is
required.
Another solution is to terminate the LVPECL driver with a Thevenin configuration as shown in Figure 8b. The
values for R1 and R2 are calculated to provide a 50 termination to VDD-2V. Given this, the recommended resistor
values are R1 = 127 and R2 = 82.5  for VDD = 3.3 V, and R1 = 250 andR2 = 62.5 for VDD = 2.5 V.
6
Rev. 0.5
AN408
Keep termination close to
input pin of the Si533x
3.3 V, 2.5 V
0.1 uF
Si533x
50
100
50
LVPECL
Rb
0.1 uF
Rb
Must be ac coupled
Figure 8a—LVPECL Input Signal with Source Biasing Option
Keep termination close to
input pin of the Si533x
VDD
VDD
Must be ac coupled
R1
R1
VDD= 3.3 V, 2.5 V
0.1 uF
Si533x
50
50
LVPECL
0.1 uF
R2
R2
VT = VDD – 2 V
R1 // R2 = 50 Ohm
Figure 8b—LVPECL Input Signal with Load Biasing Option
Figure 8. Recommended Options for Interfacing to an LVPECL Signal
Rev. 0.5
7
AN408
2.2.3. CML Inputs
CML signals may be applied to the differential inputs of the Si533x. Since the Si533x differential inputs are
internally self-biased, a CML signal may not be dc-coupled to the device.
The recommended configurations for interfacing a CML input signal to the Si533x are shown in Figure 9. The
100  resistor provides line termination, and, since the receiver is internally-biased, no additional external biasing
components are required.
Keep termination close to
input pin of the Si533x
0.1 uF
Si533x
50
100
CML
50
0.1 uF
Must be ac coupled
Figure 9. CML Input Signal
2.2.4. Applying CMOS Level Signal to Differential Inputs
Note that the maximum voltage level on the differential input pins on all Si533x must not exceed 1.3 V. To apply a
CMOS signal to any of these pins, use the circuit shown in Figure 10. For a CMOS signal applied to these
differential inputs, the maximum recommended frequency is 200 MHz.
Keep R se and Rsh close to
the receiver
0.1 uF
Rse
CMOS Input Signal
1.8 V CMOS
Rse = 249 
Rsh = 464 
50
3.3 V CMOS
Rsh
Rse = 499 
Rsh = 274 
2.5 V CMOS
0.1 uF
Rse = 402 
Rsh = 357 
Figure 10. Applying a CMOS Level Signal to the Differential Inputs
8
Rev. 0.5
Si533x
AN408
2.2.5. HCSL Inputs
A typical HCSL driver has an open source output, which requires an external series resistor and a resistor to
ground. The values of these resistors depend on the driver but are typically equal to 33  (Rs) and 50  (Rt). Note
that the HCSL driver in the Si533x requires neither Rs nor Rt resistors. Other than two ac-coupling capacitors, no
additional external components are necessary when interfacing an HCSL signal to the Si533x.
Must be ac coupled
3.3V, 2.5V, 1.8V
0.1 uF
Rs
50
Si533x
Rs
50
HCSL
0.1 uF
Rt
Rt
Figure 11. HCSL Input Signal to Si533x
Rev. 0.5
9
AN408
3. Outputs
The Si533x devices provide four outputs that can be differential or single-ended. The Si5356/55 devices only have
CMOS outputs. When configured as single-ended, the driver generates two signals that can be configured as inphase or complimentary. Each of the outputs has its own output supply pin, allowing the device to be used in mixed
supply applications without the need for external level translators. Each output driver is configurable to support the
following signal types: CMOS/LVTTL, SSTL, HSTL, LVPECL, LVDS, and HCSL. The Si5338 also supports a CML
output driver.
3.1. CMOS/LVTTL Outputs
The CMOS output driver has a controlled impedance of about 50 , which includes an internal series resistor of
approximately 22 . For this reason, an external Rs series resistor is not recommended when driving 50  traces.
If the trace impedance is higher than 50 , a series resistor, Rs, should be used. A typical configuration is shown in
Figure 12. By default, the CMOS outputs of the driver are in-phase and can be used to drive two receivers. They
can also be configured as complimentary outputs. The output supports 3.3, 2.5, and 1.8 V CMOS signal levels
when the appropriate voltage is supplied to the external VDDO pin and the device is configured accordingly.
3.3, 2.5, or 1.8 V
VDDOx
LVTTL/
CMOS
Si533x/56/55
CLKxA
CMOS
50
CLKxB
50
Figure 12. Interfacing to a CMOS Receiver
3.1.1. 1.5 and 1.2 V CMOS Outputs
The Si533x/55/56 output drivers natively support 3.3, 2.5, and 1.8 V CMOS. However, 1.5 and 1.2 V CMOS signals
can be obtained using a two-resistor network as shown in Figure 13 and Table 1 below. Place R1 and R2 as close
to the device output as possible.
3.3V, 2.5V, or 1.8V
3.3V, 2.5V, or 1.8V
VVDDOx
DDOx
1.5 or 1.2 V
1.5 or 1.2 V
RR11
Si533x/56/55
Si533x/56/55
50
50
CLKxA
CLKxA
CMOS
CMOS
RR22
CLKxB
CLKxB
RR11
50
50
RR22
Figure 13. Interfacing to a 1.5 or 1.2 V CMOS Receiver
10
Rev. 0.5
AN408
Table 1. Resistor Values for Interfacing to 1.5 and 1.2 V Receivers
1.2 V CMOS Output
1.5 V CMOS Output
VDDOx
R1
R2
R1
R2
1.8 V
25 
150 
10 
300 
2.5 V
55 
100 
33 
125 
3.3 V
90 
80 
60 
90 
The resistor values in Table 1 were selected to maintain signal integrity, specifically rise/fall time, at the cost of
current consumption. The increase in current consumption is expected to be on the order of 2 to 8 mA per output
depending on VDDOx, 4 mA max with VDDOx of 1.8 V.
3.2. SSTL and HSTL Outputs
The Si533x supports both SSTL and HSTL outputs, which can be single-ended or differential. The recommended
termination scheme for SSTL is shown in Figure 14. The VTT supply can be generated using a simple voltage
divider as shown below.
SSTL (3.3, 2.5, or 1.8 V)
HSTL (1.5 V)
VTT VTT
VDDOx
50 
Si533x
SSTL
or
HSTL
CLKxA
50 
50
SSTL_3
SSTL_2
SSTL_18
HSTL
CLKxB
50
VDDO
R1
VTT
SSTL_2, SSTL_18, HSTL
R1 = 2k
R2 = 2k
SSTL_3
R1 = 2.43k
R2 = 2k
0.1 uF
R2
Figure 14. Interfacing the Si533x to an SSTL or HSTL Receiver
Rev. 0.5
11
AN408
3.3. LVPECL Outputs
The LVPECL driver is configurable in both 3.3 V or 2.5 V standard LVPECL modes. The output driver can be accoupled or dc-coupled to the receiver.
3.3.1. DC-Coupled LVPECL Outputs
The standard LVPECL driver supports two commonly used dc-coupled configurations. Both of these are shown in
Figure 15. LVPECL drivers were designed to be terminated with 50  to VDD–2 V, which is illustrated in
Figure 15a. VTT can be supplied with a simple voltage divider as shown in Figure 15.
An alternative method of terminating LVPECL is shown in Figure 15b, which is the Thevenin equivalent to the
termination in Figure 15a. It provides a 50  load terminated to VDD–2.0 V. For 3.3 V LVPECL, use R1 = 127 and
R2 = 82.5 ; for 2.5 V LVPECL, use R1 = 250 and R2 = 62.5 The only disadvantage to this type of termination
is that the Thevenin circuit consumes additional power from the VDDO supply.
Keep termination close to
the receiver
3.3 V, 2.5 V
VDDOx
50
Si533x
50
CLKxA
LVPECL
3.3 V LVPECL
2.5 V LVPECL
VTT
CLKxB
50
50
VDDO – 2.0 V
Figure 14a—DC Coupled Termination of 50 Ohms to VDD – 2.0 V
VDDO VDDO
3.3 V, 2.5 V
VDDOx
R1
Keep termination close to
the receiver
R1
Si533x
3.3 V LVPECL
2.5 V LVPECL
CLKxA
LVPECL
50
CLKxB
50
R2
R2
VT = VDDO – 2.0 V
R1 // R2 = 50 Ohm
3.3 V LVPECL
R1 = 127 Ohm
R2 = 82.5 Ohm
2.5 V LVPECL
R1 = 250 Ohm
R2 = 62.5 Ohm
Figure 14b—DC Coupled with Thevenin Termination
Figure 15. Interfacing the Si533x to an LVPECL Receiver Using DC Coupling
12
Rev. 0.5
AN408
3.3.2. AC Coupled LVPECL Outputs
AC coupling is necessary when a receiver and a driver have compatible voltage swings but different commonmode voltages. AC coupling works well for dc-balanced signals, such as for 50% duty cycle clocks. Figure 16
describes two methods for ac coupling the standard LVPECL driver. The Thevenin termination shown in Figure 16a
is a convenient and common approach when a VBB (VDD – 1.3 V) supply is not available; however, it does
consume additional power. The termination method shown in Figure 16b consumes less power. A VBB supply can
be generated from a simple voltage divider circuit as shown in Figure 16.
V DDO V DDO
3.3 V, 2.5 V
V DDOx
R1
Si533x
Keep termination close to
the receiver
R1
3.3 V LVPECL
2.5 V LVPECL
0.1 uF
50
CLKxA
LVPECL
CLKxB
50
0.1 uF
Rb
Rb = 130 Ohm (2.5 V LVPECL)
Rb = 200 Ohm (3.3 V LVPECL)
R2
Rb
V DDO – 1.3 V
R 1 // R 2 = 50 Ohm
R2
2.5 V LVPECL
R 1 = 62.5 Ohm
R 2 = 250 Ohm
Figure 15a—AC Coupled with Thevenin Termination
Keep termination close to
the receiver
3.3 V, 2.5 V
0.1 uF
V DDOx
50
Si533x
50
CLKxA
LVPECL
3.3 V LVPECL
R 1 = 82.5 Ohm
R 2 = 127 Ohm
3.3 V LVPECL
2.5 V LVPECL
V BB
CLKxB
0.1 uF
50
50
Rb
V DDO – 1.3 V
Rb
Rb = 130 Ohm (2.5 V LVPECL)
Rb = 200 Ohm (3.3 V LVPECL)
Figure 15b—AC Coupled with 100 Ohm Termination
Figure 16. Interfacing to an LVPECL Receiver Using AC Coupling
Rev. 0.5
13
AN408
3.4. LVDS Outputs
The LVDS output option provides a very simple and power-efficient interface that requires no external biasing when
connected to an LVDS receiver. An ac-coupled LVDS driver is often useful as a CML driver. The LVDS driver may
be dc-coupled or ac-coupled to the receiver in 3.3 V or 2.5 V output mode.
3.4.1. AC-Coupled LVDS Outputs
The Si5338/34 LVDS output can drive an ac-coupled load. The Si5330 LVDS output can only drive an ac-coupled
load if the input to the Si5330 has a very well-controlled duty cycle like any Silicon Labs PLL clock products. The ac
coupling capacitors may be placed at either the driver or receiver end, as long as they are placed prior to the 100 
termination resistor. Keep the 100  termination resistor as close to the receiver as possible, as shown in
Figure 17. When a 1.8 V output supply voltage is used, the LVDS output of the Si533x produces a common-mode
voltage of ~0.875 V, which does not support the LVDS standard. In this case, it is best to ac-couple the output to
the load.
Keep termination close to
the receiver
3.3 V or 2.5 V
VDDOx
Si533x
50
LVDS
CLKxA
LVDS
100
CLKxB
50
16a—DC-Coupled LVDS Output
Keep termination close to
the receiver
3.3V, 2.5V, or 1.8V
VDDOx
0.1 uF
Si533x
50
CLKxA
LVDS
100
CLKxB
50
0.1 uF
16b—AC-Coupled LVDS Output
Figure 17. Interfacing to an LVDS Receiver
14
Rev. 0.5
AN408
3.5. HCSL Outputs
Host clock signal level (HCSL) outputs are commonly used in PCI Express applications. A typical HCSL driver has
an open source output that requires an external series resistor and a resistor to ground. The Si533x HCSL driver
has integrated these resistors to simplify the interface to an HCSL receiver. No external components are necessary
when connecting the Si533x HCSL driver to an HCSL receiver.
3.3, 2.5, or 1.8 V
VDDOx
Rs
50
HCSL
CLKxA
HCSL
CLKxB
Rs
50
Rt
Rt
Si533x
Figure 18. Interfacing the Si533x to an HCSL Receiver
3.6. CML Outputs
The Si5338 has a CML driver option. This driver can be used to replace an LVPECL driver in ac-coupled
applications and save ~15 mA for each output driver in the process. When using the CML driver, no external bias
resistors from the CML outputs to ground or Vtt should be connected. The CML driver is compliant with LVPECL
peak-peak output levels; however, the common-mode output voltage is not compliant to LVPECL specs. The CML
driver is individually available for all four differential outputs. See Section 9 of “AN411: Configuring the Si5338
without ClockBuilder Desktop” for information on selecting the CML Driver option. The CML output driver option
should only be used when the output clock signal comes from an internal MultiSynth.
The Si5338 CML output driver can be used as long as the following conditions are met:
1. Both pins of the differential output pair are ac coupled to the load.
2. The load at the receiver is effectively 100  differential.
3. The Si5338 PLL is not bypassed.
4. The VDDOx supply for the CML driver voltage is 3.3 V or 2.5 V.
The CML driver has the same specified output voltage swing as the LVPECL driver.
1. Max Vsepp = .95 V
2. Min Vsepp = .55 V
3. Typ Vsepp = .8 V
Figure 19 shows the normal connection for the Si5338 CML Driver format. Figure 20 shows the expected
termination for the Si5338 CML driver. This termination is most often within a CML receiver.
Rev. 0.5
15
AN408
Si5338 CML
Driver
50 
+
Receiver
Do Not use
external bias
resistors
-
50 
Do Not use
external bias
resistors
Figure 19. CML Driver Connection
Si5338 CML
Driver
Effective Termination
+
50 
50 
Vbias
50 
-
50 
Vbias can be any voltage with
any source impedance
Figure 20. Terminations for Si5338 CML Driver
16
Rev. 0.5
AN408
3.7. Interfacing the Si533x LVDS/LVPECL to a CML Receiver
Current mode logic (CML) is transmitted differentially and terminated to 50  to Vcc as shown in Figure 21. A CML
receiver can be driven with either an LVPECL or an LVDS output depending on the signal swing required by the
receiver. A single-ended output swing from 550 mV to 960 mV is achieved when driving a CML receiver with an
LVPECL output. For a reduced output swing, LVDS mode is recommended for producing a single-ended swing
between 250 mV and 450 mV.
Driving a CML Receiver Using the LVPECL Output
550 mV – 960 mV p-p
Si533x
CML
Receiver
0.1 uF
50
50
Vcc
0.1 uF
LVPECL
50
50
Rb
Rb
Rb = 130 Ohms (2.5 V LVPECL)
Rb = 200 Ohms (3.3 V LVPECL)
Driving a CML Receiver Using the LVDS Output
Si533x
CML
Receiver
250 mV - 450 mV p-p
0.1 uF
50
50
0.1 uF
LVDS
Vcc
50
50
Figure 21. Terminating an LVPECL or an LVDS Output to a CML Receiver
Rev. 0.5
17
AN408
DOCUMENT CHANGE LIST
Revision 0.3 to 0.4

Updated Section 3.5.
Revision 0.4 to 0.5

Updated Figure 10 on page 8.
Updated

resistor values.
Updated "2.2.4. Applying CMOS Level Signal to
Differential Inputs" on page 8.
Added
text to recomend max CMOS input frequency
into a differential input.





18
Updated "2.1.2. Single-Ended SSTL and HSTL
Inputs" on page 4 and "2.1.3. Applying a SingleEnded Signal to a Differential Input" on page 5 to
specify a max input frequency of 350 MHz.
Removed R1 and R2 and 0.1 µf cap from Figures 15
and 16.
Added maximum input frequency of 350 MHz to
"2.1.2. Single-Ended SSTL and HSTL Inputs" on
page 4 and "2.1.3. Applying a Single-Ended Signal
to a Differential Input" on page 5.
Added "3.6. CML Outputs" on page 15.
Added "3.1.1. 1.5 and 1.2 V CMOS Outputs" on
page 10.
Rev. 0.5
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