Differential-to-HSTL Zero Delay Clock
Generator
ICS8725B-01
DATA SHEET
General Description
Features
The ICS8725B-01 is a highly versatile 1:5 Differentialto-HSTL clock generator and a member of the
HiPerClockS™
HiPerClockS™ family of High Performance Clock
Solutions from IDT. The ICS8725B-01 has a fully
integrated PLL and can be configured as zero delay
buffer, multiplier or divider, and has an output frequency range of
31.25MHz to 700MHz. The reference divider, feedback divider and
output divider are each programmable, thereby allowing for the
following output-to-input frequency ratios: 8:1, 4:1, 2:1, 1:1, 1:2, 1:4,
1:8. The external feedback allows the device to achieve “zero delay”
between the input clock and the output clocks. The PLL_SEL pin can
be used to bypass the PLL for system test and debug purposes. In
bypass mode, the reference clock is routed around the PLL and into
the internal output dividers.
•
•
•
Five differential HSTL output pairs
•
•
•
•
Output frequency range: 31.25MHz to 700MHz
•
Programmable dividers allow for the following output-to-input
frequency ratios: 8:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:8
•
•
•
•
•
•
Static phase offset: 15ps ± 135ps
ICS
Block Diagram
VCO range: 250MHz to 700MHz
External feedback for “zero delay” clock regeneration
with configurable frequencies
Cycle-to-cycle jitter: 25ps (maximum)
Output skew: 45ps (maximum)
3.3V core, 1.8V output operating supply
0°C to 70°C ambient operating temperature
Available in both standard (RoHS 5) and lead-free (RoHS 6)
packages
VDDO
nQ4
Q4
GND
SEL3
PLL_SEL
Q3
CLK0
3
22
nQ3
nCLK0
4
21
Q2
CLK1
5
20
nQ2
nCLK1
6
19
Q1
CLK_SEL
7
18
nQ1
MR
8
17
VDDO
9
10 11 12 13 14 15 16
VDDO
SEL0
23
Q0
8:1, 4:1, 2:1, 1:1
1:2, 1:4, 1:8
VDDO
2
nQ0
Q4
nQ4
24
SEL1
GND
PLL
1
SEL2
Q3
nQ3
1
SEL0
FB_IN
0
32 31 30 29 28 27 26 25
Q2
nQ2
nFB_IN
0
VDDA
VDD
Q1
nQ1
VDD
÷1, ÷2, ÷4, ÷8
÷16, ÷32, ÷64
CLK_SEL
FB_IN
nFB_IN
Input frequency range: 31.25MHz to 700MHz
Q0
nQ0
1
CLK1
nCLK1
CLKx/nCLKx pairs can accept the following differential
input levels: LVPECL, LVDS, HSTL, HCSL, SSTL
Pin Assignment
PLL_SEL
CLK0
nCLK0
Selectable differential CLKx/nCLKx input pairs
SEL1
ICS8725B-01
SEL2
32-Lead LQFP
7mm x 7mm x 1.4mm package body
Y Package
Top View
SEL3
MR
ICS8725BY-01 REVISION A JULY 16, 2009
1
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Table 1. Pin Descriptions
Number
Name
1, 2,
12, 29
SEL0, SEL1,
SEL2, SEL3
Type
Description
Input
Pulldown
Determines output divider values in Table 3. LVCMOS / LVTTL interface levels.
3
CLK0
Input
Pulldown
Non-inverting differential clock input.
4
nCLK0
Input
Pullup
Inverting differential clock input.
5
CLK1
Input
Pulldown
6
nCLK1
Input
Pullup
Non-inverting differential clock input.
7
CLK_SEL
Input
Pulldown
Clock select input. When HIGH, selects CLK1, nCLK1. When LOW, selects CLK0,
nCLK0. LVCMOS/LVTTL interface levels.
Pulldown
Active HIGH Master Reset. When logic HIGH, the internal dividers are reset
causing the true outputs Qx to go low and the inverted outputs nQx to go high.
When logic LOW, the internal dividers and the outputs are enabled. LVCMOS /
LVTTL interface levels.
Inverting differential clock input.
8
MR
Input
9, 32
VDD
Power
10
nFB_IN
Input
Pullup
Inverting differential feedback input to phase detector for regenerating clocks with
“Zero Delay.”
11
FB_IN
Input
Pulldown
Non-inverted differential feedback input to phase detector for regenerating clocks
with “Zero Delay.”
13, 28
GND
Power
Power supply ground.
14, 15
nQ0, Q0
Output
Differential output pair. HSTL interface levels.
16, 17, 24,
25
VDDO
Power
Output supply pins.
18, 19
nQ1, Q1
Output
Differential output pair. HSTL interface levels.
20, 21
nQ2, Q2
Output
Differential output pair. HSTL interface levels.
22, 23
nQ3, Q3
Output
Differential output pair. HSTL interface levels.
26, 27
nQ4, Q4
Output
Differential output pair. HSTL interface levels.
30
VDDA
Power
Analog supply pin.
31
PLL_SEL
Input
Core supply pins.
Pullup
PLL select. Selects between the PLL and reference clock as the input to the
dividers. When LOW, selects reference clock. When HIGH, selects PLL.
LVCMOS/LVTTL interface levels.
NOTE: Pullup and Pulldown refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
Table 2. Pin Characteristics
Symbol
Parameter
CIN
Input Capacitance
2
pF
RPULLUP
Input Pullup Resistor
51
kΩ
RPULLDOWN
Input Pulldown Resistor
51
kΩ
ICS8725BY-01 REVISION A JULY 16, 2009
Test Conditions
2
Minimum
Typical
Maximum
Units
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Function Tables
Table 3A. Control Input Function Table
Inputs
Outputs
PLL_SEL = 1
PLL Enable Mode
SEL3
SEL2
SEL1
SEL0
Reference Frequency Range (MHz)*
Q[0:4], nQ[0:4]
0
0
0
0
250 - 700
÷1
0
0
0
1
125 - 350
÷1
0
0
1
0
62.5 - 175
÷1
0
0
1
1
31.25 - 87.5
÷1
0
1
0
0
250 - 700
÷2
0
1
0
1
125 - 350
÷2
0
1
1
0
62.5 - 175
÷2
0
1
1
1
250 - 700
÷4
1
0
0
0
125 - 350
÷4
1
0
0
1
250 - 700
÷8
1
0
1
0
125 - 350
x2
1
0
1
1
62.5 - 175
x2
1
1
0
0
31.25 - 87.5
x2
1
1
0
1
62.5 - 175
x4
1
1
1
0
31.25 - 87.5
x4
1
1
1
1
31.25 - 87.5
x8
*NOTE: VCO frequency range for all configurations above is 250MHz to 700MHz.
ICS8725BY-01 REVISION A JULY 16, 2009
3
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Table 3B. PLL Bypass Function Table
Inputs
Outputs
PLL_SEL = 0
PLL Bypass Mode
SEL3
SEL2
SEL1
SEL0
Q[0:4], nQ[0:4]
0
0
0
0
÷4
0
0
0
1
÷4
0
0
1
0
÷4
0
0
1
1
÷8
0
1
0
0
÷8
0
1
0
1
÷8
0
1
1
0
÷16
0
1
1
1
÷16
1
0
0
0
÷32
1
0
0
1
÷64
1
0
1
0
÷2
1
0
1
1
÷2
1
1
0
0
÷4
1
1
0
1
÷1
1
1
1
0
÷2
1
1
1
1
÷1
ICS8725BY-01 REVISION A JULY 16, 2009
4
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Absolute Maximum Ratings
NOTE: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
These ratings are stress specifications only. Functional operation of product at these conditions or any conditions beyond
those listed in the DC Characteristics or AC Characteristics is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect product reliability.
Item
Rating
Supply Voltage, VDD
4.6V
Inputs, VI
-0.5V to VDD + 0.5V
Outputs, VO
-0.5V to VDDO + 0.5V
Package Thermal Impedance, θJA
47.9°C/W (0 lfpm)
Storage Temperature, TSTG
-65°C to 150°C
DC Electrical Characteristics
Table 4A. Power Supply DC Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
Parameter
VDD
Test Conditions
Minimum
Typical
Maximum
Units
Core Supply Voltage
3.135
3.3
3.465
V
VDDA
Analog Supply Voltage
3.135
3.3
3.465
V
VDDO
Output Supply Voltage
1.6
1.8
2.0
V
IDD
Power Supply Current
135
mA
IDDA
Analog Supply Current
16
mA
IDDO
Output Supply Current
0
mA
Table 4B. LVCMOS/LVTTL DC Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
Parameter
VIH
Input High Voltage
VIL
Input Low Voltage
IIH
IIL
Input High Current
Input Low Current
Test Conditions
Minimum
Typical
Maximum
Units
2
VDD + 0.3
V
-0.3
0.8
V
CLK_SEL,
SEL[0:3], MR
VDD = VIN = 3.465V
150
µA
PLL_SEL
VDD = VIN = 3.465V
5
µA
CLK_SEL,
SEL[0:3], MR
VDD = 3.465V, VIN = 0V
-5
µA
PLL_SEL
VDD = 3.465V, VIN = 0V
-150
µA
ICS8725BY-01 REVISION A JULY 16, 2009
5
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Table 4C. Differential DC Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
IIH
IIL
Parameter
Test Conditions
Minimum
Typical
Maximum
Units
FB_IN,
CLK0, CLK1
VDD = VIN = 3.465V
150
µA
nFB_IN,
nCLK0, nCLK1
VDD = VIN = 3.465V
5
µA
Input High Current
FB_IN,
CLK0, CLK1
VDD = 3.465V, VIN = 0V
-5
µA
nFB_IN,
nCLK0, nCLK1
VDD = 3.465V, VIN = 0V
-150
µA
Input Low Current
VPP
Peak-to-Peak Voltage; NOTE 1
0.15
1.3
V
VCMR
Common Mode Input Voltage; NOTE 1, 2
0.5
VDD – 0.85
V
Maximum
Units
NOTE 1: VIL should not be less than -0.3V.
NOTE 2: Common mode input voltage is defined as VIH.
Table 4D. HSTL DC Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
Parameter
Test Conditions
Minimum
Typical
VOH
Output High Voltage; NOTE 1
1.0
1.4
V
VOL
Output Low Voltage; NOTE 1
0
0.4
V
VOX
Output Crossover Voltage; NOTE 2
40
60
%
VSWING
Peak-to-Peak Output Voltage Swing
0.6
1.1
V
NOTE 1: Outputs terminated with 50Ω to ground.
NOTE 2: Defined with respect to output voltage swing at a given condition.
Table 5. Input Frequency Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
Parameter
FIN
Input Frequency
CLK0, nCLK0,
CLK1, nCLK1
ICS8725BY-01 REVISION A JULY 16, 2009
Test Conditions
Minimum
PLL_SEL = 1
31.25
PLL_SEL = 0
6
Typical
Maximum
Units
700
MHz
700
MHz
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
AC Electrical Characteristics
Table 6. AC Characteristics, VDD = 3.3V ± 5%, VDDO = 1.8V ± 0.2V, TA = 0°C to 70°C
Symbol
Parameter
fMAX
Output Frequency
tPD
Propagation Delay; NOTE 1
tsk(Ø)
Static Phase Offset; NOTE 2, 5
tsk(o)
Output Skew; NOTE 3, 5
tjit(cc)
Test Conditions
Minimum
PLL_SEL = 0V, f ≤ 700MHz
3.2
PLL_SEL = 3.3V
-120
Typical
Maximum
Units
700
MHz
4.4
ns
150
ps
45
ps
Cycle-to-Cycle Jitter; NOTE 5, 6
25
ps
tjit(θ)
Phase Jitter; NOTE 4, 5, 6
±50
ps
tL
PLL Lock Time
1
ms
tR / tF
Output Rise/Fall Time
700
ps
tPW
Output Pulse Width
tPERIOD/2 + 85
ps
15
PLL_SEL = 0V
20% to 80% @ 50MHz
300
tPERIOD/2 - 85
tPERIOD/2
NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is
mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium
has been reached under these conditions.
NOTE 1: Measured from the differential input crossing point to the differential output crossing point.
NOTE 2: Defined as the time difference between the input reference clock and the averaged feedback input signal across all conditions, when
the PLL is locked and the input reference frequency is stable.
NOTE 3: Defined as skew between outputs at the same supply voltage and with equal load conditions. Measured at the output differential
cross points.
NOTE 4: Phase jitter is dependent on the input source used.
NOTE 5: This parameter is defined in accordance with JEDEC Standard 65.
NOTE 6: Characterized at VCO frequency of 622MHz.
ICS8725BY-01 REVISION A JULY 16, 2009
7
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Parameter Measurement Information
3.3V±5%
1.8V±0.2V
VDD
VDD,
VDDA
Qx
SCOPE
nCLK0, nCLK1
VDDO
V
Cross Points
PP
HSTL
V
CMR
CLK0, CLK1
nQx
GND
GND
0V
Differential Input Level
3.3V Core/1.8V Output Load AC Test Circuit
nCLK0, nCLK1
VOH
CLK0, CLK1
VOL
nFB_IN
nQx
Qx
VOH
VOL
FB_IN
nQy
➤
➤ t(Ø)
tjit(Ø) = t(Ø) – t(Ø) mean= Phase Jitter
t(Ø) mean = Static Phase Offset
Qy
tsk(o)
Where t(Ø) is any random sample, and t(Ø) mean is the average
of the sampled cycles measured on the controlled edges)
Output Skew
Phase Jitter and Static Phase Offset
nQ[0:4]
nQ[0:4]
Q[0:4]
Q[0:4]
t PW
➤
tcycle n
➤
tcycle n+1
t
➤
➤
tjit(cc) = |tcycle n – tcycle n+1|
1000 Cycles
odc =
PERIOD
t PW
x 100%
t PERIOD
Cycle-to-Cycle Jitter
ICS8725BY-01 REVISION A JULY 16, 2009
Output Duty Cycle/Pulse Width/Period
8
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Parameter Measurement Information, continued
nCLK0,
nCLK1
nQ[0:4]
80%
80%
VOX
Q[0:4]
CLK0,
CLK1
VSW I N G
nQ[0:4]
20%
20%
tR
tF
Q[0:4]
tPD
Propagation Delay
Output Rise/Fall Time
Application Information
Power Supply Filtering Technique
To achieve optimum jitter performance, power supply isolation is
required. To achieve optimum jitter performance, power supply
isolation is required. The ICS8725B-01 provides separate power
supplies to isolate any high switching noise from the outputs to the
internal PLL. VDD, VDDA and VDDO should be individually connected
to the power supply plane through vias, and 0.01µF bypass
capacitors should be used for each pin. Figure 1 illustrates this for a
generic VDD pin and also shows that VDDA requires that an additional
10Ω resistor along with a 10µF bypass capacitor be connected to the
VDDA pin. The 10Ω resistor can also be replaced by a ferrite bead.
ICS8725BY-01 REVISION A JULY 16, 2009
3.3V
VDD
.01µF
10Ω
.01µF
10µF
VDDA
Figure 1. Power Supply Filtering
9
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Recommendations for Unused Input Pins
Inputs:
Outputs:
LVCMOS Control Pins
HSTL OUTPUTS
All control pins have internal pullups or pulldowns; additional
resistance is not required but can be added for additional protection.
A 1kΩ resistor can be used.
All unused HSTL outputs can be left floating. We recommend that
there is no trace attached. Both sides of the differential output pair
should either be left floating or terminated.
CLK/nCLK Inputs
For applications not requiring the use of the differential input, both
CLK and nCLK can be left floating. Though not required, but for
additional protection, a 1kΩ resistor can be tied from CLK to ground.
Wiring the Differential Input to Accept Single Ended Levels
Figure 2 shows how the differential input can be wired to accept
single ended levels. The reference voltage V_REF = VDD/2 is
generated by the bias resistors R1, R2 and C1. This bias circuit
should be located as close as possible to the input pin. The ratio of
R1 and R2 might need to be adjusted to position the V_REF in the
center of the input voltage swing. For example, if the input clock swing
is only 2.5V and VDD = 3.3V, V_REF should be 1.25V and R2/R1 =
0.609.
VDD
R1
1K
CLK_IN
+
V_REF
-
C1
0.1uF
R2
1K
Figure 2. Single-Ended Signal Driving Differential Input
ICS8725BY-01 REVISION A JULY 16, 2009
10
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Differential Clock Input Interface
The CLK /nCLK accepts LVDS, LVPECL, LVHSTL, SSTL, HCSL and
other differential signals. Both VSWING and VOH must meet the VPP
and VCMR input requirements. Figures 3A to 3F show interface
examples for the HiPerClockS CLK/nCLK input driven by the most
common driver types. The input interfaces suggested here are
examples only. Please consult with the vendor of the driver
component to confirm the driver termination requirements. For
example, in Figure 3A, the input termination applies for IDT
HiPerClockS open emitter LVHSTL drivers. If you are using an
LVHSTL driver from another vendor, use their termination
recommendation.
3.3V
3.3V
3.3V
1.8V
Zo = 50Ω
Zo = 50Ω
CLK
CLK
Zo = 50Ω
nCLK
Zo = 50Ω
nCLK
HiPerClockS
Input
LVHSTL
R1
50
IDT
HiPerClockS
LVHSTL Driver
HiPerClockS
Input
LVPECL
R2
50
R1
50
R2
50
R2
50
Figure 3A. HiPerClockS CLK/nCLK Input
Driven by an IDT Open Emitter
HiPerClockS LVHSTL Driver
Figure 3B. HiPerClockS CLK/nCLK Input
Driven by a 3.3V LVPECL Driver
3.3V
3.3V
3.3V
R3
125
3.3V
R4
125
3.3V
Zo = 50Ω
Zo = 50Ω
CLK
CLK
R1
100
Zo = 50Ω
nCLK
HiPerClockS
Input
LVPECL
R1
84
R2
84
Figure 3C. HiPerClockS CLK/nCLK Input
Driven by a 3.3V LVPECL Driver
2.5V
nCLK
Zo = 50Ω
Receiver
LVDS
Figure 3D. HiPerClockS CLK/nCLK Input
Driven by a 3.3V LVDS Driver
2.5V
3.3V
3.3V
2.5V
*R3
33
R3
120
Zo = 50Ω
R4
120
Zo = 60Ω
CLK
CLK
Zo = 50Ω
Zo = 60Ω
nCLK
nCLK
HCSL
*R4
33
R1
50
R2
50
HiPerClockS
Input
HiPerClockS
SSTL
R1
120
R2
120
*Optional – R3 and R4 can be 0Ω
Figure 3F. HiPerClockS CLK/nCLK Input
Driven by a 2.5V SSTL Driver
Figure 3E. HiPerClockS CLK/nCLK Input
Driven by a 3.3V HCSL Driver
ICS8725BY-01 REVISION A JULY 16, 2009
11
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Schematic Example
The schematic of the ICS8725B-01 layout example is shown in
Figure 4A. The ICS8725B-01 recommended PCB board layout for
this example is shown in Figure 4B. This layout example is used as a
general guideline. The layout in the actual system will depend on the
selected component types, the density of the components, the
density of the traces, and the stacking of the P.C. board.
VDD
SP = Spare (i.e. not installed)
RU2
SP
RU3
1K
RU4
1K
RU5
SP
RU6
1K
RD6
SP
RD7
1K
VDD
Zo = 50 Ohm
+
SEL3
RD5
1K
(77.76 MHz)
PLL_SEL
RD4
SP
C16
10u
VDD
VDDO
VDDO
-
LVHSTL_input
Zo = 50 Ohm
(155.52 MHz)
Zo = 50 Ohm
CLK_SEL
3.3V PECL Driv er
R8
50
R9
50
1
2
3
4
5
6
7
8
SEL0
SEL1
CLK0
nCLK0
CLK1
nCLK1
CLK_SEL
MR
U1
ICS8725B-01
R10
50
VDD
nFB_IN
FB_IN
SEL2
GND
nQ0
Q0
VDDO
SEL0
SEL1
Zo = 50 Ohm
R4A
50
R4B
50
24
23
22
21
20
19
18
17
VDDO
Q3
nQ3
Q2
nQ2
Q1
nQ1
VDDO
VDD=3.3V
VDDO=1.8V
9
10
11
12
13
14
15
16
3.3V
VDD
PLL_SEL
VDDA
SEL3
GND
Q4
nQ4
VDDO
32
31
30
29
28
27
26
25
RD3
SP
VDD
10
C11
0.01u
CLK_SEL
PLL_SEL
SEL0
SEL1
SEL2
SEL3
RD2
1K
R7
VDDA
RU7
SP
SEL[3:0] = 0101,
Divide by 2
SEL2
R2B
50
R2A
50
Bypass capacitors located near the power pins
VDD
(U1-9) VDD
C1
0.1uF
(U1-32)
C6
0.1uF
VDDO
VDDO
(U1-16)
C2
0.1uF
(U1-17)
C4
0.1uF
(U1-24)
C5
0.1uF
(U1-25)
C7
0.1uF
Figure 4. ICS8725B-01 HSTL Zero Delay Buffer Schematic Example
ICS8725BY-01 REVISION A JULY 16, 2009
12
©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
The following component footprints are used in this layout example:
All the resistors and capacitors are size 0603.
location. While routing the traces, the clock signal traces should be
routed first and should be locked prior to routing other signal traces.
Power and Grounding
• The differential 50Ω output traces should have same length.
Place the decoupling capacitors C1, C6, C2, C4, C5, and C7 as close
as possible to the power pins. If space allows, placement of the
decoupling capacitor on the component side is preferred. This can
reduce unwanted inductance between the decoupling capacitor and
the power pin caused by the via.
• Avoid sharp angles on the clock trace. Sharp angle turns
cause the characteristic impedance to change on the
transmission lines.
• Keep the clock traces on the same layer. Whenever possible,
avoid placing vias on the clock traces. Placement of vias on
the traces can affect the trace characteristic impedance and
hence degrade signal integrity.
Maximize the power and ground pad sizes and number of vias
capacitors. This can reduce the inductance between the power and
ground planes and the component power and ground pins.
• To prevent cross talk, avoid routing other signal traces in
parallel with the clock traces. If running parallel traces is
unavoidable, allow a separation of at least three trace widths
between the differential clock trace and the other signal trace.
The RC filter consisting of R7, C11, and C16 should be placed as
close to the VDDA pin as possible.
Clock Traces and Termination
Poor signal integrity can degrade the system performance or cause
system failure. In synchronous high-speed digital systems, the clock
signal is less tolerant to poor signal integrity than other signals. Any
ringing on the rising or falling edge or excessive ring back can cause
system failure. The shape of the trace and the trace delay might be
restricted by the available space on the board and the component
• Make sure no other signal traces are routed between the
clock trace pair.
The matching termination resistors should be located as close to the
receiver input pins as possible.
GND
R7
C16
C11
C7
VDDO
C6
C5
VDD
U1
Pin 1
VDDA
VIA
50 Ohm
Traces
C4
C1
C2
Figure 4B. PCB Board Layout for ICS8725B-01
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Power Considerations
This section provides information on power dissipation and junction temperature for the ICS8725B-01.
Equations and example calculations are also provided.
1.
Power Dissipation.
The total power dissipation for the ICS8725B-01 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for VDD = 3.3V + 5% = 3.465V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
•
Power (core)MAX = VDD_MAX * (IDD_MAX + IDDA_MAX)= 3.465V * (135mA + 16mA) = 523.215mW
•
Power (outputs)MAX = 32.8mW/Loaded Output pair
If all outputs are loaded, the total power is 5 * 32.8mW = 164mW
Total Power_MAX (3.465V, with all outputs switching) = 523.215mW + 164mW = 687.215mW
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the device. The
maximum recommended junction temperature for HiPerClockS devices is 125°C.
The equation for Tj is as follows: Tj = θJA * Pd_total + TA
Tj = Junction Temperature
θJA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
TA = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θJA must be used. Assuming no air flow and
a multi-layer board, the appropriate value is 47.9°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
70°C + 0.687W * 47.9°C/W = 102.9°C. This is well below the limit of 125°C.
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow and the type of
board (multi-layer).
Table 7. Thermal Resistance θJA for 32 Lead LQFP, Forced Convection
θJA vs. Air Flow
Linear Feet per Minute
0
200
500
Single-Layer PCB, JEDEC Standard Test Boards
67.8°C/W
55.9°C/W
50.1°C/W
Multi-Layer PCB, JEDEC Standard Test Boards
47.9°C/W
42.1°C/W
39.4°C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
HSTL output driver circuit and termination are shown in Figure 5.
VDD
Q1
VOUT
RL
50Ω
Figure 5. HSTL Driver Circuit and Termination
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load.
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = (VOH_MAX /RL) * (VDDO_MAX - VOH_MAX)
Pd_L = (VOL_MAX /RL) * (VDDO_MAX - VOL_MAX)
Pd_H = (1.0V/50Ω) * (2V - 1.0V) = 20mW
Pd_L = (0.4V/50Ω) * (2V - 0.4V) = 12.8mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32.8mW
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Reliability Information
Table 8. θJA vs. Air Flow Table for a 32 Lead LQFP
θJA vs. Air Flow
Linear Feet per Minute
0
200
500
Single-Layer PCB, JEDEC Standard Test Boards
67.8°C/W
55.9°C/W
50.1°C/W
Multi-Layer PCB, JEDEC Standard Test Boards
47.9°C/W
42.1°C/W
39.4°C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
Transistor Count
The transistor count for ICS8725B-01 is: 2969
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Package Outline and Dimensions
Package Outline - Y Suffix for 32 Lead LQFP
Table 9. Package Dimensions for 32 Lead LQFP
JEDEC Variation: BBA
All Dimensions in Millimeters
Symbol
Minimum
Nominal
Maximum
N
32
A
1.60
A1
0.05
0.15
A2
1.35
1.40
1.45
b
0.30
0.37
0.45
c
0.09
0.20
D&E
9.00 Basic
D1 & E1
7.00 Basic
D2 & E2
5.60 Ref.
e
0.80 Basic
L
0.45
0.60
0.75
θ
0°
7°
ccc
0.10
Reference Document: JEDEC Publication 95, MS-026
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
Ordering Information
Table 10. Ordering Information
Part/Order Number
8725BY-01
8725BY-01T
8725BY-01LF
8725BY-01LFT
Marking
ICS8725BY-01
ICS8725BY-01
ICS8725BY01L
ICS8725BY01L
Package
32 Lead LQFP
32 Lead LQFP
“Lead-Free” 32 Lead LQFP
“Lead-Free” 32 Lead LQFP
Shipping Packaging
Tray
1000 Tape & Reel
Tray
1000 Tape & Reel
Temperature
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
NOTE: Parts that are ordered with an "LF" suffix to the part number are the Pb-Free configuration and are RoHS compliant.
ICS8725BY-01 REVISION A JULY 16, 2009
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©2009 Integrated Device Technology, Inc.
ICS8725B-01 Data Sheet
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San Jose, California 95138
DIFFERENTIAL-TO-HSTL ZERO DELAY CLOCK GENERATOR
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