IDT ICS844256BGLFT

PRELIMINARY
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
GENERAL DESCRIPTION
FEATURES
The ICS844256 is a Cr ystal-to-LVDS Clock
Synthesizer/Fanout Buffer designed for SONET
HiPerClockS™
and Gigabit Ether net applications and is a
member of the HiperClockS™ family of High
Perfor mance Clock Solutions from IDT. The
output frequency can be set using the frequency select
pins and a 25MHz crystal for Ethernet frequencies, or a
19.44MHz crystal for SONET. The low phase noise characteristics of the ICS844256 make it an ideal clock for these
demanding applications.
• Six LVDS outputs
ICS
• Crystal oscillator interface
• Output frequency range: 62.5MHz to 622.08MHz
• Crystal input frequency range: 15.625MHz to 25.5MHz
• RMS phase jitter at 125MHz, using a 25MHz crystal
(1.875MHz to 20MHz): 0.48ps (typical)
• Full 3.3V or 3.3V core, 2.5V output supply mode
• 0°C to 70°C ambient operating temperature
• Available in both standard (RoHS 5) and lead-free (RoHS 6)
packages
SELECT FUNCTION TABLE
Inputs
Function
FB_SEL
N_SEL1
N_SEL0
M Divide
N Divide
M/N
0
0
0
25
1
25
0
0
1
25
2
12.5
0
1
0
25
4
6.25
0
1
1
25
5
5
1
0
0
32
1
32
1
0
1
32
2
16
1
1
0
32
4
8
1
1
1
32
8
4
BLOCK DIAGRAM
PIN ASSIGNMENT
Q0
nQ0
PLL_BYPASS
Pullup
Q1
1
XTAL_IN
OSC
PLL
0
nQ1
Output
Divider
XTAL_OUT
nQ2
Feedback
Divider
FB_SEL
N_SEL1
N_SEL0
Q2
VDDO
VDDO
nQ2
Q2
nQ1
Q1
nQ0
Q0
PLL_BYPASS
VDDA
VDD
FB_SEL
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
Q3
nQ3
Q4
nQ4
Q5
nQ5
N_SEL1
GND
GND
N_SEL0
XTAL_OUT
XTAL_IN
Q3
ICS844256
nQ3
24-Lead TSSOP, E-Pad
4.40mm x 7.8mm x 0.90mm
body package
G Package
Top View
Pulldown
Q4
Pullup
nQ4
Pullup
Q5
nQ5
The Preliminary Information presented herein represents a product in pre-production. The noted characteristics are based on initial product characterization
and/or qualification. Integrated Device Technology, Incorporated (IDT) reserves the right to change any circuitry or specifications without notice.
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
TABLE 1. PIN DESCRIPTIONS
Number
Name
1, 2
VDDO
3, 4
5, 6
Type
Description
Power
Output supply pins.
nQ2, Q2
Output
Differential output pair. LVDS interface levels.
nQ1, Q1
Output
Differential output pair. LVDS interface levels.
7, 8
nQ0, Q0
Output
9
PLL_BYPASS
Input
10
VDDA
Power
Differential output pair. LVDS interface levels.
Selects between the PLL and crystal inputs as the input to the dividers.
When LOW, selects PLL. When HIGH, selects XTAL_IN, XTAL_OUT.
LVCMOS / LVTTL interface levels.
Analog supply pin.
11
VDD
Power
Core supply pin.
12
13,
14
15,
18
16, 17
FB_SEL
XTAL_IN,
XTAL_OUT
N_SEL0
N_SEL1
GND
Input
19, 20
nQ5, Q5
Output
Differential output pair. LVDS interface levels.
21, 22
nQ4, Q4
Output
Differential output pair. LVDS interface levels.
23, 24
nQ3, Q3
Output
Differential output pair. LVDS interface levels.
Input
Input
Pullup
Pulldown Feedback frequency select pin. LVCMOS/LVTTL interface levels.
Crystal oscillator interface. XTAL_IN is the input.
XTAL_OUT is the output.
Pullup
Output frequency select pin. LVCMOS/LVTTL interface levels.
Power supply ground.
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
Test Conditions
4
pF
RPULLUP
Input Pullup Resistor
51
kΩ
RPULLDOWN
Input Pulldown Resistor
51
kΩ
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
2
Minimum
Typical
Maximum
Units
ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
CRYSTAL FUNCTION TABLE
Inputs
XTAL (MHz)
FB_SEL
Function
N_SEL1
N_SEL0
M
VCO (MHz)
N
Output (MHz)
20
0
0
0
25
500
1
500
20
0
0
1
25
500
2
250
20
0
1
0
25
500
4
125
20
0
1
1
25
500
5
100
21.25
0
1
1
25
531.25
5
106.25
24
0
0
0
25
600
1
600
24
0
0
1
25
600
2
300
24
0
1
0
25
60 0
4
150
24
0
1
1
25
60 0
5
12 0
25
0
0
0
25
625
1
625
25
0
0
1
25
625
2
312.5
25
0
1
0
25
625
4
156.25
25
0
1
1
25
625
5
12 5
25.5
0
1
0
25
637.5
4
159.375
15.625
1
1
1
32
500
8
62.5
18.5625
1
1
1
32
594
8
74.25
18.75
1
0
0
32
600
1
600
18.75
1
0
1
32
600
2
300
18.75
1
1
0
32
600
4
150
18.75
1
1
1
32
600
8
75
19.44
1
0
0
32
622.08
1
622.08
19.44
1
0
1
32
622.08
2
311.04
19.44
1
1
0
32
622.08
4
155.52
19.44
1
1
1
32
622.08
8
77.76
19.53125
1
0
0
32
625
1
625
19.53125
1
0
1
32
625
2
312.5
19.53125
1
1
0
32
625
4
156.25
19.53125
1
1
1
32
62 5
8
78.125
20
1
1
1
32
640
8
80
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VDD
4.6V
Inputs, VI
-0.5V to VDD + 0.5V
Outputs, IO
Continuous Current
Surge Current
10mA
15mA
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.
Package Thermal Impedance, θJA
24 Lead TSSOP, EPad
32.1°C/W (0 mps)
-65°C to 150°C
Storage Temperature, TSTG
TABLE 4A. POWER SUPPLY DC CHARACTERISTICS, VDD = VDDO = 3.3V±5%, TA = 0°C TO 70°C
Symbol
Parameter
VDD
Core Supply Voltage
Test Conditions
Minimum
Typical
Maximum
Units
3.135
3.3
3.465
V
VDDA
Analog Supply Voltage
VDD – 0.08
3.3
VDD
V
VDDO
Output Supply Voltage
3.135
3.3
3.465
IDD
Power Supply Current
V
132
mA
IDDA
Analog Supply Current
8
mA
IDDO
Output Supply Current
120
mA
TABLE 4B. POWER SUPPLY DC CHARACTERISTICS, VDD = 3.3V±5%, VDDO = 2.5V±5%, TA = 0°C TO 70°C
Symbol
Parameter
Test Conditions
Minimum
Typical
Maximum
Units
VDD
Core Supply Voltage
VDDA
Analog Supply Voltage
3.135
3.3
3.465
V
VDD – 0.07
3.3
VDD
V
VDDO
Output Supply Voltage
2.375
IDD
Power Supply Current
2.5
2.625
V
125
mA
IDDA
Analog Supply Current
7
mA
IDDO
Output Supply Current
115
mA
TABLE 4C. LVCMOS / LVTTL DC CHARACTERISTICS, VDD = 3.3V±5%, VDDO = 3.3V±5%
Symbol
Parameter
VIH
Input High Voltage
VIL
Input Low Voltage
IIH
Input High Current
IIL
Input Low Current
Test Conditions
OR
Minimum
2
-0.3
FB_SEL
PLL_BYPASS,
N_SEL0, N_SEL1
FB_SEL
PLL_BYPASS,
N_SEL0, N_SEL1
2.5V±5%, TA = 0°C
Typical
TO
70°C
Maximum
Units
VDD + 0.3
V
0.8
V
VDD = VIN = 3.465V
150
µA
VDD = VIN = 3.465V
5
µA
VDD = 3.465V, VIN = 0V
-5
µA
VDD = 3.465V, VIN = 0V
-150
µA
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
TABLE 4D. LVDS DC CHARACTERISTICS, VDD = VDDO = 3.3V±5% TA = 0°C TO 70°C
Symbol
Parameter
VOD
Differential Output Voltage
Δ VOD
VOD Magnitude Change
VOS
Offset Voltage
Δ VOS
VOS Magnitude Change
Test Conditions
Minimum
Typical
Maximum
Units
350
mV
40
mV
1.25
V
50
mV
NOTE: Please refer to Parameter Measurement Information for output information.
TABLE 4E. LVDS DC CHARACTERISTICS, VDD = 3.3V±5%, VDDO = 2.5V±5%, TA = 0°C TO 70°C
Symbol
Parameter
Test Conditions
Minimum
Typical
Maximum
Units
VOD
Differential Output Voltage
350
mV
Δ V OD
VOD Magnitude Change
40
mV
VOS
Offset Voltage
Δ V OS
VOS Magnitude Change
1.25
V
50
mV
TABLE 5. CRYSTAL CHARACTERISTICS
Parameter
Test Conditions
Minimum
Mode of Oscillation
Typical Maximum
Units
Fundamental
25.5
MHz
Equivalent Series Resistance (ESR)
Frequency
15.625
50
Ω
Shunt Capacitance
7
pF
Drive Level
1
mW
NOTE: Characterized using an 18pF parallel resonant cr ystal.
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
TABLE 6A. AC CHARACTERISTICS, VDD = VDDO = 3.3V±5%, TA = 0°C TO 70°C
Symbol Parameter
FOUT
Output Frequency
t jit(Ø)
RMS Phase Jitter (Random)
t sk(o)
Output Skew; NOTE 1, 2
tR / tF
Output Rise/Fall Time
odc
Output Duty Cycle
Test Conditions
Minimum
Typical
53.125
125MHz, Integration Range:
1.875MHz - 20MHz
20% to 80%
Maximum
Units
333.33
MHz
0.48
ps
TBD
ps
37 5
ps
50
PLL Lock Time
tLOCK
See Parameter Measurement Information section.
NOTE 1: Defined as skew between outputs at the same supply voltage and with equal load conditions.
Measured at the output differential crossing points.
NOTE 2: This parameter is defined in accordance with JEDEC Standard 65.
%
1
ms
Maximum
Units
333.33
MHz
TABLE 6B. AC CHARACTERISTICS, VDD = 3.3V±5%, VDDO = 2.5V±5%, TA = 0°C TO 70°C
Symbol Parameter
FOUT
Test Conditions
Output Frequency
tjit(Ø)
RMS Phase Jitter (Random)
t sk(o)
Output Skew; NOTE 1, 2
tR / tF
Output Rise/Fall Time
odc
Output Duty Cycle
Minimum
Typical
53.125
125MHz, Integration Range:
1.875MHz - 20MHz
20% to 80%
0.44
ps
TBD
ps
400
ps
50
%
PLL Lock Time
tLOCK
See Parameter Measurement Information section.
NOTE 1: Defined as skew between outputs at the same supply voltage and with equal load conditions.
Measured at the output differential crossing points.
NOTE 2: This parameter is defined in accordance with JEDEC Standard 65.
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
6
1
ms
ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
TYPICAL PHASE NOISE AT 125MHZ @ 3.3V
0
➤
-10
-20
-30
Gb Ethernet Filter
-50
-60
-70
125MHz
RMS Phase Jitter (Random)
1.875MHz to 20MHz = 0.48ps (typical)
-80
Raw Phase Noise Data
-90
-100
-110
-120
-130
-140
-150
➤
NOISE POWER dBc
Hz
-40
➤
-160
-170
-180
-190
-200
Phase Noise Result by adding
Gb Ethernet Filter to raw data
10
100
1k
10k
100k
1M
10M
100M
OFFSET FREQUENCY (HZ)
TYPICAL PHASE NOISE AT 125MHZ @ 3.3V/2.5V
➤
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
Gb Ethernet Filter
125MHz
RMS Phase Jitter (Random)
1.875MHz to 20MHz = 0.44ps (typical)
Raw Phase Noise Data
-110
-120
➤
-130
-140
-150
-160
-170
-180
-190
-200
➤
NOISE POWER dBc
Hz
0
Phase Noise Result by adding
Gb Ethernet Filter to raw data
10
100
1k
10k
100k
1M
10M
100M
OFFSET FREQUENCY (HZ)
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
PARAMETER MEASUREMENT INFORMATION
VDD
SCOPE
3.3V±5%
POWER SUPPLY
+ Float GND –
Qx
VDD,
VDDO V
DDA
Qx
VDDA
SCOPE
+ +
VDDO
LVDS
LVDS
nQx
nQx
3.3V OUTPUT LOAD AC TEST CIRCUIT
3.3V/2.5V OUTPUT LOAD AC TEST CIRCUIT
nQx
nQ0:nQ5
Qx
Q0:Q5
t PW
t
nQy
Qy
odc =
tsk(o)
PERIOD
t PW
x 100%
t PERIOD
OUTPUT SKEW
OUTPUT DUTY CYCLE/PULSE WIDTH/PERIOD
VDD
out
80%
DC Input
VSW I N G
Clock
Outputs
LVDS
➤
80%
20%
20%
tR
➤
out
tF
VOS/Δ VOS
➤
OFFSET VOLTAGE SETUP
OUTPUT RISE/FALL TIME
VDD
➤
out
➤
LVDS
100
VOD/Δ VOD
out
➤
DC Input
DIFFERENTIAL OUTPUT VOLTAGE SETUP
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
Reference Document: JEDEC Publication 95, MO-153
–
POWER
SUPPLY
Float GND
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
APPLICATION INFORMATION
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins are
vulnerable to random noise. To achieve optimum jitter performance, power supply isolation is required. The ICS844256 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 VCC pin and also shows that
VDDA requires that an additional10Ω resistor along with a 10µF
bypass capacitor be connected to the VDDA pin.
3.3V
VDD
.01μF
10Ω
VDDA
.01μF
10μF
FIGURE 1. POWER SUPPLY FILTERING
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
OUTPUTS:
LVCMOS CONTROL PINS
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
LVDS Outputs
All unused LVDS output pairs can be either left floating or
terminated with 100Ω across. If they are left floating, we
recommend that there is no trace attached.
CRYSTAL INPUT INTERFACE
below were determined using an 18pF parallel resonant
crystal and were chosen to minimize the ppm error.
The ICS844256 has been characterized with 18pF parallel
resonant crystals. The capacitor values shown in Figure 2
XTAL_IN
C1
18p
X1
18pF Parallel Crystal
XTAL_OUT
C2
22p
FIGURE 2. CRYSTAL INPUt INTERFACE
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
LVCMOS TO XTAL INTERFACE
resistance (Rs) equals the transmission line impedance. In
addition, matched termination at the crystal input will attenuate
the signal in half. This can be done in one of two ways. First,
R1 and R2 in parallel should equal the transmission line
impedance. For most 50Ω applications, R1 and R2 can be 100Ω.
This can also be accomplished by removing R1 and making R2
50Ω.
The XTAL_IN input can accept a single-ended LVCMOS signal
through an AC couple capacitor. A general interface diagram is
shown in Figure 3. The XTAL_OUT pin can be left floating. The
input edge rate can be as slow as 10ns. For LVCMOS inputs, it
is recommended that the amplitude be reduced from full swing
to half swing in order to prevent signal interference with the
power rail and to reduce noise. This configuration requires that
the output impedance of the driver (Ro) plus the series
VDD
VCC
VDD
VCC
R1
Ro
.1uf
Rs
Zo = 50
XTAL_IN
R2
Zo = Ro + Rs
XTAL_OUT
FIGURE 3. GENERAL DIAGRAM FOR LVCMOS DRIVER TO XTAL INPUT INTERFACE
3.3V, 2.5V LVDS DRIVER TERMINATION
require a matched load termination of 100Ω across near
the receiver input.
A general LVDS interface is shown in Figure 4. In a 100Ω
differential transmission line environment, LVDS drivers
2.5V or 3.3V
VDD
LVDS_Driv er
+
R1
100
-
100 Ohm Differential Transmission Line
FIGURE 4. TYPICAL LVDS DRIVER TERMINATION
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256BG REV. B NOVEMBER 19, 2007
Reference Document: JEDEC Publication 95, MO-153
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
EPAD THERMAL RELEASE PATH
In order to maximize both the removal of heat from the package
and the electrical perfor mance, a land patter n must be
incorporated on the Printed Circuit Board (PCB) within the footprint
of the package corresponding to the exposed metal pad or
exposed heat slug on the package, as shown in Figure 5. The
solderable area on the PCB, as defined by the solder mask, should
be at least the same size/shape as the exposed pad/slug area on
the package to maximize the thermal/electrical performance.
Sufficient clearance should be designed on the PCB between the
outer edges of the land pattern and the inner edges of pad pattern
for the leads to avoid any shorts.
are application specific and dependent upon the package power
dissipation as well as electrical conductivity requirements. Thus,
thermal and electrical analysis and/or testing are recommended
to determine the minimum number needed. Maximum thermal
and electrical performance is achieved when an array of vias is
incorporated in the land pattern. It is recommended to use as
many vias connected to ground as possible. It is also
recommended that the via diameter should be 12 to 13mils (0.30
to 0.33mm) with 1oz copper via barrel plating. This is desirable to
avoid any solder wicking inside the via during the soldering process
which may result in voids in solder between the exposed pad/
slug and the thermal land. Precautions should be taken to
eliminate any solder voids between the exposed heat slug and
the land pattern. Note: These recommendations are to be used
as a guideline only. For further information, refer to the Application
Note on the Surface Mount Assembly of Amkor’s Thermally/
Electrically Enhance Leadfame Base Package, Amkor Technology.
While the land pattern on the PCB provides a means of heat
transfer and electrical grounding from the package to the board
through a solder joint, thermal vias are necessary to effectively
conduct from the surface of the PCB to the ground plane(s). The
land pattern must be connected to ground through these vias.
The vias act as “heat pipes”. The number of vias (i.e. “heat pipes”)
SOLDER
PIN
PIN PAD
EXPOSED HEAT SLUG
GROUND PLANE
THERMAL VIA
SOLDER
SOLDER
PIN
LAND PATTERN
(GROUND PAD)
PIN PAD
FIGURE 5. ASSEMBLY FOR EXPOSED PAD THERMAL RELEASE PATH –SIDE VIEW (DRAWING NOT TO SCALE)
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
POWER CONSIDERATIONS
This section provides information on power dissipation and junction temperature for the ICS844256.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS844256 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.
•
•
Power (core)MAX = VDD_MAX * (IDD_MAX + IDDA_MAX) = 3.465V * (132mA + 8mA) = 485.1mW
Power (outputs)MAX = VDDO_MAX * IDDO_MAX = 3.465V * 120mA = 415.8mW
Total Power_MAX = 485.1mW + 415.8mW = 900.9mW
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 HiPerClockSTM 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 32.1°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
70°C + 0.901W * 32.1°C/W = 98.9°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 (single layer or multi-layer).
TABLE 7. THERMAL RESISTANCE θJA
FOR
24-LEAD TSSOP, E-PAD, FORCED CONVECTION
θJA by Velocity (Meters per Second)
Multi-Layer PCB, JEDEC Standard Test Boards
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
12
0
1
2.5
32.1°C/W
25.5°C/W
24.0°C/W
ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
RELIABILITY INFORMATION
TABLE 8. θJAVS. AIR FLOW TABLE
FOR
24 LEAD TSSOP, E-PAD
θJA by Velocity (Meters per Second)
Multi-Layer PCB, JEDEC Standard Test Boards
0
1
2.5
32.1°C/W
25.5°C/W
24.0°C/W
TRANSISTOR COUNT
The transistor count for ICS844256 is: 3887
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
13
ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PACKAGE OUTLINE - G SUFFIX
FOR
24 LEAD TSSOP, E-PAD
PRELIMINARY
TABLE 9. PACKAGE DIMENSIONS
SYMBOL
Millimeters
Minimum
N
Nominal
Maximum
24
A
--
1.10
A1
0.05
0.15
A2
0.85
b
0.19
b1
0.19
c
0.09
c1
0.09
D
7. 7 0
E
E1
0.95
0.30
0.22
0.25
0.20
0.127
0.16
7.80
7.90
6.40 BASIC
4.30
e
L
0.90
4.40
4.50
0.65 BASIC
0.50
0.60
0.70
P
5.0
P1
3.2
α
0°
8°
aaa
0.076
bbb
0.10
Reference Document: JEDEC Publication 95, MO-153
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
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FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
TABLE 10. ORDERING INFORMATION
Part/Order Number
Marking
Package
Shipping Packaging
Temperature
ICS844256BG
ICS844256BG
24 Lead TSSOP, E-Pad
tube
0°C to 70°C
ICS844256BGT
ICS844256BG
24 Lead TSSOP, E-Pad
2500 tape & reel
0°C to 70°C
ICS844256BGLF
ICS844256BGLF
24 Lead "Lead-Free" TSSOP, E-Pad
tube
0°C to 70°C
ICS844256BGLFT
ICS844256BGLF
24 Lead "Lead-Free" TSSOP, E-Pad
2500 tape & reel
0°C to 70°C
NOTE: Par ts that are ordered with an "LF" suffix to the par t number are the Pb-Free configuration and are RoHS compliant.
While the information presented herein has been checked for both accuracy and reliability, Integrated Device Technology, Incorporated (IDT) assumes no responsibility for either its use or for
infringement of any patents or other rights of third parties, which would result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial
applications. Any other applications such as those requiring extended temperature ranges, high reliability or other extraordinary environmental requirements are not recommended without additional
processing by IDT. IDT reserves the right to change any circuitry or specifications without notice. IDT does not authorize or warrant any IDT product for use in life support devices or critical medical
instruments.
IDT ™ / ICS™ LVDS FREQUENCY SYNTHESIZER W/FANOUT BUFFER
15
ICS844256BG REV. B NOVEMBER 19, 2007
ICS844256
FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
PRELIMINARY
Innovate with IDT and accelerate your future networks. Contact:
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For Tech Support
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© 2007 Integrated Device Technology, Inc. All rights reserved. Product specifications subject to change without notice. IDT, the IDT logo, ICS and HiPerClockS are trademarks
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