FemtoClock® NG Clock Synthesizer
843N571I
Datasheet
Description
The 843N571I is a PLL based clock synthesizer for use in Ethernet
applications. The device uses IDT’s fourth generation FemtoClock
®
NG technology for optimal high clock frequency and low phase noise
performance, combined with a low power consumption and high
power supply noise rejection. Using IDT’s latest FemtoClock NG PLL
technology, the 843N571I achieves <0.3ps RMS phase jitter
performance.
843N571I can synthesize 100MHz, 125MHz, 156.25MHz and a low
frequency 33.33MHz CPU clock from a single device. Six LVCMOS
outputs also serve as additional buffering of the 25MHz crystal
reference.
Features
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Fourth generation FemtoClock
®
Next Generation (NG) technology
Seven single-ended LVCMOS outputs, 30 output impedance
Three LVPECL output pairs
One differential LVPECL (QA, nQA) output pair: 156.25MHz
Two selectable differential LVPECL output pairs (QB, nQB and
QC, nQC): 100MHz and 125MHz
One single-ended LVCMOS (QD0) 33.33MHz CPU clock
Selectable external crystal or single-ended input source
Crystal oscillator interface designed for 25MHz, parallel resonant
crystal
FemtoClock NG frequency multiplier provides low jitter, high
frequency output
FemtoClock NG VCO frequency: 2.5GHz
RMS phase jitter @ 125MHz, using a 25MHz crystal
(12kHz – 20MHz): 0.283ps (typical)
Power supply noise rejection PSNR: -80dB
3.3V supply voltage
-40C to 85C ambient operating temperature
Lead-free (RoHS 6) packaging
Pin Assignment
FORCE_LOW
nc
QREF5
40 39 38 37 36 35 34 33 32 31
V
EE
V
CC
QREF0
QREF1
V
CC
XTAL_IN
XTAL_OUT
REFCLK
REFSEL
V
EE
1
2
3
4
5
6
7
8
9
10
11 12 13 14 15 16 17 18 19 20
V
CC
nQA
QB
nQB
V
CC
V
CC
QA
nc
nc
nc
30
29
QREF3
QREF2
V
CC
FREQSEL
V
CC
V
CC
V
CC
QD0
nQC
QC
QREF4
28
27
26
25
24
23
22
21
V
CC
V
CC
V
CC
ICS843N571I
40-Lead VFQFN
6mm x 6mm x 0.925mm
package body
K Package
Top View
©2018 Integrated Device Technology, Inc
V
EE
V
CC
nc
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November 29, 2018
843N571I Datasheet
Block Diagram
REFSEL
Pullup
QREF 0
XTAL_IN
25MHz
XTAL_OUT
OSC
QREF 1
1
0
QREF 2
QREF 3
QREF 4
QREF 5
REFCLK
25MHz
Pulldown
PF
+
CP
FemtoClock NG
VCO
÷16
QA
nQA
÷100
÷25
1
0
QB
nQB
FREQSEL
Pullup/Pulldown
3 - State
Decoder
1
QC
nQC
÷20
0
÷75
FORCE_LOW
Pulldown
QD0
©2018 Integrated Device Technology, Inc
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843N571I Datasheet
Pin Description and Pin Characteristic Tables
Table 1. Pin Descriptions
Number
1, 10, 34
Name
V
EE
Power
Type
Description
Negative supply pins.
Power supply pins.
Pins 2, 28, 33 – power supply connection for the 25MHz LVCMOS outputs
Pin 5 – power supply connection for the crystal oscillator
Pins 11, 15, 26, 35 – power supply connection for the dividers and other
core circuitry
Pin 16 (vposO) – power supply connection for the differential LVPECL
outputs
Pin 24, 25 – power supply connection for the 33MHz LVCMOS output
Pin 39 – power supply connection for the digital logic
Pin 40 – power supply connection for the PLL
Single-ended outputs. 3.3V LVCMOS/LVTTL reference levels.
Parallel resonant crystal interface. XTAL_OUT is the output,
XTAL_IN is the input.
Pulldown
Pullup
Single-ended LVCMOS/LVTTL reference clock input.
Reference select pin. When HIGH, selects crystal. When LOW, selects
REFCLK. See Table 3A. LVCMOS/LVTTL interface levels.
No connect.
Output
Output
Output
Output
Input
Input
Pullup/
Pulldown
Pulldown
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Differential output pair. LVPECL interface levels.
Single-ended output. 3.3V LVCMOS/LVTTL reference levels.
Frequency select pin. See Table 3B. LVCMOS/LVTTL interface levels.
Forces the QD0 output into a low state. See Table 3C.
LVCMOS/LVTTL interface levels.
2, 5, 11, 15,
16, 24, 25,
26, 28, 33,
35, 39, 40
V
CC
Power
3, 4,
29, 30,
31, 32
6,
7
8
9
12, 13, 14,
36, 38
17, 18
19, 20
21, 22
23
27
37
QREF0, QREF1,
QREF2, QREF3,
QREF4, QREF5
XTAL_IN,
XTAL_OUT
REFCLK
REFSEL
nc
QA, nQA
QB, nQB
QC, nQC
QD0
FREQSEL
FORCE_LOW
Output
Input
Input
Input
NOTE:
Pullup and Pulldown
refer to internal input resistors. See Table 2,
Pin Characteristics,
for typical values.
Table 2. Pin Characteristics
Symbol
C
IN
C
PD
R
PULLUP
R
PULLDOWN
R
OUT
Parameter
Input Capacitance
Power Dissipation
Capacitance
(per output)
QD0,
QREF[0:5]
Test Conditions
Crystal Not Included
V
CC
= 3.6V
Minimum
Typical
2
6
51
51
30
Maximum
Units
pF
pF
k
k
Input Pullup Resistor
Input Pulldown Resistor
Output
Impedance
QD0,
QREF[0:5]
©2018 Integrated Device Technology, Inc
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843N571I Datasheet
Function Tables
Table 3A. REFSEL Function Table
Inputs
REFSEL
0
1 (default)
REFCLK
XTAL_IN, XTAL_OUT
Input Source
Table 3C. FORCE_LOW Function Table
Inputs
FORCE_LOW
0 (default)
1
Output Frequency (MHz)
QD0
33.33
Disabled
Table 3B. FREQSEL Function Table
Inputs
FREQSEL
0
1
Float (default)
Output Frequency (MHz)
QB, nQB
125
100
125
QC, nQC
125
100
100
©2018 Integrated Device Technology, Inc
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843N571I Datasheet
Absolute Maximum Ratings
Exposure to absolute maximum rating conditions for extended periods may affect product reliability. 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.
Item
Supply Voltage, V
CC
Inputs, V
I
XTAL_IN
Other Inputs
Outputs, I
O
(LVCMOS)
Outputs, I
O
(LVPECL)
Continuous Current
Surge Current
Package Thermal Impedance,
JA
Maximum Junction Temperature, T
J,MAX
Storage Temperature, T
STG
Rating
3.63V
0V to 2V
-0.5V to V
CC
+ 0.5V
-0.5V to V
CC
+ 0.5V
50mA
100mA
37.7C/W (0 mps)
150°C
-65C to 150C
Recommended Operating Conditions
Symbol
T
A
T
J
Parameter
Ambient air temperature
Junction temperature
Minimum
-40
Typical
Maximum
85
125
Units
C
C
NOTE 1: It is the user’s responsibility to ensure that device junction temperature remains below the maximum allowed.
NOTE 2: All conditions in the table must be met to guarantee device functionality.
NOTE 3: The device is verified to the maximum operating junction temperature through simulation.
DC Electrical Characteristics
Table 4A. Power Supply DC Characteristics,
V
CC
= 3.3V ± 0.3V, V
EE
= 0V, T
A
= -40°C to 85°C
Symbol
V
CC
I
EE
Parameter
Power Supply Voltage
Power Supply Current
No Load
Test Conditions
Minimum
3.0
Typical
3.3
Maximum
3.6
250
Units
V
mA
Table 4B. LVCMOS/LVTTL DC Characteristics,
V
CC
= 3.3V ± 0.3V, T
A
= -40°C to 85°C
Symbol
V
IH
Parameter
Input High
Voltage
REFSEL,
FORCE_LOW
FREQSEL
REFSEL,
FORCE_LOW
FREQSEL
FREQSEL
V
CC
/2 - 0.1
Test Conditions
Minimum
2
V
CC
- 0.4
-0.3
0.8
0.4
V
CC
/2 + 0.1
Typical
Maximum
V
CC
+ 0.3
Units
V
V
V
V
V
V
IL
Input Low
Voltage
Input
Medium
Voltage
V
IM
©2018 Integrated Device Technology, Inc
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November 29, 2018
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