This document contains information on a preproduction product. Specifications and information herein are subject to change without notice.
2.28.02
FS6245
FS6245
FS6245
FS6245
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
ISO9001
ISO9001
ISO9001
ISO9001
1.0 Features
On-chip tunable voltage-controlled crystal oscillator
circuitry (VCXO) allows precise system frequency
tuning (pull range typically 300ppm)
VCXO tuning range: 0-3V
Uses inexpensive fundamental-mode crystals
Two integrated phase-locked loops (PLL) multiply
VCXO frequency to the higher system frequencies
needed
5V core supply voltage (contact factory for 3.3V)
3.3V / 5V output supply voltage
Small circuit board footprint (20-pin SOIC)
Custom frequency selections available - contact your
local AMI Sales Representative for more information
Figure 1: Pin Configuration
1
16
2
3
4
5
6
7
8
15
14
13
12
11
n/c
XOUT
XIN
VDD
XTUNE
VSS
OE
n/c
n/c
CLKB
VSS
VDDO
n/c
FS624
5
9
10
CLKA
n/c
18
17
n/c
CLKC
20
19
n/c
n/c
n/c
2.0 Description
The FS6245 is a monolithic CMOS clock generator IC
designed to minimize cost and component count in digital
video/audio systems.
At the core of the FS6245 is circuitry that implements a
voltage-controlled crystal oscillator when an external
resonator is attached. The VCXO allows device frequen-
cies to be precisely adjusted for use in systems that have
frequency matching requirements, such as digital satellite
receivers.
Two high-resolution phase-locked loops generate the
output clock frequencies (CLKA, CLKB, and CLKC).
These frequencies are phase-locked and frequency-
locked to the VCXO frequency. Synthesis error of the
PLLs is +/-0 ppm unless otherwise noted.
Table 1: Crystal / Output Frequencies
DEVICE
f
XIN
(MHz) CLKA (MHz) CLKB (MHz) CLKC (MHz)
FS6245-01
13.500
11.0592
18.432
27.000
NOTE: Contact AMI for custom PLL frequencies
Figure 2: Block Diagram
VCXO
FS6245
PLL
XOUT
XIN
CLKA
XTUNE
Divider
Array
CLKB
PLL
CLKC
2
2.28.02
FS6245
FS6245
FS6245
FS6245
Dual PLL
Dual PLL
Dual PLL
Dual PLL VCXO Clock Generator IC
VCXO Clock Generator IC
VCXO Clock Generator IC
VCXO Clock Generator IC
ISO9001
ISO9001
ISO9001
ISO9001
Table 2: Pin Descriptions
Key: AI = Analog Input; AO = Analog Output; DI = Digital Input; DI
U
= Input with Internal Pull-Up; DI
D
= Input with Internal Pull-Down; DIO = Digital Input/Output; DI-3 = Three-Level Digital Input,
DO = Digital Output; P = Power/Ground; # = Active Low pin
PIN
TYPE
NAME
DESCRIPTION
1
-
N/C
No Connection
2
AI
XIN
VCXO Crystal Feedback
3
AO
XOUT / FREF
VCXO Crystal Drive / External Reference Clock Input
4
P
VDD
Core Power Supply
5
AI
XTUNE
VCXO Tune Input
6
-
N/C
No Connection
7
P
VSS
Ground
8
DI
U
OE
Output Enable
9
DO
CLKA
Clock Output "A"
10
-
N/C
No Connection
11
-
N/C
No Connection
12
-
N/C
No Connection
13
DO
CLKB
Clock Output "B"
14
P
VSS
Ground
15
P
VDDO
Output Power Supply (must be less than or equal to VDD)
16
-
N/C
No Connection
17
-
N/C
No Connection
18
DO
CLKC
Clock Output "C"
19
-
N/C
No Connection
20
-
N/C
No Connection
3
2.28.02
FS6245
FS6245
FS6245
FS6245
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
ISO9001
ISO9001
ISO9001
ISO9001
3.0 Functional Block Description
3.1
Phase-Locked Loop (PLL)
The on-chip PLL is a standard frequency- and phase-
locked loop architecture. The PLL multiplies the reference
oscillator to the desired frequency by a ratio of integers.
The frequency multiplication is exact with a zero synthe-
sis error (unless otherwise noted).
3.2 Voltage-Controlled
Crystal
Oscillator (VCXO)
The VCXO provides a tunable, low-jitter frequency refer-
ence for the rest of the FS6245 system components.
Loading capacitance for the crystal is internal to the
FS6245. No external components (other than the crystal
resonator itself) are required for operation of the VCXO.
Continuous fine-tuning of the VCXO frequency is accom-
plished by varying the voltage on the XTUNE pin.
The oscillator operates the crystal resonator in the paral-
lel-resonant mode. Crystal warping, or the "pulling" of the
crystal oscillation frequency, is accomplished by altering
the effective load capacitance presented to the crystal by
the oscillator circuit. The actual amount that changing the
load capacitance alters the oscillator frequency will be
dependent on the characteristics of the crystal as well as
the oscillator circuit itself.
Specifically, the motional capacitance of the crystal (usu-
ally referred to by crystal manufacturers as C
1
), the static
capacitance of the crystal (C
0
), and the load capacitance
(C
L
) of the oscillator determine the "warping" or "pulling"
capability of the crystal in the oscillator circuit.
A simple formula to obtain the warping capability of a
crystal oscillator is:
(
)
(
) (
)
C
C
C
C
C
C
C
ppm
f
L
L
L
L
1
0
2
0
6
1
2
1
2
10
)
(
+
+
-
=
where C
L1
and C
L2
are the two extremes of the applied
load capacitance.
EXAMPLE: A crystal with the following parameters is
used. With C
1
= 0.025pF, C
0
= 6pF, C
L1
= 10pF, and C
L2
= 20pF, the tuning range is
(
)
(
) (
)
ppm
.
f
300
10
6
20
6
2
106
10
20
025
0
=
+
+
-
=
.
FS6245 Typical VCXO Deviation vs. XTUNE Input
-200
-150
-100
-50
0
50
100
150
200
250
0
0.5
1
1.5
2
2.5
3
V(XTUNE) - volts
De
v
i
a
t
ion f
r
om
1
3
.
5
0
0
MH
z -
ppm
4
2.28.02
FS6245
FS6245
FS6245
FS6245
Dual PLL
Dual PLL
Dual PLL
Dual PLL VCXO Clock Generator IC
VCXO Clock Generator IC
VCXO Clock Generator IC
VCXO Clock Generator IC
ISO9001
ISO9001
ISO9001
ISO9001
4.0 Electrical
Specifications
Table 3: Absolute Maximum Ratings
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These conditions represent a stress rating only, and functional operation of the device at
these or any other conditions above the operational limits noted in this specification is not implied. Exposure to maximum rating conditions for extended conditions may affect device performance,
functionality, and reliability.
PARAMETER
SYMBOL
MIN.
MAX.
UNITS
Supply Voltage (V
SS
= ground)
V
DD
V
SS
-0.5
7
V
Input Voltage, dc
V
I
V
SS
-0.5
V
DD
+0.5
V
Output Voltage, dc
V
O
V
SS
-0.5
V
DD
+0.5
V
Input Clamp Current, dc (V
I
< 0 or V
I
> V
DD
)
I
IK
-50
50
mA
Output Clamp Current, dc (V
I
< 0 or V
I
> V
DD
)
I
OK
-50
50
mA
Storage Temperature Range (non-condensing)
T
S
-65
150
C
Ambient Temperature Range, Under Bias
T
A
-55
125
C
Junction Temperature
T
J
125
C
Lead Temperature (soldering, 10s)
260
C
Input Static Discharge Voltage Protection (MIL-STD 883E, Method 3015.7)
2
kV
CAUTION: ELECTROSTATIC SENSITIVE DEVICE
Permanent damage resulting in a loss of functionality or performance may occur if this device is subjected to a high-energy elec-
trostatic discharge.
Table 4: Operating Conditions
PARAMETER
SYMBOL
CONDITIONS/DESCRIPTION
MIN.
TYP.
MAX.
UNITS
Core Supply Voltage (VDD)
V
DD
5V 10%
4.75
5
5.25
V
CLK Pin Supply Voltage (VDDO)
V
DDO
3.0
-
V
DD
+0.3
V
Ambient Operating Temperature Range
T
A
0
70
C
Crystal Resonator Frequency
f
XTAL
Fundamental Mode
5
13.5
18
MHz
Crystal Resonator Motional Capacitance
C
1(xtal)
AT cut
25
fF
Crystal Load Capacitance
C
L(xtal)
AT cut
14
pF
5
2.28.02
FS6245
FS6245
FS6245
FS6245
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
Dual PLL VCXO Clock Generator IC
ISO9001
ISO9001
ISO9001
ISO9001
Table 5: DC Electrical Specifications
Unless otherwise stated, V
DD
= 5V 10%, no load on any output, and ambient temperature range T
A
= 0C to 70C. Parameters denoted with an asterisk ( * ) represent nominal characterization data
and are not production tested to any specific limits. Where given, MIN and MAX characterization data are
3
from typical. Negative currents indicate current flows out of the device.
PARAMETER
SYMBOL
CONDITIONS/DESCRIPTION
MIN.
TYP.
MAX.
UNITS
Overall
Supply Current, Dynamic, with Loaded
Outputs
I
DD
f
XTAL
= 13.5MHz; C
L
= 10pF
20
mA
Voltage Controlled Crystal Oscillator - VDD=5.0V
Crystal Loading Capacitance
C
L(xtal)
As seen by a crystal connected to XIN and
XOUT (@ V
XTUNE
= 1.65V)
14
pF
Crystal Resonator Motional Capacitance
C
1(xtal)
AT cut
25
fF
VCXO Tuning Range
f
XTAL
= 13.5MHz; C
L(xtal)
= 14pF; C
1(xtal)
= 25fF
300
ppm
VCXO Tuning Characteristic
Note: positive
F for positive
V
100
ppm/V
Crystal Drive Level
R
XTAL
=20
; C
L(xtal)
= 14pF
200
uW
Clock Outputs (CLKx) - VDDO=3.3V
High-Level Output Source Current *
I
OH
V
O
= 2.0V
-40
mA
Low-Level Output Sink Current *
I
OL
V
O
= 0.4V
17
mA
z
OH
V
O
= 0.5V
DD
; output driving high
30
Output Impedance *
z
OL
V
O
= 0.5V
DD
; output driving low
30
Short Circuit Source Current *
I
OSH
V
O
= 0V; shorted for 30s, max.
-55
mA
Short Circuit Sink Current *
I
OSL
V
O
= 3.3V; shorted for 30s, max.
55
mA
Clock Outputs (CLKx) - VDDO=5.0V
High-Level Output Source Current *
I
OH
V
O
= 4.5V
-30
mA
Low-Level Output Sink Current *
I
OL
V
O
= 0.4V
26
mA
z
OH
V
O
= 0.5V
DD
; output driving high
25
Output Impedance *
z
OL
V
O
= 0.5V
DD
; output driving low
25
Short Circuit Source Current *
I
OSH
V
O
= 0V; shorted for 30s, max.
-100
mA
Short Circuit Sink Current *
I
OSL
V
O
= 5V; shorted for 30s, max.
100
mA
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