SM8761 series
Spread Spectrum Clock Generator
OVERVIEW
The SM8761 series are compact clock generator ICs that have a spread spectrum (SS) function to reduce unde-
sirable EMI radiation. They have a built-in crystal oscillator circuit, PLL, and loop filter. They accept an input
clock signal, generated using an external crystal or direct external clock input, and output an SS-modulated
clock signal. In addition, versions are available for center spread and down spread modulation mode, and all
have a mode control pin to select the SS modulation function.
FEATURES
I
I
I
Spread spectrum clock output to reduce EMI
Correspond to wide range of output frequency
Low jitter
SM8761AA
I
I
I
Operating supply voltage: 3.3
±
0.3V
Multiplication: 1-time multiplication
Package: 8-pin SOP
SM8761AB
Center spread
±
0.75% to
±
2.25%
12MHz to 32MHz
12MHz to 32MHz
12MHz to 32MHz
1-time multiplication
200ps (typ) @16MHz
Spectrum modulation mode
Spectrum modulation rate
*1
Crystal element connection
Input frequency
External input clock
Output frequency
Multiplication
Jitter (Cycle-to-Cycle)
Down spread
– 1.0% to – 3.8%
20MHz to 40MHz
20MHz to 108MHz
20MHz to 108MHz
1-time multiplication
200ps (typ) @33MHz
120ps (typ) @75MHz
*1. The modulation rate that can be selected varies with the input frequency.
PINOUT
(Top view)
PACKAGE DIMENSIONS
(Unit: mm)
+
0.15
−
0.1
0.05
XT
VDD
VSS
CLKOUT
1
2
3
4
8
7
6
5
XTN
MSEL1
MSEL0
0.695typ
6.2
±
0.3
4.4
±
0.2
TSTN
5.2
±
0.3
0.05
±
0.05
1.5
±
0.1
1.27
0.4
±
0.2
APPLICATIONS
I
I
I
I
I
0.10
0.4
±
0.1
0 to 10°
0.12
M
Printer (laser/inkjet)
Photocopiers, scanners
LCD/PDP displays
Projectors
Miscellaneous electronic equipment
ORDERING INFORMATION
Device
SM8761AAS
SM8761ABS
Package
8-pin SOP
NIPPON PRECISION CIRCUITS INC.—1
SM8761 series
BLOCK DIAGRAM
VDD
VSS
XT
XTN
X'tal
OSC
R Counter
Phase Detector
&
Charge Pump
LPF
N Counter
(PLL)
VCO
Post
Divider
CLKOUT
SS Control
Mode, R/N Counter setting,
Divider setting, etc.
SS Control
Control Logic
MSEL0
MSEL1
TSTN
PIN DESCRIPTION
Number
1
2
3
4
5
6
7
8
Name
XT
VDD
VSS
CLKOUT
TSTN
MSEL0
MSEL1
XTN
I/O
*1
I
PWR
GND
O
Ip
I
I
O
Function
Crystal oscillator element connection or external clock input
Supply voltage
Ground
SS clock output
Test (Tie HIGH or leave open circuit)
SS modulation rate setting
SS modulation rate setting
Crystal oscillator element connection
*1. Built-in pull-up resistor
NIPPON PRECISION CIRCUITS INC.—2
SM8761 series
SPECIFICATIONS
Absolute Maximum Ratings
Parameter
Supply voltage range
Input voltage range
Output voltage range
Power dissipation
Storage temperature range
Symbol
V
DD
V
IN
V
OUT
P
D
T
STG
Rating
−0.3
to +6.5
−0.3
to V
DD
+ 0.3
−0.3
to V
DD
+ 0.3
300
−55
to +125
Unit
V
V
V
mW
°C
Recommended Operating Conditions
SM8761AA
V
SS
= 0V unless otherwise noted.
Rating
Parameter
Supply voltage range
Output load capacitance
Symbol
V
DD
C
L
f
IN
T
OPR
CLKOUT output pin
Crystal oscillator element
connection
External clock input
Operating temperature range
Condition
min
+3.0
–
20
20
–20
typ
–
–
–
–
–
max
+3.6
15
40
MHz
108
+80
°C
V
pF
Unit
Master clock frequency
SM8761AB
V
SS
= 0V unless otherwise noted.
Rating
Parameter
Supply voltage range
Output load capacitance
Symbol
V
DD
C
L
f
IN
T
OPR
CLKOUT output pin
Crystal oscillator element
connection
External clock input
Operating temperature range
Condition
min
+3.0
–
12
12
–20
typ
–
–
–
–
–
max
+3.6
15
32
MHz
32
+80
°C
V
pF
Unit
Master clock frequency
NIPPON PRECISION CIRCUITS INC.—3
SM8761 series
ELECTRICAL CHARACTERISTICS
DC Characteristics
SM8761AA
V
DD
= 3.3
±
0.3V, V
SS
= 0V, Ta =
−20
to +80°C unless otherwise noted.
Rating
Parameter
Symbol
Pins
Condition
min
V
DD
= 3.3V, Ta = 25°C,
external input clock, fin = 33MHz,
all outputs unloaded
I
DD
VDD
V
DD
= 3.3V, Ta = 25°C,
external input clock, fin = 75MHz,
all outputs unloaded
–
0.85V
DD
MSEL0, MSEL1
V
DD
= 3.3V
0.45V
DD
–
TSTN
V
DD
= 3.3V
0.85V
DD
–
0.80V
DD
–
–
–1
–
–100
–
–40
V
DD
– 0.4
–
16
–
0.50V
DD
–
–
–
–
–
–
–
–
–
–
–
–
–
24
–
0.55V
DD
0.15V
DD
–
0.15V
DD
–
0.20V
DD
1
–
1
–
40
–
–
V
0.4
µA
V
–
typ
11
max
16
mA
Unit
Current
consumption
V
IH1
V
IM1
V
IL1
Input voltage
V
IH2
V
IL2
V
IH3
V
IL3
I
IH1
I
IL1
Input current
I
IH2
I
IL2
I
IH3
I
IL3
Output voltage
V
OH
V
OL
CLKOUT
XT
TSTN
MSEL0, MSEL1
XT
V
DD
= 3.3V
V
IN
= V
DD
V
IN
= 0V
V
IN
= V
DD
, built-in pull-up resistor
V
IN
= 0V, built-in pull-up resistor
V
IN
= V
DD
V
IN
= 0V
I
OH
=
−2mA
I
OL
= 2mA
NIPPON PRECISION CIRCUITS INC.—4
SM8761 series
SM8761AB
V
DD
= 3.3
±
0.3V, V
SS
= 0V, Ta =
−20
to +80°C unless otherwise noted.
Rating
Parameter
Symbol
Pins
Condition
min
V
DD
= 3.3V, Ta = 25°C,
external input clock, fin = 12MHz,
all outputs unloaded
I
DD
VDD
V
DD
= 3.3V, Ta = 25°C,
external input clock, fin = 24MHz,
all outputs unloaded
–
0.85V
DD
MSEL0, MSEL1
V
DD
= 3.3V
0.45V
DD
–
TSTN
V
DD
= 3.3V
0.85V
DD
–
0.80V
DD
–
–
–1
–
–100
–
–40
V
DD
– 0.4
–
6
–
0.50V
DD
–
–
–
–
–
–
–
–
–
–
–
–
–
10
–
0.55V
DD
0.15V
DD
–
0.15V
DD
–
0.20V
DD
1
–
1
–
40
–
–
V
0.4
µA
V
–
typ
5
max
8
mA
Unit
Current
consumption
V
IH1
V
IM1
V
IL1
Input voltage
V
IH2
V
IL2
V
IH3
V
IL3
I
IH1
I
IL1
Input current
I
IH2
I
IL2
I
IH3
I
IL3
Output voltage
V
OH
V
OL
CLKOUT
XT
TSTN
MSEL0, MSEL1
XT
V
DD
= 3.3V
V
IN
= V
DD
V
IN
= 0V
V
IN
= V
DD
, built-in pull-up resistor
V
IN
= 0V, built-in pull-up resistor
V
IN
= V
DD
V
IN
= 0V
I
OH
=
−2mA
I
OL
= 2mA
NIPPON PRECISION CIRCUITS INC.—5
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