SM8761 series
Spread Spectrum Clock Generator
OVERVIEW
The SM8761 series are compact clock generator ICs that have a spread spectrum (SS) function to reduce undesirable 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
■
■
■
Spread spectrum clock output to reduce EMI
Correspond to wide range of output frequency
Low jitter
■
■
■
Operating supply voltage: 3.3 ± 0.3V
Multiplication: 1-time multiplication
Package: 8-pin SOP
SM8761AA
SM8761AB
Spectrum modulation mode
Down spread
Center spread
Spectrum modulation rate*1
– 1.0% to – 3.8%
± 0.75% to ± 2.25%
Crystal element connection
20MHz to 40MHz
12MHz to 32MHz
External input clock
20MHz to 108MHz
12MHz to 32MHz
Input frequency
Output frequency
20MHz to 108MHz
12MHz to 32MHz
Multiplication
1-time multiplication
1-time multiplication
200ps (typ) @33MHz
Jitter (Cycle-to-Cycle)
200ps (typ) @16MHz
120ps (typ) @75MHz
*1. The modulation rate that can be selected varies with the input frequency.
PINOUT
PACKAGE DIMENSIONS
(Top view)
(Unit: mm)
0.15 −+ 0.1
8
XTN
VDD
2
7
MSEL1
VSS
3
6
MSEL0
CLKOUT
4
5
TSTN
0.4 ± 0.2
1
4.4 ± 0.2
XT
6.2 ± 0.3
0.05
0.695typ
1.5 ± 0.1
0.05 ± 0.05
5.2 ± 0.3
1.27
0.10
0.4 ± 0.1
APPLICATIONS
■
■
■
■
■
Printer (laser/inkjet)
Photocopiers, scanners
LCD/PDP displays
Projectors
Miscellaneous electronic equipment
0 to 10°
0.12 M
ORDERING INFORMATION
Device
Package
SM8761AAS
SM8761ABS
8-pin SOP
NIPPON PRECISION CIRCUITS INC.—1
SM8761 series
BLOCK DIAGRAM
VDD
XT
X'tal
OSC
R Counter
VSS
Phase Detector
&
Charge Pump
LPF
N Counter
VCO
XTN
Post
Divider
CLKOUT
(PLL)
SS Control
Mode, R/N Counter setting,
Divider setting, etc.
SS Control
Control Logic
MSEL0
MSEL1
TSTN
PIN DESCRIPTION
Number
Name
I/O*1
1
XT
I
2
VDD
PWR
Supply voltage
3
VSS
GND
Ground
4
CLKOUT
O
SS clock output
5
TSTN
Ip
Test (Tie HIGH or leave open circuit)
6
MSEL0
I
SS modulation rate setting
7
MSEL1
I
SS modulation rate setting
8
XTN
O
Crystal oscillator element connection
Function
Crystal oscillator element connection or external clock input
*1. Built-in pull-up resistor
NIPPON PRECISION CIRCUITS INC.—2
SM8761 series
SPECIFICATIONS
Absolute Maximum Ratings
Parameter
Symbol
Rating
Unit
Supply voltage range
VDD
−0.3 to +6.5
V
Input voltage range
VIN
−0.3 to VDD + 0.3
V
VOUT
−0.3 to VDD + 0.3
V
PD
300
mW
TSTG
−55 to +125
°C
Output voltage range
Power dissipation
Storage temperature range
Recommended Operating Conditions
SM8761AA
VSS = 0V unless otherwise noted.
Rating
Parameter
Symbol
Supply voltage range
VDD
Output load capacitance
CL
Master clock frequency
fIN
Operating temperature range
Condition
Unit
min
typ
max
+3.0
–
+3.6
V
CLKOUT output pin
–
–
15
pF
Crystal oscillator element
connection
20
–
40
External clock input
20
–
108
–20
–
+80
TOPR
MHz
°C
SM8761AB
VSS = 0V unless otherwise noted.
Rating
Parameter
Symbol
Supply voltage range
VDD
Output load capacitance
CL
Master clock frequency
fIN
Operating temperature range
TOPR
Condition
Unit
min
typ
max
+3.0
–
+3.6
V
CLKOUT output pin
–
–
15
pF
Crystal oscillator element
connection
12
–
32
External clock input
12
–
32
–20
–
+80
MHz
°C
NIPPON PRECISION CIRCUITS INC.—3
SM8761 series
ELECTRICAL CHARACTERISTICS
DC Characteristics
SM8761AA
VDD = 3.3 ± 0.3V, VSS = 0V, Ta = −20 to +80°C unless otherwise noted.
Rating
Parameter
Current
consumption
Symbol
Pins
Condition
VDD = 3.3V, Ta = 25°C,
external input clock, fin = 33MHz,
all outputs unloaded
IDD
VIH2
MSEL0, MSEL1
TSTN
VIL2
VIH3
XT
VIL3
IIH1
MSEL0, MSEL1
IIL1
Input current
IIH2
TSTN
IIL2
IIH3
XT
IIL3
Output voltage
VOH
VOL
max
–
11
16
mA
VDD = 3.3V, Ta = 25°C,
external input clock, fin = 75MHz,
all outputs unloaded
–
16
24
0.85VDD
–
–
0.45VDD
0.50VDD
0.55VDD
–
–
0.15VDD
0.85VDD
–
–
–
–
0.15VDD
0.80VDD
–
–
–
–
0.20VDD
VIN = VDD
–
–
1
VIN = 0V
–1
–
–
VIN = VDD, built-in pull-up resistor
–
–
1
VIN = 0V, built-in pull-up resistor
–100
–
–
VIN = VDD
–
–
40
VIN = 0V
–40
–
–
VDD – 0.4
–
–
–
–
0.4
VDD = 3.3V
VIL1
Input voltage
typ
VDD
VIH1
VIM1
Unit
min
CLKOUT
VDD = 3.3V
VDD = 3.3V
IOH = −2mA
IOL = 2mA
V
µA
V
NIPPON PRECISION CIRCUITS INC.—4
SM8761 series
SM8761AB
VDD = 3.3 ± 0.3V, VSS = 0V, Ta = −20 to +80°C unless otherwise noted.
Rating
Parameter
Current
consumption
Symbol
Pins
Condition
VDD = 3.3V, Ta = 25°C,
external input clock, fin = 12MHz,
all outputs unloaded
IDD
VIH2
MSEL0, MSEL1
TSTN
VIL2
VIH3
XT
VIL3
IIH1
MSEL0, MSEL1
IIL1
Input current
IIH2
TSTN
IIL2
IIH3
XT
IIL3
Output voltage
VOH
VOL
max
–
5
8
mA
VDD = 3.3V, Ta = 25°C,
external input clock, fin = 24MHz,
all outputs unloaded
–
6
10
0.85VDD
–
–
0.45VDD
0.50VDD
0.55VDD
–
–
0.15VDD
0.85VDD
–
–
–
–
0.15VDD
0.80VDD
–
–
–
–
0.20VDD
VIN = VDD
–
–
1
VIN = 0V
–1
–
–
VIN = VDD, built-in pull-up resistor
–
–
1
VIN = 0V, built-in pull-up resistor
–100
–
–
VIN = VDD
–
–
40
VIN = 0V
–40
–
–
VDD – 0.4
–
–
–
–
0.4
VDD = 3.3V
VIL1
Input voltage
typ
VDD
VIH1
VIM1
Unit
min
CLKOUT
VDD = 3.3V
VDD = 3.3V
IOH = −2mA
IOL = 2mA
V
µA
V
NIPPON PRECISION CIRCUITS INC.—5
SM8761 series
AC Characteristics
SM8761AA
VDD = 3.3 ± 0.3V, VSS = 0V, Ta = −20 to +80°C unless otherwise noted.
Parameter
Symbol
Pins
Clock frequency
fin
XT
Output clock rise time*2
tr
Output clock fall time*2
Rating
Condition
Unit
min
typ
max
Crystal connection
20
–
40
External clock input*1
20
–
108
CLKOUT
CL = 15pF, VOL = 0.2VDD to VOH =
0.8VDD transition time
–
2.0
–
ns
tf
CLKOUT
CL = 15pF, VOH = 0.8VDD to VOL =
0.2VDD transition time
–
2.0
–
ns
–
200
–
CLKOUT
Cycle-to-cycle jitter,
Ta = 25°C, CL = 15pF,
VO = 0.5VDD
fin = 33MHz
tjitter
fin = 75MHz
–
120
–
Output clock duty cycle*2
Dt
CLKOUT
45
50
55
%
Power-up time*2,*3
tp
CLKOUT
–
1
5
ms
Output clock jitter*2
Ta = 25°C, CL = 15pF, VO = 0.5VDD
MHz
ps
*1. When using an external clock input, it is recommended that the clock on XT have 50% duty and VDD level signal amplitude. Note that the input signal
voltage must not exceed the absolute maximum rating, otherwise it may cause the device to breakdown.
*2. Measured using the circuit in Figure 1 on the NPC standard evaluation board.
*3. The power-up time is the time from when the supply reaches 3.0V after the supply is turned ON until each output clock reaches its designated frequency to within ± 0.1%.
SM8761AB
VDD = 3.3 ± 0.3V, VSS = 0V, Ta = −20 to +80°C unless otherwise noted.
Parameter
Symbol
Pins
Clock frequency
fin
XT
Output clock rise time*2
tr
Output clock fall time*2
tf
Output clock jitter*2
tjitter
Rating
Condition
Unit
min
typ
max
Crystal connection
12
–
32
External clock input*1
12
–
32
CLKOUT
CL = 15pF, VOL = 0.2VDD to VOH =
0.8VDD transition time
–
2.0
–
ns
CLKOUT
CL = 15pF, VOH = 0.8VDD to VOL =
0.2VDD transition time
–
2.0
–
ns
fin = 12MHz
–
450
–
CLKOUT
Cycle-to-cycle jitter,
Ta = 25°C, CL = 15pF,
VO = 0.5VDD
fin = 16MHz
–
200
–
fin = 20MHz
–
300
–
fin = 27MHz
–
180
–
45
50
55
%
–
1
5
ms
Output clock duty cycle*2
Dt
CLKOUT
Power-up time*2,*3
tp
CLKOUT
Ta = 25°C, CL = 15pF, VO = 0.5VDD
MHz
ps
*1. When using an external clock input, it is recommended that the clock on XT have 50% duty and VDD level signal amplitude. Note that the input signal
voltage must not exceed the absolute maximum rating, otherwise it may cause the device to breakdown.
*2. Measured using the circuit in Figure 1 on the NPC standard evaluation board.
*3. The power-up time is the time from when the supply reaches 3.0V after the supply is turned ON until each output clock reaches its designated frequency to within ± 0.1%.
X'tal
+
+
DUT
Active Probe
(HP1152A)
Oscilloscope
(Infinium
HP54845A)
Passive Probe
(HP10435A)
Frequency &
Time Interval
Analyzer
(HP5371A)
DUT: Device Under Testing
Jitter
Measurement
System
(ASA, M1)
Figure 1. Measurement circuit
NIPPON PRECISION CIRCUITS INC.—6
SM8761 series
FUNCTIONAL DESCRIPTION
Master Clock
The SM8761 series master clock can be generated by the crystal oscillator formed by connecting a crystal
between XT (pin 1) and XTN (pin 8) as shown in Figure 2. Alternatively, an external master clock can be input
directly on XT (pin 1) as shown in Figure 3. If an external clock is input on XT, it is recommended that the
clock have 50% duty and VDD level voltage amplitude. Note that the input clock amplitude voltage must not
exceed the absolute maximum rating, otherwise it may cause the SM8761 series to breakdown.
C1
XT (Pin1)
Internal
Circuits
Oscillator
XTN (Pin8)
C2
C1, C2 = 5 to 33pF
Figure 2. Crystal element connection
External Clock
XT (Pin1)
Oscillator
Internal
Circuits
Open
XTN (Pin8)
Figure 3. External clock input
NIPPON PRECISION CIRCUITS INC.—7
SM8761 series
Function Controls
The SM8761 series power-down and SS modulation ON/OFF functions are controlled using the MSEL0 and
MSEL1 input pins as shown in Table 1.
SM8761AA
MSEL1 (Pin 7)
MSEL0 (Pin 6)
L
L
L
M
Input/Output
frequency range [MHz]
SS mode
SS modulation*1 [%]
–2.3
–3.2
20 to 54
(Low range)
H
M
L
–1.9
M
M
–3.8
M
H
–2.5
H
L
H
M
H
H
50 to 108
(High range)
Down spread
−2.8
L
–1.9
Down spread
–1.0
–1.2
*1. The modulation rates in the table above are reference values at 30MHz to 40MHz (Low range) and 70MHz to 80MHz (High
range). The modulation rate varies with the input/output frequency.
Note. Signal level “H” represents VDD level, “L” represents VSS level, and “M” represents 1/2VDD.
SM8761AB
MSEL1 (Pin 7)
MSEL0 (Pin 6)
L
L
L
M
L
H
M
L
M
M
M
H
H
L
H
M
H
H
Input/Output
frequency range [MHz]
SS mode
SS modulation*1 [%]
± 1.25
12 to 18
(Low range)
Center spread
± 0.75
± 1.75
± 2.25
(reserved)*2
± 2.25
18 to 32
(High range)
Center spread
± 1.25
± 0.75
± 1.75
*1. The modulation rates in the table above are reference values at 12MHz (Low range) and 24MHz (High range). The modulation rate varies with the input/output frequency.
*2. If MSEL1 (pin 7) and MSEL0 (pin 6) are both simultaneously "M" level, then SM8761AB operation cannot be guaranteed.
Note. Signal level “H” represents VDD level, “L” represents VSS level, and “M” represents 1/2VDD.
NIPPON PRECISION CIRCUITS INC.—8
SM8761 series
Typical Connection Circuit
A typical connection circuit diagram is shown in Figure 4.
1) The SM8761 series oscillator circuit between XT and XTN has a built-in feedback resistor (approximately
250kΩ).
2) The oscillator circuit capacitances C101 and C102 connected to XTN and XT, to match the crystal load
capacitor.
3) If using an external clock input on XT, then connections to XT and XTN should be as shown in figure 3.
4) R201 is impedance matching resistor for board pattern.
5) C201 and C202 are bypass capacitors inserted between the supply voltage lines.
C201 is a 0.1µF (approximately) multi-layer ceramic capacitor connected directly alongside the SM8761
series.
C202 is a 33µF (approximately) electrolytic capacitor.
C102
C101
VSS
VSS
X'tal
VDD
+
XT
C202
33µF
C201
0.1µF
XTN
VDD
MSEL1
MSEL1
VSS
MSEL0
MSEL0
CLKOUT
VSS
TSTN
IC1
SM8761
Application Load
R201
0 to 22Ω
VSS
Note. This is a sample connection diagram only, and its use is not a guarantee of SM8761 series device characteristics.
Figure 4. Typical connection circuit
MSEL1 and MSEL0 Connection Method
MSEL1 and MSEL0 both support a 1/2VDD "M" level for 3-value ("H", "M", "L") DC voltage input control.
Typical connection circuits for each input level shown in figure 5. "H" level is input by connection to VDD, and
"L" level by connection to VSS. "M" level is input by connection to the center tap of two identical resistances
in series between VDD and VSS. The recommended resistance is 4.7kΩ.
VDD
VDD
R301
4.7kΩ
XTN
XTN
MSEL1
MSEL1
MSEL1
MSEL0
MSEL0
XTN
TSTN
MSEL0
R302
4.7kΩ
TSTN
TSTN
VSS
VSS
(a)“H” level
(b)“M” level
(c)“L” level
Figure 5. MSEL1 and MSEL0 typical connections
NIPPON PRECISION CIRCUITS INC.—9
SM8761 series
CLKOUT Output Spectrum Sample (SM8761AA)
A sample SM8761AA CLKOUT output spectrum is shown in Figure 6.
MKR:33.200MHz
9.37dBm
RL:10.0dBm
10dB/AT30dB
CNF:33.2MHz
SPF:3.3MHz
W:A
ST 3s
D:PK
RB3kHz
VB1kHz
(a) NPC test mode: SS OFF, fin = 33.2MHz
MKR:32.434MHz
−5.19dBm
RL:10.0dBm
10dB/AT30dB
CNF:33.2MHz
SPF:3.3MHz
W:A
ST 3s
D:PK
RB3kHz
VB1kHz
(b) MSEL1 = "L"/ MSEL0 = “H”: down spread –2.8%, fin = 33.2MHz
Figure 6. Output spectrum sample
Note. The output spectrum sample in figure (a) is for NPC test mode with the SS function OFF.
Note. These spectrum diagrams were obtained using the NPC evaluation board. These spectrum diagrams are not guaranteed SM8761 series device
characteristics.
NIPPON PRECISION CIRCUITS INC.—10
SM8761 series
Please pay your attention to the following points at time of using the products shown in this document.
The products shown in this document (hereinafter “Products”) are not intended to be used for the apparatus that exerts harmful influence on
human lives due to the defects, failure or malfunction of the Products. Customers are requested to obtain prior written agreement for such
use from NIPPON PRECISION CIRCUITS INC. (hereinafter “NPC”). Customers shall be solely responsible for, and indemnify and hold NPC
free and harmless from, any and all claims, damages, losses, expenses or lawsuits, due to such use without such agreement. NPC reserves
the right to change the specifications of the Products in order to improve the characteristic or reliability thereof. NPC makes no claim or
warranty that the contents described in this document dose not infringe any intellectual property right or other similar right owned by third
parties. Therefore, NPC shall not be responsible for such problems, even if the use is in accordance with the descriptions provided in this
document. Any descriptions including applications, circuits, and the parameters of the Products in this document are for reference to use the
Products, and shall not be guaranteed free from defect, inapplicability to the design for the mass-production products without further testing
or modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any entity not in
compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are requested
appropriately take steps to obtain required permissions or approvals from appropriate government agencies.
NIPPON PRECISION CIRCUITS INC.
4-3, Fukuzumi 2-chome, Koto-ku,
Tokyo 135-8430, Japan
Telephone: +81-3-3642-6661
Facsimile: +81-3-3642-6698
http://www.npc.co.jp/
Email: [email protected]
NC0408AE
2004.12
NIPPON PRECISION CIRCUITS INC.—11