ASM3P2853 D

ASM3P2853A
Peak EMI Reducing Solution
Features
• Generates an EMI optimized clock signal at output.
• Input frequency: 25MHz.
• Frequency outputs:
o USB Clock (48MHz unmodulated)
o 50MHz (modulated), ±1% centre spread
• Modulation rate: 39KHz.
• Spread Spectrum ON/OFF control
• Supply voltage range 2.5V ± 5%.
• Available in 8-Pin SOIC package.
by reducing the number of circuit board layers and
shielding that are required to pass EMI regulations. The
ASM3P2853A modulates the output of PLL in order to
spread the bandwidth of a synthesized clock, thereby
decreasing the peak amplitudes of its harmonics. This
results in significantly lower system EMI compared to the
typical narrow band signal produced by oscillators and
most clock generators. Lowering EMI by increasing a
signal’s bandwidth is called spread spectrum clock
generation.
Applications
Product Description
The ASM3P2853A is a versatile spread spectrum
frequency modulator. The ASM3P2853A reduces
electromagnetic interference (EMI) at the clock source.
The ASM3P2853A allows significant system cost savings
ASM3P2853A is targeted towards EMI management for
high speed digital applications such as PC peripheral
devices, consumer electronics and embedded controller
systems.
Block Diagram
VDD
XIN
XOUT
Crystal
Oscillator
SSONB
PWDNB
PLL1
USB Clock
(48MHz
Unmodulated)
PLL2
50MHz
Modulated
VSS
©2010 SCILLC. All rights reserved.
FEBRUARY 2012 – Rev. 3
Publication Order Number:
ASM3P2853/D
ASM3P2853A
Pin Configuration
XIN
1
XOUT
2
8
50MHz
7
USB Clock
ASM3P2853A
VDD
3
6
SSONB
VSS
4
5
PWDNB
Pin Description
Pin#
Pin
Name
Type
1
XIN
I
Description
Connection to crystal or external reference frequency input. This pin has dual
functions. It can be connected either to an external crystal or an external
reference clock.
Connection to crystal. If using an external reference clock, this pin must be left
2
XOUT
O
3
VDD
P
Power supply for the analog and digital blocks.
4
VSS
P
Ground to entire chip.
5
PWDNB
I
6
SSONB
I
7
8
USB
Clock
50MHz
unconnected.
Power-down control pin. Pull low to enable the power-down mode. Connect to
VDD, if not used.
Digital logic input used to enable spread spectrum function (Active LOW).
Spread spectrum is enabled when LOW, disabled when HIGH.
O
Clock output-1 (48MHz unmodulated).
O
Clock output-2 (50MHz modulated).
Rev. 2 | Page 2 of 7 | www.onsemi.com
ASM3P2853A
Absolute Maximum Ratings
Symbol
VDD, VIN
TSTG
Rating
Unit
Voltage on any pin with respect to Ground
Parameter
-0.5 to +4.6
V
Storage temperature
-65 to +125
°C
Ts
Max. Soldering Temperature (10 sec)
260
°C
TJ
TDV
Junction Temperature
Static Discharge Voltage (As per JEDEC STD22- A114-B)
150
2
°C
KV
Note: These are stress ratings only and are not implied for functional use. Exposure to absolute maximum ratings for prolonged periods of time may affect
device reliability.
Operating Conditions
Parameter
Symbol
Supply Voltage
Ambient Operating
Temperature Range
Crystal Resonator Frequency
Output Driver Load Capacitance
Condition / Description
VDD
2.5V ± 5%
TA
Min
Typ
Max
2.375
2.5
2.625
V
-40
-
+85
°C
FXIN
25
CL
-
-
MHz
15
Crystal Specifications
Fundamental AT cut parallel resonant crystal
Nominal frequency
25MHz
Frequency tolerance
±50ppm or better at 25°C
Operating temperature range
-25°C to +85°C
Storage temperature
-40°C to +85°C
Load capacitance
18pF
Shunt capacitance
7pF maximum
ESR
25Ω
Note: CY is Load Capacitance and Rx is used to prevent oscillations at overtone frequency of the Fundamental frequency.
Typical Crystal Interface Circuit
R
Crystal
XIN
Rx
XOUT
CY
CY
CY = 2*(CP – CS),
Where CP = Load capacitance of crystal from crystal vendor datasheet
CS = Stray capacitance due to CIN, PCB, Trace etc.
Rev. 2 | Page 3 of 7 | www.onsemi.com
Unit
pF
ASM3P2853A
DC Electrical Characteristics
Parameter
Symbol
Conditions / Description
Min
Typ
Max
Unit
IDD
VDD = 2.5V, FXIN = 25MHz, CL = 15pF
7
13
20
mA
IDDL
VDD = 2.5V, XIN = 0, PWDNB = 0
-
12
-
uA
Overall
Supply Current,
Dynamic
Supply Current,
Static
All input pins
High-Level Input
Voltage
Low-Level Input
Voltage
High-Level Input
Current
Low-Level Input
Current (pull-up)
VIH
VDD = 2.5V
1.7
-
-
V
VIL
VDD = 2.5V
-
-
0.7
V
IIH
-
-
25
µA
IIL
-
-
-25
µA
Clock Outputs
High-Level Output
Source Current
Low-Level Output
Sink Current
High-Level Output
Source Current
Low-Level Output
Sink Current
Output Impedance
IxOH
VDD = 2.5V ,V(XIN) = 0, VO = 2V
-
-15
-
mA
IxOL
VDD = V(XIN) = 2.5V, VO = 0.4V
-
15
-
mA
IOH
VO = 2V
-
8
-
mA
IOL
VO = 0.4V
-
8
-
mA
-
42
-
Ω
ZO
Rev. 2 | Page 4 of 7 | www.onsemi.com
ASM3P2853A
AC Electrical Characteristics
Parameter
1
Symbol
Min
Typ
Max
Unit
-
2
-
nS
-
1.5
-
nS
tjc
-
250
-
pS
tp
-
175
-
pS
45
50
55
%
-
-
5
mS
Measured from 20% to 80% of the
Rise Time
tr
1
tf
Fall Time
Jitter
(Cycle-to-Cycle)
Jitter
(Period)
Conditions / Description
signal level
Measured from 80% to 20% of the
signal level
Ratio of pulse width (as measured from
Clock Duty Cycle
td
rising edge to next falling edge at
VDD/2) to one clock period
Power-up time
tON
first locked cycle after power-up
(With stable VDD and valid input clock)
Note: 1. CL = 15 pF, Input clock frequency = 25MHz
Typical Application Schematic using ASM3P2853A Device
25MHz
fundamental
Crystal
1
XIN
2
XOUT
3
VDD
50MHz
8
USB Clock
7
SSONB
B
VSS
PWDNB
ASM3P2853A
6
27pF
+2.5V
Modulated 50MHz output
27pF
4
0.1uF
5
Rev. 2 | Page 5 of 7 | www.onsemi.com
Un-modulated 48MHz output
ASM3P2853A
Package Information
8-Pin SOIC package
H
E
D
A2
A
θ
C
D
e
A1
L
B
Dimensions
Symbol
Inches
Min
Max
Millimeters
Min
Max
A1
0.004
0.010
0.10
0.25
A
0.053
0.069
1.35
1.75
A2
0.049
0.059
1.25
1.50
B
0.012
0.020
0.31
0.51
C
0.007
0.010
0.18
0.25
D
0.193 BSC
4.90 BSC
E
0.154 BSC
3.91 BSC
e
0.050 BSC
1.27 BSC
H
0.236 BSC
6.00 BSC
L
0.016
0.050
θ
0°
8°
0.41
1.27
0°
8°
Coplanarity ≤ 4 mil
Rev. 2 | Page 6 of 7 | www.onsemi.com
ASM3P2853A
Ordering Code
Part number
Marking
ASM3P2853AG-08SR
AEC
Package Configuration
8-pin SOIC, TAPE & REEL, Green
Temperature Range
0°C to +70°C
A “microdot” placed at the end of last row of marking or just below the last row toward the center of package indicates Pb-free.
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