ASM3P2853A
Peak EMI Reducing Solution
©2010 SCILLC. All rights reserved. Publication Order Number:
FEBRUARY 2012 – Rev. 3 ASM3P2853/D
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.
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
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
ASM3P2853A is targeted towards EMI management for
high speed digital applications such as PC peripheral
devices, consumer electronics and embedded controller
systems.
Block Diagram
V
SS
V
DD
Crystal
Oscillator
50MHz
Modulated
XIN
XOUT USB Clock
(48MHz
Unmodulated)
PLL1
PLL2
PWDNB
SSONB
ASM3P2853A
Rev. 2 | Page 2 of 7 | www.onsemi.com
Pin Configuration
Pin Description
Pin# Pin
Name Type Description
1 XIN I 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.
2 XOUT O Connection to crystal. If using an external reference clock, this pin must be left
unconnected.
3 V
DD
P Power supply for the analog and digital blocks.
4 V
SS
P Ground to entire chip.
5 PWDNB I Power-down control pin. Pull low to enable the power-down mode. Connect to
VDD, if not used.
6 SSONB I Digital logic input used to enable spread spectrum function (Active LOW).
Spread spectrum is enabled when LOW, disabled when HIGH.
7 USB
Clock O Clock output-1 (48MHz unmodulated).
8 50MHz O Clock output-2 (50MHz modulated).
50MHz
V
SS
XOUT
XIN
V
DD
8
7
6
5
1
2
3
4
ASM3P2853A
PWDNB
SSONB
USB Clock
ASM3P2853A
Rev. 2 | Page 3 of 7 | www.onsemi.com
Absolute Maximum Ratings
Symbol Parameter Rating Unit
VDD, V
IN
Voltage on any pin with respect to Ground -0.5 to +4.6 V
T
STG
Storage temperature -65 to +125 °C
T
s
Max. Soldering Temperature (10 sec) 260 °C
T
J
Junction Temperature 150 °C
T
DV
Static Discharge Voltage (As per JEDEC STD22- A114-B) 2 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 Condition / Description Min Typ Max Unit
Supply Voltage V
DD
2.5V ± 5% 2.375 2.5 2.625 V
Ambient Operating
Temperature Range T
A
-40 - +85 °C
Crystal Resonator Frequency F
XIN
25 MHz
Output Driver Load Capacitance C
L
- - 15 pF
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: C
Y
is Load Capacitance and Rx is used to prevent oscillations at overtone frequency of the Fundamental frequency.
Typical Crystal Interface Circuit
C
Y
= 2*(C
P
– C
S
),
Where C
P
= Load capacitance
of crystal from crystal vendor datasheet
C
S
= Stray capacitance due to C
IN,
PCB, Trace etc.
C
Y
Rx
C
Y
Crystal
R
XIN XOUT
ASM3P2853A
Rev. 2 | Page 4 of 7 | www.onsemi.com
DC Electrical Characteristics
Parameter Symbol Conditions / Description Min Typ Max Unit
Overall
Supply Current,
Dynamic I
DD
V
DD
= 2.5V, F
XIN
= 25MHz, C
L
= 15pF 7 13 20 mA
Supply Current,
Static I
DDL
V
DD
= 2.5V, X
IN
= 0, PWDNB = 0 - 12 - uA
All input pins
High-Level Input
Voltage V
IH
V
DD
= 2.5V 1.7 - - V
Low-Level Input
Voltage V
IL
V
DD
= 2.5V - - 0.7 V
High-Level Input
Current I
IH
- - 25 µA
Low-Level Input
Current (pull-up) I
IL
- - -25 µA
Clock Outputs
High-Level Output
Source Current I
xOH
V
DD
= 2.5V ,V(X
IN
) = 0, V
O
= 2V - -15 - mA
Low-Level Output
Sink Current I
xOL
V
DD
= V(X
IN
) = 2.5V, V
O
= 0.4V - 15 - mA
High-Level Output
Source Current I
OH
V
O
= 2V - 8 - mA
Low-Level Output
Sink Current I
OL
V
O
= 0.4V - 8 - mA
Output Impedance
Z
O
- 42
- Ω
ASM3P2853A
Rev. 2 | Page 5 of 7 | www.onsemi.com
AC Electrical Characteristics
Parameter Symbol Conditions / Description Min Typ Max Unit
Rise Time
1
t
r
Measured from 20% to 80% of the
signal level - 2 - nS
Fall Time
1
t
f
Measured from 80% to 20% of the
signal level - 1.5 - nS
Jitter
(Cycle-to-Cycle) t
jc
- 250 - pS
Jitter
(Period) t
p
- 175 - pS
Clock Duty Cycle t
d
Ratio of pulse width (as measured from
rising edge to next falling edge at
V
DD
/2) to one clock period 45 50 55 %
Power-up time t
ON
first locked cycle after power-up
(With stable V
DD
and valid input clock) - - 5 mS
Note: 1.
C
L
= 15 pF, Input clock frequency = 25MHz
Typical Application Schematic using ASM3P2853A Device
Modulated 50MHz output
1
2
3
4
XIN
XOUT
V
DD
V
SS
USB Clock
5
6
7
8
PWDNB
SSONB
B
50MHz
25MHz
fundamental
Crystal
+
2.5
V
ASM3P2853A
Un-modulated 48MHz output
27pF
27pF
0.1u
F
ASM3P2853A
Rev. 2 | Page 6 of 7 | www.onsemi.com
Package Information
8-Pin SOIC package
D
EH
D
A1
A2
A
θ
L
C
B
e
Symbol
Dimensions
Inches Millimeters
Min Max 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 0.41 1.27
θ 0° 8° 0° 8°
Coplanarity ≤ 4 mil
ASM3P2853A
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes
without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular
purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability,
including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or
specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be
validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others.
SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death
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its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising
out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC
was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. U.S Patent Pending; Timing-Safe
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For additional information, please contact your
local Sales Representative
Ordering Code
Part number Marking Package Configuration Temperature Range
ASM3P2853AG-08SR AEC 8-pin SOIC, TAPE & REEL, Green 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.
