Fujitsu MB88R157A Spread spectrum clock generator capable of freely setting the output clock frequency Datasheet

New Products
MB88R157A
Spread Spectrum Clock Generator
Capable of Freely Setting the Output
Clock Frequency
MB88R157A
We have added MB88R157A with built-in FRAM to our lineup of spread spectrum
clock generator (SSCG) products that are effective measures against EMI noise.
The output frequency can be set at the user ,s discretion between 1MHz and 134MHz
for the input frequency of 10MHz to 50MHz.
* SSCG: Spread Spectrum Clock Generator
* FRAM: Ferroelectric Random Access Memory (nonvolatile memory utilizing ferroelectric)
Introduction
In recent years, electronic devices have adopted higher
performance (speed) and smaller sizes (higher density) and, as
a result, their noise emission has been growing steadily. Noise
problems are often the final challenge to overcome prior to the
mass production of a product following the trial and error of
product design and evaluation. As electrical signals (the clock
frequency that operates a system) and noise are intrinsically
the same, it is important to take noise countermeasures into
consideration at the board system design stage of a product.
This product not only simplifies noise countermeasures but
also dramatically saves on the time spent developing noise
countermeasures later, thereby minimizing the cost and evaluation
time.
Our SSCG controls the clock frequency in an ideal fashion
by applying our proprietary digitally controlled (current D/A
converter) “frequency modulation technology” and “composite
modulation technology.” It achieves − 19dB (measurement value by
FUJITSU, 1.5% modulation degree used), which corresponds
Photo 1 External View
What is SSCG?
SSCG is a product that reduces the emission of unnecessary noise
by slightly fluctuating (modulating) the clock frequency that is the
source of noise in a range that does not affect the system operation.
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New Products
MB88R157A
to 1/100 in power.
The noise emitted from electrical devices (EMI) is regulated
by various international standards, including CISPR, as it has
negative effects (e.g., it can cause other electronic devices to
malfunction). Our SSCG digitally controls the clock frequency
that is the source of EMI noise. In this way, it is possible to avoid
unexpected noise generation and to easily satisfy international
standards.
Figure 1 presents a diagram of the spread spectrum, and
Figure 2 the EMI reduction effect on an actual board.
Product Features
MB88R157A we have developed is not dependent on the
input frequency and the output frequency can be set at the
user’s discretion. It is thus possible to generate a unique clock
frequency within digital devices such as TVs, DVD players and
audio devices that can simultaneously be utilized as a noise
countermeasure.
The major advantages of SSCG include the following:
Our proprietary digital control technology delivers a high noise
reduction effect; it is possible to evaluate the actual noise with
the product built onto the board.
● Figure 1 Spread Spectrum
-17.451dBm
40.11MHz
-27.136dBm
39.39MHz
−13dB
Conventional method
Our proprietary method
Figure 2 EMI Reduction Effect in Actual Boards
Electromagnetic
field map
−19dB
Figure 3 Pin Assignments
Large
EMI reduction effect is facilitated depending on the degree of modulation
Small
XOUT
XIN
OE
PEX
MB88R157A
(TOP VIEW)
VSS
Measurement range
Modulation OFF
1.0% modulation
NC
VDD
OUT
1.5% modulation
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FIND Vol.28
New Products
MB88R157A
A dramatic reduction in the number of conventional noise
countermeasure parts, such as shields, beads and capacitors, can
be realized.
Time and man-hours can be reduced dramatically compared
to conventional noise countermeasures that use parts (which
require evaluation and measure/layout change/building and
re-measurement).
Figure 3 presents the pin assignments, Table 1 the pin
functions and Table 2 the parameters that can be set through the
program.
● ● Evaluation Board and FRAM
Writing Environment
For this product, we offer an evaluation board and writing
environment with a built-in LSI to simplify single unit evaluation
and property check. We also offer a GUI program to enable the
simple calculation of the parameter data to be programmed as the
FRAM writing environment.
Figure 4 presents an example of a connection to a writing
environment.
Table 1 Pin Functions
Pin code
I/O
端子番号
Description of function
XOUT
O
1
Connection terminal for crystal oscillator
OE
I
2
Output enable terminal
SP
I/O
3
Serial program terminal
VSS
−
4
GND terminal
OUT
O
5
Clock output terminal
VF
I
6
Variable function terminal
*M odulation enable, power down control, Hi or Low output can be
set depending on the setting in the memory.
VDD
−
7
Power supply voltage terminal
XIN
I
8
Connection terminal/clock input for crystal oscillator
Table 2 Main Setup Functions
Functions set by the program
Function details
M/N/K divider parameter
The multiplication rate for output clock frequency can be set.
L divider parameter
Modulation cycle can be set.
Charge pump current/gain
An optimal value can be set for PLL oscillation frequency.
Modulation degree setting
The degree of modulation can be selected in units of 0.25% from
modulation off, ±0.25% to ±1.75% .
OUT terminal level
OUT terminal status can be set at L output or Hi-Z when OE
terminal = L.
Clock output drive capacity
The drive capacity for OUT terminal can be selected (2 stages).
XIN/XOUT terminal oscillation stability
capacity value
The built-in oscillation stability capacity can be set in units of
0.039pF from 5pF to 10pF each.
SS/PLL mode
Whether or not SS functions are used or the highly precise PLL
mode is used can be selected.
※A PC GUI software program to calculate the optimal parameter values in the table is available.
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New Products
MB88R157A
Lineup
After adding this programmable product (single output) to
the existing lineup of single output products, we will continue
to expand the lineup in the future to address the needs of our
customers.
Figure 5 presents the lineup of our clock generator products. ✱
Figure 4 Connection Example to a Writing Environment
GUI screen
DC power supply
3.3V
Crystal oscillator
(10 to 50MHz)
USB cable
PC
OE(SW1)
Connection cable
JP1
VDD
SP(SW2)
VSS
VF(SW3)
Writing tool I.S.P-310
MB88R157A evaluation board
Figure 5 Product Lineup
In mass
production
New product
In development
Multi-output product
Programmable
Output×6
Differential output
Serial I/F program
QFN-24-pin
(W2.5mm×L3.5mm)
Internal voltage 1.8V
External voltage 2.6V
Output×5
In planning
MB88182
32.768kHz master oscillation
MB8818×
Output×3
(W2.5mm×L3.5mm)
MB88185
Programmable
Single output products
TSSOP-8-pin
(W4.4mm×L3.1mm)
3.3V±0.3V
SOP-8
(W3.9mm×L5.05mm)
3.3V±0.3V
MB88151A
MB88152A
MB88R157A
Miniaturization
Low voltage operation
TSSOP-8-pin
(W4.4mm×L3.1mm)
3.3V±0.3V
SON-8-pin
(W2.0mm×L2.0mm)
1.8V±0.15V
MB88155
MB88163
MB88153A
MB88154A
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No.3
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