FUJITSU SEMICONDUCTOR
DATA SHEET
DS04–29146–4E
ASSP
Spread Spectrum Clock Generator
MB88R157A
■
DESCRIPTION
MB88R157A is a clock generator for EMI (Electro Magnetic Interference) reduction. The peak of unnecessary
radiation noise (EMI) can be attenuated by making the oscillation frequency slightly modulate periodically
with the internal modulator.
This product has a built-in non-volatile memory, so its frequency setting can memorize each system or
application.
Also the product has a built-in oscillation stabilization circuit, so it is not necessary to use the external
oscillation stabilization capacitance.
■
FEATURES
• Input frequency
• Output frequency
: 10 MHz to 50 MHz
: 1 MHz to 134 MHz
Programmable of the parameter of N divider, M divider, K divider
(N divider : 11-bit, M divider : 12-bit, K divider : 7-bit)
: no modulation,
±0.125%, ±0.25%, ±0.5%, ±0.75%, ±1.0%, ±1.25%, ±1.5%, ±1.75%
• Modulation rate
• Variable function pin
It is possible to switch the VF pin function by setting to a non-volatile memory.
Modulation enabled: It is possible to turn on/off the modulation operation.
Power down control
Output setting selection: It is possible to save two types of frequency setting into a non-volatile memory,
and to select the type to operate.
• Equipped with a crystal oscillation circuit
• Built-in oscillation stabilization capacitance : 5 pF to 10 pF (0.039 pF step range)
• Clock output Duty : 40% to 60% (Load capacitance 15 pF or less)
• Clock Cycle-Cycle Jitter : Less than 100 ps (Output clock is over 3 MHz)
• Low power consumption by CMOS process 5 mA (24 MHz, Typ-sample, no load) [Target value]
(Input frequency : 24 MHz, N divider parameter : 200, M divider parameter : 200, K divider parameter : 1)
• At power down: 5
μA
(Power supply voltage
=
3.3 V, at room temperature) [Target value]
• Non-volatile memory : FRAM (data retention : 10 years (
+
85
°C))
• Power supply voltage : 2.7 V to 3.6 V
• Operating temperature
−20 °C
to
+
85
°C
• Package : 8-pin plastic TSSOP
Copyright©2010-2012 FUJITSU SEMICONDUCTOR LIMITED All rights reserved
2012.9
MB88R157A
■
PIN ASSIGNMENT
TOP VIEW
XOUT
OE
SP
VSS
1
2
3
4
8
7
6
5
XIN
VDD
VF
OUT
(FPT-8P-M07)
■
PIN DESCRIPTION
Pin name
XOUT
OE
SP
VSS
OUT
I/O
O
I
I/O
⎯
O
Pin no.
1
2
3
4
5
Description
Crystal oscillator connection pin
Clock output enable pin
L : output disable, H : output enable
Serial program pin
GND pin
Clock output pin
Variable function pin
It is possible to set the pin function to one of the followings by
setting to a memory.
<Modulation enable>
L : Modulation disable, H: Modulation enable
<Power down control>
Power down by the “L” input
<Output setting select>
L : 1 setting, H : 2 setting
Power supply voltage pin
Crystal oscillator connection pin/clock input pin
VF
I
6
VDD
XIN
⎯
I
7
8
2
DS04–29146–4E
MB88R157A
■
I/O CIRCUIT TYPE
Pin
name
OE
Circuit type
Remarks
• CMOS hysteresis input
• With pull-up resistor (50 kΩ)
VF
CMOS hysteresis input
SP
With pull-up resistor (50 kΩ)
In input mode
• CMOS hysteresis input
In serial output mode
• CMOS output
• I
OL
=
12 mA
OUT
• CMOS output
• I
OL
=
4 mA/8 mA selectable
(Selectable by Output driver setting
bit)
• Hi-Z or “L” output at OE pin
=
“L” input
(Selectable by OUT pin setting bit)
Note: About XIN and XOUT pins, please refer to “■ CRYSTAL OSCILLATION CIRCUIT”.
DS04–29146–4E
3
MB88R157A
■
HANDLING DEVICES
1. Preventing Latch-up
A latch-up can occur if, on this device, (a) a voltage higher than power supply voltage or a voltage lower
than GND is applied to an input or output pin or (b) a voltage higher than the rating is applied between power
supply and GND. The latch-up, if it occurs, significantly increases the power supply current and may cause
thermal destruction of an element. When you use this device, be very careful not to exceed the maximum
rating.
2. Handling unused pins
Do not leave an unused input pin open, since it may cause a malfunction.
When SP pin is not in use, please connect it to VDD power supply. Handle by other unused pins, using a
pull-up or pull-down resistor.
3. Notes for when the external clock is used
To use an external clock signal, input the clock signal to the XIN pin and the XOUT pin set open.
4. Power supply pins
Please design connecting the power supply pin of this device by as low impedance as possible from the
current supply source.
We recommend connecting electrolytic capacitor (about 10
μF)
and the ceramic capacitor (about 0.01
μF)
in
parallel between power supply and GND near the device, as a bypass capacitor.
5. Crystal Oscillation circuit
Noise near the XIN pin and XOUT pin may cause the device to malfunction. Design printed circuit boards
so that electric wiring of the XIN pin or the XOUT pin and the crystal oscillator do not intersect other wiring.
Design the printed circuit board that surrounds the XIN pin and XOUT pin with ground in order to stabilize
operation.
4
DS04–29146–4E
MB88R157A
■
BLOCK DIAGRAM
VDD
Output control
OE
XIN
N div.
OSC
Frequency
phase
comparison
Charge
Pump
Loop
Filter
VCO
K
div.
OUT
XOUT
M div
PLL block
Non-volatile memory
Serial-I/F
Serial data
SP
Modulation control
circuit
VF
VSS
IDAC (current output D/A converter) provides precise modulation, thereby dramatically reducing EMI.
DS04–29146–4E
5
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