DATASHEET
2.5 VOLT LOW EMI CLOCK GENERATOR
Description
The MK1728A-01 generates a low EMI output clock from a
clock or crystal input. Operating at 2.5 V, the part is
designed to dither the LCD interface clock for PDAs,
printers, scanners, modems, copiers, and other
applications. Using IDT’s proprietary mix of analog and
digital Phase-Locked Loop (PLL) technology, the device
spreads the frequency spectrum of the output, reducing the
frequency amplitude peaks by several dB. The
MK1728A-01 offers both centered and down spread from a
high-speed crystal or clock input.
IDT offers many other clocks for computers and computer
peripherals. Consult IDT when you need to remove crystals
and oscillators from your board.
MK1728A-01
Features
•
Operating voltage of 2.5 V
•
Packaged in 8-pin SOIC/TSSOP
•
Provides a spread spectrum (Center and down spread)
clock output
•
Accepts a clock or crystal input (provides same
frequency dithered output)
•
Input frequency range of 4 to 36 MHz
•
Output frequency range of 4 to 36 MHz
(1X Multiplier)
•
Peak reduction by 8 dB to 16 dB typical on 3rd through
19th odd harmonics
•
Low EMI feature can be disabled
•
3.3 V tolerant inputs (S0,S1, FRSEL, X1)
•
Advanced, low-power CMOS process
Block Diagram
VDD
S1:0
2
PLL Clock
Synthesis
and Spread
Spectrum
Circuitry
X1
Clock Buffer/
Crystal
Oscillator
FRSEL
SSCLK
X1/ICLK
X2
External caps required with crystal for
accurate tuning of the clock
GND
IDT®
2.5 VOLT LOW EMI CLOCK GENERATOR
1
MK1728A-01
REV C 081413
MK1728A-01
2.5 VOLT LOW EMI CLOCK GENERATOR
SSCG
Pin Assignment
Spread Direction and Percentage
Select Table
8
7
6
5
X1/ICLK
S1
SSCLK
S0
X2
VDD
GND
FRSEL
1
2
3
4
S1
Pin 7
0
0
0
M
M
M
1
1
1
FRSEL
(pin 4)
0
1
M
S0
Pin 5
0
M
1
0
M
1
0
M
1
Spread
Direction
Center
Center
Center
Center
No Spread
Down
Down
Down
Down
Typical Spread
Percentage (%)
±0.5
±1.0
±1.5
±2.0
-
-0.5
-1.0
-1.5
-2.0
Multiplier
X1
X1
X1
Output
Freq. Range
4.0 to 8.0 MHz
8.0 to 16.0MHz
16.0 to 36.0MHz
8 pin (150 mil) SOIC/TSSOP
Input
Freq. Range
4.0 to 8.0 MHz
8.0 to 16.0MHz
16.0 to 36.0MHz
0 = connect to GND
M = unconnected (floating)
1 = connect directly to VDD
Pin Descriptions
Pin
Number
Pin
Name
Pin Type
Pin Description
1
2
3
4
5
6
7
8
X2
VDD
GND
FRSEL
S0
SSCLK
S1
X1/ICLK
XO
Power
Power
Input
Input
Output
Input
Input
Crystal connection to a 4 to 36 MHz crystal. Leave unconnected for clock.
Connect to +2.5 V.
Connect to ground.
Function select for input frequency range. Default to mid-level “M”.
Function select 0 input. Selects spread amount and direction per table above
(default-internal mid-level).
Clock output with spread spectrum.
Function select 1 input. Selects spread amount and direction per table above
(default-internal mid-level).
Connect to a 4 to 36 MHz crystal or clock.
IDT®
2.5 VOLT LOW EMI CLOCK GENERATOR
2
MK1728A-01 REV C 081413
MK1728A-01
2.5 VOLT LOW EMI CLOCK GENERATOR
SSCG
External Components
The MK1728A-01 requires a minimum number of external
components for proper operation.
same side of the board, minimizing vias through other signal
layers. Other signal traces should be routed away from the
MK1728A-01. This includes signal traces just underneath
the device, or on layers adjacent to the ground plane layer
used by the device.
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between VDD and GND on pins 2 and 3, as close to these
pins as possible. For optimum device performance, the
decoupling capacitor should be mounted on the component
side of the PCB. Avoid the use of vias in the decoupling
circuit.
Crystal Information
The crystal used should be a fundamental mode (do not use
third overtone), parallel resonant. Crystal capacitors should
be connected from pins X1 to ground and X2 to ground to
optimize the initial accuracy. The value of these capacitors
is given by the following equation:
Crystal caps (pF) = (C
L
- 6) x 2
In the equation, C
L
is the crystal load capacitance. So, for a
crystal with a 16 pF load capacitance, two 20 pF [(16-6) x 2]
capacitors should be used.
Series Termination Resistor
When the PCB trace between the clock output and the load
is over 1 inch, series termination should be used. To series
terminate a 50 trace (a commonly used trace impedance)
place a 33 resistor in series with the clock line, as close to
the clock output pin as possible. The nominal impedance of
the clock output is 20.
Tri-level Select Pin Operation
The S1, S0, and FRSEL select pins are tri-level, meaning
they have three separate states to make the selections
shown in the table on page 2. To select the M (mid) level, the
connection to these pins must be eliminated by either
floating them originally, or tri-stating the GPIO pins which
drive the select pins.
Spread Spectrum Profile
The MK1728A-01 low EMI clock generator uses an
optimized frequency slew rate algorithm to facilitate down
stream tracking of zero delay buffers and other PLL devices.
The frequency modulation amplitude is constant with
variations of the input frequency.
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
1) The 0.01µF decoupling capacitor should be mounted on
the component side of the board as close to the VDD pin as
possible. No vias should be used between the decoupling
capacitor and VDD pin. The PCB trace to VDD pin should
be kept as short as possible, as should the PCB trace to the
ground via.
2) To minimize EMI, the 33 series termination resistor (if
needed) should be placed close to the clock output.
3) An optimum layout is one with all components on the
Modulation Rate
Frequency
Time
IDT®
2.5 VOLT LOW EMI CLOCK GENERATOR
3
MK1728A-01 REV C 081413
MK1728A-01
2.5 VOLT LOW EMI CLOCK GENERATOR
SSCG
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the MK1728A-01. These ratings, which
are standard values for IDT commercially rated parts, are stress ratings only. Functional operation of the device at
these or any other conditions above those indicated in the operational sections of the specifications is not implied.
Exposure to absolute maximum rating conditions for extended periods can affect product reliability. Electrical
parameters are guaranteed only over the recommended operating temperature range.
Item
Supply Voltage, VDD
All Outputs
All Inputs
Ambient Operating Temperature
Storage Temperature
Junction Temperature
Soldering Temperature
7V
Rating
-0.5 V to VDD+0.5 V
-0.5 V to 3.6 V
0 to +70C
-65 to +150C
125C
260C
Recommended Operation Conditions
Parameter
Ambient Operating Temperature
Power Supply Voltage (measured in respect to GND)
Min.
0
+2.375
Typ.
2.5
Max.
+70
2.625
Units
C
V
DC Electrical Characteristics
Unless stated otherwise,
VDD = 2.5 V,
Ambient Temperature 0 to +70C
Parameter
Operating Voltage
Supply Current
Input High Voltage
Input High Voltage
Input Middle Voltage
Input Low Voltage
Input Low Voltage
Output High Voltage
Output High Voltage
Output Low Voltage
Input Capacitance
Short Circuit Current
Symbol
VDD
IDD
V
IH
V
IH
V
IM
V
IL
V
IL
V
OH
V
OH
V
OL
C
IN1
C
IN2
I
OS
Conditions
No load, at 2.5 V,
Fin=32 MHz
FRSEL, S1:S0
ICLK
FRSEL, S1:S0
FRSEL, S1:S0
ICLK
I
OH
= -4 mA
I
OH
= -10 mA
I
OL
= 10 mA
S0, S1, FRSEL pins
X1, X2 pins
Min.
2.375
Typ.
2.5
10
Max.
2.625
15
Units
V
mA
V
V
VDD-0.6
1.7
VDD-1.8
VDD-0.7
0.6
0.7
VDD-0.4
2.0
0.4
4
6
±50
6
9
V
V
V
V
V
V
pF
pF
mA
IDT®
2.5 VOLT LOW EMI CLOCK GENERATOR
4
MK1728A-01 REV C 081413
MK1728A-01
2.5 VOLT LOW EMI CLOCK GENERATOR
SSCG
AC Electrical Characteristics
Unless stated otherwise,
VDD = 2.5 V,
C
L
=15 pF, Ambient Temperature 0 to +70 C
Parameter
Input Clock Frequency
Output Clock Frequency
Input Clock Duty Cycle
Output Clock Duty Cycle
Cycle to Cycle Jitter
Output Rise Time
Output Fall Time
Modulation Rate
EMI Peak Frequency Reduction
Symbol
Conditions
Crystal or Clock
Time above VDD/2
Time above 1.25 V
Min.
4
4
45
40
1.6
1.6
Typ.
Max. Units
36
36
55
MHz
MHz
%
%
ps
ns
ns
kHz
dB
50
200
2.8
2.8
32
8 to 16
60
300
4
4
t
R
t
F
F
MOD
20% to 80% of VDD
80% to 20% of VDD
Fin=24 MHz
Thermal Characteristics – 8 SOIC
Parameter
Thermal Resistance Junction to
Ambient
Symbol
JA
JA
JA
JC
Conditions
Still air
1 m/s air flow
3 m/s air flow
Min.
Typ.
150
140
120
40
Max. Units
C/W
C/W
C/W
C/W
Thermal Resistance Junction to Case
Thermal Characteristics – 8 TSSOP
Parameter
Thermal Resistance Junction to
Ambient
Symbol
JA
JA
JA
JC
Conditions
Still air
1 m/s air flow
3 m/s air flow
Min.
Typ.
110
100
80
35
Max. Units
C/W
C/W
C/W
C/W
Thermal Resistance Junction to Case
IDT®
2.5 VOLT LOW EMI CLOCK GENERATOR
5
MK1728A-01 REV C 081413
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
