Connect to crystal or clock input. This pin has dual functions. It can be connected
either to an external crystal or an external reference clock.
Crystal connection. If using an external reference, this pin must be left
unconnected.
Digital logic input used to select input frequency range (see the
Input Frequency
Selection Table).
This pin has an internal pull-up resistor.
External Loop Filter for the PLL. By changing the value of the CRC circuit, the
percentage spread can be adjusted accordingly. See the
Loop Filter Selection
Table
for detail value.
Ground Connection. Connect to system ground.
Spread Spectrum Clock Output.
Digital logic input used to select input frequency range (see the
Input Frequency
Selection Table).
This pin has an internal pull-up resistor.
Connect to +3.3 V
Input Frequency Selection Table
FS1
0
0
1
1
FS0
0
1
0
1
Input (MHz)
3 to 9
10 to 19
20 to 38
39 to 78
Output Frequency Scaling (MHz)
P2781A
3 to 9
10 to 19
20 to 38
39 to 78
P2782A
6 to 18
20 to 38
40 to 76
78 to 156
P2784A
12 to 36
40 to 76
80 to 152
156 to 312
Modulation Rate (KHz)
Fin / 128
Fin / 256
Fin / 512
Fin / 1024
Rev. 2 | Page 2 of 8 | www.onsemi.com
P2781/82/84
Loop Filter Selection Table VDD 3.3V
Contact ON Semiconductor for loop values that are not listed in the table and for
Component selection values for industrial and automotive temperatures.
Input
MHz
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21-22
23-24
25-26
27-28
29-30
31-32
33-34
35-36
37-38
39-42
43-46
47-50
51-54
55-58
59-62
63-66
67-70
71-74
75-78
BW = ±0.50%
1
FS1 FS0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
C1
(pF)
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
C2
(pF)
330,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
R1
(ohm)
220
270
390
510
620
820
1,000
330
390
510
560
620
750
820
910
1,000
1,200
330
390
510
560
620
750
820
910
1,000
1,200
330
390
510
560
620
750
820
910
1,000
1,200
BW = ±0.75%
1
C1
(pF)
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
C2
(pF)
330,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100,000
R1
(ohm)
300
390
560
750
1,000
1,200
1,500
510
560
750
820
1,000
1,100
1,200
1,300
1,500
1,600
560
620
750
820
1,000
1,100
1,200
1,300
1,500
1,600
560
620
750
820
1,000
1,100
1,200
1,300
1,600
1,800
C1
(pF)
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
270
BW = ±1.00%
1
C2
(pF)
R1
(ohm)
C1
(pF)
560
560
560
680
330
680
270
560
560
680
470
330
330
680
390
270
270
560
560
680
470
330
330
680
390
270
270
560
560
680
470
330
330
680
390
270
270
BW = ±1.25%
1
C2
(pF)
100,000
100,000
100,000
6,800
3,300
6,800
2,700
100,000
100,000
6,800
4,700
3,300
3,300
6,800
3,900
2,700
2,700
100,000
100,000
6,800
4,700
3,300
3,300
6,800
3,900
2,700
2,700
100,000
100,000
6,800
4,700
3,300
3,300
6,800
3,900
2,700
2,700
R1
(ohm)
510
680
910
1,200
1,200
2,200
2,200
910
1,100
1,200
1,200
1,200
1,500
2,200
2,200
2,200
2,700
910
1,100
1,200
1,200
1,200
1,500
2,200
2,200
2,200
2,700
910
1,100
1,200
1,200
1,200
1,500
2,200
2,200
2,200
2,700
Note: 1. The BW value is representative of typical conditions.
100,000
390
100,000
560
100,000
750
10,000
1,000
5,600
1,200
12,000
2,200
5,600
2,200
100,000
750
100,000 866(1%)
10,000
1,000
12,000
1,200
5,600
1,200
3,900
1,200
12,000
2,200
10,000
2,200
5,600
2,200
3,300
2,200
100,000
750
100,000 866 (1%)
10,000
1,000
12,000
1,200
6,800
1,200
3,900
1,200
12,000
2,200
10,000
2,200
5,600
2,200
3,300
2,200
100,000
750
100,000 866 (1%)
10,000
1,000
12,000
1,200
6,800
1,200
3,900
1,200
12,000
2,200
8,200
2,200
5,600
2,200
3,300
2,200
Rev. 2 | Page 3 of 8 | www.onsemi.com
P2781/82/84
The P278xA performs Zero Cycle Slip when set at low percentage spreading. This allows no occurrence of system timing
error. The optimal setting should minimize system EMI to the fullest without affecting system performance. The spreading is
described as a percentage deviation of the center frequency.
(Note: the center frequency is the frequency of the external reference input on CLKIN, Pin 1.)
Spread Spectrum Selection
The P2781A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized for
operation between 3 to 78MHz range. In the following application schematic example, the P2781A spread percentage
selection is determined by the external LF value specified in the Loop Filter Selection Table. The
Input Frequency Selection
Table
specifies the input frequency range. The external LF allows the user to fine tune the spread percentage to optimize the
EMI reduction benefits of the spread spectrum.
+3.3V
16 MHz
1
XIN/CLKIN VDD
8
2
XOUT
3
FS1
FS0
7
ModOUT
6
2.2 K
0.1µF
Modulated 16MHz Clock
To target Chip
C2
R1
C1
4
LF
0 Ohm
VSS
5
P278xA
Note: Both logic input pins FS1 and FS0 have to be connected to either VDD or VSS. Do not leave them floating.
Rev. 2 | Page 4 of 8 | www.onsemi.com
P2781/82/84
Absolute Maximum Ratings
Symbol
V
DD
, V
IN
T
STG
T
s
T
J
T
DV
Storage temperature
Max. Soldering Temperature (10 sec)
Junction Temperature
Static Discharge Voltage (As per JEDEC STD22- A114-B)
Parameter
Rating
-0.5 to +4.6
-65 to +125
260
150
2
Unit
V
°
C
°
C
°
C
KV
Voltage on any pin with respect to Ground
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
VDD
T
A
C
L
C
IN
Supply Voltage
Operating Temperature (Ambient Temperature)
Load Capacitance
Input Capacitance
Description
Min
3.0
-40
Max
3.6
+85
15
7
Unit
V
°
C
pF
pF
DC Electrical Characteristics
Symbol
V
IL
V
IH
I
IL
I
IH
I
XOL
I
XOH
V
OL
V
OH
I
DD
I
CC
VDD
Input low voltage
(Test condition: All parameters are measured at room temperature (+25° unless otherwise stated.)
I want to burn the lm3s800 program now. I have a hex file on hand. Since I don't know much about this chip, I don't know how to download it to the chip. I need help. I am willing to pay. QQ: 732144708...
[i=s]This post was last edited by neolee08 on 2018-6-21 09:08[/i] I have just entered the field of automotive electronics and am responsible for hardware design. I am not very familiar with automotive...
The basic principle and usage of RS485 communication are the same as RS232, with the following differences.The RS232 interface can only realize point-to-point communication, but this method cannot rea...
msp430f149 controls the transceiver integrated ultrasonic sensor to measure distance! Looking for a driver! I have tried for a long time but have no clue. I hope the masters who have done it can give ...
I installed the code of WindNet PPPOE1.2 and compiled it in Tornado2.2.1. Then I ran usrBasicPPPInit();usrBasicPPPoEInit();pfwStackAdd(pppOeSysProfile，&pplCallbacks,&MyHandle); and it showed pfwStackA...
Traditional broadcasting systems generally need to be operated manually at a fixed time, and can only realize one-way broadcasting with few functions. Traditional bell ringing equipment has a singl...[Details]
introduction
1 The significance of using RTOS on MSP430
It is understandable that it is meaningless to use RTOS on MSP430. Because the hardware resources of MSP430 are limited (for exampl...[Details]
A single-chip microcomputer is also called a single-chip microcontroller. It is not a chip that completes a certain logical function, but a computer system integrated into one chip. In general, a c...[Details]
1. Introduction
RFID (radio frequency identification) is a non-contact automatic identification technology that emerged in the 1990s. It uses the characteristics of radio frequency signal prop...[Details]
1. Circuit composition
The whole circuit consists of two parts:
1. Power saving control circuit
As shown in the figure below. Including delay circuit and drive circuit.
(1) Delay ci...[Details]
1. Introduction
With the growth of parking demand, the scale of parking lots is becoming larger and larger. A lot of research has been done on intelligent parking lots in China, but most of th...[Details]
Converged processors meet scalability requirements
In current embedded system design, solutions based on MCU, DSP, FPGA and ASIC account for more than 90% of the market share. These solutions ...[Details]
introduction
In the discharge process of tokamak plasma physics, the study of rupture and sawtooth is of great significance. Rupture and sawtooth exist in most tokamaks. Rupture is a notew...[Details]
Due to the significant increase in electronic devices in automotive and industrial applications, the automotive and industrial markets continue to play an important role in China's electronics in...[Details]
Electronic systems are located at different points on the automotive power bus and therefore often need to operate under very stringent power requirements. These include load dump, cold crank, very lo...[Details]
This paper establishes a fuel cell engine test platform based on the NI integrated hardware and software environment. This platform can realize the test and control of fuel cell engines and their a...[Details]
The data collector of the automatic weather station is generally designed based on a single-chip microcomputer or a PC/104 bus controller. It has the characteristics of good compatibility with PC, low...[Details]
1. Overview
The Virtual CAN Interface (VCI) function library is an application program interface specifically provided for the use of ZLGCAN devices on PCs. The functions in the library ar...[Details]
1. Project Introduction
Shandong Dezhou Xingtai Paper Co., Ltd. is a newly built high-end paperboard production enterprise with domestic leading level established by Shandong Zhaodongfang Pape...[Details]
1. Introduction
Testing the temperature of steel billets before rolling is an important measure to ensure the quality of steel. Traditional manual testing is difficult to ensure product qu...[Details]
Microcontroller MCU
京公网安备 11010802033920号
EEWORLD
