参数资料
型号: AD9627ABCPZ-80
厂商: Analog Devices Inc
文件页数: 36/76页
文件大小: 0K
描述: IC ADC 12BIT 80MSPS 64LFCSP
标准包装: 1
位数: 12
采样率(每秒): 80M
数据接口: 串行,SPI?
转换器数目: 2
功率耗散(最大): 490mW
电压电源: 模拟和数字
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 64-VFQFN 裸露焊盘,CSP
供应商设备封装: 64-LFCSP-VQ(9x9)
包装: 托盘
输入数目和类型: 4 个单端,单极;2 个差分,单极
AD9627
Rev. B | Page 41 of 76
SERIAL PORT INTERFACE (SPI)
The AD9627 serial port interface (SPI) allows the user to configure
the converter for specific functions or operations through a
structured register space provided inside the ADC. The SPI
gives the user added flexibility and customization, depending on
the application. Addresses are accessed via the serial port and
can be written to or read from via the port. Memory is organized
into bytes that can be further divided into fields, which are docu-
mented in the Memory Map section. For detailed operational
information, see Application Note AN-877, Interfacing to High
Speed ADCs via SPI.
CONFIGURATION USING THE SPI
Three pins define the SPI of this ADC: the SCLK/DFS pin, the
SDIO/DCS pin, and the CSB pin (see Table 22). The SCLK/DFS
(a serial clock) is used to synchronize the read and write data
presented from and to the ADC. The SDIO/DCS (serial data
input/output) is a dual-purpose pin that allows data to be sent
and read from the internal ADC memory map registers. The
CSB (chip select bar) is an active-low control that enables or
disables the read and write cycles.
Table 22. Serial Port Interface Pins
Pin
Function
SCLK
Serial Clock. The serial shift clock input, which is used to
synchronize serial interface reads and writes.
SDIO
Serial Data Input/Output. A dual-purpose pin that
typically serves as an input or an output, depending on
the instruction being sent and the relative position in the
timing frame.
CSB
Chip Select Bar. An active-low control that gates the read
and write cycles.
The falling edge of the CSB, in conjunction with the rising edge
of the SCLK, determines the start of the framing. An example of
the serial timing and its definitions can be found in Figure 73
Other modes involving the CSB are available. The CSB can be
held low indefinitely, which permanently enables the device;
this is called streaming. The CSB can stall high between bytes to
allow for additional external timing. When CSB is tied high, SPI
functions are placed in high impedance mode. This mode turns
on any SPI pin secondary functions.
During an instruction phase, a 16-bit instruction is transmitted.
Data follows the instruction phase, and its length is determined
by the W0 and W1 bits.
All data is composed of 8-bit words. The first bit of each individual
byte of serial data indicates whether a read command or a write
command is issued. This allows the serial data input/output
(SDIO) pin to change direction from an input to an output.
In addition to word length, the instruction phase determines
whetherthe serial frame is a read or write operation, allowing
the serial port to be used both to program the chip and to read
the contents of the on-chip memory. If the instruction is a readback
operation, performing a readback causes the serial data input/
output (SDIO) pin to change direction from an input to an output
at the appropriate point in the serial frame.
Data can be sent in MSB-first mode or in LSB-first mode. MSB
first is the default on power-up and can be changed via the SPI
port configuration register. For more information about this
and other features, see Application Note AN-877, Interfacing to
High Speed ADCs via SPI.
HARDWARE INTERFACE
The pins described in Table 22 comprise the physical interface
between the user programming device and the serial port of the
AD9627. The SCLK pin and the CSB pin function as inputs
when using the SPI interface. The SDIO pin is bidirectional,
functioning as an input during write phases and as an output
during readback.
The SPI interface is flexible enough to be controlled by either
FPGAs or microcontrollers. One method for SPI configuration
is described in detail in Application Note AN-812, Microcontroller-
Based Serial Port Interface (SPI) Boot Circuit.
The SPI port should not be active during periods when the full
dynamic performance of the converter is required. Because the
SCLK signal, the CSB signal, and the SDIO signal are typically
asynchronous to the ADC clock, noise from these signals can
degrade converter performance. If the on-board SPI bus is used for
other devices, it may be necessary to provide buffers between
this bus and the AD9627 to prevent these signals from transi-
tioning at the converter inputs during critical sampling periods.
Some pins serve a dual function when the SPI interface is not
being used. When the pins are strapped to AVDD or ground
during device power-on, they are associated with a specific
function. The Digital Outputs section describes the strappable
functions supported on the AD9627.
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