参数资料
型号: AD73311ARS
厂商: ANALOG DEVICES INC
元件分类: 通信及网络
英文描述: Low Cost, Low Power CMOS General Purpose Analog Front End
中文描述: SPECIALTY TELECOM CIRCUIT, PDSO20
封装: SSOP-20
文件页数: 11/36页
文件大小: 382K
代理商: AD73311ARS
REV. A
AD73311L
–11–
The output of the interpolation
fi
lter is fed to the DAC
s digital
sigma-delta modulator, which converts the 16-bit data to 1-bit
samples at a rate of DMCLK/8. The modulator noise-shapes
the signal so that errors inherent to the process are minimized
in the passband of the converter. The bitstream output of the
sigma-delta modulator is fed to the single bit DAC where it is
converted to an analog voltage.
Analog Smoothing Filter and PGA
The output of the single-bit DAC is sampled at DMCLK/8,
therefore it is necessary to
fi
lter the output to reconstruct the
low frequency signal. The decoder
s analog smoothing
fi
lter
consists of a continuous-time
fi
lter preceded by a third-order
switched-capacitor
fi
lter. The continuous-time
fi
lter forms part
of the output programmable gain ampli
fi
er (PGA). The PGA
can be used to adjust the output signal level from
15 dB to
+6 dB in 3 dB steps, as shown in Table IV. The PGA gain is
set by bits OGS0, OGS1 and OGS2 (CRD:4-6) in Control
Register D.
Table IV. PGA Settings for the Decoder Channel
OGS2
OGS1
OGS0
Gain (dB)
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
+6
+3
0
3
6
9
12
15
Differential Output Amplifiers
The decoder has a differential analog output pair (VOUTP and
VOUTN). The output channel can be muted by setting the
MUTE bit (CRD:7) in Control Register D. The output signal
is dc-biased to the codec
s on-chip voltage reference.
Voltage Reference
The AD73311L reference, REFCAP, is a bandgap reference
that provides a low noise, temperature-compensated reference
to the DAC and ADC. A buffered version of the reference is
also made available on the REFOUT pin and can be used to
bias other external analog circuitry. The reference has a default
nominal value of 1.2 V.
The reference output (REFOUT) can be enabled for biasing
external circuitry by setting the RU bit (CRC:6) of CRC.
Serial Port (SPORT)
The codec communicates with a host processor via the bidirec-
tional synchronous serial port (SPORT) which is compatible
with most modern DSPs. The SPORT is used to transmit and
receive digital data and control information.
In both transmit and receive modes, data is transferred at the
serial clock (SCLK) rate with the MSB being transferred
fi
rst.
Due to the fact that the SPORT uses a common serial register for
serial input and output, communications between an AD73311L
codec and a host processor (DSP engine) must always be initi-
ated by the codec itself. This ensures that there is no danger of
the information being sent to the codec being corrupted by
ADC samples being output by the codec.
SPORT Overview
The AD73311L SPORT is a flexible, full-duplex, synchronous
serial port whose protocol has been designed to allow up to eight
AD73311L devices to be connected, in cascade, to a single DSP
via a six-wire interface. It has a very flexible architecture that can
be con
fi
gured by programming two of the internal control regis-
ters. The AD73311L SPORT has three distinct modes of opera-
tion: Control Mode, Data Mode and Mixed Control/Data Mode.
In Control Mode (CRA:0 = 0), the device
s internal con
fi
gura-
tion can be programmed by writing to the
fi
ve internal control
registers. In this mode, control information can be written to or
read from the codec. In Data Mode (CRA:0 = 1), information
that is sent to the device is used to update the decoder section
(DAC), while the encoder section (ADC) data is read from the
device. In this mode, only DAC and ADC data is written to or
read from the device. Mixed mode (CRA:0 = 1 and CRA:1 = 1)
allows the user to choose whether the information being sent to
the device contains either control information or DAC data.
This is achieved by using the MSB of the 16-bit frame as a flag
bit. Mixed mode reduces the resolution to 15 bits with the MSB
being used to indicate whether the information in the 16-bit
frame is control information or DAC/ADC data.
The SPORT features a single 16-bit serial register that is used
for both input and output data transfers. As the input and out-
put data must share the same register there are some precautions
that must be observed. The primary precaution is that no infor-
mation must be written to the SPORT without reference to an
output sample event, which is when the serial register will be
overwritten with the latest ADC sample word. Once the SPORT
starts to output the latest ADC word then it is safe for the DSP
to write new control or data words to the codec. In certain con-
fi
gurations, data can be written to the device to coincide with
the output sample being shifted out of the serial register
see
section on interfacing devices. The serial clock rate (CRB:2
3)
de
fi
nes how many 16-bit words can be written to a device before
the next output sample event will happen.
The SPORT block diagram, shown in Figure 9, details the six
control registers (A
F), external MCLK to internal DMCLK
divider and serial clock divider. The divider rates are controlled
by the setting of Control Register B. The AD73311L features a
master clock divider that allows users the flexibility of dividing
externally available high frequency DSP or CPU clocks to gener-
ate a lower frequency master clock internally in the codec which
may be more suitable for either serial transfer or sampling rate
requirements. The master clock divider has
fi
ve divider options
(
÷
1 default condition,
÷
2,
÷
3,
÷
4,
÷
5) that are set by loading
the master clock divider
fi
eld in Register B with the appropriate
code. Once the internal device master clock (DMCLK) has
been set using the master clock divider, the sample rate and
serial clock settings are derived from DMCLK.
The SPORT can work at four different serial clock (SCLK) rates:
chosen from DMCLK, DMCLK/2, DMCLK/4 or DMCLK/8,
where DMCLK is the internal or device master clock resulting
from the external or pin master clock being divided by the
master clock divider. When working at the lower SCLK rate of
DMCLK/8, which is intended for interfacing with slower DSPs,
the SPORT will support a maximum of two devices in cascade
with the sample rate of DMCLK/256.
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AD73311ARSZ 功能描述:IC ANALOG FRONT END 20-SSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模拟前端 (AFE) 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 位数:- 通道数:2 功率(瓦特):- 电压 - 电源,模拟:3 V ~ 3.6 V 电压 - 电源,数字:3 V ~ 3.6 V 封装/外壳:32-VFQFN 裸露焊盘 供应商设备封装:32-QFN(5x5) 包装:带卷 (TR)
AD73311ARSZ-REEL 功能描述:IC ANALOG FRONT END 20-SSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模拟前端 (AFE) 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 位数:- 通道数:2 功率(瓦特):- 电压 - 电源,模拟:3 V ~ 3.6 V 电压 - 电源,数字:3 V ~ 3.6 V 封装/外壳:32-VFQFN 裸露焊盘 供应商设备封装:32-QFN(5x5) 包装:带卷 (TR)
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