AD7495BRM Analog Devices Inc, AD7495BRM Datasheet - Page 22

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AD7495BRM

Manufacturer Part Number
AD7495BRM
Description
ADC Single SAR 1MSPS 12-Bit Serial 8-Pin MSOP
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD7495BRM

Package
8MSOP
Resolution
12 Bit
Sampling Rate
1000 KSPS
Architecture
SAR
Number Of Analog Inputs
1
Digital Interface Type
Serial (SPI, QSPI, Microwire)
Input Type
Voltage
Signal To Noise Ratio
68 dB
Polarity Of Input Voltage
Unipolar
Rohs Status
RoHS non-compliant
Number Of Bits
12
Sampling Rate (per Second)
1M
Data Interface
DSP, MICROWIRE™, QSPI™, Serial, SPI™
Number Of Converters
1
Power Dissipation (max)
10.5mW
Voltage Supply Source
Single Supply
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
Lead Free Status / RoHS Status

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AD7475/AD7495
The timer registers are loaded with a value that provides an
interrupt at the required sample interval. When an interrupt is
received, a value is transmitted with TFS/DT (ADC control
word). The TFS is used to control the RFS, and therefore, the
reading of data. The frequency of the serial clock is set in the
SCLKDIV register. When the instruction to transmit with TFS
is given, (that is, AX0 = TX0), the state of the SCLK is checked.
The DSP waits until the SCLK has gone high, low, and high
before transmission starts. If the timer and SCLK values are
chosen such that the instruction to transmit occurs on or near
the rising edge of SCLK, the data can be transmitted or it can
wait until the next clock edge.
For example, the ADSP-2111 has a master clock frequency of
16 MHz. If the SCLKDIV register is loaded with the value 3, an
SCLK of 2 MHz is obtained, and eight master clock periods
elapse for every one SCLK period. If the timer registers are
loaded with the value 803, 100.5 SCLKs occur between
interrupts and subsequently between transmit instructions.
This situation results in nonequidistant sampling because the
transmit instruction is occurring on a SCLK edge. If the
number of SCLKs between interrupts is a whole integer figure
of N, equidistant sampling is implemented by the DSP.
AD7475/AD7495 TO DSP56
The connection diagram in Figure 30 shows how the AD7475/
AD7495 can be connected to the synchronous serial interface
(SSI) of the DSP56xxx family of devices from Motorola. The SSI
is operated in synchronous mode (SYN bit in CRB = 1) with
internally generated 1-bit clock period frame sync for both Tx
and Rx (Bits FSL1 = 1 and FSL0 = 0 in CRB). Set the word
length to 16 by setting Bits WL1 = 1 and WL0 = 0 in CRA. To
implement the power-down modes on the AD7475/AD7495,
the word length can be changed to 8 bits by setting Bit WL1 = 0
and Bit WL0 = 0 in CRA. For signal processing applications, it
is imperative that the frame synchronization signal from the
DSP56xxx provide equidistant sampling. The V
AD7475/AD7495 takes the same supply voltage as that of the
DSP56xxx. This allows the ADC to operate at a voltage higher
than the serial interface, that is, DSP56xxx, if necessary.
AD7475/AD7495*
*
ADDITIONAL PINS OMITTED FOR CLARITY
SDATA
V
SCLK
DRIVE
CS
Figure 30. Interfacing to the DSP56xxx
XXX
SCLK
SRD
SC2
V
DSP56xxx*
DD
DRIVE
pin of the
Rev. B | Page 22 of 24
AD7475/AD7495 TO MC68HC16
The serial peripheral interface (SPI) on the MC68HC16 is
configured for master mode (MSTR) = 1, clock polarity bit
(CPOL) = 1, and the clock phase bit (CPHA) = 0. The SPI is
configured by writing to the SPI control register (SPCR), as
described in the 68HC16 User Manual. The serial transfer takes
place as a 16-bit operation when the size bit in the SPCR
register is set to size = 1. To implement the power-down modes
with an 8-bit transfer, set size = 0. (A connection diagram is
shown in Figure 31.) The V
takes the same supply voltage as that of the MC68HC16. This
allows the ADC to operate at a higher voltage than the serial
interface, that is, the MC68HC16, if necessary.
*
ADDITIONAL PINS OMITTED FOR CLARITY
AD7475/AD7495*
SDATA
V
SCLK
DRIVE
CS
Figure 31. Interfacing to the MC68HC16
DRIVE
pin of the AD7475/AD7495
SCLK/PCM2
MISO/PMC0
SS/PMC3
V
MC68HC16*
DD

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