ꢉ ꢃꢠ ꢡꢢ ꢣꢤ
www.ti.com
SBAS341B − DECEMBER 2004 − REVISED APRIL 2005
The McBSP provides a host of functions including:
LAYOUT ISSUES AND COMPONENT SELECTION
The ADS1602 is a very high-speed, high-resolution data
converter. In order to achieve maximum performance, the
user must give very careful consideration to both the layout
of the printed circuit board (PCB) in addition to the routing
of the traces. Capacitors that are critical to achieve the
best performance from the device should be placed as
close to the pins of the device as possible. These include
capacitors related the analog inputs, the reference and the
power supplies.
D
D
D
Full-duplex communication
Double-buffered data registers
Independent framing and clocking for reception and
transmission of data
The sequence begins with a one-time synchronization of
the serial port by the microprocessor. The ADS1602
recognizes the SYNC signal if it is high for a least 1 CLK
period. Transfers are initiated by the ADS1602 after the
SYNC signal is de-asserted by the microprocessor.
For critical capacitors, it is recommended that Class II
dielectrics such as Z5U be avoided. These dielectrics
have a narrow operating temperature, a large tolerance on
the capacitance and will lose up to 20% of the rated
capacitance over 10,000 hours. Rather, select capacitors
with a Class I dielectric. C0G (also known as NP0), for
example, has a tight tolerance < 30PPM/°C and is very
stable over time. Should Class II capacitors be chosen
because of the size constraints, select an X7R or X5R
dielectric to minimize the variations of the capacitor’s
critical characteristics.
The FSO signal from the ADS1602 indicates that data is
available to be read, and is connected to the Frame Sync
Receive (FSR) pin of the DSP. The Clock Receiver (CLKR)
is derived directly from the ADS1602 serial clock output to
ensure continued synchronization of data with the clock.
ADS1602
FSO
TMS320
FSR
The resistors used in the circuits driving the input and
reference should be kept as low as possible to prevent
excess thermal noise from degrading the system
performance.
SCLK
DOUT
SYNC
CLKR
DR
The digital outputs from the device should always be
buffered. This will have a number of benefits: it will reduce
the loading of the internal digital buffers, which decreases
noise generated within the device, and it will also reduce
device power consumption.
FSX
Figure 54. ADS1602—TMS320 Interface
Connection
APPLICATIONS INFORMATION
Interfacing the ADS1602 to the TMS320 DSP family.
An Evaluation Module (EVM) is available from Texas
Instruments. The module consists of the ADS1602 and
supporting circuits, allowing users to quickly assess the
performance and characteristics of the ADS1602. The
EVM easily connects to various microcontrollers and DSP
systems. For more details, or to download a copy of the
ADS1602EVM User’s Guide, visit the Texas Instruments
web site at www.ti.com.
Since the ADS1602 communicates with the host via a
serial interface, the most suitable method to connect to any
of the TMS320 DSPs is via the Multi-channel Buffered
Serial Port (McBSP). A typical connection to the TMS320
DSP is shown in Figure 54.
23
BB [ BURR-BROWN CORPORATION ]
