Datasheet
SLAS353 − DECEMBER 2001
17
www.ti.com
THEORY OF OPERATION
analog and digital supplies
The DAC8541 utilizes two separate supplies for operation. The analog supply (AV
DD
) powers the output buffer
and DAC while the digital supply (DV
DD
) sets the I/O voltage thresholds. Refer to the device specification table
for additional information. AV
DD
can operate from 2.7 V to 5.5 V while DV
DD
can independently function from
1.8 V to 5.5 V. The control and data I/O thresholds are determined by DV
DD
and are given in the electrical
characteristics section.
APPLICATION INFORMATION
host processor interfacing
DAC8541 to MSP430 microcontroller
Figure 32 shows a typical parallel interface connection between the DAC8541 and a MSP430 microcontroller.
The setup for the interface shown uses ports 4 and 5 of the MSP430 to send or receive the 16-bit data while
bits 0−7 of port 2 provides the control signals for the DAC. When data is to be transmitted to the DAC8541, the
data is made available to the DAC via P4 and P5 and P2.1 is taken low. The MSP430 then toggles P2.0 from
high-to-low and back to high, transferring the 16-bit data to the DAC. This data is loaded into the DAC register
by applying a rising edge to P2.4. The remaining five I/O signals of P2 shown in the figure control the reset,
power-down, and data format functions of the DAC. Depending on the specific requirements of a given
application, these pins may be tied to DGND or DV
DD
, enabling the desired mode of operation.
8 Bits
8 Bits
16 Bits
D[15:0]
CS
R/W
RST
RSTSEL
LDAC
PD0
PD1
BTC/USB
V
REF
L
DGND
AV
DD
DV
DD
V
OUT
SENSE
V
OUT
V
REF
H
AGND
(Other Connections Omitted for Clarity)
0.1 µF 1 to 10 µF
0.1 µF 10 µF
0.1 µF 10 µF
AV
DD
DV
DD
V
OUT
V
REF
P4[0:7]
P5[0:7]
P2:0
P2:1
P2:2
P2:3
P2:4
P2:5
P2:6
P2:7
MSP430F149
DAC8541
Figure 32. DAC8541 to MSP430 Microcontroller
DAC8541 to TMS320C5402 DSP
Figure 33 shows the connections between the DAC8541 and the TMS320C5402 digital signal processor. Data
is provided via the parallel data bus of the DSP while the DAC’s CS
control input is derived from the decoded
I/O strobe signal. The IOSTRB
in addition to the R/W and XF(I/O) signals control the data transmission to and
from the DAC as well as the LDAC
control. With additional decoding, multiple DAC8541’s can be connected
to the same parallel data bus of the DSP.