AD5310
–10– REV. A
AD5310 to 68HC11/68L11 Interface
Figure 26 shows a serial interface between the AD5310 and the
68HC11/68L11 microcontroller. SCK of the 68HC11/68L11
drives the SCLK of the AD5310, while the MOSI output
drives the serial data line of the DAC. The SYNC signal is de-
rived from a port line (PC7). The setup conditions for correct
operation of this interface are as follows: the 68HC11/68L11
should be configured so that its CPOL bit is a 0 and its CPHA
bit is a 1. When data is being transmitted to the DAC, the
SYNC line is taken low (PC7). When the 68HC11/68L11 is
configured as above, data appearing on the MOSI output is valid
on the falling edge of SCK. Serial data from the 68HC11/68L11
is transmitted in 8-bit bytes with only eight falling clock edges
occurring in the transmit cycle. Data is transmitted MSB first. In
order to load data to the AD5310, PC7 is left low after the first
eight bits are transferred, and a second serial write operation is
performed to the DAC and PC7 is taken high at the end of this
procedure.
SCLK
68HC11/68L11*
SCK
*ADDITIONAL PINS OMITTED FOR CLARITY
DIN
MOSI
AD5310*
PC7
Figure 26. AD5310 to 68HC11/68L11 Interface
AD5310 to 80C51/80L51 Interface
Figure 27 shows a serial interface between the AD5310 and the
80C51/80L51 microcontroller. The setup for the interface is as
follows: TXD of the 80C51/80L51 drives SCLK of the AD5310,
while RXD drives the serial data line of the part. The SYNC
signal is again derived from a bit programmable pin on the port.
In this case port line P3.3 is used. When data is to be transmit-
ted to the AD5310, P3.3 is taken low. The 80C51/80L51 trans-
mits data only in 8-bit bytes; thus only eight falling clock edges
occur in the transmit cycle. To load data to the DAC, P3.3 is
left low after the first eight bits are transmitted, and a second
write cycle is initiated to transmit the second byte of data. P3.3
is taken high following the completion of this cycle. The 80C51/
80L51 outputs the serial data in a format which has the LSB
first. The AD5310 requires its data with the MSB as the first bit
received. The 80C51/80L51 transmit routine should take this
into account.
SCLK
80C51/80L51*
TXD
*ADDITIONAL PINS OMITTED FOR CLARITY
DIN
RXD
AD5310*
P3.3
Figure 27. AD5310 to 80C51/80L51 Interface
AD5310 to Microwire Interface
Figure 28 shows an interface between the AD5310 and any
microwire compatible device. Serial data is shifted out on the
falling edge of the serial clock and is clocked into the AD5310
on the rising edge of the SK.
SCLK
MICROWIRE*
SK
*ADDITIONAL PINS OMITTED FOR CLARITY
DIN
SO
AD5310*
CS
Figure 28.␣ AD5310 to MICROWIRE Interface
APPLICATIONS
Using REF19x as a Power Supply for AD5310
Because the supply current required by the AD5310 is extremely
low, an alternative option is to use a REF19x voltage reference
(REF195 for 5 V or REF193 for 3 V) to supply the required
voltage to the part—see Figure 29. This is especially useful if
your power supply is quite noisy or if the system supply voltages
are at some value other than 5 V or 3 V (e.g., 15 V). The REF19x
will output a steady supply voltage for the AD5310. If the low
dropout REF195 is used, the current which it needs to supply to
the AD5310 is 140 µA. This is with no load on the output of the
DAC. When the DAC output is loaded, the REF195 also needs to
supply the current to the load. The total current required (with
a 5 kΩ load on the DAC output) is:
140
µ
A + (5 V/5 k
Ω
) = 1.14 mA
The load regulation of the REF195 is typically 2 ppm/mA
which results in an error of 2.3 ppm (11.5 µV) for the 1.14 mA
current drawn from it. This corresponds to a 0.002 LSB error.
THREE-WIRE
SERIAL
INTERFACE
+15V
+5V
140mA
V
OUT
= 0V TO 5V
AD5310
REF195
SYNC
SCLK
DIN
Figure 29. REF195 as Power Supply to AD5310
