Datasheet

AD5310 Data Sheet
Rev. B | Page 12 of 16
SYNC
INTERRUPT
In a normal write sequence, the
SYNC
line is kept low for at
least 16 falling edges of SCLK, and the DAC is updated on the
16th falling edge. However, if
SYNC
is brought high before the
16th falling edge, this acts as an interrupt to the write sequence.
The shift register is reset, and the write sequence is seen as
invalid. Neither an update of the DAC register contents or a
change in the operating mode occurs (see
Figure 28).
POWER-ON RESET
The AD5310 contains a power-on reset circuit that controls the
output voltage during power-up. The DAC register is filled with
0s, and the output voltage is 0 V. It remains there until a valid
write sequence is performed to the DAC. This is useful in
applications where it is important to know the state of the
output of the DAC while it is in the process of powering up.
POWER-DOWN MODES
The AD5310 contains four separate modes of operation. These
modes are software programmable by setting two bits (DB13
and DB12) in the control register. Table 5 shows how the state
of the bits corresponds to the mode of operation of the device.
Table 5. Modes of Operation for the AD5310
Operating Mode DB13 DB12
Normal Operation 0 0
Power-Down Modes
1 kΩ to GND
0 1
100 kΩ to GND
1 0
Three-State 1 1
When both bits are set to 0, the part works normally with its
normal power consumption of 140 µA at 5 V. However, for the
three power-down modes, the supply current falls to 200 nA at
5 V (50 nA at 3 V). Not only does the supply current fall, but
the output stage is also internally switched from the output of
the amplifier to a resistor network of known values. This has the
advantage of knowing the output impedance of the part when
the part is in power-down mode. There are three options. The
output is connected internally to GND through a 1 kΩ resistor,
a 100 kΩ resistor, or it is left open-circuited (three-state). The
output stage is illustrated in Figure 26.
Figure 26. Output Stage During Power-Down
The bias generator, the output amplifier, the resistor string, and
other associated linear circuitry are all shut down when the
power-down mode is activated. However, the contents of the
DAC register are unaffected when in power-down. The time to
exit power-down is typically 2.5 µs for V
DD
= 5 V and 5 µs for
V
DD
= 3 V (see Figure 21).
MICROPROCESSOR INTERFACING
AD5310 to ADSP-2101 Interface
Figure 27 shows a serial interface between the AD5310 and the
ADSP-2101. The ADSP-2101 should be set up to operate in the
SPORT transmit alternate framing mode. The ADSP-2101SPORT
is programmed through the SPORT control register and should
be configured as follows: internal clock operation, active low
framing, 16-bit word length. Transmission is initiated by writing
a word to the Tx register after the SPORT has been enabled.
Figure 27. AD5310 to ADSP-2101 Interface
Figure 28.
SYNC
Interrupt Facility
ADSP-2101* AD5310*
*ADDITIONAL PINS OMITTED FOR CLARITY
TFS
DT
SCLK
SYNC
DIN
SCLK