AD5428 Analog Devices, AD5428 Datasheet - Page 22

• Manufacturer Part Number: AD5428
• Description: Dual 8-Bit, High Bandwidth Multiplying DACs with Parallel Interface
• Manufacturer: Analog Devices

Specifications of AD5428

• Resolution (bits): 8bit
• Dac Update Rate: 21.3MSPS
• Dac Settling Time: 30ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

AD5428/AD5440/AD5447
PARALLEL INTERFACE
Data is loaded into the AD5428/AD5440/AD5447 in 8-, 10-, or
12-bit parallel word format. Control lines CS and R/ W allow
data to be written to or read from the DAC register. A write
event takes place when CS and R/ W are brought low, data
available on the data lines fills the shift register, and the rising
edge of CS latches the data and transfers the latched data-word
to the DAC register. The DAC latches are not transparent;
therefore, a write sequence must consist of a falling and rising
edge on CS to ensure that data is loaded into the DAC register
and its analog equivalent is reflected on the DAC output.
A read event takes place when R/ W is held high and CS is
brought low. Data is loaded from the DAC register, goes back
into the input register, and is output onto the data line, where it
can be read back to the controller for verification or diagnostic
purposes. The input and DAC registers of these devices are not
transparent; therefore, a falling and rising edge of CS is required
to load each data-word.
MICROPROCESSOR INTERFACING
ADSP-21xx-to-AD5428/AD5440/AD5447 Interface
Figure 44 shows the AD5428/AD5440/AD5447 interfaced to
the ADSP-21xx series of DSPs as a memory-mapped device. A
single wait state may be necessary to interface the AD5428/
AD5440/AD5447 to the ADSP-21xx, depending on the clock
speed of the DSP. The wait state can be programmed via the
data memory wait state control register of the ADSP-21xx (see
the ADSP-21xx family’s user manual for details).
ADSP-21xx
1
ADDITIONAL PINS OMITTED FOR CLARITY.
DATA 0 TO
ADDR
DATA 23
ADRR
Figure 44. ADSP21xx-to-AD5428/AD5440/AD5447 Interface
0
DMS
1
TO
WR
13
DECODER
ADDRESS
ADDRESS BUS
DATA BUS
R/W
DB0 TO DB11
CS
AD5428/
AD5440/
AD5447
1
Rev. C | Page 22 of 32
8xC51-to-AD5428/AD5440/AD5447 Interface
Figure 45 shows the interface between the AD5428/AD5440/
AD5447 and the 8xC51 family of DSPs. To facilitate external
data memory access, the address latch enable (ALE) mode is
enabled. The low byte of the address is latched with this output
pulse during access to the external memory. AD0 to AD7 are
the multiplexed low order addresses and data bus, and they
require strong internal pull-ups when emitting 1s. During
access to external memory, A8 to A15 are the high order
address bytes. Because these ports are open drain, they also
require strong internal pull-ups when emitting 1s.
ADSP-BF5xx-to-AD5428/AD5440/AD5447 Interface
Figure 46 shows a typical interface between the AD5428/
AD5440/AD5447 and the ADSP-BF5xx family of DSPs. The
asynchronous memory write cycle of the processor drives the
digital inputs of the DAC. The AMS x line is actually four
memory select lines. Internal ADDR lines are decoded into
AMS
rest of the interface is a standard handshaking operation.
8051
ADSP-BF5xx
1
1
ADDITIONAL PINS OMITTED FOR CLARITY.
ADDITIONAL PINS OMITTED FOR CLARITY.
AD0 TO AD7
A8 TO A15
DATA 0 TO
ADDR
1
3–0
DATA 23
ADRR
Figure 46. ADSP-BF5xx-to-AD5428/AD5440/AD5447 Interface
, and then these lines are inserted as chip selects. The
AMSx
1
AWE
Figure 45. 8xC51-to-AD5428/AD5440/AD5447 Interface
ALE
TO
WR
19
1
ADDRESS
DECODER
ADDRESS
DECODER
LATCH
8-BIT
ADDRESS BUS
DATA BUS
ADDRESS BUS
DATA BUS
Data Sheet
CS
R/W
DB0 TO DB11
CS
R/W
DB0 TO DB11
AD5428/
AD5440/
AD5447
AD5428/
AD5440/
AD5447
1
1