AD5445 Analog Devices, AD5445 Datasheet - Page 23

• Manufacturer Part Number: AD5445
• Description: High Bandwidth CMOS 12-Bit Parallel Interface Multiplying D/A Converter
• Manufacturer: Analog Devices

Specifications of AD5445

• Resolution (bits): 12bit
• Dac Update Rate: 20.4MSPS
• Dac Settling Time: 80ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

Data Sheet
Provided the DAC switches are driven from true wideband
low impedance sources (V
Consequently, the slew rate and settling time of a voltage
switching DAC circuit is determined largely by the output op
amp. To obtain minimum settling time in this configuration, it
is important to minimize capacitance at the V
output node in this application) of the DAC. This is done by using
low inputs capacitance buffer amplifiers and careful board design.
Most single-supply circuits include ground as part of the analog
signal range, which in turns requires an amplifier that can handle
rail-to-rail signals. There is a large range of single-supply
amplifiers available from Analog Devices.
PARALLEL INTERFACE
Data is loaded to the
of an 8-, 10-, or 12-bit parallel word. 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, thus
a write sequence must consist of a falling and rising edge on CS
to ensure that data is loaded to 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. New data is loaded from the DAC register back to
the input register and out onto the data line where it can be read
back to the controller for verification or diagnostic purposes.
MICROPROCESSOR INTERFACING
ADSP-21xx-to-AD5424/AD5433/AD5445
Figure 56 shows the
the ADSP-21xx series of DSPs as a memory-mapped device. A
single wait state may be necessary to interface the AD5424/
AD5433/AD5445
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 user’s manual for details).
ADSP-21xx*
*ADDITIONAL PINS OMITTED FOR CLARITY
DATA 0 TO
ADDR
DATA 23
ADRR
Figure 56.
0
DMS
TO
WR
13
ADSP21xx-to-AD5424/AD5433/AD5445
to the ADSP-21xx, depending on the clock
DECODER
ADDRESS
AD5424/AD5433/AD5445
AD5424/AD5433/AD5445
IN
and AGND), they settle quickly.
ADDRESS BUS
DATA BUS
REF
Interface
DB0 TO DB11
CS
R/W
interfaced to
in the format
node (voltage
Interface
AD5424/
AD5433/
AD5445*
Rev. C | Page 23 of 28
8xC51-to-AD5424/AD5433/AD5445
Figure 57 shows the interface between the AD5424/AD5433/
AD5445
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 external memory. AD0 to AD7 are the
multiplexed low order addresses and data bus and require
strong internal pull-ups when emitting 1s. During access to
external memory, A8 to A15 are the high order address bytes.
Since these ports are open drained, they also require strong
internal pull-ups when emitting 1s.
ADSP-BF5xx-to-AD5424/AD5433/AD5445
Figure 58 shows a typical interface between the AD5424/
AD5433/AD5445
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
lines are then inserted as chip selects. The rest of the interface is
a standard handshaking operation.
8051*
ADSP-BF5xx
*ADDITIONAL PINS OMITTED FOR CLARITY
*ADDITIONAL PINS OMITTED FOR CLARITY
AD0 TO AD7
DATA 0 TO
A8 TO A15
ADDR
DATA 23
ADRR
Figure 58.
AMSx
1
AWE
Figure 57.
and the 8xC51 family of DSPs. To facilitate external
ALE
TO
WR
19
ADSP-BF5xx-to-AD5424/AD5433/AD5445
8xC51-to-AD5424/AD5433/AD5445
and the ADSP-BF5xx family of DSPs. The
DECODER
DECODER
ADDRESS
ADDRESS
LATCH
8-BIT
AD5424/AD5433/AD5445
ADDRESS BUS
DATA BUS
ADDRESS BUS
DATA BUS
Interface
R/W
DB0 TO DB11
R/W
DB0 TO DB11
CS
CS
Interface
Interface
Interface
AD5424/
AD5433/
AD5445*
AD5424/
AD5433/
AD5445*
3-0
, these