AD664TD-UNI Analog Devices Inc, AD664TD-UNI Datasheet - Page 9

IC DAC 12BIT QUAD UNIPOL 28-CDIP

AD664TD-UNI

Manufacturer Part Number
AD664TD-UNI
Description
IC DAC 12BIT QUAD UNIPOL 28-CDIP
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD664TD-UNI

Rohs Status
RoHS non-compliant
Settling Time
8µs
Number Of Bits
12
Data Interface
Parallel
Number Of Converters
4
Voltage Supply Source
Dual ±
Power Dissipation (max)
525mW
Operating Temperature
-55°C ~ 125°C
Mounting Type
Through Hole
Package / Case
28-CDIP (0.600", 15.24mm)

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REV. C
This allows the user to “preload” the data to a DAC and strobe
it into the output latch at some future time. The user could do
this by reproducing the sequence of signals illustrated in the
next section.
Update Second Rank of a DAC
Assuming that a new input code had previously been placed into
the first rank of the input latches, the user can update the out-
put of the DAC by simply pulling CS low while keeping LS,
MS, TR, RD and RST high. Address data is not needed in this
case. In reality, all second ranks are being updated by this pro-
cedure, but only those which receive data different from that
already there would manifest a change. Updating the second
rank does not change the contents of the first rank.
The same options that exist for individual DAC input loading
also exist for multiple DAC input loading. That is, the user can
choose to update the first and second ranks of the registers or
preload the first ranks and then update them at a future time.
Preload Multiple First Rank Registers
The first ranks of the DAC input registers may be preloaded
with new input data without disturbing the second rank data.
This is done by transferring the data into the first rank by bring-
ing CS low while LS is low. But CS must return high before LS.
This prevents the data from the first rank from getting into the
second rank. A simple second rank update cycle as shown in
Figure 11 would move the “preloaded” information to the
DACs.
Figure 10b. Preload First Rank of a DAC Timing
Figure 11. Update Second Rank of a DAC
Figure 10a. Preload First Rank of a DAC
SYMBOL
t
t
t
t
t
t
t
LS
LH
CW
DS
DH
AS
AH
25 C
MIN (ns)
0
15
80
0
15
0
15
T
MIN (ns)
0
15
100
0
15
0
15
MIN
to T
MAX
–9–
Load and Update Multiple DAC Outputs
The following examples demonstrate two ways to update all
DAC outputs. The first method involves doing all data transfers
during one long CS low period. Note that in this case, shown in
Figure 13, LS returns high before CS goes high. Data hold time,
relative to an address change, is 70 ns. This updates the outputs
of all DACs simultaneously.
The second method involves doing a CS assertion (low) and an
LS toggle separately for each DAC. It is basically a series of
preload operations (Figure 10). In this case, illustrated in Figure
14, two LS signals are shown. One, labeled LS, goes high before
CS returns high. This transfers the “new” input word to the
DAC outputs sequentially. The second LS signal, labeled Alter-
nate LS, stays low until CS returns high. Using this sequence
loads the first ranks with each “new” input word but doesn’t up-
date the DAC outputs. To then update all DAC outputs simul-
taneously would require the signals illustrated in Figure 11.
SELECTING GAIN RANGE AND MODES (44-PIN
VERSIONS)
The AD664’s mode select feature allows a user to configure the
gain ranges and output modes of each of the four DACs.
On-board switches take the place of up to eight external relays
that would normally be required to accomplish this task. The
switches are programmed by the mode select word entered via
the data I/O port. The mode select word is eight-bits wide and
Figure 14. Load and Update Multiple DACs
Figure 12. Preload First Rank Registers
Figure 13. Update All DAC Outputs
AD664

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