
CAT504
7
Doc. No. 25048-0A 2/98 M-1
APPLICATION CIRCUITS
Buffered DAC Output
Amplified DAC Output
TEMPORARILY CHANGE OUTPUT
The CAT504 allows temporary changes in DAC’s output
to be made without disturbing the settings retained in
EEPROM memory. This feature is particularly useful
when testing for a new output setting and allows for user
adjustment of preset or default values without losing the
original factory settings.
Figure 3 shows the control and data signals needed to
effect a temporary output change. DAC settings may be
changed as many times as required and can be made to
any of the four DACs in any order or sequence. The
temporary setting(s) remain in effect long as CS remains
high. When CS returns low all four DACs will return to the
output values stored in EEPROM memory.
When it is desired to save a new setting acquired using
this feature, the new value must be reloaded into the
DAC control register prior to programming. This is be-
cause the CAT504’s internal control circuitry discards
the new data from the programming register two clock
cycles after receiving it (after reception is complete) if no
PROG signal is received.
Bipolar DAC Output
OPT 504
GND
VDD
REF
REF
CONTROL
& DATA
+
–
OP 07
VOUT
-15V
+15V
+5V
OUT DAC
OPT 504
GND
VDD
REF
REF
CONTROL
& DATA
+
–
OP 07
VOUT
-15V
+15V
+5V
R
R
i
F
OUT RI
OPT 504
GND
VDD
REF
REF
CONTROL
& DATA
+
–
OP 07
OUT
RF
R +
-15V
+15V
+5V
R
R
i
F
Ri
i
RF
VDAC
For Ri
OUT
RF
i
DAC
Vi
OUT
MSB LSB
1111 1111 255
1000 0000 128
REF
REF
0111 1111 255
0000 0001 255
0000 0000 0
REF
REF
F
VREF
RI
OUT
DAC INPUT DAC OUTPUT ANALOG
OUTPUT
REF
REF
OUT
REF
REF
OUT
REF
REF
OUT
REF
REF
OUT
VFS
VZERO
REF
REF
DAC
255
CODE
FS
ZERO
ZERO
Figure 3. Temporary Change in Output
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
D0
D1
D2
D3
D4
D5
D6
D7
1
NEW DAC DATA
CURRENT DAC DATA
DO
DI
CS
Vpp
PROG
DAC
OUTPUT
to
CURRENT
NON-VOLATILE
DANEW
VOLATILE
CURRENT
NON-VOLATILE
DON'T CARE