CAT525 CATALYST [Catalyst Semiconductor], CAT525 Datasheet - Page 7

• Manufacturer Part Number: CAT525
• Manufacturer: CATALYST [Catalyst Semiconductor]

CONTROL
& DATA
setting is reloaded into the DAC control register. Since
this value is the same as that which had been there
previously no change in the DAC’s output is noticed.
Had the value held in the control register been different
from that stored in EEPROM then a change would occur
at the read cycle’s conclusion.
TEMPORARILY CHANGE OUTPUT
The CAT525 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 CAT525’s internal control circuitry discards
from the programming register the new data two clock
cycles after receiving it if no PROG signal is received.
APPLICATION CIRCUITS
+5V
V DD
OPT 505
GND
CAT525
V i
V
V
REF
REF
H
L
CONTROL
& DATA
R
For R =
V
V
I
OUT
OUT
I R F
= 2V
=
V DAC
–
+
+15V
-15V
DAC
+5V
OP 07
(
R
-V
CAT525
V DD
OPT 505
GND
R + I
F
I
Amplified DAC Output
Bipolar DAC Output
R I
R F
) -V
V
V
V
REF
REF
I
OUT
R F
H
L
7
RDY/BSY
OUTPUT
V
Figure 3. Temporary Change in Output
PROG
DAC
MSB
1111
1000
0111
0000
0000
OUT
DO
DAC INPUT
CS
DI
R
I
= (1 + –––) V
1111
0000
1111
0001
0000
LSB
t
o
1
R F
R I
–
+
+15V
-15V
1
—— (.98 V
2
—— (.98 V
—— (.98 V
—— (.98 V
—— (.98 V
V
V
V
255
255
128
255
127
255
255
255
A0
DAC
FS
ZERO
1
0
3
R
DAC
OP 07
= 0.99 V
A1
F
NON-VOLATILE
= ——— (V
4
DAC VALUE
CURRENT
D0
= 0.01 V
D0
CODE
255
REF
5
REF
REF
REF
REF
DAC OUTPUT
D1
D1
REF
6
NEW DAC DATA
CURRENT DAC DATA
) + .01 V
) + .01 V
) + .01 V
) + .01 V
) + .01 V
V OUT
D2
D2
REF
7
FS
D3
D3
8
- V
D4
D4
REF
REF
REF
REF
REF
ZERO
9
D5
D5
10
= .990 V
= .502 V
= .498 V
= .014 V
= .010 V
D6
D6
11
) + V
Doc. No. 25078-00 4/01 - A M-1
D7
D7
12
ZERO
REF
REF
REF
REF
REF
DAC VALUE
VOLATILE
NEW
N
V
V
V
V
V
V
R = R
OUT
ANALOG
OUT
OUT
OUT
OUT
OUTPUT
REF
N+1 N+2
I
NON-VOLATILE
CAT525
DAC VALUE
CURRENT
= +4.90V
= +0.02V
= -0.02V
= -4.86V
= -4.90V
= 5V
F