CAT524 Catalyst Semiconductor, CAT524 Datasheet - Page 7

• Manufacturer Part Number: CAT524
• Description: Configured Digitally Programmable Potentiometer (DPP): Programmable Voltage Applications
• Manufacturer: Catalyst Semiconductor

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 CAT524 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
APPLICATION CIRCUITS
MSB
1111
1000
0111
0000
0000
DAC INPUT
1111
0000
1111
0001
0000
LSB
—— (.98 V
—— (.98 V
—— (.98 V
—— (.98 V
—— (.98 V
V
255
V
V
255
128
255
127
255
255
255
1
0
DAC
FS
ZERO
= 0.99 V
= ——— (V
= 0.01 V
CODE
255
REF
REF
REF
REF
REF
DAC OUTPUT
REF
) + .01 V
) + .01 V
) + .01 V
) + .01 V
) + .01 V
REF
FS
- V
REF
REF
REF
REF
REF
ZERO
CONTROL
& DATA
= .990 V
= .502 V
= .498 V
= .014 V
= .010 V
) + V
ZERO
REF
REF
REF
REF
REF
+5V
OPT 504
V
V
V
V
V
V DD
GND
CAT524
V
R = R
ANALOG
OUT
OUT
OUT
OUT
OUT
OUTPUT
REF
I
= +4.90V
= +0.02V
= -0.02V
= -4.86V
= -4.90V
= 5V
F
Amplified DPP Output
V
V
Bipolar DPP Output
REF
REF
H
L
7
CONTROL
& DATA
this feature, the new value must be reloaded into the
DAC control register prior to programming. This is be-
cause the CAT524’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.
Figure 3. Temporary Change in Output
V
OUTPUT
R
OUT
PROG
i
DAC
DO
CS
DI
= (1 + –––) V
t
o
–
+
+15V
-15V
+5V
R F
R I
1
CAT524
1
V DD
GND
2
R
OP 07
A0
F
3
DAC
A1
NON-VOLATILE
4
DAC VALUE
V i
CURRENT
D0
D0
V
V
REF
5
REF
D1
D1
V OUT
6
H
L
CURRENT DAC DATA
NEW DAC DATA
D2
D2
7
D3
D3
8
V
D4
D4
For R =
V
OUT
R
OUT
9
i
D5
D5
10
D6
D6
i R F
=
= 2V
11
V DAC
D7
D7
12
–
+
DAC
Doc. No. 25076-00 Rev. 4/01
+15V
-15V
DAC VALUE
VOLATILE
NEW
(
-V
R + i
OP 07
R
i
R i
F
R F
N
N+1 N+2
CAT524
NON-VOLATILE
) -V R F
DAC VALUE
CURRENT
i
V OUT