CAT525_04 Datasheet, PDF (7/12 Pages) Catalyst Semiconductor – Configured Digitally Programmable Potentiometer

CAT525
same as that which had been there previously no change
in the DPP’s output is noticed. Had the value held in the
control register been different from that stored in non-
volatile memory then a change would occur at the read
cycle’s conclusion.
TEMPORARILY CHANGE OUTPUT
The CAT525 allows temporary changes in DPP’s output
to be made without disturbing the settings retained in
non-volatile 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. DPP settings may be
changed as many times as required and can be made to
any of the four DPPs in any order or sequence. The
temporary setting(s) remain in effect long as CS remains
high. When CS returns low all four DPPs will return to the
output values stored in non-volatile memory.
When it is desired to save a new setting acquired using
this feature, the new value must be reloaded into the
DPP control register prior to programming. This is
because 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.
Figure 3. Temporary Change in Output
to 1 2 3 4 5 6 7 8 9 10 11 12
N N+1 N+2
CS
DI
DO
PROG
RDY/BSY
DPP
OUTPUT
NEW DPP DATA
1 A0 A1 D0 D1 D2 D3 D4 D5 D6 D7
CURRENT DPP DATA
D0 D1 D2 D3 D4 D5 D6 D7
CURRENT
DPP VALUE
NON-VOLATILE
NEW
DPP VALUE
VOLATILE
CURRENT
DPP VALUE
NON-VOLATILE
APPLICATION CIRCUITS
+5V
Vi
RI
RF
CONTROL
& DATA
VDD
VREFH
CAT525
VDPP
GND
VREFL
+15V
–
+ _{OP 07}
-15V
V _OUT
VOUT = VDPP (RI+ RF) -VI RF
RI
For RI = RF
VOUT = 2VDPP -VI
DPP INPUT
DPP OUTPUT
MSB LSB
1111 1111
VDPP = —^C2O—_5D5—^E (VFS- VZERO ) + VZERO
VFS = 0.99 VREF
VZERO = 0.01 VREF
—₂₂₅₅—₅₅ (.98 VREF ) + .01 VREF = .990 VREF
ANALOG
OUTPUT
VREF = 5V
R _I = RF
VOUT = +4.90V
1000 0000
0111 1111
0000 0001
—¹²²⁵—⁸⁵ (.98 VREF) + .01 VREF = .502 VREF
—¹²²⁵—⁷⁵ (.98 VREF) + .01 VREF = .498 VREF
—₂₁₅—₅ (.98 VREF) + .01 VREF = .014 VREF
VOUT = +0.02V
VOUT = -0.02V
VOUT = -4.86V
0000 0000 —₂₀₅—₅ (.98 VREF) + .01 VREF = .010 VREF
VOUT = -4.90V
Bipolar DPP Output
+5V
RI
RF
CONTROL
& DATA
VDD
VREFH
+15V
–
CAT525
+ _{OP 07}
GND
VREFL
-15V
VOUT
=
(1
+
–^R–^F–)
RI
VDPP
A_Ampli_lf_ified_dD_DA_PC_PO_Output
V _OUT
7
Doc. No. 2001, Rev. E