CAT524_04 Datasheet, PDF (7/13 Pages) Catalyst Semiconductor – Configured Digitally Programmable Potentiometer

CAT524
Since this value is the 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 CAT524 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 wiper 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 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
to 1 2 3 4 5 6 7 8 9 10 11 12
N N+1 N+2
CS
DI
DO
PROG
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
DPP INPUT
DPP OUTPUT
MSB LSB
1111 1111
VDPP = —^C2O—_5D5—^E (VFS- VZERO ) + V _ZERO
VFS = 0.99 VREF
VZERO = 0.01 VREF
—₂₂₅₅—₅₅ (.98 VREF) + .01 VREF = .990 VREF
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
ANALOG
OUTPUT
VREF = 5V
R _I = RF
VOUT= +4.90V
V _OUT= +0.02V
V _OUT= -0.02V
V _OUT= -4.86V
CONTROL
& DATA
0000 0000 —₂₀₅—₅ (.98 VREF) + .01 VREF = .010 VREF V _OUT= -4.90V
+5V
Vi
VDD
VREFH
CAT524
GND
VREFL
Ri
RF
+15V
–
+ _{OP 07}
-15V
VOUT
VOUT = ^VDPP
(Ri+ RF ) -ViRF
Ri
For Ri = RF
VOUT = 2VDPP -Vi
CONTROL
& DATA
Bipolar DPP Output
+5V
Ri
RF
VDD
VREFH
C_OA_PT5₅2₀4₄
GND
VREFL
+15V
–
+ _{OP 07}
-15V
VOUT = (1 + –RR–FI–) V _DPP
VOUT
Amplified DPP Output
7
Doc. No. 2006, Rev. E