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CAT525_07 Datasheet, PDF (9/16 Pages) Catalyst Semiconductor – Configured Digitally Programmable Potentiometer (DPP™): Programmable Voltage Applications
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CAT525
APPLICATION CIRCUITS
+5V
VI
RI
RF
CONTROL
& DATA
VDD
VREFH
CAT525
VDPP
+15V
–
+
OP 07
VOUT
GND
VREFL
-15V
V OUT
=
VDPP
( RI+ RF )
RI
-
VI RF
For R I = RF
VOUT = 2VDPP - VI
DPP INPUT
MSB LSB
1111 1111
1000 0000
0111 1111
0000 0001
0000 0000
DPP OUTPUT
VDPP
=
CODE
255
VFS
-
VZERO
+ VZERO
VFS = 0.99VREF
VZERO = 0.01VREF
255
255
×
0.98VREF
+
0.01VREF
=
0.990VREF
128
255
×
0.98VREF
+
0.01VREF
=
0.502VREF
127
255
×
0.98VREF
+
0.01VREF
=
0.498VREF
1
255
×
0.98VREF
+
0.01VREF
=
0.014VREF
0
255
×
0.98VREF
+
0.01VREF
=
0.010VREF
ANALOG OUTPUT
VREF = 5V
RI = RF
VOUT = +4.90V
VOUT = +0.02V
VOUT = -0.02V
VOUT = -4.86V
VOUT = -4.90V
Bipolar DPP Output
CONTROL
& DATA
+5V
RI
RF
VDD
VREFH
CAT525
VDPP
+15V
–
+
OP 07
VOUT
GND
VREFL
-15V
VOUT = (1 + RRFI ) VDPP
Amplified DPP Output
+5V
VDD
VREF
VREFH
FINE ADJUST
DPP
127RC
COARSE ADJUST
DPP
GND
VREFL
+V
RC
+
VOFFSET
–
RC
=
VREF
256 x 1µA
Fine adjust gives ±1 LSB change in VOFFSET
when VOFFSET = VREF/2
Coarse-Fine Offset Control by Averaging DPP
Outputs for Single Power Supply Systems
+5V
VDD
+VREF
VREFH
FINE ADJUST
DPP
127RC
COARSE ADJUST
RC
DPP
RC =
(+VREF) - (VOFFSET+)
1µA
(-VREF) + (VOFFSET+)
R0 =
1µA
GND
VREFL
R0
-VREF
+V
+
VOFFSET
–
-V
Coarse-Fine Offset Control by Averaging DPP
Outputs for Dual Power Supply Systems
© Catalyst Semiconductor, Inc.
9
Characteristics subject to change without notice
Doc. No. MD-2001 Rev. F
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