Rainbow Electronics MAX5479 - Manual (Page 13)

MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I
2
C-Interface,
Digital Potentiometers
______________________________________________________________________________________ 13
Offset Voltage and Gain Adjustment
Connect the high and low terminals of one potentiome-
ter of a MAX5477 between the NULL inputs of a
MAX410 and the wiper to the op amp’s positive supply
to nullify the offset voltage over the operating tempera-
ture range. Install the other potentiometer in the feed-
back path to adjust the gain of the MAX410 (Figure 12).
Adjustable Voltage Reference
Figure 13 shows the MAX5477/MAX5478/MAX5479
used as the feedback resistors in multiple adjustable
voltage reference applications. Independently adjust
the output voltages of the MAX6160 parts from 1.23V to
V
IN
- 0.2V by changing the wiper positions of the
MAX5477/MAX5478/MAX5479.
MAX6160
IN
5V
OUT
ADJ
GND
HA
LA
WA
VOUT1
IN
OUT
ADJ
GND
HB
LB
WB
V OUT2
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
MAX6160
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
FOR THE MAX5477 V OUT_ = 1.23V x
10k Ω
R
FOR THE MAX5478 V OUT_ = 1.23V x
50k Ω
R
FOR THE MAX5479 V OUT_ = 1.23V x
100k Ω
R
WHERE R = R HL x D / 256
AND D = DECIMAL VALUE OF WIPER CODE
R R
Figure 13. Adjustable Voltage Reference
3
2
5V
7
4
1
6
8
MAX410
HA LA
WA
R2
R1
HB
LB
WB
1/2 MAX5477
1/2 MAX5477
R 2 = R HL x D / 256
WHERE R HL = END-TO-END RESISTANCE
AND = D DECIMAL VALUE OF WIPER CODE
Figure 12. Offset Voltage Adjustment Circuit
MAX5477
MAX5478
MAX5479
V IN
R 2
HB
WB
LB
R 1
V OUT
R 3
HA
WA
LA
C
MAX410
V+
V-
R 2 , R 3 = R HL x D / 256
WHERE R HL = END-TO-END RESISTANCE
AND D = DECIMAL VALUE OF WIPER CODE
Figure 11. Programmable Filter
16
1
2
3
4
12
11
10
9
15 14 13
5 6 7 8
N.C. HA WA LA
HB
WB
LB
WP
SCL
SDA
A0
A1 A2 GND N.C.
V DD
TOP VIEW
MAX5477
MAX5478
MAX5479
14
13
12
11
10
9
8
1
2
3
4
5
6
7
V DD
SCL
SDA
A0 HB
LA
WA
HA
A1
A2
GND WP
LB
WB
TSSOP
(4.4mm x 5mm)
THIN QFN
(3mm x 3mm)
MAX5477
MAX5478
MAX5479
Pin Configurations
Chip Information
TRANSISTOR COUNT: 12,651
PROCESS: BiCMOS