MAX5479 Maxim, MAX5479 Datasheet - Page 12

• Manufacturer Part Number: MAX5479
• Description: Dual - 256-Tap/ Nonvolatile/ I2C-Interface/ Digital Potentiometers
• Manufacturer: Maxim

Dual, 256-Tap, Nonvolatile, I
Digital Potentiometers
The MAX5477/MAX5478/MAX5479 feature a low-power
standby mode. When the device is not being pro-
grammed, it enters into standby mode and supply cur-
rent drops to 500nA (typ).
The MAX5477/MAX5478/MAX5479 are ideal for circuits
requiring digitally controlled adjustable resistance,
such as LCD contrast control (where voltage biasing
adjusts the display contrast), or for programmable fil-
ters with adjustable gain and/or cutoff frequency.
Figures 9 and 10 show an application where the
MAX5477/MAX5478/MAX5479 provide an adjustable,
positive LCD bias voltage. The op amp provides buffer-
Table 2. Command Byte Summary
Figure 9. Positive LCD Bias Control Using a Voltage-Divider
12
NVREGxVREG
VREGxNVREG
NVREGxVREG
VREGxNVREG
NVREGxVREG
VREGxNVREG
SCL CYCLE
NUMBER
NVREG
NVREG
NVREG
VREG
VREG
VREG
______________________________________________________________________________________
MAX5477
MAX5478
MAX5479
START
(S)
Applications Information
A6 A5 A4 A3 A2 A1 A0
1
0
0
0
0
0
0
0
0
0
0
0
0
5V
H_
L_
Positive LCD Bias Control
2
1
1
1
1
1
1
1
1
1
1
1
1
ADDRESS BYTE
W_
3
0
0
0
0
0
0
0
0
0
0
0
0
4
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
1 A2 A1 A0 0
5
MAX480
6
30V
7
8
ACK
(A)
9
Standby
V
OUT
10 11 12 13 14 15 16 17 18
0
0
0
0
0
0
0
0
0
0
0
0
TX NV V R3 R2 R1 R0
0
0
1
1
0
0
1
1
0
0
1
1
COMMAND BYTE
0
1
1
0
0
1
1
0
0
1
1
0
1
0
0
1
1
0
0
1
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
ing and gain to the resistor-divider network made by
the potentiometer (Figure 9) or by a fixed resistor and a
variable resistor (see Figure 10).
Figure 11 shows the MAX5477/MAX5478/MAX5479 in a
1st-order programmable application filter. Adjust the
gain of the filter with R
with R
gain (A) and the -3dB cutoff frequency (f
Figure 10. Positive LCD Bias Control Using a Variable Resistor
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
3
1
1
1
1
0
0
0
0
1
1
1
1
2
. Use the following equations to calculate the
MAX5477
MAX5478
MAX5479
ACK
C-Interface,
(A)
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
19 20 21 22 23 24 25 26
f
C
A
H_
L_
5V
DATA BYTE
=
=
1
2
2
, and set the cutoff frequency
π
W_
+
×
R
R
Programmable Filter
1
2
R
1
3
MAX480
×
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30V
C
ACK
(A)
27
C
):
STOP
(P)
V
OUT
WIPER A
WIPER B
A AND B
WIPERS
NOTES
ONLY
ONLY