MAX5460(2002) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX5460 Datasheet PDF : 10 Pages
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32-Tap FleaPoT™, 2-Wire Digital
Potentiometers
Power-On Reset
All parts in this family feature power-on reset (POR) cir-
cuitry that sets the wiper position to midscale at power-
up. By default, the chip is in the increment mode.
Applications Information
The MAX5460–MAX5468 are intended for circuits
requiring digitally controlled adjustable resistance,
such as LCD contrast control, where voltage biasing
adjusts the display contrast.
Controlling a Switch-Mode
LCD Bias Generator
Figure 3 shows an application where the variable resis-
tor is used with a MAX1771 to make an adjustable posi-
tive LCD-bias circuit. The output of the MAX1771 is a
positive voltage that is digitally controlled through the
MAX5461/MAX5464/MAX5467. Similarly, Figure 4
shows the application of the variable resistor in a digi-
tally controlled negative LCD-bias circuit along with the
MAX774/MAX775/MAX776.
Alternative Positive
LCD Bias Control
Alternatively, use an op amp to provide buffering and
gain to the output of the MAX5462/MAX5465/MAX5468.
Connect the mechanical potentiometer to the positive
input of a noninverting op amp (Figure 5) to select a
portion of the input signal by digitally controlling the
wiper terminal. Figure 6 shows a similar circuit for the
MAX5461/MAX5464/MAX5467.
Adjustable Gain
Figure 7 shows how to use the variable resistor to digi-
tally adjust the gain of a noninverting op amp configura-
tion. Connect the MAX5461/MAX5464/MAX5467 in
series with a resistor to ground to form the adjustable
gain control of a noninverting amplifier. The MAX5460–
MAX5468 have a low 5ppm/°C ratiometric tempco that
allows for a very stable adjustable gain configuration
over temperature.
VIN = 5V
C1
68µF
C3
0.1µF
C2
0.1µF
2
V+
5 REF
4 SHDN MAX1771
6 AGND
GND
7
L1
22µH
D1
1N5817-22
1
EXT
8
CS
FB 3
C4
N
300µF
MTD20N03HDL
RSENSE
40mΩ
R2
MAX5461
MAX5464
MAX5467
C5
RVAR
R1
VOUT = 12V
AT 0.5A
VREF = 1.5V
VOUT(MAX) = R2 + 1
VREF R1
( ) VOUT(MIN) =
R2
+1
VREF
R1 + RVAR(MAX)
Figure 3. Adjustable Positive LCD Bias
VIN
C1
150µF
C2
0.1µF
1 OUT
V+ 5
R2
MAX5461
3
SHDN
2
FB
R3
0.07Ω
CS 6
Q1
7
Si9435
EXT
P
VOUT
MAX5464
MAX774
MAX5467
MAX775
MAX776
RVAR
R1
4 REF
GND
L1
22µH
1N5822/
MBR340
C4*
C3
8
0.1µF
* MAX774 = 330µF, 10V
MAX775/MAX776 = 120µF, 20V
VOUT(MAX) = R2 , VOUT(MIN) = R2
VREF R1 VREF R1 + RVAR
VREF - VFB ≥ 5µA (FOR 2% GAIN-SETTING ACCURACY)
R1 + RVAR
Figure 4. Adjustable Negative LCD Bias
6 _______________________________________________________________________________________
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