Datasheet MAX5160 (Maxim) - 5

Low-Power Digital Potentiometers MAX5160/MAX5161 Detailed Description
a variable resistor (a potentiometer with the wiper and one end terminal shorted together). The MAX5160/MAX5161 consist of resistor arrays with thirty-one resistive elements. Thirty-two tap points are The MAX5160/MAX5161 feature power-on reset circuit- accessible to the wiper along the resistor string ry that sets the wiper position to midscale at power-up. between H and L. Logic inputs CS, U/D, and INC
Applications Information
determine the position of the wiper. With CS low and U/D high, a high-to-low transition on INC increments the The MAX5160/MAX5161 are intended for circuits internal counter, increasing the resistance between W requiring digitally controlled adjustable voltage or and L. When both CS and U/D are low, a high-to-low adjustable gain, such as LCD contrast control, where INC transition decrements the internal counter, decreas- voltage biasing adjusts the display contrast. ing the resistance between W and L. At either end
Controlling a Switch-Mode
(maximum or minimum positions), additional transitions in
LCD Bias Generator
the direction of the end points will not change the counter Figure 1 shows an application where the MAX5161 is value (the counter will not wrap around). used with a MAX1771 to make an adjustable positive The H and L terminals of the MAX5160 are similar to the LCD-bias circuit. The output of the MAX1771 is a posi- two end terminals of a mechanical potentiometer. The tive voltage that is digitally controlled through the tap W is equivalent to the variable tap (wiper) of the MAX5160/MAX5161. Similarly, Figure 2 shows the potentiometer. application of the MAX5161 in a digitally controlled The MAX5161 is similar to the MAX5160 except that CS negative LCD-bias circuit along with the MAX774/ internally connects to ground and the wiper terminal (W) MAX775/MAX776. is shorted to the high terminal (H). The MAX5161 acts as VIN = 5V VIN C1 C2 C1 C2 68µF 0.1µF 1 5 150µF 0.1µF OUT V+ 2 L1 R3 V+ 22µH R2 3 0.07Ω 5 D1 VOUT = 12V SHDN MAX774 REF 1N5817-22 AT 0.5A MAX775 CS 6 C3 2 Q1 MAX5161 0.1µF MAX776 Si9435 MAX1771 C4 7 4 1 FB EXT P SHDN EXT 300µF N R V VAR OUT MTD20N03HDL 6 8 1N5822/ AGND CS MBR340 RSENSE R1 4 REF L1 C4* 40mΩ R2 22µH 3 GND FB C3 8 GND 0.1µF 7 C5 RVAR MAX5161 * MAX774 = 330µF, 10V MAX775, MAX776 = 120µF, 20V R1 V V R2 V R2 REF = 1.5V OUT(MAX) = , OUT(MIN) = V VREF R1 VREF R1 + RVAR OUT(MAX) R2 = + 1 V V REF R1 REF - VFB ≥ 5µA (FOR 2% GAIN-SETTING ACCURACY) R1 + RVAR VOUT(MIN) = ( R2 ) + 1 VREF R1 + RVAR(MAX) Figure 1. Adjustable Positive LCD Bias Figure 2. Adjustable Negative LCD Bias
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