Low-Power Digital Potentiometers

Transcription

1 19-143; Rev 2a; 2/1 ow-power Digital Potentiometers General Description The linear-taper digital potentiometers perform the same function as a mechanical potentiometer or a variable resistor. They coist of a fixed resistor and a wiper contact with 32 tap points that are digitally controlled by three lines for the 8-pin MAX16 or by two lines for the 6-pin. These parts are ideal for applicatio requiring digitally controlled resistors. Three resistance values are available for each part type: kω, 1kΩ, and 2kΩ. A nominal resistor temperature coefficient of ppm/ C end-to-end and only ppm/ C ratiometric makes the MAX16 ideal for applicatio requiring a low-temperature-coefficient variable resistor, such as low-tempco, adjustable-gain circuit configuratio. The MAX16 is available in an 8-pin µmax package, and the is available in a 6-pin SOT23 package. Both devices are guaranteed over the extendedindustrial temperature range (-4 C to +8 C). Applicatio CD Screen Adjustment Volume Control Mechanical Potentiometer Replacement PART TOP MARK Selector Guide R (kω) MAX16NEUA 2 MAX16MEUA 1 MAX16EUA NEZT AAAC 2 MEZT AAAB 1 EZT AAAA Pin Configuratio Features 32 Tap Positio kω, 1kΩ, and 2kΩ Resistance Values 4Ω iper Resistance ±2% Resistance Tolerance 3-ire Serial Data Input ±1SB DN ±.SB IN 1nA Supply Current +2.7V to +.V Single-Supply Operation Power-On Reset: iper Goes to Midscale (position 16) ±2kV ESD Protection Small-Footprint Packages 6-Pin SOT23 () 8-Pin µmax (MAX16) Glitchless Switching Between the Resistor Taps Ordering Information PART MAX16NEUA MAX16MEUA TEMP. RANGE -4 C to +8 C -4 C to +8 C PIN- PACKAGE 8 µmax 8 µmax MAX16EUA -4 C to +8 C 8 µmax NEZT -4 C to +8 C 6 SOT23 MEZT -4 C to +8 C 6 SOT23 EZT -4 C to +8 C 6 SOT23 Functional Diagram R (kω) TOP VIE 1 6 MAX MAX UP/DN COUNTER POSITION DECODER µmax 3 4 SOT23-6 Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at , or visit Maxim s website at

2 ow-power Digital Potentiometers ABSOUTE MAXIMUM RATINGS to...-.3v to +6V,, to...-.3v to +6V,, to V to ( +.3V) Input and Output atchup Immunity...±2mA Maximum Continuous Current into,, and MAX16 E...±1mA Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditio beyond those indicated in the operational sectio of the specificatio is not implied. Exposure to absolute maximum rating conditio for extended periods may affect device reliability. EECTRICA CARACTERISTI Continuous Power Dissipation (T A = +7 C) 6-Pin SOT23 (derate 6.2m/ C above +7 C)...m 8-Pin µmax (derate 4.1m/ C above +7 C)...33m Operating Temperature Range C to +8 C Storage Temperature Range...-6 C to +1 C ead Temperature (soldering, 1s)...+3 C ( = +2.7V to +.V, V =, V =, T A = T MIN to T MAX. Typical values are at = +V, T A = +2 C, unless otherwise noted.) µs PARAMETER SYMBO CONDITIONS MIN TYP MAX UNITS DC PERFORMANCE Resolution 3 % Integral Nonlinearity (Note 1) IN ±1/2 SB Differential Nonlinearity (Note 1) DN ±1 SB End-to-End Resistor Tempco TC R ppm/ C Ratiometric Resistor Tempco ppm/ C Full-Scale Error -.1 SB Zero-Scale Error +.1 SB iper Resistance R 4 17 Ω iper Capacitance C 1 pf MAX16_NE End-to-End Resistance MAX16_ME kω MAX16_E DIGITA INPUTS Input igh Voltage VI.7 V Input ow Voltage VI.3 V Input eakage Current ±1 µa Input Capacitance pf TIMING CARACTERISTI (Figure 6) to Setup Time t CI 2 to old Time t IC ow Period t I 2 igh Period t I 2 to old t ID to Setup t DI iper-settling Time t I 1 Frequency f IMAX 7 Mz POER SUPPIES Supply Voltage 2.7. V Supply Current I DD = = = = +V.6 1 µa or = +2.7V 13 na Note 1: For the MAX16, linearity is defined in terms of to code-dependent resistance. 2

3 ow-power Digital Potentiometers ( = +V, T A = +2 C, unless otherwise noted.) IPER RESISTANCE (Ω) 1, IPER RESISTANCE vs. IPER VOTAGE R MAX = = +2.7V = +V IPER VOTAGE (V) MAX16/61 toc1 Typical Operating Characteristics END-TO-END RESISTANCE % CANGE END-TO-END RESISTANCE % CANGE vs. TEMPERATURE 2kΩ 1kΩ kω 2kΩ 1kΩ kω TEMPERATURE ( C) MAX16/61 toc2 RESISTANCE (kω) kΩ END-TO-END RESISTANCE vs. TAP POSITION TAP POSITION MAX16/61 toc3 RESISTANCE (kω) kΩ END-TO-END RESISTANCE vs. TAP POSITION TAP POSITION MAX16/61 toc4 RESISTANCE (kω) kω END-TO-END RESISTANCE vs. TAP POSITION TAP POSITION MAX16/61 toc 3

4 ow-power Digital Potentiometers Typical Operating Characteristics (continued) ( = +V, T A = +2 C, unless otherwise noted.) SUPPY CURRENT (µa) SUPPY CURRENT vs. TEMPERATURE TEMPERATURE ( C) = +V = +2.7V MAX16/61 toc6 OUTPUT mv/div 2V/div V V TAP-TO-TAP SITCING TRANSIENT µs/div MAX16/61 toc7 Pin Description PIN PIN MAX16 NAME FUNCTION iper Increment Control Input. ith low, a high-to-low traition increments ( high) or decrements ( low) the wiper position. Up/Down Control Input. ith low, a high-to-low traition increments ( high) or decrements ( low) the wiper position. 3 2 igh Terminal of Resistor 4 3 Ground iper Terminal of Resistor 6 1 ow Terminal of Resistor 7 Chip-Select Input. Drive low to change the wiper position through and. 8 6 Power Supply 4

5 ow-power Digital Potentiometers Detailed Description The coist of resistor arrays with thirty-one resistive elements. Thirty-two tap points are accessible to the wiper along the resistor string between and. ogic inputs,, and determine the position of the wiper. ith low and high, a high-to-low traition on increments the internal counter, increasing the resistance between and. hen both and are low, a high-to-low traition decrements the internal counter, decreasing the resistance between and. At either end (maximum or minimum positio), additional traitio in the direction of the end points will not change the counter value (the counter will not wrap around). The and terminals of the MAX16 are similar to the two end terminals of a mechanical potentiometer. The tap is equivalent to the variable tap (wiper) of the potentiometer. The is similar to the MAX16 except that internally connects to ground and the wiper terminal () is shorted to the high terminal (). The acts as a variable resistor (a potentiometer with the wiper and one end terminal shorted together). The feature power-on reset circuitry that sets the wiper position to midscale at power-up. Applicatio Information The are intended for circuits requiring digitally controlled adjustable voltage or adjustable gain, such as CD contrast control, where voltage biasing adjusts the display contrast. Controlling a Switch-Mode CD Bias Generator Figure 1 shows an application where the is used with a MAX1771 to make an adjustable positive CD-bias circuit. The output of the MAX1771 is a positive voltage that is digitally controlled through the. Similarly, Figure 2 shows the application of the in a digitally controlled negative CD-bias circuit along with the MAX774/ MAX77/MAX776. V IN = V V IN C1 68µF C3.1µF 4 6 C2.1µF 2 V+ REF MAX1771 SDN A 7 EXT FB µ D1 1N C4 N 3µF MTD2N3D R SENSE 4mΩ R1 R VAR R2 C = 12V AT.A C1 1µF C2.1µF R2 R R VAR 4 C3.1µF OUT V+ SDN FB REF MAX774 MAX77 MAX776 8 EXT µ R3.7Ω Q1 Si943 P 1N822/ MBR34 C4* * MAX774 = 33µF, 1V MAX77, MAX776 = 12µF, 2V V REF = 1.V (MAX) R2 = + 1 V REF R1 (MIN) R2 = V REF ( R1 + R VAR(MAX) ) + 1 (MAX) R2 (MIN) R2 =, = V REF R1 V REF R1 + R VAR V REF - V FB µa (FOR 2% GAIN-SETTING ACCURACY) R1 + R VAR Figure 1. Adjustable Positive CD Bias Figure 2. Adjustable Negative CD Bias

6 ow-power Digital Potentiometers Alternative Positive CD Bias Control Alternatively, use an op amp to provide buffering and gain to the output of the. Connect the MAX16 to the positive input of a noninverting op amp (Figure 3) to select a portion of the input signal by digitally controlling the wiper terminal. Figure 4 shows a similar circuit for the. +V MAX16 +V 3V Adjustable Gain Figure shows how to use the to digitally adjust the gain of a noninverting op amp configuration. Connect the in series with a resistor to ground to form the adjustable gain control of a noninverting amplifier. The have a low ppm/ C ratiometric tempco that allows for a very stable adjustable gain configuration over temperature. Serial Interface Figure 6 is the serial-interface timing diagram. +V +V 3V GAIN 6 GAIN 6 Figure 3. MAX16 Positive CD Bias Control Figure 4. Positive CD Bias Control V CC V CC V IN V IN +V MAX16 a) b) Figure. Adjustable Gain Circuit: a) ; b) MAX16 6

7 ow-power Digital Potentiometers t DI t ID t CI t I t IC t I t I Figure 6. Serial-Interface Timing Diagram Truth Table Chip Information xx-x X R O O O + TRANSISTOR COUNT: 969 X = Don t care O = Previous state + = Increment = Decrement = igh-to-ow Traition = ow-to-igh Traition 7

8 ow-power Digital Potentiometers Package Information 8UMAXD.EPS 8

9 ow-power Digital Potentiometers Package Information (continued) 6 EAD TIN SOT23.EPS Maxim cannot assume respoibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licees are implied. Maxim reserves the right to change the circuitry and specificatio without notice at any time. Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.