32-Tap, Nonvolatile, Linear-Taper Digital Potentiometers in SOT23

Transcription

1 19-367; Rev 1; 2/6 EVALUATION KIT AVAILABLE 32-Tap, Nonvolatile, Linear-Taper Digital General Description The lineartaper digital potentiometers function as mechanical potentiometers, but replace the mechanics with a simple 3-wire up/down digital interface. These digital potentiometers feature nonvolatile memory (EEPROM) to return the wiper to its previously stored position upon power-up. The MAX5471/ are 2-terminal, variable resistors in 6-pin SOT23 packages. The MAX5474/ are 3-terminal potentiometers in 8-pin SOT23 packages. The MAX5471/MAX5474 have an end-to-end resistance of 5kΩ, and the / have an endto-end resistance of 1kΩ. All of these devices have 32 wiper positions, a low ratiometric temperature coefficient (5ppm/ C), and all operate from a single +2.7V to +5.25V supply. Each device is guaranteed over the extended -4 C to +85 C temperature range. Applications Mechanical Potentiometer Replacement Liquid-Crystal-Display (LCD) Screen Adjustment Audio Volume Control Programmable Filters TOP VIEW CS V DD Pin Configurations CS 1 V DD L W Features Wiper Position Stored in Nonvolatile Memory and Recalled Upon Power-Up Tiny SOT23 Package 35ppm/ C End-to-End Resistance Temperature Coefficient 5ppm/ C Ratiometric Temperature Coefficient 32 Tap Positions Voltage-Divider or Variable-Resistor Potentiometer Configuration 5kΩ and 1kΩ End-to-End Resistance Values 1µA (max) Static Supply Current 2.7V to 5.25V Single-Supply Operation 2, Wiper Store Cycles 5-Year Wiper Data Retention PART Ordering Information TEMP RANGE PIN-PACKAGE PKG CODE M A X E Z T- T - 4 C to + 85 C 6 Thin SOT23-6 Z6-1 M A X E Z T- T - 4 C to + 85 C 6 Thin SOT23-6 Z6-1 M A X E KA- T - 4 C to + 85 C 8 SOT23-8 K8S-3 M A X E KA- T - 4 C to + 85 C 8 SOT23-8 K8S-3 PART END-TO-END RESISTANCE (kω) Selector Guide TOP MARK MAX5471EZT 5 ABQN EZT 1 ABQM MAX5474EKA 5 AEIZ EKA 1 AEIY U/D 3 MAX5471 SOT INC U/D 3 4 MAX INC SOT23-8 Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS V DD to...-.3v to +6.V All Other Pins to...-.3v to the lower of (V DD +.3V) or +6.V Maximum Continuous Current into, L, and W MAX5471/MAX ±1.3mA /...±.6mA 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 conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CARACTERISTICS Continuous Power Dissipation (T A = +7 C) 6-Pin SOT23 (derate 9.1mW/ C above +7 C)...727mW 8-Pin SOT23 (derate 8.9mW/ C above +7 C)...714mW Operating Temperature Range...-4 C to +85 C Junction Temperature C Storage Temperature Range...-6 C to +15 C Lead Temperature (soldering, 1s)...+3 C (V DD = +2.7V to +5.25V, V = V DD, V L =, T A = -4 C to +85 C, unless otherwise noted. Typical values are at V DD = +5.V, T A = +25 C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC PERFORMANCE Resolution N 32 Tap End-to-End Resistance End-to-End Resistance Temperature Coefficient Ratiometric Resistance Temperature Coefficient MAX5471/MAX / TC R 35 ppm/ C kω 5 ppm/ C Variable-resistor mode (Note 2) ±.5 ±1. Integral Nonlinearity INL Voltage-divider mode (MAX5474/) (Note 3) ±.1 ±.5 Variable-resistor mode (Note 2) ±.5 ±1. Differential Nonlinearity DNL Voltage-divider mode (MAX5474/) (Note 3) ±.1 ±.5 Full-Scale Error MAX5474/ -.5 LSB Zero-Scale Error MAX5474/ +.5 LSB Wiper Resistance R W MAX5474/ (Note 4) 6 12 Ω DIGITAL INPUTS (CS, U/D, INC) (Note 5) V DD < 3.6V.7 x V DD Input igh Voltage V I V DD 3.6V 2.4 LSB LSB V V DD < 3.6V.3 x V DD Input Low Voltage V IL V DD 3.6V.8 V Input Current I IN ±.1 ±1 µa DYNAMIC CARACTERISTICS Wiper -3dB Bandwidth (Note 6) MAX5471/MAX / 2 kz 2

3 ELECTRICAL CARACTERISTICS (continued) (V DD = +2.7V to +5.25V, V = V DD, V L =, T A = -4 C to +85 C, unless otherwise noted. Typical values are at V DD = +5.V, T A = +25 C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS TIMING CARACTERISTICS (Figure 1, Note 7) CS to INC Setup t CI 5 ns INC igh to U/D Change t ID ns U/D to INC Setup t DI 1 ns INC Low Period t IL 5 ns INC igh Period t I 5 ns INC Cycle Time t CYC 1 ns INC Inactive to CS Inactive t IC 1 ns INC Active to CS Inactive t IK 1 ns CS Deselect Time (Store) t CP 1 ns Wiper Settling Time t IW (Note 8) 1 µs Power-Up to Wiper Stable t PU 1 µs Wiper Store Cycle t WSC 12 ms NONVOLATILE MEMORY RELIABILITY Data Retention T A = +85 C 5 Year Endurance POWER SUPPLY T A = +25 C 2, T A = +85 C 5, Supply Voltage V DD V Supply Current I DD Write to memory 4 µa Static Supply Current I SD T A = +25 C (Note 9).35 1 µa Note 1: All devices are production tested at T A = +25 C and are guaranteed by design and characterization for -4 C < T A < +85 C. Note 2: The DNL and INL are measured with the potentiometer configured as a variable resistor. For the 3-terminal potentiometers (MAX5474/), is unconnected and L =. At V DD = 5.25V, W is driven with a source current of 8µA for the 5kΩ configuration, and 4µA for the 1kΩ configuration. At V DD = 2.7V, the wiper terminal is driven with a source current of 4µA for the 5kΩ configuration, and 2µA for the 1kΩ configuration. Note 3: The DNL and INL are measured with the potentiometer configured as a voltage-divider with = V DD and L = (MAX5474/ only). The wiper terminal is unloaded. Note 4: The wiper resistance is the worst value measured by injecting the currents given in Note 2 into W with L =. R W = (V W - V ) / I W. Note 5: The device draws higher supply current when digital inputs are driven with voltages between.3v x V DD and.7 x V DD. Drive the digital inputs as close as possible to V DD or. (See the Typical Operating Characteristics for the Supply Current vs. Digital Input Voltage graph.) Note 6: Wiper at midscale with a 1pF load. Note 7: Digital timing is guaranteed by design and characterization, and is not production tested. Note 8: Wiper settling time is the worst-case % to 5% rise time measured between consecutive wiper positions. = V DD, L =, and the wiper terminal is unloaded and measured with a 1pF oscilloscope probe (see the Typical Operating Characteristics for the Tap-to-Tap Switching Transient). Note 9: Digital inputs CS, U/D, and INC are connected to or V DD. See the Typical Operating Characteristics for the Static Supply Current vs. Temperature graph. Store 3

4 (V DD = 5.V, T A = +25 C, unless otherwise noted.) SUPPLY CURRENT (μa) WIPER RESISTANCE (Ω) W-TO-L RESISTANCE (kω) SUPPLY CURRENT vs. SUPPLY VOLTAGE.5 DIGITAL INPUTS = OR V DD SUPPLY VOLTAGE (V) WIPER RESISTANCE vs. (MAX5474) V DD = 5.V V DD = 3.V W-TO-L RESISTANCE vs. MAX MAX5471 toc1 MAX5471 toc4 MAX5471 toc7 SUPPLY CURRENT (μa) WIPER RESISTANCE (Ω) -TO- RESISTANCE (kω) STATIC SUPPLY CURRENT vs. TEMPERATURE DIGITAL INPUTS = OR V DD V DD = 5.V V DD = 3.V TEMPERATURE ( C) WIPER RESISTANCE vs. () V DD = 5.V Typical Operating Characteristics V DD = 3.V -TO- RESISTANCE vs. MAX MAX5471 toc2 MAX5471 toc5 MAX5471 toc8 SUPPLY CURRENT (μa) END-TO-END RESISTANCE % CANGE 1, SUPPLY CURRENT vs. DIGITAL INPUT VOLTAGE V DD = 5.V V DD = 3.V DIGITAL INPUT VOLTAGE (V) END-TO-END RESISTANCE % CANGE vs. TEMPERATURE 1kΩ 5kΩ 5kΩ 1kΩ TEMPERATURE ( C) INC 5V/div W 1mV/div TAP-TO-TAP SWITCING TRANSIENT C L = 1pF V = V DD TAP 16 TO TAP 15 4ns/div MAX5474 MAX5471 toc3 MAX5471 toc6 MAX5471 toc9 4

5 Typical Operating Characteristics (continued) (V DD = 5.V, T A = +25 C, unless otherwise noted.) RESISTANCE DNL RESISTANCE INL V DD 5V/div W 1V/div RESISTANCE DNL vs. (MAX5471) VARIABLE-RESISTOR MODE WIPER TRANSIENT AT POWER-ON (MAX5474) 1.μs/div RESISTANCE INL vs. () VARIABLE-RESISTOR MODE C L = 1pF TAP 16 V = V DD MAX5471 toc1 MAX5471 toc13 MAX5471 toc16 RESISTANCE INL RESISTANCE DNL V DD 5V/div W 1V/div WIPER TRANSIENT AT POWER-ON () 1.μs/div C L = 1pF TAP 16 V = V DD RESISTANCE INL vs. (MAX5471) VARIABLE-RESISTOR MODE RESISTANCE DNL vs. (MAX5474) VOLTAGE-DIVIDER MODE MAX5471 toc11 MAX5471 toc14 MAX5471 toc17 WIPER RESPONSE (db) RESISTANCE DNL RESISTANCE INL WIPER RESPONSE vs. FREQUENCY TAP = 16 C L = 1pF MAX FREQUENCY (kz) RESISTANCE DNL vs. () VARIABLE-RESISTOR MODE RESISTANCE INL vs. (MAX5474) VOLTAGE-DIVIDER MODE MAX5471toc12 MAX5471 toc15 MAX5471 toc

6 Typical Operating Characteristics (continued) (V DD = 5.V, T A = +25 C, unless otherwise noted.) MAX5471/ RESISTANCE DNL PIN RESISTANCE DNL vs. () VOLTAGE-DIVIDER MODE MAX5474/ NAME 1 1 CS 2 3 Ground 3 4 U/D 4 5 INC MAX5471 toc19 RESISTANCE INL RESISTANCE INL vs. () VOLTAGE-DIVIDER MODE FUNCTION MAX5471 toc2 Pin Description Chip-Select Input. Drive low to change wiper position (W) through INC and U/D. A low-tohigh transition with INC high stores the wiper position in nonvolatile memory. Up/Down Control Input. With U/D low, a high-to-low INC transition decrements the wiper position. With U/D high, a high-to-low INC transition increments the wiper position. Wiper Increment Control Input. With CS low, the wiper position moves in the direction determined by the state of U/D on a high-to-low transition. 5 6 igh Terminal of Resistor. The voltage at can be greater than or less than the voltage at L. Current can flow into or out of. 6 2 V DD Power Supply 7 W Wiper Terminal of Resistor 8 L Low Terminal of Resistor. The voltage at L can be greater than or less than the voltage at. Current can flow into or out of L. 6

7 CS INC U/D V W t CYC t CI t IL t I t IW NOTE: V W IS NOT A DIGITAL SIGNAL. IT REPRESENTS A WIPER TRANSITION. Figure 1. Digital Interface and Timing Diagram Detailed Description The contain a resistor array with 31 resistive elements (Figures 2 and 3). The MAX5471/MAX5474 have a total end-to-end resistance of 5kΩ, and the / have an end-to-end resistance of 1kΩ. The MAX5471/ wiper is connected to the high terminal, and the low terminal is internally connected to ground, making the device a variable resistor. The MAX5474/ allow access to the high, low, and wiper terminals for a standard voltage-divider configuration. The wiper is moved among the 32 tap points through a simple 3-wire interface. Nonvolatile memory allows the wiper position to be stored and recalled to the same point upon power-up. Digital Interface Logic inputs CS, U/D, and INC control the wiper position and store it in nonvolatile memory (see the Truth Table). The chip-select (CS) input enables the serial interface when low and disables the interface when high. The position of the wiper is stored when CS transitions from low to high and INC is high (see the Storing Wiper Position section). With the serial interface active (CS low), a high-to-low (falling edge) transition on INC moves the wiper position by one resistive element in the direction determined by the state of U/D. If U/D is high, the wiper increments and it increases the resistance between W and L (it decreases the resistance between and W). If U/D is low, the wiper decrements and it decreases the resistance between W and L (it increases the resistance between and W). The direction of the wiper t ID tdi t IC WIPER POSITION STORED t CP t WSC WIPER POSITION NOT STORED (state of U/D) can be changed at any time as long as the setup and hold times are met. Since the MAX5471/ have the wiper internally connected to, an increment command increases the resistance between and, and a decrement command decreases the resistance between and. The wiper performs a make-before-break transition, ensuring that there is never an open circuit during a transition from one resistor tap to another. When the wiper is at either end of the resistor array (max/min), additional transitions in the direction of the endpoint do not change the counter value (the wiper does not wrap around). Storing Wiper Position The position of the wiper is stored in nonvolatile memory whenever CS transitions low-to-high (rising edge) while INC is high. Upon power-up, the wiper returns to this stored position. By keeping INC low while taking CS high, the serial interface can be disabled and the potentiometer placed in standby without storing the latest wiper position. The factory-default wiper position is midscale. These devices can also be operated like a one-time programmable (OTP) device. Once the desired wiper position is trimmed and stored in nonvolatile memory, disable the serial interface by connecting CS to V DD, and INC to. The disabled interface places the device in standby and disallows any changes to the wiper position. In OTP mode, these devices become a fixed 3-terminal potentiometer or a 1-terminal resistor to with less than 1µA of supply current. t IK 7

8 CS U/D INC W L L Decrement L Increment L X No change X X No change X X No change X L Position not stored X Position stored = igh-to-low transition. = Low-to-high transition. X = Don t care. Truth Table Standby Mode The are always in standby mode, except during the transition of a logic input or while the wiper position is being stored. When in standby mode, the static supply current is reduced to less than 1µA and the resistive terminals (, W, and L) are unaffected. V DD 6 2 CS 1 INC 4 U/D 3 UP/DOWN COUNTER MAX5471 NONVOLATILE MEMORY 32-POSITION DECODER R 31 R 3 R 2 5 S 32 S 31 S 3 S 3 S 2 R W Applications Information The are intended for circuits requiring digitally controlled adjustable resistance, such as LCD contrast control (where voltage biasing adjusts the display contrast), or programmable filters with adjustable gain and/or cutoff frequency. Positive LCD Bias Control Figures 4 and 5 show an application where the voltagedivider or variable resistor is used to make an adjustable, positive LCD-bias voltage. The op amp provides buffering and gain to the resistor-divider network made by the potentiometer (Figure 4) or to a fixed resistor and a variable resistor (Figure 5). Programmable Filter Figure 6 shows the configuration of a 1st-order programmable filter. The gain of the filter is adjusted by R2, and the cutoff frequency is adjusted by R3. Use the following equations to calculate the gain (G) and the 3dB cutoff frequency (f C ): V DD CS INC U/D UP/DOWN COUNTER NONVOLATILE MEMORY fc MAX5474 R1 G = 1+ R2 1 = 2π R3 C 32-POSITION DECODER R 31 R 3 R 2 R 1 6 S 32 S 31 S 3 S 3 S 2 R W 7 W R 1 S 1 8 L S 1 Figure 2. MAX5471/ Functional Diagram Figure 3. MAX5474/ Functional Diagram 8

9 5V L MAX5474 W 3V V OUT Figure 4. Positive LCD Bias Control Using a Voltage-Divider 5V MAX5471 3V V OUT Figure 5. Positive LCD Bias Control Using a Variable Resistor V IN C MAX5471 Figure 6. Programmable Filter R3 R1 MAX5471 R2 V OUT Chip Information TRANSISTOR COUNT: 531 PROCESS: BiCMOS 9

10 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to 6L TIN SOT23.EPS 1

11 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to 11

12 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to MARKING PACKAGE OUTLINE, SOT-23, 8L BODY G 1 1 SOT23, 8L.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.