19-1848; Rev 0; 10/00 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 Features ♦ Miniature 8-Pin SOT23 (3mm x 3mm) ♦ 256 Tap Positions ♦ Ultra-Low 0.1µA Supply Current ♦ Single-Supply Operation: +2.7V to +5.5V ♦ Low Ratiometric Temperature Coefficient: 5ppm/°C ♦ Power-On Reset: Wiper Goes to Midscale (Position 128) ♦ Glitchless Switching Between the Resistor Taps The MAX5400/MAX5401 serve well in applications requiring digitally controlled resistors, including adjustable voltage references and programmable gain amplifiers (PGAs). A nominal end-to-end resistor temperature coefficient of 50ppm/°C allows these parts to be used as variable resistors in applications such as low-tempco adjustable gain and other circuit configurations. ♦ 3-Wire SPI™-Interface Compatible ♦ 50kΩ/100kΩ Resistor Values Ordering Information Two resistance values are available: 50kΩ (MAX5400) and 100kΩ (MAX5401). Each device is guaranteed over the extended industrial temperature range (-40°C to +85°C). TEMP. RANGE PART ________________________Applications PINPACKAGE R (kΩ) MAX5400EKA-T -40°C to +85°C 8-SOT23 50 MAX5401EKA-T -40°C to +85°C 8-SOT23 100 SOT-PoT is a trademark of Maxim Integrated Products. SPI is a trademark of Motorola, Inc. Mechanical Potentiometer Replacement Low-Drift PGAs Pin Configuration appears at end of data sheet. Adjustable Voltage References Functional Diagram VDD H 8 DIN 8-BIT SHIFT REGISTER 8 8-BIT LATCH DECODER W L MAX5400/MAX5401 SCLK CS CLOCK LOGIC POR GND ________________________________________________________________ Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX5400/MAX5401 General Description The MAX5400/MAX5401 digital potentiometers offer 256-tap SOT-PoT™ digitally controlled variable resistors in tiny 8-pin SOT23 packages. Each device functions as a mechanical potentiometer, consisting of a fixed resistor string with a digitally controlled wiper contact. They operate from +2.7V to +5.5V single-supply voltages and use an ultra-low supply current of 0.1µA. These devices also provide glitchless switching between resistor taps, as well as a convenient poweron reset that sets the wiper to the midscale position at power-up. A low 5ppm/°C ratiometric temperature coefficient makes it ideal for applications requiring low drift. MAX5400/MAX5401 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 ABSOLUTE MAXIMUM RATINGS VDD to GND ............................................................. -0.3V to +6V DIN, SCLK, CS to GND ............................................-0.3V to +6V H, L, W to GND...........................................-0.3V to (VDD + 0.3V) Maximum Continuous Current into Pins H, L, and W ...........................................................±1mA Continuous Power Dissipation (TA = +70°C) 8-Pin SOT23 (derate 8.7mW/°C above +70°C)...........697mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ..................................................…+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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 CHARACTERISTICS (VDD = +5V, VH = VDD, VL = 0, TA = TMIN to TMAX. Typical values are at TA = +25°C, unless otherwise noted. Parameters are measured at TA = +25°C. Values over full temperature range are guaranteed by design.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC PERFORMANCE (Voltage Divider Mode) Resolution N 8 Bits Integral Nonlinearity (Notes 1, 2) INL ±1/2 LSB Differential Nonlinearity (Notes 1, 2) DNL ±1/2 LSB End-to-End Resistor Tempco TCR Ratiometric Resistor Tempco Full-Scale Ratio Error Zero-Scale Ratio Error 50 ppm/°C 5 ppm/°C MAX5400 -0.8 MAX5401 -0.4 MAX5400 +0.8 MAX5401 +0.4 LSB LSB POWER SUPPLIES Supply Voltage VDD Supply Current IDD 2.7 CS = SCLK = DIN = VDD VDD = 5V 0.7 VDD = 2.7V 0.1 5.5 V 5 µA µA DC PERFORMANCE (Variable Resistor Mode) Resolution Integral Nonlinearity (Notes 1, 3) Differential Nonlinearity (Notes 1, 3) N 8 Bits ±1 VCC = 5V INL DNL VCC = 3V MAX5400 ±1.5 MAX5401 ±1 VCC = 5V ±1/2 VCC = 3V ±1/2 LSB LSB DC PERFORMANCE (Resistor Characteristics) Wiper Resistance (Note 4) RW 250 Wiper Capacitance CW 25 End-to-End Resistance RHL 2 800 MAX5401 75 100 125 MAX5400 37.5 50 62.5 _______________________________________________________________________________________ Ω pF kΩ 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 (VDD = +5V, VH = VDD, VL = 0, TA = TMIN to TMAX. Typical values are at TA = +25°C, unless otherwise noted. Parameters are measured at TA = +25°C. Values over full temperature range are guaranteed by design.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DIGITAL INPUTS Input High Voltage VIH VCC = 5V Input Low Voltage VIL VCC = 5V Input High Voltage VIH VCC = 3V Input Low Voltage VIL VCC = 3V 0.7 ✕ VDD V 0.3 ✕ VDD 0.7 ✕ VDD V 0.3 ✕ VDD ±1.0 Input Leakage Current Input Capacitance V 5.0 V µA pF TIMING CHARACTERISTICS (Voltage Divider Mode) Wiper Settling Time tIL MAX5400 (to 50% of final value, from code 0 to code 128) 300 MAX5401 (to 50% of final value, from code 0 to code 128) 600 ns TIMING CHARACTERISTICS (Digital) (Note 5) SCLK Clock Period tCP 100 ns SCLK Pulse Width High tCH 40 ns SCLK Pulse Width Low tCL 40 ns CS Fall to SCLK Rise Setup Time tCSS 40 ns SCLK Rise to CS Rise Hold Time tCSH 0 ns tDS 40 ns DIN Setup Time DIN Hold Time tDH 0 ns SCLK Rise to CS Fall Delay tCS0 10 ns CS Rise to SCLK Rise Hold tCS1 40 ns CS Pulse Width High tCSW 100 ns Note 1: Linearity is defined in terms of the H to L code-dependent resistance. Note 2: The DNL and INL are measured with the potentiometer configured as a voltage-divider with H = VDD and L = 0. The wiper terminal is unloaded and measured with an ideal voltmeter. Note 3: The DNL and INL are measured with the potentiometer configured as a variable resistor. H is unconnected and L = 0. The wiper terminal is driven with a source current of 80µA for the 50kΩ configuration and 40µA for the 100kΩ configuration. Note 4: The wiper resistance is measured assuming the source currents given in Note 2. Note 5: Digital timing is guaranteed by design. _______________________________________________________________________________________ 3 MAX5400/MAX5401 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) END-TO-END RESISTANCE % CHANGE vs. TEMPERATURE 200 100 MAX5400toc02 50kΩ -0.03 -0.05 -0.07 0 1 2 3 4 VARIABLE RESISTOR DNL vs. INPUT CODE (50kΩ) MAX5400 Toc04 0.020 0.015 (LSB) 30 25 20 15 5 0 96 0.15 0.10 0.005 0.05 0 -0.005 -0.05 -0.010 -0.10 -0.015 -0.15 -0.20 0 32 64 96 128 160 192 224 256 0 32 64 96 128 160 192 224 256 INPUT CODE-DECIMAL VARIABLE RESISTOR DNL vs. INPUT CODE (100kΩ) VARIABLE RESISTOR INL vs. INPUT CODE (100kΩ) SUPPLY CURRENT vs. TEMPERATURE 0.05 (LSB) 0.005 0 0 -0.005 -0.05 -0.010 -0.10 -0.015 -0.15 96 128 160 192 224 256 INPUT CODE-DECIMAL 0.6 0.4 VDD = +3V 0.2 0 -0.20 64 VDD = +5V 0.8 SUPPLY CURRENT (µA) 0.15 0.10 1.0 MAX5400 Toc08 MAX5400 Toc07 0.20 0.010 -1.020 4 0 INPUT CODE-DECIMAL 0.015 32 128 160 192 224 256 INPUT CODE-DECIMAL 0.020 0 96 0.20 0.010 128 160 192 224 256 64 VARIABLE RESISTOR INL vs. INPUT CODE (50kΩ) -0.020 64 32 INPUT CODE-DECIMAL 10 32 30 0 (LSB) 35 0 40 0 W-to-L RESISTANCE vs. INPUT CODE (50kΩ) 40 50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 5 TEMPERATURE (°C) VDD = 2.7V to 5.5V 45 60 10 WIPER VOLTAGE (V) 50 70 20 -0.09 -0.11 0 W-TO-L RESISTANCE (kΩ) -0.01 80 MAX5400 Toc06 VDD = +5V 100kΩ 0.01 VDD = 2.7V to 5.5V 90 0 32 64 96 128 160 192 224 256 INPUT CODE-DECIMAL -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TEMPERATURE (°C) _______________________________________________________________________________________ MAX5400toc09 300 0.03 W-TO-L RESISTANCE (kΩ) VDD = +3V 400 100 MAX5400 Toc05 WIPER RESISTANCE (Ω) 500 0.05 END-TO-END RESISTANCE % CHANGE MAX5400 toc01 600 W-to-L RESISTANCE vs. INPUT CODE (100kΩ) MAX5400 Toc03 WIPER RESISTANCE vs. VOLTAGE (LSB) MAX5400/MAX5401 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 TAP-to-TAP SWITCHING TRANSIENT (FROM CODE 127 toc CODE 128) SUPPLY CURRENT vs. INPUT LOGIC VOLTAGE MAX5400 Toc10 MAX5400 Toc11 10 10mV/div 2.5V 5V/div CS 0 SUPPLY CURRENT (mA) 1 VW-L VDD = +5V 0.1 0.01 VDD = +3V 0.001 0.0001 0 1 2 3 4 5 DIGITAL INPUT VOLTAGE (V) VOLTAGE DIVIDER DNL vs. INPUT CODE (50kΩ) 0.08 0.06 VDD = +2.7V to +5.5V 0.15 0.10 0.04 0.05 (LSB) 0.02 (LSB) MAX5400 Toc13 0.20 MAX5400 Toc12 0.10 VOLTAGE DIVIDER INL vs. INPUT CODE (50kΩ) 0 -0.02 0 -0.05 -0.04 -0.10 -0.06 -0.15 -0.08 -0.10 -0.20 0 32 64 96 128 160 192 224 256 0 32 64 INPUT CODE-DECIMAL 96 128 160 192 224 256 INPUT CODE-DECIMAL Pin Description PIN NAME 1 L 2 GND FUNCTION Low Terminal of Resistor Ground 3 CS Chip Select Input 4 DIN Serial Data Input 5 SCLK 6 VDD 7 W Wiper Terminal 8 H High Terminal of Resistor Clock Input Power Supply. Bypass with a 0.1µF capacitor to GND. _______________________________________________________________________________________ 5 MAX5400/MAX5401 Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX5400/MAX5401 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 POT REGISTER LOADED CS SCLK 8TH CLOCK PULSE 1ST CLOCK PULSE DIN D7 D6 D5 D4 D3 D2 D1 D0 LSB MSB TIME Figure 2. Serial Interface Timing Diagram CS tCSW tCSO tCS1 tCSS tCH tCL tCP tCSH SCLK tDS tDH DIN Figure 3. Detailed Serial Interface Timing Diagram Detailed Description The MAX5400/MAX5401 consists of 255 fixed resistors in series between pins H and L. The potentiometer wiper (pin W) can be programmed to access any one of the 256 different tap points on the resistor string. The MAX5400/MAX5401 uses a 3-wire serial data interface to control the wiper tap position. This write-only interface contains three inputs: Chip-Select (CS), Data In (DIN), and Data Clock (SCLK). When CS is taken low, data from the DIN pin is synchronously loaded into the 8-bit serial shift register on the rising edge of each SCLK pulse. The MSB is shifted in first as shown in Figure 4. Note that if CS is not kept low during the entire data stream, the data will be corrupted and the device 6 will need to be reloaded. After all 8 data bits have been loaded into the shift register, they are latched into the decoder once CS is taken high. The decoder switches the potentiometer wiper to the tap position that corresponds to the 8-bit input data. Each resistor cell is 50kΩ/255 or 196.1Ω for the MAX5400 and 100kΩ/255 or 392.2Ω for the MAX5401. The MAX5400/MAX5401 feature power-on reset (POR) circuitry that sets the wiper to the midscale position at power-up by loading a binary value of 128 into the 8-bit latch. The MAX5400/MAX5401 can be used as a variable resistor by connecting pin W to either pin H or pin L. _______________________________________________________________________________________ 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 B0 (D7) B1 (D6) B2 (D5) B3 (D4) B4 (D3) B5 (D2) B6 (D1) (MSB) FIRST BIT IN B7 (D0) (LSB) LAST BIT IN Figure 4. Serial Data Format Applications Information The MAX5400/MAX5401 are intended for a variety of circuits that require accurate, fine-tuning adjustable resistance, such as adjustable voltage or adjustable gain circuit configurations. The MAX5400/MAX5401 are primarily used in either a potentiometer divider or a variable resistor configuration. Adjustable Current-to-Voltage Converter Figure 5 shows the MAX5400/MAX5401 being used with a MAX4250 low-noise op amp to fine tune a current-to-voltage converter. Pins H and W of the MAX5400/MAX5401 are connected to the node between R3 and R2 and pin L is connected to ground. resistor configuration so that the gain of the circuit can be digitally controlled. Adjustable Voltage Reference In Figure 7, the MAX5400/MAX5401 are shown with the MAX6160 to make an adjustable voltage reference. In this circuit, the H pin of the MAX5400/MAX5401 is connected to the OUT pin of the MAX6160, the L pin of the MAX5400/MAX5401 is connected to GND, and the W pin of the MAX5400/MAX5401 is connected to the ADJ pin of the MAX6160. The MAX5400/MAX5401 allow precise tuning of the voltage reference output. A low 5ppm/°C ratiometric tempco allows a very stable adjustable voltage over temperature. Adjustable Gain Amplifier The MAX5400/MAX5401 are used again with the MAX4250 to make a digitally adjustable gain circuit as shown in Figure 6. The normal feedback resistor is replaced with the MAX5400/MAX5401 in a variable +5V R3 VS +5V R1 VO R2 VO MAX4250 R2 MAX4250 R1 VO / IS = R3(1 + R2 / R1)+ R2 VO / VS = 1 + R2 / R1 Figure 5. I to V Converter Figure 6. Noninverting Amplifier _______________________________________________________________________________________ 7 MAX5400/MAX5401 DATA WORD MAX5400/MAX5401 256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23 Chip Information +5V TRANSISTOR COUNT: 3769 TECHNOLOGY: BiCMOS VIN VO REF OUT MAX6160 ADJ H W GND L VO = 1.23V × 100kΩ FOR MAX5401 R2(kΩ) VO = 1.23V × 50kΩ FOR MAX5400 R2(kΩ) Figure 7. Adjustable Voltage Reference Pin Configuration TOP VIEW L 1 GND 2 CS 3 MAX5400/ MAX5401 DIN 4 8 H 7 W 6 VDD 5 SCLK SOT23 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.