Home

ANALOG DEVICES AD5228 handbook

1. s 14 Layout and Power Supply Biasing sss 14 Applications cioe RR EROR anne 15 Manual Adjustable LED Driver eee 15 Adjustable Current Source for LED Driver 15 Automatic LCD Panel Backlight Control 16 Audio Amplifier with Volume Control 0 se sesse se see 16 Constant Bias with Supply to Retain Resistance Setting 17 Outline Dimensions pi 18 Ordering Guide ee dtes 18 ww BDTI C com ADI Rev 0 Page 2 of 20 AD5228 ELECTRICAL CHARACTERISTICS 10 kO 50 kQ 100 kQ versions Vpp 3 V 10 or 5 V 10 Va Von Vs 0 V 40 C lt Ta lt 105 unless otherwise noted Table 2 Parameter Symbol Conditions Min Typ Max Unit DC CHARACTERISTICS RHEOSTAT MODE Resistor Differential Nonlinearity R DNL Rwe A terminal no connect 0 5 40 05 0 5 LSB Resistor Integral Nonlinearity R INL Rwe A terminal no connect 05 0 1 0 5 LSB Nominal Resistor Tolerance ARas Ras 20 20 96 Resistance Temperature Coefficient ARas Ras x 10 AT 35 ppm C Wiper Resistance Rw Vop 2 7V 100 200 Q Voo 5 5V 50 Q DC CHARACTERISTICS POTENTIOMETER DIVIDER MODE Specifications apply to all RDACs Resolution N 5 Bits Integral Nonlinearity INL 0 5 0 05 40 5 LSB Differential Nonlinearity gt DNL 0 5 0 05 0 5 LSB Voltage Divider Temperature
2. 5 V 28 32 04422 0 011 04422 0 012 04422 0 013 AD5228 POTENTIOMETER MODE DNL LSB POTENTIOMETER MODE DNL LSB FSE LSB 0 4 8 12 16 20 24 28 32 CODE Decimal Figure 13 DNL vs Code vs Supply Voltages 0 4 8 12 16 20 24 28 32 CODE Decimal Figure 14 DNL vs Code Voo 5 V TEMPERATURE C Figure 15 Full Scale Error vs Temperature 04422 0 014 04422 0 016 ZSE LSB NOMINAL RESISTANCE Rag KO Rev 0 Page 8 of 20 0 50 0 35 Vpp 2 7V Vpp 5 5V 20 0 20 40 60 80 100 TEMPERATURE C Figure 16 Zero Scale Error vs Temperature IDD ACT 501A TYP 120 20 0 20 40 60 80 100 TEMPERATURE C Figure 17 Supply Current vs Temperature TEMPERATURE C Figure 18 Nominal Resistance vs Temperature 04422 0 017 04422 0 018 04422 0 019 WIPER RESISTANCE Ry RHEOSTAT MODE TEMPCO ARywg AT ppm C POTENTIOMETER MODE TEMPCO AVyslAT ppm C 120 100 80 60 40 20 40 20 0 20 40 60 80 100 TEMPERATURE C Figure 19 Wiper Resistance vs Temperature CODE Decimal Figure 20 Rheostat Mode Tempco ARws AT vs Code 0 4 8 12 16 20 24
3. 100 1k 10k 100k 1M FREQUENCY Hz Figure 25 PSRR 1 2 1 0 0 8 0 6 THEORETICAL Iwe Max mA 5 00V CH2 100mV M2 00ms A CH17 3 00V i gt v 3 92000ms Figure 26 Basic Increment 04422 0 028 5 00V CH2 100mV M2 00ms A CH1 1 2 60V id v 59 8000ms Figure 27 Repetitive Increment Rev 0 Page 10 of 20 CODE Decimal Figure 29 Maximum lws vs Code Ww g S Q 3 3 5 00V CH2 200mv A CH1 V 2 80V gt 800 000ms Figure 28 Autoscan Increment VA OPEN TA 25 C Rap 10kQ Rag 50kQ E ET 3 9 3 4 8 12 20 24 28 32 THEORY OF OPERATION The AD5228 is a 32 position manual up down digitally con trolled potentiometer with selectable power on preset The AD5228 presets to midscale when the PRE pin is tied to ground and to zero scale when PRE is tied to Vp Floating the PRE pin is not allowed The step up and step down operations require the activation of the PU push up and PD push down pins These pins have 100 kQ internal pull up resistors that the PU and PD activate at logic low The common practice is to apply external pushbuttons tactile switches as shown in Figure 30 AD5228 UP DOWN CONTROL DISCRETE Ow STEP AUTO SCAN DETECT OB BUTTON ZERO OR MID SCALE PRESET d ADAPTIVE DEBOUNCER PUSH DOWN BUTTON 04422 0 031 Because of ani switches during ct losu gle pu usually generates numerous bo
4. 1 kHz 14 nV NHz Typicals represent average readings at 25 Vpp 5 V Resistor position nonlinearity error R INL is the deviation from an ideal value measured between the maximum resistance and the minimum resistance wiper positions R DNL measures the relative step change from ideal between successive tap positions Parts are guaranteed monotonic 3 INL and DNL are measured at Vw with the RDAC configured as a potentiometer divider similar to a voltage output D A converter Va Voo and Vs 0 V Guaranteed by design and not subject to production test 5 DNL specification limits of 1 LSB maximum are guaranteed monotonic operating conditions Resistor Terminals A B and W have no limitations on polarity with respect to each other TREE 7 PU and PD have 100 kO internal pull up resistors lpo Acr Voo 100 KO losc internal oscillator operating current when PU or PD is connected to ground 8 Poss is calculated based on Ipp stay X Von only Ipo acr duration should be short Users should not hold PU or PD pin to ground longer than necessary to elevate power Note that all input value The lowest R value results in the fastest seffling highest ptio 96 of and timed av e avel of 1 witching efistics are measured using Voo 5 V 12 The debouncer keeps monitoring the logic low level once PU is connected to ground Once the signal lasts longer than 11 ms the debouncer assumes the last bounce is met and allows the AD5228 to inc
5. or any other conditions above those indicated in the operational section of this specification is not implied Exposure to absolute maximum rating conditions for extended periods may affect device reliability Maximum terminal current is bounded by the maximum applied voltage across any two of the A B and W terminals at a given resistance the maximum current handling of the switches and the maximum power dissipation of the package Voo 5 V Package power dissipation TL max Ta BA waw BDTI ESD CAUTION ESD electrostatic discharge sensitive device Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection Although this product features proprietary ESD protection circuitry permanent damage may occur on devices subjected to high energy electrostatic discharges Therefore proper ESD precautions are recommended to avoid performance degradation or loss of functionality C com ADI EDU ESD SENSITIVE DEVICE Rev 0 Page 5 of 20 AD5228 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 04422 0 003 Figure 6 SOT 23 8 Pin Configuration Table 4 Pin Function Descriptions Pin No Mnemonic Description 1 PU Push Up Pin Connect to the external pushbutton Active low A 100 KQ pull up resistor is connected to Von 2 PD Push Down Pin Connect to the external pushbutton Active low A 100 KQO pull up resistor is connect
6. shown in Figure 47 a similar low power digital potentiometer is biased with a 3 4 V 450 mA hour Li Ion cell phone battery The measurement shows that the device drains negligible power Constantly biasing the potentiometer is a practical approach because most of the portable devices do not require detachable batteries for charging Although the resistance setting of the AD5228 is lost when the battery needs to be replaced this event occurs so infrequently that the inconvenience is minimal for most applications AD5228 VD VD Vpp COMPONENT X COMPONENT Y a Za uz ce q d o 04422 0 047 AD5228 BATTERY VOLTAGE V 04422 0 048 DAYS Figure 47 Battery Consumption Measurement C cond ADI Rev 0 Page 17 of 20 AD5228 OUTLINE DIMENSIONS la 2 90 BSC 0 84 F 1 00 MAX 0 10 MAX 0 38 o le x 0 22 SEATING PLANE 0 20 0 08 y 0 60 ths gt ke 0 45 a 0 30 0 COMPLIANT TO JEDEC STANDARDS MO 193BA Figure 48 8 Lead Small Outline Transistor Package TSOT 8 Thin SOT 23 8 UJ 8 Dimensions shown in millimeters ORDERING GUIDE Full Container Model Ras kQ Tempe de Package Description Quanti Branding AD5228BUJZ1078RL 1 40 C 3 D3K AD5228BUJZ10 0 40 C sod D3K AD5228BUJZ5O0 RE7 0 40 8 000 D3L AD5228BUJZ50 R2 50 40 C to 105 C UJ
7. 28 CODE Decimal Figure 21 Potentiometer Mode Tempco AVws AT vs Code 32 04422 0 020 04422 0 021 04422 0 022 GAIN dB b 4 es GAIN dB GAIN dB Rev 0 Page 9 of 20 REF LEVEL DIV 0dB 6 0dB 6 16 STEPS 8 STEPS 4 STEPS AD5228 MARKER 469 390 941Hz MAG AIR 8 966dB TA 25 C Vpp 5 5V Va 50mV rms 18 TT 2 STEPS 1 STEP 1k 10k START 1 000 000Hz 100k 1M STOP 1 000 000 000Hz Figure 22 Gain vs Frequency vs Code Ras 10 kQ REF LEVEL DIV 0dB 6 0dB MARKER 97 525 233Hz MAG AIR 9 089dB TA 25 C Vpp 5 5V VA 50mV rms START 1 000 000Hz 100k 1M STOP 1 000 000 000Hz Figure 23 Gain vs Frequency vs Code Ras 50 kQ REF LEVEL DIV 6 0dB 6 0dB MARKER 51 404 427Hz MAG AIR 9 123dB TA 25 C Vpp 5 5V 0 16 STEPS Va 50mV rms 8 STEPS 4 STEPS 2 STEPS 1 STEP 1k 10k START 1 000 000Hz 100k 1M STOP 1 000 000 000Hz Figure 24 Gain vs Frequency vs Code Ras 100 kO 04422 0 050 04422 0 051 04422 0 052 AD5228 STEP MIDSCALE VA Vpp Vg OV PSRR dB 10 p 04422 0 026
8. ANALOG DEVICES FEATURES 32 position digital potentiometer 10 kO 50 kO 100 kO end to end terminal resistance Simple manual up down control Self contained requires only 2 pushbutton tactile switches Built in adaptive debouncer Discrete step up step down control Autoscan up down control with 4 steps per second Pin selectable zero scale midscale preset Low potentiometer mode tempco 5 ppm C Low rheostat mode tempco 35 ppm C Digital control compatible Ultralow power loo 0 4 pA typ and 3 pA max Low operating voltage 2 7 V to 5 5 V Automotive temperature range 40 C to 105 C Compact thin SOT 23 8 2 9 mm x 3 mm Pb free package APPLICATIONS Mechanical potentiometer and trimmer replacements LCD backlight contrast and brightness controls Digital volume control Portable i Electronic GENERAL DESCRIPTION The AD5228 is Analog Devices latest 32 step up step down control digital potentiometer emulating mechanical potenti ometer operation Its simple up down control interface allows manual control with just two external pushbutton tactile switches The AD5228 is designed with a built in adaptive debouncer that ignores invalid bounces due to contact bounce commonly found in mechanical switches The debouncer is adaptive accommodating a variety of pushbutton tactile switches that generally have less than 10 ms of bounce time during contact closures When choosing the switch the user should consult the timing
9. Coefficient AVw Vw x 10 AT Midscale 5 ppm C Full Scale Error Vwese 2415 steps from midscale 1 0 5 0 LSB Zero Scale Error Vwzse 16 steps from midscale 0 0 3 0 5 LSB RESISTOR TERMINALS Voltage Ran JW Vo V ase AL C pF Capacitance W Cw f 1 MHz measured to GND pF Common Mode Leakage lem Va Vs z Vw 1 nA PU PD INPUTS Input High Vin Von 5V 2 4 5 5 V Input Low Vit Voo 5V 0 0 8 V Input Current li Vin OVor5V 1 HA Input Capacitance C 5 pF POWER SUPPLIES Power Supply Range Voo Voo 5 V PU PD Voo 2 7 55 V Supply Standby Current Ipp srav 0 4 3 HA Supply Active Current lop Acr Voo 5 V PU or PD OV 50 110 pA Power Dissipation Poiss Vop 5V 17 HW Power Supply Sensitivity PSSR Von 5 V 1096 0 01 0 05 96 96 Footnotes on next page Rev 0 Page 3 of 20 AD5228 Parameter Symbol Conditions Min Typ Max Unit DYNAMIC CHARACTERISTICS 0 1 Built in Debounce and Settling Time 2 tos 6 ms PU Low Pulse Width teu 12 ms PD Low Pulse Width teo 12 ms PU High Repetitive Pulse Width teu_rep 1 Us PD High Repetitive Pulse Width teo_rep 1 us Autoscan Start Time tAS START PUorPD 0V 06 08 12 s Autoscan Time tas PUorPD 0V 0 16 0 25 038 s Bandwidth 3 dB BW 10 Ras 10 kO midscale 460 kHz BW 50 Ras 50 kO midscale 100 kHz BW 100 Ras 100 kO midscale 50 kHz Total Harmonic Distortion THD Va 1Vrms Ras 10 kO 0 05 Vs 0V dc f 1 kHz Resistor Noise Voltage EN wB Rws 5 KO f
10. TSOT 8 250 D3L AD5228BUJZ1007 RL7 100 40 C to 105 C UJ TSOT 8 3000 D3M AD5228BUJZ100 R2 100 40 C to 105 C UJ TSOT 8 250 D3M AD5228EVAL 10 Evaluation Board 1 The end to end resistance Rasis available in 10 kO 50 kO and 100 kQ The final three characters of the part number determine the nominal resistance value for example 10 kQ 10 2 Z Pb free part Rev 0 Page 18 of 20 AD5228 NOTES ww BDTI C com ADI AD5228 NOTES ww BDTI C com ADI 2004 Analog Devices Inc All rights reserved Trademarks and ANALOG registered trademarks are the property of their respective owners WWW ana l 0 g COM sesse ad DEVICES Rev 0 Page 20 of 20
11. and PD pins are usually connected to pushbutton tactile switches for manual operation but the AD5228 can also be controlled digitally It is recommended to add external MOSFETS or transistors that simplify the logic controls AD5228 UP DOWN CONTROL DISCRETE QW STEP AUTO SCAN DETECT 04422 0 039 Figure 38 Digital Control with External MOSFETs TERMINAL VOLTAGE OPERATION RANGE The AD5228 is designed with internal ESD diodes for protection These diodes also set the voltage boundary of the terminal operating voltages Positive signals present on Terminal A B or W that exceed Vp are clamped by the forward biased diode There is no polarity constraint between Va Vw and Vs but they cannot be higher than Von or lower than GND Vpp A w B 2 0 040 8 GND 3 Figure 39 Maximum Terminal Voltages Set by Voo and GND Rev 0 Page 13 of 20 AD5228 POWER UP AND POWER DOWN SEQUENCES Because of the ESD protection diodes that limit the voltage compliance at Terminals A B and W Figure 39 it is important to power on Vp before applying any voltage to Terminals A B and W Otherwise the diodes are forward biased such that Vp is powered on unintentionally and can affect other parts of the circuit Similarly Vp should be powered down last The ideal power on sequence is in the following order GND Vop and Vaniw The order of powering Va Vs and Vw is not important as long as they are powered on aft
12. around 0 1 V and adjusted by the digital potentiometer I Voor 8 LED R SET Rser should be small enough to conserve power but large enough to limit maximum LED current R3 should also be used in par allel with AD5228 to limit the LED current within an achievable range A wider current adjustment range is possible by lowering the R2 to RI ratio as well as changing R3 accordingly IN U2 ADP1610 O Vour D2 D3 we D4 L1 SLF6025 100M1RO D1 MBRO520LT1 R3 2000 04422 0 044 Figure 43 Adjustable Current Source for LEDs in Series Rev 0 Page 15 of 20 AD5228 AUTOMATIC LCD PANEL BACKLIGHT CONTROL With the addition of a photocell sensor an automatic brightness control can be achieved As shown in Figure 44 the resistance of the photocell changes linearly but inversely with the light output The brighter the light output the lower the photocell resistance and vice versa The AD5228 sets the voltage level that is gained up by U2 to drive N1 to a desirable brightness With the photocell acting as the variable feedback resistor the change in the light output changes the R2 resistance therefore causing U2 to drive N1 accordingly to regulate the output This simple low cost implementation of an LED controller can compensate for the temperature and aging effects typically found in high power LEDs Similarly for power efficiency a PWM signal can be applied at the gate of N2 to switch the LED on and o
13. ed to Von 3 A Resistor Terminal A GND lt Va lt Vpp 4 GND Common Ground 5 W Wiper Terminal W GND lt Vw lt Voo 6 B Resistor Terminal B GND lt Vs lt Vpp 7 PRE Power On Preset Output midscale if PRE GND output zero scale if PRE Vpp Do not let the PRE pin float No pull up resistor is needed 8 Voo Positive Power Supply 2 7 V to 5 5 V ww BDTI C com ADI Rev 0 Page 6 of 20 TYPICAL PERFORMANCE CHARACTERISTICS RHEOSTAT MODE INL LSB RHEOSTAT MODE INL LSB RHEOSTAT MODE DNL LSB 0 10 0 4 8 12 16 20 24 CODE Decimal Figure 7 R INL vs Code vs Supply Voltages 28 32 0 4 8 12 16 20 24 CODE Decimal 28 Figure 8 R INL vs Code vs Temperature Vpp 5 V 32 0 4 8 12 16 20 24 CODE Decimal Figure 9 R DNL vs Code vs Supply Voltages 28 32 04422 0 008 04422 0 009 04422 0 010 POTENTIOMETER MODE INL LSB RHEOSTAT MODE DNL LSB POTENTIOMETER MODE INL LSB Rev 0 Page 7 of 20 AD5228 8 12 16 20 24 CODE Decimal Figure 10 R DNL vs Code vs Temperature Vpp 5 V 8 12 16 20 24 CODE Decimal Figure 11 INL vs Code vs Supply Voltages 28 32 8 12 16 20 24 CODE Decimal Figure 12 INL vs Code Voo
14. entiometer Mode Operation If all three terminals are used the operation is called potenti ometer mode The most common configuration is the voltage divider operation as shown in Figure 36 C DA C ve Ww B 04422 0 037 Figure 36 Potentiometer Mode Configuration The change of Vws is known provided that the AD5228 maximum or minimum scale has not been reached during operation If the effect of wiper resistance is ignored the transfer functions can be simplified as PU AVwg V 5 WB 3 5 PD AVywg V 6 WB 32 VA 6 Unlike in rheostat mode operation where the absolute tolerance is high potentiometer mode operation yields an almost ratio metric function of PU 32 or PD 32 with a relatively small error contributed by almost can CMOS switchlre c 2 coefficients the ratiometric adjustment also reduces the overall temperature coefficient effect to 5 ppm C except at low value codes where Rw dominates Potentiometer mode operations include an op amp input and feedback resistors network and other voltage scaling applications The A W and B terminals can be input or output terminals and have no polarity constraint provided that Vas Vwa and Vws do not exceed Vpp to GND AD5228 CONTROLLING INPUTS All PU and PD inputs are protected with a Zener ESD structure as shown in Figure 37 DECODE pu AND DEBOUNCE CKT 04422 0 038 Figure 37 Equivalent ESD Protection in PU and PD Pins PU
15. er Vpp The states of the PU and PD pins can be logic high or floating but they should not belogiclow during power on LAYOUT AND POWER SUPPLY BIASING It is always a good practice to use compact minimum lead length layout design The leads to the input should be as direct as possible with a minimum conductor length Ground paths should have low resistance and low inductance It is also good practice to bypass the power supplies with quality capacitors Low ESR equivalent series resistance 1 uF to 10 uF tantalum or electrolytic capacitors should be applied at the supplies to minimize any transient disturbance and to filter low frequency ripple Figure 39 illustrates the basic supply bypassing configu ration for the AD5228 AD5228 M O DD c2 C1 10uF 0 1uF FA 1 04422 0 041 Figure 40 Power Supply Bypassing ww BDTI C com ADI Rev 0 Page 14 of 20 APPLIGATIONS MANUAL ADJUSTABLE LED DRIVER The AD5228 can be used in many electronics level adjustments such as LED drivers for LCD panel backlight controls Figure d1 shows a manually adjustable LED driver The AD5228 sets the voltage across the white LED D1 for the brightness control Since U2 handles up to 250 mA a typical white LED with V of 3 5 V requires a resistor R1 to limit U2 current This circuit is simple but not power efficient The U2 shutdown pin can be toggled with a PWM signal to conserve power Cc Oo PUSH DOWN BUTTON 04422 0 042 Fi
16. ff without noticeable effect N z Ew e o N 04422 0 045 Figure 44 Automatic LCD Panel Backlight Control AUDIO AMPLIFIER WITH VOLUME CONTROL The AD5228 and SSM2211 can form a 1 5 W audio amplifier with volume control that has adequate power and quality for portable devices such as PDAs and cell phones The SSM2211 can drive a single speaker differentially between Pins 5 and 8 without any output capacitor The high pass cutoff frequency is fin 1 2 x n x RI x CI The SSM2211 can also drive two speakers as shown in Figure 45 However the speakers must be configured in single ended mode and output coupling capacitors are needed to block the dc current The output capacitor and the speaker load form an additional high pass cutoff frequency as fip 1 2 x n x R5 x C3 As a result C3 and C4 must be large to make the frequency as low as fm 2 5V p p AUDIO INPUT O 5VO c6 c7 104 TOLF T PUSH UP BUTTON JL PUSH DOWN BUTTON 04422 0 046 Figure 45 Audio Amplifier with Volume Control Rev 0 Page 16 of 20 CONSTANT BIAS WITH SUPPLY TO RETAIN RESISTANCE SETTING Users who consider EEMEM potentiometers but cannot justify the additional cost and programming for their designs can consider constantly biasing the AD5228 with the supply to retain the resistance setting as shown in Figure 46 The AD5228 is designed specifically with low power to allow power conser vation even in battery operated systems As
17. gure 41 Low Cost Adjustable LED Driver ADJUSTABLE CURRENT SOURCE FOR LED DRIVER Because LED brightness is a function of current rather than of forward voltage an adjustable current source is preferred as shown in Figure 42 The load current s of the AD5228 di 7 Ip Rser The U1 ADP3333ARM 1 5 is a 1 5 V LDO that is lifted above or lowered below 0 V When V ws of the AD5228 is at its minimum there is no current through D1 so the GND pin of U1 is at 1 5 V if U3 is biased with the dual supplies As a result some of the U2 low resistance steps have no effect on the output until the U1 GND pin is lifted above 0 V When Vws of the AD5228 is at its maximum Vour becomes VL Vas so the U1 supply voltage must be biased with adequate headroom Similarly PWM signal can be applied at the U1 shutdown pin for power efficiency PUSH UP BUTTON O PUSH DOWN BUTTON o 04422 0 043 Figure 42 Adjustable Current Source for LED Driver AD5228 ADJUSTABLE HIGH POWER LED DRIVER The previous circuit works well for a single LED Figure 43 shows a circuit that can drive three to four high power LEDs The ADP1610 is an adjustable boost regulator that provides the voltage headroom and current for the LEDs The AD5228 and the op amp form an average gain of 12 feedback network that servos the Rser voltage and the ADP1610 FB pin 1 2 V band gap reference voltage As the loop is set the voltage across Rser is regulated
18. ideo game player can press a pushbutton switch in 40 ms Rev 0 Page 11 of 20 AD5228 If the PU button is held for longer than 1 second continuously holding it activates autoscan mode such that the AD5228 increments by four Rws steps per second see Figure 3 Whenever the maximum Rws Ra is reached Rws stops incrementing regardless of the state of the PU pin Any continu ous holding of the PU pin to logic low simply elevates the supply current When both PU and PD buttons are pressed Rws decrements until it stops at zero scale All the preceding descriptions apply to PD operation Due to the tolerance of the internal RC oscillator all the timing information given previously is based on the typical values which can vary 430 The AD5228 debouncer is carefully designed to handle common pushbutton tactile switches Other switches that have excessive bounces and duration are not suitable to use in conjunction with the AD5228 RDAC UP DOWN CTRL AND DECODE BE KK OB 04422 0 035 Rs Rapi32 Figure 34 AD5228 Equivalent RDAC Circuit PROGRAMMING THE DIGITAL POTENTIOMETERS Rheostat Operation If only the W to B or W to A terminals are used as variable resistors the unused terminal can be opened or shorted with W Such operation is called rheostat mode and is shown in Figure 35 2 Figure 35 Rheostat Mode Configuration 04422 0 036 The end to end resistance Ras has 32 contact points acces
19. of 40 C to 105 C The AD5228 s simple interface small footprint and very low cost enable it to replace mechanical potentiometers and trimmers with typically 3x improved resolution solid state reliability and faster adjustment resulting in considerable cost saving in end users systems Users who consider EEMEM potentiometers should refer to the recommendations in the Applications section Table 1 Truth Table PU PD Operation 0 0 Rws Decrement 0 1 Rws Increment 1 0 Rwa Decrement 1 1 Rws Does Not Change Rwa increments if Rus decrements and vice versa One Technology Way P O Box 9106 Norwood MA 02062 9106 U S A Tel 781 329 4700 www analog com Fax 781 326 8703 2004 Analog Devices Inc All rights reserved AD5228 TABLE OF CONTENTS Electrical Characteristics seen 3 Interface Timing Diagrams seen 4 Absolute Maximum Ratings sek see ee ee ee ee ek ek ee ee 5 PES VERE EE EE ID 5 Pin Configuration and Function Descriptions 6 Typical Performance Characteristics ssseee 7 Theory of Operation se see ee ee ee ee Re oe oe ee ee ee Re ee ee 11 Programming the Digital Potentiometers 12 Controlling Inputs sesse se seek ek ee ee ee ee ek ek ek ee ee 13 Terminal Voltage Operation Range se 13 REVISION HISTORY Revision 0 Initial Version Power Up and Power Down Sequences
20. rement by one step If the PU signal remains at low and reaches tas starr the AD5528 increments again see Figure 7 Similar characteristics apply to PD operation dissipation Bandwidth noise and settling time are dependent bandwidth The highe th mini 1 All dynamic chara amp te INTERFACE TIMING DIAGRAMS RwB gt tos e Rwg Figure 2 Increment Rwe in Discrete Steps 04422 0 004 04422 0 006 Figure 4 Decrement Rws in Discrete Steps PD PU ag tas START t lt lt aes 2 tos as tas ja RwB RwB e jet Figure 3 Increment Rws in Autoscan Mode 04422 0 005 04422 0 007 Figure 5 Decrement Rwe in Autoscan Mode Rev 0 Page 4 of 20 ABSOLUTE MAXIMUM RATINGS AD5228 Table 3 Parameter Rating Voo to GND 0 3V 47V Va Ve Vw to GND OV Voo PU PD PRE Voltage to GND OV Voo Maximum Current lws Iwa Pulsed 20 mA lws Continuous Rws lt 5 kO A open 1 mA Ilwa Continuous Rwa lt 5 kO B open 1 mA las Continuous 500 uA 100 pA Ras 10 kQ 50 kQ 100 kQ 50 HA Operating Temperature Range 40 C to 105 C Maximum Junction Temperature 150 C Timax Storage Temperature 65 C to 150 C Lead Temperature 245 C Soldering 10 s 30 s Thermal Resistance Ba 230 C W Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device This is a stress rating only and functional operation of the device at these
21. sed by the wiper terminal plus the B terminal contact if Rws is used Pushing the PU pin discretely increments Rws by one step The total resistance becomes Rs Rw as shown in Figure 34 The change of Rws can be determined by the number of discrete PU executions provided that its maximum setting is not reached during operation ARws can therefore be approximated as ARWB PUA Ry 1 R ARwg pe Ry 2 where PU is the number of push up executions PD is the number of push down executions Raz is the end to end resistance Rwis the wiper resistance contributed by the on resistance of the internal switch Similar to the mechanical potentiometer the resistance of the RDAC between the Wiper W and Terminal A also produces a complementary resistance Rwa When these terminals are used eB terminal can O opened o d dt can also be e gs are not e Aya b2 On 3 ARA 6e PD AE Ry 4 Note that Equations 1 to 4 do not apply when PU and PD 0 execution Because in the lowest end of the resistor string a finite wiper resistance is present care should be taken to limit the current flow between W and B in this state to a maximum pulse current of no more than 20 mA Otherwise degradation or possible destruction of the internal switches can occur The typical distribution of the resistance tolerance from device to device is process lot dependent and 420 tolerance is possible Rev 0 Page 12 of 20 Pot
22. specification of the switch to ensure its suitability in an AD5228 application 1 The terms digital potentiometer and RDAC are used interchangeably Rev 0 Information furnished by Analog Devices is believed to be accurate and reliable However no responsibility is assumed by Analog Devices for its use nor for any infringements of patents or other rights of third parties that may result from its use Specifications subject to change without notice No license is granted by implication or otherwise under any patent or patent rights of Analog Devices Trademarks and registered trademarks are the property of their respective owners 32 Position Manual Up Down Control Potentiometer AD5228 FUNCTIONAL BLOCK DIAGRAM AD5228 UPIDOWN Vpp O CONTROL DISCRETE QW STEP AUTO SCAN DETECT BUTTON L ADAPTIVE ZERO OR MID mm DEBOUNCER SCALE PRESET L PUSH DOWN BUTTON 04422 0 001 Figure 1 The AD5228 can increment or decrement the resistance in discrete steps or in autoscan mode When the PU or PD button is pressed briefly no longer than 0 6 s the resistance of the AD5228 changes by one step When the PU or PD button is held device activates the continuously for more thaf a segend the CO s fo si ie The 2 Iso nt olled dig features simplify microcontroller usage The AD5228 is available in a compact thin SOT 23 8 TSOT 8 package The part is guaranteed to operate over the automotive temperature range
23. unces during contact closure Note that the term pushbutton refers specifically to a pushbutton tactile switch or a similar switch that has 10 ms or less bounce time during contact closure Figure 31 shows the characteristics of one such switch the KRS 3550 tactile switch Figure 32 and Figure 33 show close ups of the initial bounces and end bounces respectively 04422 0 032 1 00V M40 0ms 20 4096 A CH1 L 2 38V Figure 31 Typical Tactile Switch Characteristics AD5228 04422 0 033 1 00V M100us 20 20 A CH1 V 2 38V Figure 32 Close Up of Initial Bounces di 04422 0 034 M10 0us A CH1 2 38V 20 2096 1 00V Figure 33 Close Up of Final Bounces The following paragraphs describes the PU incrementing operation Similar characteristics apply to the PD decrementing operation The AD5228 features an adaptive debouncer that monitors the duration of the logic low level of PU signal between bounces If the PU logic low level signal duration is shorter than 7 ms the debouncer ignores it as an invalid incrementing command Whenever the logic low level of PU signal lasts longer than 11 ms the debouncer assumes that the last bounce is met and therefore increments Rws by one step Repeatedly pressing the PU button for fast adjustment without missing steps is allowed provided that each press is not shorter than tev which is 12 ms see Figure 2 As a point of reference an advanced v

ANALOG DEVICES AD5228 handbook

Contents

Download Pdf Manuals

Related Search

Related Contents