DS1809 dallastat DS1809 preliminary 061798 1/5 features ? 64position linear taper ? two nonvolatile wiper storage options ? operates from +2.7 to +5.5 volt supplies ? standard resistance values: 10k w , 50k w , 100k w ? industrial operating temperature range: 40 c to + 85 c ? electronic interface provides either digital or push button control ? low cost alternative to mechanical solutions pin assignment 8pin dip 8pin soic (150 mil) 8pin m sop (118 mil) 1 2 3 4 8 6 7 8 r h v cc dc r w gnd uc str r l pin description v cc supply voltage r h high end of resistor r l low end of resistor r w wiper terminal uc up control input dc down control input str storage enable input gnd ground description the DS1809 dallastat is a nonvolatile digitally con- trolled potentiometer that provides 64 uniform wiper positions over the entire resistor range; including the highend and lowend terminals of the device. the DS1809 is a low power, low voltage device capable of operating from power supplies of +2.7v to +5.5v. the device is ideal for lowpower, portable, or battery pow- ered applications. wiper position is maintained in the absence of power. this is accomplished via the use of an eeprom cell array. the device provides for two storage methods which include an autostore capability and a com- mandinitiated storage function. the eeprom cell array is specified to accept greater than 50k writes. storage of the wiper position is discussed in the wiper storage section of this datasheet. wiper positioning is controlled via a patented dual pushbutton (or contact closure) interface. for simple pushbutton controlled applications or cpu generated control signals, external debounce circuitry is not needed. the control interface will support both repeti- tive pulse inputs and continuous pulse (apushand holdo) inputs. repetitive pulse and continuous pulse control, as well as, timing diagrams are discussed in the section entitled aoperationo. the DS1809 is available in standard 10k w , 50k w , and 100k w resistor versions. the DS1809 is provided as an industrial temperature grade part only. available pack- aging for the DS1809 include an 8lead (300 mil) dip an 8lead (150 mil) soic, and an 8lead (118 mil) m sop.
DS1809 061798 2/5 block diagram figure 1 nv memory control logic r h r l str r w uc dc operation the DS1809 dallastat is a digitally controlled nonvola- tile potentiometer. a block diagram of the DS1809 is shown in figure 1. the DS1809 is a linear potentiome- ter providing 64uniform wiper positions over the entire resistor range including the endterminals. all three potentiometer terminals of the device are accessible. these terminals include r h , r l , and r w . r h and r l are the endterminals of the potentiometer. these termi- nals will have a constant resistance between them as defined by the potentiometer value chosen: 10k w , 50k w , or the 100k w version. functionally, r h and r l are interchangeable. the wiper terminal, r w , is the mul- tiplexed terminal and can be set to one of the 64 total positions that exist on the resistor ladder including the r h and r l terminals. control of the wiper (r w ) position setting is accom- plished via the two inputs uc and dc. the uc and dc control inputs, when active, determine the direction on the resistor array that the wiper position will move. the uc (up control) control input is used to move the wiper position towards the r h terminal. the dc (down con- trol) control input is used to move wiper position towards the r l terminal. the control inputs uc and dc are active low inputs which interpret input pulse widths as the means of con- trolling wiper movement. internally, these inputs are pulledup to v cc via a 100k w resistance. a transition from a hightolow on these inputs is considered the beginning of pulse input activity. a single pulse on the uc or dc input is defined as being greater than 1 millisecond but lasting no longer that 1/2 second. this type pulse input will cause the wiper posi- tion of the dallastat to move one position. multiple pulse inputs (repetitive pulse inputs) can be used to step through each wiper position of the device. the requirement for a repetitive pulse train on the uc or dc inputs is that pulses must be separated by a mini- mum high time of 1 millisecond. if this is not the case the dallastat will ignore that pulse input. a continuous pulse input (apush and holdo) is defined as lasting longer that 1/2 second. a continuous pulse input will cause the wiper position to move one position every 100 milliseconds following the initial 1/2 second hold time. the total time to transcend the entire potentiome- ter given a continuous pulse input is provided by the equation: 1/2(second) + 62 x 100 ms = 6.7 (seconds) if the wiper position of the DS1809 is incremented to an endposition, it will stay at that position until the device receives an opposite direction input pulse command over the uc or dc inputs. for example, if the wiper position is incremented to the r h terminal using the uc input control, it will stay at that position until uc is first deactivated, and then the dc input is activated to move the wiper position towards the r l terminal. the uc and dc control inputs are designed to support simple pushbutton inputs or cpu generated inputs. figure 2 illustrates the requirements for pushbutton generated controls. for manual pushbutton controls all that is required are the desired pushbuttons to implement contact closure. no external debounce or timing circuitry is needed to support the pushbutton operation. applications using cpu generated controls must power the uc and dc control pins in a highstate to avoid any inadvertent wiper position movement. to help prevent inadvertent wiper position movement during a pow- erup, the DS1809 locks out the control port inputs for a minimum time of 10 ms. wiper storage as stated earlier, the DS1809 provides for two methods of nonvolatile wiper storage using internal eeprom memory cells. these two methods include an autostore configuration and a command initiated storage opera- tion both of which utilize the str input pin. the
DS1809 061798 3/5 eeprom cell array of the DS1809 is designed to accept greater than 50k writes. autostorage the autostore configuration is designed to provide wiper position storage as the part powersdown; writing the current wiper position into memory. the configura- tion for initiating the automatic storage capability of the DS1809 is shown in figure 3. as shown in this configu- ration two external devices are required to insure proper wiper storage. this includes a schottky diode and a 10 uf capacitor. the automatic store configuration will cause the DS1809 to initiate a storage of wiper position when power (v cc ) to the device is removed. the 10 uf capacitor and schottky diode are used to provide supplemental power for wiper storage. commandinitiated wiper storage the DS1809 will also support a commandinitiated wiper storage operation during powered conditions. for command initiated storage, the str pin should be held in a low state on powerup; otherwise the part will assume an autostore configuration. as shown in figure 5, a lowtohigh pulse lasting at least 1 m s on the str input, will cause the DS1809 to initiate the storage of the current wiper position into eeprom when v cc is pres- ent. pushbutton configuration figure 2 dc 7 2 uc gnd 5 it is assumed that the the str input will be controlled by either external logic or cpu driven. no external capaci- tors or diodes are needed for the commandinitiated storage operation. the str input will take precedence over the pushbut- ton inputs uc and dc. autostore configuration figure 3 v cc 8 3 str 10 uf cap. schottky diode pushbutton timing diagrams figure 4 continuous and single pulse inputs t ccp t pw repetitive pulse inputs t hpw t pw if during any pushbutton activity, the str input is acti- vated pushbutton operation will be suspended until the storage of eeprom has been completed. once com- plete, pushbutton inputs if still active will resume from the point of suspension. command initiated storage operations will require a minimum 4 ms to complete the storage operation. this 4 ms is measured from the rise of str input (see figure 5). for applications not requiring or using the nonvolatile memory feature of the DS1809, it is recommended that the str input be connected to gnd. command initiated wiper storage figure 5 t str
DS1809 061798 4/5 absolute maximum ratings* voltage on any pin relative to ground 1.0v to +7.0v operating temperature 40 c to +85 c; industrial storage temperature 55 c to +125 c soldering temperature 260 c for 10 seconds * this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. recommended dc operating conditions parameter symbol min typ max units notes supply voltage v cc +2.7 +5.5 v 1 resistor inputs r l , r h , r w gnd0.5 v cc +0.5 v 2 gnd gnd gnd gnd 1 dc electrical conditions parameter symbol min typ max units notes supply current active i cc 500 1000 m a 5 standby current i stby 25 m a 6 logic input high v ih +2.0 v cc +0.5 v 6, 11 logic input low v il 0.5 +0.8 +0.6 v 6, 11 input leakage i il 1 +1 m a 3 wiper resistance r wiper 400 w wiper current i w 1 ma storage pin current (str) i sp 5 8 m a 12, 18 wiper storage time t wst 4 ms 19 ac electrical conditions parameter symbol min typ max units notes single input pulse width t pw 1 dc ms 4, 5, 7, 9 repetitive pulse high time t hpw 1 dc ms 4,5,7,8,9 continuous pulse t ccp 1 dc ms 4,5,7,8,9 storage control pulse t str 1 m s 10, 12 capacitance c in 5 10 pf 10
DS1809 061798 5/5 analog resistor characteristics electrical conditions parameter symbol min typ max units notes total resistance r tot 10k, 50k, 100k w 13 endtoend resistance 20 +20 % 14 absolute linearity 0.6 +0.6 lsb 15 relative linearity 0.25 +0.25 lsb 16 3 db cutoff frequency f cutoff mhz 17 temperature coefficient 650 ppm/ c 14 notes: 1. all voltages are referenced with respect to ground. 2. voltages across the potentiometer terminals (r l ,r w ,r h ) cannot exceed v cc or go below ground by 0.5v. 3. inputs uc and dc are internally pulledup with resistance of 100k w . 4. uc and dc inputs are internally pulledup to v cc via a 100k w resistor. 5. active current is specified when the inputs uc or dc are active. 6. standby current is the current consumed when the uc, dc , and str inputs are inactive. 7. input pulse width is the minimum time required for an input to cause an increment or decrement. 8. repetitive pulse inputs on uc or dc will be recognized as long as they are within 500 milliseconds of each other. pulses occuring faster than 1 ms apart may not be recognized as individual and separate pulses. 9. input pulse timing has tolerances to 10% 10. capacitance values apply at 25 c. 11. for v cc = 5v 10% maximum v il =+0.8v. for v cc = 3.0v 10%, maximum v il =0.6v. input logic levels are refer- enced to ground. 12. if not used str should be connected to ground. 13. the DS1809 is offered in three standard values a 10k w , 50k w , and 100k w . 14. the endtoend resistance tolerance of the DS1809 can be expected to shift with temperature which is governed by the temperature coefficient specification. the endtoend resistance of the DS1809 will always remain within a 20% tolerance regardless of temperature. 15. absolute linearity is used to compare measured wiper voltage versus expected wiper voltage as determined by wiper position. the DS1809 is specified to provide a absolute linearity of 0.60 lsb. 16. relative linearity is used to determined the change in voltage between successive tap positions. the DS1809 is specified to provide a relative linearity specification of 0.25 lsb. 17. 3 db cutoff frequency characteristics for the DS1809 depend on the potentiometer's total resistance. DS1809010; 1 mhz, DS1809050; 200 khz, and the DS1809100; 100 khz. 18. current leakage on the input control storage pin will require a typical 5 and maximum 8 m a to implement the auto storage feature. 19. a minimum time of 4 milliseconds between 2.2 volts and 1.7 volts is required on the input to the str terminal when using the part in the autostorage configuration. the 2.2 volt to 1.7 volt range is a worst case condition for meeting the power down storage requirements of the part.
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