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AD5231BRU100-REEL7 数据表(PDF) 10 Page - Analog Devices |
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AD5231BRU100-REEL7 数据表(HTML) 10 Page - Analog Devices |
10 / 24 page REV. 0 AD5231 –10– OPERATIONAL OVERVIEW The AD5231 digital potentiometer is designed to operate as a true variable resistor replacement device for analog signals that remain within the terminal voltage range of VSS < VTERM < VDD. The basic voltage range is limited to a |VDD – VSS| < 5.5 V. The digital potentiometer wiper position is determined by the RDAC register contents. The RDAC register acts as a scratch pad regis- ter allowing as many value changes as necessary to place the potentiometer wiper in the correct position. The scratch pad register can be programmed with any position value using the standard SPI serial interface mode by loading the complete repre- sentative data word. Once a desirable position is found this value can be saved into an EEMEM register. Thereafter the wiper position will always be set at that position for any future ON- OFF-ON power supply sequence. The EEMEM save process takes approximately 25 ms, during this time the shift register is locked preventing any changes from taking place. The RDY pin indicates the completion of this EEMEM save. There are 16 instructions that facilitate users’ programming needs. Refer to Table III. The instructions are: 1. Do Nothing 2. Restore EEMEM Setting to RDAC 3. Save RDAC Setting to EEMEM 4. Save RDAC Setting or User Data to EEMEM 5. Decrement 6 dB 6. Decrement 6 dB 7. Decrement One Step 8. Decrement One Step 9. Reset EEMEM setting to RDAC 10. Read EEMEM to SDO 11. Read Wiper Setting to SDO 12. Write Data to RDAC 13. Increment 6 dB 14. Increment 6 dB 15. Increment One Step 16. Increment One Step Scratch Pad and EEMEM Programming The scratch pad register (RDAC register) directly controls the position of the digital potentiometer wiper. When the scratch pad register is loaded with all zeros, the wiper will be connected to the B-Terminal of the variable resistor. When the scratch pad register is loaded with midscale code (1/2 of full-scale position), the wiper will be connected to the middle of the variable resistor. And when the scratch pad is loaded with full-scale code, all ones, the wiper will connect to the A-Terminal. Since the scratch pad register is a standard logic register, there is no restriction on the number of changes allowed. The EEMEM registers have a program erase/write cycle limitation described in the Flash/EEMEM Reliability section. Basic Operation The basic mode of setting the variable resistor wiper position (programming the scratch pad register) is accomplished by loading the serial data input register with the command instruc- tion #11, which includes the desired wiper position data. When the desired wiper position is found, the user would load the serial data input register with the command instruction #2, which makes a copy of the desired wiper position data into the nonvolatile EEMEM register. After 25 ms the wiper position will be permanently stored in the nonvolatile EEMEM location. Table I provides an application-programming example listing the sequence of serial data input (SDI) words and the serial data output appearing at the SDO Pin in hexadecimal format. Table I. Set and Save RDAC Data to EEMEM Register SDI SDO Action B00100H XXXXXXH Loads data 100H into RDAC register, Wiper W moves to 1/4 full-scale position. 20XXXXH B00100H Saves copy of RDAC register contents into EEMEM register. At system power ON, the scratch pad register is automatically refreshed with the value last saved in the EEMEM register. The factory preset EEMEM value is midscale but thereafter, the EEMEM value can be changed by user. CS CLK SDI IDD* 2mA/DIV 5V/DIV 5V/DIV 5V/DIV * SUPPLY CURRENT RETURNS TO MINIMUM POWER CONSUMPTION IF INSTRUCTION #0 (NOP) IS EXECUTED IMMEDIATELY AFTER INSTRUCTION #1 (READ EEMEM) 4ms/DIV TPC 19. IDD vs. Time (Read) Program Mode CODE – Decimal 100 1 0.01 1024 0.1 10 RAB = 10k RAB = 50k RAB = 100k 896 768 640 512 384 128 256 0 VA = VB = OPEN TA = 25 C TPC 20. IWB_MAX vs. Code |
类似零件编号 - AD5231BRU100-REEL7 |
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类似说明 - AD5231BRU100-REEL7 |
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