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AD5253BRU1-RL7 Fiches technique(PDF) 22 Page - Analog Devices |
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AD5253BRU1-RL7 Fiches technique(HTML) 22 Page - Analog Devices |
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22 / 32 page  AD5253/AD5254 Data Sheet Rev. C | Page 22 of 32 DIGITAL INPUT/OUTPUT CONFIGURATION SDA is a digital input/output with an open-drain MOSFET that requires a pull-up resistor for proper communication. On the other hand, SCL and WP are digital inputs for which pull-up resistors are recommended to minimize the MOSFET cross- conduction current when the driving signals are lower than VDD. SCL and WP have ESD protection diodes, as shown in Figure 35 and Figure 36. WP can be permanently tied to VDD without a pull-up resistor if the write-protect feature is not used. If WP is left floating, an internal current source pulls it low to enable write protection. In applications in which the device is programmed infrequently, this allows the part to default to write-protection mode after any one-time factory programming or field calibration without using an on-board pull-down resistor. Because there are protection diodes on all inputs, the signal levels must not be greater than VDD to prevent forward biasing of the diodes. GND SCL VDD Figure 35. SCL Digital Input GND INPUTS WP VDD Figure 36. Equivalent WP Digital Input MULTIPLE DEVICES ON ONE BUS The AD5253/AD5254 are equipped with two addressing pins, AD1 and AD0, that allow up to four AD5253/AD5254 devices to be operated on one I2C bus. To achieve this result, the states of AD1 and AD0 on each device must first be defined. An example is shown in Table 12 and Figure 37. In I2C programming, each device is issued a different slave address—01011(AD1)(AD0)— to complete the addressing. Table 12. Multiple Devices Addressing AD1 AD0 Device Addressed 0 0 U1 0 1 U2 1 0 U3 1 1 U4 SDA SDA AD1 AD0 MASTER SCL SCL SDA AD1 AD0 SCL SDA AD1 AD0 SCL SDA 5V RP RP 5V 5V 5V AD1 AD0 SCL AD5253/ AD5254 AD5253/ AD5254 AD5253/ AD5254 AD5253/ AD5254 Figure 37. Multiple AD5253/AD5254 Devices on a Single Bus In wireless base station smart-antenna systems that require arrays of digital potentiometers to bias the power amplifiers, large numbers of AD5253/AD5254 devices can be addressed by using extra decoders, switches, and I/O buses, as shown in Figure 38. For example, to communicate to a total of 16 devices, four decoders and 16 sets of combinational switches (four sets shown in Figure 38) are needed. Two I/O buses serve as the common inputs of the four 2 × 4 decoders and select four sets of outputs at each combination. Because the four sets of combination switch outputs are unique, as shown in Figure 38, a specific device is addressed by properly programming the I2C with the slave address defined as 01011(AD1)(AD0). This operation allows one of 16 devices to be addressed, provided that the inputs of the two decoders do not change states. The inputs of the decoders are allowed to change once the operation of the specified device is completed. |
Numéro de pièce similaire - AD5253BRU1-RL7 |
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Description similaire - AD5253BRU1-RL7 |
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