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AD5025BRUZ-REEL7 Fiches technique(PDF) 31 Page - Analog Devices |
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AD5025BRUZ-REEL7 Fiches technique(HTML) 31 Page - Analog Devices |
31 / 33 page Preliminary Technical Data AD5025/45/65 APPLICATIONS USING A REFERENCE AS A POWER SUPPLY FOR This is an output voltage range of ±5 V, with 0x0000 corre- THE AD5025/45/65 sponding to a −5 V output, and 0xFFFF corresponding to a Because the supply current required by the AD5025/45/65 is +5 V output. extremely low, an alternative option is to use a voltage reference R2 = 10kΩ +5V –5V AD820/ OP295 AD5025/45/65 VDD VOUT R1 = 10kΩ ±5V 0.1µF 10µF to supply the required voltage to the parts (see Figure 52). This is especially useful if the power supply is quite noisy or if the +5V system supply voltages are at some value other than 5 V or 3 V, for example, 15 V. The voltage reference outputs a steady supply voltage for the AD5025, AD5045 and AD5065. If the low dropout REF195 is used, it must supply 500 μA of current to the AD5025/ AD5045 / AD5065, with no load on the output of the DAC. When the DAC output is loaded, the REF195 also needs to supply the current to the load. The total current required (with a 5 kΩ load on the DAC output) is THREE-WIRE SERIAL INTERFACE 500 μA + (5 V/5 kΩ) = 1.5 mA Figure 53. Bipolar Operation with the AD5025/45/65 The load regulation of the REF195 is typically 2 ppm/mA, USING THE AD5025/45/65 WITH A which results in a 3 ppm (15 μV) error for the 1.5 mA current GALVANICALLY ISOLATED INTERFACE drawn from it. This corresponds to a 0.196 LSB error. In process control applications in industrial environments, it is often necessary to use a galvanically isolated interface to protect and isolate the controlling circuitry from any hazardous common-mode voltages that can occur in the area where the DAC is functioning. iCoupler® provides isolation in excess of 2.5 kV. The AD5025/45/65 uses a 3-wire serial logic interface, so the ADuM1300 three-channel digital isolator provides the required isolation (see Figure 54). The power supply to the part AD5065/ AD5045/ AD5025 THREE-WIRE SERIAL INTERFACE SYNC SCLK DIN 15V 5V VOUT =0VTO 5V VDD REF195 also needs to be isolated, which is done by using a transformer. On the DAC side of the transformer, a 5 V regulator provides the 5 V supply required for the AD5025/45/65. Figure 52. REF195 as Power Supply to the AD5025/45/65 BIPOLAR OPERATION USING THE AD5025/45/65 The AD5025/45/65 has been designed for single-supply operation, but a bipolar output range is also possible using the circuit in Figure 53. The circuit gives an output voltage range of ±5 V. Rail-to-rail operation at the amplifier output is achievable 0.1µF 5V REGULATOR GND DIN SYNC SCLK POWER 10µF AD5025/45/65 VOUT VOB VOA VOC VDD VIC VIB VIA ADuM1300 using an AD820 or an OP295 as the output amplifier. SCLK The output voltage for any input code can be calculated as follows: SDI ⎡ ⎢ ⎣ V DD ⎤ ⎛ ⎜ ⎝ D ⎞ ⎟ ⎠ R1 + R2 R2 ⎛ ⎜ ⎝ ⎞ ⎟ ⎠ ⎛ ⎜ ⎝ ⎞ ⎟ ⎠ − V O V DD × × × = where D represents the input code in decimal (0 to 65,535). With VDD = 5 V, R1 = R2 = 10 kΩ, ⎥ ⎦ 65,536 R1 R1 DATA Figure 54. AD5025/45/65 with a Galvanically Isolated Interface ⎛ ⎜ ⎝ = 10 × D ⎞ ⎟ ⎠ V O − 5 V 65,536 Rev. PrB | Page 31 of 3 3 |
Numéro de pièce similaire - AD5025BRUZ-REEL7 |
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Description similaire - AD5025BRUZ-REEL7 |
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