Electronic Components Datasheet Search |
|
AD7701 Datasheet(PDF) 9 Page - Analog Devices |
|
AD7701 Datasheet(HTML) 9 Page - Analog Devices |
9 / 16 page –9– REV. D AD7701 The output settling of the AD7701 in response to a step input change is shown in Figure 12. The Gaussian response has fast settling with no overshoot, and the worst-case settling time to ±0.0007% (±0.5 LSB) is 125 ms with a 4.096 MHz master clock frequency. 100 80 60 40 20 0 0 40 80 120 160 TIME – ms Figure 12. AD7701 Step Response USING THE AD7701 SYSTEM DESIGN CONSIDERATIONS The AD7701 operates differently from successive approxima- tion ADCs or other integrating ADCs. Since it samples the sig- nal continuously, like a tracking ADC, there is no need for a start convert command. The 16-bit output register is updated at a 4 kHz rate, and the output can be read at any time, either syn- chronously or asynchronously. CLOCKING The AD7701 requires a master clock input, which may be an external TTL/CMOS compatible clock signal applied to the CLKIN pin (CLKOUT not used). Alternatively, a crystal of the correct frequency can be connected between CLKIN and CLKOUT, when the clock circuit will function as a crystal- controlled oscillator. The input sampling frequency, output data rate, filter character- istics and calibration time are all directly related to the master clock frequency fCLKIN by the ratios given in the specification table. Therefore, the first step in system design with the AD7701 is to select a master clock frequency suitable for the bandwidth and output data rate required by the application. ANALOG INPUT RANGES The AD7701 performs conversion relative to an externally supplied reference voltage, which allows easy interfacing to ratiometric systems. In addition, either unipolar or bipolar input voltage range may be selected using the BP/UP input. With BP/ UP tied low, the input range is unipolar and the span is 0 to +VREF. With BP/UP tied high, the input range is bipolar and the span is ±V REF. In the bipolar mode both positive and negative full scale are directly determined by VREF. This offers superior tracking of positive and negative full scale and better midscale (bipolar zero) stability than bipolar schemes that simply scale and offset the input range. The digital output coding for the unipolar range is Unipolar Binary; for the bipolar range it is Offset Binary. Bit weights for the unipolar and bipolar modes are shown in Table I. The input voltages and output codes for unipolar and bipolar ranges, using the recommended +2.5 V reference, are shown in Table II. Table I. Bit Weight Table (2.5 V Reference Voltage) Unipolar Mode Bipolar Mode V LSBs % FS ppm FS LSBs % FS ppm FS 10 0.26 0.0004 4 0.13 0.0002 2 19 0.5 0.0008 8 0.26 0.0004 4 38 1.00 0.0015 15 0.5 0.0008 8 76 2.00 0.0031 31 1.00 0.0015 15 153 4.00 0.0061 61 2.00 0.0031 31 Table II. Output Coding Unipolar Mode Bipolar Mode Input Relative to Input in Volts Input Relative to Input in Volts Output Data FS and AGND FS and AGND 1111 1111 1111 1111 +VREF – 1.5 LSB +2.499943 +VREF – 1.5 LSB +2.499886 1111 1111 1111 1110 +VREF – 2.5 LSB +2.499905 +VREF – 2.5 LSB +2.499810 1111 1111 1111 1101 +VREF – 3.5 LSB +2.499867 +VREF – 3.5 LSB +2.499733 1111 1111 1111 1100 1000 0000 0000 0001 +VREF/2 + 0.5 LSB +1.250019 AGND + 0.5 LSB +0.000038 1000 0000 0000 0000 +VREF/2 – 0.5 LSB +1.249981 AGND – 0.5 LSB –0.000038 0111 1111 1111 1111 +VREF/2 – 1.5 LSB +1.249943 AGND – 1.5 LSB –0.000114 0111 1111 1111 1110 0000 0000 0000 0011 AGND + 2.5 LSB +0.000095 –VREF + 2.5 LSB –2.499810 0000 0000 0000 0010 AGND + 1.5 LSB +0.000057 –VREF + 1.5 LSB –2.499886 0000 0000 0000 0001 AGND + 0.5 LSB +0.000019 –VREF + 0.5 LSB –2.499962 0000 0000 0000 0000 NOTES 1V REF = +2.5 V 2AGND = 0 V 3Unipolar Mode, 1 LSB = 2.5 V/655536 = 0.000038 V 4Bipolar Mode, 1 LSB = 5 V/65536 = 0.000076 V 5Inputs are voltages at code transitions. |
Similar Part No. - AD7701 |
|
Similar Description - AD7701 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |