Rainbow-electronics ADC12041 Manual de usuario descargar pdf (Pagina 7)

Notes on Specifications (Continued)

Note 6: Each input is protected by a nominal 6.5V breakdown voltage zener diode to GND, as shown below, input voltage magnitude up to 5V above V

or 5V

below GND will not damage the ADC12041. There are parasitic diodes that exist between the inputs and the power supply rails and errors in the A/D conversion

can occur if these diodes are forward biased by more than 50 mV. As an example, if V

is 4.50 V

, full-scale input voltage must be 4.55 V

to ensure accurate

conversions.

TL/H/12441–4

Note 7: V

and V

must be connected together to the same power supply voltage and bypassed with separate capacitors at each V

pin to assure

conversion/comparison accuracy. Refer to the Power Supply Considerations section for a detailed discussion.

Note 8: Accuracy is guaranteed when operating at f

CLK

12 MHz.

Note 9: With the test condition for V

REF

) given as

4.096V, the 12-bit LSB is 1.000 mV.

Note 10: Typicals are at T

C and represent most likely parametric norm.

Note 11: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 12: Positive integral linearity error is defined as the deviation of the analog value, expressed in LSBs, from the straight line that passes through positive full-

scale and zero. For negative integral linearity error, the straight line passes through negative full-scale and zero.

Note 13: Zero error is a measure of the deviation from the mid-scale voltage (a code of zero), expressed in LSB. It is the average value of the code transitions

between

1to0and0to

1 (see

Figure 6

Note 14: The DC common-mode error is measured with both inputs shorted together and driven from 0V to 5V. The measured value is referred to the resulting

output value when the inputs are driven with a 2.5V input.

Note 15: Power Supply Sensitivity is measured after an Auto-Zero and Auto Calibration cycle has been completed with V

and V

at the specified extremes.

Note 16: V

REFCM

(Reference Voltage Common Mode Range) is defined as

REF

Note 17: The ADC12041’s self-calibration technique ensures linearity and offset errors as specified, but noise inherent in the self-calibration process will result in a

repeatability uncertainty of

0.20 LSB.

Note 18: Total Unadjusted Error (TUE) includes offset, full scale linearity and MUX errors.

Note 19: The ADC12041 parts used to gather the information for these curves were auto-calibrated prior to taking the measurements at each test condition. The

auto-calibration cycle cancels any first order drifts due to test conditions. However, each measurement has a repeatability uncertainty error of 0.2 LSB. See Note

17.

Note 20: This is a DC average current drawn by the reference input with a full-scale sinewave input. The ADC12041 is continuously converting with a throughput

rate of 206 kHz.

Note 21: These typical curves were measured during continuous conversions with a positive half-scale DC input. A 240 ns RD

pulse was applied 25 ns after the

RDY

signal went low. The data bus lines were loaded with 2 HC family CMOS inputs (C

20 pF).

Note 22: Any other values placed in the command field are meaningless. However, if a code of 101 or 110 is placed in the command field and the CS

,RDand WR

go low at the same time, the ADC12041 will enter a test mode. These test modes are only to be used by the manufacturer of this device. A hardware power-off and

power-on reset must be done to get out of these test modes.

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