Rainbow-electronics MAX1314 Bedienungsanleitung PDF herunterladen (Seite 28)

MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–MAX1314

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs

with ±10V, ±5V, and 0 to +5V Analog Input Ranges

28 ______________________________________________________________________________________

Bipolar ±5V Devices

Table 6 and Figure 13 show the two’s complement trans-

fer function for the ±5V input range MAX1308/MAX1309/

MAX1310. The FSR is four times the voltage at REF. The

internal +2.5V reference gives a +10V FSR, while an

external +2V to +3V reference allows an FSR of +8V to

+12V respectively. Calculate the LSB size using:

which equals 2.44mV when using a 2.5V reference.

The input range is centered about V

MSV

. Normally,

MSV = AGND, and the input is symmetrical about zero.

For a custom midscale voltage, drive MSV with an

external voltage source. Noise present on MSV directly

couples into the ADC result. Use a precision, low-drift

voltage reference with adequate bypassing to prevent

MSV from degrading ADC performance. For maximum

FSR, do not violate the absolute maximum voltage rat-

ings of the analog inputs when choosing MSV.

Determine the input voltage as a function of V

REF

MSV

, and the output code in decimal using:

CH_

= LSB x CODE

+ V

MSV

LSB

REF

Table 6. ±5V Bipolar Code Table

TWO’s

COMPLEMENT

DIGITAL OUTPUT

CODE

DECIMAL

EQUIVALENT

DIGITAL OUTPUT

CODE

(CODE

)

INPUT VOLTAGE

(V)

REF

= +2.5V

MSV

= 0

0111 1111 1111 =

0x7FF

+2047

+4.9988 ± 0.5 LSB

0111 1111 1110 =

0x7FE

+2046

+4.9963 ± 0.5 LSB

0000 0000 0001 =

0x001

+0.0037 ± 0.5 LSB

0000 0000 0000 =

0x000

+0.0012 ± 0.5 LSB

1111 1111 1111 =

0xFFF

-1

-0.0012 ± 0.5 LSB

1000 0000 0001 =

0x801

-2047

-4.9963 ± 0.5 LSB

1000 0000 0000 =

0x800

-2048

-4.9988 ± 0.5 LSB

(

)

4 x V

REF

4 x V

REF

1 LSB =

TWO'S COMPLEMENT BINARY OUTPUT CODE

-2048 -2046 +2047+2045

0x800

0x801

0x802

0x803

0x7FF

0x7FE

0x7FD

0x7FC

0xFFF

0x000

0x001

-1 0 +1

(MSV)

INPUT VOLTAGE (V

CH_

- V

MSV

IN LSBs)

Figure 13. ±5V Bipolar Transfer Function

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Kommentare zu diesen Handbüchern

Keine Kommentare

Rainbow-electronics MAX1314 Bedienungsanleitung Seite 28

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Sensoren Rainbow-electronics MAX1314