ADS1258IPHPREP datasheet(46/59 Pages) TI1

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100Ω

10 kΩ

9.09kΩ

1 0kΩ

OP A 350

OP A 365

O PA 365

AD S1258

47 Ω

10kΩ

2 .2n F

+2.5 V

+2.5V

−2.5V

+2.5V

−2.5V

+2.5V

− 2.5V

A IN 15

A IN COM

RE FP

R EF N

A IN 0

A VS S

AV D D

±10V

9.09kΩ

±10V

50Ω

A INx

20m A Input

1kΩ

+2 .5V

−2.5V

0 .1µ F

10 0µ F

0.1µ F

0.47µ F

10 µF

R EF 3125

0.1µ F

10µ F

−2.5V

0 .1µ F

1 0µ F

N OTE : 0.1µ F ca pacitors no t show n.

47Ω

ADS1258-EP

SBAS445D

– MARCH 2009 – REVISED MARCH 2011

www.ti.com

ANALOG INPUT CONNECTIONS

When using Auto-Scan mode to sequence through

the

channels,

the

switch

time

delay

feature

Figure

shows

the

ADS1258

interfacing

(programmable by registers) can be used to provide

high-level

±10V inputs, commonly used in industrial

additional settling time of the external components.

environments. In this case, bipolar power supplies are

used, avoiding the need for input signal level-shifting

Figure 69 illustrates the ADS1258 interfacing to

otherwise required when a single supply is used. The

multiple pressure sensors having a resistor bridge

input resistors serve both to reduce the level of the

output. Each sensor is excited by the 5-V single

10V input signal to within the ADC range and also

supply that also powers the ADS1258 and likewise is

protect the inputs from inadvertent signal over-voltage

used as the ADS1258 reference input; the 6% input

up to 30V. The external amplifiers convert the

overrange capability accommodates input levels at or

single-ended inputs to a fully differential output to

above VREF. The ratiometric connection provides

drive the ADC inputs. Driving the inputs differentially

cancellation of excitation voltage drift and noise. For

maintains good linearity performance. The 2.2-nF

best performance, the 5-V supply should be free from

capacitor at the ADC inputs is required to bypass the

glitches or transients. The 5-V supply input amplifiers

ADC

sampling

currents.

The

2.5-V

reference,

(two OPA365s) form a differential input/differential

REF3125, is filtered and buffered to provide a

output buffer with the gain set to 10. The chop feature

low-noise reference input to the ADC. The chop

of the ADS1258 is used to reduce offset and offset

feature of the ADC can be used to reduce offset and

drift to very low levels. The 2.2-nF capacitor at the

offset drift of the amplifiers.

ADC inputs is required to bypass the ADC sampling

currents. The 47-

Ω resistors isolate the op-amp

For

±1V input signals, the input resistor divider can

outputs from the filter capacitor.

be removed and replaced with a series protection

resistor. For 20-mA input signals, the input resistor

divider is replaced by a 50-

Ω resistor, connected from

each input to AINCOM.

Figure 68. Multichannel,

±10V Single-Ended Input, Bipolar Supply Operation

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ADS1258IPHPREP Datasheet(PDF) 46 Page - Texas Instruments

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