VDD

GND

AIN0

VDD

GND

AIN1

VDD

GND

AIN2

VDD

GND

AIN3

AIN

P

AIN

N

GND

Device

ADS1118

www.ti.com

SBAS457A

– OCTOBER 2010 – REVISED JULY 2011

MULTIPLEXER

The ADS1118 contains an input multiplexer, as shown in Figure 33. Either four single-ended or two differential

signals can be measured. Additionally, AIN0 and AIN1 may be measured differentially to AIN3. The multiplexer is

configured by three bits in the Config Register. When single-ended signals are measured, the negative input of

the ADC is internally connected to GND by a switch within the multiplexer.

Figure 33. ADS1118 MUX

When measuring single-ended inputs, it is important to note that the negative range of the output codes are not

discharge (ESD) diodes to VDD and GND protect the inputs. To prevent the ESD diodes from turning on, the

absolute voltage on any input must stay within the range of Equation 1:

GND

– 0.3V < AINx < VDD + 0.3V

(1)

If it is possible that the voltages on the input pins may violate these conditions, external Schottky clamp diodes

and/or series resistors may be required to limit the input current to safe values (see the Absolute Maximum

Ratings table). While the analog inputs can support signals marginally above supply, under no circumstances

should any analog or digital input or output be driven to greater than 5.5V with respect to the GND pin.

Also, overdriving one unused input on the ADS1118 may affect conversions taking place on other input pins. If

overdrive on unused inputs is possible, it is recommended to clamp the signal with external Schottky diodes.

Copyright

© 2010–2011, Texas Instruments Incorporated

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