ADS1148IPW datasheet(16/50 Pages) TI

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REFN1

REFP1

ADC

ADS1148 Only

REFN0

REFP0

REFN

REFP

VREFCOM

VREFOUT

ReferenceMultiplexer

Internal

Voltage

Reference

ADS1146

ADS1147

ADS1148

SBAS453C – JULY 2009 – REVISED APRIL 2010

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ESD diodes protect the ADC inputs. To prevent these

As with the analog inputs, REFP0 and REFN0 can be

diodes from turning on, make sure the voltages on

configured as digital I/Os on the ADS1147 and

the input pins do not go below AVSS by more than

ADS1148.

100mV, and do not exceed AVDD by more than

100mV, as shown in Equation 2. Note that the same

caution is true if the inputs are configured to be

GPIOs.

AVSS – 100mV < (AINX) < AVDD + 100mV

(2)

Settling Time for Channel Multiplexing

The ADS1146/7/8 is a true single-cycle settling

ΔΣ

converter. The first data available after the start of a

conversion are fully settled and valid for use. The

time required to settle is roughly equal to the inverse

of the data rate. The exact time depends on the

specific data rate and the operation that resulted in

the start of a conversion; see Table 15 for specific

values.

Figure 12. Reference Input Multiplexer

VOLTAGE REFERENCE INPUT

The reference input circuit has ESD diodes to protect

The voltage reference for the ADS1146/7/8 is the

the inputs. To prevent the diodes from turning on,

differential voltage between REFP and REFN:

make sure the voltage on the reference input pin is

VREF = VREFP – VREFN

not less than AVSS – 100mV, and does not exceed

AVDD + 100mV, as shown in Equation 3:

In the case of the ADS1146, these pins are dedicated

inputs. For the ADS1147 and ADS1148, there is a

AVSS – 100mV < (VREFP or VREFN) < AVDD + 100mV

(3)

multiplexer that selects the reference inputs, as

shown in Figure 12. The reference input uses a buffer

to increase the input impedance.

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