ADS1148IPWR datasheet(21/100 Pages) TI2

21 / 100 page

0 V

1.0 V

AINP

AINN

100 mV

VCM

0 V

1.0 V

AINP

AINN

100 mV

VCM

ADS1146, ADS1147, ADS1148

www.ti.com

SBAS453G – JULY 2009 – REVISED AUGUST 2016

Product Folder Links: ADS1146 ADS1147 ADS1148

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(1)

Input current with VCM = 2.5 V, TA = 25°C, AVDD = 5 V, and AVSS = 0 V.

Figure 23 and Figure 24 show examples of both fully-differential and pseudo-differential signals, respectively.

Figure 23. Fully-Differential Input Signal

Figure 24. Pseudo-Differential Input Signal

NOTE

With a unipolar power supply, the input range does not extend to the ground. Equation 11

and Equation 12 show the common-mode voltage requirements.

•

VCM (MIN) ≥ AVSS + 0.1 V + ½ Gain × VIN (MAX)

•

VCM (MAX) ≤ AVDD – 0.1 V – ½ Gain × VIN (MAX)

9.3.2.3 Analog Input Impedance

The device inputs are buffered through a high-input impedance PGA before they reach the ΔΣ modulator. For the

majority of applications, the input current is minimal and can be neglected. However, because the PGA is

chopper-stabilized for noise and offset performance, the input impedance is best described as a small absolute

input current. The absolute input current for selected channels is approximately proportional to the selected

modulator clock. Table 4 shows the typical values for these currents with a differential voltage coefficient and the

corresponding input impedances over data rate.

Table 4. Typical Values for Analog Input Current Over Data Rate (1)

CONDITION

ABSOLUTE INPUT CURRENT

EFFECTIVE INPUT IMPEDANCE

DR = 5 SPS, 10 SPS, 20 SPS

± (0.5 nA + 0.1 nA/V)

5000 MΩ

DR = 40 SPS, 80 SPS, 160 SPS

± (2 nA + 0.5 nA/V)

1200 MΩ

DR = 320 SPS, 640 SPS, 1 kSPS

± (4 nA + 1 nA/V)

600 MΩ

DR = 2 kSPS

± (8 nA + 2 nA/V)

300 MΩ

9.3.3 Clock Source

The device can use either the internal oscillator or an external clock. Connect the CLK pin to DGND before

power-on or reset to activate the internal oscillator. Connecting an external clock to the CLK pin at any time

deactivates the internal oscillator, with the device then operating on the external clock. After the device switches

to the external clock, it cannot be switched back to the internal oscillator without cycling the power supplies or

resetting the device.

ADS1148IPWR Datasheet(PDF) 21 Page - Texas Instruments

ADS1148IPWR Datasheet(HTML) 21 Page - Texas Instruments

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