VIN

+

VOUT

R1

Vcc

Current-limiting resistor

required if input voltage

exceeds supply rails by

• 0.3 V.

10 mA max

13

LPV821

www.ti.com

SNOSD36A – AUGUST 2017 – REVISED DECEMBER 2017

Product Folder Links: LPV821

Submit Documentation Feedback

Copyright © 2017, Texas Instruments Incorporated

Feature Description (continued)

8.3.2 Input

The LPV821 input common-mode voltage range extends to the supply rails. Typically, the input bias current is

approximately 7 pA; however, input voltages that exceed the power supplies can cause excessive current to flow

into or out of the input pins. Momentary voltages greater than the power supply can be tolerated if the input

current is limited to 10 mA. This limitation is easily accomplished with adding a resistor in series with the input,

as shown in Figure 37.

Figure 37. Input Current Protection

8.3.3 Internal Offset Correction

The LPV821 operational amplifier combines an auto-calibration technique with a time-continuous 8-kHz

operational amplifier in the signal path. The amplifier's offset is zero-corrected every 1 ms using a proprietary

technique. This design has no aliasing or flicker (1/f) noise.

8.3.4 Input Offset Voltage Drift

The LPV821 operational amplifier's input voltage offset drift is defined over the entire temperature range of

–40°C to 125°C. The maximum input voltage drift allows designers to calculate the worst-case input offset

change over this temperature range. The maximum input voltage drift over temperature is defined using

Equation 1:

dVOS/dT = ΔVOS / ΔT

where

•

ΔVOS = Change in input offset voltage

•

ΔT = Change in temperature (125°C - (-40°C) = 165°C)

•

dVOS/dT = Input offset voltage drift

(1)

The LPV821 datasheet maximum value for input offset voltage drift is specified for a sample size with a Cpk

(process capability index) of 2.0.

8.4 Device Functional Modes

The LPV821 has a single functional mode. The device is powered on as long as the power supply voltage is

between 1.7 V (±0.85 V) and 3.6 V (±1.8 V).

8.4.1 EMI Performance and Input Filtering

Operational amplifiers vary in susceptibility to EMI. If conducted EMI enters the operational amplifier, the dc

offset at the amplifier output can shift from its nominal value when EMI is present. This shift is a result of signal

rectification associated with the internal semiconductor junctions. Although all operational amplifier pin functions

can be affected by EMI, the input pins are likely to be the most susceptible. The LPV821 operational amplifier

incorporates an internal input low-pass filter that reduces the amplifier response to EMI. Both common mode and

differential-mode filtering are provided by the input filter.