LMV854EVAL National Semiconductor, LMV854EVAL Datasheet - Page 14

• Manufacturer Part Number: LMV854EVAL
• Description: BOARD EVALUATION LMV854 8MHZ
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LMV854EVAL

• Channels Per Ic: 4 - Quad
• Amplifier Type: General Purpose
• Output Type: Single-Ended, Rail-to-Rail
• Slew Rate: 4.5 V/µs
• Current - Output / Channel: 65mA
• Operating Temperature: -40°C ~ 125°C
• Current - Supply (main Ic): 1.59mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 5.5 V, ±1.35 V ~ 2.75 V
• Board Type: Fully Populated
• Utilized Ic / Part: LMV854
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• -3db Bandwidth: -

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Application Information
INTRODUCTION
The LMV851/LMV852/LMV854 are operational amplifiers
with very good specifications, such as low offset, low noise
and a rail-to-rail output. These specifications make the
LMV851/LMV852/LMV854 great choices to use in areas such
as medical and instrumentation. The low supply current is
perfect for battery powered equipment. The small packages,
SC-70 package for the LMV851, the MSOP package for the
dual LMV852 and the TSSOP package for the quad LMV854,
make any of these parts a perfect choice for portable elec-
tronics. Additionally, the EMI hardening makes the LMV851/
LMV852 or LMV854 a must for almost all op amp applications.
Most applications are exposed to Radio Frequency (RF) sig-
nals such as the signals transmitted by mobile phones or
wireless computer peripherals. The LMV851/LMV852/
LMV854 will effectively reduce disturbances caused by RF
signals to a level that will be hardly noticeable. This again
reduces the need for additional filtering and shielding. Using
this EMI resistant series of op amps will thus reduce the num-
ber of components and space needed for applications that are
affected by EMI, and will help applications, not yet identified
as possible EMI sensitive, to be more robust for EMI.
INPUT CHARACTERISTICS
The input common mode voltage range of the LMV851/
LMV852/LMV854 includes ground, and can even sense well
below ground. The CMRR level does not degrade for input
levels up to 1.2V below the supply voltage. For a supply volt-
age of 5V, the maximum voltage that should be applied to the
input for best CMRR performance is thus 3.8V.
When not configured as unity gain, this input limitation will
usually not degrade the effective signal range. The output is
rail-to-rail and therefore will introduce no limitations to the
signal range.
The typical offset is only 0.26 mV, and the TCV
0.4 μV/°C, specifications close to precision op amps.
CMRR MEASUREMENT
The CMRR measurement results may need some clarifica-
tion. This is because different setups are used to measure the
AC CMRR and the DC CMRR.
The DC CMRR is derived from ΔV
is stated in the tables, and is tested during production testing.
The AC CMRR is measured with the test circuit shown in
Figure 1.
OS
versus ΔV
CM
. This value
OS
is
14
The configuration is largely the usually applied balanced con-
figuration. With potentiometer P1, the balance can be tuned
to compensate for the DC offset in the DUT. The main differ-
ence is the addition of the buffer. This buffer prevents the
open-loop output impedance of the DUT from affecting the
balance of the feedback network. Now the closed-loop output
impedance of the buffer is a part of the balance. But as the
closed-loop output impedance is much lower, and by careful
selection of the buffer also has a larger bandwidth, the total
effect is that the CMRR of the DUT can be measured much
more accurately. The differences are apparent in the larger
measured bandwidth of the AC CMRR.
One artifact from this test circuit is that the low frequency CM-
RR results appear higher than expected. This is because in
the AC CMRR test circuit the potentiometer is used to com-
pensate for the DC mismatches. So, mainly AC mismatch is
all that remains. Therefore, the obtained DC CMRR from this
AC CMRR test circuit tends to be higher than the actual DC
CMRR based on DC measurements.
The CMRR curve in Figure 2 shows a combination of the AC
CMRR and the DC CMRR.
FIGURE 1. AC CMRR Measurement Setup
FIGURE 2. CMRR Curve
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