MCP6N16-001E/MF 查看數據表（PDF） - Microchip Technology

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MCP6N16-001E/MF

Zero-Drift Instrumentation Amplifier

Microchip Technology 

MCP6N16

In this data sheet, RF + RG = 10 kΩ for most gains (0Ω

for GDM = 1); see Table 1-6. This choice gives good

phase margin. In general, RF (Figure 4-13) needs to

meet the following limits to maintain stability:

EQUATION 4-13:

For GDM = 1:

RF = 0

For GDM > 1:

RF  2-------f--G---G-B---WD2----M-P---C----G--

Where:

  0.25

GDM  GMIN

fGBWP = Gain-Bandwidth Product

CG = CDM + CCM + (PCB stray capacitance)

4.4.10 EMI REJECTION RATIO (EMIRR)

Electromagnetic interference (EMI) can be coupled to

an INA through electromagnetic induction or radiation,

or by conduction. INAs are most sensitive to EMI at

their input pins.

EMIRR describes an INA’s EMI robustness. Internal

passive filters in these parts improve the EMIRR, when

good PCB layout techniques are used. EMIRR is

defined to be:

EQUATION 4-14:

Where:

EMIRRdB

=

20



log





---V--V-R---O-F--S-

VRF = Peak Input Voltage of EMI (VPK)

∆VOS = Input Offset Voltage Shift (V)

4.4.11

REDUCING UNDESIRED NOISE

AND SIGNALS

Reduce undesired noise and signals with:

• Low bandwidth signal filters:

- Minimizes random analog noise

- Reduces interfering signals

• Good PCB layout techniques:

- Minimizes crosstalk

- Minimizes parasitic capacitances and

inductances that interact with fast switching

edges

• Good power supply design:

- Isolation from other parts

- Filtering of interference on supply line(s)

4.4.12 SUPPLY BYPASS

With these INAs, the Power Supply pin (VDD for single

supply) should have a local bypass capacitor (i.e.,

0.01 µF to 0.1 µF) within 2 mm for good high-frequency

performance. Surface mount, multilayer ceramic

capacitors, or their equivalent, should be used.

These INAs require a bulk capacitor (i.e., 1.0 µF or

larger) within 100 mm to provide large, slow currents.

This bulk capacitor can be shared with other nearby

analog parts as long as crosstalk through the supplies

does not prove to be a problem.

4.4.13 PCB DESIGN FOR DC PRECISION

In order to achieve DC precision on the order of ±1 µV,

many physical errors need to be minimized. The design

of the printed circuit board (PCB), the wiring, and the

thermal environment have a strong impact on the

precision achieved. A poor PCB design can easily be

more than 100 times worse than the MCP6N16 op

amps’ minimum and maximum specifications.

4.4.13.1 PCB Layout

Any time two dissimilar metals are joined together, a

temperature dependent voltage appears across the

junction (the Seebeck or thermojunction effect). This

effect is used in thermocouples to measure

temperature. The following are examples of

thermojunctions on a PCB:

• Components (resistors, INAs, …) soldered to a

copper pad

• Wires mechanically attached to the PCB

• Jumpers

• Solder joints

• PCB vias

Typical thermojunctions have temperature to voltage

conversion coefficients of 1 to 100 µV/°C (sometimes

higher).

Microchip’s AN1258 (“Op Amp Precision Design: PCB

Layout Techniques” – DS01258) contains in-depth

information on PCB layout techniques that minimize

thermojunction effects. It also discusses other effects,

such as crosstalk, impedances, mechanical stresses

and humidity.

4.4.13.2 Crosstalk

DC crosstalk causes offsets that appear as a larger

input offset voltage. Common causes include:

• Common mode noise (remote sensors)

• Ground loops (current return paths)

• Power supply coupling

Interference from the mains (usually 50 Hz or 60 Hz),

and other AC sources, can also affect the DC

performance. Nonlinear distortion can convert these

signals to multiple tones, including a DC shift in voltage.

DS20005318A-page 44

 2014 Microchip Technology Inc.

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