maxq3180-ran Maxim Integrated Products, Inc., maxq3180-ran Datasheet - Page 46

• Manufacturer Part Number: maxq3180-ran
• Description: Low-power, Multifunction, Polyphase Afe
• Manufacturer: Maxim Integrated Products, Inc.

These two cases cover the majority of practical situa-
tions. For higher order curves, the formulas are more
complex, and the calculations can be performed using
built-in functions of Microsoft Excel
The MathWorks, Inc.
Note that all intermediate calculations should be per-
formed with double precision, the last result rounded to
the nearest integer. Also note that PA_n are 16-bit
signed coefficients. If the calculated value exceeds 16
bits, the phase angle cannot be calibrated. In this case,
assign the largest possible value, i.e., 0x7FFF for posi-
tive overflow or 0x8000 for negative overflow.
Careful PCB layout significantly minimizes noise on the
analog inputs, resulting in less noise on the digital I/O
that could cause improper operation. The use of multi-
Low-Power, Multifunction, Polyphase AFE
Microsoft Excel is a registered trademark of Microsoft Corp.
MATLAB is a registered trademark of The MathWorks, Inc.
46
3) Repeat the phase angle error measurement
4) Calculate the coefficients (PA_n) of best fit polyno-
5) For first-order curve (requires at least two points):
______________________________________________________________________________________
c) Calculate pair of coordinates (x1,y1):
across the range.
Repeat steps 2a to 2c using other input currents
across the range. It is recommended to spread
input current points uniformly in logarithmic scale,
resulting in a set of point coordinates:
The number of points N is not limited.
mial curve.
The calculation recipe depends on the order of
polynomial.
a) For zero-order curve (requires at least one
where x_avg = average (x1,x2, . . . xN),
PA_1 = {∑ (xi-x_avg)(yi-y_avg)}/{∑ (xi-x_avg)
point):
y_avg = average (y1,y2, . . . yN)
x1 = (ln(I1_raw/2
PA_0 = average(y1,y2, . . . yN)
PA_0 = y_avg - PA_1 x x_avg
(x1,y1), (x2,y2), . . . (xN,yN)
Application Information
PA_1 = PA_2 = PA_3 = 0
y1 = (-PAerr1) x 2
PA_2 = PA_3 = 0
Grounds and Bypassing
16
) - 6.0625)/16
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or MATLAB
16
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from
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layer boards is essential to allow the use of dedicated
power planes. The area under any digital components
should be a continuous ground plane if possible. Keep
any bypass capacitor leads short for best noise rejec-
tion and place the capacitors as close to the leads of
the devices as possible.
The MAXQ3180 must have separate ground areas for
the analog (AGND) and digital (DGND) portions, con-
nected together at a single point.
CMOS design guidelines for any semiconductor require
that no pin be taken above DVDD or below DGND.
Violation of this guideline can result in a hard failure
(damage to the silicon inside the device) or a soft fail-
ure (unintentional modification of memory contents).
Voltage spikes above or below the device’s absolute
maximum ratings can potentially cause a devastating
IC latchup.
Microcontrollers commonly experience negative volt-
age spikes through either their power pins or general-
purpose I/O pins. Negative voltage spikes on power
pins are especially problematic as they directly couple
to the internal power buses. Devices such as keypads
can conduct electrostatic discharges directly into the
microcontroller and seriously damage the device.
System designers must protect components against
these transients that can corrupt system memory.
To reduce the possibility of coupling noise into the
microcontroller, the system should be designed with a
crystal or oscillator in a metal case that is grounded to
the digital plane. Doing so reduces the susceptibility of
the design to fast transient noise.
Because the MAXQ3180 is designed for use in systems
where high voltages are present, care must be taken to
route all signal paths, both analog and digital, as far
away as possible from the high-voltage components.
It is possible to construct more elaborate metering
designs using multiple MAXQ3180 devices. This can be
accomplished by using a single SPI bus to connect all
the MAXQ3180 devices together but using separate
slave select lines to individually select each MAXQ3180.
Designers must ensure they have the latest MAXQ3180
errata documents. Errata sheets contain deviations
from published specifications. A MAXQ3180 errata
sheet for any specific device revision is available at
www.maxim-ic.com/errata.
Specific Design Considerations for
MAXQ3180-Based Systems
Additional Documentation