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Maxim > Design Support > Technical Documents > Application Notes > Amplifiers > APP 5495
Maxim > Design Support > Technical Documents > Application Notes > Battery Management > APP 5495
Maxim > Design Support > Technical Documents > Application Notes > Energy Measurement & Metering > APP 5495
Keywords: battery measurement, cell stack measurement, cell balancing, battery monitoring, cell stack
monitoring, AFE, PCB
APPLICATION NOTE 5495
PCB Layout Guidelines for the MAX14921 High-
Accuracy 12-/16-Cell Measurement AFE
By: Micheal Scherrenburg
Apr 03, 2013
Abstract:
The MAX14921
analog front-end (AFE), combined with an analog-to-digital converter (ADC) and a
voltage reference, form a high-performance, cost-effective solution for battery (cell stack) measurement. To
achieve highest accuracy, care must be taken with the printed circuit board (PCB) layout. This application
note provides a few layout suggestions that, when followed, help you to achieve the highest level of accuracy
that your solution is capable of delivering.
Introduction
The MAX14921 is a high-performance building block, crucial in high-accuracy cell-stack measurement
applications. This enhanced accuracy is especially important with new lithium phosphate cell chemistries,
whose charge and discharge curves are exceptionally flat, particularly in the 65% to 95% state-of-charge
(SOC) region. The superior accuracy derives from the MAX14921's unique sample-and-hold architecture,
which minimizes both cell voltage acquisition errors and errors from sampling cells at different times.
Along with greater accuracy comes the need for greater care during design. This application note describes
some simple, yet effective, layout guidelines to help you realize the benefits of this enhanced accuracy.
Mitigating Noise
The following noise-related guidelines are well known by those practiced in the art of modern PCB layout, so
these are more reminders of those layout aspects most critical to noise management particular to the
MAX14921.
Bypass Capacitors
It is well known that bypass capacitors are important circuit elements, good for filtering noise before it makes
its way into an integrated circuit (IC). For greatest effectiveness, it is important to place the bypass capacitors
as close to their IC power pins as is reasonable. Table 1 details the MAX14921's bypass capacitor
requirements.
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