この包括的なオンラインガイドは、お客様がDSM™スマートアンプソリューションを迅速に設計する上で役立ちます。このガイドの最初のセクションでは、技術の概要を説明します。マキシムのDSM技術に関する基本的な理解を促し、アイデアから設計、生産へと進むためのヒントを提示します。第2のセクションでは、DSMを実装した設計について説明します。第3の最終セクションでは、マキシムのDSM Sound Studio GUIによるMAX98390の評価システムの使用に焦点を合わせます。
DSM is optimized for use with 1W to 3W micro speakers in a sealed box enclosure.
Note: This provides the most controlled audio response and the maximum value from DSM, but usually performs just as well with bare drivers (no enclosure) as long as the front sound waves are isolated from the rear sound waves.
Sending Your Final Speaker for Laser Calibration
For a final precision laser verification test, it is highly recommended to send 3 to 5 samples of your final micro speaker + enclosure design to Maxim.
After characterization is complete, you will receive a tested parameter specification (TPS) report.
On the production line, the most important step is to calibrate RDC at a known temperature for each speaker. This is necessary to ensure that DSM’s thermal protection has an accurate reference point.
Maxim can provide assistance for measuring and setting RDC as required.
DSM Sound Studio produces a complete register map for the setup of the amplifier. The on-chip memory is volatile, so the register map must be loaded by the host for each amplifier power-up.
As mentioned in the previous section, it is also highly suggested that the final micro speaker design (including enclosure) is laser characterized by Maxim.
To increase reliability, check RDC against the expected range to filter out bad speakers. Please see the How Does DSM Improve Reliability? section for more information.
It is highly recommended that standard production testing and reliability practices are always followed.
DSM Sound Studio with the MAX98390
Getting Started with MAX98390EVSYS
What is DSM Sound Studio?
DSM Sound Studio is a complement to Maxim’s standard EV Kit GUI.
Enables a quick demo, ultra-fast speaker characterization, tuning, and easy evaluation of different speakers and different tunes.
Extract - Automated Micro Speaker Characterization and Setting Protection Limits
DSM’s thermal protection safely drives micro speakers to their specified thermal limits.
Using thermal protection, designers can ignore the specified power rating and drive speakers much more aggressively.
Voice Coil Thermal Limit (C): Determines how hot the voice coil can get before parts of the micro speaker melt.
Maxim’s DSM Smart Amplifier uses IV-sense to limit the temperature of the voice coil by monitoring the speaker impedance from the relationship outlined below.
Resistance to Temperature Correction
DSM’s Excursion Protection safely drives speakers to their specified excursion limits.
By using Excursion Protection, designers can ignore the specified resonant frequency and extend bass up to 2 octaves beyond the resonant frequency.
Excursion Limit (mm), How far the diaphragm can move before breaking.
Maxim’s speaker characterization process models the resonant frequency and Q-factor of your speaker and looks ahead at content to ensure your speaker is always protected against over-excursion.
Stereo Bass Management
Provides an even, centered bass experience for stereo systems.
When Stereo Bass Management is enabled, the lower frequencies of both channels are summed and then sent to both channels to maximize bass response while maintaining a stereo image in mid and high frequencies.
Controls for Stereo Bass Management: Enable/Disable.
Low Frequency Extension (LFX)
LFX is a feature that empowers the design to safely extend the bass response significantly below the resonant frequency.
LFX is a true bass extension algorithm. It does not use distortion components to psychoacoustically enhance bass.
Controls for LFX include: Enable/Disable, Highpass Filter, Gain, and Q.
Dynamic Range Compressor (DRC)
MAX98390 includes a Dynamic Range Compressor.
DRC attenuates loud signals and amplifies low signals. This ensures that the listener is not jarred by loud sounds like guns firing or blaring advertisements while still being able to hear softer sounds like footsteps or a quiet voice.
Controls for DRC include: Enable/Disable, Compression Ratio, Compression Threshold, Noise Gate Threshold, Attack Time, Release Time, and Makeup Gain.
8-Band Parametric EQ
MAX98390 includes 8 bands of parametric equalization.
7 filter types provided:
Controls for EQ: Enable/Disable, Filter Type, Q, Gain, Fc.
A patented feature that helps address the buzzing inherent in some speaker designs.
Audio designs will often have mechanical buzzing due to the audio output interacting with the casing or mechanical design. In these cases, engineers traditionally employ a static notch filter, but this reduces the loudness (SPL).
Maxim’s Debuzzer technology employs a programmable, dynamic notch that maximizes SPL, which only attenuates when signal levels are high enough to stimulate buzzing.
Controls for Debuzzer include: Enable/Disable, Frequency, Q, and Threshold.
Perceptual Power Reduction (PPR)
A patented algorithm that saves up to an additional 25% of power with no loss in audio fidelity.
PPR uses the human hearing response, which is much less sensitive at low frequencies, along with DSM’s knowledge of the micro speaker’s frequency response to dynamically filter inaudible content.
Threshold for PPR is tunable in Maxim’s DSM Sound Studio GUI and can be set to an even more aggressive level to save even more power.
Controls for PPR include: Enable/Disable, Threshold.