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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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LP3952 Datenblatt(PDF) 18 Page - Texas Instruments |
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LP3952 Datenblatt(HTML) 18 Page - Texas Instruments |
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18 / 46 page  ASE BUFFER ADC DC REMOVER AGC GAIN EN 3 FILTERS PEAK DETECTOR MODE LUT LUT INT PW M LED DRIVER R B G HIGH / LOW SPEED LP3952 SNVS518A – JULY 2007 – REVISED MARCH 2013 www.ti.com analog audio input. Because a low-order low-pass filter attenuates the high-frequency components from audio signal, MODE_CTRL=01b selection is recommended when frequency synchronization mode is enabled. Application example 5 shows an example of a second order RC-filter for 29 kHz PWM signal with 3.3V amplitude. Active filters, such as a Sallen-Key filter, may also be applied. An active filter gives better stop-band attenuation and cut-off frequency can be higher than for a RC-filter. To make sure that the filter rolls off sufficiently quickly, connect your filter circuit to the audio input(s), turn on the audio synchronization feature, set manual gain to maximum, apply the PWM signal to the filter input and keep an eye on LEDs. If they are blinking without an audio signal (modulation), a sharper roll-off after the cut-off frequency, more stop-band attenuation, or smaller amplitude of the PWM signal is required. AUDIO SYNCHRONIZATION SIGNAL PATH (1.65V ≤ VDDIO ≤ VDD1,2V) (unless otherwise noted) LP3952 audio synchronization is mainly done digitally and it consists of the following signal path blocks: • Input Buffers • AD Converter • DC Remover • Automatic Gain Control (AGC) • Programmable Gain • 3 Band Digital Filter • Peak Detector • Look-up Tables (LUT) • Mode Selector • Integrators • PWM Generator • Output Drivers The digitized input signal has DC component that is removed by digital DC REMOVER (-3 dB @ 400 Hz). Since the light response of input audio signal is very much amplitude dependent the AGC adjusts the input signal to suitable range automatically. User can disable AGC and the gain can be set manually with PROGRAMMABLE GAIN. LP3952 has 2 audio synchronization modes: amplitude and frequency. For amplitude based synchronization the PEAK DETECTION method is used. For frequency based synchronization 3 BAND FILTER separates high pass, low pass and band bass signals. For both modes the predefined LUT is used to optimize the audio visual effect. MODE SELECTOR selects the synchronization mode. Different response times to music beat can be selected using INTEGRATOR speed variables. Finally PWM GENERATOR sets the driver FET duty cycles. INPUT SIGNAL TYPE AND BUFFERING (1.65V ≤ VDDIO ≤ VDD1,2V) (unless otherwise noted) LP3952 supports single ended audio input as shown in the figure below. The electric parameters of the buffer are described in the Audio Synch table. The buffer is rail-to-rail input operational amplifier connected as a voltage follower. DC level of the input signal is set by a simple resistor divider 18 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Product Folder Links: LP3952 |
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