## page was renamed from Lecture 11
= Sigma-Delta PWM for class-D audio and other Sigma-delta tricks =

== Additional Material ==

 * [[https://people.ee.ethz.ch/~haschmid/asf/11/33mW_2_5MS_SD_ADC__reutemann02.pdf|Reutemann et. al. (decimation filter)]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/33mW_2_5MS_SD_ADC_slides__reutemann02.pdf|... and the slides presented at the conference]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/cic_filters__hogenauer81.pdf|Hogenauer's original CIC filter paper]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/2009esscirc.pdf|Pastre, Schmid et. al. on a sigma-delta accelerometer]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/audio_classD_fundamentals__jiang17.pdf|Jiang on class-D audio (fundamentals)]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/classD_audio_mobile__berkhout10.pdf|Berkhout on class-D audio (more details)]]

== The Balloon (Holiday Special) ==

Spoiler Alert! It is better if you do '''not''' look at this before the lecture.

 * [[https://people.ee.ethz.ch/~haschmid/asf/2018_12_asf.zip|Exploding-Ballon Room Impulse Response Demo]]

== Exercise ==

 * [[https://people.ee.ethz.ch/~haschmid/asf/11/asf_ex11_applications.pdf|Exercise 11]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/asf_ex11_app_ref.pdf|Exercise 11 reference solution]]

== Matlab Exercise ==

 * [[https://people.ee.ethz.ch/~haschmid/asf/11/asf_ex11.zip|asf_ex11.zip]]
 * [[https://people.ee.ethz.ch/~haschmid/asf/11/asf_ex11_ref.zip|Reference Solution]]

The target is to build a driver for the TAS5602 by Texas Instruments.  This chip expects a pulse-width modulated signal with at most 400kHz base frequency.  We have an FPGA with a maximum clock frequency of 50 MHz.  So what we need to do is to drive the digital PWM generator with a sigma-delta bitstream.

How to proceed:
 1. Understand the 8-bit (256-step) pulse width modulator (pwmstage.mdl, go_pwmstage_00.m)
 1. Replace the comparator in the sigma-delta converter by a 256-step quantizer (example: sd2multibit.mdl, go_sd2multibit_00.m)
 1. Combine both and optimize SNR
 1. If you want, feed audio through your solution.

== Learning Targets formulated in 2009 ==

 * How a MASH converter works in principle 
 * How a low-distortion converter works (signal bypassing the loop filter)
 * How a converter with noise coupling works
 * PWM stage driven by a sigma-delta bitstream

(compiled by Hanspeter Schmid)