Datasheet CMX655A, CMX655D (CML Microcircuits) - 2

Ultra-Low Power Voice Codec CMX655D/CMX655A
1 Brief Description
Traditionally audio codecs have interfaced to electret microphones and speakers providing A-to-D and D-to-A functions using precision oversampling data converters. Recent advances in microphone design using MEMS techniques are now changing this, along with higher efficiency speaker drivers such as Class-D topologies. Both of these advances enable significant reductions in power consumption which is needed to address new applications such as voice control, that require ‘always-on’ operation. Such applications are often battery powered, driving the need for minimal power consumption. The CMX655D and CMX655A address these needs providing an update to the traditional audio codec that is both very low power and small in size. The CMX655D has a digital microphone interface that connects single or dual microphones to the device and the same parallel processing streams. The CMX655A has two independent input channels that support analogue microphones, with parallel processing of each data stream to maintain phase alignment between the two channels. The device supports programmable on-chip filtering, with digital gain control and an AGC function. A 1-Watt mono Class-D amplifier drives differential audio outputs for a filterless speaker. A separate single-ended analogue lineout is also provided for a headphone. The Class-D amplifier features programmable filtering and digital gain control. This architecture operates with far higher efficiency than conventional speaker drivers. The device interfaces via standard serial busses that are commonly found on many microcontrollers, DSPs and low cost radio transceivers. Note that text shown in pale grey indicates features that will be available in future versions of the device.  2018 CML Microsystems Plc 2 D/655/3 Document Outline Datasheet Front Page 1 Brief Description 2 Block Diagram 2.1 CMX655A 2.2 CMX655D 3 Pin List 3.1 CMX655A 3.2 CMX655D 4 External Components 4.1 CMX655A 4.1.1 Power Supply and Pin Decoupling 4.1.2 SPI 4.1.3 TWI 4.1.4 Speaker and Microphone 4.2 CMX655D 4.2.1 Power Supply and Pin Decoupling 4.2.2 SPI 4.2.3 TWI 4.2.4 Speaker and Microphone 5 General Description 5.1 Power Management 5.1.1 External Supplies 5.1.2 Regulated Supplies 5.2 Device Reset 5.2.1 Power-On-Reset 5.2.2 Reset Pin 5.3 Main Clock 5.3.1 Clock Frequency 5.3.2 Clock Generation 5.3.3 PLL 5.3.4 Low Power Oscillator 5.3.5 Clock Control Registers 5.3.5.1 CLKCTRL ($03) 5.3.5.2 RDIVHI ($04) 5.3.5.3 RDIVLO ($05) 5.3.5.4 NDIVHI ($06) 5.3.5.5 NDIVLO ($07) 5.3.5.6 PLLCTRL ($08) 5.4 Microphone Interface 5.4.1 Digital Microphone Interface 5.4.2 Analogue Microphone Interface 5.5 Class-D Amplifier 5.5.1 Audio Outputs 5.5.2 Overload Current Protection 5.5.3 Thermal Protection 5.5.4 Clipping Detection 5.6 Audio Signal Processing 5.6.1 Record Level Control 5.6.1.1 Record Level Control Register 5.6.2 Automatic Gain Control 5.6.2.1 AGC Registers 5.6.3 Noise Gate 5.6.3.1 Noise Gate Registers 5.6.4 Record Level Detection 5.6.4.1 Record Level Detection Registers 5.6.5 Playback Preamplifier Gain 5.6.5.1 Playback Preamplifier Gain Register 5.6.6 Playback Volume Control 5.6.6.1 Playback Volume Register 5.6.7 Automatic Level Control 5.6.7.1 ALC Registers 5.6.8 Digital Sidetone 5.6.8.1 Digital Sidetone Register 5.6.9 Voice Filters 5.6.9.1 Low Pass Filter 5.6.9.2 DC Blocking Filter 5.6.9.3 High Pass Filter 5.6.9.4 Voice Filters Registers 5.6.10 Channel Multiplexing 5.6.11 Click-and-Pop Reduction 5.6.11.1 Click-and-Pop Reduction Register 5.7 Control Interface 5.7.1 SPI Slave 5.7.2 TWI Slave 5.8 Serial Audio Interface 5.8.1 I2S Mode 5.8.2 Left-Justified Mode 5.8.3 PCM Mode 5.8.4 Audio Companding 5.8.5 Serial Audio Interface Registers 5.9 Interrupt Status and IRQN Pin 5.9.1 Interrupt Registers 5.10 System Control 5.10.1 System Control Registers 5.11 Register Address Map 6 Application Notes 6.1 Programming Examples 6.1.1 Start-up 6.1.2 DC-offset Calibration 6.1.3 Configuration 6.1.4 Enable Audio Channels 6.1.5 Shutdown 7 Performance Specification 7.1 Electrical Performance 7.1.1 Absolute Maximum Ratings 7.1.2 Operating Limits 7.1.3 Operating Characteristics 7.1.3.1 DC Parameters 7.1.3.2 AC Parameters 7.1.3.3 SPI 7.1.3.4 TWI 7.1.3.5 SAI 7.1.3.6 Digital Microphone Interface 7.2 Typical Performance Characteristics 7.2.1 THD+N vs. Level performance 7.2.2 THD+N vs. Frequency performance 7.2.3 Class D Amplifier Efficiency 7.2.4 Filter Performance Speaker Channel 7.2.5 Filter Performance Microphone Channel 7.3 Packaging 7.3.1 CMX655D/CMX655A End of Document