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TLV320AIC3256: Both input IN1 & IN2 will make noise issue?

Ray Hsu
Expert 1330 points

Part Number: TLV320AIC3256

Channel 1 is MIC input. SE in. external MIC bias. 

Channel 2 is BT speaker. Diff. in.

below is my register table, please help me check any wrong?

when i only channel 1 or only channel 2 input, there is no any noise.

but when i both Ch1 & Ch2 input, there is noise issue here.

Fullscreen audio_3256.txt Download 
static const RegValue RecordingBothOn[] = {
	//{0x00, 0x01},	//# switch to page1
	//{0x33, 0x40},	//# Enable MICBIAS and set to 1.25V, MICBIAS voltage is generated from AVDD
	{0x00, 0x00},
	{0x3D, 0x01},
	{0x00, 0x01},
	{0x01, 0x08},
	{0x02, 0x00},
	{0x3D, 0x00},
	{0x47, 0x32},
	{0x7B, 0x01},
	{0x00, 0x01},
	{0x33, 0x00}, //40

#ifdef CONFIG_TARGET_BOARD_R1_PRO
//	{0x34, 0x33},	//# IN1R, IN2L						is routed to Left MICPGA POSITIVE with 40K resistance
//	{0x36, 0xF0},	//# 	  IN2R		 	CM1L, 		is routed to Left MICPGA NEGATIVE with 40K resistance
//	{0x37, 0xF0},	//# IN1R, IN2R						is routed to Right MICPGA POSITIVE with 40K resistance
//	{0x39, 0xCC},	//# 	  	,			CM1L		is routed to Right MICPGA NEGATIVE with 40K resistance

	//{0x34, 0x22},	//# IN1R, IN2L						is routed to Left MICPGA POSITIVE with 40K resistance
	//{0x36, 0xA2},	//# 	  IN2R		 	CM1L, 		is routed to Left MICPGA NEGATIVE with 40K resistance
	//{0x37, 0xA2},	//# IN1R, IN2R						is routed to Right MICPGA POSITIVE with 40K resistance
	//{0x39, 0x82},	//# 	  	,			CM1L		is routed to Right MICPGA NEGATIVE with 40K resistance
	
	//{0x34, 0x02},	//# only mic /20K
	//{0x36, 0x82},	//# 	  
	//{0x37, 0x80},	//# 
	//{0x39, 0x82},	//# 		
	
	//{0x34, 0x20},	//# only BT /20K
       //{0x36, 0x20},	//# 	  
	//{0x37, 0x22},	//# 
	//{0x39, 0x00},	//# 	


	{0x34, 0xf3},  //0x55  //0x8a 
	{0x36, 0xf3}, 
	{0x37, 0xf3},   //0x44 //0x88 
	{0x39, 0xf3}, 
#endif
#ifdef CONFIG_TARGET_BOARD_10C_EVO
#if 0  // 20K
	{0x34, 0x0A},	//# IN1R,		IN3L				is routed to Left MICPGA POSITIVE with 40K resistance
	{0x36, 0x8A},	//# 			IN3R,	CM1L,		is routed to Left MICPGA NEGATIVE with 40K resistance
	{0x37, 0x88},	//# IN1R,		IN3R				is routed to Right MICPGA POSITIVE with 40K resistance
	{0x39, 0x8A},	//# 			IN3L,	CM1L		is routed to Right MICPGA NEGATIVE with 40K resistance
#else  // 40K
	{0x34, 0x0F},	//# IN1R,		IN3L					is routed to Left MICPGA POSITIVE with 40K resistance
	{0x36, 0xCF},	//# 			IN3R,	CM1L,	CM2L	is routed to Left MICPGA NEGATIVE with 40K resistance
	{0x37, 0xCC},	//# IN1R,		IN3R					is routed to Right MICPGA POSITIVE with 40K resistance
	{0x39, 0xCF},	//# 			IN3L,	CM1L,	CM2L	is routed to Right MICPGA NEGATIVE with 40K resistance
#endif
#endif

	{0x3B, 0x28},	//# Left MICPGA Gain is enabled, Left MICPGA Gain is set to 0dB 08
	{0x3C, 0x28},	//# Right MICPGA Gain is enabled, Right MICPGA Gain is set to 0dB 08

	{0x00, 0x00},	//# Select Page 0
	{0x53, 0x00},	//# Left ADC Channel Volume = 10dB 14
	{0x54, 0x00},	//# Left ADC Channel Volume = 10dB 14
	{0x51, 0xC0},	//# Power up LADC, Power up RADC
	{0x52, 0x00},	//# Unmute LADC, Unmute RADC
};

  • 0
    TI__Guru 57800 points

    Hi, Ray,

    Can you please share more information about the noise issue you are experiencing?.  is it something like crosstalk?, does it sound like a tone?.

    Can you please also share the sampling rate and frequency of I²S clocks used?. It is not common to see noise issues when two or more inputs are used with this or any or our codecs.

    I will look at the register configuration, but getting the information I asked above would help to identify the root cause.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 1330 points

    Hi, Sir,

    Below is my schematic,

    I2S LRCLK is 48K,

    IN1L is NC.

    thanks!

  • 0 in reply to Ray Hsu
    TI__Guru 57800 points

    Hi, Ray,

    Thanks for the feedback.

    From the schematic, it seems that there is no big problem, however, having IN1L floating if unused is not a good idea as some noise can be coupling though that connection. We recommend to connect unused inputs through a cap to GND. Can you please provide more details on the type of noise issue you are experiencing?. Is it noise from BT lines coupling on mic?.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer