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PCM6240-Q1: Inputs Shorted to VBAT

Part Number:PCM6240-Q1

Dear team,

I have a question about short to VBAT in microphone mode.

I did three test case,as following:

PCM6240 in DC-Coupled Microphone Differential Input Connection,

(1)Test case 1:when pcm6240 connect all 4 MICs with MIC Load,short MIC1+ /MIC2+ /MIC3+ /MIC4+ to VBAT,everything is OK;

(2)Test case 2:only connect MIC1 load,and mic2/mic3/mic3 did't connect mic load,when short mic1+ to VABT,voltage of mic2,mic3,mic4 will change from 9v to 12V,and sofaware log also show mic2,mic3,mic4 are shorted to vbat.

(3)Test case 3:when mic1/mic2/mic3/mic4 did't connect mic load,mic1+ shorted to vbat,and sofaware log show mic1,mic2,mic3,mic4 are shorted to vbat.

I cannot understand the result in test case 2 and case3,if one of the channel (MIC1)only connect the mic load,when the mic1+ channel short to vbat,why the other channel will report the short to vbat too?

Can you help analyze the cause of this problem?Is this anomaly software log  because of the pull-up resistor? Is this problem normal?

Amy Luo:

您好,

上述描述中是指的故障诊断报告结果不是期望状态是吗?

电路图中MIC_BIAS1是9V和VBAT_IN是14V是吗?MIC_BIAS1和VBAT_IN电压是怎样产生的呢?VBAT_IN 接入 PCM6240-Q1的这部分电路可以附出来吗?

,

WAN zhilong:

您好, 

    MIC_BIAS内部配置,输出DC9V;VBAT_IN输入为DC14V;VBAT大于MIC_BIAS电压; S32K通过I2C读取PCM5240的一些状态;     

    当PCM6240使能4路MIC输入诊断时,

(1)若4路输入都不接MIC负载时,对MIC1+进行短路到VBAT,PCM6240的诊断报告错误为:MIC2+/MIC3+/MIC4+也短路到VBAT;理论上期望的是,只有MIC1+短路到VBAT;

        问题:请问这个情况是否正常?是不是因为4路MIC的偏置电压上拉到同一个MIC_BIAS1电源导致的?

(2)若MIC1接负载,其他3路MIC2/MIC3/MIC4都不接MIC负载时,对MIC1+进行短路到VBAT,PCM6240的也诊断报告错误为:MIC2+/MIC3+/MIC4+也短路到VBAT;理论上期望的是,只有MIC1+短路到VBAT;

        问题:请问这个情况是否正常?应该怎么解释这个现象?

(3)若4路MIC输入都接上MIC负载时,对应地进行短路VBAT测试,其诊断报告都是正常;即MIC1+短路到VBAT时,只会报告:MIC1+短路到VBAT。

,

Amy Luo:

1、这个情况是正常的,如您所说是因为4路MIC的偏置电压上拉到同一个MIC_BIAS1电源导致的;

2、这个情况应该也是正常的,您实测MIC2+/MIC3+/MIC4+电压应该被拉到VBAT,只要电压差小于设置阈值就会报告故障状态:

 

,

Amy Luo:

3、在其他路MIC输入接上MIC时,因为MIC_BIAS1电压被MIC的上拉电阻、MIC和MIC的下拉电阻分压,即使MIC1+短路到VBAT,这个分压回路还是存在的,仅是MIC_BIAS1可能被VBAT拉至14V,不会使VBAT_IN与INxx间的电压小于设置阈值(最大450mV),就不会报告故障。

希望以上解释清楚了您的疑惑。

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