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AFE4490: QUESTION：LED1 and LED2

difang LIU
Prodigy 30 points
Part Number: AFE4490


We have measured the BG, VCM, TX_REF, and CLKOUT signals of the AFE4490, where the CLKOUT output shows a 4 MHz triangular waveform. After configuring and writing the code, we are only receiving the ADC_READY signal. However, it appears that the constant current sources for LED1 and LED2 are not functioning. Could you please advise on the possible reasons for this issue?

  • 0
    TI__Mastermind 38700 points

    您好，

          您使用的是哪种LED驱动电路？ LED_DRV_SUP和TX_CTRL_SUP电压是多少？

          

          请重新确认AFE4490 Integrated Analog Front-End for Pulse Oximeters datasheet (Rev. H)  "8.3.5 Transmit Section" 内容。

  • 0 回复 Alice
    Prodigy 30 points

    We used a push-pull drive configuration and modified the register settings as shown below.

    AFE4490_Write(CONTROL0, 0x000000); //写寄存器 delay_ms(10); AFE4490_Write(CONTROL0, 0x000008); //软件复位，所有寄存器清零 delay_ms(10); AFE4490_Write(TIAGAIN, 0x000000); // CF = 5pF, RF = 500kΩ delay_ms(10); AFE4490_Write(TIA_AMB_GAIN, 0x000001); //消除环境光DC 1uA delay_ms(10); AFE4490_Write(LEDCNTRL, 0x001414); // 150mA 7ma LED1 LED2 delay_ms(10); AFE4490_Write(CONTROL2, 0x000800); // 0.75V LED_RANGE=100mA, LED=50mA Push delay_ms(10); AFE4490_Write(CONTROL1, 0x010107); // Timers ON, average 3 samples 1E 107 PD_ALM LED_ALM 001LED1 delay_ms(10); AFE4490_Write(PRPCOUNT, 0x001F3F);//7999 4Mhz 250ns 2ms 1F3F 400hz delay_ms(10); //LED2采样区间 AFE4490_Write(LED2STC, 0x001770); // 6050 红外光 0x0017A2 delay_ms(10); AFE4490_Write(LED2ENDC, 0x001F3E); // delay_ms(10); AFE4490_Write(LED2LEDSTC, 0x001770); //6000 delay_ms(10); AFE4490_Write(LED2LEDENDC, 0x001F3F); //7999 delay_ms(10); AFE4490_Write(LED2CONVST, 0x000002);//4 delay_ms(10); AFE4490_Write(LED2CONVEND, 0x0007CF);//1999 delay_ms(10); //ALED2采样 AFE4490_Write(ALED2STC, 0x000000); //50 delay_ms(10); AFE4490_Write(ALED2ENDC, 0x0007CE); //1998 delay_ms(10); AFE4490_Write(ALED2CONVST, 0x0007D2); //2004 delay_ms(10); AFE4490_Write(ALED2CONVEND, 0x000F9F); //3999 delay_ms(10); //LED1采样时间 AFE4490_Write(LED1STC, 0x0007D0); //红光2050 delay_ms(10); AFE4490_Write(LED1ENDC, 0x000F9E); //3998 delay_ms(10); AFE4490_Write(LED1LEDSTC, 0x0007D0); //2000 delay_ms(10); AFE4490_Write(LED1LEDENDC, 0x000F9F); //3999 delay_ms(10); AFE4490_Write(LED1CONVST, 0x000FA2); //4004 delay_ms(10); AFE4490_Write(LED1CONVEND, 0x00176F); //5999 //ALED1采样 AFE4490_Write(ALED1STC, 0x000FA0); //4050 delay_ms(10); AFE4490_Write(ALED1ENDC, 0x00176E); //5998 delay_ms(10); AFE4490_Write(ALED1CONVST, 0x001772);//6004 delay_ms(10); AFE4490_Write(ALED1CONVEND, 0x001F3F); //7999 delay_ms(10); //ADC复位 AFE4490_Write(ADCRSTCNT0, 0x000000); // delay_ms(10); AFE4490_Write(ADCRSTENDCT0, 0x000000); //ALED2 delay_ms(10); AFE4490_Write(ADCRSTCNT1, 0x0007D0); //2000 delay_ms(10); AFE4490_Write(ADCRSTENDCT1, 0x0007D0); //LED1 delay_ms(10); AFE4490_Write(ADCRSTCNT2, 0x000FA0); //4000 delay_ms(10); AFE4490_Write(ADCRSTENDCT2, 0x000FA0); //ALED1 delay_ms(10); AFE4490_Write(ADCRSTCNT3, 0x001770); //6000 delay_ms(10); AFE4490_Write(ADCRSTENDCT3, 0x001770); // LED2
    After configuration, a 2 ms ADC_READY signal was received; however, the IR signal remained at 0, and the RED signal appeared to be close to full-scale. In addition, there was no signal variation observed on the TXM and TXP pins. What could be the reason for this?

  • 0 回复 Alice
    Prodigy 30 points

    We used a push-pull drive configuration and modified the register settings as shown below.LED_DRV_SUP=5V  TX_CTRL_SUP=5V
    After configuration, a 2 ms ADC_READY signal was received; however, the IR signal remained at 0, and the RED signal appeared to be close to full-scale. In addition, there was no signal variation observed on the TXM and TXP pins. What could be the reason for this? AFE4490_Write(CONTROL0, 0x000000); //写寄存器 delay_ms(10); AFE4490_Write(CONTROL0, 0x000008); //软件复位，所有寄存器清零 delay_ms(10); AFE4490_Write(TIAGAIN, 0x000000); // CF = 5pF, RF = 500kΩ delay_ms(10); AFE4490_Write(TIA_AMB_GAIN, 0x000001); //消除环境光DC 1uA delay_ms(10); AFE4490_Write(LEDCNTRL, 0x001414); // 150mA 7ma LED1 LED2 delay_ms(10); AFE4490_Write(CONTROL2, 0x000800); // 0.75V LED_RANGE=100mA, LED=50mA Push delay_ms(10); AFE4490_Write(CONTROL1, 0x010107); // Timers ON, average 3 samples 1E 107 PD_ALM LED_ALM 001LED1 delay_ms(10); AFE4490_Write(PRPCOUNT, 0x001F3F);//7999 4Mhz 250ns 2ms 1F3F 400hz delay_ms(10); //LED2采样区间 AFE4490_Write(LED2STC, 0x001770); // 6050 红外光 0x0017A2 delay_ms(10); AFE4490_Write(LED2ENDC, 0x001F3E); // delay_ms(10); AFE4490_Write(LED2LEDSTC, 0x001770); //6000 delay_ms(10); AFE4490_Write(LED2LEDENDC, 0x001F3F); //7999 delay_ms(10); AFE4490_Write(LED2CONVST, 0x000002);//4 delay_ms(10); AFE4490_Write(LED2CONVEND, 0x0007CF);//1999 delay_ms(10); //ALED2采样 AFE4490_Write(ALED2STC, 0x000000); //50 delay_ms(10); AFE4490_Write(ALED2ENDC, 0x0007CE); //1998 delay_ms(10); AFE4490_Write(ALED2CONVST, 0x0007D2); //2004 delay_ms(10); AFE4490_Write(ALED2CONVEND, 0x000F9F); //3999 delay_ms(10); //LED1采样时间 AFE4490_Write(LED1STC, 0x0007D0); //红光2050 delay_ms(10); AFE4490_Write(LED1ENDC, 0x000F9E); //3998 delay_ms(10); AFE4490_Write(LED1LEDSTC, 0x0007D0); //2000 delay_ms(10); AFE4490_Write(LED1LEDENDC, 0x000F9F); //3999 delay_ms(10); AFE4490_Write(LED1CONVST, 0x000FA2); //4004 delay_ms(10); AFE4490_Write(LED1CONVEND, 0x00176F); //5999 //ALED1采样 AFE4490_Write(ALED1STC, 0x000FA0); //4050 delay_ms(10); AFE4490_Write(ALED1ENDC, 0x00176E); //5998 delay_ms(10); AFE4490_Write(ALED1CONVST, 0x001772);//6004 delay_ms(10); AFE4490_Write(ALED1CONVEND, 0x001F3F); //7999 delay_ms(10); //ADC复位 AFE4490_Write(ADCRSTCNT0, 0x000000); // delay_ms(10); AFE4490_Write(ADCRSTENDCT0, 0x000000); //ALED2 delay_ms(10); AFE4490_Write(ADCRSTCNT1, 0x0007D0); //2000 delay_ms(10); AFE4490_Write(ADCRSTENDCT1, 0x0007D0); //LED1 delay_ms(10); AFE4490_Write(ADCRSTCNT2, 0x000FA0); //4000 delay_ms(10); AFE4490_Write(ADCRSTENDCT2, 0x000FA0); //ALED1 delay_ms(10); AFE4490_Write(ADCRSTCNT3, 0x001770); //6000 delay_ms(10); AFE4490_Write(ADCRSTENDCT3, 0x001770); // LED2

  • 0 回复 difang LIU
    TI__Mastermind 38700 points

    您好，

         AFE4490SPO2EVM Evaluation board | TI.com的GUI中有默认的寄存器配置请参考。    

         请参考AFE4400 / AFE4490 / AFE4403 / AFE4404 FAQs - Data converters forum - Data converters - TI E2E support forums 的“7a”部分检查电压；及“9” 建议的初始化序列。