如图是PGA280的内部输入开关电路,(说明:VSP为输入+15V,VSN为输入-15V,VSON为输出地,VSOP为输出电源+5.2V,图中无VSOP)
测试条件:
1:+15V,-15V间为一组电阻串, 中间测试电阻的上端为0.05mV左右,稳定到0.1uV, 下端约为99.95mV 稳定到0.1uV
(可以简单理解为输入是Vs=100mV的非对称信号)
2:INP1及INN2接于上述0.05mV处; INP2及INN1接于上述99.95mV处
(即,如果是差分输入时,IN1与IN2是相反方向输入的)
3:设计要求采用差分输入
问题,
设置为INP1/INN1差分输入,或者INP2/INN2差分输出,配置不同的GAIN输出,均无反应(VO+=VO-=VCOM; 差分输出,VCOM为中点电位,实际为2.5V);
但设置为INP1 或 INN1 或INP2 或INN2单端输入(对应另一端C1/或C2接VSON------VSON为输出电源地)
设置不同的GAIN(增益:1/8,1/4,~,64,128),输出都为相应变化,输出电压基本符合增益所得电压.;
但采用差分输入时,就是没有输出;
程序如下:(说明,在每个设置后面加入回读函数,证明了设置是成功的)
(只例出关键程序,前部分定义是PGA280功能定义)
//各个控制开关使能位;
#define GPA280_PRA_SW1_A1 0x40
#define GPA280_PRA_SW1_A2 0x20
#define GPA280_PRA_SW1_B1 0x10
#define GPA280_PRA_SW1_B2 0x08
#define GPA280_PRA_SW1_C1 0x04
#define GPA280_PRA_SW1_C2 0x02
#define GPA280_PRA_SW1_D12 0x01
#define GPA280_PRA_SW2_F1 0x08
#define GPA280_PRA_SW2_F2 0x04
#define GPA280_PRA_SW2_G1 0x02
#define GPA280_PRA_SW2_G2 0x01
//组合
#define GPA280_SW1_SEL_INP1 GPA280_PRA_SW1_A1 //单连接 1+
#define GPA280_SW1_SEL_INN1 GPA280_PRA_SW1_A2 //单连接 1-
#define GPA280_SW1_SEL_IN1 (GPA280_PRA_SW1_A1 | GPA280_PRA_SW1_A2) //使用 1+-
#define GPA280_SW1_SEL_INP2 GPA280_PRA_SW1_B1 //单连接 2+
#define GPA280_SW1_SEL_INN2 GPA280_PRA_SW1_B2 //单连接 2-
#define GPA280_SW1_SEL_IN2 (GPA280_PRA_SW1_B1 | GPA280_PRA_SW1_B2) //使用 2+-
#define GPA280_SW1_SEL_SHORT_IN1 GPA280_PRA_SW1_D12 //短路 1+ 1-输入
#define GPA280_SW2_SEL_INP1_TO_GND GPA280_PRA_SW2_G1 //1+ 短地
#define GPA280_SW2_SEL_INN1_TO_GND GPA280_PRA_SW2_G2 //1- 短地
#define GPA280_SW1_SEL_P_TO_GND GPA280_PRA_SW1_C1 //+短地
#define GPA280_SW1_SEL_N_TO_GND GPA280_PRA_SW1_C2 //-短地
#define GPA280_SW1_SEL_SHORT_P_N (GPA280_SW1_SEL_IN1 | GPA280_PRA_SW1_D12) //使用 1+-, 且1+短1-
#define GPA280_SW2_SEL_INP1_UP_100UA GPA280_PRA_SW2_F1 //上拉恒流
#define GPA280_SW2_SEL_INN1_DN_100UA GPA280_PRA_SW2_F2 //下拉恒流
#define GPA280_SW_OPEN 0x00
PGA280_Init();
PGA280_SW_A_D(GPA280_SW1_SEL_IN1); //INP1 INN1输入时
//PGA280_SW_A_D(GPA280_SW1_SEL_INP1 | GPA280_SW1_SEL_N_TO_GND); //INP1单端输入, N接地
PGA280_SW_F_G(GPA280_SW_OPEN);
//0~10表示ＧＡＩＮ＝１／８～１２８
PGA280_Gain_Set(0);
PGA280_Gain_Set(1);
PGA280_Gain_Set(2);
PGA280_Gain_Set(3);
PGA280_Gain_Set(4);
PGA280_Gain_Set(5);
PGA280_Gain_Set(6);
PGA280_Gain_Set(7);
PGA280_Gain_Set(8);
PGA280_Gain_Set(9);
PGA280_Gain_Set(10);
下面连接是TI官网发贴求助连接
http://www.deyisupport.com/question_answer/analog/amplifiers/f/52/p/120899/334453.aspx#334453
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