米6体育平台手机版

ZHCSQY6E August 2022 – July 2024 OPA2992-Q1 , OPA4992-Q1 , OPA992-Q1

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

PW|14
- MPDS360A
D|14
- MPDS177H

散热焊盘机械数据 (封装 | 引脚)

订购信息

7.2.1.2 Detailed Design Procedure

The transfer function of the circuit in Figure 7-1 is given in Equation 1:

Equation 1.

V_{O U T} = I_{L O A D} \times R_{S H U N T} \times G a i n

The load current (I_LOAD) produces a voltage drop across the shunt resistor (R_SHUNT). The load current is set from 0A to 1A. To keep the shunt voltage below 100mV at maximum load current, the largest shunt resistor is defined using Equation 2:

Equation 2.

R_{S H U N T} = \frac{V_{S H U N T_M A X}}{I_{L O A D_M A X}} = \frac{100 m V}{1 A} = 100 m Ω

Using Equation 2, R_SHUNT is calculated to be 100mΩ. The voltage drop produced by I_LOAD and R_SHUNT is amplified by the OPA992-Q1 to produce an output voltage of 0V to 4.9V. The gain needed by the OPA992-Q1 to produce the necessary output voltage is calculated using Equation 3:

Equation 3.

G a i n = \frac{(V_{O U T_M A X} - V_{O U T_M I N})}{(V_{I N_M A X} - V_{I N_M I N})}

Using Equation 3, the required gain is calculated to be 49V/V, which is set with resistors R_F and R_G. Equation 4 is used to size the resistors, R_F and R_G, to set the gain of the OPA992-Q1 to 49V/V.

Equation 4.

G a i n = 1 + \frac{(R_{F})}{(R_{G})}

Choosing R_F as 5.76kΩ, R_G is calculated to be 120Ω. R_F and R_G were chosen as 5.76kΩ and 120Ω because the values are standard value resistors that create a 49:1 ratio. Other resistors that create a 49:1 ratio can also be used. However, excessively large resistors generate thermal noise that exceeds the intrinsic noise of the op amp. Figure 7-2 shows the measured transfer function of the circuit shown in Figure 7-1.