米6体育平台手机版

ZHCSKP5D june 2020 – april 2023 LMV321A-Q1 , LMV324A-Q1 , LMV358A-Q1

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

D|8
- MSOI002K
DGK|8
- MPDS028E

散热焊盘机械数据 (封装 | 引脚)

订购信息

8.2.1.2 Detailed Design Procedure

The transfer function of the circuit in Figure 8-1 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 0 A to 1 A. To keep the shunt voltage below 100 mV at maximum load current, the largest shunt resistor is shown 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 100 mΩ. The voltage drop produced by I_LOAD and R_SHUNT is amplified by the LMV3xxA-Q1 to produce an output voltage of approximately 0 V to 4.9 V. The gain needed by the LMV3xxA-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 49 V/V, which is set with resistors R_F and R_G. Equation 4 sizes the resistors R_F and R_G, to set the gain of the LMV3xxA-Q1 to 49 V/V.

Equation 4.

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

Selecting R_F as 57.6 kΩ and R_G as 1.2 kΩ provides a combination that equals 49 V/V. Figure 8-2 shows the measured transfer function of the circuit shown in Figure 8-1. Notice that the gain is only a function of the feedback and gain resistors. This gain is adjusted by varying the ratio of the resistors and the actual resistors values are determined by the impedance levels that the designer wants to establish. The impedance level determines the current drain, the effect that stray capacitance has, and a few other behaviors. There is no best impedance selection that works for every system, choose an impedance that is an excellent choice for the system parameters.