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)

DCK|5
- MPDS025J
DBV|5
- MPDS018T

散热焊盘机械数据 (封装 | 引脚)

订购信息

8.2.2.2 Detailed Design Procedure

The transfer function between the output voltage (V_OUT), the input current, (I_IN) and the reference voltage (V_REF) is defined in Equation 5.

Equation 5.

V_{O U T} = I_{I N} + R_{F} + V_{R E F}

Where:

Equation 6.

V_{R E F} = V_{+} \times (\frac{R_{1} \times R_{2}}{R_{1} + R_{2}})

Set V_REF to 100 mV to meet the minimum output voltage level by setting R1 and R2 to meet the required ratio calculated in Equation 7.

Equation 7.

\frac{V_{R E F}}{V_{+}} = \frac{0.1 V}{3.3 V} = 0.0303

The closest resistor ratio to meet this ratio sets R1 to 11.5 kΩ and R2 to 357 Ω.

The required feedback resistance can be calculated based on the input current and desired output voltage.

Equation 8.

R_{F} = \frac{V_{O U T} - V_{R E F}}{I_{I N}} = \frac{3.2 V - 0.1 V}{10 μ A} = 310 \frac{k V}{A} \approx 309 k Ω

Calculate the value for the feedback capacitor based on R_F and the desired –3-dB bandwidth, (f_–3dB) using Equation 9.

Equation 9.

C_{F} = \frac{1}{2 \times π \times R_{F} \times f_{- 3 d B}} = \frac{1}{2 \times π \times 309 k Ω \times 50 k H z} = 10.3 p F \approx 10 p F

The minimum op amp bandwidth required for this application is based on the value of R_F, C_F, and the capacitance on the INx– pin of the LMV358A-Q1 which is equal to the sum of the photodiode shunt capacitance, (CPD) the common-mode input capacitance, (CCM) and the differential input capacitance (CD) as Equation 10 shows.

Equation 10.

C_{I N} = C_{P D} + C_{C M} + C_{D} = 47 p F + 5 p f + 1 p F = 53 p F

The minimum op amp bandwidth is calculated in Equation 11.

Equation 11.

F = B G W \geq \frac{C_{I N} + C_{F}}{2 \times π \times R_{F} \times C_{F^{2}}} \geq 324 k H z

The 1-MHz bandwidth of the LMV3xxA-Q1 meets the minimum bandwidth requirement and remains stable in this application configuration.