米6体育平台手机版

ZHCSS23A april 2023 – august 2023 LMH32401-Q1

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

RGT|16
- MPQF119H

散热焊盘机械数据 (封装 | 引脚)

RGT|16
- QFND778

订购信息

8.1 Application Information

The differential outputs of the LMH32401-Q1 can directly drive a high-speed differential input ADC. Figure 8-1 shows the LMH32401-Q1 differential outputs directly driving the ADC12QJ1600. The effective signal gain between the TIA input and the ADC input is 2 kΩ or 20 kΩ when driving an ADC with a 100-Ω differential input impedance (R_{ADC_IN} = 50 Ω). Equation 2 gives the effective signal gain between the TIA input and the ADC input when driving an ADC with any other value of differential input impedance (R_{ADC_IN} ≠ 50 Ω).

Figure 8-1 LMH32401-Q1 to ADC Interface

Equation 2.

A_{Z} = 2 k Ω (o r 20 k Ω) \times 1.2 \times \frac{2 \times R_{A D C_I N}}{(2 \times R_{A D C_{I N}} + 20 Ω)}

where

A_Z = Differential gain from the TIA input to the ADC input
R_{ADC_IN} = Input resistance of the ADC

Figure 8-2 shows a matching resistor network between the LMH32401-Q1 output and the ADC12QJ1600 input. The matching network is needed to prevent signal reflections when the signal path between the LMH32401-Q1 and ADC is very long. Equation 3 gives the effective gain from the TIA input to the ADC input when using a matching resistor network.

Figure 8-2 LMH32401-Q1 to ADC Interface With a Matching Resistor Network

Equation 3.

A_{Z} = 2 k Ω (o r 20 k Ω) \times 1.2 \times \frac{2 \times R_{A D C_I N}}{(2 \times R_{A D C_I N} + 2 \times R_{I S O} + 20 Ω)}

where

A_Z = Gain from the TIA input to the ADC input
R_{ADC_IN} = Differential input resistance of the ADC
R_ISO = Series resistance between the TIA and ADC

Equation 4 gives the voltage to be applied at VOD (pin 9) if a certain differential offset voltage (V_OD) is needed at the ADC input for the circuit in Figure 8-2.

Equation 4.

V_{V O D} = V_{O D} \times (\frac{1}{1.2}) \times \frac{(2 \times R_{A D C_I N} + 2 \times R_{I S O} + 20 Ω)}{(2 \times R_{A D C_I N})}

where

V_VOD = Voltage applied at pin 9
V_OD = Desired differential offset voltage at the ADC input
R_{ADC_IN} = Differential input resistance of the ADC
R_ISO = Series resistance between the TIA and ADC