I need to DC-couple the input signal. Can I use the INMx as a reference to an external differential amplifier?
Or, can I simply drive the INMx with external reference DC signal?
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I need to DC-couple the input signal. Can I use the INMx as a reference to an external differential amplifier?
Or, can I simply drive the INMx with external reference DC signal?
Grzgorz,
AFE5816 doesn't support pure DC signals. while DC coupled can be support when you bias the INP pin at the Vcm of 1V. the INM still needs the bypass cap for filtering out the noise.
meanwhile you will need to disable the LNA DC offset correct circuit per datasheet shows:
Thanks!
9.3.2.4 LNA High-Pass Filter (LNA HPF)
The LPF circuit in Figure 60 is a low-pass transfer function between the positive and negative inputs of the LNA.
The LPF results in a high-pass transfer function between the LNA input and output and can be used to reject
unwanted low-frequency leakage signal from the transducer. The high-pass filter in the LNA is active for both CW
and TGC mode. The effective corner frequency of the HPF is determined by the capacitor connected at the INMx
pin of the device. Internal to the device, a 10-nF capacitor is connected at the INMx node. A large capacitor
(such as 1 μF) can be connected externally at the INMx pin for setting the low corner frequency (< 2 kHz) of the
LNA dc offset correction circuit. By default, a capacitor is not required to be connected at the INMx pin. To
disable this HPF, set the LNA_HPF_DIS register bit to 1. This bit powers down the unity feedback buffer
connected between positive and negative input of the LNA shown in Figure 60. For a given INMx capacitor, the
corner frequency of the HPF can be programmed using the LNA_HPF_PROG bit. Table 3 lists the HPF corner
frequency as a function of the CINM_EXT capacitor connected at the INMx pin across various LNA_HPF_PROG bit
settings.