46.6.1.2 Conversion Channel

The ADCs convert voltage, current and temperature.

All ADC channels are built around the same Delta-Sigma A/D converter. The voltage reference of this converter is the VREF_AFE pin voltage with a reference to ground (GNDA pin). This reference voltage can be internally or externally sourced. The converter sampling rate is typically 1.024 MHz. An external low-pass filter, typically a passive R-C network, is required at each ADC input to reject frequency images around this sampling frequency (anti-alias).

The analog inputs are designed to sample 0V centered signals. As these inputs have internal ESD protection devices connected to GNDA, the maximum input signal level defined in the section “Electrical Characteristics”, typically ±0.25V, must be respected to avoid leakage in these devices.

Voltage channels have single-ended inputs with a reference to the VN pin. The VN pin must be connected to a low-noise ground. The user must take care that no voltage drop on the ground net is sampled by the ADC by a non-optimal connection of the VN pin.

Current channels have a programmable gain amplifier (PGA) to accommodate low input signals. The PGA improves the dynamic range of the channel as the input referred noise is reduced when gain increases. The PGA does not introduce any delay or bandwidth limitation on the current channels compared to the voltage channels. The channels (voltage or current) are always sampled synchronously. The input impedance of the PGA depends on the programmed gain.