1 Introduction

The AFE20408 is an analog front end (AFE) highly integrated PA biasing controller. The AFE combines 8 DACs, a multi-input ADC, and fast gate bias switches in a tiny 5mm x 5mm package.

The eight 13-bit DACs each have a range of 0V to 10V and –10V to 0V. The DACs are grouped in two blocks, each with a separate supply voltage. This allows for both positive and negative DAC outputs on one device, enabling one device to power both LDMOS and GaN PAs.

The AFE20408 has two groups of four fast low on-resistance switched outputs. These switched outputs allow for fast switching between two DAC channels at different voltages facilitating time-division duplexing. These switched outputs can also switch from a DAC voltage to VSS, allowing more DAC channels to be used for gate biasing. Built in redundancy allows the switches to be toggled either through software bits or hardware pins.

The AFE20408 features an integrated 16-bit ADC. The ADC has two high-voltage bus lines that measure voltages up to an 85V input and two pairs of high-side current sense inputs. Furthermore, the device has an internal temperature sensor. All of these inputs can be configured to set an alarm condition with user-defined minimum and maximum thresholds.

Other features of the AFE20408 include a flexible digital VIO voltage input from 1.8V to 5V, an auto-detectable SPI or I²C communication interface, sixteen I²C target addresses, a device-good pin (PAON) to indicate device readiness, and a FLEXIO pin that can be configured as RESET, ALARMOUT, ALARMIN, LDAC, DRVEN2, or a GPIO pin.