Datasheet AH4930 (Diodes) - 8

AH4930 Application Information 1 General Description
As described on the block diagram the three vector components of the magnetic flux density (BX, BY and BZ) applied to the IC are sensed through the sensor front-end. The 3-axies Hall signals are generated at the Hall plates and amplified. The analog front-end is based on a fully differential analog chain with offset cancellation technique. The conditioned analog signals are converted through an ADC and provided to a DSP block for further processing. The DSP stage is a customized finite state machine whose major function consists of signal conditioning of the XYZ Hall signals. Offset and sensitivity drift compensation are using the calibrated internal temperature sensor to improve the sensor’s accuracy. These 3D linear Hall measurements can be read out to the communication bus master. The supported communication protocols are I2C, where the AH4930 is a slave on the bus. Upon read-back, it is then up to the microcontroller to process the measurement data in order to achieve more complex position sensing functionality required by the application.
2 Functional Description
The AH4930 consists of three main function blocks containing: • The power management system: containing a low-power oscillator, a fast oscillator, biasing, accurate reset, and undervoltage detection. • The analog front-end: containing the HALL biasing, HALL sensing with multiplexers and an ADC. Furthermore, a temperature sensor is implemented. • The FSM/DSP and I2C interface: containing the Finite State Machine and DSP to process data, I2C interface to communicate to master, register file to store parameters and I/O pads.
2.1 Power Management
The power management unit provides the conversion modes control in the IC, a power-on reset function and fast/low-power oscillators as clock sources. It also handles the startup procedure. • When startup this unit: – provides an accurate reset/UVLO detector, activates the biasing, and fast/low oscillator. – the applied voltage level on SDA pin must be set to high for I2C mode. – let sensor enter power-down mode (also can be configured via I2C interface). Note: 13. The sensor enters the power-down mode by default after power-up. • After AH4930 re-configured to one of the operating modes a measurement cycle is performed periodically including: – qualifies reset/UVLO condition, starts the internal biasing and enables the fast oscillator. – enables the HALL biasing and the measurements of the three HALL probe channels sequentially including temperature. – enters the configured mode again. Only if the supply voltage is high enough to be above VUVLO measurements are executed, otherwise the reset circuit will halt the state machine until the supply level is reached and continues its operation. The functions are also restarted if a power-on reset event occurs.
2.2 Analog Front-End (Signal Path)
The sensing part of analog front-end performs the measurements of the magnetic field in X, Y and Z direction. Each X, Y and Z-HALL data is consecutively output to a multiplexer, which is then connected to an ADC. The temperature is determined prior to the three HALL channels to compensate sensitivity drift and output as sensed junction temperature. AH4930 8 of 23 January 2025 Document number: DS46768 Rev. 1 - 2
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