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A1334LLETR-60-T Datasheet(PDF) 7 Page - Allegro MicroSystems |
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A1334LLETR-60-T Datasheet(HTML) 7 Page - Allegro MicroSystems |
7 / 20 page Precision Hall-Effect Angle Sensor IC A1334 6 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com FUNCTIONAL DESCRIPTION Operational Modes The A1334 angle sensor device is designed to support a wide variety of automotive applications requiring measuring 0° to 360° angle positions. An option for two electrically-independent die in the same package provides solid-state consistency and reliability. Each die SPI port can be configured in a different RPM mode. The data output selection is controlled by the address request in the SPI Read command. The A1334 has dual identical system-on-chip (SoC) architecture. The output of each die is used by the host microcontroller to provide a single channel of target data. Angle Measurement The A1334 can monitor the angular position of a rotating magnet at speeds ranging from 0 to more than 7600 rpm. At lower rotational speeds, the A1334 provides high-resolution angle mea- surement accuracy. It can also support higher rates of rotational speeds at reduced levels of angle measurement accuracy. The A1334 can be configured to operate in two angular measure- ment modes of operation: Low RPM mode, and High RPM mode. For applications that have a speed range from 0 to 500 rpm (can vary with AVG), the Low RPM mode provides increased resolution. For applications above 500 rpm, configuring the A1334 in High RPM mode provides angle measurements with standard resolution. Above 7600 rpm, the A1334 continues to provide angle data; however, the accuracy is proportionally reduced. The actual update rate of Low RPM mode can be changed by setting the AVG bits in the EEPROM. (See the appendix Program- ming Reference for details.) The selection of Low RPM mode or High RPM mode can be programmed, via the Angle_Meas_Mode bit, for the expected maximum rotational speed of the magnet in operation to provide the highest corresponding level of angle accuracy. However, the A1334 provides valid output data regard- less of the selected mode and the application speed. Although the range of the resolution of the measurement data output, RESANGLE, is determined by the selection of either High RPM or Low RPM mode, the measurement is also affected by the intensity (B, in gauss) of the applied magnetic field from the target. At lower intensities, a reduced signal-to-noise ratio will cause one or two LSBs to change state randomly due to noise, and the effective DAC resolution is reduced. These factors work together, so when High RPM mode is selected, the effective range of resolution is 8 to 10 bits (from lower to higher field intensities), and in Low RPM mode, the effective range is 11 to 12 bits, depending on field strength and AVG selection. Regardless of the field intensity and mode selection, the transmis- sion protocol and number formatting remains the same. The MSB is always transmitted first. The entire number should be read. The Output Angle is always calculated at maximum resolution. To be more explicit: AngleOUT = 360 (°) × D[12:0] / (213) (1) This formula is always true, regardless of the applied field intensity. What changes with the field and speed setting is how uniform the LSBs of the measurement data (D 12:x) will be. When using the dual die version of the A1334, it should be noted that the secondary die (E2) is rotated 180° relative to the primary die (E1). This results in a difference in measurement of approxi- mately 180° between the two die, given perfect alignment of each die to the target magnet. This phenomenon can be counteracted by subtracting the offset using a microprocessor. Alternatively, the difference between the two die can be compensated for using the EEPROM for setting the Reference Angle. System-Level Timing The A1334 outputs a new angle measurement every tANG µs. In High RPM mode, the A1334 outputs a new angle measurement every tANG µs, with an effective resolution of 10 bits. There is, however, a latency of tLAT, from when the rotating magnet is sampled by the CVH to when the sampled data has been completely transmitted over the SPI interface. Because an SPI interface Read command is not synchronous with the CVH tim- ing, but instead is polled by the external host microcontroller, the latency can vary. For single back-to-back SPI transactions (first transaction is sending the Read register 0x0 command, second is retrieving the angle data) the following scenarios are possible: • Worst case: 2 CVH cycle + 2 SPI cycles • Best case: 1.5 SPI cycles; 2 µs, assuming a 10 MHz SPI clock |
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