TLE4998C8D Datasheet, PDF (22/28 Pages) Infineon Technologies AG – High Performance Programmable Dual Linear Hall Sensor

TLE4998C8D Grade1
SPC Output Definition
9.2
Unit Time Setup
The basic SPC protocol unit time granularity is defined as 3 μs. Every timing is a multiple of this basic time unit.
To achieve more flexibility, trimming of the unit time can be used to:
• Allow a calibration trim within a timing error of less than 20% clock error (as given in SAE standard)
• Allow a modification of the unit time for small speed adjustments
This enables a setup of different unit times, even if the internal RC oscillator varies by ±20%. Of course, timing
values that are too low could clash with timing requirements of the application and should therefore be avoided,
but in principle it is possible to adjust the timer unit for a more precise protocol timing. The output characteristic
depends on the external load, the wiring, as well on the pull-up voltage and the temperature. Furthermore,
sufficient driving capability of the sensor counterpart (ECU) is mandatory, in order to be able to maintain the herein
given master pulse requirements. All these parameters have considerable influence to find the proper unit time
setup.
Table 9-6
Pre-divider Setting
Parameter
Symbol
Values
Min. Typ. Max.
Register size
Prediv
4
Unit time
t_UNIT
2.0
1) Prediv default is decimal = 8 for 3 μs nominal SPC unit time.
2) RC oscillator frequency variation ± 20%.
3.88
Unit
bit
μs
Note / Test Condition
Pre-divider¹⁾
Clk_UNIT=8 MHz²⁾
The nominal unit time is calculated by:
f_UNIT = (Prediv+16) / Clk_UNIT
Clk_UNIT = 8MHz ± 20%
(9.1)
9.2.1 Master Pulse Requirements
An SPC transmission is initiated by a Master pulse on the OUT pin. To detect a low-level on the OUT pin, the
voltage must be below a threshold V_thf. The sensor detects that the OUT line has been released as soon as V_thr
is crossed. Figure 9-2 shows the timing definitions for the master pulse. The master low time t_mlow as well as the
total trigger time t_mtr are individual for the different SPC modes and are given in the subsequent sections.
It is recommended to choose the typical master low time exactly between the minimum and the maximum possible
time: t_mlow,typ = (t_mlow,min + t_mlow,max) / 2. Although the allowed timing windows are larger for longer low times, the
master should use a crystal oscillator clock source to provide a high timing accuracy (approx. 1%). For improved
robustness, the master pulse can be adopted by the master once the effective unit time is known through the
sensor’s synchronisation period length. If the master low time exceeds the maximum low time, the sensor does
not respond and is available for a next triggering 30μs after the master pulse crosses V_thr. t_md,tot is the delay
between internal triggering of the falling edge in the sensor and the triggering of the ECU.
Technical Product Description
22
Revision 1.0, 2014-05-21