TLE4953 Datasheet, PDF (7/20 Pages) Infineon Technologies AG – Differential Two-Wire Hall Effect Sensor IC

TLE4953
TLE4953C
NS ^N
S
S
N
N
SNS
DR-L
DR-R
G 0415 S
53C1R
AEA03193
Figure 4 Definition of Rotation Direction
Circuit Description
The circuit internally is supplied by a voltage regulator. A 2 MHz on-chip oscillator serves
as a clock generator for the DSP and the output encoder.
Speed signal circuitry
TLE4953 speed signal path comprises a pair of Hall Effect probes, separated from each
other by 2.5 mm, a differential amplifier including noise limiting low-pass filter, and a
comparator triggering a switched current output stage. An offset cancellation feedback
loop is provided through a signal-tracking A/D converter, a digital signal processor
(DSP), and an offset cancellation D/A converter.
Uncalibrated Mode
Occasionally a short initial offset settling time t_d,input might delay the detection of the input
signal. (The sensor is "blind"). During the startup phase (un-calibrated mode) the output
is disabled (I = I_Low). The magnetic input signal is tracked by the speed ADC and
monitored within the digital circuit. For detection the signal needs to exceed a threshold
(digital noise constant d1). When the signal slope is identified as a rising edge, a trigger
pulse is issued to a comparator. A second trigger pulse is issued as soon as the next
rising edge is detected.
Between the start-up of the magnetic input signal and the time when its second extreme
is reached, the PGA (programmable gain amplifier) will switch to its appropriate position.
This value is determined by the signal amplitude and initial offset value. The digital noise
constant value is changing accordingly (d1 → d2, related to the corresponding PGA
Data Sheet
4
V 4.0, 2010-04