Recommendation For The External Capacitor C - Infineon TLE5501 Series User Manual

TLE5501
TMR-Based Angle Sensor
Transient behavior
For the time τ until the voltage settles to a value less than 0.5LSB from final value U
s
holds:
For a 12 bit ADC with N = 12, τ
This means that a waiting time of approx. 9 times of τ
can be converted with the ADC.
2.2

Recommendation for the external capacitor C

For most applications, it is a target to achieve a high angle accuracy. To reach this, the phase shift Φ between
the magnetic input signal and the bridge output shall be small. It can be estimated using
The external buffer capacitor C
phase shift Φ according to
For an application with 8000rpm, f
maximum buffer capacitor C
The time constant τ of the bridge in this case is τ
br
So the settling time of the bridge τ
For applications with higher speed, the buffer capacitor C
account, that there is also a capacitive load of the ADC of the microcontroller which needs to be charged.
Further details in Chapter
User's Manual
æ
τ s
= –
è
becomes τ = 9.0τ .
s s br
can be calculated depending on magnetic input frequency f
b
Equation (2.8):
C b
= 133Hz, R = 4kOhm (R = R
in
is calculated to C = 1nF.
b b
br
is then τ = 9τ
s s br
3.
0.5
æ ö ö
τ b r ⋅ ------ -
ln
è ø ø
N
2
should be considered for settling the signal before it
br
b
( ) Φ
tan
---------------- -
=
2πRf
in
/2, see
TMR
= R /2 x C = 4kOhm x 1nF = 4µs.
TMR b
= 36µs.
can be further reduced but it has to be taken into
b
9
the following relation
0
Equation (2.3).
and desired
in
Chapter 2.1) and Φ = 0.2° the
2019-04-29
(2.7)
(2.8)
Rev. 1.0