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TLE5501
TMR-Based Angle Sensor
Transient behavior
2
Transient behavior
For the sine and cosine output pins, it is also recommended to use a buffer capacitor C
As the device itself has a high output impedance, given by the TMR resistors R
a low-pass filter together with the bridge resistivity.
2.1
Bandwidth of the TMR bridge
It has to be taken into account that the low pass filter limits the bandwidth of the sensor and increases step
response time.
Figure 5
resistivity of a TMR resistor R
Figure 5
Schematic of one branch of the TMR bridge with external buffer capacitor C
The result of a pSPICE simulation of this output structure is shown in
capacitor value of C
= 1nF is assumed. Applying a voltage step of 5V on the supply V
b
compared with analytical simulations using below
The time constant for the bridge τ
A good approximation of the transient behavior in the analytical calculation can be achieved with R = 4kΩ and
C
= 1nF, so R in the analytical simulation is half of the resistivity of one TMR resistor R
b
This behavior is equal to a low-pass filter at the sensor output with R = R
User's Manual
shows a schematic of the sensor output structure with an external capacitor C
is specified in the datasheet and has a value between 4kΩ and 8kΩ.
TMR
VDD
R
TMR
R
TMR
GND
U t ( )
=
is defined as: τ
br
U_out
C
b
Figure
Equation
(2.1):
t τ ⁄
–
(
)
U
1 e
–
0
= RC, U
is taken to be 2.5V = VDD/2.
br
0
TMR
5
for filtering purpose.
b
, this buffer capacitor builds
TMR
b
6. A resistor of R
= 8kΩ and a
TMR
is simulated. This is
DD
of the bridge.
TMR
/2 and C
.
b
. The
b
(2.1)
Rev. 1.0
2019-04-29
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