mlx90316 Melexis Company, mlx90316 Datasheet - Page 20

• Manufacturer Part Number: mlx90316
• Description: Rotary Position Sensor Ic
• Manufacturer: Melexis Company

14.4. Sensor Front-End
14.4.1. HIGHSPEED Parameter
The HIGHSPEED parameter defines the main frequency for the DSP.
For better noise performance, the Slow Mode must be enabled.
14.4.2. ARGC, AUTO_RG, RoughGain Parameters
AUTO_RG and ARGC parameters enable the automatic gain control (AGC) of the analog chain. The AGC
loop is based on
and it targets an amplitude of 90% of the ADC input span.
At Start-Up phase, the gain stored in the parameter RoughGain is always used. Depending of the
AUTO_RG and ARGC settings, the AGC regulation acts as follow:
The parameter AUTO_RG activates the automatic regulation during normal operation of the device as
background task.
Melexis strongly recommend to set ARGC = “1”, AUTO_RG = “1” and RoughGain ≤ 3 for all types of
application. If the magnetic specifications of the application are well known and under control, the
appropriate RoughGain can also be programmed with ARGC set to “0” and AUTO_RG to “1”.
Please note that the angular errors listed in the section 10 are only valid if the AUTO_RG is activated.
AUTO_RG avoids also the saturation of the analog chain and the associated linearity error.
The current gain (RG) can be read out with the PTC-04 and gives a rough indication of the applied
magnetic flux density (Amplitude).
3901090316
Rev. 003
•
•
•
•
•
HIGHSPEED = 0 selects the Slow mode with a 7 MHz master clock.
HIGHSPEED = 1 selects the Fast mode with a 20 MHz master clock.
If ARGC is set, the regulation proceeds by jump to reach the target gain. Note that this regulation
is only valid if the starting gain does not saturate the ADC. Melexis recommendation is to use
RoughGain ≤ 3 if ARGC=1.
If ARGC is “0” and AUTO_RG is set to “1”, the regulation adapts every cycle by one gain code the
current gain to reach the 90% ADC span target. Note that if the value of RoughGain is too far
from the actual gain, the chip will enter the normal operating mode (after the Start-Up phase) with
an incorrect gain which will cause the device to go in diagnostic low (field too low/field too high –
See section 15).
If ARGC and AUTO_RG are “0”, the AGC regulation is off and the gain used is the value stored in
the parameter RoughGain. Melexis does not advise the use of this mode.
HIGHSPEED
RoughGain
Parameter
AUTO_RG
RGThresH
RGThresL
ARGC
(V
X
)²+ (V
Y
)² = (Amplitude)² = (Radius)²
Page 20 of 41
0 = Slow mode
1 = Fast mode
0 = disable
1 = enable
0 = disable
1 = enable
0 … 15
0 … 15
0 … 15
Value
Rotary Position Sensor IC
Unit
MLX90316
Data Sheet
April 07