MLX90316KDC-BDG Datasheet, PDF (22/45 Pages) Melexis Microelectronic Systems – Rotary Position Sensor IC

MLX90316
Rotary Position Sensor IC
14.4. Sensor Front-End
Parameter
HIGHSPEED
ARGC
AUTO_RG
RoughGain
RGThresL
RGThresH
Value
Unit
0 = Slow mode
1 = Fast mode
0 = disable
1 = enable
0 = disable
1 = enable
0 … 15
0 … 15
0 … 15
14.4.1. HIGHSPEED Parameter
The HIGHSPEED parameter defines the main frequency for the DSP.
• HIGHSPEED = 0 selects the Slow mode with a 7 MHz master clock.
• HIGHSPEED = 1 selects the Fast mode with a 20 MHz master clock.
For better noise performance, the Slow Mode must be enabled.
14.4.2. ARGC, AUTO_RG, RoughGain and FORCECRA75 Parameters
AUTO_RG and ARGC parameters enable the automatic gain control (AGC) of the analog chain. The AGC
loop is based on
(V_X)²+ (V_Y)² = (Amplitude)² = (Radius)²
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:
• 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.
The parameter AUTO_RG activates the automatic regulation during normal operation of the device as
background task.
The parameter FORCECRA75 modifies the target of the AGC algorithm to 75% - instead of 90% - of the
ADC span (at start-up and in normal operation).
3901090316
Rev10
Page 22 of 45
Jul/13