AN2159 Datasheet, PDF (6/8 Pages) STMicroelectronics – SPI protocol for STPM01/STPM10 metering devices

Application Note
Freescale Semiconductor, Inc.
25
20
Ignition Advance ¹⁵
Angle (degree)
10
5
Low RPM
Throttle:
0 to 25%
26 to 50%
51 to 100%
High RPM
0
01234567
Speed (RPM × 1000)
Figure 7. Example of Ignition Advance Characteristics
The period of pulses (positive and negative) generated from pulser (mounted
on the magneto) is proportional to the engine speed. The pulses then passes
through the signal shaping circuit to be converted to the MCU input level. The
MCU then captures these pulses to calculate the output ignition angle. The HT
primary coil is charged prior to the ignition pulse. The ignition timing diagram is
shown in Figure 8.
Pulser pulses
Positive pulse
(Advance)
Negative pulse
(Reference pulse)
Filtered pulses
to MCU
T_d
Ignition pulses
from MCU
T_t
Coil charge period
Switch on IGBT
Switch off IGBT
(Ignition instance)
T_d = Delay value calculated with respect to positive pulse (Advance)
T_t = Time period (in seconds)
1
Engine RPM =
× 60
T_t
Figure 8. Ignition Advance Waveforms
AN2159
6
MOTOROLA
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