HIP9011EVAL1Z Intersil, HIP9011EVAL1Z Datasheet - Page 4

• Manufacturer Part Number: HIP9011EVAL1Z
• Description: BOARD EVALUATION FOR HIP9011
• Manufacturer: Intersil

Specifications of HIP9011EVAL1Z

• Main Purpose: Special Purpose, Engine Knock Signal Processor
• Utilized Ic / Part: HIP9011
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -

The codes written by the computer for each function are
displayed on the lower right side of the display. Multiple
settings may easily be obtained by opening more windows
with different settings and clicking with the mouse on the
desired window, to activate the desired setting.
Figure 13 through Figure 17 shows the writing sequence to
the knock processing IC by the computer for various settings
of the knock signal processing ICs.
Open Knock Sensor Detection
One means to detect an open sensor is to couple a low level,
low frequency AC signal to the amplifier input. If the coupling
capacitor value carrying this signal is small compared to the
capacitance of the piezoelectric transducer, the coupled
signal will be attenuated. To a first order, this would be the
capacitance ratio Ccoupling/Csensor. Moreover, if the low
level signal’s frequency is below the normal spectrum of
engine signals it will be further attenuated by the bandpass
filters. To accomplish this function on the Evaluation Board,
two terminals are provided. One is marked 900Hz, while the
other is the ground return for that signal. When the
piezoelectric transducer is removed from the input circuit,
the previously attenuated 900Hz signal will become large
and drive the IC’s input operational amplifier to full output,
which will produce higher frequency components that will
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FIGURE 4. RESPONSE OF ONLY THE FILTERS WITHIN THE HIP9011
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look like a severe knock signal that can not be handled by
the control system. Software would then retard the timing to
a minimum that would allow the engine to function, but at a
lower efficiency level. Service would be required to restore
normal engine operation.
Another Open Knock Sensor Approach with a
Software Algorithm
The main focus of this method to detect sensor disconnect is
based on exploiting the re-programmability of the gain stage
within the IC. If a user reprograms the gain stage, for
example, at every 5th engine revolution for an open sensor
condition, the response time and accuracy of the feedback
knock sensor control should not impair the engine
performance over most of the entire engine speed range.
The approach is to adjust the GAIN stage prior to supplying
the knock signal to the Band Pass Filter stage. To determine
the sensor disconnect threshold value for the knock sensor
system, the gain would be reduced to the lowest
programmable level. This would then provide a signal
level/reference value closest to that produced by a sensor
that was disconnected.
Then with the GAIN stage programmed to a more
normal/frequent operating value, should a sensor become
disconnected, the INTOUT signal level would drop to a level
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November 6, 2006
AN9770.1