HIP9011EVAL1Z Intersil, HIP9011EVAL1Z Datasheet - Page 2

• 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: -

Operation of the Signal Processing IC
Inputs from one or two piezoelectric sensors mounted on the
engine block are capacitively coupled to the inputs of the
operational amplifiers within the HIP9011. Two sensors are
shown in the examples in this application note, one for each
side of a “V” type of engine configuration. Engines configured
in-line may use sensors placed on either end of the engine
block. Often only one sensor is used by strategically locating a
point where optimum signal output is available. The ability of
this IC to have programmable gain changes at each ignition
pulse can help with these configurations. In some high end
applications two HIP9011 are used.
The input coupling capacitor and series input resistors to the
inverting input of the operational amplifiers within the HIP9011
serve as a high pass filter to reduce low frequency components
from the transducer. AC coupling also has the advantage of
reducing the possibility of driving the output of the input
amplifier towards the positive supply with increased leakage
resistance of the transducer or environment with time. Leakage
resistance to ground will pull the inverting input of the
operational amplifier to ground, thus forcing its output high. The
non-inverting input of the HIP9011 is not committed, but in most
applications, it is usually returned to the mid supply voltage,
available as an output terminal of the device.
A signal from the engine’s microcontroller determines which
transducer input signal will be processed by the HIP9011
operational amplifier for each ignition pulse by toggling the
transmission gate on the output of these amplifiers. From here
the signal is applied to an anti aliasing filter within the HIP9011.
This filter excludes input signals above 20kHz from passing on
to the following switched capacitor filter and gain stages.
Signals above 20kHz could cause problems with the 200kHz
clocking frequency of the switched capacitor filters and
amplifiers. A filter channel is provided in the HIP9011, with a
tuning range from 1.22kHz to 19.98kHz, in 64 steps. Serial
control signals are sent via the SPI bus to the HIP9011 by the
microcontroller. These control signals set the filter frequencies
within these ICs.
CH0FB 18
CHIFB 17
CH0IN 19
CH0NI 20
CH1IN 16
CH1NI 15
FIGURE 2. SIMPLIFIED BLOCK DIAGRAM OF THE HIP9011, SINGLE CHANNEL KNOCK SIGNAL PROCESSING IC
-
+
-
+
VMID
2
POWER SUPPLY
BIAS CIRCUITS
3 VDD 1 GND
AND
PROGRAMMABLE
64 STEPS
2 - 0.111
STAGE
GAIN
2
Application Note 9770
PROGRAMMABLE
BANDPASS
64 STEPS
1 - 20kHz
FILTER
The output of the Filter Stage in the HIP9011 is applied to a full
wave rectifier and then to an integrator. The integrator operation
is initiated by the INT/HOLD signal from the microcontroller. It is
only during the rising edge of the INT/HOLD signal that the
integrator starts from its initial reset condition of 0.125V.
Integration is towards the positive supply when a knock signal
is present. Severity of the knock signal and the integrators
programmable time constant determines the final level. The
integrator time constant is programmable in 32 steps from 40μs
to 600μs. This time constant can be viewed as an output signal
attenuator. Again, the value of the time constant is set by the
SPI control signals from the microcontroller.
Immediately after the INT/HOLD signal goes low, the
integrators output signal, INTOUT is held in the HIP9011’s
output sample and hold circuit for the microcontroller’s A/D
converter to process. Figure 2 shows the block diagram of the
HIP9011. Figure 3 shows the waveforms for the integrator,
INTOUT on the top trace. The center trace shows the input
signal from a simulated pressure transducer mounted on the
cylinder. An expanded waveform of the simulated engine input
signal during the integration period is shown in the circled
display of Figure 3. The bottom trace shows the INT/HOLD
signal.
From this discussion we see that we have an IC that can detect
low levels of engine knock or ping by using bandpass filters,
rectification and an integration process. The gated integrator
allows the IC to only monitor engine noise during the time that
engine knock is expected to occur, thus, vastly reducing the
influence of background noise.
Integrator Operation
Observation of the integrator output signal, INTOUT, is
important to the setup and understanding of the operation of
this signal processing IC. This observation can be distorted by
instrumentation used to view the INTOUT signal. In Figure 5,
the upper waveform shows what looks like inaccuracies in the
INTOUT signal. This is due to aliasing of the oscilloscope
sampling system with only 500 samples. Not shown in this
FULL WAVE
TEST 14
RECTIFIER
TO SWITCHED
STATE MACHINE
ACTIVE
NETWORKS
CAPACITOR
REGISTERS
AND
PROGRAMMABLE
INTEGRATOR
40 - 600μs
32 STEPS
PROGRAMMABLE
DIVIDER
INTERFACE
SPI
TO SINGLE-ENDED
OUTPUT DRIVER
DIFFERENTIAL
CONVERTER,
SAMPLE AND
HOLD AND
CLOCK
November 6, 2006
OSCOUT 10
INT/HOLD 7
INTOUT 4
OSCIN 9
SCK 13
AN9770.1
SO 11
SI 12
CS 8