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6
FN4367.2
January 6, 2006
Description of the HIP9011 Operation
This IC is designed to be a universal digitally controlled, analog
interface between engine acoustical sensors or accelerometers
and internal combustion engine fuel management systems.
Two wideband input amplifiers are provided which will allow the
use of two sensors. These sensors be of the piezoelectric type,
that can be mounted in optimum locations on either in-line or V
type engine configurations.
Output from these input amplifiers are directed to a channel
select mux switch and then into a 3rd order antialiasing filter.
The output signal is then directed to two programmable gain
stages, where one stage inverts or shifts the knock signal 180
degrees. The gain stage signals are outputted to two
programmable bandpass filter stages. Outputs from the two
BPF stages are then full wave rectified before being digitally
integrated by the programmable integrator. The integrator
output is applied to a line driver for further processing by the
engine fuel management control system. The gain, bandpass
filter and integrator stage settings are programmable from a
microprocessor via the SPI Bus Interface
Broadband piezoelectric ceramic transducers used for the
engine signal pickup have device capacitances in the order
of 1100pF and output voltages that range from 5mV to 8V
RMS. During normal engine operation, a single input
channel is selected and applied to the HIP9011. The engine
background noise is typically well below in amplitude than
the pre-detonation noise. Therefore, the bandpass filter
stages can be optimized to further discriminate between
engine background and combustion noise and pre-
detonation noise.
A basic approach to engine pre-detonation systems is to
only observe engine background during the time interval
that noise is expected and if detected, retard timing. This
basic approach does not require the sensitivity and
selectivity that is needed for a continuously adjustable
solution. Enhanced fuel economy and performance is
obtainable when this IC is coupled with a microprocessor
controlled fuel management system.
EXAMPLE CASE USING IDEAL SYSTEM EQUATION
Where:
VIN = 200mVP-P, Continuous AC Signal
GIN = 1.0, Ratio of RF to RIN
GPR = 0.190
GBPF = 2.0 Ideal Gain Value
tC = 200s
tINT =2ms
GDSE = 2.0 Ideal Gain Value
VRESET = 0.125V, Typical Value
INTOUT (Volts) =
200x10-3*1* [2 * 0.19 * 0.318 * 2x10-3/200x10-6*
2]+0.125
= 0.4833 + 0.125
= 0.608V
INTOUT (Volts) =
V
IN
G
IN
G
BPR
G
PR
1
π
---
t
int
t
c
--------
×
G
DSE
×
V
RESET
+
×
When the Input Signal is Present for the Period tINT:
FIGURE 3. SIMPLIFIED BLOCK DIAGRAM OF THE HIP9011 IN AN AUTOMOTIVE APPLICATION
VDD
GND
VMID
INTOUT
SO
SI
CH1IN
CH1FB
CH0FB
CH0IN
0.022
F
MICROPROCESSOR
+5V
A/D
CONVERTER
OSCIN
OSCOUT
4MHz
TRANSDUCERS
HIP9011
TEST
INT/HOLD
CS
SCK
SPI BUS
CH0NI
CH1NI
20pF
1M
Rin
RF
Rin
+5V
HIP9011