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:

INTOUT (Volts) =

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

+

×

×

FIGURE 3. SIMPLIFIED BLOCK DIAGRAM OF THE HIP9011 IN AN AUTOMOTIVE APPLICATION

GND

VMID

INTOUT

SO

SI

CH1IN

CH1FB

CH0FB

CH0IN

0.022

µF

MICROPROCESSOR

+5V

A/D

CONVERTER

OSCIN

OSCOUT

4MHz

TRANSDUCERS

HIP9011

TEST

INT/HOLD

CS

SCK

SPI BUS

CH0NI

CH1NI

20pF

20pF

1M

Ω

+5V

HIP9011