P+H Drivers

[David Rhoads II]

Pasted below are the e-mail conversations with On Semiconductor
concerning use of the CS453/2 Injector drivers.  If I'm understanding
correctly, with a little caution, it appears that the CS453 can be used
to drive any type of injector.

Here are the e-mail conversations with On Semiconductor.
ROUND 1.........................
Hello Mr. Rhoads,

I will include below the exact text as I received it from the engineer
when
I inquired about these devices:
Here are the answers to your questions.
1)  The decision on which part depends on the fuel injectors to be used.

The ONLY difference between the parts is the CS452 has a typical peak
current of 2.4A, and a sustaining current of 0.6A while the CS453 has a
peak
current of 4.4A, and a sustaining current of 1.12A.  The customer
requirements for these electrical specs dictate which part to use.
2)  There are no timers on these IC's.  Any time delays called out in
the
spec are switching delays in the circuit.
3)  They are single stage parts.  That is, the same driver is used for
both
modes of operation (Ipeak, and Isus).
4)  Current limit is accomplished by sensing a voltage drop internally
across a resistor, and comparing it to an on-chip voltage reference.
If we can be of any further assistance with this matter or any other,
please
feel free to contact us via our website at www.onsemi.com or by
telephone at
(800) 282-9855.
Regards,
Casey D. Clarke
ON Semiconductor Technical Specialist


Contact Name: David Rhoads
Company Name: APPLIED DYNAMICS INTL
City/State:   ANN ARBOR MI, MI
Phone Number: (734) 973-1300 x274
Email:        rhoads at adt.com

Product: CS452GT5
PTI:     PNBD

Description of customer's question:

Has data sheets for both devices. Application will be in fuel injection
system.  Customer has same  questions regarding the both  devices.
1.Which part is more appropriate for use in driving multiple fuel
injectors?
2. Is the peak to hold transition,  timed or current sensed?
3. Are the devices single or two stage parts
4. When device tripped into a hold state, how is the current limited.

ROUND 2...........................
Hello Mr. Rhoads,

I will include the engineers response below:

If you are not going to reach the threshold of reduced current, you will
be
dissipating additional power across your load.  The CS452/3 is acting as
a
saturated switch.  You have to determine if this is a good thing or a
bad
thing.  The 452/3 will handle the current (DC).  Just keep an eye on the
die
temperature at all times.  You should keep it under 125C.

question#4
The device has an internal sense resistor who's voltage is internally
compared with an op amp.  The reference voltage tied to one input of the
op
amp is switched at the high current trip point.  It's all done DC.

If I can be of any further assistance, please contact me immediately at
(800) 282-9855 or respond to this e-mail

Regards,
Casey D. Clarke
ON Semiconductor Technical Specialist

Contact Name: David Rhoads
Company Name: APPLIED DYNAMICS INTL
City/State:   ANN ARBOR MI, MI
Phone Number: (734) 973-1300 x274
Email:        rhoads at adi.com

Product: CS452GT5
PTI:     PNBD

Description of customer's question:

The info you sent is helpful but not the main piece that I'm looking
for.

What I really need to know is can either the CS453 or CS452 be used to
drive
all
injectors (TBI, TPI/MPI, Peak & Hold, saturated) and what are the pros
and
cons
of doing so?  It seems to me that using the CS453 would handle all of
these
injector types with the possible setback of having to dissipate more
power
in
the lowest impedance injectors.  The higher impedance Saturated
injectors
would
simply never trip from the Peak state into the Hold state.  Is it
possible
to
damage the driver by using a saturated injector that would never allow
the
driver to trip into its hold state?

Something of lesser importance related to question #4: AFTER the driver
has
tripped into its Hold state, how is the current limited?  Is a different

series
resistance switched into the circuit within the driver or is the
base/gate
of
the internal transistor pulsed at a 25% duty cycle to provide the 25%
hold
current, and if so at what frequency?

Anxiously awaiting your response.
--
. David Rhoads II

HTH
--
. David Rhoads II
. Applied Dynamics International
. 3800 Stone School Road, Ann Arbor, Mi 48108
. (734) 973-1300
. rhoads at adi.com   web site:  http://www.adi.com


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