mc33293atv Freescale Semiconductor, Inc, mc33293atv Datasheet - Page 14

• Manufacturer Part Number: mc33293atv
• Description: Quad Side Switch
• Manufacturer: Freescale Semiconductor, Inc

that will cause the onset of current limit are: I DS(limit) , V load ,
and R DS(on) , as shown below.
For the case when: V load = 14 V
an over-current condition will be detected for any load
resistance such that R load
limit condition will occur any time 2.6
that the undetected current limit range is quite small.
Fault Interrogation
Status Output pin for reporting three different fault conditions,
a real time interrogation routine can be used to determine
which one of the three Fault conditions is being reported and
which single output is affected.
only one fault on a single output can be interpreted. In other
woRDS, if more than one over-current or open-load Fault
exists among the four outputs, it is not possible to distinguish
which outputs have a fault and which do not. It is very
unlikely, however, that more than one output will be faulted at
the same time.
is an over-current or open-load Fault (R load
typical). This is done by taking all the inputs (single or dual) to
a logic low state. If the Fault Status resets (changes to a
logic high state) after the Fault Status Reset Delay Time
(t s(reset), see Figure 4) has lapsed, then an over-current Fault
is being reported. If the Fault Status does not reset (remains
14
The factors that determine the value of load resistance
Even though the MC33293A incorporates a single Fault
An important point to note about Fault interrogation is that
When a Fault is reported, the first step is to determine if it
R load(limit) = [V load / I DS(limit) ] – R DS(on)
V OC(limit) = 3.7 V
R DS(on) = 0.3
I DS(limit) = 4.0 A
2.6
. An undetected current
R load 3.2 . Notice
447 k ,
MC33293A
(13)
at a logic low state) after t s(reset) has lapsed, then an
open-load Fault (R load
This type of interrogation is possible because an output-off
open-load Fault can only be reported when all the inputs are
in a logic low state.
which single output is affected. After all inputs are turned
OFF and the fault status resets, each input is then turned ON
then OFF sequentially. A Fault will again be reported when
the input to the corresponding Over-Current output is turned
ON and t os(on) has lapsed. If the dual input mode is being
used, an over-current Fault can only be interrogated down to
the two outputs being driven together.
interrogation, all inputs are turned OFF and the fault status
remains set.
sequentially. The Fault status will remain set when the input
to the corresponding faulted output is turned ON and t os(on)
has lapsed. If the dual input mode is used, an open-load Fault
can only be interrogated down to the two outputs driven
together.
of R open(on) is 187 . From the example following Equation
6, the typical value of R open(off) is 447 k . Therefore, if the
load resistance is between 187
output-on open-load Fault will be reported at the Fault Status
output but an output-off open-load Fault will not. This
condition is referred to as a soft open fault . If a soft open fault
exists, it is reported at the Fault Status output the same as an
over-current Fault except for the reporting delay time. A soft
open fault has a reporting delay time of 2.2 ms typically, and
an over-current Fault has a reporting delay time of only 55 s
typically, after the input to the faulted output is turned ON.
For an over-current Fault, the next step is to determine
For an open-load Fault (R load
From the example following Equation 1, the typical value
Each input is then turned ON and OFF
MOTOROLA ANALOG IC DEVICE DATA
447 k , typical) is being reported.
and 447 k
447 k , typical)
typically, an