IPS maximum output current capability consideration

Application Note AN- 1181
IPS maximum output current capability
consideration
By Andre MOURRIER
Table of Contents
Page
Introduction .......................................................................................... 2
How does a quick comparison? ........................................................... 2
How does the calculation? ................................................................... 3
Comparison table ................................................................................ 4
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Topics Covered:
Maximum output current capability
 Introduction
 Quick comparison methodology
 Calculation & Result
 Comparison
Introduction
One of the key parameter to choose an IPS is the
maximum output current capability. All component
suppliers provide this information but each supplier has
different conditions:
How does a quick comparison?
The maximum continous output current capability
depends of two types of parameters:
 Application parameters (ex. Maximum ambiant
temperature …).
 Component characteristics (ex. Rdson …)
The application parameters are given for a typical
application and identical for the comparison. So the
component characteristics are the most relevant for this
type of comparison. This is the equation to calculate the
maximum output current capability:
Equation 1:
√
As an example this is the number given by the
datasheet given for the BTS723G:
Where:
And as a comparison this is theAUIPS7142G from IR:
Iout(max) is the maximum output current to be sure that
at ambiant temperature equal to Ta, the junction
temperature will never reach the Tj.
Ta is the ambient temperature
Tj is the junction temperature during the regular
operation.
As a first result the BTS723G seems have more output
current capability than the AUIPS7142G. But a result is
nothing without its conditions: need to compare apple
with apple.
Rdson(@Tj) is the ON state resistance of the power
MOSFET at Tj temperature.
Rth is the static thermal resistance from junction to
ambiant.
Tj and Ta are the application parameters, so they are
This is the conditions for the BTS723G
This is the conditions for the AUIPS7142G
define the limit and the condition of use. To do a quick
comparison, these parameters are considered as
identical for the both component.
Regarding the equation if we remove these two
application parameters, the comparison Rth and Rdson
must be enough. Because these values are in the
denomitor, lower are these two values, higher is the
output current capabilty.
Take a quick look to our example, first the Rdson:
BTS723G:
AUIPS7142G:
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With the same condition, Iout = 2A for the maximum
value, the Rdson of the AUIPS7142G is better than the
AUIPS7142G.
Now take a look to the Rth parameters:
The BTS723G:
As we have determined in previous quick analysis, the
AUIPS7142G output current capability is better than the
BTS723G. Now, the calculation is done for the two
channels in parallel. We will use the same way to
calculate but the current in each channel is divided by
2. So the power dissipated by each channel is also
divided by 2. Then multiply by two the current for the
two channels:
√
Always take care to the small note for the conditions:
For the BTS723G:
√
The AUIPS7142G:
For the AUIPS7142G:
√
With the same conditions, the two Rth are equivalent:
45°C/W.
As conclusion, even if at the first look, the output
current of the BTS723G seems higher than the
AUIPS7142G after a quick analysis it is not true.
Because other parameters are equivalent and the
Rdson of the AUIPS7142G is better than the BTS723G
so the output current capabality of the AUIPS7142G is
higher.
How does the calculation?
Where:
Iout(total max) is the maximum of the channel1 + channel2
As shown, the first evaluation, the AUIPS7142G has
more output current capability than the BTS723.
Finally, the calculation is done for the two channels not
in parallel but activated in same time. We will use the
same way to calculate but with the two channels
activated the maximum output current is divided by two:
The first quick analysis show that the output capability
of the IR device is better than the competitor but how
much is it better?
For that use the equation 1 and replace parameters
name by the numeric values:
√
For the BTS723G:
√
√
For the AUIPS7142G:
For the BTS723G:
√
√
As shown, the first evaluation, the AUIPS7142G has
more output current capability than the BTS723.
For the AUIPS7142G:
√
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Comparison table
Part number
BTS723G
AUIPS7142G
BTS723G
AUIPS7142G
BTS724G
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Nb
channel
1
2
4
Rth
in
°C/W
45
45
41
40
34
Tj in
°C
Tambient
in °C
[email protected]°C
in Ohm
85
85
85
85
85
0,21
0,18
0,21
0,18
0,18
150
150
150
150
150
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Imax in
A
2,62
2,83
3,89
4,25
2,30
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