SIP4282A Vishay, SIP4282A Datasheet - Page 8

• Manufacturer Part Number: SIP4282A
• Description: Vishay Power Ics 1.2 A Slew Rate Controlled Load Switch In Ppak Sc75
• Manufacturer: Vishay

SiP4282A
Vishay Siliconix
Protection Against Reverse Voltage Condition
The P-Channel MOSFET pass transistor has an intrinsic
diode that is reversed biased when the input voltage is
greater than the output voltage. Should V
this intrinsic diode will become forward biased and allow
excessive current to flow into the IC thru the V
potentially damage the IC device. Therefore extreme care
should be taken to prevent V
In conditions where V
parallel with the internal intrinsic diode is recommended to
protect the SiP4282A.
Thermal Considerations
The SiP4282A is designed to maintain a constant output load
current. Due to physical limitations of the layout and
assembly of the device the maximum switch current is 1.2 A,
as stated in the ABS MAX table. However, another limiting
characteristic for the safe operating load current is the
thermal power dissipation of the package. To obtain the
highest power dissipation (and a thermal resistance of 90 °C/
W) the power pad of the device should be connected to a
heat sink on the printed circuit board.
The maximum power dissipation in any application is
dependant on the maximum junction temperature, T
= 125 °C, the junction-to-ambient thermal resistance for the
SC-75 PPAK package, θ
temperature, T
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon
Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and
reliability data, see
www.vishay.com
8
P
(max)
=
T
J
A
http://www.vishay.com/ppg?74480.
(max)
, which may be formulaically expressed as:
θ
J
−
A
OUT
−
T
J-A
A
exceeds V
OUT
=
= 90 °C/W, and the ambient
125
from exceeding V
90
−
IN
T
a Schottky diode in
A
OUT
exceed V
OUT
IN
pin and
.
J(MAX)
IN
,
It then follows that, assuming an ambient temperature of
70 °C, the maximum power dissipation will be limited to about
610 mW.
So long as the load current is below the 1.2 A limit, the
maximum continuous switch current becomes a function two
things: the package power dissipation and the R
ambient temperature.
As an example let us calculate the worst case maximum load
current at T
occurs at an input voltage of 1.8 V and is equal to 480 mΩ.
The R
using the following formula
R
Where T
we have
R
= 551 mΩ
The maximum current limit is then determined by
which in case is 1.05 A. Under the stated input voltage
condition, if the 1.05 A current limit is exceeded the internal
die temperature will rise and eventually, possibly damage the
device.
I
LOAD
DS(ON)
DS(ON)
(max)
DS(ON
(at 70 °C) = R
(at 70 °C) = 480 mΩ x (1 + 0.0033 x (70 °C - 25 °C))
C
is 3300 ppm/°C. Continuing with the calculation
) at 70 °C can be extrapolated from this data
A
〈
= 70 °C. The worst case R
R
P
DS
(max)
(
ON
DS(ON)
)
(at 25 °C) x (1 + T
S-71378–Rev. B, 23-Jul-07
Document Number: 74480
DS(ON)
DS(ON)
C
x ΔT)
at 25 °C
at the