FPF2215 Fairchild Semiconductor, FPF2215 Datasheet - Page 11

• Manufacturer Part Number: FPF2215
• Description: IC LOAD SWITCH MICROFET6
• Manufacturer: Fairchild Semiconductor
• Type: High Side Switchr

Specifications of FPF2215

• Number Of Outputs: 1
• Rds (on): 325 mOhm
• Internal Switch(s): Yes
• Current Limit: Adjustable
• Voltage - Input: 1.8 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-MLP, 6-MicroFET™
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: FPF2215TR

FPF2213-FPF2215 Rev. C
Take note that this is below the maximum package power
dissipation, and the thermal shutdown feature will act as
additional safety to protect the part from damage due to
excessive heating. The junction temperature is only able to
increase to the thermal shutdown threshold. Once this
temperature has been reached, toggling ON will not turn-on the
switch until the junction temperature drops. For the FPF2215, a
short on the output will cause the part to operate in a constant
current state dissipating a worst case power of:
This large amount of power will activate the thermal shutdown
and the part will cycle in and out of thermal shutdown so long as
the ON pin is active and the short is present.
PCB Layout Recommendations
In order to benefit from adjustable, high-precision load switch
devices, a high-precision R
current limit tolerance.
determined by the voltage drop across the R
layout can introduce parasitic noise on the I
minor variation of I
noise coupling mechanisms from I
minimized. This becomes more critical when I
to the nominal load current operation where parasitic effects
could cause the device to go in and out of current limit and
result in an error flag report.
Care must be taken to provide a direct current return path
between the R
(pin5). Please see current pad #2 in figure below.
Figure 22: Eliminate parasitic noise of ISET-GND by providing a
separate ground route, unique from the power ground plane
Improving Thermal Performance
An improper layout could result in higher junction temperature
and triggering the thermal shutdown protection feature. This
concern applies when the switch is set at higher current limit
value and an over-current condition occurs. In this case, the
power dissipation of the switch, from the formula below, could
exceed the maximum absolute power dissipation of 1.2W.
P
PD = (V
1)Power current path
2)RSET current path
(Max)
= V
IN
IN (MAX)
- V
SET
OUT
LIMIT
ground pad and the device ground pad
) x I
* I
. To improve the I
LIM (MAX)
LIM (Max)
Since I
SET
value must be used to set a tight
= 5.5 * 0.276 = 1.5W
LIMIT
SET
(current limit value) is
LIMIT
SET
to GND must be
SET
stability, parasitic
LIMIT
pin resulting in a
, a poor PCB
is set close
11
The following techniques have been identified to improve the
thermal performance of this family of devices.
techniques are listed in order of the significance of their impact.
1. Thermal performance of the load switch can be improved by
connecting pin7 of the DAP (Die Attach Pad) to the GND plane
of the PCB.
2. Embedding two exposed through-hole vias into the DAP
(pin7) provides a path for heat to transfer to the back GND
plane of the PCB. A drill size of Round, 14 mils (0.35mm) with
1-ounce copper plating is recommended to result in appropriate
solder reflow. A smaller size hole prevents the solder from
penetrating into the via, resulting in device lift-up. Similarly, a
larger via-hole consumes excessive solder, and may result in
voiding of the DAP.
Figure 23: Two through hole open vias embedded in DAP
Figure 24: X-Ray result (bottom view with 45
3. The V
generated during a high load current condition. Using wide
traces will help minimize parasitic electrical effects along with
minimizing the case to ambient thermal impedance. The layout
suggested in Figure 25 provides each pin with adequate copper
so that heat may be transferred as efficiently as possible out of
the device. The low-power FLAGB and ON pin traces may be
laid-out diagonally from the device to maximize the area
available to the ground pad.
capacitors as close to the device as possible also contributes to
heat dissipation, particularly during high load currents.
IN
, V
OUT
and GND pins will dissipate most of the heat
Placing the input and output
o
angle)
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