FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2 A
Adjustable Over-Current Protection Load Switches
Features
Description
The AccuPower™ FPF270X series is a family of
current-limit load switches that provide full protection to
systems and loads from excess current conditions.
Minimum current limit is adjustable from 0.4 A to 2.0 A.
The FPF270X contains a slew-rate-controlled N-channel
MOSFET and slew-rated turn-on to prevent power bus
disturbances from being caused by “hot plugging” loads
or momentary excess load demands. The input voltage
range is 2.8 V to 36 V. Loads can be activated or
deactivated with a low-voltage logic-compatible ON pin.
Fault conditions can be monitored using the error flag
pin and/or the power-good pin.
2.8 V to 36 V Input Voltage Range
Typical RDS(ON)=88 m
0.4 A to 2 A Adjustable Current Limit (Min.)
Slew Rate Controlled
ESD Protected, above 2000 V HBM
Thermal Shutdown
Active LOW Enable
UVLO Protection
Power-Good Output
Applications
Each member of the FPF270X family serves a category
of load-fault response. All devices clamp the load
current so that it cannot exceed an externally
programmed current level. An over temperature feature
provides further device protection in case of excessive
levels of power dissipation.
Motor Drives
Digital Cameras
Consumer Electronics
Industrial
FPF2700 responds to an overload condition that lasts
longer than a fixed blanking period by turning off the
load, followed by a retry after the auto-restart time.
Computing
Hard Disk Drives
Telecom Equipment
FPF2701 responds to an overload condition that lasts
longer than a fixed blanking period by latching off the
load. The load remains off unless either the ON pin is
toggled or the input voltage cycles through UVLO.
Figure 1. MLP (Top View) Figure 2. MLP (Bottom View)
FPF2702 is intended to be used with external fault
management. Like the FPF2700 and FPF2701, it sets
the fault signal pin LOW when it activates current
clamping. This device is intended for applications where
external fault management coordinates the overload
response with the FPF2702.
The FPF270X is available in a space-saving, Lead and
Halogen free, 8-lead, MLP 3x3 mm and SO8 packages.
Figure 3. SO8 (Top View)
Ordering Information
Part
Number
Current Limit [A]
Current Limit
Blanking Time [ms]
Auto-Restart
Time [ms]
ON Pin
Activity
Package
FPF2700MPX
0.4 – 2.0
0.5
127.5
Active LOW
MLP3X3
FPF2701MPX
0.4 – 2.0
0.5
NA
Active LOW
MLP3X3
FPF2702MPX
0.4 – 2.0
NA
NA
Active LOW
MLP3X3
FPF2700MX
0.4 – 2.0
0.5
127.5
Active LOW
SO8
FPF2701MX
0.4 – 2.0
0.5
NA
Active LOW
SO8
FPF2702MX
0.4 – 2.0
NA
NA
Active LOW
SO8
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
December 2013
36 V MAX.
VIN
VOUT
ON
FLAGB
TO LOAD
OFF
ON
VIN
2.8 V – 36 V
100KΩ
100KΩ
COUT
CIN
ISET
PGOOD
RSET
GND
Figure 4. Typical Application
Block Diagram
IN
VDD
VREF
BGAP/BIAS
Reg
Current Limit
SOA Protection
Current Limit
UVLO
CONTROL
LOGIC
VREF
ON
THERMAL
PROTECTION
CHARGE
PUMP
ISET
VIN
OUT
VOUT
PGOOD
FLAGB
+
-
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Application Diagram
GND
Figure 5. Block Diagram
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
2
VOUT
8
1
VIN
FLAGB
7
2
PGOOD
VIN
1
8
VOUT
PGOOD
2
7
FLAGB
ISET
3
6
NC
ON
4
5
GND
GND
NC
6
3
ISET
GND
5
4
ON
Figure 6. MLP (Bottom View)
Figure 7. SO8 (Top View)
Pin Definitions
Pin #
Name
Description
1
VIN
2
PGOOD
Power-Good Output. Open-drain output to indicate that output voltage has reached 90% of
input voltage.
3
ISET
Current Limit Set Input. A resistor from ISET to ground sets the current limit for the switch.
4
ON
5
GND
6
NC
7
FLAGB
Fault Output. Active LOW, open-drain output that indicates current limit, under-voltage, or
over-temperature state.
8
VOUT
Switch Output. Output of the power switch.
Supply Input. Input to the power switch and the supply voltage for the IC.
ON Control Input. Active LOW.
Ground
No connection. Leave open or connect to ground.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Pin Configurations
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3
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only.
Symbol
Parameter
Min.
Max.
Unit
PGOOD, FLAGB, VIN to GND
-0.3
40
V
VOUT to GND
-0.3
VIN + 0.3
V
ON to GND
-0.3
6
V
(1)
MLP 3x3 , See Figure 8
1.25
PD
Power Dissipation (TA=25°C)
ISW
Maximum Continuous Switch Current
3.5
A
TJ
Operating Junction Temperature
-40
+125
°C
TSTG
Storage Temperature
-65
+150
°C
ESD
Electrostatic Discharge
Protection Level
Human Body Model, JESD22-A114
2000
Charged Device Model, JESD22-C101
2000
JA
Thermal Resistance,
Junction to Ambient
MLP 3x3 , See Figure 8
(1)
SO8 , See Figure 10
1.00
(1)
V
80
(1)
SO8 , See Figure 10
W
102
°C/W
Note:
1. Thermal resistance, θJA, is determined with the device mounted on a one inch square pad, 2 oz copper pad,
and a 1.5 x 1.5 in. board of FR-4 material.
2
Figure 8. 80°C/W Mounted on a 1in Pad
of 2-oz. Copper
Figure 9. 226°C/W Mounted on a Minimum Pad
of 2-oz. Copper
2
Figure 10. 102°C/W mounted on a 1in Pad
of 2-oz. Copper
Figure 11. 181°C/W Mounted on a Minimum Pad
of 2-oz. Copper
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance. Fairchild does not recommend exceeding them or
designing to Absolute Maximum Ratings.
Symbol
Parameter
Min.
Max.
Unit
VIN
Input Supply Voltage
2.8
36.0
V
TA
Ambient Operating Temperature
-40
85
°C
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Absolute Maximum Ratings
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4
VIN=2.8 to 36 V and TA=-40 to +85°C unless otherwise noted. Typical values are at VIN=12 V and TA=25°C.
Symbol
Parameter
Conditions
Min.
Typ.
Max. Unit
Basic Operation
VIN
Operating Voltage
IQ
Quiescent Current
VIN=12 V, VON=0 V, IOUT=0 A
ISHDN
Shutdown Current
VIN=36 V, VON=3.3 V, IOUT=0 A
TA=25°C, VIN=12 V
RON
On Resistance
2.8
36.0
V
92
140
μA
5
14
μA
88
114
TA=-40 to +85°C, VIN=12 V
140
TA=25°C, VIN=5 V
88
TA=-40 to +85°C, VIN=5 V
114
mΩ
140
VIH
ON Input Logic HIGH Voltage
VIN=2.8 to 36 V
VIL
ON Input Logic LOW Voltage
VIN=2.8 to 36 V
ILK
ON Input Leakage
VON=5.5 V or GND
ISWOFF
Off Switch Leakage
VIN=36 V, VON=3.3 V, VOUT=0 V
0.01
FLAGB Output Logic LOW Voltage
VIN=5 V, ISINK=1 mA
0.1
IFLAGB(HI)
FLAGB Output Logic HIGH Leakage
Current
VIN=36 V, Switch On,
VFLAGB=36 V
VPGOOD
PGOOD Trip Voltage
VIN=5 V, VOUT as Percent of VIN,
VOUT Rising
90
%
VPGOOD(HYS) PGOOD Hysteresis
VIN=5 V, VOUT as Percent of VIN,
VOUT Falling
3
%
VPGOOD(LO) PGOOD Output Logic LOW Voltage
VIN=5 V, ISINK=1 mA
VFLAGB(LO)
IPGOOD(HI)
PGOOD Output High Leakage
Current
VIN=36 V, Switch ON,
VPGOOD=36 V
Current Limit
TA=25°C
Short Circuit Current Limit
VOUT < 2 V, Switch in OverCurrent Condition
2.0
V
-1
0.1
0.8
V
1
μA
μA
0.2
V
1
μA
0.2
V
1
μA
+20
%
Protections
ILIM
ISC
TSD
UVLO
Thermal Shutdown
Under-Voltage Shutdown
-20
0.75 x
INOM
Shutdown Threshold
140
Return from Shutdown
110
Hysteresis
30
VIN Increasing
2.3
UVLO_HYST Under-Voltage Shutdown Hysteresis
2.5
A
°C
2.7
100
V
mV
Dynamic
tdon
Turn On Delay
tdoff
Turn Off Delay
tR
VOUT Rise Time
tF
VOUT Fall Time
tBLANK
tRESTART
tCLR
2.7
0.1
RL=500 Ω, CL=2 µF
ms
7.5
1.5
Over-Current Blanking Time
FPF2700/1, TA=25°C
0.25
0.50
0.75
ms
Auto-Restart Time
FPF2700, TA=25°C
63.8
127.5 191.2
ms
Current-Limit Response Time
VIN=12 V, VON=0 V
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
50
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Electrical Characteristics
μs
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VOUT
90
%
90
%
10
%
tR
10
%
tF
3.3
V
VON
50
%
50
%
90
%
10
%
VOUT
tdon
tdoff
tON = tR + tdon tOFF = tF + tdoff
Figure 12. Timing Diagram
Typical Performance Characteristics
VIN = 12 V and TA = 25°C.
1.40
1.80
TA = 25°C
V IN = 12V
1.70
1.38
On Threshold Voltage (V)
On Threshold Voltage (V)
1.60
1.35
V IH
1.33
1.30
V IL
1.28
1.50
1.40
V IH
1.30
V IL
1.20
1.10
1.25
1.00
1.23
0.90
1.20
0.80
0
5
10
15
20
25
30
35
40
-50
-25
0
25
Figure 13. ON Threshold vs. Supply
75
100
125
150
Figure 14. ON Threshold vs. Temperature
130
12
V ON = 0V
TA = 125°C
V ON = 5V
120
TA = 125°C
10
TA = 85°C
TA = 85°C
110
Quiescent Current (µA)
Quiescent Current (µA)
50
TJ, Junction Temperature (oC)
Supply Voltage (V)
TA = 25°C
100
90
TA = -40°C
80
8
TA = 25°C
6
TA = -40°C
4
2
70
60
0
0
5
10
15
20
25
30
35
40
0
Supply Voltage (V)
5
10
15
20
25
30
35
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Timing Diagram
40
Supply Voltage (V)
Figure 15. Quiescent Current vs. Supply Voltage (ON) Figure 16. Quiescent Current vs. Supply Voltage (OFF)
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
6
VIN = 12 V and TA = 25°C.
100
160
95
On Resistance (m)
On Resistance (m)
140
90
120
85
100
80
75
80
70
60
65
40
60
0
10
20
30
Supply Voltage (V)
-50 -25 0 25 50 75 100 o125 150
TJ, Junction Temperature ( C)
40
Figure 17. On Resistance vs. Supply Voltage
Figure 18. On Resistance vs. Junction Temperature
4.0
12
VIN = 12V
RL = 500
CL = 2µF
11
10
Rise Time (ms)
Turn-On Delay (ms)
3.5
3.0
9
2.5
8
7
2.0
6
1.5
5
4
1.0
-50
-25
0
25
50
75
100
125
150
-50 -25
TJ, Junction Temperature ( oC)
Figure 19. Turn-On Delay vs. Junction Temperature
0 25 50 75 100 125 150
TJ, Junction Temperature (oC)
Figure 20. Output Rise Time vs. Junction Temperature
0.15
Turn Off Delay Time (ms)
2.00
0.13
Fall Time (ms)
1.90
0.11
1.80
0.09
1.70
0.07
1.60
0.05
1.50
-50 -25 0 25 50 75 100 125 150
TJ, Junction Temperature (oC)
-50 -25 0 25 50 75 100 o125 150
TJ, Junction Temperature ( C)
Figure 21. Turn-Off Delay vs. Junction Temperature
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Typical Performance Characteristics
Figure 22. Output Fall Time vs. Junction Temperature
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When VOUT ILIM, FPF2702 Enters Constant Current Mode,
Removed (SOA Protection Followed by a Normal
Running at ILIM)
Operation, FPF2700 / FPF2701)
Note:
2. VOC signal forces the device into an over-current condition by loading a 500 m resistor to the output through
an NMOS. VOC is the gate drive of the NMOS.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
10
Description of Operation
Current Limiting
The FPF270X family of current limit load switches is
designed to meet the power requirements of a variety of
applications with wide input voltage range of 2.8 V to
36 V and adjustable current-limit value. The FPF270X
family offers control and protection while providing
optimum operation current for safe design practices.
The core of each switch is a typical 88 mΩ (VIN = 12 V)
N-channel MOSFET and a controller capable of
functioning over an input voltage range of 2.8 V to 36 V.
The current limit ensures that the current through the
switch doesn't exceed a maximum value while not
limiting at less than a minimum value. The current-limit
level is adjustable through an external resistor
connected between the ISET pin and GND.
The typical current limit level is adjustable from 510 mA
to 2.5 A. The minimum current limit (ILIM(MIN)) range is
from 0.4 A to 2.0 A, including 20% current-limit
tolerance. The FPF2700 and FPF2701 have a blanking
time during which the switch acts as a constant-current
source (Figure 27). If the over-current condition persists
beyond the blanking time, the FPF2700 latches off and
shuts the switch off (Figure 32). If the ON pin is kept
active, an auto-restart feature releases the switch and
turns the switch on again after the auto-restart time
(Figure 33). If the over-current condition persists beyond
the blanking time, the FPF2701 latch-off feature shuts
the switch off. The switch is kept off until the ON pin is
toggled or input power is cycled. The FPF2702 has no
current-limit blanking period, so it remains in a constantcurrent state until the ON pin is deactivated or the
thermal shutdown turns off the switch.
FPF270X offers adjustable current limiting, undervoltage lockout (UVLO), power-good indicator
(PGOOD), fault flag output (FLAGB), and thermal
shutdown protection. In the event of an over-current
condition, the load switch limits the load to the current
limit value. The current limit value for each switch can
be adjusted from 400 mA to 2 A through the ISET pin.
On/Off Control
The ON pin is active LOW for and controls the state of
the switch. Pulling the ON pin continuously to LOW
holds the switch in ON state. The switch moves into
OFF state when the ON pin is pulled HIGH. The ON pin
can be pulled HIGH to a maximum voltage of 5.5 V.
Besides the current-limiting functionality, the switch is
protected by the thermal shutdown protection and an
independent SOA protection circuit is available.
An under-voltage condition on the input voltage or a
junction temperature in excess of 140°C overrides the
ON control and turns off the switch. In addition, an overcurrent condition causes the switch to turn off in the
FPF2700 and FPF2701 after the expiration of the
blanking time. The FPF2700 has an auto-restart feature
that automatically turns the switch ON again after the
auto-restart time. For the FPF2701, the ON pin must be
toggled to turn the switch on again. The FPF2702 does
not turn off in response to an over-current condition; it
remains operating in Constant-Current Mode as long as
ON is enabled and the thermal shutdown or UVLO have
not activated. The ON pin does not have internal pulldown or pull-up resistors and should not be left floating.
SOA Protection Current Limit (IOUT > 12 A)
FPF270X has an SOA protection feature to protect the
load switch in response to current surges exceeding
12 A in normal operation. If a short-circuit event occurs
(IOUT>12 A), the switch is turned off in about 1µs by an
independent Safe Operating Area (SOA) protection
circuit (Figure 26, Figure 28). This feature protects the
switch in case of sudden, high-current events at the
output, such as a short to GND. The switch turns on
automatically after a turn-on delay of about 2.7 ms.
Short-Circuit Current Limit (VOUT < VSCTH = 2 V)
Fault Reporting
When the output voltage drops below the short-circuit
threshold voltage, VSCTH, the current-limit value reconditions itself to the short-circuit current limit value,
which is 75% of the nominal current limit (0.75 x ILIM,)
(Figure 24). This prevents early thermal shutdown by
reducing the power dissipation of the device. The V SCTH
value is set at 2 V. At about VOUT = 2.1 V, the switch is
removed from short-circuit current-limiting mode and the
current limit is set to the nominal current limit value.
Upon detection of an over-current condition, an input
UVLO, or an over-temperature condition, the FLAGB
signals the Fault Mode by activating LOW. In the event
of an over-current condition for the FPF2700 or
FPF2701, the FLAGB goes LOW at the end of the
blanking time (Figure 24 and Figure 25). FLAGB goes
LOW immediately for the FPF2702 (Figure 29). If the
over-current condition lasts longer than blanking time,
FLAGB remains LOW through the auto-restart time for
the FPF2700. For the FPF2701, FLAGB is latched LOW
and ON must be toggled to release it.
Setting the Current Limit Value
FPF270X has an adjustable 0.4 A to 2.0 A minimum
current limit set through an external resistor, R SET,
connected between ISET and GND. A precision RSET
value must be used, such as 1% tolerance or lower, to
minimize the total current limit tolerance of the system.
For FPF2702, FLAGB is LOW during a fault and
immediately returns HIGH at the end of the fault
condition. FLAGB is an open-drain MOSFET that
requires a pull-up resistor. The maximum pull-up voltage
is 36 V (Figure 29).
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Application Information
Use the following equation to calculate the value of the
resistor for intended typical current limit value:
During shutdown, the pull-down on FLAGB is disabled
to reduce current draw from the supply. A 100 kΩ pullup resistor is recommended in the application.
RSET (k)
277.5
I LIM (TYP ) ( A)
(1)
ILIM(TYP) is the typical current limit value based on a RSET.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
11
RSET Selection Guide
Power Good
Current Limit [A]
RSET
(k)
Min.
Typ.
Max.
111
2.00
2.50
3.00
20
124
1.79
2.24
2.69
20
147
1.51
1.89
2.27
20
182
1.22
1.52
1.83
20
220
1.01
1.26
1.51
20
274
0.81
1.01
1.22
20
374
0.59
0.74
0.89
20
549
0.40
0.51
0.61
20
FPF270X has a power good feature. The PGOOD pin is
an open-drain MOSFET that asserts HIGH when the
output voltage reaches 90% of the input voltage (Figure
26). A typical 3% PGOOD hysteresis is added to
PGOOD to prevent PGOOD from chattering as VOUT
falls near the PGOOD threshold voltage.
Tol. (%)
The PGOOD pin requires an external pull-up resistor
connected to an external voltage source compatible with
input levels of other chips connected to this pin.
PGOOD is kept LOW when the device is inactive. To
save current in the OFF state, the pull-up resistor of the
PGOOD pin can be connected to the output voltage
when there is no battery, provided that compatibility with
the input levels of other devices connected to PGOOD
is observed. A typical value of 100 kΩ is recommended
for the pull up resistor. When the power-good feature is
not used in the application, the PGOOD pin can be
connected to GND.
2.8
2.6
2.4
ILIMIT (A)
2.2
2.0
Thermal Shutdown
1.8
Thermal shutdown protects the die from internally or
externally generated excessive temperatures. During an
over-temperature condition; as the temperature
increases above 140°C, FLAGB is activated and the
switch is turned off.
1.6
1.4
1.2
1.0
0.8
0.6
When the die cools down sufficiently (die temperature
drops below the threshold level), the switch
automatically turns on again. To avoid unwanted
thermal oscillations, a 30°C (typical) thermal hysteresis
is implemented between thermal shutdown entry and
exit temperatures. Proper board layout is required to
prevent premature thermal shutdown (see Figure 38 for
thermal shutdown behavior on FPF2702).
0.4
0.2
0.0
100
200
300
400
500
600
RSET (k)
Figure 36. ILIM vs. RSET
Under-Voltage Lockout (UVLO)
The under-voltage lockout feature turns off the switch if
the input voltage drops below the under-voltage lockout
threshold. With the ON pin active (ON pin pulled LOW),
the input voltage rising above the under-voltage lockout
threshold causes a controlled turn-on of the switch
(Figure 37). The UVLO threshold voltage is set internally
at 2.5 V for VIN rising. The under-voltage lockout
threshold has a 0.1 V hysteresis.
ON
VIN
VOUT
2V
IOUT
ILIM
Thermal Cycling
Device cools off
ON
Over
current
condition
UVLO Threshold
Device Wake up
FLAGB
VIN
FLAGB
Figure 38. FPF2702 Thermal Shutdown Behavior
Rise time
10%VOUT
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Table 1.
90%VOUT
VOUT
Figure 37. Under-Voltage Lockout Performance
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
12
During extended output-short conditions, excessive
power dissipation occurs in the load switch. FPF2700
and PFP2701 are protected by turning off the load
switch after blanking time. FPF2702 has no blanking
time feature; please refer to Note 3.
It is possible to estimate the SOA for the two FPF2702
packages, MPX and MX, through their respective SOA
curves shown in Figure 39 and Figure 40. These curves
provide a reference on how long the load switch
survives under the worst-case scenario with minimum
(1)
pad size of one square inch.
Figure 39. FPF2702 MPX SOA
Figure 40. FPF2702 MX SOA
Note:
3. To protect FPF2702 from an extended short condition, additional protection must be implemented in the system
to protect the device. For example, the FLAGB and PGOOD signal can be used to monitor the short-circuit fault
condition. In applications where FPF2702 can be exposed to persistent short-circuit conditions, it should be used
only with external fault management control to protect the switch.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
SOA (FPF2702)
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13
Power Dissipation
To limit the voltage drop on the input supply caused by
transient inrush currents when the switch is turned on
into a discharged load capacitor or short-circuit; an input
capacitor, CIN, is recommended between the IN and
GND pins. The FPF270X features a fast current limit
response time (50 μs). During this period, the device
relies on the input capacitor to supply the load current. A
10 μF to 100 μF ceramic capacitor is adequate for CIN in
most cases. Larger CIN values may be required in highvoltage or high-current applications. An electrolytic
capacitor can be used in parallel to further reduce the
voltage drop.
During normal operation as a switch, the power
dissipation of the device is small and has little effect on
the operating temperature of the part. The maximum
power dissipation for the switch in normal operation
occurs just before the switch enters into current limit.
This may be calculated using the equation:
PD _ MAX( NormalOper ation) ( I LIM( Max ) )2 RON ( MAX )
The maximum junction temperature should be limited to
125°C under normal operation. Junction temperature
can be calculated using the equation:
Output Capacitor
TJ PD JA TA
A 0.1 μF to 1 μF capacitor, C OUT , should be placed
between the OUT and GND pins. This capacitor helps
prevent parasitic board inductances from forcing the
output voltage below ground when the switch turns
off. This capacitor should have a low dissipation
factor. An X7R Multilayer Ceramic Chip (MLCC)
capacitor is recommended.
where:
During startup, the total output current consists of both
the load current and the charge current of the output
capacitor. For the FPF2700 and FPF2701; if the total
output current exceeds the set current limit threshold
(determined via RSET) for longer than the blanking time,
the device may not be able to start properly. This
imposes an upper limit to the value of the output
capacitor, given the load current and the selected
current limit value. COUT should not exceed the COUTmax
calculated in Equation 2 or the switch does not start
properly due to the set current limit:
COUT max ILIM _ MIN 500s / V
PD _ MAX( NormalOper ation)( VIN12V ) (1 )2 0.140 140 mW
If device is in over-current condition and VOUT>2 V,
power dissipation can be calculated as:
22
27< VIN ≤ 32
47
32< VIN ≤ 36
68
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
(6)
PD = (VIN - VOUT) x ILIM (Max)
If device is in short-circuit current limit and VOUT < 2 V,
power dissipation can be calculated as:
(7)
PD = (VIN - VOUT) x (0.75 x ILIM (Max) )
Design Example:
Using FPF2702 in a VIN = 5 V application where ILIM (Max)
= 2 A, assuming VOUT = 2.5 V; power dissipation across
the switch is calculated as:
PD = (5 - 2.5) x 2 = 5W
COUT Selection Guide
24< VIN ≤ 27
(5)
FPF2702 PD(Max) during OC:
During a hard short condition on the output while
operating at greater than 24 V VIN, a large
instantaneous inrush current is delivered to the shorted
output. A capacitor must be placed at the OUTPUT
pin, acting as a current source to support the
instantaneous current draw (Table 2). A low-ESR
capacitor is recommended. Once the value of the
output capacitor is determined from Table 2, Equation
2 must be reevaluated.
Capacitance (μF)
TJ is junction temperature;
PD is power dissipation on the switch;
ΘJA is the thermal resistance, junction-to-ambient of
the package; and
TA is ambient temperature.
For a 12 V application and ILIM (Max) = 1 A, maximum
power dissipation in a normal operation is calculated as:
(2)
VIN (V)
(4)
Design Example
High-Voltage Operation (Output Capacitor)
Table 2.
(3)
(8)
Whereas in a short-circuit current-limit condition (VOUT ≈
0 V), power dissipation is calculated as:
PD = ((VIN - VOUT) x (0.75 x ILIM (Max)) = (5 - 0) x
(0.75 x 2) = 7.5W
(9)
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Input Capacitor
www.fairchildsemi.com
14
For the best performance, all traces should be as short
as possible. To be most effective, the input and output
capacitors should be placed close to the device to
minimize the effects that parasitic trace inductances
may have on normal and short-circuit operation (Figure
42). Using wide traces for IN, OUT, and GND pins helps
minimize parasitic electrical effects as well as the caseto-ambient thermal impedance.
3. The IN, OUT, and GND pins dissipate most of the
heat generated during high-load current condition.
The layout suggested in Figure 42 and Figure 43 is
strongly recommended illustrating a proper layout
for devices in MLP 3x3 packages. IN, OUT, and
GND pins are connected to adequate copper so
that heat may be transferred as efficiently as
possible out of the device. The low-power FLAGB
and ON pins traces may be laid-out diagonally from
the device to maximize the area available to the
ground pad. Place the input and output capacitors
as close as possible to the device.
To minimize the interference between analog ground
(chip ground, pin 5) and power ground during load
current excursion, the ground terminal of the input and
output capacitors and the RSET resistor should be routed
directly to chip ground and away from power ground.
Improving Thermal Performance
Improper layout could result in higher junction
temperature and trigger thermal shutdown protection.
This is particularly significant for the FPF2702, where
the device operates in Constant Current Mode under
overload conditions. During fault conditions, the power
dissipation of the switch could exceed the maximum
absolute power dissipation.
The following techniques improve the thermal
performance of this family of devices. These techniques
are listed in order of the significance of their impact.
1. Thermal performance of the load switch can be
improved by connecting the Die Attach Pad (DAP) of
the MLP 3x3 package to the GND plane of the PCB.
Figure 42. Proper Layout of Output and Ground
Copper Area (Top, SST, and AST Layers)
2. Embedding two exposed through-hole vias into the
DAP provides a path for heat to transfer to the back
GND plane of the PCB. A drill size of round, 15 mils
(0.4 mm) with 1-ounce copper plating is
recommended for appropriate solder reflow. A
smaller-size hole prevents the solder from
penetrating into the via, resulting in device lift-up.
Similarly, a larger hole consumes excessive solder
and may result in voiding the DAP.
15 Mil
Figure 43. Proper Layout (Bottom and ASB Layers)
25 Mil
Figure 41. Two Through-Hole Open Vias
Embedded in the DAP
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
PCB Layout Recommendations
www.fairchildsemi.com
15
The FPF270X demonstration board has components
and circuitry to demonstrate the load switch’s functions
and features. Thermal performance of the board is
improved using the techniques recommended in the
layout recommendations section. Additional information
about demonstration board can be found in the
FPF270X board users guide.
Figure 44. Top, SST, and AST Layers
Figure 45. Bottom and ASB Layers
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
FPF270x Demonstration Board
www.fairchildsemi.com
16
0.65
A
4.90±0.10
(0.635)
8
5
B
1.75
6.00±0.20
1
PIN ONE
INDICATOR
5.60
3.90±0.10
4
1.27
1.27
0.25
C B A
LAND PATTERN RECOMMENDATION
SEE DETAIL A
0.175±0.75
0.22±0.30
C
1.75 MAX
0.10
0.42±0.09
OPTION A - BEVEL EDGE
(0.86) x 45°
R0.10
GAGE PLANE
R0.10
OPTION B - NO BEVEL EDGE
0.36
NOTES: UNLESS OTHERWISE SPECIFIED
8°
0°
A) THIS PACKAGE CONFORMS TO JEDEC
MS-012, VARIATION AA.
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS DO NOT INCLUDE MOLD
FLASH OR BURRS.
D) LANDPATTERN STANDARD: SOIC127P600X175-8M.
E) DRAWING FILENAME: M08Arev15
F) FAIRCHILD SEMICONDUCTOR.
SEATING PLANE
0.65±0.25
(1.04)
DETAIL A
SCALE: 2:1
Figure 46. 8-Lead, Small Outline Package (SOP)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Physical Dimensions
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/dwg/M0/M08A.pdf.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
17
3.00
0.15 C
A
2X
2.52
B
8
3.00
5
1.94
1.70
3.30
PIN1
IDENT
0.56 8X
0.15 C
TOP VIEW
1
2X
0.65
4
0.47 8X
RECOMMENDED LAND PATTERN
0.80 MAX
0.10 C
(0.20)
0.08 C 0.05
0.00
NOTES:
C
SIDE VIEW
A. PACKAGE CONFORMS TO JEDEC MO-229
EXCEPT WHERE NOTED.
SEATING
PLANE
B. DIMENSIONS ARE IN MILLIMETERS.
C. DIMENSIONS AND TOLERANCES PER
ASME Y14.5M, 1994.
2.45
2.35
PIN 1
IDENT
1
(0.35) 4X
D. LAND PATTERN RECOMMENDATION IS
BASED ON FSC DESIGN ONLY.
E. DRAWING FILENAME: MKT-MLP08Vrev1.
4
1.75
1.65
0.40 8X
0.30
8
0.10
0.05
5
0.65
C A B
C
0.40 8X
0.30
BOTTOM VIEW
Figure 47. 8-Lead, 3x3 mm Molded Leadless Package (MLP)
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
Physical Dimensions
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/dwg/ML/MLP08V.pdf.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
18
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2A Adjustable Over-Current Protection Load Switches
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
www.fairchildsemi.com
19
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