Fairchild Semiconductor Electronic Components Datasheet



FPF2701

Adjustable Over-Current Protection Load Switches


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December 2013
FPF2700 / FPF2701 / FPF2702 — AccuPower™ 0.4~2 A
Adjustable Over-Current Protection Load Switches
Features
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
Motor Drives
Digital Cameras
Consumer Electronics
Industrial
Computing
Hard Disk Drives
Telecom Equipment
Description
The AccuPowerFPF270X 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 pluggingloads
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.
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.
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.
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.
Figure 3. SO8 (Top View)
The FPF270X is available in a space-saving, Lead and
Halogen free, 8-lead, MLP 3x3 mm and SO8 packages.
Ordering Information
Part
Number
FPF2700MPX
FPF2701MPX
FPF2702MPX
FPF2700MX
FPF2701MX
FPF2702MX
Current Limit [A]
0.4 2.0
0.4 2.0
0.4 2.0
0.4 2.0
0.4 2.0
0.4 2.0
Current Limit
Blanking Time [ms]
0.5
0.5
NA
0.5
0.5
NA
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 • Rev. 1.0.3
Auto-Restart
Time [ms]
127.5
NA
NA
127.5
NA
NA
ON Pin
Activity
Active LOW
Active LOW
Active LOW
Active LOW
Active LOW
Active LOW
Package
MLP3X3
MLP3X3
MLP3X3
SO8
SO8
SO8
www.fairchildsemi.com


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Application Diagram
VIN
2.8 V 36 V
OFF
ON
CIN
RSET
36 V MAX.
VIN VOUT
TO LOAD
100KΩ
ON FLAGB
100KΩ
COUT
ISET
PGOOD
GND
Block Diagram
Figure 4. Typical Application
IN
VDD
Reg
BGAP/BIAS
VREF
Current Limit
UVLO
ON
CONTROL
LOGIC
SOA Protection
Current Limit
ISET
FLAGB
THERMAL
PROTECTION
CHARGE
PUMP
VIN VOUT
+
-
OUT
PGOOD
GND
Figure 5. Block Diagram
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
2
www.fairchildsemi.com


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Pin Configurations
VOUT 8
FLAGB 7
NC 6
GND
1 VIN
2 PGOOD
3 ISET
GND 5
4 ON
Figure 6. MLP (Bottom View)
VIN 1
PGOOD 2
ISET 3
ON 4
8 VOUT
7 FLAGB
6 NC
5 GND
Figure 7. SO8 (Top View)
Pin Definitions
Pin #
1
2
3
4
5
6
7
8
Name
VIN
PGOOD
ISET
ON
GND
NC
FLAGB
VOUT
Description
Supply Input. Input to the power switch and the supply voltage for the IC.
Power-Good Output. Open-drain output to indicate that output voltage has reached 90% of
input voltage.
Current Limit Set Input. A resistor from ISET to ground sets the current limit for the switch.
ON Control Input. Active LOW.
Ground
No connection. Leave open or connect to ground.
Fault Output. Active LOW, open-drain output that indicates current limit, under-voltage, or
over-temperature state.
Switch Output. Output of the power switch.
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
3
www.fairchildsemi.com


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Absolute Maximum Ratings
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
ON to GND
MLP 3x3(1), See Figure 8
PD Power Dissipation (TA=25°C) SO8(1), See Figure 10
-0.3 VIN + 0.3
-0.3 6
1.25
1.00
V
V
W
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
Charged Device Model, JESD22-C101
2000
2000
V
JA
Thermal Resistance,
Junction to Ambient
MLP 3x3(1), See Figure 8
SO8(1), See Figure 10
80
°C/W
102
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.
Figure 8. 80°C/W Mounted on a 1in2 Pad
of 2-oz. Copper
Figure 9. 226°C/W Mounted on a Minimum Pad
of 2-oz. Copper
Figure 10. 102°C/W mounted on a 1in2 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
VIN Input Supply Voltage
TA Ambient Operating Temperature
Min.
2.8
-40
Max.
36.0
85
Unit
V
°C
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
4
www.fairchildsemi.com


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Electrical Characteristics
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
Basic Operation
VIN
IQ
ISHDN
Operating Voltage
Quiescent Current
Shutdown Current
RON On Resistance
VIH
VIL
ILK
ISWOFF
VFLAGB(LO)
IFLAGB(HI)
ON Input Logic HIGH Voltage
ON Input Logic LOW Voltage
ON Input Leakage
Off Switch Leakage
FLAGB Output Logic LOW Voltage
FLAGB Output Logic HIGH Leakage
Current
VPGOOD PGOOD Trip Voltage
VPGOOD(HYS) PGOOD Hysteresis
VPGOOD(LO)
IPGOOD(HI)
PGOOD Output Logic LOW Voltage
PGOOD Output High Leakage
Current
Protections
ILIM Current Limit
ISC Short Circuit Current Limit
TSD Thermal Shutdown
UVLO Under-Voltage Shutdown
UVLO_HYST Under-Voltage Shutdown Hysteresis
Dynamic
tdon
tdoff
tR
tF
tBLANK
tRESTART
tCLR
Turn On Delay
Turn Off Delay
VOUT Rise Time
VOUT Fall Time
Over-Current Blanking Time
Auto-Restart Time
Current-Limit Response Time
Conditions
VIN=12 V, VON=0 V, IOUT=0 A
VIN=36 V, VON=3.3 V, IOUT=0 A
TA=25°C, VIN=12 V
TA=-40 to +85°C, VIN=12 V
TA=25°C, VIN=5 V
TA=-40 to +85°C, VIN=5 V
VIN=2.8 to 36 V
VIN=2.8 to 36 V
VON=5.5 V or GND
VIN=36 V, VON=3.3 V, VOUT=0 V
VIN=5 V, ISINK=1 mA
VIN=36 V, Switch On,
VFLAGB=36 V
VIN=5 V, VOUT as Percent of VIN,
VOUT Rising
VIN=5 V, VOUT as Percent of VIN,
VOUT Falling
VIN=5 V, ISINK=1 mA
VIN=36 V, Switch ON,
VPGOOD=36 V
TA=25°C
VOUT < 2 V, Switch in Over-
Current Condition
Shutdown Threshold
Return from Shutdown
Hysteresis
VIN Increasing
RL=500 Ω, CL=2 µF
FPF2700/1, TA=25°C
FPF2700, TA=25°C
VIN=12 V, VON=0 V
Min. Typ. Max. Unit
2.8 36.0 V
92 140 μA
5 14 μA
88 114
140
88 114
140
2.0 V
0.8 V
-1 1 μA
0.01 μA
0.1 0.2 V
1 μA
90 %
3%
0.1 0.2 V
1 μA
-20 +20
0.75 x
INOM
140
110
30
2.3 2.5 2.7
100
%
A
°C
V
mV
2.7
0.1
7.5
1.5
0.25 0.50 0.75
63.8 127.5 191.2
50
ms
ms
ms
μs
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
5
www.fairchildsemi.com


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Timing Diagram
VOUT
VON
90
10 %
%
tR
3.3
V
50
%
90
% 10
%
tF
50
%
VOUT
10
%
90
%
tdon tdoff
tON = tR + tdon tOFF = tF + tdoff
Figure 12. Timing Diagram
Typical Performance Characteristics
VIN = 12 V and TA = 25°C.
1.40
TA = 25°C
1.38
1.35
1.33
VIH
1.30
1.28
1.25
1.23
1.20
0
VIL
5 10 15 20 25 30 35 40
Supply Voltage (V)
Figure 13. ON Threshold vs. Supply
1.80
1.70 VIN = 12V
1.60
1.50
1.40
1.30
VIL
1.20
1.10
1.00
0.90
0.80
-50
-25
0
VIH
25 50 75
TJ, Junction Temperature (oC)
100
125
Figure 14. ON Threshold vs. Temperature
150
130
VON = 0V
120
110
100
90
80
70
TA = 125°C
TA = 85°C
TA = 25°C
TA = -40°C
12
VON = 5V
10
8
6
4
2
TA = 85°C
TA = 125°C
TA = -40°C
TA = 25°C
60
0
5 10 15 20 25 30 35 40
Supply Voltage (V)
0
0 5 10 15 20 25 30 35 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
6
www.fairchildsemi.com


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Typical Performance Characteristics
VIN = 12 V and TA = 25°C.
100
95
90
85
80
75
70
65
60
0
10Supply 2V0oltage (V3)0
40
Figure 17. On Resistance vs. Supply Voltage
160
140
120
100
80
60
40
-50 -25 0 25 50 75 100 125 150
TJ, Junction Temperature (oC)
Figure 18. On Resistance vs. Junction Temperature
4.0
VIN = 12V
3.5 RL = 500
CL = 2µF
3.0
2.5
2.0
1.5
1.0
-50
-25 0 25 50 75 100 125
TJ, Junction Temperature (oC)
150
12
11
10
9
8
7
6
5
4
-50 -25 TJ,0Junc2t5ion5T0em7p5era1t0u0re1(o2C5) 150
Figure 19. Turn-On Delay vs. Junction Temperature Figure 20. Output Rise Time vs. Junction Temperature
0.15 2.00
0.13 1.90
0.11 1.80
0.09 1.70
0.07 1.60
0.05
-50 -25 0 25 50 75 100 125 150
TJ, Junction Temperature (oC)
1.50
-50 -25 0 25 50 75 100 125 150
TJ, Junction Temperature (oC)
Figure 21. Turn-Off Delay vs. Junction Temperature Figure 22. Output Fall Time vs. Junction Temperature
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
7
www.fairchildsemi.com


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Typical Operation Characteristics of FPF2700 and FPF2701
When VOUT<2 V, the current limit is set to 75% of ILIM.
VON
VOUT
IOUT
5V
0V
VIN
2V
0V
ILIM
Slew rate limited turn-on
tRISE = 7.5ms
Turn-on delay
tDON = 2.7ms
Figure 23. Normal Startup to 0.5X ILIM
VOUT
VIN
2V
0V
12A
IOUT
0.75x
IILLIIMM
OUT shorted to GND
and switch immediately
turned OFF
FLAGB
Switch turned off due to the
Current limited expiration of tBLANK (FPF2700,
operation at FPF2701) or due to over-heating
0.75xILIM
NOTE: Auto-restart after
tRESTART (FPF2700) or
tBLANK or
Thermal Shutdown
restart after cooling
down is not shown
Switch turns back ON and enters current
limited operation at short circuit current limit
Turn-on delay is similar
to normal tDON ~ 2.7ms
(75% of ISET)
VIN
2V
0V
12A
IOUT
ILIM
Load
demanding
1.5X ISET
FLAGB
Current limited
operation at ISET
tBLANK or
Thermal
Shutdown
NOTE: Auto-restart after
tRESTART (FPF2700) or
restart after cooling down
is not shown
Switch turned off due to the
expiration of tBLANK (FPF2700,
FPF2701) or due to over-heating
Figure 24. OUT Shorted to GND, Short Condition
Persists (SOA Protection Followed by Current-Limited
Operation)
Figure 25. OUT Overloaded with 1.5X ILIM
(Long-Duration Overload)
VOUT
VIN
2V
0V
12A
IOUT
ISET
OUT shorted to GND
and switch immediately
turned OFF
FLAGB
Rise time tR ~
7.5ms
Turn-on delay is
similar to normal
tDON ~ 2.7ms
Normal operation
Switch turns back ON
and enters normal
operation
VOUT
VIN
2V
0V
12A
IOUT
ISET
Output Load current
demanding 1.5X ISET
FLAGB
Normal operation
Load demanding I=1.5X ISET
removed from OUT before the
expiration of tBLANK (FPF2700,
FPF2701) or before over-heating
Figure 26. OUT Shorted to GND, Short Condition
Removed (SOA Protection Followed by
Normal Operation)
Figure 27. OUT Overloaded with 1.5X ILIM
(Transient Overload)
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
8
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Typical Operation Characteristics of FPF2702
VOUT
VIN
2V
0V
12A
IOUT
0.
75x
IILLIIMM
Current limited
operation at
0. 75xILIM
Switch turned off
due to over-heating
OUT shorted to GND
and switch immediately
turned OFF
FLAGB
Switch turns back ON and enters
current limited operation at short
circuit current limit (75 % of ISET )
Turn - on delay is similar
to normal tDON ~ 2.7ms
FLAGB
asserts due to
current limit
FLAGB asserts due to
Thermal Shutdown
Figure 28. OUT Shorted to GND, Short Condition Persists
(SOA Protection Current Limit Followed by Current Limit)
VOUT
VIN
2V
0V
12A
IOUT
ILIM
Load demanding
1.5X ISET
Current limited
operation at ISET
Switch turned off due
to over-heating
FLAGB
FLAGB
asserts due to
current limit
FLAGB asserts due
to Thermal Shutdown
Figure 29. OUT Overloaded with 1.5X ILIM (Long-Duration Overload)
© 2010 Fairchild Semiconductor Corporation
FPF2700 / FPF2701 / FPF2702 Rev. 1.0.3
9
www.fairchildsemi.com


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Typical Performance Characteristics FPF270X
VIN = 12 V and TA = 25°C.
Figure 30. 12V Turn-On Delay (RL=500 , COUT=2 µF) Figure 31. 12 V Turn-Off Delay (RL=500 , COUT=2 µF)
Figure 32. 12 V Blanking Time
(Output Overloaded and tblank Expired, FPF2700/01,
ILIM=1 A, ILOAD=3.3 A, COUT= µF, RLOAD=500 ) VOC(2)
Figure 33. 12 V Restart Time
(Switch Turned ON into Persistent Over-Current
Condition,tRESTART~127.5 ms)
Figure 34. Soft Overload and Constant Current
Figure 35. OUT Shorted to GND, Short Condition
(ILOAD > ILIM, FPF2702 Enters Constant Current Mode,
Running at ILIM)
Note:
Removed (SOA Protection Followed by a Normal
Operation, FPF2700 / FPF2701)
2. VOC signal forces the device into an over-current condition by loading a 500 mresistor 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
10
www.fairchildsemi.com


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Application Information
Description of Operation
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.
FPF270X offers adjustable current limiting, under-
voltage 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.
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 over-
current 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 pull-
down or pull-up resistors and should not be left floating.
Fault Reporting
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.
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).
During shutdown, the pull-down on FLAGB is disabled
to reduce current draw from the supply. A 100 kΩ pull-
up resistor is recommended in the application.
Current Limiting
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 constant-
current state until the ON pin is deactivated or the
thermal shutdown turns off the switch.
Besides the current-limiting functionality, the switch is
protected by the thermal shutdown protection and an
independent SOA protection circuit is available.
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)
When the output voltage drops below the short-circuit
threshold voltage, VSCTH, the current-limit value re-
conditions 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 VSCTH
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.
Setting the Current Limit Value
FPF270X has an adjustable 0.4 A to 2.0 A minimum
current limit set through an external resistor, RSET,
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.
Use the following equation to calculate the value of the
resistor for intended typical current limit value:
RSET
(k)
277.5
ILIM (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
11
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Table 1.
RSET
(k)
111
124
147
182
220
274
374
549
RSET Selection Guide
Current Limit [A]
Min.
Typ.
Max.
2.00 2.50 3.00
1.79 2.24 2.69
1.51 1.89 2.27
1.22 1.52 1.83
1.01 1.26 1.51
0.81 1.01 1.22
0.59 0.74 0.89
0.40 0.51 0.61
Tol. (%)
20
20
20
20
20
20
20
20
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
100
200 300 400
RSET (k)
Figure 36. ILIM vs. RSET
500
600
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
UVLO Threshold
Device Wake up
VIN
FLAGB
Rise time
10%VOUT
90%VOUT
VOUT
Figure 37. Under-Voltage Lockout Performance
Power Good
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.
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.
Thermal Shutdown
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.
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).
ON
VIN
VOUT
2V
IOUT
ILIM
Thermal Cycling
Device cools off
Over
current
condition
FLAGB
Figure 38. FPF2702 Thermal Shutdown Behavior
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SOA (FPF2702)
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
pad size of one square inch.(1)
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.
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Input Capacitor
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 high-
voltage or high-current applications. An electrolytic
capacitor can be used in parallel to further reduce the
voltage drop.
Output Capacitor
A 0.1 μF to 1 μF capacitor, COUT, 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.
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
(2)
Power Dissipation
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( NormalOperation) (ILIM( Max ) )2 RON( MAX )
(3)
The maximum junction temperature should be limited to
125°C under normal operation. Junction temperature
can be calculated using the equation:
TJ PD  JA TA
(4)
where:
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.
Design Example
For a 12 V application and ILIM (Max) = 1 A, maximum
power dissipation in a normal operation is calculated as:
PD _MAX( NormalOperation)(VIN12V ) (1)2 0.140 140mW
(5)
FPF2702 PD(Max) during OC:
If device is in over-current condition and VOUT>2 V,
power dissipation can be calculated as:
PD = (VIN - VOUT) x ILIM (Max)
(6)
High-Voltage Operation (Output Capacitor)
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.
Table 2. COUT Selection Guide
VIN (V)
Capacitance (μF)
24< VIN ≤ 27
22
27< VIN ≤ 32
47
32< VIN ≤ 36
68
If device is in short-circuit current limit and VOUT < 2 V,
power dissipation can be calculated as:
PD = (VIN - VOUT) x (0.75 x ILIM (Max) )
(7)
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
(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)
© 2010 Fairchild Semiconductor Corporation
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PCB Layout Recommendations
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 case-
to-ambient thermal impedance.
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.
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.
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.
Figure 42. Proper Layout of Output and Ground
Copper Area (Top, SST, and AST Layers)
15 Mil
25 Mil
Figure 43. Proper Layout (Bottom and ASB Layers)
Figure 41. Two Through-Hole Open Vias
Embedded in the DAP
© 2010 Fairchild Semiconductor Corporation
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FPF270x Demonstration Board
The FPF270X demonstration board has components
and circuitry to demonstrate the load switchs 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
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Physical Dimensions
4.90±0.10 A
(0.635)
85
B
6.00±0.20
3.90±0.10
1.75
0.65
5.60
PIN ONE
INDICATOR
1
0.175±0.75
4
1.27
0.25
1.27
C B A LAND PATTERN RECOMMENDATION
SEE DETAIL A
1.75 MAX
C
0.42±0.09
0.22±0.30
0.10
OPTION A - BEVEL EDGE
R0.10
R0.10
0.65±0.25
(0.86) x 45°
GAGE PLANE
0.36
SEATING PLANE
(1.04)
DETAIL A
SCALE: 2:1
OPTION B - NO BEVEL EDGE
NOTES: UNLESS OTHERWISE SPECIFIED
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.
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.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/dwg/M0/M08A.pdf.
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Physical Dimensions
0.15 C
2X
3.00
A
B
2.52
85
PIN1
IDENT
3.00
TOP VIEW
0.15 C
2X
0.10 C
0.80 MAX
0.08 C 0.05
0.00
SEATING
PLANE
SIDE VIEW
(0.20)
C
PIN 1
IDENT
2.45
2.35
14
(0.35) 4X
1.70 1.94
3.30
0.56 8X
1
0.65
4
0.47 8X
RECOMMENDED LAND PATTERN
NOTES:
A. PACKAGE CONFORMS TO JEDEC MO-229
EXCEPT WHERE NOTED.
B. DIMENSIONS ARE IN MILLIMETERS.
C. DIMENSIONS AND TOLERANCES PER
ASME Y14.5M, 1994.
D. LAND PATTERN RECOMMENDATION IS
BASED ON FSC DESIGN ONLY.
E. DRAWING FILENAME: MKT-MLP08Vrev1.
1.75
1.65
0.40
0.30
8X
8
0.65
0.10 C A B
5 0.05 C
0.40
0.30
8X
BOTTOM VIEW
Figure 47. 8-Lead, 3x3 mm Molded Leadless Package (MLP)
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.
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