LTC4414IMS8#TR [Linear]
LTC4414 - 36V, Low Loss PowerPath Controller for Large PFETs; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LTC4414IMS8#TR |
| 厂家： | 
Linear |
| 描述： | LTC4414 - 36V, Low Loss PowerPath Controller for Large PFETs; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C 电源电路 电源管理电路 光电二极管 控制器 |
| 文件： | 总12页 (文件大小：162K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4414
36V, Low Loss PowerPathTM
Controller for Large PFETs
U
FEATURES
DESCRIPTIO
The LTC®4414 controls an external P-channel MOSFET to
create a near ideal diode function for power switchover.
This permits highly efficient OR’ing of multiple power
sourcesforextendedbatterylifeandlowself-heating.When
conducting, the voltage drop across the MOSFET is typi-
cally20mV.Forapplicationswithawalladapterorotheraux-
iliarypowersource,theloadisautomaticallydisconnected
from the battery when the auxiliary source is connected.
Two or more LTC4414s may be interconnected to allow
switchover between multiple batteries or charging of mul-
tiple batteries from a single charger.
■
Designed Specifically to Drive Large QG PFETs
■
Very Low Loss Replacement for Power Supply
OR’ing Diodes
■
3.5V to 36V AC/DC Adapter Voltage Range
■
Minimal External Components
■
Automatic Switching Between DC Sources
■
Low Quiescent Current: 30µA
■
3V to 36V Battery Voltage Range
■
Limited Reverse Battery Protection
■
MOSFET Gate Protection Clamp
■
Manual Control Input
■
Space Saving 8-Lead MSOP Package
The wide supply operating range supports operation from
one to eight Li-Ion cells in series. The low quiescent
current (30µA typical) is independent of the load current.
The gate driver includes an internal voltage clamp for
MOSFET protection.
U
APPLICATIO S
■
High Current Power Path Switch
■
Industrial and Automotive Applications
The STAT pin can be used to enable an auxiliary P-channel
MOSFET power switch when an auxiliary supply is
detected. This pin may also be used to indicate to a micro-
controller that an auxiliary supply is connected. The con-
trol (CTL) input enables the user to force the primary
MOSFET off and the STAT pin low.
■
Uninterruptable Power Supplies
■
Logic Controlled Power Switch
■
Battery Backup Systems
■
Emergency Systems with Battery Backups
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
The LTC4414 is available in a low profile 8-lead MSOP
package.
U
TYPICAL APPLICATIO
LTC4414 vs Schottky Diode Forward Voltage Drop
8.0
Automatic Switchover of Load Between a Battery and a Power Supply
CONSTANT
UPS840
POWER
R
ON
SUPPLY
INPUT
3.6
SUP75P03_07
TO LOAD
BATTERY
CELL(S)
LTC4414
C
OUT
LTC4414
SENSE
V
CC
V
IN
CONSTANT
VOLTAGE
GND GATE
CTL STAT
470k
SCHOTTKY
DIODE
STATUS OUTPUT
LOW WHEN POWER
SUPPLY PRESENT
4414 TA01
NC
NC
0
0.02
0.5
FORWARD VOLTAGE (V)
4414 TA01b
4414fc
1
LTC4414
W W U W
U
W U
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
Supply Voltage (VIN) .................................. –14V to 40V
Voltage from VIN to SENSE ........................ –40V to 40V
Input Voltage
CTL........................................................–0.3V to 40V
SENSE ....................................................–14V to 40V
Output Voltage
TOP VIEW
STAT
CTL
GND
NC
1
2
3
4
8 GATE
7 V
6 SENSE
5 NC
IN
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 200°C/W
GATE ..................... –0.3V to the Higher of VIN + 0.3V
or SENSE + 0.3V
MS8 PART MARKING
ORDER PART NUMBER
STAT .....................................................–0.3V to 40V
Operating Ambient Temperature Range (Note 2)
I Grade ............................................ –40°C to 125°C
E Grade.............................................. –40°C to 85°C
Operating Junction Temperature ......... –40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LTC4414EMS8
LTC4414IMS8
LTBQF
LTBQG
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating
temperature range, unless otherwise noted specifications are at T = 25°C, V = 12V, CTL and GND = 0V. Current into a pin is positive
A
IN
and current out of a pin is negative. All voltages are referenced to GND, unless otherwise specified.
SYMBOL PARAMETER CONDITIONS
and/or V
MIN
TYP
MAX
UNITS
V ,
IN
Operating Supply Range
V
IN
Must Be in This Range
SENSE
●
●
3
36
V
V
SENSE
for Proper Operation
I
Quiescent Supply Current at Low Supply
While in Forward Regulation
V
= 3.6V. Measure Combined Current
IN
31
36
60
61
µA
µA
QFL
IN
at V and SENSE Pins Averaged with
V
SENSE
= 3.5V and V
= 3.6V (Note 3)
SENSE
I
Quiescent Supply Current at High Supply
While in Forward Regulation
V
= 36V. Measure Combined Current
IN
IN
●
QFH
at V and SENSE Pins Averaged with
V
SENSE
= 35.9V and V
= 36V (Note 3)
SENSE
I
I
I
I
I
Quiescent Supply Current at Low Supply
While in Reverse Turn-Off
V
= 3.6V, V = 3.7V. Measure
SENSE
21
33
14
26
–1
30
45
20
35
µA
µA
µA
µA
QRL
QRH
QCL
QCH
LEAK
IN
Combined Current of V and SENSE Pins
IN
Quiescent Supply Current at High Supply
While in Reverse Turn-Off
V
IN
= 35.9V, V
= 36V. Measure
SENSE
Combined Current of V and SENSE Pins
IN
Quiescent Supply Current at Low Supply
with CTL Active
V
IN
V
IN
= 3.6V, V = 1V,
CTL
– V
= 0.9V
SENSE
Quiescent Supply Current at High Supply
with CTL Active
V
IN
V
IN
= 36V, V = 1V,
CTL
– V
= 0.9V
SENSE
V
and SENSE Pin Leakage Currents
V
IN
V
IN
V
IN
V
IN
V
IN
V
IN
= 28V, SENSE = 0V
= 14V, SENSE = –14V
= 36V, SENSE = 8V
= 0V, SENSE = 28V
= –14V, SENSE = 14V
= 8V, SENSE = 36V
–10
–10
–10
–10
–10
–10
1
1
1
1
1
1
µA
µA
µA
µA
µA
µA
IN
When Other Pin Supplies Power
PowerPath Controller
V
PowerPath Switch Forward Regulation
Voltage
V
V
– V
, 3V ≤ V ≤ 36V, C
= 3nF
= 3nF
●
●
10
10
32
32
mV
FR
IN
SENSE
IN
GATE
GATE
V
RTO
PowerPath Switch Reverse Turn-Off
Threshold Voltage
– V , 3V ≤ V ≤ 36V, C
mV
SENSE
IN
IN
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2
LTC4414
ELECTRICAL CHARACTERISTICS
and current out of a pin is negative. All voltages are referenced to GND, unless otherwise specified.
The
●
denotes specifications which apply over the full operating
temperature range, unless otherwise noted specifications are at T = 25°C, V = 12V, CTL and GND = 0V. Current into a pin is positive
A
IN
SYMBOL PARAMETER
GATE and STAT Outputs
CONDITIONS
MIN
TYP
MAX
UNITS
GATE Active Forward Regulation
Source Current
Sink Current
(Note 4)
I
I
–25
190
–7
500
µA
µA
G(SRC)
G(SNK)
V
G(ON)
GATE Clamp Voltage
Apply I
= 6µA, V = 12V,
8
9
V
GATE
IN
V
SENSE
= 11.9V, Measure V – V
IN GATE
V
GATE Off Voltage
Apply I
= –30µA, V = 12V,
0.35
0
0.92
V
G(OFF)
GATE
IN
V
V
V
= 12.1V, Measure V
– V
SENSE
SENSE GATE
t
t
I
I
t
t
GATE Turn-On Time
GATE Turn-Off Time
STAT Off Current
< –6V, C = 17nF (Note 5)
GATE
600
20
1
µs
µs
µA
µA
µs
µs
G(ON)
G(OFF)
S(OFF)
S(SNK)
S(ON)
S(OFF)
GS
GS
> –1.5V, C
= 17nF (Note 6)
GATE
3V ≤ V ≤ 36V (Note 7)
●
●
–1
50
IN
STAT Sink Current
STAT Turn-On Time
STAT Turn-Off Time
12V ≤ V ≤ 36V (Note 7)
200
8
IN
(Note 8)
(Note 8)
51
CTL Input
V
V
CTL Input Low Voltage
CTL Input High Voltage
CTL Input Pull-Down Current
CTL Hysteresis
3V ≤ V ≤ 36V
●
●
0.35
1
V
V
IL
IH
IN
3V ≤ V ≤ 36V
0.9
5.9
IN
I
0.35V ≤ V ≤ 36V
3.5
µA
mV
CTL
CTL
H
3V ≤ V ≤ 36V
170
CTL
IN
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 5: V is held at 12V and SENSE is stepped from 12.2V to 11.8V to
IN
trigger the event. GATE voltage is initially V
.
G(OFF)
Note 6: V is held at 12V and SENSE is stepped from 11.8V to 12.2V to
IN
trigger the event. GATE voltage is initially internally clamped at V
.
G(ON)
Note 2: The LTC4414E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC4414I is guaranteed and tested
over the –40° to 125° operating temperature range.
Note 3: This results in the same supply current as would be observed with
an external P-channel MOSFET connected to the LTC4414 and operating in
forward regulation.
Note 7: STAT is forced to V – 1.5V. SENSE is set at V – 0.1V to
IN
IN
measure the off current at STAT. SENSE is set V + 0.1V to measure the
IN
sink current at STAT.
Note 8: STAT is forced to 9V and V is held at 12V. SENSE is stepped
IN
from 11.8V to 12.2V to measure the STAT turn-on time defined when I
STAT
reaches one half the measured I
11.8V to measure the STAT turn-off time defined when I
SENSE is stepped from 12.2V to
S(SNK).
reaches one
STAT
half the measured I
S(SNK) .
Note 4: V is held at 12V and GATE is forced to 9V. SENSE is set at 12V
IN
to measure the source current at GATE. SENSE is set at 11.9V to measure
sink current at GATE.
4414fc
3
LTC4414
U W
TYPICAL PERFOR A CE CHARACTERISTICS
V
vs Temperature and
Normalized Quiescent Supply
Current vs Temperature
V
vs Temperature and
FR
RTO
Supply Voltage
Supply Voltage
25
23
21
26
24
22
1.05
1.00
0.95
V
= 3V
IN
V
V
= 28V
= 36V
IN
IN
3V ≤ V ≤ 36V
IN
V
= 36V
= 28V
IN
V
IN
V
= 3V
IN
50
100
150
–50
0
50
100
150
50
100
150
–50
0
–50
0
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4414 G01
4414 G02
4414 G03
V
and SENSE Pin Leakage
IN
V
vs Temperature and I
GATE
vs Temperature
V
vs Temperature
G(OFF)
G(ON)
0
–1
–2
9.0
1.0
0.5
0
I
= 6µA
3V ≤ V ≤ 36V
GATE
IN
I
: V – SENSE = 28V
SENSE IN
V
= 36V
= 10V
IN
I
= –60µA
GATE
8.5
8.0
V
IN
I
= –30µA
GATE
I
: SENSE – V = 28V
VIN IN
I
= 0µA
GATE
50
100
150
–50
50
100
150
–50
0
50
100
150
0
–50
0
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4414 G04
4414 G05
4414 G06
t
vs Temperature
t
vs Temperature
G(ON)
G(OFF)
10
320
300
280
C
= 15nF
C
= 15nF
IN
GATE
LOAD
12V ≤ V ≤ 36V
12V ≤ V ≤ 36V
IN
8
6
50
100
150
–50
0
50
100
150
–50
0
TEMPERATURE (°C)
TEMPERATURE (°C)
4414 G08
4414 G07
4414fc
4
LTC4414
U
U
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PI FU CTIO S
STAT (Pin 1): Open-Drain Output Status Pin. When the
SENSE pin is pulled above the VIN pin with an auxiliary
power source by VRTO or more, the reverse turn-off
threshold (VRTO) is reached. The STAT pin will then go
fromanopenstatetoacurrentsink(IS(SNK)).TheSTATpin
current sink can be used, along with an external resistor,
to turn on an auxiliary P-channel power switch and/or
signal the presence of an auxiliary power source to a
microcontroller.
SENSE (Pin 6): Power Sense Input Pin. Supplies power to
the internal circuitry and is a voltage sense input to the
internalanalogcontroller(Theotherinputtothecontroller
is the VIN pin). This input is usually supplied power from
an auxiliary source such as an AC adapter or back-up
battery which also supplies current to the load.
VIN (Pin7): PrimaryInputSupplyVoltage. Suppliespower
to the internal circuitry and is one of two voltage sense
inputs to the internal analog controller (The other input to
the controller is the SENSE pin). This input is usually
supplied power from a battery or other power source
which supplies current to the load. This pin can be by-
passed to ground with a capacitor in the range of 0.1µF to
10µF if needed to suppress load transients.
CTL(Pin2):DigitalControlInput.Alogicalhighinput(VIH)
on this pin forces the gate to source voltage of the primary
P-channelMOSFETpowerswitchtoasmallvoltage(VGOFF).
This will turn the MOSFET off and no current will flow from
theprimarypowerinputatVIN iftheMOSFETisconfigured
so that the drain to source diode does not forward bias. A
high input also forces the Open-Drain STAT pin ON. If the
STAT pin is used to control an auxiliary P-channel power
switch, then a second active source of power, such as an
AC wall adaptor, will be connected to the load (see Appli-
cations Information). An internal current sink will pull the
CTL pin voltage to ground (logical low) if the pin is open.
GATE (Pin 8): Primary P-Channel MOSFET Power Switch
Gate Drive Pin. This pin is directed by the power controller
to maintain a forward regulation voltage (VFR) of 20mV
between the VIN and SENSE pins when an auxiliary power
source is not present. When an auxiliary power source is
connected, the GATE pin will pull up to the SENSE pin
voltage, turning off the primary P-channel power switch.
GND (Pin 3): Ground. Provides a power return for all the
internal circuits.
W
BLOCK DIAGRA
+
AUXILIARY
–
SUPPLY
*
+
+
OUTPUT
PRIMARY
–
–
TO LOAD
SUPPLY
7
6
V
IN
SENSE
–
+
POWER SOURCE
SELECTOR
A1
POWER
LINEAR GATE
DRIVER AND
VOLTAGE/CURRENT
REFERENCE
0.5V
GATE
STAT
8
1
VOLTAGE CLAMP
V
CC
CTL
ON/OFF
2
+
STATUS
OUTPUT
ON/OFF
C1
ANALOG CONTROLLER
3.5µA
–
GND
3
4414 BD
*DRAIN-SOURCE DIODE OF MOSFET
4414fc
5
LTC4414
U
OPERATIO
OperationcanbestbeunderstoodbyreferringtotheBlock
Diagram, whichillustratestheinternalcircuitblocksalong
with the few external components, and the graph that
accompanies the Typical Application drawing on the front
pageofthedatasheet. Thetermsprimaryandauxiliaryare
arbitrary and may be changed to suit the application.
Operation begins when either or both power sources are
applied and the CTL control pin is below the input low
voltage of 0.35V (VIL). If only the primary supply is
present,thePowerSourceSelectorwillpowertheLTC4414
from the VIN pin. Amplifier A1 will deliver a current to the
Analog Controller block that is proportional to the voltage
difference in the VIN and SENSE pins. While the voltage on
SENSE is lower than VIN – 20mV (VFR), the Analog
Controller will instruct the Linear Gate Driver and Voltage
ClampblocktopulldowntheGATEpinvoltageandturnon
the external P-channel MOSFET. The dynamic pull-down
current of 300µA (IG(SNK)) stops when the GATE voltage
reaches ground or the gate clamp voltage. The gate clamp
The Power Source Selector will power the LTC4414
from the SENSE pin. As the SENSE voltage pulls above
VIN – 20mV, the Analog Controller will instruct the Linear
Gate Driver and Voltage Clamp block to pull the GATE
voltage up to turn off the P-channel MOSFET. When the
voltage on SENSE is higher than VIN + 20mV (VRTO), the
Analog Controller will instruct the Linear Gate Driver and
Voltage Clamp block to rapidly pull the GATE pin voltage
to the SENSE pin voltage. This action will quickly finish
turning off the external P-channel MOSFET if it hasn’t
already turned completely off. For a clean transition, the
reverse turn-off threshold has hysteresis to prevent
uncertainty. The system is now in the reverse turn-off
mode. Power to the load is being delivered through the
external diode and no current is drawn from the primary
supply. The external diode provides protection in case
the auxiliary supply is below the primary supply, sinks
current to ground or is connected reverse polarity.
During the reverse turn-off mode of operation the STAT
pin will sink a current (IS(SNK)) if connected. Note that the
external MOSFET is wired so that the drain to source
diode will momentarily forward bias when power is first
applied to VIN and will become reverse biased when an
auxiliary supply is applied.
voltage is 8.5V (VG(ON)) below the higher of VIN or VSENSE
.
AstheSENSEvoltagepullsuptoVIN –20mV, theLTC4414
will regulate the GATE voltage to maintain a 20mV differ-
ence between VIN and VSENSE which is also the VDS of the
MOSFET. The system is now in the forward regulation
mode and the load will be powered from the primary
supply. Astheloadcurrentvaries, theGATEvoltagewillbe
controlled to maintain the 20mV difference. If the load
current exceeds the P-channel MOSFET’s ability to deliver
the current with a 20mV VDS the GATE voltage will clamp,
theMOSFETwillbehaveasafixedresistorandtheforward
voltage will increase slightly. While the MOSFET is on the
STAT pin is an open circuit.
WhentheCTL(control)inputisassertedhigh, theexternal
MOSFET will have its gate to source voltage forced to a
small voltage VG(OFF) and the STAT pin will sink a mini-
mumof50µAofcurrentifconnected.Thisfeatureisuseful
to allow control input switching of the load between two
power sources as shown in Figure 3 or as a switchable
highsidedriverasshowninFigure7.A3.5µAinternalpull-
down current (ICTL) on the CTL pin will insure a low level
input if the pin should become open.
When an auxiliary supply is applied, the SENSE pin will be
pulled higher than the VIN pin through the external diode.
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LTC4414
W U U
APPLICATIO S I FOR ATIO
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Introduction
Care should be taken to ensure that the power dissipated
is never allowed to rise above the manufacturer’s recom-
mended maximum level. The auxiliary MOSFET power
switch, if used, has similar considerations, but its VGS can
be tailored by resistor selection. When choosing the
resistor value consider the full range of STAT pin current
(IS(SNK)) that may flow through it.
The system designer will find the LTC4414 useful in a
variety of cost and space sensitive power control applica-
tions that include low loss diode OR’ing, fully automatic
switchoverfromaprimarytoanauxiliarysourceofpower,
microcontroller controlled switchover from a primary to
an auxiliary source of power, charging of multiple batter-
ies from a single charger and high side power switching.
VIN and SENSE Pin Bypass Capacitors
External P-Channel MOSFET Transistor Selection
Many types of capacitors, ranging from 0.1µF to 10µF and
located close to the LTC4414, will provide adequate VIN
bypassing if needed. Voltage droop can occur at the load
duringasupplyswitchoverbecausesometimeisrequired
to turn on the MOSFET power switch. Factors that deter-
mine the magnitude of the voltage droop include the
supply rise and fall times, the MOSFET’s characteristics,
the value of COUT and the load current. Droop can be made
insignificant by the proper choice of COUT, since the droop
is inversely proportional to the capacitance. Bypass ca-
pacitance for the load also depends on the application’s
dynamic load requirements and typically ranges from 1µF
to 47µF. In all cases, the maximum droop is limited to the
drain source diode forward drop inside the MOSFET.
Important parameters for the selection of MOSFETs are
the maximum drain-source voltage VDS(MAX), threshold
voltage VGS(VT) and on-resistance RDS(ON)
.
The maximum allowable drain-source voltage, VDS(MAX),
must be high enough to withstand the maximum drain-
source voltage seen in the application.
The maximum gate drive voltage for the primary MOSFET
issetbythesmalleroftheVINsupplyvoltageortheinternal
clamping voltage VG(ON). A logic level MOSFET is com-
monly used, but if a low supply voltage limits the gate
voltage, a sub-logic level threshold MOSFET should be
considered. The maximum gate drive voltage for the
auxiliary MOSFET, if used, is determined by the external
resistor connected to the STAT pin.
Caution must be exercised when using multilayer ceramic
capacitors. Because of the self resonance and high Q
characteristics of some types of ceramic capacitors, high
voltage transients can be generated under some start-up
conditions such as connecting a supply input to a hot
power source. To reduce the Q and prevent these tran-
sients from exceeding the LTC4414’s absolute maximum
voltage rating, the capacitor’s ESR can be increased by
adding up to several ohms of resistance in series with the
ceramic capacitor. Refer to Application Note 88.
As a general rule, select a MOSFET with a low enough
RDS(ON) to obtain the desired VDS while operating at full
loadcurrentandanachievableVGS.TheMOSFETnormally
operates in the linear region and acts like a voltage
controlled resistor. If the MOSFET is grossly undersized,
it can enter the saturation region and a large VDS may
result. However, the drain-source diode of the MOSFET, if
forward biased, will limit VDS. A large VDS, combined with
the load current, will likely result in excessively high
MOSFETpowerdissipation.KeepinmindthattheLTC4414
will regulate the forward voltage drop across the primary
MOSFET at 20mV if RDS(ON) is low enough. The required
RDS(ON) can be calculated by dividing 0.02V by the load
current in amps. Achieving forward regulation will mini-
mize power loss and heat dissipation, but it is not a
necessity. If a forward voltage drop of more than 20mV is
acceptable then a smaller MOSFET can be used, but must
be sized compatible with the higher power dissipation.
Theselectedcapacitancevalueandcapacitor’sESRcanbe
verified by observing VIN and SENSE for acceptable volt-
age transitions during dynamic conditions over the full
load current range. This should be checked with each
power source as well. Ringing may indicate an incorrect
bypass capacitor value and/or too low an ESR.
VIN and SENSE Pin Usage
Sincetheanalogcontroller’sthresholdsaresmall(±20mV),
the VIN and SENSE pin connections should be made in a
4414fc
7
LTC4414
W U U
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APPLICATIO S I FOR ATIO
way to avoid unwanted I • R drops in the power path. Both
pins are protected from negative voltages.
CTL Pin Usage
This is a digital control input pin with low threshold
voltages (VIL,VIH) for use with logic powered from as little
as 1V. During normal operation, the CTL pin can be biased
at any voltage between ground and 36V, regardless of the
supply voltage to the LTC4414. A logical high input on this
pin forces the gate to source voltage of the primary
P-channelMOSFETpowerswitchtoasmallvoltage(VGOFF).
This will turn the MOSFET off and no current will flow from
theprimarypowerinputatVIN iftheMOSFETisconfigured
sothatthedraintosourcediodeisnotforwardbiased. The
high input also forces the STAT pin to sink at least 50µA of
current (IS(SNK)). See the Typical Applications for various
examples on using the STAT pin. A 3.5µA internal pull-
down current (ICTL) on the CTL pin will insure a logical low
level input if the pin should be open.
GATE Pin Usage
The GATE pin controls the external P-channel MOSFET
connected between the VIN and SENSE pins when the load
current is supplied by the power source at VIN. In this
mode of operation, the internal current source, which is
responsible for pulling the GATE pin up, is limited to a few
microamps (IG(SRC)). If external opposing leakage cur-
rents exceed this, the GATE pin voltage will reach the
clamp voltage (VGON) and VDS will be smaller. The internal
current sink, which is responsible for pulling the GATE pin
down, has a higher current capability (IG(SNK)). With an
auxiliary supply input pulling up on the SENSE pin and
exceeding the VIN pin voltage by 20mV (VRTO), the device
enters the reverse turn-off mode and a much stronger
current source is available to oppose external leakage
currents and turn off the MOSFET (VGOFF).
Protection
Most of the application circuits shown provide some
protection against supply faults such as shorted, low or
reversed supply inputs. The fault protection does not
protectshortedsuppliesbutcanisolateothersuppliesand
the load from faults. A necessary condition of this protec-
tion is for all components to have sufficient breakdown
voltages. In some cases, if protection of the auxiliary input
(sometimes referred to as the wall adapter input) is not
required, then the series diode or MOSFET may be
eliminated.
While in forward regulation, if the on resistance of the
MOSFET is too high to maintain forward regulation, the
GATE pin will maximize the MOSFET’s VGS to that of the
clamp voltage (VGON). The clamping action takes place
between VIN and the GATE pin.
STAT Pin Usage
During normal operation, the open-drain STAT pin can be
biased at any voltage between ground and 36V regardless
of the supply voltage to the LTC4414. It is usually con-
nected to a resistor whose other end connects to a voltage
source. In the forward regulation mode, the STAT pin will
be open (IS(OFF)). When a wall adaptor input or other
auxiliary supply is connected to that input, and the voltage
on SENSE is higher than VIN + 20mV (VRTO), the system is
in the reverse turn-off mode. During this mode of opera-
tion the STAT pin will sink at least 50µA of current
(IS(SNK)). This will result in a voltage change across the
resistor, depending on the resistance, which is useful to
turn on an auxiliary P-channel MOSFET or signal to a
microcontroller that an auxiliary power source is con-
nected. External leakage currents, if significant, should be
accounted for when determining the voltage across the
resistor when the STAT pin is either on or off.
Internal protection for the LTC4414 is provided to prevent
damaging pin currents and excessive internal self heating
during a fault condition. These fault conditions can be a
result of VIN, SENSE, GATE or CTL pins shorted to ground
or to a power source that is within the pin’s absolute
maximum voltage limits. Both the VIN and SENSE pins are
capable of being taken significantly below ground without
current drain or damage to the IC (see Absolute Maximum
Voltage Limits). This feature allows for limited reverse-
battery condition without current drain or damage. This
internal protection is not designed to prevent overcurrent
or overheating of external components.
4414fc
8
LTC4414
U
TYPICAL APPLICATIO S
Automatic PowerPath Control
Figure 1 illustrates an application circuit for automatic
switchover of load between a battery and a wall adapter
thatfeatureslowestpowerloss.Operationissimilartothe
Typical Application on the front page except that an
auxiliary P-channel MOSFET replaces the diode. The
STAT pin is used to turn on the MOSFET once the SENSE
pin voltage exceeds the battery voltage by 20mV. When
thewalladapterinputisapplied, thedrain-sourcediodeof
the auxiliary MOSFET will turn on first to pull up the
SENSE pin and turn off the primary MOSFET followed by
turning on of the auxiliary MOSFET. Once the auxiliary
MOSFET has turned on the voltage drop across it can be
very low depending on the MOSFET’s characteristics.
The applications shown in Figures 1 and 2 and the typical
application shown on the first page of this data sheet are
automatic ideal diode controllers that require no assis-
tance from a microcontroller. Each of these will automati-
cally connect the higher supply voltage, after accounting
for certain diode forward voltage drops, to the load with
application of the higher supply voltage. These circuits are
not recommended for load sharing.
Thetypicalapplicationshownonthefirstpageonthisdata
sheet illustrates an application circuit for automatic
switchover of a load between a battery and a wall adapter
or other power input. With application of the battery, the
load will initially be pulled up by the drain-source diode of
the P-channel MOSFET. As the LTC4414 comes into
action, it will control the MOSFET’s gate to turn it on and
reduce the MOSFET’s voltage drop from a diode drop to
20mV. The system is now in the low loss forward regula-
tion mode. Should the wall adapter input be applied, the
SchottkydiodewillpulluptheSENSEpin,connectedtothe
load, above the battery voltage and the LTC4414 will turn
the MOSFET off. The STAT pin will then sink current
indicating an auxiliary input is connected. The battery is
now supplying no load current and all the load current
flows through the Schottky diode. A silicon diode could be
used instead of the Schottky, but will result in higher
power dissipation and heating due to the higher forward
voltage drop.
Figure 2 illustrates an application circuit for the automatic
switchover of a load between a battery and a wall adapter
in the comparator mode. It also shows how a battery
charger can be connected. This circuit differs from Figure
1 in the way the SENSE pin is connected. The SENSE pin
is connected directly to the auxiliary power input and not
the load. This change forces the LTC4414’s control cir-
cuitry to operate in an open-loop comparator mode. While
the battery supplies the system, the GATE pin voltage will
be forced to its lowest clamped potential, instead of being
regulated to maintain a 20mV drop across the MOSFET.
This has the advantages of minimizing power loss in the
MOSFET by minimizing its RON and not having the influ-
ence of a linear control loop’s dynamics. A possible
disadvantage is if the auxiliary input ramps up slow
enough the load voltage will initially droop before rising.
AUXILIARY
P-CHANNEL
MOSFET
*
WALL
ADAPTER
INPUT
WALL
ADAPTER
INPUT
PRIMARY
P-CHANNEL
MOSFET
*
P-CHANNEL
BATTERY
MOSFET
*
CHARGER
TO LOAD
TO LOAD
BATTERY
CELL(S)
BATTERY
CELL(S)
C
OUT
C
OUT
LTC4414
SENSE
LTC4414
7
3
2
6
8
1
V
7
3
2
6
8
1
CC
V
IN
V
SENSE
IN
GND GATE
CTL STAT
47k
STATUS OUTPUT
IS LOW WHEN A
WALL ADAPTER
IS PRESENT
GND GATE
CTL STAT
47k
STATUS OUTPUT
DROPS WHEN A
WALL ADAPTER
IS PRESENT
4414 F02
4414 F01
*DRAIN-SOURCE DIODE OF MOSFET
*DRAIN-SOURCE DIODE OF MOSFET
Figure 1. Automatic Switchover of Load Between a Battery and a
Wall Adapter with Auxiliary P-Channel MOSFET for Lowest Loss
Figure 2. Automatic Switchover of Load Between
a Battery and a Wall Adapter in Comparator Mode
4414fc
9
LTC4414
U
TYPICAL APPLICATIO S
continue to power the load. Only when the primary
voltageishigherthantheauxiliaryvoltagewilltakingCTL
low switch back to the primary power, otherwise the
auxiliary stays connected. When the primary power is
disconnectedandVIN fallsbelowVLOAD, itwillturnonthe
auxiliary MOSFET if CTL is low, but VLOAD must stay up
long enough for the MOSFET to turn on. At a minimum,
This is due to the SENSE pin voltage rising above the
battery voltage and turning off the MOSFET before the
Schottky diode turns on. The factors that determine the
magnitude of the voltage droop are the auxiliary input rise
time, the type of diode used, the value of COUT and the load
current.
Ideal Diode Control with a Microcontroller
C
OUT capacitancemustbesizedtoholdupVLOAD untilthe
transition between the sets of MOSFETs is complete.
Sufficient capacitance on the load and low or no capaci-
tance on VIN will help ensure this. If desired, this can be
avoided by use of a capacitor on VIN to ensure that VIN
falls more slowly than VLOAD
mended for load sharing.
Figure 3 illustrates an application circuit for microcontrol-
ler monitoring and control of two power sources. The
microcontroller’s analog inputs, perhaps with the aid of a
resistor voltage divider, monitors each supply input and
commands the LTC4414 through the CTL input. Back-to-
backMOSFETsareusedsothatthedrain-sourcediodewill
not power the load when the MOSFET is turned off (dual
MOSFETs in one package are commercially available).
. This circuit is not recom-
High Current Power Supply Load Sharing
Figure 4 illustrates an application circuit for dual identical
power supply load sharing. The load will then be shared
between the two power supplies according to their source
impedances. The STAT pins provide information as to
whichinputissupplyingtheloadcurrent.Thisconceptcan
be expanded to more power inputs.
With a logical low input on the CTL pin, the primary input
supplies power to the load regardless of the auxiliary
voltage. When CTL is switched high, the auxiliary input
will power the load whether or not it is higher or lower
than the primary power voltage. Once the auxiliary is on,
the primary power can be removed and the auxiliary will
Q1
*
POWER
TO LOAD
SUPPLY1
AUXILIARY
C
OUT
P-CHANNEL MOSFETS
LTC4414
SENSE
7
3
2
6
8
1
V
CC
*
*
V
IN
AUXILIARY POWER
SOURCE INPUT
OPTIONAL
ZENER
GND GATE
CTL STAT
47k
470k
CLAMP
STATUS
IF V
GS(MAX)
AN ISSUE
MICROCONTROLLER
PRIMARY
P-CHANNEL MOSFETS
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH POWER SUPPLIES
ARE SUPPLYING LOAD CURRENTS.
Q2
*
*
*
TO LOAD
POWER
SUPPLY2
C
0.1µF
OUT
LTC4414
7
3
2
6
8
1
V
CC
LTC4414
V
SENSE
PRIMARY
POWER
SOURCE INPUT
IN
7
3
2
6
8
1
V
SENSE
IN
R
LIMIT
GND GATE
CTL STAT
47k
GND GATE
CTL STAT
STATUS
4414 F04
4414 F03
*DRAIN-SOURCE DIODE OF MOSFET
Q1, Q2: SUB75P03-07
*DRAIN-SOURCE DIODE OF MOSFET
Figure 3. Microcontroller Monitoring and Control
of Two Power Sources
Figure 4. High Current Dual Power Supply Load Sharing
4414fc
10
LTC4414
U
TYPICAL APPLICATIO S
Battery Load Sharing
CTL pin input can be used with a microcontroller and
back-to-back MOSFETs as shown in Figure 4. This allows
complete control for disconnection of the charger from
either battery.
Figure 5 illustrates an application circuit for dual battery
load sharing with automatic switchover of load from
batteriestowalladapter.Whicheverbatterycansupplythe
higher voltage will provide the load current until it is
dischargedtothevoltageoftheotherbattery. Theloadwill
then be shared between the two batteries according to the
capacity of each battery. The higher capacity battery will
provide proportionally higher current to the load. When a
wall adapter input is applied, both MOSFETs will turn off
and no load current will be drawn from the batteries. The
STATpinsprovideinformationastowhichinputissupply-
ing the load current. This concept can be expanded to
more power inputs.
High Side Power Switch
Figure 7 illustrates an application circuit for a logic con-
trolled high side power switch. When the CTL pin is a
logical low, the LTC4414 will turn on the MOSFET. Be-
cause the SENSE pin is grounded, the LTC4414 will apply
maximum clamped gate drive voltage to the MOSFET.
When the CTL pin is a logical high, the LTC4414 will turn
off the MOSFET by pulling its gate voltage up to the supply
input voltage and thus deny power to the load. The
MOSFET is connected with its source connected to the
power source. This disables the drain-source diode from
supplyingvoltagetotheloadwhentheMOSFETisoff.Note
that if the load is powered from another source, then the
drain-source diode can forward bias and deliver current to
the power supply connected to the VIN pin.
WALL
ADAPTER
INPUT
*
TO LOAD
BAT1
C
OUT
LTC4414
SENSE
7
3
2
6
8
1
V
CC
47k
V
IN
GND GATE
CTL STAT
STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
LOAD CURRENT
*
TO LOAD OR
PowerPath
BATTERY
CHARGER
INPUT
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH BATTERIES ARE
SUPPLYING LOAD CURRENTS. WHEN
BOTH STATUS LINES ARE LOW, THEN
WALL ADAPTER IS PRESENT
CONTROLLER
BAT1
*
LTC4414
SENSE
7
3
2
6
8
1
V
CC
470k
V
IN
BAT2
GND GATE
CTL STAT
LTC4414
STATUS IS HIGH
WHEN BAT1 IS
CHARGING
7
3
2
6
8
1
V
CC
47k
V
SENSE
IN
0.1µF
GND GATE
CTL STAT
STATUS IS HIGH
WHEN BAT2 IS
SUPPLYING
*
TO LOAD OR
PowerPath
CONTROLLER
4414 F05
LOAD CURRENT
BAT2
*DRAIN-SOURCE DIODE OF MOSFET
LTC4414
7
3
2
6
8
1
V
CC
470k
V
SENSE
IN
Figure 5. Dual Battery Load Sharing with Automatic
Switchover of Load from Batteries to Wall Adapter
GND GATE
CTL STAT
STATUS IS HIGH
WHEN BAT2 IS
CHARGING
4414 F06
*DRAIN-SOURCE DIODE OF MOSFET
Multiple Battery Charging
Figure 6. Automatic Dual Battery Charging
from Single Charging Source
Figure 6 illustrates an application circuit for automatic
dual battery charging from a single charger. Whichever
battery has the lower voltage will receive the charging
currentuntilbothbatteryvoltagesareequal, thenbothwill
be charged. When both are charged simultaneously, the
higher capacity battery will get proportionally higher cur-
rent from the charger. For Li-Ion batteries, both batteries
will achieve the float voltage minus the forward regulation
voltage of 20mV. This concept can apply to more than two
batteries. The STAT pins provide information as to which
batteries are being charged. For intelligent control, the
P-CHANNEL
MOSFET
*
SUPPLY
INPUT
TO LOAD
C
OUT
LTC4414
SENSE
7
3
2
6
8
0.1µF
V
IN
GND GATE
CTL STAT
1
LOGIC
INPUT
4414 F07
*DRAIN-SOURCE DIODE OF MOSFET
Figure 7. Logic Controlled High Side Power Switch
4414fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC4414
U
PACKAGE DESCRIPTIO
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.52
(.0205)
REF
0.889
(.035
±
±
0.127
.005)
8
7 6
5
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
5.23
(.206)
MIN
4.90 ± 0.152
(.193 ± .006)
3.20 – 3.45
(.126 – .136)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
GAUGE PLANE
0.65
(.0256)
BSC
0.42
±
0.038
1
2
3
4
(.0165
±
.0015)
0.53 ± 0.152
(.021 ± .006)
1.10
(.043)
MAX
0.86
(.034)
REF
TYP
RECOMMENDED SOLDER PAD LAYOUT
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
0.127 ± 0.076
NOTE:
(.009 – .015)
(.005 ± .003)
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
0.65
(.0256)
BSC
TYP
MSOP (MS8) 0204
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
RELATED PARTS
PART NUMBER
LTC1473
DESCRIPTION
COMMENTS
Switches and Isolates Sources Up to 30V
Dual PowerPath Switch Driver
PowerPath Controller for Dual Battery Systems
LTC1479
Complete PowerPath Management for Two Batteries; DC Power Source,
Charger and Backup
LTC1558/LTC1559 Back-Up Battery Controller with Programmable Output
Adjustable Backup Voltage from 1.2V NiCd Button Cell,
Includes Boost Converter
LT®1579
LTC1733/LTC1734 Monolithic Linear Li-Ion Chargers
300mA Dual Input Smart Battery Back-Up Regulator
Maintains Output Regulation with Dual Inputs, 0.4V Dropout at 300mA
Thermal Regulation, No External MOSFET/Sense Resistor
Adjustable Trip Voltage/Hysteresis, ThinSOT
LTC1998
LTC4055
2.5µA, 1% Accurate Programmable Battery Detector
USB Power Controller and Li-Ion Linear Charger
Automatic Battery Switchover, Thermal Regulation, Accepts Wall Adapter
and USB Power, 4mm × 4mm QFN
LTC4354
LTC4410
Negative Voltage Diode-OR Controller and Monitor
USB Power Manager in ThinSOTTM
Replaces Power Schottky Diodes; 80V Operation
Enables Simultaneous Battery Charging and
Operation of USB Component Peripheral Devices
LTC4411
SOT-23 Ideal Diode
2.6A Forward Current, 28mV Regulated Forward Voltage
LTC4412HV
LTC4413
36V, Low Loss PowerPath Controller in MSOP
–40°C to –125°C Operation; Automatic Switch Between DC Sources
Dual 2.6A, 2.5V to 5.5V Ideal Diodes in 3mm × 3mm
DFN
100mΩ ON Resistance, 1µA Reverse Leakage Current, 28mV Regulated
Forward Voltage
4414fc
LT/LWI 0806 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
© LINEAR TECHNOLOGY CORPORATION 2005
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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