LTC4412HVIS6#TR [Linear]
LTC4412HV - 36V, Low Loss PowerPath Controller in ThinSOT; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C;
| 型号： | LTC4412HVIS6#TR |
| 厂家： | 
Linear |
| 描述： | LTC4412HV - 36V, Low Loss PowerPath Controller in ThinSOT; Package: SOT; Pins: 6; 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：173K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4412HV
36V, Low Loss PowerPathTM
Controller in ThinSOT
U
FEATURES
DESCRIPTIO
TheLTC®4412HVcontrolsanexternalP-channelMOSFET
to create a near ideal diode function for power switchover
orloadsharing.ThispermitshighlyefficientOR’ingofmul-
tiple power sources for extended battery life and low self-
heating. When conducting, the voltage drop across the
MOSFET is typically 20mV. For applications with a wall
adapter or other auxiliary power source, the load is auto-
maticallydisconnectedfromthebatterywhentheauxiliary
sourceisconnected.TwoormoreLTC4412HVsmaybein-
terconnected to allow load sharing between multiple bat-
teriesorchargingofmultiplebatteriesfromasinglecharger.
The LTC4412HV is an extended supply and temperature
range version of the LTC4412.
■
Very Low Loss Replacement for Power Supply
OR’ing Diodes
■
3V to 36V AC/DC Adapter Voltage Range
■
–40°C to 125°C Operating Temperature Range
■
Minimal External Components
■
Automatic Switching Between DC Sources
■
Simplifies Load Sharing with Multiple Batteries
■
Low Quiescent Current: 11µA
■
2.5V to 36V Battery Voltage Range
■
Reverse Battery Protection
■
Drives Almost Any Size MOSFET for Wide Range of
Current Requirements
■
MOSFET Gate Protection Clamp
■
Manual Control Input
The wide supply operating range supports operation from
one to eight Li-Ion cells in series. The low quiescent
current (11µA typical) is independent of the load current.
The gate driver includes an internal voltage clamp for
MOSFET protection.
Low Profile (1mm) SOT-23 (ThinSOTTM) Package
■
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APPLICATIO S
■
Industrial and Automotive Applications
■
Notebook and Handheld Computers
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.
■
USB-Powered Peripherals
■
Uninterruptable Power Supplies
■
Logic Controlled Power Switch
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath and ThinSOT are trademarks of Linear Technology Corporation.
TheLTC4412HVisavailableinalowprofile(1mm)SOT-23
package.
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LTC4412HV vs Schottky Diode Forward Voltage Drop
TYPICAL APPLICATIO
1
CONSTANT
1N5819
WALL
R
ON
ADAPTER
INPUT
FDN306P
TO LOAD
BATTERY
CELL(S)
LTC4412HV
C
OUT
LTC4412HV
1
2
3
6
5
4
V
CC
V
IN
SENSE
CONSTANT
VOLTAGE
GND GATE
CTL STAT
470k
SCHOTTKY
DIODE
STATUS OUTPUT
LOW WHEN WALL
ADAPTER PRESENT
4412HV F01
0
0.02
Figure 1. Automatic Switchover of Load Between a Battery and a Wall Adapter
0.5
4412HV F01b
FORWARD VOLTAGE (V)
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LTC4412HV
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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
GATE ..................... –0.3V to the Higher of VIN + 0.3V
or SENSE + 0.3V
STAT .....................................................–0.3V to 40V
Operating Ambient Temperature Range
ORDER PART
NUMBER
TOP VIEW
LTC4412HVIS6
V
1
6 SENSE
5 GATE
4 STAT
IN
GND 2
CTL 3
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
S6 PART MARKING
LTBHR
TJMAX = 125°C, θJA = 230°C/W
(Note 2) ........................................... –40°C to 125°C
Operating Junction Temperature ......... –40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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 TA = 25°C, VIN = 12V, CTL and GND = 0V. Current into a pin is positive
and current out of a pin is negative. All voltages are referenced to GND, unless otherwise specified.
SYMBOL PARAMETER
CONDITIONS
and/or V Must Be in This Range
SENSE
for Proper Operation
MIN
TYP
MAX
UNITS
V ,
IN
Operating Supply Range
V
●
●
2.5
36
V
IN
V
SENSE
I
Quiescent Supply Current at Low Supply
While in Forward Regulation
V
= 3.6V. Measure Combined Current
11
18
19
32
µA
µA
QFL
IN
at V and SENSE Pins Averaged with
IN
V
= 3.5V and V
= 3.6V (Note 3)
SENSE
SENSE
I
Quiescent Supply Current at High Supply
While in Forward Regulation
V
= 36V. Measure Combined Current
IN
●
QFH
at V and SENSE Pins Averaged with
IN
V
= 35.9V and V
= 36V (Note 3)
SENSE
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
10
19
7
19
33
13
25
1
µA
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
= 35.9V, V
= 36V. Measure
SENSE
IN
Combined Current of V and SENSE Pins
IN
Quiescent Supply Current at Low Supply
with CTL Active
V
V
= 3.6V, V
= 0V, V
= 1V
CTL
IN
IN
SENSE
SENSE
Quiescent Supply Current at High Supply
with CTL Active
= 36V, V
= 8V, V = 1V
15
0
CTL
V
and SENSE Pin Leakage Currents
V
V
= 28V, V
= 14V, V
= 0V; V
= –14V; V
= 28V, V = 0V
= 14V, V = –14V
SENSE IN
–3
IN
IN
IN
SENSE
SENSE
SENSE
IN
When Other Pin Supplies Power
PowerPath Controller
V
V
PowerPath Switch Forward Regulation
Voltage
V
V
– V
, 2.5V ≤ V ≤ 36V
●
●
10
10
20
20
32
32
mV
mV
FR
IN
SENSE
IN
PowerPath Switch Reverse Turn-Off
Threshold Voltage
– V , 2.5V ≤ V ≤ 36V
IN IN
RTO
SENSE
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LTC4412HV
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 TA = 25°C, VIN = 12V, CTL and GND = 0V. Current into a pin is positive
SYMBOL PARAMETER
GATE and STAT Outputs
CONDITIONS
MIN
TYP
MAX
UNITS
GATE Active Forward Regulation
Source Current
Sink Current
(Note 4)
I
I
–1
25
–2.5
50
–5
85
µA
µA
G(SRC)
G(SNK)
V
G(ON)
GATE Clamp Voltage
Apply I
= 1µA, V = 12V,
6.3
7
7.7
V
GATE
IN
V
SENSE
= 11.9V, Measure V – V
IN GATE
V
GATE Off Voltage
Apply I
= –5µA, V = 12V,
0.13
0.25
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
< –3V, C = 1nF (Note 5)
GATE
110
13
0
175
22
1
µs
µs
µA
µA
µs
µs
G(ON)
G(OFF)
S(OFF)
S(SNK)
S(ON)
S(OFF)
GS
GS
> –1.5V, C
= 1nF (Note 6)
GATE
2.5V ≤ V ≤ 36V (Note 7)
●
●
–1
6
IN
STAT Sink Current
STAT Turn-On Time
STAT Turn-Off Time
2.5V ≤ V ≤ 36V (Note 7)
10
4.5
40
17
25
75
IN
(Note 8)
(Note 8)
CTL Input
V
V
CTL Input Low Voltage
CTL Input High Voltage
CTL Input Pull-Down Current
CTL Hysteresis
2.5V ≤ V ≤ 36V
●
●
0.35
5.9
V
V
IL
IH
IN
2.5V ≤ V ≤ 36V
0.9
1
IN
I
0.35V ≤ V ≤ 36V
3.5
µA
mV
CTL
CTL
H
2.5V ≤ V ≤ 36V
135
CTL
IN
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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 LTC4412HV is guaranteed to meet performance specifications
over the –40°C to 125°C operating ambient temperature range.
Note 3: This results in the same supply current as would be observed with
an external P-channel MOSFET connected to the LTC4412HV 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
Note 4: V is held at 12V and GATE is forced to 10.5V. SENSE is set at
12V to measure the source current at GATE. SENSE is set at 11.9V to
measure sink current at GATE.
S(SNK).
IN
reaches one
STAT
half the measured I
S(SNK) .
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)
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LTC4412HV
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TYPICAL PERFOR A CE CHARACTERISTICS
VFR vs Temperature and
Supply Voltage
Normalized Quiescent Supply
Current vs Temperature
VRTO vs Temperature and
Supply Voltage
22
20
18
22
20
18
1.05
V
IN
= 2.5V
V
V
= 36V
= 28V
IN
3.6V ≤ V ≤ 36V
IN
IN
V
= 28V
= 36V
IN
1.0
V
IN
= 2.5V
V
IN
0.95
50
100 125
–50 –25
0
25
75
50
TEMPERATURE (°C)
100 125
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
–50 –25
0
25
75
TEMPERATURE (°C)
4412HV G01
4412HV G02
4412HV G03
V
IN and SENSE Pin Leakages vs
VG(OFF) vs Temperature and IGATE
Temperature and Supply Voltage
VG(ON) vs Temperature
7.1
0
–1
–2
–3
–4
–5
0.25
0.20
0.15
0.10
0.05
0
I
8V ≤ V ≤ 36V
2.5V ≤ V ≤ 36V
LEAK
IN
= 1µA
IN
I
GATE
I
= –10µA
GATE
I
: V
= 36V, V = 0V
VIN SENSE IN
I
= –5µA
GATE
I
: V
= 24V, V = –14V
VIN SENSE IN
7.0
6.9
I
= 0µA
GATE
I
: V = 36V, V
SENSE IN
= 0V
SENSE
I
: V = 24V, V
SENSE IN
= –14V
SENSE
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
50
100 125
–50 –25
0
25
50
75
100 125
–50 –25
0
25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
4412HV G05
4412HV G04
4412HV G06
tG(ON) vs Temperature and
Supply Voltage
tG(OFF) vs Temperature and
Supply Voltage
IS(SNK) vs Temperature and VIN
15
14
13
12
11
10
10.5
10.0
9.5
120
110
100
90
V
= V – 1.5V
IN
STAT
V
= 12V
= 24V
IN
V
V
IN
V
= 12V
= 36V
IN
V
= 36V
IN
= 30V
= 36V
IN
IN
V
= 2.5V
V
IN
IN
V
50
100 125
50
100 125
–50 –25
0
25
75
–50 –25
25
75
0
50
100 125
–50 –25
0
25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4412HV G08
4412HV G09
4412HV G07
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LTC4412HV
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PI FU CTIO S
VIN (Pin1): 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.
STAT (Pin 4): Open-Drain Output Status Pin. When the
SENSE pin is pulled above the VIN pin with an auxiliary
powersourcebyabout20mVormore, thereverseturn-off
threshold (VRTO) is reached. The STAT pin will then go
from an open state to a 10µA current sink (IS(SNK)). The
STAT pin 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.
GND (Pin 2): Ground. Provides a power return for all the
internal circuits.
GATE (Pin 5): 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.
CTL(Pin3):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 STAT pin to sink 10µA of current
(IS(SNK)). If the STAT pin is used to control an auxiliary P-
channel power switch, then a second active source of
power,suchasanACwalladaptor,willbeconnectedtothe
load (see Applications Information). An internal current
sink will pull the CTL pin voltage to ground (logical low) if
the pin is open.
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.
W
BLOCK DIAGRA
+
AUXILIARY
–
SUPPLY
+
+
OUTPUT
PRIMARY
–
–
TO LOAD
SUPPLY
1
6
V
SENSE
IN
–
+
POWER SOURCE
SELECTOR
A1
POWER
LINEAR GATE
DRIVER AND
VOLTAGE/CURRENT
REFERENCE
0.5V
GATE
STAT
5
4
VOLTAGE CLAMP
V
CC
CTL
ON/OFF
3
+
STATUS
OUTPUT
ON/OFF
C1
ANALOG CONTROLLER
3.5µA
10µA
–
GND
2
4412HV BD
*DRAIN-SOURCE DIODE OF MOSFET
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LTC4412HV
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OPERATIO
OperationcanbestbeunderstoodbyreferringtotheBlock
Diagram, whichillustratestheinternalcircuitblocksalong
with the few external components, and the graph that
accompaniesFigure1.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, the Power Source Selector will power the
LTC4412HV 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
VoltageClampblocktopulldowntheGATEpinvoltageand
turnontheexternalP-channelMOSFET.Thedynamicpull-
down current of 50µA (IG(SNK)) stops when the GATE
voltage reaches ground or the gate clamp voltage. The
gate clamp voltage is 7V (VG(ON)) below the higher of VIN
or VSENSE. As the SENSE voltage pulls up to VIN – 20mV,
the LTC4412HV will regulate the GATE voltage to maintain
a 20mV difference 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. As the load current varies, the GATE
voltagewillbecontrolledtomaintainthe20mVdifference.
IftheloadcurrentexceedstheP-channelMOSFET’sability
to deliver the current with a 20mV VDS the GATE voltage
will clamp, the MOSFET will behave as a fixed resistor and
theforwardvoltagewillincreaseslightly.WhiletheMOSFET
is on the STAT pin is an open circuit.
The Power Source Selector will power the LTC4412HV
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 transistion, 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. Dur-
ing the reverse turn-off mode of operation the STAT pin
will sink 10µA of 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.
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 10µA of
current if connected. This feature is useful to allow control
input switching of the load between two power sources as
shown in Figure 4 or as a switchable high side driver as
shown in Figure 7. A 3.5µA internal pull- 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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LTC4412HV
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APPLICATIO S I FOR ATIO
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Introduction
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 dissipa-
tion. Care should be taken to ensure that the power
dissipatedisneverallowedtoriseabovethemanufacturer’s
recommended maximum level. The auxiliary MOSFET
power switch, if used, has similar considerations, but its
The system designer will find the LTC4412HV 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, load sharing between two or
more batteries, charging of multiple batteries from a
single charger and high side power switching.
V
GS 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.
External P-Channel MOSFET Transistor Selection
VIN and SENSE Pin Bypass Capacitors
Important parameters for the selection of MOSFETs are
the maximum drain-source voltage VDS(MAX), threshold
Many types of capacitors, ranging from 0.1µF to 10µF and
locatedclosetotheLTC4412HV, willprovideadequateVIN
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.
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 and the STAT pin sink
current.
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 LTC4412HV’s absolute maxi-
mum 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
MOSFET power dissipation. Keep in mind that the
LTC4412HV 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 minimize power loss and heat dissipation, but it is not
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.
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LTC4412HV
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APPLICATIO S I FOR ATIO
VIN and SENSE Pin Usage
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.
Sincetheanalogcontroller’sthresholdsaresmall(±20mV),
the VIN and SENSE pin connections should be made in a
way to avoid unwanted I • R drops in the power path. Both
pins are protected from negative voltages.
Control 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 LTC4412HV. 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 10µA of current
(IS(SNK)). See the Typical Applications for various ex-
amples 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 elimi-
nated.
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 the higher of VIN or VSENSE and the GATE pin.
Status 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 LTC4412HV. It is usually
connected 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 operation the STAT pin will sink 10µA 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-
Internal protection for the LTC4412HV is provided to
prevent damaging pin currents and excessive internal self
heatingduringafaultcondition.Thesefaultconditionscan
be a result of any LTC4412HV 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
drainordamagetotheIC(seeAbsoluteMaximumVoltage
Limits). This feature allows for reverse-battery condition
without current drain or damage. This internal protection
is not designed to prevent overcurrent or overheating of
external components.
sn4412hv 4412hvfs
8
LTC4412HV
U
TYPICAL APPLICATIO S
Automatic PowerPath Control
Figure 2 illustrates an application circuit for automatic
switchover of load between a battery and a wall adapter
that features lowest power loss. Operation is similar to
Figure 1 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 the wall adapter input is applied,
the drain-source diode of 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.
OncetheauxiliaryMOSFEThasturnedonthevoltagedrop
across it can be very low depending on the MOSFET’s
characteristics.
TheapplicationsshowninFigures1, 2and3areautomatic
ideal diode controllers that require no assistance from a
microcontroller. Each of these will automatically connect
the higher supply voltage, after accounting for certain
diode forward voltage drops, to the load with application
of the higher supply voltage.
Figure 1 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 LTC4412HV 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 LTC4412HV 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 3 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 LTC4412HV’s control
circuitry 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,
insteadofbeingregulatedtomaintaina20mVdropacross
the MOSFET. This has the advantages of minimizing
power loss in the MOSFET by minimizing its RON and not
having the influence 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
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
LTC4412HV
V SENSE
IN
LTC4412HV
1
2
3
6
5
4
V
1
2
3
6
5
4
CC
V
SENSE
IN
GND GATE
CTL STAT
470k
STATUS OUTPUT
IS LOW WHEN A
WALL ADAPTER
IS PRESENT
GND GATE
CTL STAT
470k
STATUS OUTPUT
DROPS WHEN A
WALL ADAPTER
IS PRESENT
4412HV F03
4412HV F02
*DRAIN-SOURCE DIODE OF MOSFET
*DRAIN-SOURCE DIODE OF MOSFET
Figure 2. Automatic Switchover of Load Between a Battery and a
Wall Adapter with Auxiliary P-Channel MOSFET for Lowest Loss
Figure 3. Automatic Switchover of Load Between
a Battery and a Wall Adapter in Comparator Mode
sn4412hv 4412hvfs
9
LTC4412HV
U
TYPICAL APPLICATIO S
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,
rising. 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.
C
OUT capacitancemustbesizedtoholdupVLOAD untilthe
transistion 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
Ideal Diode Control with a Microcontroller
Figure 4 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 LTC4412HV through the CTL input. Back-
to-back MOSFETs are used so that the drain-source diode
willnotpowertheloadwhentheMOSFETisturnedoff(dual
MOSFETs in one package are commercially available).
falls more slowly than VLOAD
.
Load Sharing
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.
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
continue to power the load. Only when the primary
voltageishigherthantheauxiliaryvoltagewilltakingCTL
low switch back to the primary power, otherwise the
WALL
ADAPTER
INPUT
*
AUXILIARY
TO LOAD
P-CHANNEL MOSFETS
BAT1
C
OUT
*
*
LTC4412HV
1
2
3
6
5
4
V
CC
AUXILIARY POWER
SOURCE INPUT
V
SENSE
IN
GND GATE
CTL STAT
470k
470k
STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
MICROCONTROLLER
PRIMARY
P-CHANNEL MOSFETS
LOAD CURRENT
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH BATTERIES ARE
SUPPLYING LOAD CURRENTS. WHEN
BOTH STATUS LINES ARE LOW THEN
WALL ADAPTER IS PRESENT
*
*
TO LOAD
*
C
0.1µF
OUT
BAT2
LTC4412HV
LTC4412HV
PRIMARY
POWER
SOURCE INPUT
1
2
3
6
5
4
V
1
2
3
6
5
4
CC
V
SENSE
V
SENSE
IN
IN
GND GATE
CTL STAT
470k
GND GATE
CTL STAT
STATUS IS HIGH
WHEN BAT2 IS
4412HV F04
4412HV F05
SUPPLYING
LOAD CURRENT
*DRAIN-SOURCE DIODE OF MOSFET
*DRAIN-SOURCE DIODE OF MOSFET
Figure 4. Microcontroller Monitoring and Control
of Two Power Sources
Figure 5. Dual Battery Load Sharing with Automatic
Switchover of Load from Batteries to Wall Adapter
sn4412hv 4412hvfs
10
LTC4412HV
U
TYPICAL APPLICATIO S
Multiple Battery Charging
High Side Power Switch
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
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 7 illustrates an application circuit for a logic con-
trolled high side power switch. When the CTL pin is a
logical low, the LTC4412HV will turn on the MOSFET.
Because the SENSE pin is grounded, the LTC4412HV will
applymaximumclampedgatedrivevoltagetotheMOSFET.
When the CTL pin is a logical high, the LTC4412HV 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.
P-CHANNEL
MOSFET
*
*
TO LOAD OR
PowerPath
BATTERY
CHARGER
INPUT
SUPPLY
TO LOAD
INPUT
CONTROLLER
C
BAT1
OUT
LTC4412HV
LTC4412HV
1
2
3
6
5
1
2
3
6
5
4
V
CC
0.1µF
V
IN
SENSE
V
SENSE
IN
GND GATE
CTL STAT
GND GATE
CTL STAT
470k
STATUS IS HIGH
WHEN BAT1 IS
CHARGING
4
LOGIC
INPUT
4412HV F07
0.1µF
*DRAIN-SOURCE DIODE OF MOSFET
*
TO LOAD OR
PowerPath
CONTROLLER
Figure 7. Logic Controlled High Side Power Switch
BAT2
LTC4412HV
1
2
3
6
5
4
V
CC
V
SENSE
IN
GND GATE
CTL STAT
470k
STATUS IS HIGH
WHEN BAT2 IS
CHARGING
4412HV F06
*DRAIN-SOURCE DIODE OF MOSFET
Figure 6. Automatic Dual Battery Charging
from Single Charging Source
sn4412hv 4412hvfs
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-
tation that the interconnection ofits circuits as described herein willnotinfringe on existing patentrights.
11
LTC4412HV
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
2.90 BSC
(NOTE 4)
0.62
MAX
0.95
REF
1.22 REF
1.4 MIN
1.50 – 1.75
2.80 BSC
3.85 MAX 2.62 REF
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
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
USB Power Manager in ThinSOT
SOT-23 Ideal Diode
Automatic Battery Switchover, Thermal Regulation, Accepts Wall Adapter
and USB Power, 4mm × 4mm QFN
LTC4410
LTC4411
Enables Simultaneous Battery Charging and
Operation of USB Component Peripheral Devices
2.6A Forward Current, 28mV Regulated Forward Voltage
sn4412hv 4412hvfs
LT/TP 0304 1K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
LINEAR TECHNOLOGY CORPORATION 2004
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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