1
LTC4412HV
Rev. B
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36V, Low Loss PowerPathTM
Controller in ThinSOT
■ 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
■ Low Profile (1mm) SOT-23 (ThinSOTTM) Package
■ AEC-Q100 Qualified for Automotive Applications
■ Industrial and Automotive Applications
■ Notebook and Handheld Computers
■ USB-Powered Peripherals
■ Uninterruptable Power Supplies
■ Logic Controlled Power Switch
The LT C
®
4412HV controls an external P-channel MOSFET
to create a near ideal diode function for power switchover
or load sharing. This permits highly efficient OR’ing of
multiple 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 automatically disconnected from the battery when the
auxiliary source is connected. Two or more LTC4412HVs
may be interconnected to allow load sharing between
multiple batteries or charging of multiple batteries from
a single charger. The LTC4412HV is an extended supply
and temperature range version of the LTC4412.
The wide supply operating range supports operation from
one to eight Li-Ion cells in series. The low quiescent cur-
rent (11µA typical) is independent of the load current. The
gate driver includes an internal voltage clamp for MOSFET
protection.
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.
The LTC4412HV is available in a low profile (1mm)
SOT-23 package.
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV C
OUT
TO LOAD
STATUS OUTPUT
LOW WHEN WALL
ADAPTER PRESENT
470k
4412HV F01
V
CC
1N5819
FDN306P
BATTERY
CELL(S)
WALL
ADAPTER
INPUT
Figure1. Automatic Switchover of Load Between a Battery and a Wall Adapter
FORWARD VOLTAGE (V)
0.02
0
CURRENT (A)
1
CONSTANT
RON
4412HV F01b
0.5
CONSTANT
VOLTAGE SCHOTTKY
DIODE
LTC4412HV
LTC4412HV vs Schottky Diode Forward Voltage Drop
All registered trademarks and trademarks are the property of their respective owners.
FEATURES
APPLICATIONS
DESCRIPTION
TYPICAL APPLICATION
2
LTC4412HV
Rev. B
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(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
(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
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN,
VSENSE
Operating Supply Range VIN and/or VSENSE Must Be in This Range
for Proper Operation
l2.5 36 V
IQFL Quiescent Supply Current at Low Supply
While in Forward Regulation
VIN = 3.6V. Measure Combined Current
at VIN and SENSE Pins Averaged with
VSENSE = 3.5V and VSENSE = 3.6V (Note 3)
l11 19 µA
IQFH Quiescent Supply Current at High Supply
While in Forward Regulation
VIN = 36V. Measure Combined Current
at VIN and SENSE Pins Averaged with
VSENSE = 35.9V and VSENSE = 36V (Note 3)
l18 32 µA
IQRL Quiescent Supply Current at Low Supply
While in Reverse Turn-Off
VIN = 3.6V, VSENSE = 3.7V. Measure
Combined Current of VIN and SENSE Pins
10 19 µA
IQRH Quiescent Supply Current at High Supply
While in Reverse Turn-Off
VIN = 35.9V, VSENSE = 36V. Measure
Combined Current of VIN and SENSE Pins
19 33 µA
The l denotes the specifications which apply over the full operating
junction 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.
ORDER INFORMATION
ELECTRICAL CHARACTERISTICS
TAPE AND REEL (MINI) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC4412HVIS6#TRMPBF LTC4412HVIS6#TRPBF LTBHR 6-Lead Plastic TSOT-23 –40°C to 125°C
AUTOMOTIVE PRODUCTS**
LTC4412HVIS6#WTRMPBF
LTC4412HVIS6#WTRPBF LTBHR 6-Lead Plastic TSOT-23 –40°C to 125°C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These
models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your local
Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for thesemodels.
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
VIN 1
GND 2
CTL 3
6 SENSE
5 GATE
4 STAT
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 230°C/W
3
LTC4412HV
Rev. B
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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.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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 4: VIN 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.
Note 5: VIN is held at 12V and SENSE is stepped from 12.2V to 11.8V to
trigger the event. GATE voltage is initially VG(OFF).
Note 6: VIN is held at 12V and SENSE is stepped from 11.8V to 12.2V to
trigger the event. GATE voltage is initially internally clamped at VG(ON).
Note 7: STAT is forced to VIN – 1.5V. SENSE is set at VIN – 0.1V to measure
the off current at STAT. SENSE is set VIN + 0.1V to measure the sink
current at STAT.
Note 8: STAT is forced to 9V and VIN is held at 12V. SENSE is stepped
from 11.8V to 12.2V to measure the STAT turn-on time defined when ISTAT
reaches one half the measured IS(SNK). SENSE is stepped from 12.2V to
11.8V to measure the STAT turn-off time defined when ISTAT reaches one
half the measured IS(SNK) .
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
IQCL Quiescent Supply Current at Low Supply
with CTL Active
VIN = 3.6V, VSENSE = 0V, VCTL = 1V 7 13 µA
IQCH Quiescent Supply Current at High Supply
with CTL Active
VIN = 36V, VSENSE = 8V, VCTL = 1V 15 25 µA
ILEAK VIN and SENSE Pin Leakage Currents
When Other Pin Supplies Power
VIN = 28V, VSENSE = 0V; VSENSE = 28V, VIN = 0V
VIN = 14V, VSENSE = –14V; VSENSE = 14V, VIN = –14V
–3 0 1 µA
PowerPath Controller
VFR PowerPath Switch Forward Regulation
Voltage
VIN – VSENSE, 2.5V ≤ VIN ≤ 36V l10 20 32 mV
VRTO PowerPath Switch Reverse Turn-Off
Threshold Voltage
VSENSE – VIN, 2.5V ≤ VIN ≤ 36V l10 20 32 mV
GATE and STAT Outputs
IG(SRC)
IG(SNK)
GATE Active Forward Regulation
Source Current
Sink Current
(Note 4)
–1
25
–2.5
50
–5
85
µA
µA
VG(ON) GATE Clamp Voltage Apply IGATE = 1µA, VIN = 12V,
VSENSE = 11.9V, Measure VIN – VGATE
6.3 7 7.7 V
VG(OFF) GATE Off Voltage Apply IGATE = – 5µA, VIN = 12V,
VSENSE = 12.1V, Measure VSENSE – VGATE
0.13 0.25 V
tG(ON) GATE Turn-On Time VGS < –3V, CGATE = 1nF (Note 5) 110 175 µs
tG(OFF) GATE Turn-Off Time VGS > –1.5V, CGATE = 1nF (Note 6) 13 22 µs
IS(OFF) STAT Off Current 2.5V ≤ VIN ≤ 36V (Note 7) l–1 0 1 µA
IS(SNK) STAT Sink Current 2.5V ≤ VIN ≤ 36V (Note 7) l6 10 17 µA
tS(ON) STAT Turn-On Time (Note 8) 4.5 25 µs
tS(OFF) STAT Turn-Off Time (Note 8) 40 75 µs
CTL Input
VIL CTL Input Low Voltage 2.5V ≤ VIN ≤ 36V l0.35 V
VIH CTL Input High Voltage 2.5V ≤ VIN ≤ 36V l0.9 V
ICTL CTL Input Pull-Down Current 0.35V ≤ VCTL ≤ 36V 1 3.5 5.9 µA
HCTL CTL Hysteresis 2.5V ≤ VIN ≤ 36V 135 mV
ELECTRICAL CHARACTERISTICS
4
LTC4412HV
Rev. B
For more information www.analog.com
VFR vs Temperature and
Supply Voltage
VRTO vs Temperature and
Supply Voltage
Normalized Quiescent Supply
Current vs Temperature
VIN and SENSE Pin Leakages vs
Temperature and Supply Voltage VG(ON) vs Temperature
VG(OFF) vs Temperature and IGATE
tG(ON) vs Temperature and
Supply Voltage
tG(OFF) vs Temperature and
Supply Voltage IS(SNK) vs Temperature and VIN
TEMPERATURE (C)
–50
VFR (mV)
22
20
18 25 75
4412HV G01
–25 0 50 100 125
VIN = 2.5V
VIN = 28V
VIN = 36V
TEMPERATURE (C)
–50
VRTO (mV)
22
20
18 25 75
4412HV G02
–25 0 50 100 125
VIN = 2.5V
VIN = 28V
VIN = 36V
TEMPERATURE (C)
–50
CURRENT (A)
1.05
1.0
0.95 25 75
4412HV G03
–25 0 50 100 125
3.6V VIN 36V
TEMPERATURE (C)
–50
CURRENT (A)
0
–1
–2
–3
–4
–5 25 75
4412HV G04
–25 0 50 100 125
ILEAK
IVIN: VSENSE = 36V, VIN = 0V
IVIN: VSENSE = 24V, VIN = –14V
ISENSE: VIN = 36V, VSENSE = 0V
ISENSE: VIN = 24V, VSENSE = –14V
TEMPERATURE (C)
–50
VOLTAGE (V)
7.1
7.0
6.9 25 75
4412HV G05
–25 0 50 100 125
8V VIN 36V
IGATE = 1A
TEMPERATURE (C)
–50
VOLTAGE (V)
0.25
0.20
0.15
0.10
0.05
0
25 75
4412HV G06
–25 0 50 100 125
2.5V VIN 36V
IGATE = –10A
IGATE = –5A
IGATE = 0A
TEMPERATURE (C)
–50
TIME (s)
120
110
90
100
25 75
4412HV G07
–25 0 50 100 125
VIN = 12V
VIN = 24V
VIN = 30V
VIN = 36V
TEMPERATURE (C)
–50
CURRENT (A)
10.5
10.0
9.5 25 75
4412HV G09
–25 0 50 100 125
VSTAT = VIN – 1.5V
VIN = 36V
VIN = 2.5V
TEMPERATURE (C)
–50
TIME (s)
15
14
13
12
11
10 25 75
4412HV G08
–25 0 50 100 125
VIN = 12V
VIN = 36V
TYPICAL PERFORMANCE CHARACTERISTICS
5
LTC4412HV
Rev. B
For more information www.analog.com
VIN (Pin 1): Primary Input Supply Voltage. Supplies power
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 sup
-
plied power from a battery or other power source which
supplies current to the load. This pin can be bypassed to
ground with a capacitor in the range of 0.1µF to 10µF if
needed to suppress load transients.
GND (Pin 2): Ground. Provides a power return for all the
internal circuits.
CTL (Pin 3): Digital Control Input. A logical high input
(VIH) on this pin forces the gate to source voltage of the
primary P-channel MOSFET power switch to a small
voltage (V
GOFF
). This will turn the MOSFET off and no
current will flow from the primary power input at VIN if
the MOSFET is configured 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, such as an AC wall
adaptor, will be connected to the load (see Applications
Information). An internal current sink will pull the CTL pin
voltage to ground (logical low) if the pin is open.
STAT (Pin 4): Open-Drain Output Status Pin. When the
SENSE pin is pulled above the VIN pin with an auxiliary
power source by about 20mV or more, the reverse turn-
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.
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.
SENSE (Pin 6): Power Sense Input Pin. Supplies power
to the internal circuitry and is a voltage sense input to the
internal analog controller (The other input to the controller
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.
PIN FUNCTIONS
6
LTC4412HV
Rev. B
For more information www.analog.com
–
+
1 6
SOURCE
POWER
VOLTAGE/CURRENT
REFERENCE
0.5V
POWER
LINEAR GATE
DRIVER AND
VOLTAGE CLAMP
A1
VIN SENSE
ANALOG CONTROLLER
–
+
C1
3
2
CTL
3.5A
ON/OFF
10A
*DRAIN-SOURCE DIODE OF MOSFET
STATUS
OUTPUT
4412HV BD
ON/OFF
STAT
VCC
GATE
4
5
GND
OUTPUT
TO LOAD
SELECTOR
–
+
PRIMARY
SUPPLY
–
+
AUXILIARY
SUPPLY
–
+
PIN FUNCTIONS
7
LTC4412HV
Rev. B
For more information www.analog.com
Operation can best be understood by referring to the Block
Diagram, which illustrates the internal circuit blocks along
with the few external components, and the graph that
accompanies Figure1. The terms primary and auxiliary
are 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 pres-
ent, 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 V
IN
– 20mV (V
FR
), the
Analog Controller will instruct the Linear Gate Driver and
Voltage Clamp block to pull down the GATE pin voltage
and turn on the external P-channel MOSFET. The dynamic
pull-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 volt-
age will be 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, the MOSFET will behave as a fixed resistor
and the forward voltage will increase slightly. While the
MOSFET is on the STAT pin is an open circuit.
When an auxiliary supply is applied, the SENSE pin will be
pulled higher than the VIN pin through the external diode.
The Power Source Selector will power the LTC4412HV
from the SENSE pin. As the SENSE voltage pulls above
V
IN
– 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 pri-
mary 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 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.
When the CTL (control) input is asserted high, the external
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.
OPERATION
8
LTC4412HV
Rev. B
For more information www.analog.com
Introduction
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
switchover from a primary to an auxiliary source of power,
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.
External P-Channel MOSFET Transistor Selection
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
is set by the smaller of the VIN supply voltage or the
internal clamping voltage VG(ON). A logic level MOSFET
is commonly 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.
As a general rule, select a MOSFET with a low enough
RDS(ON) to obtain the desired VDS while operating at full
load current and an achievable V
GS
. The MOSFET nor-
mally 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 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 dis-
sipation. Care should be taken to ensure that the power
dissipated is never allowed to rise above the manufactur-
er’s recommended 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 cur-
rent (IS(SNK) ) that may flow through it.
VIN and SENSE Pin Bypass Capacitors
Many types of capacitors, ranging from 0.1µF to 10µF and
located close to the LTC4412HV, will provide adequate
VIN bypassing if needed. Voltage droop can occur at the
load during a supply switchover because some time is
required to turn on the MOSFET power switch. Factors
that determine the magnitude of the voltage droop include
the supply rise and fall times, the MOSFET’s characteris-
tics, the value of COUT and the load current. Droop can be
made insignificant by the proper choice of C
OUT
,
since the
droop is inversely proportional to the capacitance. Bypass
capacitance 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.
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.
The selected capacitance value and capacitor’s ESR can
be verified by observing VIN and SENSE for acceptable
voltage 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.
APPLICATIONS INFORMATION
9
LTC4412HV
Rev. B
For more information www.analog.com
VIN and SENSE Pin Usage
Since the analog controller’s thresholds are small
(±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.
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 V
IN
. 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
currents 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).
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 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 aux-
iliary 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 oper-
ation 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 microcontrol-
ler that an auxiliary power source is connected. 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.
Control Pin Usage
This is a digital control input pin with low threshold volt-
ages (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 pri-
mary P-channel MOSFET power switch to a small voltage
(VGOFF). This will turn the MOSFET off and no current will
flow from the primary power input at V
IN
if the MOSFET is
configured so that the drain to source diode is not forward
biased. The high input also forces the STAT pin to sink
10µA 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 log-
ical low level input if the pin should be open.
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
protect shorted supplies but can isolate other supplies
and the load from faults. A necessary condition of this
protection is for all components to have sufficient break-
down voltages. In some cases, if protection of the aux-
iliary input (sometimes referred to as the wall adapter
input) is not required, then the series diode or MOSFET
may be eliminated.
Internal protection for the LTC4412HV is provided to pre
-
vent damaging pin currents and excessive internal self
heating during a fault condition. These fault conditions
can 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 drain or damage to the IC (see Absolute Maximum
Voltage Limits). This feature allows for reverse-battery
condition without current drain or damage. This internal
protection is not designed to prevent overcurrent or over-
heating of external components.
APPLICATIONS INFORMATION
10
LTC4412HV
Rev. B
For more information www.analog.com
Automatic PowerPath Control
The applications shown in Figures 1, 2 and 3 are auto-
matic 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
Schottky diode will pull up the SENSE pin, connected to
the 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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 bat-
tery 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. Once the auxiliary MOSFET has turned on the
voltage drop across it can be very low depending on the
MOSFET’s characteristics.
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 char-
ger 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 volt-
age 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 hav-
ing 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
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
PRIMARY
P-CHANNEL
MOSFET
C
OUT
TO LOAD
STATUS OUTPUT
DROPS WHEN A
WALL ADAPTER
IS PRESENT
470k
4412HV F02
BATTERY
CELL(S)
WALL
ADAPTER
INPUT
*
*
AUXILIARY
P-CHANNEL
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
VIN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
BATTERY
CHARGER
P-CHANNEL
MOSFET
COUT
TO LOAD
STATUS OUTPUT
IS LOW WHEN A
WALL ADAPTER
IS PRESENT
470k
*DRAIN-SOURCE DIODE OF MOSFET
4412HV F03
VCC
BATTERY
CELL(S)
*
WALL
ADAPTER
INPUT
Figure3. Automatic Switchover of Load Between
a Battery and a Wall Adapter in Comparator Mode
TYPICAL APPLICATIONS
11
LTC4412HV
Rev. B
For more information www.analog.com
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.
Ideal Diode Control with a Microcontroller
Figure4 illustrates an application circuit for microcon-
troller 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 will not power the load when the MOSFET
is turned off (dual MOSFETs in one package are commer-
cially available).
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
voltage is higher than the auxiliary voltage will taking
CTL low switch back to the primary power, otherwise
the auxiliary stays connected. When the primary power
is disconnected and VIN falls below VLOAD, it will turn
on the auxiliary MOSFET if CTL is low, but VLOAD must
stay up long enough for the MOSFET to turn on. At a
minimum, COUT capacitance must be sized to hold up
VLOAD until the transistion between the sets of MOSFETs
is complete. Sufficient capacitance on the load and low
or no capacitance 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.
Load Sharing
Figure5 illustrates an application circuit for dual battery
load sharing with automatic switchover of load from bat-
teries to wall adapter. Whichever battery can supply the
higher voltage will provide the load current until it is dis-
charged to the voltage of the other battery. The load will
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 STAT pins provide information as to which input is
supplying the load current. This concept can be expanded
to more power inputs.
VIN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV COUT
TO LOAD
STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
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
STATUS IS HIGH
WHEN BAT2 IS
SUPPLYING
LOAD CURRENT
470k
4412HV F05
VCC
BAT1
WALL
ADAPTER
INPUT
VIN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
470k
VCC
BAT2
*
*
*DRAIN-SOURCE DIODE OF MOSFET
Figure5. Dual Battery Load Sharing with Automatic
Switchover of Load from Batteries to Wall Adapter
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
*DRAIN-SOURCE DIODE OF MOSFET
PRIMARY
P-CHANNEL MOSFETS
C
OUT
TO LOAD
4412HV F04
AUXILIARY POWER
SOURCE INPUT
*
*
*
*
PRIMARY
POWER
SOURCE INPUT
AUXILIARY
P-CHANNEL MOSFETS
470k
MICROCONTROLLER
0.1F
Figure4. Microcontroller Monitoring and Control
of Two Power Sources
TYPICAL APPLICATIONS
12
LTC4412HV
Rev. B
For more information www.analog.com
Multiple Battery Charging
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
current until both battery voltages are equal, then both
will be charged. When both are charged simultaneously,
the higher capacity battery will get proportionally higher
current from the charger. For Li-Ion batteries, both batter-
ies will achieve the float voltage minus the forward reg-
ulation 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 con-
trol, 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.
VIN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
P-CHANNEL
MOSFET
SUPPLY
INPUT
LOGIC
INPUT
COUT
*
TO LOAD
4412HV F07
*DRAIN-SOURCE DIODE OF MOSFET
0.1F
Figure7. Logic Controlled High Side Power Switch
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 log-
ical low, the LTC4412HV will turn on the MOSFET. Because
the SENSE pin is grounded, the LTC4412HV will apply
maximum clamped gate drive voltage to the MOSFET.
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 supplying voltage to the load when the MOSFET is
off. 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.
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
TO LOAD OR
PowerPath
CONTROLLER
TO LOAD OR
PowerPath
CONTROLLER
STATUS IS HIGH
WHEN BAT1 IS
CHARGING
STATUS IS HIGH
WHEN BAT2 IS
CHARGING
470k
4412HV F06
V
CC
*
*
BAT1
BATTERY
CHARGER
INPUT
470k
V
CC
BAT2
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412HV
*DRAIN-SOURCE DIODE OF MOSFET
0.1F
Figure6. Automatic Dual Battery Charging
from Single Charging Source
TYPICAL APPLICATIONS
13
LTC4412HV
Rev. B
For more information www.analog.com
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
B 10/20 Added AEC-Q100 qualification and #W part numbers. 1, 2
14
LTC4412HV
Rev. B
For more information www.analog.com
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.30 – 0.45
6 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 – 0.90
1.00 MAX 0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
PIN ONE ID
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
3.85 MAX
0.62
MAX
0.95
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
PACKAGE DESCRIPTION
ANALOG DEVICES, INC. 2004–2020
www.analog.com
10/20
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