LTC4412HV

36V, Low Loss PowerPathTM

Controller in ThinSOT
U
FEATURES DESCRIPTIO
■ Very Low Loss Replacement for Power Supply The LTC®4412HV controls an external P-channel MOSFET
OR’ing Diodes to create a near ideal diode function for power switchover
■ 3V to 36V AC/DC Adapter Voltage Range or load sharing. This permits highly efficient OR’ing of mul-
■ –40°C to 125°C Operating Temperature Range tiple power sources for extended battery life and low self-
■ Minimal External Components heating. When conducting, the voltage drop across the
■ Automatic Switching Between DC Sources MOSFET is typically 20mV. For applications with a wall
■ Simplifies Load Sharing with Multiple Batteries adapter or other auxiliary power source, the load is auto-
■ Low Quiescent Current: 11µA matically disconnected from the battery when the auxiliary
■ 2.5V to 36V Battery Voltage Range source is connected. Two or more LTC4412HVs may be in-
■ Reverse Battery Protection terconnected to allow load sharing between multiple bat-
■ Drives Almost Any Size MOSFET for Wide Range of teries or charging of multiple batteries from a single charger.
Current Requirements The LTC4412HV is an extended supply and temperature
■ MOSFET Gate Protection Clamp range version of the LTC4412.
■ Manual Control Input
The wide supply operating range supports operation from
■ Low Profile (1mm) SOT-23 (ThinSOTTM) Package
one to eight Li-Ion cells in series. The low quiescent
U current (11µA typical) is independent of the load current.
APPLICATIO S The gate driver includes an internal voltage clamp for
■ Industrial and Automotive Applications MOSFET protection.
■ Notebook and Handheld Computers The STAT pin can be used to enable an auxiliary P-channel
■ USB-Powered Peripherals MOSFET power switch when an auxiliary supply is
■ Uninterruptable Power Supplies detected. This pin may also be used to indicate to a micro-
■ Logic Controlled Power Switch controller that an auxiliary supply is connected. The con-
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath and ThinSOT are trademarks of Linear Technology Corporation.
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.

U LTC4412HV vs Schottky Diode Forward Voltage Drop

TYPICAL APPLICATIO
1

1N5819 CONSTANT
WALL RON
ADAPTER
INPUT FDN306P
CURRENT (A)

TO LOAD
BATTERY LTC4412HV
CELL(S) COUT
LTC4412HV
1 6 VCC
VIN SENSE
CONSTANT
2 5
GND GATE 470k VOLTAGE
STATUS OUTPUT SCHOTTKY
3 4
CTL STAT LOW WHEN WALL DIODE
4412HV F01
ADAPTER PRESENT

0
Figure 1. Automatic Switchover of Load Between a Battery and a Wall Adapter 0.02 0.5
FORWARD VOLTAGE (V) 4412HV F01b

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LTC4412HV
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ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION
(Note 1)
Supply Voltage (VIN) .................................. –14V to 40V ORDER PART
Voltage from VIN to SENSE ........................ – 40V to 40V NUMBER
Input Voltage
CTL ........................................................– 0.3V to 40V TOP VIEW LTC4412HVIS6
SENSE .................................................... –14V to 40V VIN 1 6 SENSE

Output Voltage GND 2 5 GATE

CTL 3 4 STAT
GATE ..................... –0.3V to the Higher of VIN + 0.3V
or SENSE + 0.3V S6 PACKAGE S6 PART MARKING
6-LEAD PLASTIC TSOT-23
STAT .....................................................– 0.3V to 40V TJMAX = 125°C, θJA = 230°C/W
Operating Ambient Temperature Range LTBHR
(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 MIN TYP MAX UNITS
VIN, Operating Supply Range VIN and/or VSENSE Must Be in This Range ● 2.5 36 V
VSENSE for Proper Operation
IQFL Quiescent Supply Current at Low Supply VIN = 3.6V. Measure Combined Current ● 11 19 µA
While in Forward Regulation at VIN and SENSE Pins Averaged with
VSENSE = 3.5V and VSENSE = 3.6V (Note 3)
IQFH Quiescent Supply Current at High Supply VIN = 36V. Measure Combined Current ● 18 32 µA
While in Forward Regulation at VIN and SENSE Pins Averaged with
VSENSE = 35.9V and VSENSE = 36V (Note 3)
IQRL Quiescent Supply Current at Low Supply VIN = 3.6V, VSENSE = 3.7V. Measure 10 19 µA
While in Reverse Turn-Off Combined Current of VIN and SENSE Pins
IQRH Quiescent Supply Current at High Supply VIN = 35.9V, VSENSE = 36V. Measure 19 33 µA
While in Reverse Turn-Off Combined Current of VIN and SENSE Pins
IQCL Quiescent Supply Current at Low Supply VIN = 3.6V, VSENSE = 0V, VCTL = 1V 7 13 µA
with CTL Active
IQCH Quiescent Supply Current at High Supply VIN = 36V, VSENSE = 8V, VCTL = 1V 15 25 µA
with CTL Active
ILEAK VIN and SENSE Pin Leakage Currents VIN = 28V, VSENSE = 0V; VSENSE = 28V, VIN = 0V –3 0 1 µA
When Other Pin Supplies Power VIN = 14V, VSENSE = –14V; VSENSE = 14V, VIN = –14V
PowerPath Controller
VFR PowerPath Switch Forward Regulation VIN – VSENSE, 2.5V ≤ VIN ≤ 36V ● 10 20 32 mV
Voltage
VRTO PowerPath Switch Reverse Turn-Off VSENSE – VIN, 2.5V ≤ VIN ≤ 36V ● 10 20 32 mV
Threshold Voltage

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 LTC4412HV
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 MIN TYP MAX UNITS
GATE and STAT Outputs
GATE Active Forward Regulation (Note 4)
IG(SRC) Source Current –1 –2.5 –5 µA
IG(SNK) Sink Current 25 50 85 µA
VG(ON) GATE Clamp Voltage Apply IGATE = 1µA, VIN = 12V, 6.3 7 7.7 V
VSENSE = 11.9V, Measure VIN – VGATE
VG(OFF) GATE Off Voltage Apply IGATE = – 5µA, VIN = 12V, 0.13 0.25 V
VSENSE = 12.1V, Measure VSENSE – VGATE
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) ● –1 0 1 µA
IS(SNK) STAT Sink Current 2.5V ≤ VIN ≤ 36V (Note 7) ● 6 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 ● 0.35 V
VIH CTL Input High Voltage 2.5V ≤ VIN ≤ 36V ● 0.9 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
Note 1: Absolute Maximum Ratings are those values beyond which the life Note 6: VIN is held at 12V and SENSE is stepped from 11.8V to 12.2V to
of a device may be impaired. trigger the event. GATE voltage is initially internally clamped at VG(ON).
Note 2: The LTC4412HV is guaranteed to meet performance specifications Note 7: STAT is forced to VIN – 1.5V. SENSE is set at VIN – 0.1V to
over the – 40°C to 125°C operating ambient temperature range. measure the off current at STAT. SENSE is set VIN + 0.1V to measure the
Note 3: This results in the same supply current as would be observed with sink current at STAT.
an external P-channel MOSFET connected to the LTC4412HV and Note 8: STAT is forced to 9V and VIN is held at 12V. SENSE is stepped
operating in forward regulation. from 11.8V to 12.2V to measure the STAT turn-on time defined when ISTAT
Note 4: VIN is held at 12V and GATE is forced to 10.5V. SENSE is set at reaches one half the measured IS(SNK). SENSE is stepped from 12.2V to
12V to measure the source current at GATE. SENSE is set at 11.9V to 11.8V to measure the STAT turn-off time defined when ISTAT reaches one
measure sink current at GATE. half the measured IS(SNK) .
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).

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LTC4412HV
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TYPICAL PERFOR A CE CHARACTERISTICS
VFR vs Temperature and VRTO vs Temperature and Normalized Quiescent Supply
Supply Voltage Supply Voltage Current vs Temperature
22 22 1.05

VIN = 2.5V VIN = 36V

3.6V ≤ VIN ≤ 36V

CURRENT (µA)
VIN = 28V

VRTO (mV)
VFR (mV)

20 VIN = 28V 20 1.0

VIN = 2.5V
VIN = 36V

18 18 0.95
–50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)
4412HV G01 4412HV G02 4412HV G03

VIN and SENSE Pin Leakages vs

Temperature and Supply Voltage VG(ON) vs Temperature VG(OFF) vs Temperature and IGATE
0 7.1 0.25
ILEAK 8V ≤ VIN ≤ 36V 2.5V ≤ VIN ≤ 36V
IGATE = 1µA
–1 0.20
IGATE = –10µA
IVIN: VSENSE = 36V, VIN = 0V
CURRENT (µA)

VOLTAGE (V)

VOLTAGE (V) 0.15

–2
IGATE = –5µA
IVIN: VSENSE = 24V, VIN = –14V 7.0
0.10 IGATE = 0µA
–3
ISENSE: VIN = 36V, VSENSE = 0V

–4 0.05
ISENSE: VIN = 24V, VSENSE = –14V

–5 6.9 0
–50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)
4412HV G04 4412HV G05 4412HV G06

tG(ON) vs Temperature and tG(OFF) vs Temperature and

Supply Voltage Supply Voltage IS(SNK) vs Temperature and VIN
120 15 10.5
VSTAT = VIN – 1.5V
VIN = 12V
14
VIN = 24V
VIN = 12V
110
CURRENT (µA)

VIN = 36V
13
TIME (µs)
TIME (µs)

VIN = 30V
10.0
VIN = 36V VIN = 2.5V
12
100 VIN = 36V

11

90 10 9.5
–50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)
4412HV G07 4412HV G08 4412HV G09

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 LTC4412HV
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PI FU CTIO S
VIN (Pin 1): Primary Input Supply Voltage. Supplies power STAT (Pin 4): Open-Drain Output Status Pin. When the
to the internal circuitry and is one of two voltage sense SENSE pin is pulled above the VIN pin with an auxiliary
inputs to the internal analog controller (The other input to power source by about 20mV or more, the reverse turn-off
the controller is the SENSE pin). This input is usually threshold (VRTO) is reached. The STAT pin will then go
supplied power from a battery or other power source from an open state to a 10µA current sink (IS(SNK)). The
which supplies current to the load. This pin can be by- STAT pin current sink can be used, along with an external
passed to ground with a capacitor in the range of 0.1µF to resistor, to turn on an auxiliary P-channel power switch
10µF if needed to suppress load transients. 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
CTL (Pin 3): Digital Control Input. A logical high input (VIH)
to maintain a forward regulation voltage (VFR) of 20mV
on this pin forces the gate to source voltage of the primary
between the VIN and SENSE pins when an auxiliary power
P-channel MOSFET power switch to a small voltage (VGOFF).
source is not present. When an auxiliary power source is
This will turn the MOSFET off and no current will flow from
connected, the GATE pin will pull up to the SENSE pin
the primary power input at VIN if the MOSFET is configured
voltage, turning off the primary P-channel power switch.
so that the drain to source diode does not forward bias. A
high input also forces the STAT pin to sink 10µA of current SENSE (Pin 6): Power Sense Input Pin. Supplies power to
(IS(SNK)). If the STAT pin is used to control an auxiliary P- the internal circuitry and is a voltage sense input to the
channel power switch, then a second active source of internal analog controller (The other input to the controller
power, such as an AC wall adaptor, will be connected to the is the VIN pin). This input is usually supplied power from
load (see Applications Information). An internal current an auxiliary source such as an AC adapter or back-up
sink will pull the CTL pin voltage to ground (logical low) if battery which also supplies current to the load.
the pin is open.

W
BLOCK DIAGRA +
AUXILIARY
SUPPLY
–
+ + OUTPUT
PRIMARY
SUPPLY
– – TO LOAD

1 6
VIN SENSE

– +
POWER SOURCE
A1
SELECTOR

POWER

VOLTAGE/CURRENT LINEAR GATE GATE

REFERENCE DRIVER AND 5
0.5V VOLTAGE CLAMP
VCC

CTL
ON/OFF 3 + STAT
4
STATUS
OUTPUT
3.5µA C1 ANALOG CONTROLLER ON/OFF
10µA
–

GND 4412HV BD
2

*DRAIN-SOURCE DIODE OF MOSFET

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LTC4412HV
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OPERATIO
Operation can best be understood by referring to the Block The Power Source Selector will power the LTC4412HV
Diagram, which illustrates the internal circuit blocks along from the SENSE pin. As the SENSE voltage pulls above
with the few external components, and the graph that VIN – 20mV, the Analog Controller will instruct the Linear
accompanies Figure 1. The terms primary and auxiliary are Gate Driver and Voltage Clamp block to pull the GATE
arbitrary and may be changed to suit the application. voltage up to turn off the P-channel MOSFET. When the
Operation begins when either or both power sources are voltage on SENSE is higher than VIN + 20mV (VRTO), the
applied and the CTL control pin is below the input low Analog Controller will instruct the Linear Gate Driver and
voltage of 0.35V (VIL). If only the primary supply is Voltage Clamp block to rapidly pull the GATE pin voltage
present, the Power Source Selector will power the to the SENSE pin voltage. This action will quickly finish
LTC4412HV from the VIN pin. Amplifier A1 will deliver a turning off the external P-channel MOSFET if it hasn’t
current to the Analog Controller block that is proportional already turned completely off. For a clean transistion, the
to the voltage difference in the VIN and SENSE pins. While reverse turn-off threshold has hysteresis to prevent
the voltage on SENSE is lower than VIN – 20mV (VFR), the uncertainty. The system is now in the reverse turn-off
Analog Controller will instruct the Linear Gate Driver and mode. Power to the load is being delivered through the
Voltage Clamp block to pull down the GATE pin voltage and external diode and no current is drawn from the primary
turn on the external P-channel MOSFET. The dynamic pull- supply. The external diode provides protection in case
down current of 50µA (IG(SNK)) stops when the GATE the auxiliary supply is below the primary supply, sinks
voltage reaches ground or the gate clamp voltage. The current to ground or is connected reverse polarity. Dur-
gate clamp voltage is 7V (VG(ON)) below the higher of VIN ing the reverse turn-off mode of operation the STAT pin
or VSENSE. As the SENSE voltage pulls up to VIN – 20mV, will sink 10µA of current (IS(SNK)) if connected. Note that
the LTC4412HV will regulate the GATE voltage to maintain the external MOSFET is wired so that the drain to source
a 20mV difference between VIN and VSENSE which is also diode will momentarily forward bias when power is first
the VDS of the MOSFET. The system is now in the forward applied to VIN and will become reverse biased when an
regulation mode and the load will be powered from the auxiliary supply is applied.
primary supply. As the load current varies, the GATE When the CTL (control) input is asserted high, the external
voltage will be controlled to maintain the 20mV difference. MOSFET will have its gate to source voltage forced to a
If the load current exceeds the P-channel MOSFET’s ability small voltage VG(OFF) and the STAT pin will sink 10µA of
to deliver the current with a 20mV VDS the GATE voltage current if connected. This feature is useful to allow control
will clamp, the MOSFET will behave as a fixed resistor and input switching of the load between two power sources as
the forward voltage will increase slightly. While the MOSFET shown in Figure 4 or as a switchable high side driver as
is on the STAT pin is an open circuit.
shown in Figure 7. A 3.5µA internal pull- down current
When an auxiliary supply is applied, the SENSE pin will be (ICTL) on the CTL pin will insure a low level input if the pin
pulled higher than the VIN pin through the external diode. should become open.

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 LTC4412HV
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APPLICATIO S I FOR ATIO
Introduction a necessity. If a forward voltage drop of more than 20mV
The system designer will find the LTC4412HV useful in a is acceptable then a smaller MOSFET can be used, but
must be sized compatible with the higher power dissipa-
variety of cost and space sensitive power control applica-
tions that include low loss diode OR’ing, fully automatic tion. Care should be taken to ensure that the power
switchover from a primary to an auxiliary source of power, dissipated is never allowed to rise above the manufacturer’s
recommended maximum level. The auxiliary MOSFET
microcontroller controlled switchover from a primary to
power switch, if used, has similar considerations, but its
an auxiliary source of power, load sharing between two or
more batteries, charging of multiple batteries from a VGS can be tailored by resistor selection. When choosing
the resistor value consider the full range of STAT pin
single charger and high side power switching.
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
located close to the LTC4412HV, will provide adequate VIN
voltage VGS(VT) and on-resistance RDS(ON).
bypassing if needed. Voltage droop can occur at the load
The maximum allowable drain-source voltage, VDS(MAX), during a supply switchover because some time is required
must be high enough to withstand the maximum drain- to turn on the MOSFET power switch. Factors that deter-
source voltage seen in the application. mine the magnitude of the voltage droop include the
The maximum gate drive voltage for the primary MOSFET supply rise and fall times, the MOSFET’s characteristics,
is set by the smaller of the VIN supply voltage or the internal the value of COUT and the load current. Droop can be made
clamping voltage VG(ON). A logic level MOSFET is com- insignificant by the proper choice of COUT, since the droop
monly used, but if a low supply voltage limits the gate is inversely proportional to the capacitance. Bypass ca-
voltage, a sub-logic level threshold MOSFET should be pacitance for the load also depends on the application’s
considered. The maximum gate drive voltage for the dynamic load requirements and typically ranges from 1µF
auxiliary MOSFET, if used, is determined by the external to 47µF. In all cases, the maximum droop is limited to the
resistor connected to the STAT pin and the STAT pin sink drain source diode forward drop inside the MOSFET.
current. Caution must be exercised when using multilayer ceramic
As a general rule, select a MOSFET with a low enough capacitors. Because of the self resonance and high Q
RDS(ON) to obtain the desired VDS while operating at full characteristics of some types of ceramic capacitors, high
load current and an achievable VGS. The MOSFET normally voltage transients can be generated under some start-up
operates in the linear region and acts like a voltage conditions such as connecting a supply input to a hot
controlled resistor. If the MOSFET is grossly undersized, power source. To reduce the Q and prevent these tran-
it can enter the saturation region and a large VDS may sients from exceeding the LTC4412HV’s absolute maxi-
result. However, the drain-source diode of the MOSFET, if mum voltage rating, the capacitor’s ESR can be increased
forward biased, will limit VDS. A large VDS, combined with by adding up to several ohms of resistance in series with
the load current, will likely result in excessively high the ceramic capacitor. Refer to Application Note 88.
MOSFET power dissipation. Keep in mind that the The selected capacitance value and capacitor’s ESR can be
LTC4412HV will regulate the forward voltage drop across verified by observing VIN and SENSE for acceptable volt-
the primary MOSFET at 20mV if RDS(ON) is low enough. age transitions during dynamic conditions over the full
The required RDS(ON) can be calculated by dividing 0.02V load current range. This should be checked with each
by the load current in amps. Achieving forward regulation power source as well. Ringing may indicate an incorrect
will minimize power loss and heat dissipation, but it is not 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
Since the analog controller’s thresholds are small (±20mV),
resistor when the STAT pin is either on or off.
the VIN and SENSE pin connections should be made in a
way to avoid unwanted I • R drops in the power path. Both
Control Pin Usage
pins are protected from negative voltages.
This is a digital control input pin with low threshold
GATE Pin Usage voltages (VIL,VIH) for use with logic powered from as little
as 1V. During normal operation, the CTL pin can be biased
The GATE pin controls the external P-channel MOSFET
at any voltage between ground and 36V, regardless of the
connected between the VIN and SENSE pins when the load
supply voltage to the LTC4412HV. A logical high input on
current is supplied by the power source at VIN. In this
this pin forces the gate to source voltage of the primary
mode of operation, the internal current source, which is
responsible for pulling the GATE pin up, is limited to a few P-channel MOSFET power switch to a small voltage (VGOFF).
microamps (IG(SRC)). If external opposing leakage cur- This will turn the MOSFET off and no current will flow from
the primary power input at VIN if the MOSFET is configured
rents exceed this, the GATE pin voltage will reach the
so that the drain to source diode is not forward biased. The
clamp voltage (VGON) and VDS will be smaller. The internal
high input also forces the STAT pin to sink 10µA of current
current sink, which is responsible for pulling the GATE pin
(IS(SNK)). See the Typical Applications for various ex-
down, has a higher current capability (IG(SNK)). With an
amples on using the STAT pin. A 3.5µA internal pull-down
auxiliary supply input pulling up on the SENSE pin and
current (ICTL) on the CTL pin will insure a logical low level
exceeding the VIN pin voltage by 20mV (VRTO), the device
input if the pin should be open.
enters the reverse turn-off mode and a much stronger
current source is available to oppose external leakage Protection
currents and turn off the MOSFET (VGOFF).
Most of the application circuits shown provide some
While in forward regulation, if the on resistance of the protection against supply faults such as shorted, low or
MOSFET is too high to maintain forward regulation, the reversed supply inputs. The fault protection does not
GATE pin will maximize the MOSFET’s VGS to that of the protect shorted supplies but can isolate other supplies and
clamp voltage (VGON). The clamping action takes place the load from faults. A necessary condition of this protec-
between the higher of VIN or VSENSE and the GATE pin. tion is for all components to have sufficient breakdown
voltages. In some cases, if protection of the auxiliary input
Status Pin Usage
(sometimes referred to as the wall adapter input) is not
During normal operation, the open-drain STAT pin can be required, then the series diode or MOSFET may be elimi-
biased at any voltage between ground and 36V regardless nated.
of the supply voltage to the LTC4412HV. It is usually
Internal protection for the LTC4412HV is provided to
connected to a resistor whose other end connects to a
voltage source. In the forward regulation mode, the STAT prevent damaging pin currents and excessive internal self
pin will be open (IS(OFF)). When a wall adaptor input or heating during a fault condition. These fault conditions can
other auxiliary supply is connected to that input, and the be a result of any LTC4412HV pins shorted to ground or to
voltage on SENSE is higher than VIN + 20mV (VRTO), the a power source that is within the pin’s absolute maximum
system is in the reverse turn-off mode. During this mode voltage limits. Both the VIN and SENSE pins are capable of
being taken significantly below ground without current
of operation the STAT pin will sink 10µA of current
drain or damage to the IC (see Absolute Maximum Voltage
(IS(SNK)). This will result in a voltage change across the
Limits). This feature allows for reverse-battery condition
resistor, depending on the resistance, which is useful to
without current drain or damage. This internal protection
turn on an auxiliary P-channel MOSFET or signal to a
is not designed to prevent overcurrent or overheating of
microcontroller that an auxiliary power source is con-
external components.
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 LTC4412HV
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TYPICAL APPLICATIO S
Automatic PowerPath Control Figure 2 illustrates an application circuit for automatic
The applications shown in Figures 1, 2 and 3 are automatic switchover of load between a battery and a wall adapter
ideal diode controllers that require no assistance from a that features lowest power loss. Operation is similar to
microcontroller. Each of these will automatically connect Figure 1 except that an auxiliary P-channel MOSFET
the higher supply voltage, after accounting for certain replaces the diode. The STAT pin is used to turn on the
diode forward voltage drops, to the load with application MOSFET once the SENSE pin voltage exceeds the battery
of the higher supply voltage. voltage by 20mV. When the wall adapter input is applied,
the drain-source diode of the auxiliary MOSFET will turn
Figure 1 illustrates an application circuit for automatic on first to pull up the SENSE pin and turn off the primary
switchover of a load between a battery and a wall adapter MOSFET followed by turning on of the auxiliary MOSFET.
or other power input. With application of the battery, the Once the auxiliary MOSFET has turned on the voltage drop
load will initially be pulled up by the drain-source diode of across it can be very low depending on the MOSFET’s
the P-channel MOSFET. As the LTC4412HV comes into characteristics.
action, it will control the MOSFET’s gate to turn it on and
reduce the MOSFET’s voltage drop from a diode drop to Figure 3 illustrates an application circuit for the automatic
20mV. The system is now in the low loss forward regula- switchover of a load between a battery and a wall adapter
tion mode. Should the wall adapter input be applied, the in the comparator mode. It also shows how a battery
Schottky diode will pull up the SENSE pin, connected to the charger can be connected. This circuit differs from Figure
load, above the battery voltage and the LTC4412HV will 1 in the way the SENSE pin is connected. The SENSE pin
turn the MOSFET off. The STAT pin will then sink current is connected directly to the auxiliary power input and not
indicating an auxiliary input is connected. The battery is the load. This change forces the LTC4412HV’s control
now supplying no load current and all the load current circuitry to operate in an open-loop comparator mode.
flows through the Schottky diode. A silicon diode could be While the battery supplies the system, the GATE pin
used instead of the Schottky, but will result in higher voltage will be forced to its lowest clamped potential,
power dissipation and heating due to the higher forward instead of being regulated to maintain a 20mV drop across
voltage drop. 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
AUXILIARY
P-CHANNEL possible disadvantage is if the auxiliary input ramps up
MOSFET slow enough the load voltage will initially droop before
*
WALL
ADAPTER
INPUT WALL
ADAPTER
PRIMARY INPUT
P-CHANNEL P-CHANNEL
BATTERY
MOSFET MOSFET
CHARGER
* *

TO LOAD TO LOAD
BATTERY BATTERY
COUT CELL(S) COUT
CELL(S) LTC4412HV
LTC4412HV 1 6 VCC
1 6
VIN SENSE VIN SENSE
2 5 2 5
GND GATE 470k STATUS OUTPUT GND GATE 470k STATUS OUTPUT
3 4 DROPS WHEN A 3 4 IS LOW WHEN A
CTL STAT CTL STAT
4412HV F02 WALL ADAPTER 4412HV F03 WALL ADAPTER
IS PRESENT *DRAIN-SOURCE DIODE OF MOSFET IS PRESENT
*DRAIN-SOURCE DIODE OF MOSFET

Figure 2. Automatic Switchover of Load Between a Battery and a Figure 3. Automatic Switchover of Load Between
Wall Adapter with Auxiliary P-Channel MOSFET for Lowest Loss a Battery and a Wall Adapter in Comparator Mode

sn4412hv 4412hvfs

9
LTC4412HV
U
TYPICAL APPLICATIO S
rising. This is due to the SENSE pin voltage rising above auxiliary stays connected. When the primary power is
the battery voltage and turning off the MOSFET before the disconnected and VIN falls below VLOAD, it will turn on the
Schottky diode turns on. The factors that determine the auxiliary MOSFET if CTL is low, but VLOAD must stay up
magnitude of the voltage droop are the auxiliary input rise long enough for the MOSFET to turn on. At a minimum,
time, the type of diode used, the value of COUT and the load COUT capacitance must be sized to hold up VLOAD until the
current. transistion between the sets of MOSFETs is complete.
Sufficient capacitance on the load and low or no capaci-
Ideal Diode Control with a Microcontroller tance on VIN will help ensure this. If desired, this can be
Figure 4 illustrates an application circuit for microcontrol- avoided by use of a capacitor on VIN to ensure that VIN
ler monitoring and control of two power sources. The falls more slowly than VLOAD.
microcontroller’s analog inputs, perhaps with the aid of a
Load Sharing
resistor voltage divider, monitors each supply input and
commands the LTC4412HV through the CTL input. Back- Figure 5 illustrates an application circuit for dual battery
to-back MOSFETs are used so that the drain-source diode load sharing with automatic switchover of load from
will not power the load when the MOSFET is turned off (dual batteries to wall adapter. Whichever battery can supply the
MOSFETs in one package are commercially available). higher voltage will provide the load current until it is
discharged to the voltage of the other battery. The load will
With a logical low input on the CTL pin, the primary input
then be shared between the two batteries according to the
supplies power to the load regardless of the auxiliary
capacity of each battery. The higher capacity battery will
voltage. When CTL is switched high, the auxiliary input
provide proportionally higher current to the load. When a
will power the load whether or not it is higher or lower
wall adapter input is applied, both MOSFETs will turn off
than the primary power voltage. Once the auxiliary is on,
and no load current will be drawn from the batteries. The
the primary power can be removed and the auxiliary will
STAT pins provide information as to which input is supply-
continue to power the load. Only when the primary
ing the load current. This concept can be expanded to
voltage is higher than the auxiliary voltage will taking CTL
more power inputs.
low switch back to the primary power, otherwise the
WALL
ADAPTER
INPUT *
AUXILIARY
TO LOAD
P-CHANNEL MOSFETS
BAT1 COUT
* * LTC4412HV
AUXILIARY POWER 1 6 VCC
VIN SENSE
SOURCE INPUT 2 5
470k GND GATE 470k STATUS IS HIGH
3 4 WHEN BAT1 IS
CTL STAT
SUPPLYING
MICROCONTROLLER PRIMARY LOAD CURRENT
P-CHANNEL MOSFETS
WHEN BOTH STATUS LINES ARE
* *
HIGH, THEN BOTH BATTERIES ARE
TO LOAD * SUPPLYING LOAD CURRENTS. WHEN
0.1µF COUT BOTH STATUS LINES ARE LOW THEN
WALL ADAPTER IS PRESENT
BAT2
PRIMARY LTC4412HV LTC4412HV
1 6 1 6 VCC
POWER VIN SENSE VIN SENSE
SOURCE INPUT 2 5 2 5
GND GATE GND GATE 470k STATUS IS HIGH
3 4 3 4 WHEN BAT2 IS
CTL STAT CTL STAT
4412HV F04 4412HV F05 SUPPLYING
*DRAIN-SOURCE DIODE OF MOSFET *DRAIN-SOURCE DIODE OF MOSFET LOAD CURRENT

Figure 4. Microcontroller Monitoring and Control Figure 5. Dual Battery Load Sharing with Automatic
of Two Power Sources Switchover of Load from Batteries to Wall Adapter
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10
 LTC4412HV
U
TYPICAL APPLICATIO S
Multiple Battery Charging High Side Power Switch
Figure 6 illustrates an application circuit for automatic Figure 7 illustrates an application circuit for a logic con-
dual battery charging from a single charger. Whichever trolled high side power switch. When the CTL pin is a
battery has the lower voltage will receive the charging logical low, the LTC4412HV will turn on the MOSFET.
current until both battery voltages are equal, then both will Because the SENSE pin is grounded, the LTC4412HV will
be charged. When both are charged simultaneously, the apply maximum clamped gate drive voltage to the MOSFET.
higher capacity battery will get proportionally higher cur- When the CTL pin is a logical high, the LTC4412HV will
rent from the charger. For Li-Ion batteries, both batteries turn off the MOSFET by pulling its gate voltage up to the
will achieve the float voltage minus the forward regulation supply input voltage and thus deny power to the load. The
voltage of 20mV. This concept can apply to more than two MOSFET is connected with its source connected to the
batteries. The STAT pins provide information as to which power source. This disables the drain-source diode from
batteries are being charged. For intelligent control, the supplying voltage to the load when the MOSFET is off. Note
CTL pin input can be used with a microcontroller and that if the load is powered from another source, then the
back-to-back MOSFETs as shown in Figure 4. This allows drain-source diode can forward bias and deliver current to
complete control for disconnection of the charger from the power supply connected to the VIN pin.
either battery.
P-CHANNEL
MOSFET
* *
BATTERY TO LOAD OR
SUPPLY
CHARGER PowerPath TO LOAD
INPUT
INPUT BAT1 CONTROLLER COUT
LTC4412HV LTC4412HV
1 6 VCC 1 6
VIN SENSE 0.1µF VIN SENSE
2 5 2 5
GND GATE 470k GND GATE
3 4 STATUS IS HIGH 3 4
LOGIC
CTL STAT WHEN BAT1 IS CTL STAT
INPUT 4412HV F07
CHARGING
0.1µF *DRAIN-SOURCE DIODE OF MOSFET
*
TO LOAD OR
PowerPath
Figure 7. Logic Controlled High Side Power Switch
BAT2 CONTROLLER
LTC4412HV
1 6 VCC
VIN SENSE
2 5
GND GATE 470k
3 4 STATUS IS HIGH
CTL STAT WHEN BAT2 IS
4412HV F06
CHARGING
*DRAIN-SOURCE DIODE OF MOSFET

Figure 6. Automatic Dual Battery Charging

from Single Charging Source

sn4412hv 4412hvfs

11
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 of its circuits as described herein will not infringe on existing patent rights.
LTC4412HV
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)

0.62 0.95 2.90 BSC

MAX REF (NOTE 4)

1.22 REF

2.80 BSC 1.50 – 1.75

3.85 MAX 2.62 REF 1.4 MIN (NOTE 4)

PIN ONE ID

RECOMMENDED SOLDER PAD LAYOUT 0.30 – 0.45

0.95 BSC
PER IPC CALCULATOR 6 PLCS (NOTE 3)

0.80 – 0.90

0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’

0.30 – 0.50 REF

0.09 – 0.20 1.90 BSC
(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

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and USB Power, 4mm × 4mm QFN
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Operation of USB Component Peripheral Devices
LTC4411 SOT-23 Ideal Diode 2.6A Forward Current, 28mV Regulated Forward Voltage
sn4412hv 4412hvfs

LT/TP 0304 1K • PRINTED IN USA

12 Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ●
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