LTC4412IS6#TRPBF [Linear]
LTC4412 - Low Loss PowerPath Controller in ThinSOT; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C;
| 型号： | LTC4412IS6#TRPBF |
| 厂家： | 
Linear |
| 描述： | LTC4412 - Low Loss PowerPath Controller in ThinSOT; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C 光电二极管 |
| 文件： | 总14页 (文件大小：392K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4412
Low Loss PowerPath™
Controller in ThinSOT
FeaTures
DescripTion
The LTC®4412 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 LTC4412s
may be interconnected to allow load sharing between
multiple batteries or charging of multiple batteries from
a single charger.
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Very Low Loss Replacement for Power Supply
OR’ing Diodes
Minimal External Components
Automatic Switching Between DC Sources
Simplifies Load Sharing with Multiple Batteries
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Low Quiescent Current: 11µA
3V to 28V AC/DC Adapter Voltage Range
2.5V to 28V 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) ThinSOT™ Package
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The wide supply operating range supports operation
from one to six 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.
applicaTions
n
Cellular Phones
Notebook and Handheld Computers
Digital Cameras
USB-Powered Peripherals
Uninterruptible Power Supplies
Logic Controlled Power Switch
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 mi-
crocontroller that an auxiliary supply is connected. The
control (CTL) input enables the user to force the primary
MOSFET off and the STAT pin low.
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L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
The LTC4412 is available in a low profile (1mm) ThinSOT
package.
Typical applicaTion
LTC4412 vs Schottky Diode
Forward Voltage Drop
1
WALL
ADAPTER
INPUT
CONSTANT
R
ON
TO LOAD
BATTERY
CELL(S)
C
OUT
LTC4412
SENSE
LTC4412
V
CC
V
IN
GND GATE
CTL STAT
470k
CONSTANT
VOLTAGE
STATUS OUTPUT
LOW WHEN WALL
ADAPTER PRESENT
SCHOTTKY
DIODE
4412 F01
0
Figure 1. Automatic Switchover of Load Between a Battery and a Wall Adapter
0.02
0.5
4412 F01b
FORWARD VOLTAGE (V)
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LTC4412
absoluTe MaxiMuM raTings
pin conFiguraTion
(Note 1)
Supply Voltage (V ) .................................. –14V to 36V
IN
Voltage from V to SENSE ........................ –28V to 28V
IN
TOP VIEW
Input Voltage
V
IN
1
6 SENSE
5 GATE
4 STAT
CTL........................................................–0.3V to 36V
SENSE .................................................... –14V to 36V
Output Voltage
GND 2
CTL 3
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
GATE ..................... –0.3V to the Higher of V + 0.3V
IN
or SENSE + 0.3V
T
JMAX
= 150°C, θ = 230°C/W
JA
STAT ......................................................–0.3V to 36V
Operating Junction Temperature Range
(Note 2) ........................................... –55°C to 150°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
orDer inForMaTion
LEAD FREE FINISH
LTC4412ES6#PBF
LTC4412IS6#PBF
LTC4412HS6#PBF
LTC4412MPS6#PBF
LEAD BASED FINISH
LTC4412ES6
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
PACKAGE DESCRIPTION
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
TEMPERATURE RANGE
LTC4412ES6#TRPBF
LTC4412IS6#TRPBF
LTC4412HS6#TRPBF
LTC4412MPS6#TRPBF
TAPE AND REEL
LTA2
–40°C to 85°C
LTA2
–40°C to 85°C
LTA2
–40°C to 150°C
–55°C to 150°C
TEMPERATURE RANGE
–40°C to 85°C
LTA2
PART MARKING*
LTC4412ES6#TR
LTA2
LTA2
LTA2
LTA2
LTC4412IS6
LTC4412IS6#TR
–40°C to 85°C
LTC4412HS6
LTC4412HS6#TR
LTC4412MPS6#TR
–40°C to 150°C
–55°C to 150°C
LTC4412MPS6
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LTC4412
elecTrical characTerisTics 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.
SYMBOL
V ,
PARAMETER
CONDITIONS
and/or V Must Be in This Range
SENSE
MIN
TYP
MAX
UNITS
l
l
Operating Supply Range
V
2.5
28
V
IN
IN
V
for Proper Operation
SENSE
I
Quiescent Supply Current at Low Supply
While in Forward Regulation
V
= 3.6V. Measure Combined Current
11
15
19
26
µA
µA
QFL
IN
at V and SENSE Pins Averaged with
IN
V
SENSE
= 3.5V and V
= 3.6V (Note 3)
SENSE
l
I
Quiescent Supply Current at High Supply
While in Forward Regulation
V
= 28V. Measure Combined Current
IN
QFH
at V and SENSE Pins Averaged with
IN
V
SENSE
= 27.9V and V
= 28V (Note 3)
SENSE
I
I
I
I
I
Quiescent Supply Current at Low Supply
While in Reverse Turn-Off
V
= 3.6V, V = 3.7V. Measure
SENSE
10
16
7
19
28
13
20
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
IN
= 27.9V, V
= 28V. Measure
SENSE
Combined Current of V and SENSE Pins
IN
Quiescent Supply Current at Low Supply
with CTL Active
V
= 3.6V, V
= 0V, V = 1V
CTL
IN
IN
SENSE
SENSE
Quiescent Supply Current at High Supply
with CTL Active
V
= 28V, V
= 0V, V = 1V
12
0
CTL
V
and SENSE Pin Leakage Currents
V
IN
V
IN
= 28V, V
= 14V, V
= 0V; V
= 28V, V = 0V
SENSE IN
–3
IN
SENSE
SENSE
SENSE
IN
When Other Pin Supplies Power
= –14V; V
= 14V, V = –14V
PowerPath Controller
l
l
V
V
PowerPath Switch Forward Regulation
Voltage
V
V
– V
, 2.5V ≤ V ≤ 28V
10
10
20
20
32
32
mV
mV
FR
IN
SENSE
IN
PowerPath Switch Reverse Turn-Off
Threshold Voltage
– V , 2.5V ≤ V ≤ 28V
IN IN
RTO
SENSE
GATE and STAT Outputs
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
GATE Clamp Voltage
Apply I
SENSE
= 1µA, V = 12V,
6.3
7
7.7
V
G(ON)
GATE
IN
V
= 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
l
l
2.5V ≤ V ≤ 28V (Note 7)
–1
6
IN
STAT Sink Current
STAT Turn-On Time
STAT Turn-Off Time
2.5V ≤ V ≤ 28V (Note 7)
10
4.5
40
17
25
75
IN
(Note 8)
(Note 8)
CTL Input
l
l
V
V
CTL Input Low Voltage
CTL Input High Voltage
CTL Input Pull-Down Current
CTL Hysteresis
2.5V ≤ V ≤ 28V
0.5
0.635
3.5
0.35
5.5
V
V
IL
IH
IN
2.5V ≤ V ≤ 28V
0.9
1
IN
I
0.35V ≤ V ≤ 28V
µA
mV
CTL
CTL
H
2.5V ≤ V ≤ 28V
135
CTL
IN
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LTC4412
elecTrical characTerisTics
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 3: This results in the same supply current as would be observed with
an external P-channel MOSFET connected to the LTC4412 and operating in
forward regulation.
Note 4: V is held at 12V and GATE is forced to 10.5V. SENSE is set at
IN
Note 2: The LTC4412 is tested under pulsed load conditions such that T ≈
T . The LTC4412E is guaranteed to meet performance specifications from
A
12V to measure the source current at GATE. SENSE is set at 11.9V to
measure sink current at GATE.
J
0°C to 85°C operating junction temperature range. Specifications over
the –40°C to 85°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LTC4412I is guaranteed over the –40°C to 85°C operating junction
temperature range. The LTC4412MP is tested and guaranteed over the
–55°C to 150°C operating junction temperature range. High junction
temperatures degrade operating lifetimes; operating lifetime is degraded
for junction temperatures greater than 125°C. Note that the maximum
ambient temperature consistent with these specifications is determined
by specific operating conditions in conjunction with board layout, the
Note 5: V is held at 12V and SENSE is stepped from 12.2V to 11.8V to
IN
trigger the event. GATE voltage is initially V
.
G(OFF)
Note 6: V is held at 12V and SENSE is stepped from 11.8V to 12.2V to
IN
trigger the event. GATE voltage is initially internally clamped at V
.
G(ON)
Note 7: STAT is forced to V – 1.5V. SENSE is set at V – 0.1V to
IN
IN
measure the off current at STAT. SENSE is set V + 0.1V to measure the
IN
sink current at STAT.
Note 8: STAT is forced to 9V and V is held at 12V. SENSE is stepped
IN
from 11.8V to 12.2V to measure the STAT turn-on time defined when I
STAT
reaches one half the measured I
11.8V to measure the STAT turn-off time defined when I
SENSE is stepped from 12.2V to
S(SNK).
rated package thermal impedance and other environmental factors. T
J
reaches one
STAT
is calculated from the ambient temperature T and power dissipation P
A
D
half the measured I
S(SNK) .
according to the following formula: T = T + (P • Θ ), where Θ =
J
A
D
JA
JA
230°C/W for the TSOT-23 package.
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LTC4412
Typical perForMance characTerisTics
Normalized Quiescent Supply
Current vs Temperature
VFR vs Temperature and
VRTO vs Temperature and
Supply Voltage
Supply Voltage
1.15
1.10
1.05
1.00
0.95
25
20
15
25
20
15
V
= 2.5V
IN
V
= 28V
IN
V
= 28V
IN
3.6V ≤ V ≤ 28V
IN
V
= 2.5V
IN
–75
–25
25
75
125
175
–75
–25
25
75
125
125
125
175
–75
–25
25
75
125
125
125
175
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4412 G03
4412 G01
4412 G02
ILEAK vs Temperature
VG(ON) vs Temperature
VG(OFF) vs Temperature and IGATE
–0.2
–0.25
–0.3
7.05
6.95
6.85
0.30
0.20
0.10
0.00
8V ≤ V ≤ 28V
2.5V ≤ V ≤ 28V
IN
= 1µA
IN
I
GATE
–0.35
I
I
I
= –10µA
GATE
GATE
GATE
= –5µA
= 0µA
–0.4
–75
–25
25
75
175
–75
–25
25
75
175
–75
–25
25
75
125
175
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4412 G04
4412 G05
4412 G06
tG(ON) vs Temperature
tG(OFF) vs Temperature
IS(SNK) vs Temperature and VIN
106
100
94
13.0
12.5
12.0
11.5
11.0
10.5
10.0
3.6V ≤ V ≤ 28V
3.6V ≤ V ≤ 28V
IN
V
= V – 1.5V
STAT IN
IN
C
= 1nF
C
= 1nF
GATE
GATE
V
= 28V
IN
V
= 2.5V
IN
–75
–25
25
75
175
–75
–25
25
75
175
–75
–25
25
75
125
175
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4412 G07
4412 G08
4412 G09
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LTC4412
pin FuncTions
V (Pin1):PrimaryInputSupplyVoltage. Suppliespower
STAT (Pin 4): Open-Drain Output Status Pin. When the
IN
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
suppliedpowerfromabatteryorotherpowersourcewhich
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.
SENSE pin is pulled above the V pin with an auxiliary
IN
power source by about 20mV or more, the reverse turn-
off threshold (V ) is reached. The STAT pin will then go
RTO
from an open state to a 10µA current sink (I
). The
S(SNK)
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
CTL (Pin 3): Digital Control Input. A logical high input
to maintain a forward regulation voltage (V ) of 20mV
FR
(V ) on this pin forces the gate to source voltage of the
IH
between the V and SENSE pins when an auxiliary power
IN
primaryP-channelMOSFETpowerswitchtoasmallvoltage
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.
(V
). This will turn the MOSFET off and no current will
GOFF
flow from the primary power input at V if the MOSFET
IN
is configured so that the drain to source diode does not
forward bias. A high input also forces the STAT pin to
SENSE (Pin 6): Power Sense Input Pin. Supplies power
to the internal circuitry and is a voltage sense input to the
internalanalogcontroller(Theotherinputtothecontroller
sink 10µA of current (I
). If the STAT pin is used to
S(SNK)
controlanauxiliaryP-channelpowerswitch,thenasecond
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.
is the V pin). This input is usually supplied power from
IN
an auxiliary source such as an AC adapter or back-up
battery which also supplies current to the load.
block DiagraM
+
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
4412 BD
*DRAIN-SOURCE DIODE OF MOSFET
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LTC4412
operaTion
OperationcanbestbeunderstoodbyreferringtotheBlock
Diagram, whichillustratestheinternalcircuitblocks 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
The Power Source Selector will power the LTC4412 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 V + 20mV (V ), the Analog
IN
RTO
Controller will instruct the Linear Gate Driver and Voltage
Clamp block to rapidly pull the GATE pin voltage to the
SENSE pin voltage. This action will quickly finish turning
off the external P-channel MOSFET if it hasn’t already
turned completely off. For a clean transition, the reverse
turn-off threshold has hysteresis to prevent uncertainty.
The system is now in the reverse turn-off mode. Power to
the load is being delivered through the external diode and
no current is drawn from the primary supply. The external
diode provides protection in case the auxiliary supply is
below the primary supply, sinks current to ground or is
connected reverse polarity. During the reverse turn-off
mode of operation the STAT pin will sink 10µA of current
voltage of 0.35V (V ). If only the primary supply is pres-
IL
ent, the Power Source Selector will power the LTC4412
from the V pin. Amplifier A1 will deliver a current to
IN
the Analog Controller block that is proportional to the
voltage difference in the V and SENSE pins. While the
IN
voltage on SENSE is lower than V – 20mV (V ), the
IN
FR
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 (I
voltage reaches ground or the gate clamp voltage. The
gate clamp voltage is 7V (V ) below the higher of V
) stops when the GATE
G(SNK)
G(ON)
IN
or V
. As the SENSE voltage pulls up to V – 20mV,
(I
) if connected. Note that the external MOSFET is
SENSE
IN
S(SNK)
the LTC4412 will regulate the GATE voltage to maintain
wired so that the drain to source diode will momentarily
a 20mV difference between V and V
the V of the MOSFET. The system is now in the forward
which is also
forward bias when power is first applied to V and will
IN
SENSE
IN
becomereversebiasedwhenanauxiliarysupplyisapplied.
DS
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
WhentheCTL(control)inputisassertedhigh, theexternal
MOSFET will have its gate to source voltage forced to a
small voltage V
and the STAT pin will sink 10µA of
G(OFF)
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
to deliver the current with a 20mV V the GATE voltage
DS
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.
(I ) on the CTL pin will insure a low level input if the pin
CTL
When an auxiliary supply is applied, the SENSE pin will be
should become open.
pulled higher than the V pin through the external diode.
IN
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LTC4412
applicaTions inForMaTion
Introduction
If a forward voltage drop of more than 20mV is accept-
able then a smaller MOSFET can be used, but must be
sized compatible with the higher power dissipation. Care
should be taken to ensure that the power dissipated is
never allowed to rise above the manufacturer’s recom-
mended maximum level. The auxiliary MOSFET power
The system designer will find the LTC4412 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.
switch, if used, has similar considerations, but its V
GS
can be tailored by resistor selection. When choosing the
resistor value consider the full range of STAT pin current
(I
S(SNK)
) that may flow through it.
External P-Channel MOSFET Transistor Selection
V and SENSE Pin Bypass Capacitors
IN
Important parameters for the selection of MOSFETs are
Many types of capacitors, ranging from 0.1µF to 10µF and
located close to the LTC4412, will provide adequate V
bypassing if needed. Voltage droop can occur at the load
duringasupplyswitchoverbecausesometimeisrequired
toturnontheMOSFETpowerswitch.Factorsthatdetermine
the magnitude of the voltage droop include the supply rise
and fall times, the MOSFET’s characteristics, the value of
the maximum drain-source voltage V
threshold
DS(MAX),
IN
voltage V
and on-resistance R
.
GS(VT)
DS(ON)
The maximum allowable drain-source voltage, V
DS(MAX),
must be high enough to withstand the maximum drain-
source voltage seen in the application.
ThemaximumgatedrivevoltagefortheprimaryMOSFETis
C
andtheloadcurrent.Droopcanbemadeinsignificant
OUT
set by the smaller of the V supply voltage or the internal
IN
by the proper choice of C , since the droop is inversely
OUT
clampingvoltageV
AlogiclevelMOSFETiscommonly
G(ON).
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.
used, but if a low supply voltage limits the gate voltage, a
sub-logic level threshold MOSFET should be considered.
ThemaximumgatedrivevoltagefortheauxiliaryMOSFET,
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
powersource.To reducetheQandpreventthesetransients
fromexceedingtheLTC4412’sabsolutemaximumvoltage
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
R
to obtain the desired V while operating at full
DS(ON)
DS
load current and an achievable V . The MOSFET nor-
GS
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 V may
DS
result. However, the drain-source diode of the MOSFET,
if forward biased, will limit V . A large V , combined
DS
DS
with the load current, will likely result in excessively high
MOSFETpowerdissipation.KeepinmindthattheLTC4412
will regulate the forward voltage drop across the primary
The selected capacitance value and capacitor’s ESR can
MOSFET at 20mV if R
DS(ON)
is low enough. The required
be verified by observing V and SENSE for acceptable
DS(ON)
IN
R
can be calculated by dividing 0.02V by the load
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.
currentinamps.Achievingforwardregulationwillminimize
power loss and heat dissipation, but it is not a necessity.
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8
For more information www.linear.com/LTC4412
LTC4412
applicaTions inForMaTion
V and SENSE Pin Usage
IN
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 V and SENSE pin connections should be made in a
IN
way to avoid unwanted I • R drops in the power path. Both
Control Pin Usage
pins are protected from negative voltages.
Thisisadigitalcontrolinputpinwithlowthresholdvoltages
GATE Pin Usage
(V V ) for use with logic powered from as little as 1V.
IL, IH
During normal operation, the CTL pin can be biased at any
voltage between ground and 28V, regardless of the supply
voltage to the LTC4412. A logical high input on this pin
forces the gate to source voltage of the primary P-channel
The GATE pin controls the external P-channel MOSFET
connected between the V and SENSE pins when the
IN
load current is supplied by the power source at V . In
IN
this mode of operation, the internal current source, which
MOSFET power switch to a small voltage (V
). This
GOFF
is responsible for pulling the GATE pin up, is limited to
will turn the MOSFET off and no current will flow from the
a few microamps (I
). If external opposing leakage
G(SRC)
primary power input at V if the MOSFET is configured
IN
currents exceed this, the GATE pin voltage will reach the
clamp voltage (V ) and V will be smaller. The internal
so that the drain to source diode is not forward biased.
GON
DS
The high input also forces the STAT pin to sink 10µA of
current sink, which is responsible for pulling the GATE pin
down, has a higher current capability (I ). With an
current (I
). See the Typical Applications for various
S(SNK)
G(SNK)
examples on using the STAT pin. A 3.5µA internal pull-
auxiliary supply input pulling up on the SENSE pin and
exceeding the V pin voltage by 20mV (V ), the device
down current (I ) on the CTL pin will insure a logical
low level input if the pin should be open.
CTL
IN
RTO
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 (V
).
GOFF
Most of the application circuits shown provide some
protection against supply faults such as shorted, low or
reversedsupplyinputs.Thefaultprotectiondoesnotprotect
shortedsuppliesbutcanisolateothersuppliesandtheload
from faults. A necessary condition of this protection is for
all components to have sufficient breakdown voltages. In
somecases,ifprotectionoftheauxiliaryinput(sometimes
referred to as the wall adapter input) is not required, then
the series diode or MOSFET may be eliminated.
While in forward regulation, if the on resistance of the
MOSFET is too high to maintain forward regulation, the
GATE pin will maximize the MOSFET’s V to that of the
GS
clamp voltage (V ). The clamping action takes place
GON
between the higher of V or V
and the GATE pin.
IN
SENSE
Status Pin Usage
During normal operation, the open-drain STAT pin can be
biased at any voltage between ground and 28V regard-
less of the supply voltage to the LTC4412. It is usually
connected to a resistor whose other end connects to a
voltage source. In the forward regulation mode, the STAT
Internal protection for the LTC4412 is provided to prevent
damaging pin currents and excessive internal self heating
during a fault condition. These fault conditions can be
a result of any LTC4412 pins shorted to ground or to a
power source that is within the pin’s absolute maximum
pin will be open (I ). When a wall adaptor input or
S(OFF)
other auxiliary supply is connected to that input, and the
voltage on SENSE is higher than V + 20mV (V ), the
voltage limits. Both the V and SENSE pins are capable
IN
IN
RTO
of being taken significantly below ground without current
drain ordamage to the IC (see AbsoluteMaximum Voltage
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.
systemisinthereverseturn-offmode.Duringthismodeof
operation the STAT pin will sink 10µA of current (I ).
S(SNK)
This will result in a voltage change across the resistor,
depending on the resistance, which is useful to turn on an
auxiliaryP-channelMOSFETorsignaltoamicrocontroller
that an auxiliary power source is connected. External
4412fb
9
For more information www.linear.com/LTC4412
LTC4412
Typical applicaTions
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
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 LTC4412 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 LTC4412 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.
MOSFET followed by turning on of the auxiliary MOSFE
T.
OncetheauxiliaryMOSFEThasturnedonthevoltagedrop
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 LTC4412’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, instead of being
regulated to maintain a 20mV drop across the MOSFET.
This has the advantages of minimizing power loss in the
MOSFETbyminimizingitsR andnothavingtheinfluence
ON
ofalinearcontrolloop’sdynamics.Apossibledisadvantage
is if the auxiliary input ramps up slow enough the load
voltage will initially droop before rising. This is due to the
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
C
OUT
OUT
LTC4412
LTC4412
1
2
3
6
5
4
1
2
3
6
5
4
V
CC
V
SENSE
V
SENSE
IN
IN
GND GATE
CTL STAT
470k
GND GATE
CTL STAT
470k
STATUS OUTPUT
DROPS WHEN A
WALL ADAPTER
IS PRESENT
STATUS OUTPUT
IS LOW WHEN A
WALL ADAPTER
IS PRESENT
4412 F02
4412 F03
*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
4412fb
10
For more information www.linear.com/LTC4412
LTC4412
Typical applicaTions
SENSE pin voltage rising above the battery voltage and
turning off the MOSFET before the Schottky diode turns
on.Thefactorsthatdeterminethemagnitudeofthevoltage
droop are the auxiliary input rise time, the type of diode
the auxiliary stays connected. When the primary power
is disconnected and V falls below V
, it will turn
IN
LOAD
on the auxiliary MOSFET if CTL is low, but V
must
LOAD
stay up long enough for the MOSFET to turn on. At a
minimum, C capacitance must be sized to hold up
used, the value of C
and the load current.
OUT
OUT
V
LOAD
until the transition between the sets of MOSFETs
Ideal Diode Control with a Microcontroller
is complete. Sufficient capacitance on the load and low
or no capacitance on V will help ensure this. If desired,
IN
Figure 4 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller’sanaloginputs, perhapswiththeaidofa
resistor voltage divider, monitors each supply input and
commandstheLTC4412throughtheCTLinput. Back-to-
backMOSFETsareusedsothatthedrain-sourcediodewill
not power the load when the MOSFET is turned off (dual
MOSFETs in one package are commercially available).
this can be avoided by use of a capacitor on V to ensure
IN
that V falls more slowly than V
.
IN
LOAD
Load Sharing
Figure 5 illustrates an application circuit for dual battery
load sharing with automatic switchover of load from
batteries to wall adapter. Whichever battery can supply
the 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 STAT pins provide information as to which input is
supplying 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
voltage is higher than the auxiliary voltage will taking
CTL low switch back to the primary power, otherwise
WALL
ADAPTER
INPUT
*
AUXILIARY
P-CHANNEL MOSFETS
TO LOAD
BAT1
*
*
C
OUT
LTC4412
SENSE
AUXILIARY POWER
SOURCE INPUT
1
2
3
6
5
4
V
CC
V
IN
470k
GND GATE
CTL STAT
470k
STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
MICROCONTROLLER
PRIMARY
LOAD CURRENT
P-CHANNEL MOSFETS
*
*
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
LTC4412
PRIMARY
POWER
SOURCE INPUT
1
2
3
6
5
4
LTC4412
1
2
3
6
5
4
V
V
SENSE
CC
IN
V
SENSE
IN
GND GATE
CTL STAT
GND GATE
CTL STAT
470k
STATUS IS HIGH
WHEN BAT2 IS
SUPPLYING
4412 F04
4412 F05
*DRAIN-SOURCE DIODE OF MOSFET
LOAD CURRENT
*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
4412fb
11
For more information www.linear.com/LTC4412
LTC4412
Typical applicaTions
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
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
currentfromthecharger.ForLi-Ionbatteries,bothbatteries
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-
trolledhighsidepowerswitch.WhentheCTLpinisalogical
low, the LTC4412 will turn on the MOSFET. Because the
SENSE pin is grounded, the LTC4412 will apply maximum
clamped gate drive voltage to the MOSFET. When the CTL
pin is a logical high, the LTC4412 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 con-
nectedwithitssourceconnectedtothepowersource.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 V pin.
IN
*
TO LOAD OR
PowerPath
BATTERY
CHARGER
INPUT
P-CHANNEL
MOSFET
*
CONTROLLER
BAT1
LTC4412
SENSE
SUPPLY
INPUT
1
2
3
6
5
4
V
TO LOAD
CC
V
IN
C
OUT
GND GATE
CTL STAT
470k
LTC4412
SENSE
STATUS IS HIGH
WHEN BAT1 IS
CHARGING
1
2
3
6
5
4
0.1µF
V
IN
GND GATE
CTL STAT
0.1µF
*
LOGIC
INPUT
TO LOAD OR
PowerPath
CONTROLLER
4412 F07
*DRAIN-SOURCE DIODE OF MOSFET
BAT2
LTC4412
1
2
3
6
5
4
V
CC
V
SENSE
IN
Figure 7. Logic Controlled High Side Power Switch
GND GATE
CTL STAT
470k
STATUS IS HIGH
WHEN BAT2 IS
CHARGING
4412 F06
*DRAIN-SOURCE DIODE OF MOSFET
Figure 6. Automatic Dual Battery Charging
from Single Charging Source
4412fb
12
For more information www.linear.com/LTC4412
LTC4412
revision hisTory (Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
02/15 Added H and MP-grade options.
Throughout
4412fb
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
13
LTC4412
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
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
(NOTE 4)
2.80 BSC
3.85 MAX 2.62 REF
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
Complete Dual Battery Charger/Selector System, 36-Lead SSOP
Adjustable Trip Voltage/Hysteresis, ThinSOT
LTC1960
LTC1998
LTC4350
Dual Battery Charger Selector with SPI
2.5µA, 1% Accurate Programmable Battery Detector
Hot Swappable Load Share Controller
Allows N + 1 Redundant Supply, Equally Loads Multiple Power Supplies
Connected in Parallel
LTC4410
USB Power Manager in ThinSOT
Enables Simultaneous Battery Charging and
Operation of USB Component Peripheral Devices
4412fb
LT 0215 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
14
●
●
LINEAR TECHNOLOGY CORPORATION 2002
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4412
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