Datasheet

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LTC4412

4412fa

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

Low Loss PowerPath

Controller in ThinSOT

■

Very Low Loss Replacement for Power Supply

OR’ing Diodes

■

Minimal External Components

■

Automatic Switching Between DC Sources

■

Simplifies Load Sharing with Multiple Batteries

■

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

■

Cellular Phones

■

Notebook and Handheld Computers

■

Digital Cameras

■

USB-Powered Peripherals

■

Uninterruptable Power Supplies

■

Logic Controlled Power Switch

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 mul-

tiple power sources for extended battery life and low self-

heating. When conducting, the voltage drop across the

MOSFET is typically 20mV. For applications with a wall

adapter or other auxiliary power source, the load is auto-

matically 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.

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.

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

microcontroller that an auxiliary supply is connected.

The

control (CTL) input enables the user to force the primary

MOSFET off and the STAT pin low.

The LTC4412 is available in a low profile (1mm) ThinSOT

package.

PowerPath and ThinSOT are trademarks of Linear Technology Corporation.

GND

CTL

SENSE

GATE

STAT

LTC4412

OUT

TO LOAD

STATUS OUTPUT

LOW WHEN WALL

ADAPTER PRESENT

470k

4412 F01

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

CURRENT (A)

CONSTANT

4412 F01b

0.5

CONSTANT

VOLTAGE

SCHOTTKY

DIODE

LTC4412

LTC4412 vs Schottky Diode

Forward Voltage Drop

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

Summary of content (12 pages)

PAGE 1
LTC4412 Low Loss PowerPathTM Controller in ThinSOT U FEATURES DESCRIPTIO ■ 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 selfheating. When conducting, the voltage drop across the MOSFET is typically 20mV.
PAGE 2
LTC4412 U U U W W W (Note 1) U ABSOLUTE MAXIMUM RATINGS PI CO FIGURATIO Supply Voltage (VIN) .................................. –14V to 36V Voltage from VIN to SENSE ........................ – 28V to 28V Input Voltage CTL ........................................................– 0.3V to 36V SENSE .................................................... –14V to 36V Output Voltage GATE ..................... –0.3V to the Higher of VIN + 0.3V or SENSE + 0.3V STAT ...........................................
PAGE 3
LTC4412 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 TYP MAX IQCL Quiescent Supply Current at Low Supply with CTL Active VIN = 3.
PAGE 4
LTC4412 U W TYPICAL PERFOR A CE CHARACTERISTICS VFR vs Temperature and Supply Voltage Normalized Quiescent Supply Current vs Temperature VRTO vs Temperature and Supply Voltage 22 1.05 22 VIN = 28V 20 CURRENT (μA) VRTO (mV) VFR (mV) VIN = 2.5V VIN = 28V 20 VIN = 2.5V 18 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 18 –50 –25 125 50 25 75 0 TEMPERATURE (°C) 4412 G01 100 3.6V ≤ VIN ≤ 28V 1.0 0.95 –50 –25 125 7.1 0.25 8V ≤ VIN ≤ 28V IGATE = 1μA VOLTAGE (V) VOLTAGE (V) 0.
PAGE 5
LTC4412 U U U PI FU CTIO S 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 supplied 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.
PAGE 6
LTC4412 U OPERATIO 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).
PAGE 7
LTC4412 U W U U APPLICATIO S I FOR ATIO Introduction The system designer will find the LTC4412 useful in a variety of cost and space sensitive power control applications 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.
PAGE 8
LTC4412 U W U U APPLICATIO S I FOR ATIO 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 VIN.
PAGE 9
LTC4412 U TYPICAL APPLICATIO S Automatic PowerPath Control The applications shown in Figures 1, 2 and 3 are automatic 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.
PAGE 10
LTC4412 U TYPICAL APPLICATIO S 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 microcontroller monitoring and control of two power sources.
PAGE 11
LTC4412 U TYPICAL APPLICATIO S Multiple Battery Charging High Side Power Switch Figure 6 illustrates an application circuit for automatic dual battery charging from a single charger. Whichever battery has the lower voltage will receive the charging 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.
PAGE 12
LTC4412 U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 2.80 BSC 1.4 MIN 3.85 MAX 2.62 REF 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 1.90 BSC 0.09 – 0.20 (NOTE 3) S6 TSOT-23 0302 REV B NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.