LINEAR TECHNOLOGY LTC4413 Technical data

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Dual Monolithic Ideal Diode Manages Multiple Power Inputs

Design Note 356

Andy Bishop

Introduction

The LTC®4413 dual monolithic ideal diode helps reduce
the size and improve the performance and reliability of
handheld battery-operated devices. The LTC4413 is a
single-chip solution that can automatically select between
and isolate up to three power sources; such as a wall
adapter, an auxiliary supply and a battery. It provides a low
loss automatic PowerPath

TM

management solution for
demanding applications that may require short-circuit
protection, thermal management and system-level power
management and control.

The LTC4413 contains two isolated low voltage (2.5V to

5.5V) monolithic ideal diodes. Each ideal diode channel
provides a low forward voltage drop (typically as low as
40mV when conducting low current) and a low R

DS(ON)

(below 100mΩ) when conducting high current—fea­tures that are important to extend battery life and reduce
heat in portable applications. Furthermore, each channel
is capable of providing up to 2.6A of continuous current
from a small 3mm × 3mm, 10-pin DFN package. Current­limit and thermal shutdown features further enhance
system reliability.

Triple Supply Power Management

Figure 1 shows a schematic with the LTC4413 configured
to automatically switchover from a battery to either a USB
supply or to a wall adapter. This circuit provides uninter­rupted power to the load—while isolating all three power
sources—allowing the user to remove the battery without
affecting load voltage when either of the two other sup­plies is present. This circuit exploits the LTC4413 to
provide low loss uninterrupted power while automatically
prioritizing which source should be connected to the load.

Referring to Figure 1, if a wall adapter is applied in the
absence of a USB supply, the body diode in MP1 forward
biases, pulling the output voltage above the battery volt­age and turning off the ideal diode connected between INA
and OUTA. This causes the STAT voltage to fall, turning on
MP1. The load then draws current from the wall adapter
and the battery is disconnected from the load. If the USB
is present when the wall adapter is removed, the output
voltage falls until the USB voltage exceeds the output

, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.

02/05/356

(MP1 BODY DIODE)

WALL

ADAPTER

LTC4413

Actual

Size

USB

C1

10µF
R1
1Ω

BATTERY

R2
1000k

R3
100k

R4
1000k

R5
500k

ENBB

STAT

LTC4413

IDEAL

INA

OUTA

GND

IDEAL

INB OUTB

ENBA

MP1: FDR8508

MP1

R

STAT

470k

C2

4.7µF

DN356 F01

TO
LOAD

Figure 1. Automatic Switchover from a Battery to a USB Supply or Wall Adapter

voltage causing the STAT voltage to rise, disabling the
external PFET; the USB then provides power to the load.
In the absence of a USB supply when the wall adapter is
removed, the load voltage droops until the battery voltage
exceeds the load voltage, likewise causing the STAT
voltage to rise and disabling MP1; the battery then pro­vides the load power.

When a USB supply is applied, the voltage divider at ENBA
disables the power path from battery to OUT. The USB
then provides load current, unless a wall adapter is
present as described above.

Automatic Switchover Between a Battery and a
Wall Adapter with a Battery Charger

Figure 2 illustrates an application where the LTC4413
performs the function of automatically switching a load
over from a battery to a wall adapter, while controlling an
LTC4059A battery charger. When no wall adapter is
present, the LTC4413 connects the load to the Li-Ion
battery. In this configuration, the STAT voltage is high,
thereby disabling the battery charger. If a wall adapter is

connected, the load voltage rises as the ideal diode from
INB to OUTB conducts. As soon as the load voltage
exceeds the battery voltage, the battery is disconnected
from the load and the STAT voltage falls, turning on the
LTC4059A battery charger and beginning a charge cycle.

When the wall adapter is removed, the load voltage
collapses until it is below the battery voltage. The battery
reverts to supplying power to the load and the STAT pin
falls disabling the battery charger.

Conclusion

The LTC4413 performs automatic PowerPath manage­ment functions in high performance battery-powered
applications. The applications described herein have the
added benefit that while an alternate supply powers the
load, the battery may be replaced without disturbing load
voltage. This feature demonstrates the benefit of the
LTC4413 as compared with alternative solutions that do
not allow the battery to be replaced without impacting load
power.

LTC4413

WALL

ADAPTER

LTC4059A

V

CC

ENB

PROG

GND

BAT

R2
100k

1-CELL
Li-Ion

C1
10µF

STAT

IDEAL

INA OUTA

ENBA

ENBB

GND

IDEAL

INB OUTB

R1
560k

C2

4.7µF

DN356 F02

TO LOAD

Figure 2. Automatic Switchover from a Battery to a Wall Adapter with a Battery Charger

Data Sheet Download

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