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LTC4415IDHC#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LTC4415
13
4415fa
Typical applicaTions
Precision enable inputs and independent status outputs
provide flexibility in power supply back up and load share
applications using the two high current ideal diode circuits
in the LTC4415, as shown in the following examples. The
features shown in these application circuits can be com-
bined in custom applications as needed.
Prioritized Switchover to a Backup Battery
The application circuit, Figure 5, illustrates switchover
from a primary power source to backup power at a pre-
cise input voltage using the prioritized power supply-OR
application circuit. Diode 2 is enabled when the primary
power source voltage on diode 1 input falls below the
threshold given as follows:
V
IN1
<0.8V • 1+
R1+R2
R3
As V
IN1
falls further, diode 1 is disabled when the primary
power source voltage falls below the threshold determined
by the resistor divider on enable pin EN1:
V
IN1
< 0.8V – V
ENHYST
( )
• 1+
R1
R2+R3
The built-in hysteresis on the enable pins in the LTC4415
provides some overlap of diode enables around the swi-
tchover of power supplies. Resistor R2 can be optionally
used for additional overlap between the two supplies. The
additional overlap is given by:
V
OVERLAP
≈ V
ENTH
•
R2
R3
when
R2
R3
<<1
The enable overlap minimizes the load voltage droop during
switchover. Both input power supplies provide power to
the load during the overlap. The status output pins can be
pulled up to the output voltage or to a logic power supply.
Automatic Switchover to a Backup Battery and Keep-
Alive Power Source
Figure 6 illustrates an application circuit for automatic
switchover to the backup battery if the primary power
source voltage falls below the backup battery voltage. The
wired-AND of the status outputs is used to drive the gate
of a pair of back-to-back connected external NMOS (M1
and M2) when both primary and backup power sources
are absent or below UVLO or during thermal shutdown of
LTC4415. Under these conditions, the keep-alive source
supplies power to critical components of the system. At
the same time, the wired-AND status output turns off
Figure 5. Prioritized Power Supply ORing
Figure 6. Automatic Switchover to a Backup Battery with Provision
for Keep-Alive Power to the Load When Both Are Absent
IDEAL
IDEAL
LTC4415
GND
EN1
R1
47k
4415 F06
47µF
LOAD
DMN2215UDM
M1
M2
M3
OPTIONAL
KEEP ALIVE/
COIN CELL
CLIM1
CLIM2
STAT1
WARN1
WARN2
STAT2
EN2
IN2
BACKUP
BAT
IN1 OUT1
OUT2
PRIMARY
POWER
SOURCE
+
IDEAL
IDEAL
LTC4415
GND
EN1
4415 F05
4.7µF
TO
LOAD
R1
R2
R3
R
CLIM2
470k
R
CLIM1
CLIM1
CLIM2
STAT1
WARN1
WARN2
STAT2
EN2
IN2
IN1 OUT1
OUT2
PRIMARY
POWER
SOURCE
SECONDAY
POWER
SOURCE
(BAT)
+
470k
470k
470k
LTC4415
14
4415fa
Typical applicaTions
non-critical high current loads. If the status resistors are
pulled up through the keep-alive power source itself as
shown in Figure 6, the output voltage is limited to:
V
OUT
= V
KEEP_ALIVE
– V
gs(M1,2)
where V
gs(M1,2)
is the voltage drop from gate to source
of the composite NMOS device (M1 and M2). The pull-up
resistor, R1, consumes power from the keep-alive source
when the primary or backup sources supply power to the
load. The primary power source or backup battery supplies
power to the load when either of them are higher than the
output voltage.
Current limit on any of the diode power paths can be set
to automatically fold back as the output voltage drops (to
reduce power consumption), by switching out a resistor on
the CLIM pin, as shown in Figure 6 for diode 1. The gate
of NMOS M3 can optionally be fed from a resistor divided
output voltage to adjust the output voltage threshold of
current foldback.
Multiple Battery Charging
Figure 7 illustrates an application circuit for automatic dual
battery charging from a single charger. The battery with
lower voltage receives larger charging current until both
battery voltages are equal, then both are charged. While
both batteries are charging simultaneously, the higher
capacity battery gets proportionally higher current from
the charger. For Li-Ion batteries, both batteries achieve
the charger float voltage minus the forward regulation
voltage of 15mV. This concept can be extended to more
than two batteries using additional LTC4415. The STAT1,
STAT2 pins provide information as to when the batteries
are being charged. For intelligent control, the EN1/EN2
input pins can be used with a microcontroller as shown
in Figure 9 later in this section.
Figure 7. Dual Battery Charging from a Single Charger
PROG
EN
FAULT
BATSENS
TO µP
FROM µP
NTC
CHRG
PGND
10µF
PV
IN
V
INSENSE
BAT
IDET TIMER
R4
549Ω
R5
549Ω
C2
0.22µF
C1
10µF
V
IN
4.5V TO 5.5V
C3
0.1µF
SS
SW SENSE
LTC4001
L1
1.5µH
GNDSENS
R3
10k
25°C
R2
1k
D1
LED
R1
10k
IDEAL
50k
IDEAL
LTC4415
GND
EN1
4415 F07
CLIM1
CLIM2
STAT1
WARN1
WARN2
STAT2
EN2
IN2
IN1 OUT1
OUT2
BAT2
LOAD2
1.5k
1.5k
+
BAT1
+
LOAD1
LTC4415
15
4415fa
Typical applicaTions
Load Sharing by Multiple Batteries and Automatic
Switchover to a Preferred Power Supply
(Such as a Wall Adapter)
An application circuit for dual battery load sharing with
automatic switchover to a wall adapter (when present)
is shown in Figure 8. In the absence of the wall adapter,
the higher voltage battery provides the load current until
it has discharged to the voltage of the other battery. The
load is then shared between the two batteries according
to their capacities, the higher capacity battery providing
proportionally higher current to the load unless limited
by its current limit.
When a wall adapter is applied, the output voltage rises
as the body diode of PFET MP1 conducts and both of the
ideal diode paths in the LTC4415 stop conducting due to
reverse turn-off. At this time, the wired-OR status signal
pulls up the gate voltage of NFET MN1, pulling down the
gate voltage of power PFET MP1, turning it on. The wired-OR
status signal indicates whether the wall adapter or either
of the two batteries is supplying the load current. The two
application circuits described in Figure 7 and Figure 8 can
be cascaded for dual battery charging and load sharing.
Microcontrolled Power Switch with Reverse Blocking,
Selectable Current Limit, Soft-Start and Monitoring
Figure 9 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller monitors the input supply voltages and
commands the LTC4415 through EN1/EN2 inputs.
Currents through the ideal diodes are monitored by the
microcontroller measuring CLIM1/CLIM2 pin voltages
using ADCs. The current limit can be adjusted for either
diode using an external FET as shown in this application
for diode 1 with MN1. The two ideal diode outputs are
connected together for power source ORing, or they may
feed different loads.
Parallel Diodes for Lower Resistance or Higher
Current Output
The two ideal diodes in the LTC4415 can be connected in
parallel as shown in Figure 10 to achieve a low resistance
PowerPath. The master enable input, ENABLE, turns on
diode 2. EN1 is tied to the output so that diode 1 conducts
only after the output has charged up (by diode 2 according
to its current limit setting). Diode 1 is disabled when the
Figure 8. Dual Battery Load Sharing with Automatic Switchover to a Wall Adapter
IDEAL
IDEAL
LTC4415
GND
EN1
470k
MN1
IRLML2402
CLIM1
CLIM2
STAT1
STAT
WARN1
WARN2
STAT2
EN2
IN2
BAT2
BAT1
IN1 OUT1
OUT2
470k
4.7µF
+
MP1 IRFHS9301
WALL ADAPTER
PV
IN1
PV
IN2
SW2
SW3
FB2
FB3
V
OUT1
LTC3521
SHDN2
SHDN1
1.0M
137k
68.1k
10µF
V
IN
4.7µH 4.7µH
V
OUT1
3.3V
0.8A
V
OUT2
1.8V
0.6A
100k
100k
10µF
4.7µH
V
OUT3
1.2V
0.6A
221k
4415 F08
SHDN3
PWM
SW1A
SW1B
FB1
PGOOD2
PGOOD1
PGOOD3PGND1A
PGND2GNDPGND1B
ON
OFF
PWM
BURST
+
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LTC4415IDHC#TRPBF

Mfr. #:
Buy LTC4415IDHC#TRPBF
Manufacturer:
Analog Devices Inc.
Description:
Power Management Specialized - PMIC 2x 4A Ideal Diodes w/ Adj C Lim
Lifecycle:
New from this manufacturer.
Delivery:
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