LTC4420
18V Dual Input Micropower
PowerPath Prioritizer with
Backup Supply Monitoring
FEATURES DESCRIPTION
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Selects Highest Priority Valid Supply from Two The LTC 4420 is a dual input monolithic PowerPath
prioritizer, with low operating current, that provides
Inputs
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backup switchover for keeping critical circuitry alive dur-
Wide 1.8V to 18V Operating Range
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ing brownout and power loss conditions. Unlike diode-OR
Internal Dual 2, 0.5A Switches
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products, little current is drawn from the inactive supply
Low 3.6A Operating Current
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even if its voltage is greater than the active supply.
Low 320nA V2 Current When V1 Connected to OUT
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Blocks Reverse and Cross Conduction Currents
Internal 2, current limited PMOS switches provide
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Reverse Supply Protection to 15V
power path selection from a primary input (V1) or a backup
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Built-In V2 Test with Optional V2 Disconnect
input (V2) to the output. Two adjustable voltage monitors
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V2 Freshness Seal/Ship Mode
set via external resistive dividers provide flexibility in set-
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1.5% Accurate Adjustable Switchover Threshold
ting V1 to V2 switchover and V2 undervoltage thresholds.
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2.3% Accurate V2 Monitor and Comparator
V1 is monitored continuously while V2 supply monitoring
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Overcurrent and Thermal Protection
includes controllable low duty cycle UV monitoring. When
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Thermally Enhanced 12-Pin 3mm 3mm
primary input V1 drops, the ADJ monitor causes OUT to
DFN and 12-Lead Exposed Pad MSOP Packages
be switched to V2. When V2 drops, it is disconnected from
OUT if V2DIS is low. Fast non-overlap switchover circuitry
prevents reverse and cross conduction while minimizing
APPLICATIONS
output droop.
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Low Power Battery Backup
Auxiliary voltage monitor CMP1 provides flexible voltage
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Portable Equipment
monitoring and output V2OK provides V2 undervoltage
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Point-of-Sale (POS) Equipment
status. Freshness seal mode prevents V2 battery discharge
during storage or shipment.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Analog Devices, Inc. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
Typical Switchover Waveforms
5V WALL
V1 OUT OUT
ADAPTER
1M 1M 1M
V2 MONITORING
ADJ V1UV
10F CMPOUT1
INTERVAL
237k
V2
2V/DIV
CMP1 V2OK V2OK
SWITCHOVER
121k
V1
THRESHOLD
LTC4420
2V/DIV
V2 UNDERVOLTAGE
AND DISCONNECT
V2 V2DIS
+
7.4V
4.02M
Li-Ion
V2UV V2TEST
OUT
C = 10F
OUT
280k
I = 100mA
TYPICAL VALUES: LOAD
GNDSW SWITCHOVER THRESHOLD: V1 < 4V (V1 FALLING)
4420 TA01b
20ms/DIV
V1UV THRESHOLD: V1 < 4.4V (V1 FALLING)
GND
4420 TA01a
V2OK THRESHOLD: V2 < 6V (V2 FALLING)
4420fa
1
For more information www.linear.com/LTC4420LTC4420
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2)
Terminal Voltages Pin Currents (Note 2)
V1, V2 ......................................................15V to 24V ADJ, CMP1, V2UV, CMPOUT1, GNDSW .............1mA
OUT ....................................................... 0.3V to 24V V2TEST, V2DIS, V2OK ......................................1mA
OUT V2 .................................................24V to 39V Operating Ambient Temperature Range
OUT V1 .................................................24V to 39V LTC4420C ................................................ 0C to 70C
Input Voltages LTC4420I .............................................40C to 85C
ADJ, CMP1, V2UV, V2TEST, V2DIS Junction Temperature (Notes 4, 5) ........................ 125C
(Note 3) ................................................ 0.3V to 24V Storage Temperature Range .................. 65C to 150C
Output Voltages Lead Temperature (Soldering, 10 sec)
CMPOUT1, GNDSW, V2OK (Note 3) ...... 0.3V to 24V MSOP Package .................................................300C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
1 V2
V1 12
1
V1 12 V2
V2DIS
V2TEST 2 11
V2TEST 2 11 V2DIS
3
CMP1 10 V2UV CMP1 3 13 10 V2UV
13
GND
GND ADJ 4 9 OUT
ADJ 4 9 OUT
GND 5 8 V2OK
GND 5 8 V2OK
CMPOUT1 6 7 GNDSW
CMPOUT1 6 7 GNDSW
MSE PACKAGE
DD PACKAGE
12-LEAD PLASTIC MSOP
12-LEAD (3mm 3mm) PLASTIC DFN
T = 125C, = 40C/W
JMAX JA
T = 125C, = 43C/W
JMAX JA
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB