LTC4420CDD Datasheet, PDF (1/24 Pages) Linear Integrated Systems – 18V Dual Input Micropower PowerPath Prioritizer with Backup Supply Monitoring

LTC4420
18V Dual Input Micropower
PowerPath Prioritizer with
Backup Supply Monitoring
Features
n _{Selects Highest Priority Valid Supply from Two}
Inputs
n _{Wide 1.8V to 18V Operating Range}
n _{Internal Dual 2Ω, 0.5A Switches}
n _{Low 3.6µA Operating Current}
n _{Low 320nA V2 Current When V1 Connected to OUT}
n _{Blocks Reverse and Cross Conduction Currents}
n _{Reverse Supply Protection to –15V}
n _{Built-In V2 Test with Optional V2 Disconnect}
n _{V2 Freshness Seal/Ship Mode}
n _{±1.5% Accurate Adjustable Switchover Threshold}
n _{±2.3% Accurate V2 Monitor and Comparator}
n _{Overcurrent and Thermal Protection}
n _{Thermally Enhanced 12-Pin 3mm × 3mm}
DFN and 12-Lead Exposed Pad MSOP Packages
Applications
n _{Low Power Battery Backup}
n _{Portable Equipment}
n _{Point-of-Sale (POS) Equipment}
Description
The LTC^®4420 is a dual input monolithic PowerPath™
prioritizer, with low operating current, that provides
backup switchover for keeping critical circuitry alive dur-
ing brownout and power loss conditions. Unlike diode-OR
products, little current is drawn from the inactive supply
even if its voltage is greater than the active supply.
Internal 2Ω, current limited PMOS switches provide
power path selection from a primary input (V1) or a backup
input (V2) to the output. Two adjustable voltage monitors
set via external resistive dividers provide flexibility in set-
ting V1 to V2 switchover and V2 undervoltage thresholds.
V1 is monitored continuously while V2 supply monitoring
includes controllable low duty cycle UV monitoring. When
primary input V1 drops, the ADJ monitor causes OUT to
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
output droop.
Auxiliary voltage monitor CMP1 provides flexible voltage
monitoring and output V2OK provides V2 undervoltage
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 Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Typical Application
5V WALL
ADAPTER
+
10µF
7.4V
Li-Ion
Typical Switchover Waveforms
V1
OUT
1M
ADJ CMPOUT1
237k
CMP1 V2OK
121k
LTC4420
V2
V2DIS
1M
V1UV
OUT
1M
V2OK
V2
2V/DIV
V1
2V/DIV
V2 MONITORING
INTERVAL
SWITCHOVER
THRESHOLD
V2 UNDERVOLTAGE
AND DISCONNECT
4.02M
280k
V2UV V2TEST
GNDSW
GND
TYPICAL VALUES:
SWITCHOVER THRESHOLD: V1 < 4V (V1 FALLING)
4420 TA01a
V1UV THRESHOLD: V1 < 4.4V (V1 FALLING)
V2OK THRESHOLD: V2 < 6V (V2 FALLING)
C_OUT = 10µF
I_LOAD = 100mA
20ms/DIV
OUT
4420 TA01b
4420f
For more information www.linear.com/LTC4420
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