LTC4420

1

4420f

For more information www.linear.com/LTC4420

Typical applicaTion

FeaTures

DescripTion

18V Dual Input Micropower

PowerPath Prioritizer with

Backup Supply Monitoring

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

powerpathselectionfromaprimaryinput(V1)orabackup

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.FreshnesssealmodepreventsV2batterydischarge

during storage or shipment.

applicaTions

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

n

Low Power Battery Backup

n

Portable Equipment

n

Point-of-Sale (POS) Equipment

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 Switchover Waveforms

SWITCHOVER

THRESHOLD

V2 MONITORING

INTERVAL

V2 UNDERVOLTAGE

AND DISCONNECT

OUT

20ms/DIV

V1

2V/DIV

V2

2V/DIV

4420 TA01b

+

V1

ADJ

V1UV

V2OK

TYPICAL VALUES:

SWITCHOVER THRESHOLD: V1 < 4V (V1 FALLING)

CMP1

V2

V2UV

GNDSW

1M

1M

1M

OUT

237k

121k

OUT

5V WALL

ADAPTER

CMPOUT1

V2OK

V2DIS

V2TEST

LTC4420

GND

4420 TA01a

4.02M

V1UV THRESHOLD: V1 < 4.4V (V1 FALLING)

V2OK THRESHOLD: V2 < 6V (V2 FALLING)

7.4V

Li-Ion

280k

10µF