LTC2951

13

2951f

Power Path Switching

The ⎯E⎯N open drain output of the LTC2951-2 is designed to

switch on/off an external power PFET. This allows a user

to connect/disconnect a power supply (or battery) to its

load by toggling the ⎯P⎯B pin. Figure 7 shows the LTC2951-2

controlling a two cell Li-Ion battery application. The ⎯I⎯N⎯T

and ⎯K⎯I⎯L⎯L pins are connected to the output of the PFET

through a resistor divider. The ⎯K⎯I⎯L⎯L pin serves as a voltage

circuited 30µs later.

R1

909k

1%

R4

100k

1%

C3*

0.1

µF

2951 F07

C4

0.1

µF

CERAMIC

*OPTIONAL

OPEN DRAIN OUTPUT

R5

100K

M1

+

4.2V

SINGLE CELL

Li-Ion BATTERY

+

4.2V

SINGLE CELL

Li-Ion BATTERY

OPTIONAL GLITCH

FILTER CAPACITOR

PB

EN

INT

KILL

LTC2951-2

GND

OFFT

0.033

µF

0.033

µF

KILLT

PB

LTC2951-1

GND

R6

5k

2951 F08

TRACE

CAPACITANCE

PARASITICS

C5

0.1

µF

DETAILS OMITTED

FOR CLARITY

TRACE

INDUCTANCE

NOISE

EN

INT

KILL

OFFT

KILLT

Figure 7. Power Path Control with 6V Under Voltage Detect

Figure 8. Filtering for Noisy ⎯P⎯B Traces

⎯P⎯B Pin in a Noisy Environment

The rugged ⎯P⎯B pin is designed to operate in noisy envi-

(<33V) will not damage the rugged ⎯P⎯B pin. Additionally,

the ⎯P⎯B pin can withstand ESD HBM strikes up to ±10kV.

In order to keep external noise from coupling inside the

LTC2951, place an R-C network close to the ⎯P⎯B pin. A

5k resistor and a 0.1µF capacitor should suffice for most

noisy applications (see Figure 8).

TYPICAL APPLICATIO S