LTC2952CF datasheet(21/28 Pages) LINER

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LTC2952

2952f

2952 F12

KILL

INTERNAL

ON/OFF SIGNAL

tKILL, ON BLANKING

DON'T CARE

Figure 12.

⎯K⎯I⎯L⎯L Initiated Shutdown

wait time expires, the WDE pin transitions again (this time

from high to low) at t12, causing the 500ms timer to reset

again. Finally, the third 500ms timer which starts at t12

expires without any further extension at t13 causing the

EN pin to go low, shutting down the DC/DC converter.

Setting Up Different Conﬁgurations

The various conﬁgurations discussed previously are sum-

marized here in Table 2, including the ideal diode power

paths state (ID1-primary, ID2-secondary). Note that an

input above 0.515V (typical rising threshold) on the M1

and M2 pins is indicated with a 1 and an input below

0.500V (typical falling threshold) is represented by a 0.

Also, an enabled ideal diode driver is indicated with a 1

and a disabled driver is indicated with a 0.

Table 2. Mode Table

Mode Description

ID1

ID2

Both Diodes Enabled

Primary Diode Off, Secondary

Diode On

01001

Primary Diode Off, Secondary

Diode On

01101

Power Path Off, PB Overwrite

Transitional Power Path Off,

PB Overwrite

10111

Push-Button Power Path Off

Push-Button Power Path On

APPLICATIONS INFORMATION

Figure 13. Power-On/Power-Off Sequence with Extended Shutdown/Housekeeping Wait Time

2952 F13

KILL

INTERNAL

ON/OFF SIGNAL

tKILL, ON BLANKING < tKILL, OFF WAIT

WDE

t10

t11

t12

t13

DON'T CARE

EXTENDED HOUSE KEEPING TIME

tKILL, OFF WAIT

tEN, LOCKOUT

< tKILL, OFF WAIT

⎯K⎯I⎯L⎯L Power Turn-Off During Normal Operation

Once the system has powered on and is operating nor-

mally, the system can turn off power by setting

⎯K⎯I⎯L⎯L low

as shown in the timing diagram in Figure 12. At t9, ⎯K⎯I⎯L⎯L

is set low and this immediately causes the LTC2952 to

pull EN low, turning off the DC/DC converter.

Extended Power During Turn-Off

In the shutdown process, the availability of power can be

extended by providing edges to the WDE pin during the

⎯K⎯I⎯L⎯L Off Wait time. The timing diagram in Figure 13 is

similar to the power-on/power-off sequence timing diagram

(Figure 10) except for the edges on the WDE pin during the

shutdown process. At time t10, the internal ON/OFF signal

transitions low. When this happens, the DC/DC converter

providing power to the system will be shut off in 500ms

unless the WDE pin is toggled.

When the WDE pin transitions at t11, the LTC2952 resets

the 500ms

⎯K⎯I⎯L⎯L Off Wait timer. Before this second 500ms

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