LTC2950IDDB-1#TRPBF Linear Technology, LTC2950IDDB-1#TRPBF Datasheet - Page 11

• Manufacturer Part Number: LTC2950IDDB-1#TRPBF
• Description: IC PUSH BUTTON ON/OFF CTRLR 8DFN
• Manufacturer: Linear Technology

Specifications of LTC2950IDDB-1#TRPBF

• Applications: Push Button, On/Off Controller
• Voltage - Supply: 2.7 V ~ 26.4 V
• Current - Supply: 6µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-DFN
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Pin Count: 8
• Mounting: Surface Mount
• Package Type: DFN EP
• Case Length: 3mm
• Screening Level: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Input: -
• Lead Free Status / Rohs Status: Compliant

applicaTions inForMaTion
Aborted Power On Sequence
The power on sequence is aborted when the KILL remains
low after the end of the 512ms blanking time. Figure 2 is
a simplified version of an aborted power on sequence.
At time t
turning off the DC/DC converter).
µP Turns Off Power During Normal Operation
Once the system has powered on and is operating nor-
mally, the µP can turn off power by setting KILL low, as
shown in Figure 3. At time t
This immediately pulls EN low, thus turning off the DC/
DC converter.
DC/DC Turn Off Blanking
When the DC/DC converter is turned off, it can take a sig-
nificant amount of time for its output to decay to ground. It
is desirable to wait until the output of the DC/DC converter
is near ground before allowing the user (via PB) to restart
the converter. This condition guarantees that the µP has
always powered down completely before it is restarted.
KILL
PB
EN
ABORT,
Figure 3. µP Turns Off Power (LTC2950-1)
XXX DON’T CARE
since KILL is still low, EN pulls low (thus
KILL
, KILL is set low by the µP .
KILL LOW
µP SETS
TURNS OFF
t
KILL
DC/DC
2950 F03
Figure 4 shows the µP turning power off. After a low on
KILL releases enable, the internal 256ms timer ignores
the PB pin. This is shown as t
LTC2950-1, LTC2950-2 VERSIONS
The LTC2950-1 (high true EN) and LTC2950-2 (low true
EN) differ only by the polarity of the EN/EN pin. Both ver-
sions allow the user to extend the amount of time that the
PB must be held low in order to begin a valid power on/
off sequence. An external capacitor placed on the ONT
pin adds additional time to the turn on time. An external
capacitor placed on the OFFT pin adds additional time to
the turn off time. If no capacitor is placed on the ONT
(OFFT) pin, then the turn on (off) duration is given by an
internally fixed 32ms timer.
The LTC2950 fixes the KILL turn off delay time (t
DELAY
switched low/high a maximum of 1024ms after initiating
a valid turn off sequence. Note that in a typical application,
a µP or µC would set KILL low prior to the 1024ms timer
period (t
PB BLANKING
) at 1024ms. This means that the EN/EN pin will be
KILL
PB
EN
Figure 4. DC/DC Turn Off Blanking (LTC2950-1)
7
in Figure 1).
LTC2950-1/LTC2950-2
XXX DON’T CARE
POWER ON
EN/EN
, LOCKOUT in Figure 4.
TURNS OFF
DC/DC
t
EN/EN, LOCKOUT
PB IGNORED
256ms
µP SETS
KILL LOW
KILL, OFF
11
295012fd
2950 F04