LTC2953IDD-1#PBF Linear Technology, LTC2953IDD-1#PBF Datasheet - Page 13

• Manufacturer Part Number: LTC2953IDD-1#PBF
• Description: IC PB ON/OFF CONTROLLER 12DFN
• Manufacturer: Linear Technology

Specifications of LTC2953IDD-1#PBF

• Applications: Push Button, On/Off Controller
• Voltage - Supply: 2.7 V ~ 27 V
• Current - Supply: 14µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 12-DFN
• Ic Function: Push Button On/Off Controller With Voltage Monitoring
• Supply Voltage Range: 2.7V To 27V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: DFN
• No. Of Pins: 12
• Svhc: No
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Input: -

Note that only the push button input can enable system
power. The LTC2953 provides two enable output polarities
to allow DC/DC converter control (LTC2953-1) and external
power PFET control (LTC2953-2).
APPLICATIONS INFORMATION
PB OR UVLO
PUSH BUTTON CONTROL
Power On Sequence
To enable system power, the push button input ( ⎯ P ⎯ B ) must
be held low continuously for 32ms (t
enable output (EN/ ⎯ E ⎯ N ) is asserted, the LTC2953 starts
a 512ms internal timer (t
must be driven high within this 512ms window. This blank-
ing time represents the maximum time allowed for the
system to power up and initialize the circuits driving the
⎯ K ⎯ I ⎯ L ⎯ L input. If ⎯ K ⎯ I ⎯ L ⎯ L remains low at the end of the blanking
period, the enable output is released (see “Aborted Power
On Sequence” section). Figure 9 shows a normal power
on sequence.
(LTC2953-1)
(LTC2953-1)
KILL
KILL
INT
PB
EN
EN
Figure 9. Power On Timing (UVLO > 0.55V)
Figure 10. Power Off Interrupt Timing
DO NOT CARE
t
DB, ON
t
DB, OFF
DO NOT CARE
SHORT PULSE
KILL, ON BLANK
t
INT, Min
PB, UVLO AND KILL
t
KILL, ON BLANK
IGNORED
DB, ON
). The ⎯ K ⎯ I ⎯ L ⎯ L input
SYSTEM SETS
KILL HIGH
). Once the
SYSTEM SETS
POWER OFF
KILL LOW
SYSTEM
2953 F09
2953 F10
PB OR UVLO
(LTC2953-1)
Short Pulse Interrupt
To interrupt the μP, either ⎯ P ⎯ B or UVLO must be low for
at least 32ms (t
user has pressed the push button or that the supply is
running low. The μP would then perform power down
and housekeeping tasks and assert ⎯ K ⎯ I ⎯ L ⎯ L low when done.
This in turn releases the enable output, thus shutting off
system power. See Figure 10.
Note that either ⎯ P ⎯ B or UVLO can control the power down
sequence, but not both at the same time. For example, if
both ⎯ P ⎯ B and UVLO are high and the user presses the push
button, ⎯ P ⎯ B will be active and UVLO will be ignored until ⎯ P ⎯ B
is released or the power down sequence is complete.
Forced Power Off Sequence
The LTC2953 provides a failsafe feature that allows a user
to manually force a system power down. For cases when
the μP fails to respond to the interrupt signal, the user
can force a power down by pressing and holding either
the push button or the UVLO inputs low.
The length of time required to release the enable output
is given by a fi xed internal 64ms delay (t
adjustable power down timer delay (t
delay is set by placing an external capacitor on the PDT
pin. Use the following equation to calculate the capacitance
for the desired extra delay. C
capacitor:
C
See Figure 11.
PDT
Figure 11. Forced Power Off Timing with Adjustable Delay
(See Figure 5 for More Details)
PDT
= 1.56E-4 [μF/ms] • (t
EN
DB, OFF
t
PD, Min
). This signals the μP either that a
LONG PULSE
PDT
PDT
16 CYCLES
– 1ms)
t
PDT
is the PDT pin external
PDT
LTC2953
). The adjustable
PD, Min
) plus an
13
2953 F11
2953f