pushbutton ON/OFF controller. The part contains a push-
button input which controls the toggling of an open-drain
enable output. The pushbutton turn OFF debounce time
is externally programmable, while the turn ON debounce
time is fixed at 128ms. A simple microprocessor interface
allows for proper system housekeeping prior to power-
down. Under system fault conditions, an adjustable
KILL
timeout delay ensures proper power-down.
The LTC2951 operates over a 2.7V to 26.4V input voltage
range to accommodate a variety of input power supplies.
Very low quiescent current (6µA typical) makes the
LTC2951 ideally suited for battery powered applications.
Two versions of the part are available to accommodate
either positive or negative enable polarities. The parts
are available in 8-pin 3mm × 2mm DFN and ThinSOT
packages.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
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n
Adjustable Pushbutton Debounce and Delay Timers
Low Supply Current: 6µA
Wide Operating Voltage Range: 2.7V to 26.4V
EN Output (LTC2951-1) Allows DC/DC Converter
Control
EN
Output (LTC2951-2) Allows Circuit Breaker
Control
Simple Interface Allows Graceful µP Shutdown
High Input Voltage
PB
Pin with Internal Pull-Up
Resistor
±10kV ESD HBM on
PB
Input
Accurate 0.6V Threshold on
KILL
Comparator Input
8-Pin 3mm × 2mm DFN and ThinSOT
TM
Packages
APPLICATIONS
n
n
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Portable Instrumentation Meters
Blade Servers
Portable Customer Service PDA
Desktop and Notebook Computers
TYPICAL APPLICATION
V
IN
2.7V TO 26.4V
V
IN
V
OUT
DC/DC
BUCK
SHDN**
EN
2V/DIV
INT
KILL
µP/µC
PB
128ms
Turn-On Debounce
V
IN
LTC2951-1
PB
GND
KILLT
C
KILLT
*
0.033µF
2951 TA01
EN
INT
KILL
OFFT
C
OFFT
*
0.033µF
R1
10k
*OPTIONAL
**SHDN INTERNALLY PULLED UP BY DC/DC
25ms/DIV
2951 TA01b
295112fb
1
LTC2951-1/LTC2951-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (V
IN
) .................................. –0.3V to 33V
Input Voltages
PB
............................................................. –6V to 33V
KILLT .................................................... –0.3V to 2.7V
OFFT ..................................................... –0.3V to 2.7V
KILL
........................................................–0.3V to 7V
Output Voltages
INT
......................................................... –0.3V to 10V
EN/EN .................................................... –0.3V to 10V
Operating Temperature Range
LTC2951C-1 ............................................. 0°C to 70°C
LTC2951C-2 ............................................. 0°C to 70°C
LTC2951I-1...........................................–40°C to 85°C
LTC2951I-2 ..........................................–40°C to 85°C
Storage Temperature Range
DFN Package ..................................... –65°C to 125°C
TSOT-23 .............................................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
PIN CONFIGURATION
TOP VIEW
GND 1
KILLT 2
PB
3
V
IN
4
9
8
7
6
5
INT
EN/EN
OFFT
KILL
TOP VIEW
V
IN
1
PB
2
KILLT 3
GND 4
8
KILL
7 OFFT
6 EN/EN
5
INT
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 140°C/W
T
JMAX
= 125°C,
θ
JA
= 165°C/W
EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL
ORDER INFORMATION
LEAD FREE FINISH
LTC2951CDDB-1#PBF
LTC2951CDDB-2#PBF
LTC2951IDDB-1#PBF
LTC2951IDDB-2#PBF
LTC2951CTS8-1#PBF
LTC2951CTS8-2#PBF
LTC2951ITS8-1#PBF
LTC2951ITS8-2#PBF
TAPE AND REEL
LTC2951CDDB-1#TRPBF
LTC2951CDDB-2#TRPBF
LTC2951IDDB-1#TRPBF
LTC2951IDDB-2#TRPBF
LTC2951CTS8-1#TRPBF
LTC2951CTS8-2#TRPBF
LTC2951ITS8-1#TRPBF
LTC2951ITS8-2#TRPBF
PART MARKING*
LBTB
LBTD
LBTB
LBTD
LTBTC
LTBTF
LTBTC
LTBTF
PACKAGE DESCRIPTION
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead Plastic TSOT
8-Lead Plastic TSOT
8-Lead Plastic TSOT
8-Lead Plastic TSOT
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
295112fb
2
LTC2951-1/LTC2951-2
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
IN
V
UVL
V
UVL(HYST)
V
PB(MIN,
MAX)
I
PB
V
PB(VTH)
t
EN/EN, Lockout
I
EN/EN(LKG)
V
EN/EN(VOL)
V
PB(VOC)
I
KILLT, OFFT(PU)
I
KILLT, OFFT(PD)
t
DB, ON
t
DB, OFF
t
OFFT
I
INT(LKG)
V
INT(VOL)
V
KILL(TH)
V
KILL(HYST)
I
KILL(LKG)
t
KILL(PW)
t
KILL(PD)
PARAMETER
Supply Voltage Range
V
IN
Supply Current
V
IN
Undervoltage Lockout
V
IN
Undervoltage Lockout Hysteresis
PB
Voltage Range
PB
Input Current
Single-Ended
2.5V < V
PB
< 26.4V
V
PB
= 1V
V
PB
= 0.6V
PB
Falling
Enable Released
→
Enable Asserted
V
EN/EN
= 1V, Sink Current Off
I
EN/EN
= 3mA
I
PB
= –1µA
V
KILLT, OFFT
= 0V
V
KILLT, OFFT
= 1.3V
PB
Falling
→
Enable Asserted
OFFT Pin Float,
PB
Falling
→
INT
Falling
C
OFFT
= 1500pF
V
INT
= 3V
I
INT
= 3mA
KILL
Falling
V
KILL
= 0.6V
KILL
Falling
→
Enable Released
KILL
= Low, Enable Asserted
→
Enable Released
KILLT Pin Float,
KILL
= High,
INT
Asserted
→
Enable Released
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 2.7V to 26.4V, unless otherwise noted. (Note 2)
CONDITIONS
Steady-State Operation
System Power-On, V
IN
= 2.7V to 24V
V
IN
Falling
l
l
l
l
MIN
2.7
TYP
6
MAX
26.4
12
2.4
600
26.4
UNITS
V
µA
V
mV
V
µA
µA
µA
V
ms
µA
V
V
µA
µA
ms
ms
ms
µA
V
V
mV
µA
µs
µs
ms
ms
ms
2.2
50
–1
–1
–3
0.6
200
2.3
300
Pushbutton, Enable (PB, EN/
EN)
l
l
l
l
l
l
l
l
l
–6
–9
0.8
256
0.11
±1
–12
–15
1
325
±0.1
0.4
2
–3.6
3.6
163
41
13.5
±1
PB
Input Threshold
EN/EN Lockout Time (Note 5)
EN/EN Leakage Current
EN/EN Voltage Output Low
PB
Open-Circuit Voltage
KILLT/OFFT Pull-Up Current
KILLT/OFFT Pull-Down Current
Turn-On Debounce Time
Internal Turn-Off Debounce Time
Additional Adjustable Turn-Off Time
INT
Leakage Current
INT
Output Voltage Low
KILL
Input Threshold Voltage
KILL
Input Threshold Hysteresis
KILL
Leakage Current
KILL
Minimum Pulse Width
KILL
Propagation Delay
1
–2.4
2.4
100
26
9
1.6
–3
3
128
32
11.5
Timing Pins (KILLT, OFFT)
l
l
l
l
l
µP Handshake Pins (INT,
KILL)
l
l
l
l
l
l
l
l
l
l
0.11
0.57
10
30
0.6
30
0.4
0.63
50
±0.1
30
t
KILL,
ON BLANK
KILL
Turn-On Blanking (Note 3)
t
KILL,
OFF DELAY
Internal
KILL
Turn-Off Delay (Note 4)
400
100
9
512
128
11.5
650
163
13.5
t
KILL,OFF
DELAY,
Additional Adjustable
KILL
Turn-Off Delay C
KILLT
= 1500pF
(Note 4)
ADDITIONAL
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3:
The
KILL
turn-on blanking timer period is the waiting period
immediately after the enable output is asserted. This blanking time allows
sufficient time for the DC/DC converter and the µP to perform power-up
tasks. The
KILL
and
PB
inputs are ignored during this period. If
KILL
remains low at the end of this time period, the enable output is released,
thus turning off system power. This time delay does not include t
DB,ON
.
Note 4:
The internal
KILL
turn-off delay (t
KILL
,
OFF DELAY
) is the default
delay from the initiation of a power-off sequence (INT falling,
KILL
= high),
to the release of the enable output. The additional, adjustable
KILL
turn-off
delay (t
KILL
,
OFF DELAY, ADDITIONAL
) uses an optional external capacitor
(C
KILLT
) to provide extra delay from
INT
falling to the release of the enable
output. If the
KILL
input switches low at any time during
KILL
turn-off
delay, enable is released, thus turning off system power.
Note 5:
The enable lockout time is designed to allow an application to
properly power down such that the next power-up sequence starts from a
FPGA/CPLD
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