push button ON/OFF controller. The part contains a push
button input which controls the toggling of an open drain
enable output. The push button 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
⎯
K
⎯
I
⎯
L
⎯
L
timeout delay ensures proper power down.
The LTC2951 operates over a 2.7V to 26V 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.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is
a trademark of Linear Technology Corporation. All other trademarks are the property of
their respective owners.
APPLICATIO S
■
■
■
■
Portable Instrumentation Meters
Blade Servers
Portable Customer Service PDA
Desktop and Notebook Computers
TYPICAL APPLICATIO
V
IN
3V – 26V
V
IN
V
OUT
DC/DC
BUCK
SHDN
EN
V
IN
LTC2951-1
PB
GND KILLT
C
KILLT
*
0.033µF
EN
INT
KILL
OFFT
2951 TA01
R1
10k
INT
KILL
µP/µC
2V/DIV
128ms
PB
C
OFFT
*
0.033µF
*OPTIONAL
U
Turn On Debounce
25ms/DIV
2951 TA01b
U
U
2951f
1
LTC2951
ABSOLUTE
(Note 1)
AXI U RATI GS
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
Supply Voltage (V
IN
) ..................................– 0.3V to 33V
Input Voltages
⎯
P
⎯
B ............................................................– 6V to 33V
KILLT ....................................................– 0.3V to 2.7V
OFFT .....................................................– 0.3V to 2.7V
⎯
K
⎯
I
⎯
L
⎯
L .........................................................– 0.3V to 7V
Output Voltages
⎯
I
⎯
N
⎯
T .........................................................– 0.3V to 10V
EN/
⎯
E
⎯
N ....................................................– 0.3V to 10V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND 1
KILLT 2
PB 3
V
IN
4
9
8
7
6
5
INT
EN/EN
OFFT
KILL
DDB8 PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 165°C/W
EXPOSED PAD (PIN 9) UNCONNECTED
ORDER PART
NUMBER
LTC2951CDDB-1
LTC2951CDDB-2
LTC2951IDDB-1
LTC2951IDDB-2
DDB PART*
MARKING
LBTB
LBTD
LBTB
LBTD
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
IN
V
UVL
V
UVL(HYST)
PARAMETER
Supply Voltage Range
V
IN
Supply Current
V
IN
Undervoltage Lockout
V
IN
Undervoltage Lockout Hysteresis
The
●
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
Falling
●
●
●
●
2
U
U
W
W W
U
W
TOP VIEW
V
IN
1
PB 2
KILLT 3
GND 4
8 KILL
7 OFFT
6 EN/EN
5 INT
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 140°C/W
ORDER PART
NUMBER
LTC2951CTS8-1
LTC2951CTS8-2
LTC2951ITS8-1
LTC2951ITS8-2
TS8 PART*
MARKING
LTBTC
LTBTF
LTBTC
LTBTF
MIN
2.7
2.2
50
TYP
6
2.3
300
MAX
26.4
12
2.4
600
UNITS
V
µA
V
mV
2951f
LTC2951
ELECTRICAL CHARACTERISTICS
SYMBOL
Push Button Pin (
⎯
P
⎯
B)
V
⎯
P
⎯
B(MIN, MAX)
I
⎯
P
⎯
B
⎯
P
⎯
B Voltage Range
⎯
P
⎯
B Input Current
Single-Ended
2.5V < V
⎯
P
⎯
B
< 26.4V
V
⎯
P
⎯
B
= 1V
V
⎯
P
⎯
B
= 0.6V
⎯
P
⎯
B Falling
I
⎯
P
⎯
B
= –1µA
V
KILLT, OFFT
= 0V
V
KILLT, OFFT
= 1.3V
⎯
P
⎯
B Falling
→
Enable Asserted
OFFT Pin Float,
⎯
P
⎯
B Falling
→ ⎯
I
⎯
N
⎯
T Falling
●
●
●
●
●
●
The
●
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)
PARAMETER
CONDITIONS
MIN
–1
–1
–3
0.6
1
–2.4
2.4
100
26
9
–6
–9
0.8
1.6
–3
3
128
32
11.5
TYP
MAX
26.4
±1
–12
–15
1
2
–3.6
3.6
163
41
13.5
±1
0.11
0.57
10
30
30
400
100
9
200
512
128
11.5
256
0.11
650
163
13.5
325
±0.1
0.4
0.6
30
0.4
0.63
50
±0.1
UNITS
V
µA
µA
µA
V
V
µA
µA
ms
ms
ms
µA
V
V
mV
µA
µs
µs
ms
ms
ms
ms
µA
V
V
⎯
P
⎯
B(VTH)
V
⎯
P
⎯
B(VOC)
I
KILLT, OFFT(PU)
I
KILLT, OFFT(PD)
t
DB, ON
t
DB, OFF
t
OFFT
I
⎯
I
⎯
N
⎯
T(LKG)
V
⎯
I
⎯
N
⎯
T(VOL)
V
⎯
K
⎯
I
⎯
L
⎯
L(TH)
V
⎯
K
⎯
I
⎯
L
⎯
L(HYST)
I
⎯
K
⎯
I
⎯
L
⎯
L(LKG)
t
⎯
K
⎯
I
⎯
L
⎯
L(PW)
t
⎯
K
⎯
I
⎯
L
⎯
L(PD)
t
⎯
K
⎯
I
⎯
L
⎯
L, ON BLANK
t
⎯
K
⎯
I
⎯
L
⎯
L, OFF DELAY
t
⎯
K
⎯
I
⎯
L
⎯
L, OFF DELAY,
ADDITIONAL
⎯
P
⎯
B Input Threshold
⎯
P
⎯
B Open Circuit Voltage
KILLT/OFFT Pull Up Current
KILLT/OFFT Pull Down Current
Turn On Debounce Time
Internal Turn Off Debounce Time
Timing Pins (KILLT, OFFT)
●
●
●
●
●
Additional Adjustable Turn Off Time C
OFFT
= 1500pF
⎯
I
⎯
N
⎯
T Leakage Current
⎯
I
⎯
N
⎯
T Output Voltage Low
⎯
K
⎯
I
⎯
L
⎯
L Input Threshold Voltage
⎯
K
⎯
I
⎯
L
⎯
L Input Threshold Hysteresis
⎯
K
⎯
I
⎯
L
⎯
L Leakage Current
⎯
K
⎯
I
⎯
L
⎯
L Minimum Pulse Width
⎯
K
⎯
I
⎯
L
⎯
L Propagation Delay
⎯
K
⎯
I
⎯
L
⎯
L Turn On Blanking (Note 3)
Internal
⎯
K
⎯
I
⎯
L
⎯
L Turn Off Delay
(Note 4)
⎯
K
⎯
I
⎯
L
⎯
L Falling
→
Enable Released
⎯
K
⎯
I
⎯
L
⎯
L = Low, Enable Asserted
→
Enable
Released
KILLT Pin Float,
⎯
K
⎯
I
⎯
L
⎯
L = High,
⎯
I
⎯
N
⎯
T Asserted
→
Enable Released
V
⎯
K
⎯
I
⎯
L
⎯
L
= 0.6V
V
⎯
I
⎯
N
⎯
T
= 3V
I
⎯
I
⎯
N
⎯
T
= 3mA
⎯
K
⎯
I
⎯
L
⎯
L Falling
µP Handshake Pins (
⎯
I
⎯
N
⎯
T,
⎯
K
⎯
I
⎯
L
⎯
L)
●
●
●
●
●
●
●
●
●
●
●
●
●
Additional Adjustable
⎯
K
⎯
I
⎯
L
⎯
L Turn Off C
KILLT
= 1500pF
Delay (Note 4)
EN/
⎯
E
⎯
N Lock Out Time (Note 5)
EN/
⎯
E
⎯
N Leakage Current
EN/
⎯
E
⎯
N Voltage Output Low
Enable Released
→
Enable Asserted
V
EN/
⎯
E
⎯
N
= 1V, Sink Current Off
I
EN/
⎯
E
⎯
N
= 3mA
t
EN/
⎯
E
⎯
N, Lock Out
I
EN/
⎯
E
⎯
N(LKG)
V
EN/
⎯
E
⎯
N(VOL)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3:
The
⎯
K
⎯
I
⎯
L
⎯
L 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
⎯
K
⎯
I
⎯
L
⎯
L and
⎯
P
⎯
B inputs are ignored during this period. If
⎯
K
⎯
I
⎯
L
⎯
L
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
⎯
K
⎯
I
⎯
L
⎯
L turn off delay (t
⎯
K
⎯
I
⎯
L
⎯
L
,
OFF DELAY
) is the default
delay from the initiation of a power off sequence (
⎯
I
⎯
N
⎯
T falling,
⎯
K
⎯
I
⎯
L
⎯
L = high),
to the release of the enable output. The additional, adjustable
⎯
K
⎯
I
⎯
L
⎯
L turn
off delay (t
⎯
K
⎯
I
⎯
L
⎯
L
,
OFF DELAY, ADDITIONAL
) uses an optional external capacitor
(C
KILLT
) to provide extra delay from
⎯
I
⎯
N
⎯
T falling to the release of the enable
output. If the
⎯
K
⎯
I
⎯
L
⎯
L input switches low at any time during
⎯
K
⎯
I
⎯
L
⎯
L turn off
delay, enable is released, thus turning off system power.
Note 5:
The enable lock out time is designed to allow an application to
properly power down such that the next power up sequence starts from a
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