manages system power via a pushbutton interface. An
enable output toggles system power while an interrupt
output provides debounced pushbutton status. The inter-
rupt output can be used in menu driven applications to
request a system power-down. A power kill input allows
a microprocessor or system to reset the enable output,
effectively powering down the system. Independently
adjustable on and off timers allow dependable pushbutton
control of the enable output and resistance to accidental
toggling of system power.
The LTC2954 operates over a wide 2.7V to 26.4V input volt-
age range to accommodate a wide variety of input power
supplies. Very low quiescent current (6μA typical) makes
the LTC2954 ideally suited for battery powered applications.
Two versions of the part are available to accommodate
either positive or negative enable polarities.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Adjustable Power On/Off Timers
Low Supply Current: 6μA
Wide Operating Voltage Range: 2.7V to 26.4V
Low Leakage EN Output (LTC2954-1) Allows DC/DC
Converter Control
High Voltage
EN
Output (LTC2954-2) 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™ Packages
APPLICATIONS
n
n
n
n
n
Pushbutton PowerPath™ Control
Portable Instrumentation Meters
Blade Servers
Portable Customer Service PDA
Desktop and Notebook Computers
TYPICAL APPLICATION
Pushbutton On/Off with Interrupt
V
IN
V
OUT
DC/DC
9V
100k
100k
PB
TURN-ON PULSE
SHORT PULSE
LONG PULSE
+
EN
V
IN
LTC2954-2
PB
GND
ONT
EN
INT
KILL
PDT
2954 TA01a
TURNS ON
STAYS ON
TURNS OFF
10k
INT
μP/μC
KILL
INT
INTERRUPT
INTERRUPT
2954 TA01b
1μF
t
PDT
= 6.4 SECONDS
2954fb
1
LTC2954
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (V
IN
) .................................. –0.3V to 33V
Input Voltages
PB
............................................................ –6V to 33V
ONT ...................................................... –0.3V to 2.7V
PDT ....................................................... –0.3V to 2.7V
KILL
......................................................... –0.3V to 7V
Output Voltages
INT
......................................................... –0.3V to 10V
EN/EN .................................................... –0.3V to 33V
Operating Temperature Range
LTC2954C-1 ............................................. 0°C to 70°C
LTC2954C-2 ............................................. 0°C to 70°C
LTC2954I-1 ..........................................–40°C to 85°C
LTC2954I-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
ONT 2
PB
3
V
IN
4
9
8
7
6
5
INT
EN/EN
PDT
KILL
TOP VIEW
V
IN
1
PB
2
ONT 3
GND 4
8
KILL
7 PDT
6 EN/EN
5
INT
DDB PACKAGE
8-LEAD (3mm 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 165°C/W
EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 140°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC2954CDDB-1#PBF
LTC2954CDDB-2#PBF
LTC2954IDDB-1#PBF
LTC2954IDDB-2#PBF
LTC2954CTS8-1#PBF
LTC2954CTS8-2#PBF
LTC2954ITS8-1#PBF
LTC2954ITS8-2#PBF
LEAD BASED FINISH
LTC2954CDDB-1
LTC2954CDDB-2
LTC2954IDDB-1
LTC2954IDDB-2
LTC2954CTS8-1
LTC2954CTS8-2
LTC2954ITS8-1
LTC2954ITS8-2
TAPE AND REEL
LTC2954CDDB-1#TRPBF
LTC2954CDDB-2#TRPBF
LTC2954IDDB-1#TRPBF
LTC2954IDDB-2#TRPBF
LTC2954CTS8-1#TRPBF
LTC2954CTS8-2#TRPBF
LTC2954ITS8-1#TRPBF
LTC2954ITS8-2#TRPBF
TAPE AND REEL
LTC2954CDDB-1#TR
LTC2954CDDB-2#TR
LTC2954IDDB-1#TR
LTC2954IDDB-2#TR
LTC2954CTS8-1#TR
LTC2954CTS8-2#TR
LTC2954ITS8-1#TR
LTC2954ITS8-2#TR
PART MARKING*
LCJG
LCNJ
LCJG
LCNJ
LTCJH
LTCNK
LTCJH
LTCNK
PART MARKING*
LCJG
LCNJ
LCJG
LCNJ
LTCJH
LTCNK
LTCJH
LTCNK
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-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
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-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
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
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/
2954fb
2
LTC2954
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
PB
Voltage Range
PB
Input Current
Single-Ended
2.5V < V
PB
< 26.4V
V
PB
= 1V
V
PB
= 0.6V
PB
Falling
I
PB
= –1μA
Enable Released
→
Enable Asserted
V
EN/
EN
= 1V, Sink Current Off
V
EN/
EN
= 26.4V, Sink Current Off
I
EN/
EN
= 500μA
V
ONT
= 0V
V
ONT
= 1.3V
ONT Pin Float,
PB
Falling
→
Enable Asserted
l
l
l
l
l
l
l
l
l
l
l
l
l
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
MIN
2.7
TYP
6
MAX
26.4
12
2.5
700
UNITS
V
μA
V
mV
2.2
50
2.3
400
Pushbutton, Enable (PB, EN/EN))
V
PB(MIN,
MAX)
I
PB
–1
–1
–3
0.6
1
200
–6
–9
0.8
1.6
256
26.4
±1
–12
–15
1
2
325
±0.1
±1
0.11
–2.4
2.4
26
9
–2.4
2.4
26
52
9
26
35
–3
3
32
11.5
–3
3
32
64
11.5
32
43.5
0.4
–3.6
3.6
41
13.5
–3.6
3.6
41
82
13.5
41
54.5
±1
0.11
0.57
10
30
30
400
512
650
0.6
30
0.4
0.63
50
±0.1
V
μA
μA
μA
V
V
ms
μA
μA
V
μA
μA
ms
ms
μA
μA
ms
ms
ms
ms
ms
μA
V
V
mV
μA
μs
μs
ms
V
PB(VTH)
V
PB(VOC)
t
EN, LOCKOUT
I
EN(LKG)
V
EN(VOL)
I
ONT(PU)
I
ONT(PD)
t
DB, ON
t
ONT
I
PDT(PU)
I
PDT(PD)
t
DB, OFF
t
PD,MIN
t
PDT
t
INT,MIN
t
INT,MAX
I
INT(LKG)
V
INT(VOL)
V
KILL(TH)
V
KILL(HYST)
I
KILL(LKG)
t
KILL(PW)
t
KILL(PD)
t
KILL,ON
BLANK
PB
Input Threshold
PB
Open Circuit Voltage
EN/EN Lockout Time (Note 5)
EN/EN Leakage Current
EN/EN Voltage Output Low
ONT Pull-Up Current
ONT Pull-Down Current
Internal Turn-On Debounce Time
Power-On Timing Pin (ONT)
Additional Adjustable Turn-On Time C
ONT
= 1500pF
PDT Pull-Up Current
PDT Pull-Down Current
Turn-Off Interrupt Debounce Time
V
PDT
= 0V
V
PDT
= 1.3V
PB
Falling
→
INT
Falling
Power-Down Timing Pin (PDT)
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
Internal
PB
Power-Down Debounce PDT Pin Float,
PB
Falling
→
Enable Released
Time (Note 4)
Additional Adjustable
PB
Power-Down Debounce Time
Minimum
INT
Pulse Width
Maximum
INT
Pulse Width
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
KILL
Turn-On Blanking (Note 3)
KILL
Falling
→
Enable Released
KILL
= Low, Enable Asserted
→
Enable Released
V
KILL
= 0.6V
C
PDT
= 1500pF
INT
Asserted
→
INT
Released
C
PDT
= 1500pF,
INT
Asserted
→
INT
Released
V
INT
= 3V
I
INT
= 3mA
KILL
Falling
μP Handshake Pins (INT,
KILL)
2954fb
3
LTC2954
ELECTRICAL CHARACTERISTICS
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
or t
ONT
.
Note 4:
To manually force an immediate release of the EN/EN pin, the
pushbutton input must be held low for at least t
PD,MIN
(internal default
power-down timer) + t
PDT
(adjustable by placing external capacitor at
PDT pin).
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
中风发生时，一切都是以秒来计算的。延误治疗可能导致大脑重大损伤。伦敦大学医学院的一位博士Alistair McEwan已经获得行为医学研究所(Action Medical Research)的同意，为急救人员开发一种无线诊断系统来减少时间延误。感谢抗血栓药物，一些病人在病情发作的三个小时之内可以完全恢复。但出血也会导致中风。医生在治疗之前需要确定发病原因，因为不适当的服用抗血栓药物会加重损害。...[详细]
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