LINER LTC2951 Push button on/off controller Datasheet

LTC2951
Push Button On/Off
Controller
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DESCRIPTIO
FEATURES
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Adjustable Push Button Debounce and Delay
Timers
Low Supply Current: 6µA
Wide Operating Voltage Range: 2.7V to 26V
EN Output (LTC2951-1) Allows DC/DC Converter
Control
⎯E⎯N Output (LTC2951-2) Allows Circuit Breaker
Control
Simple Interface Allows Graceful µP Shut Down
High Input Voltage ⎯P⎯B Pin with Internal Pull Up
Resistor
±10kV ESD HBM on ⎯P⎯B Input
Accurate 0.6V Threshold on ⎯K⎯I⎯L⎯L Comparator Input
8-Pin 3mm × 2mm DFN and ThinSOTTM Packages
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APPLICATIO S
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Portable Instrumentation Meters
Blade Servers
Portable Customer Service PDA
Desktop and Notebook Computers
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.
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The LTC®2951 is a micropower, wide input voltage range
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.
TYPICAL APPLICATIO
Turn On Debounce
VIN
3V – 26V
VIN
VOUT
DC/DC
BUCK
SHDN
EN
VIN
R1
10k
EN
LTC2951-1
2V/DIV
INT
INT
PB
KILL
KILL
GND KILLT
OFFT
µP/µC
PB
128ms
2951 TA01
CKILLT*
0.033µF
25ms/DIV
COFFT*
0.033µF
2951 TA01b
*OPTIONAL
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LTC2951
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ABSOLUTE
AXI U RATI GS
(Note 1)
Supply Voltage (VIN) ..................................– 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
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
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
GND 1
KILLT 2
PB 3
VIN 4
9
8
INT
7
EN/EN
6
OFFT
5
KILL
8 KILL
7 OFFT
6 EN/EN
5 INT
VIN 1
PB 2
KILLT 3
GND 4
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
DDB8 PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 140°C/W
TJMAX = 125°C, θJA = 165°C/W
EXPOSED PAD (PIN 9) UNCONNECTED
ORDER PART
NUMBER
DDB PART*
MARKING
ORDER PART
NUMBER
TS8 PART*
MARKING
LTC2951CDDB-1
LTC2951CDDB-2
LTC2951IDDB-1
LTC2951IDDB-2
LBTB
LBTD
LBTB
LBTD
LTC2951CTS8-1
LTC2951CTS8-2
LTC2951ITS8-1
LTC2951ITS8-2
LTBTC
LTBTF
LTBTC
LTBTF
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
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
SYMBOL
VIN
IIN
VUVL
VUVL(HYST)
PARAMETER
Supply Voltage Range
VIN Supply Current
VIN Undervoltage Lockout
VIN Undervoltage Lockout Hysteresis
CONDITIONS
Steady State Operation
System Power On
VIN Falling
●
MIN
2.7
●
●
●
2.2
50
TYP
6
2.3
300
MAX
26.4
12
2.4
600
UNITS
V
µA
V
mV
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LTC2951
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
V⎯P⎯B(MIN, MAX)
⎯P⎯B Voltage Range
Single-Ended
●
–1
I⎯P⎯B
⎯P⎯B Input Current
2.5V < V⎯P⎯B < 26.4V
V⎯P⎯B = 1V
V⎯P⎯B = 0.6V
●
●
●
–1
–3
TYP
MAX
UNITS
26.4
V
–6
–9
±1
–12
–15
µA
µA
µA
Push Button Pin (⎯P⎯B)
V⎯P⎯B(VTH)
⎯P⎯B Input Threshold
⎯P⎯B Falling
●
0.6
0.8
1
V
V⎯P⎯B(VOC)
⎯P⎯B Open Circuit Voltage
I⎯P⎯B = –1µA
●
1
1.6
2
V
Timing Pins (KILLT, OFFT)
IKILLT, OFFT(PU)
KILLT/OFFT Pull Up Current
VKILLT, OFFT = 0V
●
–2.4
–3
–3.6
µA
IKILLT, OFFT(PD)
KILLT/OFFT Pull Down Current
VKILLT, OFFT = 1.3V
●
2.4
3
3.6
µA
tDB, ON
Turn On Debounce Time
⎯P⎯B Falling → Enable Asserted
●
100
128
163
ms
tDB, OFF
Internal Turn Off Debounce Time
OFFT Pin Float, ⎯P⎯B Falling → ⎯I⎯N⎯T Falling
●
26
32
41
ms
●
9
11.5
13.5
ms
±1
µA
0.11
0.4
V
0.63
V
tOFFT
Additional Adjustable Turn Off Time COFFT = 1500pF
µP Handshake Pins (⎯I⎯N⎯T, ⎯K⎯I⎯L⎯L)
I⎯I⎯N⎯T(LKG)
⎯I⎯N⎯T Leakage Current
V⎯ I⎯N⎯T = 3V
●
V⎯I⎯N⎯T(VOL)
⎯I⎯N⎯T Output Voltage Low
I⎯ I⎯N⎯T = 3mA
●
V⎯K⎯I⎯L⎯L(TH)
⎯K⎯I⎯L⎯L Input Threshold Voltage
⎯K⎯I⎯L⎯L Falling
●
0.57
0.6
●
10
30
V⎯K⎯I⎯L⎯L(HYST)
⎯K⎯I⎯L⎯L Input Threshold Hysteresis
I⎯K⎯I⎯L⎯L(LKG)
⎯K⎯I⎯L⎯L Leakage Current
t ⎯K⎯I⎯L⎯L(PW)
⎯K⎯I⎯L⎯L Minimum Pulse Width
t ⎯K⎯I⎯L⎯L(PD)
⎯K⎯I⎯L⎯L Propagation Delay
⎯K⎯I⎯L⎯L Falling → Enable Released
●
t ⎯K⎯I⎯L⎯L, ON BLANK
⎯K⎯I⎯L⎯L Turn On Blanking (Note 3)
⎯K⎯I⎯L⎯L = Low, Enable Asserted → Enable
Released
●
400
t ⎯K⎯I⎯L⎯L, OFF DELAY
Internal ⎯K⎯I⎯L⎯L Turn Off Delay
(Note 4)
KILLT Pin Float, ⎯K⎯I⎯L⎯L = High, ⎯I⎯N⎯T Asserted →
Enable Released
●
t ⎯K⎯I⎯L⎯L, OFF DELAY,
ADDITIONAL
Additional Adjustable ⎯K⎯I⎯L⎯L Turn Off CKILLT = 1500pF
Delay (Note 4)
tEN/⎯E⎯N, Lock Out
EN/⎯E⎯N Lock Out Time (Note 5)
IEN/⎯E⎯N(LKG)
EN/⎯E⎯N Leakage Current
VEN/⎯E⎯N(VOL)
EN/⎯E⎯N Voltage Output Low
●
V ⎯K⎯I⎯L⎯L = 0.6V
●
50
mV
±0.1
µA
30
µs
30
µs
512
650
ms
100
128
163
ms
●
9
11.5
13.5
ms
Enable Released → Enable Asserted
●
200
256
325
ms
VEN/ ⎯E⎯N = 1V, Sink Current Off
●
±0.1
µA
IEN/ ⎯E⎯N = 3mA
●
0.4
V
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 tDB, ON.
0.11
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
(CKILLT) 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
consistent powered down configuration. ⎯P⎯B is ignored during this lock out
time. This time delay does not include tDB, ON.
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LTC2951
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TYPICAL PERFOR A CE CHARACTERISTICS
10
10
TA = 25°C
8
VIN = 2.7V
4
2
160
tDB, ON (ms)
VIN = 3.3V
6
IVIN (µA)
6
4
2
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
0
100
0
5
10
15
20
25
10000
tDB, OFF + tOFFT (ms)
tDB, OFF (ms)
40
30
20
1000
100
10
0
20
25
10
30
1
100
10
OFFT EXTERNAL CAPACITOR (nF)
2951 G06
tKILL, OFF DELAY (ms)
160
120
80
40
0
5
10
15
VIN (V)
20
25
30
2951 G03
20
25
VIN = 26.4V
–3.0
VIN = 2.7V
–2.8
–25
0
25
50
TEMPERATURE (°C)
75
100
2951 G08
KILLT Pull-Down Current vs
Temperature
10000
–3.4
1000
100
10
30
–3.2
–2.6
–50
1000
KILLT PULL-DOWN CURRENT (µA)
TA = 25°C
15
VIN (V)
OFFT Pull-Down Current vs
Temperature
⎯K⎯I⎯L⎯L Turn Off Delay vs KILLT
External Capacitor
200
10
2951 G07
tKILL, OFF DELAY + tKILL, OFF DELAY, ADDITIONAL (ms)
Internal Default ⎯K⎯I⎯L⎯L Turn Off
Delay (t⎯K⎯I⎯L⎯L, OFF DELAY) vs VIN
0
5
–3.4
TA = 25°C
VIN = 3.3V
15
VIN (V)
0
2951 G14
Turn Off Debounce Time (tDB, OFF
+ tOFFT) vs OFFT External Capacitor
TA = 25°C
10
0
30
2951 G02
Internal Default Turn Off
Debounce Time (tDB, OFF) vs VIN
5
80
VIN (V)
2951 G01
0
120
40
OFFT PULL-DOWN CURRENT (µA)
IVIN (µA)
8
200
TA = 25°C
VIN = 26.4V
50
Turn On Debounce Time
(tDB, ON) vs VIN
Supply Current vs Supply Voltage
Supply Current vs Temperature
1
100
10
KILLT EXTERNAL CAPACITOR (nF)
1000
2951 G04
–3.2
VIN = 26.4V
–3.0
VIN = 2.7V
–2.8
–2.6
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2951 G05
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LTC2951
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TYPICAL PERFOR A CE CHARACTERISTICS
⎯P⎯B Voltage vs External ⎯P⎯B
Resistance to Ground
⎯P⎯B Current vs ⎯P⎯B Voltage
–250
300
TA = 25°C
VIN = 3.3V
VIN = 3.3V
250
PB VOLTAGE (mV)
PB CURRENT (µA)
–200
–150
–100
–50
0
–10
200
TA = 100°C
150
TA = 25°C
TA = –45°C
100
50
0
–5
0
5
10 15
PB VOLTAGE (V)
20
25
0
5
10
15
20
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
30
2951 G09
500
EN/⎯E⎯N VOL vs Current Load
1.0
EN (LTC2951-1) Voltage vs VIN
0.6
200
0.4
100
0.2
⎯E⎯N (LTC2951-2) Voltage vs VIN
TA = 25°C
100k PULL-UP FROM EN TO VIN
3
EN (V)
300
EN (V)
EN/EN VOLTAGE (mV)
0.8
4
TA = 25°C
100k PULL-UP FROM EN TO VIN
TA = 25°C
VIN = 3.3V
400
2951 G10
2
1
0
0
2
6
8
4
EN/EN CURRENT LOAD (mA)
10
0
0
0
1
2
3
4
2951 G11
0
1
2
3
4
VIN (V)
VIN (V)
2951 G12
2951 G13
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LTC2951
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PI FU CTIO S
(TSOT-23/DFN)
VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.
⎯ ⎯B (Pin 2/Pin 3): Push Button Input. Connecting ⎯P⎯B to
P
ground through a momentary switch provides on/off
control via the EN/⎯E⎯N pin. An internal 100k pull-up resistor connects to an internal 1.9V bias voltage. The rugged
⎯P⎯B input can be pulled up to 26.4V externally without
consuming extra current.
KILLT (Pin 3/Pin 2): Additional, Adjustable ⎯K⎯I⎯L⎯L Turn Off
Delay Input (t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL). A capacitor to
ground provides additional delay time (beyond the internal
default 128ms, t⎯K⎯I⎯L⎯L, OFF DELAY) from ⎯I⎯N⎯T falling to the
automatic release of the enable output. The ⎯K⎯I⎯L⎯L turn off
delay feature ensures the release of the enable pin under
system fault conditions, such as the µP not responding
to the LTC2951 interrupt signal (⎯I⎯N⎯T low).
GND (Pin 4/Pin 1): Device Ground.
I⎯ ⎯N⎯T (Pin 5/Pin 8): Open Drain Interrupt Output. After a
push button turn-off event is detected (tDB, OFF + tOFFT),
the LTC2951 interrupts the system (µP) by bringing the
⎯I⎯N⎯T pin low. Once the system finishes its power down
and housekeeping tasks, it sets ⎯K⎯I⎯L⎯L low, which in turn
releases the enable output. If at the end of the power
down timer period (t⎯K⎯I⎯L⎯L, OFF DELAY + t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL) ⎯K⎯I⎯L⎯L is still high, the enable output is released
immediately. ⎯I⎯N⎯T may optionally be tied to ⎯K⎯I⎯L⎯L to release
the enable output immediately after the turn-off event has
been detected (⎯I⎯N⎯T low).
EN (LTC2951-1, Pin 6/Pin 7): Open Drain Enable Output.
This pin is intended to enable system power. EN goes high
after a valid ⎯P⎯B turn on event (tDB, ON). EN goes low if: a)
⎯ ⎯I⎯L⎯L is not driven high within 512ms of the initial valid ⎯P⎯B
K
power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low during normal
operation, or c) a second valid ⎯P⎯B event (power turn-off)
is detected. The operating range for this pin is 0V to 10V.
A 100k pull-up is recommended if not available in the
DC/DC converter.
⎯E⎯N (LTC2951-2, Pin 6/Pin 7): Open Drain Enable Output.
This pin is intended to enable system power. ⎯E⎯N is asserted
low after a valid ⎯P⎯B turn-on event (tDB, ON). ⎯E⎯N releases
high if: a) ⎯K⎯I⎯L⎯L is not driven high within 512ms of the
initial valid ⎯P⎯B power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low
during normal operation, or c) a second valid ⎯P⎯B event
(power turn-off) is detected. The operating range of this
pin is 0V to 10V. A 100k pull-up is recommended if not
available in the DC/DC converter.
OFFT (Pin 7/Pin 6): Additional Adjustable Turn Off Time
Input (tOFFT). A capacitor to ground determines the additional time (beyond the internal default 32ms, tDB, OFF)
that the ⎯P⎯B pin must be held low before initiating a power
down sequence (⎯I⎯N⎯T falling). Floating this pin results in a
default turn off debounce time of 32ms.
⎯ ⎯I⎯L⎯L (Pin 8/Pin 5): ⎯K⎯I⎯L⎯L Input. Forcing ⎯K⎯I⎯L⎯L low releases
K
the enable output. During system turn on, this pin is blanked
by a 512ms internal timer (t⎯K⎯I⎯L⎯L, ON BLANK) to allow the
system to pull ⎯K⎯I⎯L⎯L high. This pin has an accurate 0.6V
threshold and can be used as a voltage monitor input.
Exposed Pad (Pin 9): Exposed Pad may be left open or
connected to device ground.
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LTC2951
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BLOCK DIAGRA
EN/EN
VIN
2.7V TO 26.4V
REGULATOR
2.4V
2.4V
OSCILLATOR
KILL
100k
LOGIC
PB
DEBOUNCE
0.6V
0.8V
INT
OSCILLATOR
GND
2951 BD
KILLT
OFFT
W
UW
TI I G DIAGRA S
tKILL(PW)
KILL
tKILL(PD)
EN/EN
2951 TD01
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LTC2951
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UW
TI I G DIAGRA S
PB
PB & KILL IGNORED
tKILL, ON BLANK
tDB, ON
EN
(LTC2951-1)
EN
(LTC2951-2)
2951 TD02
Power On Timing
PB
PB IGNORED
tDB, OFF
tOFFT
OFFT
16 CYCLES
INT
tKILL, OFF DELAY
tKILL, OFF DELAY, ADDITIONAL
KILLT
16 CYCLES
EN
(LTC2951-1)
EN
(LTC2951-2)
2951 TD03
Power Off Timing, ⎯K⎯I⎯L⎯L > 0.6V
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LTC2951
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APPLICATIO S I FOR ATIO
Description
⎯K⎯I⎯L⎯L Turn Off Delay
The LTC2951 is a low power (6µA), wide input voltage range
(2.7V to 26.4V), push button On/Off controller that can
interface to a µP and a power supply. The part incorporates
all the flexible timing needed to debounce the push button
input (⎯P⎯B). The LTC2951 also provides a simple interface
(⎯I⎯N⎯T output, ⎯K⎯I⎯L⎯L input) to allow a system to power on and
power off in a controlled manner. The wide input voltage
range allows a system designer to operate from single cell
to multi-cell battery stacks. Very low quiescent current
makes the LTC2951 ideal for continuously monitoring the
On/Off push button of a handheld device.
The LTC2951 provides a failsafe feature that allows the
user to turn off system power (via ⎯P⎯B) under system fault
conditions. During a normal power down sequence, the
LTC2951 first interrupts the µP by setting ⎯I⎯N⎯T low. The
µP then performs power down and housekeeping tasks
and drives ⎯K⎯I⎯L⎯L low when done. The LTC2951 releases the
enable output, thus turning off system power. The ⎯K⎯I⎯L⎯L
turn off timer starts when ⎯I⎯N⎯T is driven low. If the µP fails
to respond during this timeout period, the enable output
will automatically release. The default power down timeout
period is 128ms (t⎯K⎯I⎯L⎯L, OFF DELAY), which can be extended
by placing an optional capacitor on the KILLT pin (t⎯K⎯I⎯L⎯L,
OFF DELAY, ADDITIONAL). The following equation describes
the additional power down timeout period. CKILLT is the
KILLT external capacitor:
Turn On
When power is first applied to the LTC2951, the part initializes the output pins. Any DC/DC converters connected to
the EN/⎯E⎯N pin will therefore be off. To assert the enable
output, ⎯P⎯B must be held low for a minimum of 128ms
(tDB, ON).
Once the enable output is asserted, any DC/DC converters
connected to this pin are turned on. The ⎯K⎯I⎯L⎯L input from
the µP is ignored during the succeeding 512ms blanking
time (t ⎯K⎯I⎯L⎯L, ON BLANK). This blanking time represents the
maximum time required to power up the DC/DC converter
and the µP. If ⎯K⎯I⎯L⎯L is not brought high during this 512ms
time window, the enable output is released. The assumption is that 512ms is sufficient time for the system to
power up.
Turn Off
To initiate a power off sequence, ⎯P⎯B must be held low for a
minimum of 32ms (tDB, OFF). Additional turn off debounce
time may be added via an optional capacitor connected to
the OFFT pin (tOFFT). The following equation describes the
additional time that ⎯P⎯B must be held low to initiate a power
off sequence. COFFT is the OFFT external capacitor:
COFFT = 1.56E-4 [μF/ms] • (tOFFT – 1ms)
Once ⎯P⎯B has been validly pressed, ⎯I⎯N⎯T is switched low.
This alerts the µP to perform its power down and housekeeping tasks.
CKILLT = 1.56e-4 [µF/ms] • (tK⎯ I⎯ L⎯ L⎯ , OFF DELAY, ADDITIONAL – 1ms)
Note that ⎯K⎯I⎯L⎯L can be driven low (thereby releasing the
enable output) at any time after t⎯K⎯I⎯L⎯L, ON BLANK period.
Simplified Power On/Off Sequence
Figure 1 shows a simplified LTC2951-1 power on and power
off sequence. A high to low transition on ⎯P⎯B (t1) initiates
the power on sequence. This diagram does not show any
bounce on ⎯P⎯B. In order to assert the enable output, the ⎯P⎯B
pin must stay low continuously (⎯P⎯B high resets timers) for
128ms (t2–t1). Once EN goes high (t2), an internal 512ms
blanking timer is started. This blanking timer is designed
to give sufficient time for the DC/DC converter to reach its
final voltage, and to allow the µP enough time to perform
power on tasks.
The ⎯K⎯I⎯L⎯L pin must be pulled high within 512ms of the
EN pin going high. Failure to do so results in the EN
pin going low 512ms after it went high. (EN = low, see
Figure 2). Note that the LTC2951 does not sample ⎯K⎯I⎯L⎯L
and ⎯P⎯B until after the 512ms internal timer has expired.
The reason ⎯P⎯B is ignored is to ensure that the system
is not forced off while powering on. Once the 512ms
timer expires (t4), the release of the ⎯P⎯B pin is then
debounced with an internal 32ms timer. The system has
now properly powered on and the LTC2951 monitors ⎯P⎯B
2951f
9
LTC2951
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APPLICATIO S I FOR ATIO
t1
t2
PB
t3
t4
t5
t6
PB & KILL IGNORED
tDB, ON
t7
PB IGNORED
tKILL, ON BLANK
< tKILL,
OFF DELAY
tDB, OFF
tOFFT
OFFT
INT
KILL
EN
2951 F01
Figure 1. Simplified Power On/Off Sequence for LTC2951-1
tABORT
PB
tDB, ON
512ms
INTERNAL
TIMER
POWER ON
TIMING
POWER
TURNED OFF
EN
µP FAILED TO SET
KILL HIGH
KILL
2951 F02
Figure 2. Aborted Power On Sequence for LTC2951-1
2951f
10
LTC2951
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APPLICATIO S I FOR ATIO
and ⎯K⎯I⎯L⎯L (for a turnoff command) while consuming only
6µA of supply current.
A high to low transition on ⎯P⎯B (t5) initiates the power
off sequence. ⎯P⎯B must stay low continuously (⎯P⎯B high
resets debounce timer) for a period controlled by the
default 32ms and the external OFFT capacitor (t6–t5). At
the completion of the OFFT timing (t6), an interrupt (⎯I⎯N⎯T)
is set, signifying that EN will be switched low after the
⎯K⎯I⎯L⎯L turn off (t ⎯K⎯I⎯L⎯L, OFF DELAY + t ⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL)
timeout period. Once a system has finished performing
its power down operations, it can set ⎯K⎯I⎯L⎯L low (t7) and
thus immediately set EN low, terminating the ⎯K⎯I⎯L⎯L turn off
timer. The release of the ⎯P⎯B pin is then debounced with
an internal 32ms timer.
The system is now in its reset state: where the LTC2951
is in low power mode (6µA). ⎯P⎯B is monitored for a high
to low transition.
Aborted Power On Sequence
The power on sequence is aborted when the ⎯K⎯I⎯L⎯L remains
low after the end of the 512ms blanking time. Figure 2 is
a simplified version of an aborted power on sequence.
At time tABORT, since ⎯K⎯I⎯L⎯L is still low, EN pulls low (thus
turning off the DC/DC converter).
µP Turns Off Power During Normal Operation
Once the system has powered on and is operating normally, the µP can turn off power by setting ⎯K⎯I⎯L⎯L low, as
shown in Figure 3. At time t ⎯K⎯I⎯L⎯L, ⎯K⎯I⎯L⎯L is set low by the
µP. 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 significant 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 ⎯P⎯B) to restart
the converter. This condition guarantees that the µP has
always powered down completely before it is restarted.
Figure 4 shows the µP turning power off. After a low on
⎯K⎯I⎯L⎯L releases enable, ⎯P⎯B is ignored during the internal
256ms timer period. This is shown as tEN/⎯E⎯N, LOCKOUT in
Figure 4.
LTC2951-1, LTC2951-2 Versions
The LTC2951-1 (high true EN) and LTC2951-2 (low true
⎯E⎯N) differ only by the polarity of the EN/⎯E⎯N pin. Both versions allow the user to extend the amount of time that the
⎯P⎯B must be held low in order to begin a valid power off
sequence. An external capacitor placed on the OFFT pin
adds additional time to the turn off debounce time. If no
capacitor is placed on the OFFT pin, then the turn off debounce time is given by an internally fixed 32ms timer.
Both versions of the LTC2951 provide extendable ⎯K⎯I⎯L⎯L
turn off timer, t ⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL, by connecting
an optional external capacitor on the KILLT pin. The default
⎯K⎯I⎯L⎯L turn off delay time is 128ms, t ⎯K⎯I⎯L⎯L, OFF DELAY.
tEN/EN, LOCKOUT
PB
POWER ON
tKILL
PB
PB & KILL IGNORED
DC/DC
TURNS OFF
PB & KILL IGNORED
PB BLANKING
PB IGNORED
256ms
DC/DC
TURNS OFF
EN
EN
µP SETS
KILL LOW
KILL
µP SETS
KILL LOW
XXX DON’T CARE
KILL
XXX DON’T CARE
2951 F04
2951 F03
Figure 3. µP Turns Off Power (LTC2951-1)
Figure 4. DC/DC Turn Off Blanking (LTC2951-1)
2951f
11
LTC2951
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APPLICATIO S I FOR ATIO
High Voltage Pins
The VIN and ⎯P⎯B pins can operate at voltages up to 26.4V.
⎯P⎯B can, additionally, operate below ground (–6V) without
⎯ B
⎯ has an ESD HBM rating of ±10kV.
latching up the device. P
If the push button switch connected to ⎯P⎯B exhibits high
leakage current, then an external pull-up resistor to VIN is
recommended. Furthermore, if the push button switch is
physically located far from the LTC2951 ⎯P⎯B pin, parasitic
capacitances may couple onto the high impedance ⎯P⎯B
input. Additionally, parasitic series inductance may cause
unpredictable ringing at the ⎯P⎯B pin. Placing a 5k resistor
from the ⎯P⎯B pin to the push button switch would mitigate
parasitic inductance problems. Placing a 0.1µF capacitor
on the ⎯P⎯B pin would lessen the impact of parasitic capacitive coupling.
U
TYPICAL APPLICATIO S
Voltage Monitoring with ⎯K⎯I⎯L⎯L Input
The ⎯K⎯I⎯L⎯L pin can be used as a voltage monitor. Figure
5 shows an application where the ⎯K⎯I⎯L⎯L pin has a dual
function. It is driven by a low leakage open drain output
of the µP. It is also connected to a resistor divider that
monitors battery voltage (VIN). When the battery voltage
falls below the set value, the voltage at the ⎯K⎯I⎯L⎯L pin falls
below 0.6V and the EN pin is quickly pulled low. Note that
the resistor values should be as large as possible, but
small enough to keep leakage currents from tripping the
0.6V ⎯K⎯I⎯L⎯L comparator.
The DC/DC converter shown has an internal pull-up current on its ⎯S⎯H⎯D⎯N pin. A pull-up resistor on EN is thus not
needed.
Operation Without µP
Figure 6 shows how to connect the ⎯K⎯I⎯L⎯L pin when there
is no circuitry available to drive it. The minimum pulse
width detected is 30µs. If there are glitches on the resistor pull-up voltage that are wider than 30µs and transition
below 0.6V, then an appropriate bypass capacitor should
be connected to the ⎯K⎯I⎯L⎯L pin.
VIN
VIN
9V
9V
VIN
VIN
3.3V
VOUT
LT1767-3.3
LT1767-3.3
SHDN
SHDN
5.4V THRESHOLD
C4
0.1µF
3.3V
VOUT
R3
806k
1%
VIN
EN
LTC2951-1
R2
100k
1%
R1
100k
R1
10k
INT
INT
PB
KILL
GND KILLT
OFFT
C4
0.1µF
VIN
EN
LTC2951-1
INT
+
µP
KILL
(OPEN DRAIN)
PB
KILL
GND KILLT
OFFT
C3*
0.01µF
2951 F05
CKILLT*
0.033µF
CKILLT*
0.033µF
COFFT*
0.033µF
*OPTIONAL
Figure 5. Input Voltage Monitoring with ⎯K⎯I⎯L⎯L Input
COFFT*
0.033µF
*OPTIONAL
2951 F06
Figure 6. No µP Application
2951f
12
LTC2951
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TYPICAL APPLICATIO S
Power Path Switching
⎯P⎯B Pin in a Noisy Environment
The ⎯E⎯N open drain output of the LTC2951-2 is designed to
switch on/off an external power PFET. This allows a user
to connect/disconnect a power supply (or battery) to its
load by toggling the ⎯P⎯B pin. Figure 7 shows the LTC2951-2
controlling a two cell Li-Ion battery application. The ⎯I⎯N⎯T
and ⎯K⎯I⎯L⎯L pins are connected to the output of the PFET
through a resistor divider. The ⎯K⎯I⎯L⎯L pin serves as a voltage
monitor. When VOUT drops below 6V, the ⎯E⎯N pin is open
circuited 30µs later.
The rugged ⎯P⎯B pin is designed to operate in noisy environments. Transients below ground (>–6V) and above VIN
⎯ ⎯B pin. Additionally,
(<33V) will not damage the rugged P
⎯
⎯
the PB pin can withstand ESD HBM strikes up to ±10kV.
In order to keep external noise from coupling inside the
⎯ ⎯B pin. A
LTC2951, place an R-C network close to the P
5k resistor and a 0.1µF capacitor should suffice for most
noisy applications (see Figure 8).
VOUT
M1
R5
100K
4.2V
SINGLE CELL
Li-Ion BATTERY
R1
909k
1%
+
C4
0.1µF
CERAMIC
4.2V
SINGLE CELL
Li-Ion BATTERY
VOUT,TRIP POINT = 6V
+
VIN
EN
LTC2951-2
INT
PB
KILL
GND KILLT
OFFT
CKILLT*
0.033µF
OPEN DRAIN OUTPUT
OPTIONAL GLITCH
FILTER CAPACITOR
VTH = 0.6V INPUT
R4
100k
1%
C3*
0.1µF
COFFT*
0.033µF
*OPTIONAL
2951 F07
Figure 7. Power Path Control with 6V Under Voltage Detect
VIN
PARASITICS
TRACE
CAPACITANCE
R6
5k
EN
VIN
PB
LTC2951-1
INT
KILLT
OFFT
NOISE
TRACE
INDUCTANCE
C5
0.1µF
KILL
GND
DETAILS OMITTED
FOR CLARITY
2951 F08
Figure 8. Filtering for Noisy ⎯P⎯B Traces
2951f
13
LTC2951
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TYPICAL APPLICATIO S
External Pull-Up Resistor on ⎯P⎯B
Reverse Battery Protection
⎯ ⎯B pin makes an exAn internal pull-up resistor on the P
ternal pull-up resistor unnecessary. Leakage current on
⎯ ⎯B board trace, however, will affect the open circuit
the P
voltage on the ⎯P⎯B pin. If the leakage is too large (>2µA),
the ⎯P⎯B voltage may fall close to the threshold window.
To mitigate the effect of the board leakage, a 10k resistor
to VIN is recommended (see Figure 9).
To protect the LTC2951 from a reverse battery connection, place a 1k resistor (R8) in series with the VIN pin
(see Figure 10).
VIN
VIN
LTC2951-1/
LTC2951-2
2.4V
R7
10k
100k
PB
EXTERNAL BOARD
LEAKAGE CURRENT
>2µA
GND
PINS OMITTED
FOR CLARITY
2951 F09
IF EXTERNAL PARASITIC BOARD
LEAKAGE >2µA, USE EXTERNAL
PULL-UP RESISTOR
Figure 9. External Pull-Up Resistor on ⎯P⎯B Pin
2951f
14
LTC2951
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PACKAGE DESCRIPTIO
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702)
0.61 ±0.05
(2 SIDES)
R = 0.115
TYP
5
0.56 ± 0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
0.675 ±0.05
2.50 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
8
2.00 ±0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
4
0.25 ± 0.05
0.75 ±0.05
0.200 REF
0.50 BSC
2.20 ±0.05
(2 SIDES)
0.38 ± 0.10
(DDB8) DFN 1103
0.50 BSC
2.15 ±0.05
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1
PIN 1
CHAMFER OF
EXPOSED PAD
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637)
0.52
MAX
2.90 BSC
(NOTE 4)
0.65
REF
1.22 REF
1.4 MIN
3.85 MAX 2.62 REF
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.22 – 0.36
8 PLCS (NOTE 3)
0.65 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
1.95 BSC
TS8 TSOT-23 0802
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
2951f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC2951
U
TYPICAL APPLICATIO
VIN
9V
BATTERY
+
R5
910k
R8
1k
VOUT
LT1761-1.8
SHDN
1.8V
C4
0.1µF
VIN
R1
10k
EN
LTC2951-1
INT
INT
PB
KILL
KILL
GND KILLT
OFFT
µP
CKILLT*
0.033µF
COFFT*
0.033µF
*OPTIONAL
2951 F10
Figure 10. Reverse Battery Protection Using R8
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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Adjustable ⎯R⎯E⎯S⎯E⎯T and Tolerance, 8-Lead SOT-23 and 3mm × 2mm DFN Packages
LTC2950
Micropower Push Button On/Off Controller
High Voltage Push Button Controller with µP Interface and Adjustable ON Time
LTC4411
2.6A Low Loss Ideal Diode in ThinSOT
No External MOSFET, Automatic Switching Between DC Sources
LTC4412HV
Power Path Controller in ThinSOT
Efficient Diode-ORing, Automatic Switching Between DC Sources, 3V to 36V
LTC4055
USB Power Controller and Li-Ion Charger
Automatic Switchover, Charges 1-Cell Li-Ion Batteries
2951f
16 Linear Technology Corporation
LT/TP 0405 500 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
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