LTC2953
Push Button
On/Off Controller
with Voltage Monitoring
DESCRIPTION
FEATURES
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Wide Operating Voltage Range: 2.7V to 27V
Push Button Control of System Power
Low Supply Current: 14μA
Power Fail Comparator Generates Warning
UVLO Comparator Gracefully Latches Power Off
Adjustable Supply Monitor with 200ms Reset
Adjustable Power Down Timer
Low Leakage EN Output (LTC2953-1) Allows DC/DC
Converter Control
High Voltage ⎯E⎯N Output (LTC2953-2) Allows Circuit
Breaker Control
Simple Interface Allows Orderly System Power Up
and Power Down
±1.5% Threshold Tolerances
±10kV ESD HBM on ⎯P⎯B Input
12-Pin 3mm × 3mm DFN
The LTC®2953 is a push button On/Off controller that
manages system power via a push button interface. An
enable output toggles system power while an interrupt
output provides debounced push button status. The interrupt output can be used in menu driven applications to
request a system power down.
The LTC2953 also features input and output power supply monitors. An uncommitted power fail comparator
provides real time input monitor information, while a
de-glitched under voltage lockout comparator gracefully
initiates a system power down. The under voltage lockout
comparator prevents the system from powering from a
low power supply.
The adjustable supply monitor input is compared against
an accurate internal 0.5V reference. The reset output
remains low until the supply monitor input has been in
compliance for 200ms.
APPLICATIONS
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Push Button Power Path Control
Battery Power Supervisor
Portable Instrumentation, PDA
Blade Servers
Desktop and Notebook Computers
The LTC2953 operates over a wide 2.7V to 27V input
voltage range and draws only 14μA of current. Two versions of the part accommodate either positive or negative
enable polarities.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
VIN
+
8.4V
100k
2150k
UVLO
23.2k
VIN
DC/DC
3.3V
SHDN
EN
499k
LTC2953-1
PFI
Push Button On/Off Control with Interrupt
VOUT
TURN ON PULSE
SHORT
INTERRUPT PULSE
LONG
TURN OFF PULSE
PB
100k
VM
EN
100k
TURNS ON
STAYS ON
TURNS OFF
100k
196k
100k
ON/OFF
PB
RST
PFO
INT
KILL
GND
PDT
RST
GPIO
INT SYSTEM
LOGIC
KILL
1μF
INT
INTERRUPT
INTERRUPT
2954 TD01b
2953 TA01
tPDT = 6.4 SECONDS
2953f
1
LTC2953
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Supply Voltage (VIN) .................................. –0.3V to 33V
Input Voltages
⎯P⎯B, ⎯P⎯F⎯I, UVLO........................................... –6V to 33V
VM ......................................................... –0.3V to 20V
⎯K⎯I⎯L⎯L ....................................................... –0.3V to 10V
PDT....................................................... –0.3V to 2.7V
Output Voltages
EN/⎯E⎯N, ⎯P⎯F⎯O ............................................ –0.3V to 50V
⎯R⎯S⎯T, ⎯I⎯N⎯T ................................................ –0.3V to 10V
Operating Temperature Range
LTC2953C ................................................ 0°C to 70°C
LTC2953I ............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
TOP VIEW
GND
1
12 INT
VM
2
11 EN/EN
KILL
3
PDT
4
PB
5
8 PFI
VIN
6
7 UVLO
10 RST
13
9 PFO
DD PACKAGE
12-LEAD (3mm ´ 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 43°C/W
EXPOSED PAD (PIN 13) PCB GROUND CONNECTION OPTIONAL
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2953CDD-1#PBF
LTC2953CDD-2#PBF
LTC2953IDD-1#PBF
LTC2953IDD-2#PBF
LTC2953CDD-1#TRPBF
LTC2953CDD-2#TRPBF
LTC2953IDD-1#TRPBF
LTC2953IDD-2#TRPBF
LCWT
LCQT
LCWT
LCQT
12-Lead (3mm × 3mm) Plastic DFN
12-Lead (3mm × 3mm) Plastic DFN
12-Lead (3mm × 3mm) Plastic DFN
12-Lead (3mm × 3mm) Plastic DFN
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.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
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 27V, unless otherwise noted (Note 2).
SYMBOL
PARAMETER
CONDITIONS
MIN
Supply Voltage Range
Steady State Operation
●
TYP
MAX
UNITS
Supply Pin (VIN)
VIN
2.7
IIN
VIN Supply Current
VIN = 2.7V to 27V
●
VUVL
VIN Undervoltage Lockout
VIN Falling
●
2.2
27
V
14
26
μA
2.3
2.5
V
27
V
Push Button, Enable (⎯P⎯B, EN/⎯E⎯N)
VPB(MIN, MAX)
⎯P⎯B Operating Voltage Range
Single-Ended
●
–1
IPB
⎯P⎯B Input Current
2.5V < VPB < 27V
VPB = 1V
VPB = 0.6V
●
●
●
–1
–3
–6
–9
±1
–12
–15
μA
μA
μA
VPB(VTH)
⎯P⎯B Input Threshold
⎯P⎯B Falling
●
0.6
0.8
1
V
VPB(VOC)
⎯P⎯B Open Circuit Voltage
IPB = –1μA
●
1
1.6
2
V
2953f
2
LTC2953
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 27V, unless otherwise noted (Note 2).
SYMBOL
PARAMETER
CONDITIONS
MIN
IEN(LKG)
EN/⎯E⎯N Leakage Current
VEN/ ⎯E⎯N = 1V, Sink Current Off
VEN/ ⎯E⎯N = 40V, Sink Current Off
●
●
VEN(VOL)
EN/⎯E⎯N Voltage Output Low
IEN/ ⎯E⎯N = 500μA
●
tEN, Lock Out
EN/⎯E⎯N Lock Out Time (Note 3)
Enable Released → Enable Asserted
●
TYP
MAX
UNITS
±0.1
±1
μA
μA
0.11
0.4
V
52
64
82
ms
On/Off Timing Pins (⎯P⎯B, UVLO, PDT, ⎯I⎯N⎯T)
tDB, ON
Turn On Debounce Time
⎯P⎯B Falling → Enable Asserted
●
26
32
41
ms
IPDT(PU)
PDT Pull Up Current
VPDT = 0V
●
–2.4
–3
–3.6
μA
IPDT(PD)
PDT Pull Down Current
VPDT = 1.3V
●
2.4
3
3.6
μA
tDB, OFF
Turn Off Interrupt Debounce Time
⎯P⎯B, UVLO Falling → ⎯I⎯N⎯T Falling
●
26
32
41
ms
tPD, Min
Internal ⎯P⎯B Power Down Delay
Time (Note 4)
⎯P⎯B, UVLO Falling → Enable Released
PDT Open
●
52
64
82
ms
tPDT
Additional Adjustable ⎯P⎯B Power
Down Delay Time
CPDT = 1500pF
●
9
11.5
13.5
ms
tINT, Min
Minimum ⎯I⎯N⎯T Pulse Width
⎯I⎯N⎯T Asserted → ⎯I⎯N⎯T Released
●
26
32
41
ms
tINT, Max
Maximum ⎯I⎯N⎯T Pulse Width
CPDT = 1500pF, ⎯I⎯N⎯T Asserted → ⎯I⎯N⎯T Released
●
35
43.5
54.5
ms
⎯K⎯I⎯L⎯L Falling
●
0.57
0.6
0.63
V
●
10
30
50
mV
●
30
30
μs
650
ms
μP Handshake Pins (⎯K⎯I⎯L⎯L, ⎯I⎯N⎯T)
VKILL(TH)
⎯K⎯I⎯L⎯L Input Threshold Voltage
VKILL(HYST)
⎯K⎯I⎯L⎯L Input Threshold Hysteresis
t KILL(PW)
⎯K⎯I⎯L⎯L Minimum Pulse Width
tKILL(PD)
⎯K⎯I⎯L⎯L Propagation Delay
⎯K⎯I⎯L⎯L Falling → Enable Released
●
tKILL, ON BLANK
⎯K⎯I⎯L⎯L Turn On Blanking (Note 5)
⎯K⎯I⎯L⎯L = Low, Enable Asserted → Enable Released
●
IKILL(LKG)
⎯K⎯I⎯L⎯L Leakage Current
VKILL = 0.6V
●
±0.1
μA
IINT(LKG)
⎯I⎯N⎯T Leakage Current
VINT = 3V
●
±0.1
μA
VINT(VOL)
⎯I⎯N⎯T Output Voltage Low
IINT = 3mA
●
0.11
0.4
V
400
μs
512
Power Fail and Voltage Monitor Pins (⎯P⎯F⎯I, ⎯P⎯F⎯O, UVLO, VM, ⎯R⎯S⎯T)
VPFI(TH)
⎯P⎯F⎯I Input Threshold Voltage
Falling
●
492
500
508
mV
VUVLO(TH)
UVLO Input Threshold Voltage
Falling
●
492
500
508
mV
VM(TH)
Adjustable Reset Threshold
Falling/Rising
●
492
500
508
mV
ΔVTH
⎯P⎯F⎯I-UVLO Threshold Mismatch
●
–5
0
5
mV
VPFI(HYST)
⎯P⎯F⎯I Input Hysteresis
●
2
4
10
mV
VUVLO(HYST)
UVLO Input Hysteresis
●
30
50
70
mV
VPFO(VOL)
⎯P⎯F⎯O Output Voltage Low
IPFO = 500μA
●
0.11
0.4
V
VRST(VOL)
⎯R⎯S⎯T Output Voltage Low
I = 3mA
●
0.11
0.4
V
2953f
3
LTC2953
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 27V, unless otherwise noted (Note 2).
SYMBOL
PARAMETER
CONDITIONS
IPFI(LKG)
⎯P⎯F⎯I Leakage Current
VPFI = 0.5V
VPFI = 27V
IPFO(LKG)
⎯P⎯FO Leakage Current
IUVLO(LKG)
MIN
TYP
MAX
UNITS
●
2
±10
±1
nA
μA
VPFO = 1V
VPFO = 40V
●
2
±10
±1
nA
μA
UVLO Leakage Current
VUVLO = 0.5V
VUVLO = 27V
●
2
±10
±1
nA
μA
IVM(LKG)
VM Input Leakage Current
VM = 0.5V
●
2
±10
nA
IRST(LKG)
⎯R⎯S⎯T Output Leakage Current
VRST = 3V
●
±0.1
μA
tPFI
⎯P⎯F⎯I Delay to ⎯P⎯F⎯O
100
200
μs
tRST
Reset Timeout Period
200
260
ms
tuv
VM Under Voltage Detect to ⎯R⎯S⎯T
VM Less Than VM(TH) By More Than 1%
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 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.
●
40
●
140
250
μs
Note 4: To manually force a release of the EN/⎯E⎯N pin, either ⎯P⎯B or UVLO
must be held low for at least tPD, Min (internal default power down timer) +
tPDT (adjustable by placing external capacitor at PDT pin).
Note 5: The ⎯K⎯I⎯L⎯L turn on blanking timer period (tKILL, ON BLANK) is the
waiting period immediately after 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, ⎯P⎯B and UVLO inputs are ignored during this
period. If ⎯K⎯I⎯L⎯L remains low at the end of this blanking period, the enable
output is released, thus turning off system power.
2953f
4
LTC2953
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
Turn On Debounce Time (tDB, ON)
vs VIN
Supply Current vs Supply Voltage
20
50
20
TA = 25°C
TA = 25°C
VIN = 27V
18
40
VIN = 2.7V
tDB, ON (ms)
IVIN (μA)
IVIN (μA)
VIN = 3.3V
15
16
14
30
20
10
12
5
–50
–25
0
25
50
TEMPERATURE (°C)
75
10
0
10
100
0
5
10
20
15
VIN (V)
25
30
2953 G01
35
10000
50
TA = 25°C
–3.4
TA = 25°C
VIN = 3.3V
tPD,MIN + tPDT (ms)
tDB, OFF (ms)
1000
100
10
10
0
5
10
15
VIN (V)
20
25
1
30
10
100
PDT EXTERNAL CAPACITANCE (nF)
PDT Pull-Up Current vs
Temperature
–300
30
VIN = 3.3V
–3.0
–2.8
–2.6
–50
1000
–25
0
25
50
TEMPERATURE (°C)
75
100
2953 G06
⎯P⎯B Voltage vs External ⎯P⎯B
Resistance to Ground
300
TA = 25°C
VIN = 3.3V
–250
VIN = 3.3V
250
3.2
3.0
PB VOLTAGE (mV)
TA = 100°C
PB CURRENT (μA)
PDT PULL-UP CURRENT (μA)
25
–3.2
⎯P⎯B Current vs ⎯P⎯B Voltage
VIN = 3.3V
–200
–150
–100
200
150
100
2.8
–50
2.6
–50
20
2953 G04
3.4
15
VIN (V)
PDT Pull-Down Current vs
Temperature
40
0
10
2953 G03
PDT PULL-DOWN CURRENT (μA)
Turn Off Interrupt Debounce Time
(tDB, OFF) vs VIN
20
5
2953 G02
Forced Power Down Delay Time
(tPD, MIN + tPDT) vs PDT External
Capacitance
30
0
–25
0
25
50
TEMPERATURE (°C)
75
100
2953 G07
0
–10
TA = –45°C
TA = 25°C
50
0
0
10
20
PB VOLTAGE (V)
30
0
5
10
15
20
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
2953f
5
LTC2953
TYPICAL PERFORMANCE CHARACTERISTICS
⎯E⎯N (LTC2953-2) Voltage vs VIN
EN (LTC2953-1) Voltage vs VIN
4
1.0
3
2
0.4
1
0
2
1
0
3
4
0
1
2
3
0
4
0
0.5
1.0
1.5
VIN (V)
VIN (V)
2.0 2.5
VIN (V)
2953 G11
⎯R⎯S⎯T Voltage vs VIN
3.0
3.5
4.0
2953 G12
⎯R⎯S⎯T, ⎯I⎯N⎯T VOL vs Current Load
600
4
2
1
0.2
0
TA = 25°C
PFI = 1V
100k PULL-UP FROM PFO TO VIN
3
PFO (V)
0.6
EN (V)
EN (V)
4
TA = 25°C
100k PULL-UP FROM EN TO VIN
TA = 25°C
100k PULL-UP FROM EN TO VIN
0.8
⎯P⎯F⎯O Voltage vs VIN
TA = 25°C
VM = 1V
100k PULL-UP FROM RST TO VIN
TA = 25°C
VIN = 3.3V
500
RST, INT VOL (mV)
RST (V)
3
2
400
300
200
1
100
0
0
0
0.5
1.0
1.5
2.0 2.5
VIN (V)
3.0
3.5
0
4.0
2953 G14
2953 G13
Threshold Voltage (VM, ⎯P⎯F⎯I,
UVLO) vs Temperature
504
EN/⎯E⎯N, ⎯P⎯F⎯O VOL vs Current Load
800
VIN = 3.3V
TA = 25°C
VIN = 3.3V
EN/EN, PFO VOL (mV)
THRESHOLD (mV)
502
500
498
496
–50
10
2
4
6
8
RST, INT CURRENT LOAD (mA)
600
400
200
0
–25
0
25
50
TEMPERATURE (°C)
75
100
2953 G15
0
0.5
2
2.5
1
1.5
EN/EN, PFO CURRENT LOAD (mA)
3
2953 G16
2953f
6
LTC2953
PIN FUNCTIONS
GND (Pin 1): Ground.
VM (Pin 2): Voltage Monitor Input. Input to an accurate
comparator with a 0.5V threshold. VM controls the state
of the ⎯R⎯S⎯T output pin and is independent of ⎯P⎯B, ⎯P⎯F⎯I and
UVLO status. A voltage below 0.5V on this pin asserts
⎯R⎯S⎯T low. Connect to GND if unused.
⎯K⎯I⎯L⎯L (Pin 3): ⎯K⎯I⎯L⎯L Input. Forcing ⎯K⎯I⎯L⎯L low releases the
enable output. During system turn on, this pin is blanked
by a 512ms internal timer (tKILL, 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 power kill voltage monitor.
Set the pin voltage above its threshold if unused.
of hysteresis. PFI controls the state of the ⎯P⎯F⎯O output pin
and is independent of ⎯P⎯B, VM and UVLO status. Connect
to GND if unused.
⎯P⎯F⎯O (Pin 9): Power Fail Output. This pin is a high voltage
open drain pull-down. ⎯P⎯F⎯O pulls low when PFI is below
0.5V. Open circuit when unused.
⎯R⎯S⎯T (Pin 10): Reset Output. This pin is an open drain
pull-down. Pulls low when VM input is below 0.5V and is
held low for 200ms after VM input is above 0.5V. Open
circuit when unused.
PDT (Pin 4): Power Down Time Input. A capacitor to
ground determines the additional time (6.4 seconds/μF)
that ⎯P⎯B or UVLO must be held low before releasing the
EN/⎯E⎯N and ⎯I⎯N⎯T outputs. If this pin is left open, the power
down delay time defaults to 64ms.
EN (LTC2953-1, Pin 11): Open Drain Enable Output. This
output is intended to enable system power. EN is asserted
high after a valid ⎯P⎯B turn on event (tDB, ON). EN is released
low if: a) ⎯K⎯I⎯L⎯L is not driven high (by μP) within 512ms of
the initial valid ⎯P⎯B power turn on event, b) ⎯K⎯I⎯L⎯L is driven
⎯ B
⎯ or UVLO is asserted and
low during normal operation, c) P
held low (t > tPD, Min + tPDT) during normal operation.
⎯P⎯B (Pin 5): Push Button Input. Connecting ⎯P⎯B to ground
through a momentary switch provides On/Off control via the
EN/⎯E⎯N and ⎯I⎯N⎯T outputs. An internal 100k pull-up resistor
connects to an internal 1.9V bias voltage. The rugged ⎯P⎯B
input withstands ±10kV ESD HBM and can be pulled up to
27V externally without consuming extra current. Voltages
below ground will not damage the pin.
⎯E⎯N (LTC2953-2, Pin 11): Open Drain Enable Output. This
output is intended to enable system power. ⎯E⎯N is asserted
low after a valid ⎯P⎯B turn on event (tDB, ON). ⎯E⎯N is released
high if: a) ⎯K⎯I⎯L⎯L is not driven high (by μP) within 512ms of
the initial valid ⎯P⎯B power turn-on event, b) ⎯K⎯I⎯L⎯L is driven
⎯ B
⎯ or UVLO is asserted and
low during normal operation, c) P
held low (t > tPD, Min + tPDT) during normal operation.
VIN (Pin 6): Power Supply Input: 2.7V to 27V.
I⎯ ⎯N⎯T (Pin 12): Open Drain Interrupt Output. After a turn off
event is detected (tDB, OFF) from ⎯P⎯B or UVLO, the LTC2953
interrupts the system (μP) by asserting ⎯I⎯N⎯T low. The μP
would perform power down and housekeeping tasks and
then assert the ⎯K⎯I⎯L⎯L pin low, thus releasing the enable output. The ⎯I⎯N⎯T pulse width is a minimum of 32ms and stays
low as long as ⎯P⎯B is asserted. If ⎯P⎯B is asserted for longer
than tPD, Min + tPDT, however, the ⎯I⎯N⎯T and EN/⎯E⎯N outputs
are immediately released. Open circuit when unused.
UVLO (Pin 7): UVLO Comparator Input. When UVLO drops
below its falling threshold (0.5V) for more than 32ms, the
LTC2953 asserts ⎯I⎯N⎯T low, thereby requesting a system
power down. If UVLO remains below its falling threshold
(0.5V) for longer than the adjustable power down delay,
the enable output is released. Additionally, UVLO provides
a ⎯P⎯B lock out feature that prevents the user from asserting
the enable output when UVLO falls below its threshold.
Connect to VIN if unused.
PFI (Pin 8): Power Fail Comparator Input. Input to an accurate comparator with a 0.5V falling threshold and 4mV
Exposed Pad (Pin 13): Exposed Pad may be left open or
connected to ground.
2953f
7
LTC2953
BLOCK DIAGRAM
VIN
2.7V TO 27V
REGULATOR
1.5k
2.4V
34V
ZENER
–
+
+
0.5V
VM
HV
–
HV
PFI
0.5V
PFO
200 ms RST
DELAY
RST
HV
2.4V
EN (–1)
EN (–2)
100k
PB
HV
KILL
DEBOUNCE AND
10μs FILTER
LOGIC
0.8V
UVLO
0.5V
0.6V
INT
HV
–
+
DEBOUNCE AND
10μs FILTER
OSCILLATOR
GND
HV INDICATES A
HIGH VOLTAGE PIN
2953 BD
PDT
2953f
8
LTC2953
TIMING DIAGRAMS
PB, UVLO AND KILL
IGNORED
PB
tDB, ON
tKILL, ON BLANK
EN
(LTC2953-1)
KILL
DO NOT CARE
SYSTEM SETS KILL HIGH
2953 TD01
Figure 1. Power On Timing (UVLO > 0.55V)
PB AND UVLO
IGNORED
PB
tDB, OFF
t < tPDT
PDT
tPD, Min
INT
tINT, Min
UVLO
EN
(LTC2953-1)
UVLO IGNORED
ENABLE DOES NOT SWITCH LOW
2953 TD02
Figure 2. ⎯P⎯B Interrupt Pulse: ⎯P⎯B Low for tDB,OFF < t < (tPD, Min + tPDT) (Enable Remains Active)
2953f
9
LTC2953
TIMING DIAGRAMS
PB AND UVLO
IGNORED
UVLO
tDB, OFF
t < tPDT
PDT
tPD, Min
INT
tINT, Min
PB
EN
(LTC2953-1)
PB IGNORED
ENABLE DOES NOT SWITCH LOW
2953 TD03
Figure 3. UVLO Interrupt Pulse: UVLO Low for tDB,OFF < t < (tPD, Min + tPDT) (Enable Remains Active)
PB
IGNORED
PB
tDB, OFF
16 CYCLES
PDT
tPD, Min
tPDT
INT
tINT, Max
EN
(LTC2953-1)
UVLO
UVLO IGNORED
2953 TD04
Figure 4. Push Button Power Down Timing: ⎯P⎯B Pressed and Held Low for t > (tPD, Min + tPDT)
2953f
10
LTC2953
TIMING DIAGRAMS
UVLO
IGNORED
UVLO
tDB, OFF
16 CYCLES
PDT
tPD, Min
tPDT
INT
tINT, Max
EN
(LTC2953-1)
PB
PB IGNORED
2953 TD05
Figure 5. UVLO Power Down Timing: UVLO Low for t > (tPD, Min + tPDT)
0.5V
0.5V
0.5V
VM
0.504V
PFI
tUV
tRST
tPFI
RST
tPFI
PFO
2953 TD06
2953 TD07
Figure 6. Voltage Monitor Reset Timing
Figure 7. Power Fail Comparator Timing
0.6V
tKILL(PW)
0.63V
KILL
EN
(LTC2953-1)
tKILL(PD)
2953 TD08
Figure 8. ⎯K⎯I⎯L⎯L Minimum Pulse Width and Propagation Delay
2953f
11
LTC2953
OPERATION
The LTC2953 is a push button On/Off controller with dual
function input and output supply monitors. The part contains all the circuitry needed to debounce a push button
input and provides a simple μP handshake protocol for
reliable toggling of system power. The LTC2953 operates
over a wide 2.7V to 27V input voltage range and draws
only 14μA of current.
The LTC2953 features dual function supply monitoring: a
power fail comparator generates an early warning and an
under voltage lock-out comparator initiates a controlled
system power down.
Push Button Controller
The push button input controls the enable and interrupt
outputs. The enable output toggles system power while
the interrupt output provides debounced push button
status. The interrupt output can be used in menu driven
applications to request a system power down. A power
kill input allows a microprocessor or other logic to release
the enable output, thus immediately powering down the
system.
To assert the enable output (turn on system power), press
the push button (⎯P⎯B) input and hold for at least 32ms.
See Figure 1.
Once system power has been enabled, a user can request
a system power down by again pressing the push button
for at least 32ms and releasing it before the PDT timer
counts 16 cycles. The LTC2953 then asserts the interrupt
output and the μP subsequently sets the ⎯K⎯I⎯L⎯L input low
to turn off system power. Note that the UVLO input can
also assert the interrupt output. See Figure 2 and Figure 3
and Dual Function Supply Monitors section.
In the event that the μP does not respond to the interrupt
request, the user can force release of the enable output by
pressing and holding down the push button (or UVLO) until
the PDT timer times out. See Figure 4 and Figure 5.
Dual Function Supply Monitors
An uncommitted power fail comparator provides real
time supply threshold information. The power fail input
(PFI) is compared against an accurate internal 0.5V reference and the comparison result is passed directly to the
power fail output (⎯P⎯F⎯O) pin. The operation of the power
fail comparator is de-coupled from all other functionality
and is always active. See Figure 7.
The under voltage lockout comparator provides the user
with another method to initiate a controlled system power
down. If the UVLO pin voltage falls below its falling threshold (0.5V) for longer than 32ms, the interrupt output is
asserted for a minimum of 32ms. If the UVLO pin voltage
remains below its threshold (0.5V) for an additional time
given by the PDT external capacitor, then the enable pin is
automatically released (thus powering down the system).
See Figure 3 and Figure 5.
This comparator also serves as an under voltage lockout. If
system power is off (enable released) and UVLO < 0.5V, the
UVLO comparator prevents the push button from turning
on system power (asserting enable output).
Voltage Supervisor with 200ms μP Reset
The LTC2953 provides a single adjustable supply monitor
with a nominal 200ms reset delay. When the VM input
voltage drops below 0.5V, the ⎯R⎯S⎯T output is pulled low.
⎯R⎯S⎯T remains low for 200ms after the VM input has risen
above 0.5V. The input 0.5V threshold has a guaranteed
accuracy of ±1.5% over temperature and process. The
operation of the supply monitor is de-coupled from all
other functionality and is always active. See Figure 6.
2953f
12
LTC2953
APPLICATIONS INFORMATION
PUSH BUTTON CONTROL
Short Pulse Interrupt
Power On Sequence
To enable system power, the push button input (⎯P⎯B) must
be held low continuously for 32ms (tDB, ON). Once the
enable output (EN/⎯E⎯N) is asserted, the LTC2953 starts
a 512ms internal timer (tKILL, ON BLANK). The ⎯K⎯I⎯L⎯L input
must be driven high within this 512ms window. This blanking 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.
To interrupt the μP, either ⎯P⎯B or UVLO must be low for
at least 32ms (tDB, OFF). This signals the μP either that a
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
PB, UVLO AND KILL
IGNORED
PB
tDB, ON
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.
tKILL, ON BLANK
EN
(LTC2953-1)
KILL
SYSTEM SETS
KILL HIGH
DO NOT CARE
2953 F09
Figure 9. Power On Timing (UVLO > 0.55V)
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).
PB OR UVLO
The length of time required to release the enable output
is given by a fixed internal 64ms delay (tPD, Min) plus an
adjustable power down timer delay (tPDT). The adjustable
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. CPDT is the PDT pin external
capacitor:
CPDT = 1.56E-4 [μF/ms] • (tPDT – 1ms)
See Figure 11.
SHORT PULSE
PB OR UVLO
tDB, OFF
LONG PULSE
INT
16 CYCLES
PDT
tINT, Min
KILL
DO NOT CARE
SYSTEM
POWER OFF
EN
(LTC2953-1)
2953 F10
Figure 10. Power Off Interrupt Timing
tPD, Min
SYSTEM SETS
KILL LOW
tPDT
EN
(LTC2953-1)
2953 F11
Figure 11. Forced Power Off Timing with Adjustable Delay
(See Figure 5 for More Details)
2953f
13
LTC2953
APPLICATIONS INFORMATION
PB, UVLO AND KILL
IGNORED
PB
tDB, ON
EN
(LTC2953-1)
KILL
SYSTEM SETS KILL LOW
KILL
tKILL, ON BLANK
TURN ON ABORTED
EN
(LTC2953-1)
SYSTEM POWER OFF
SYSTEM FAILS TO SET KILL HIGH
2953 F13
tKILL(PD)
2953 F12
Figure 12. Aborted Power On Sequence, ⎯K⎯I⎯L⎯L
Remaining Low Aborts Power On Sequence
Figure 13. μP Turns Off System Power
Aborted Power On Sequence
Power Fail Comparator
The LTC2953 provides an internal 512ms timer to detect
when a system fails to power on properly. A power on
sequence begins by debouncing the ⎯P⎯B input. After the
enable pin is subsequently asserted, the LTC2953 starts
the 512ms blanking timer (tKILL, ON BLANK). If the ⎯K⎯I⎯L⎯L
input is not driven high within this 512ms time window,
the enable pin is immediately released, thus turning off
system power. This failsafe feature prevents a user from
turning on the device when the circuits driving the ⎯K⎯I⎯L⎯L
input do not respond within 512ms after enable has been
asserted. See Figure 12.
This comparator provides real time threshold information
and can serve as the first warning of a decaying battery or
supply. The ⎯P⎯F⎯O output is driven low when the PFI input
voltage drops below its falling threshold (0.5V) and is
high impedance when PFI rises above its rising threshold
(0.504V). The low leakage, high voltage PFI input (10nA,
maximum) allows the use of large valued external resistors,
which lowers system current consumption.
μP Turns Off System Power During Normal Operation
Once the system has powered on and is operating normally,
the μP can turn off power by asserting the ⎯K⎯I⎯L⎯L input low.
See Figure 13.
DUAL FUNCTION BATTERY SUPERVISOR
The LTC2953 provides two comparators for battery
monitoring: an uncommitted power fail comparator and
a latched low battery comparator with μP interrupt. The
application shown in Figure 14 monitors a 2 cell Li-Ion
battery stack.
UVLO Comparator
The under voltage lockout comparator performs three
functions: a) interrupts the μP when a supply glitch drives
the UVLO voltage below its falling threshold (0.5V) for
longer than 32ms, followed by b) forces system power
off when the UVLO voltage falls below its falling threshold
(0.5V) for tPD, Min + tPDT, c) locks out the enable (prevents
system power on) output if UVLO voltage is below its falling threshold (0.5V) during system power on. See Figures
15A and 15B.
The low leakage (10nA, maximum), high voltage UVLO
input allows the use of large valued external resistors.
See Figure 14.
2953f
14
LTC2953
APPLICATIONS INFORMATION
INT
to the low offset architecture of the comparators, the
UVLO and ⎯P⎯F⎯I thresholds can be set to as close as ±5mV
apart. The trip thresholds of the circuit of Figure 14 are
6.04V and 5.40V for the power fail and low battery (UVLO)
comparators, respectively.
EN
Push Button Lockout
+
8.4V
VIN
LTC2953-1
DEBOUNCE
UVLO
COMPARATOR
R14
2150k
UVLO
–
VTH = 5.4V
50mV
R13
23.2k
0.5V
+
DEBOUNCE
AND DELAY
PFI
R12
196k
PFO
–
VTH = 6.04V
The LTC2953 provides a push button lock out feature that
prevents a user from turning on a system with a dead
battery. The push button input is ignored when the UVLO
input voltage is less than the falling threshold (0.5V). See
Figure 15B.
4mV
0.5V
+
UVLO
0.5V
SUPPLY
GLITCH
0.55V
tDB, OFF
POWER FAIL
COMPARATOR
2953 F14
2953 F15a
INT
tINT, Min
Figure 14. Dual Function Battery Comparators
Figure 15A. Supply Glitch Generates μP Interrupt
Which Input Initiated Power Down: ⎯P⎯B or UVLO?
The circuit in Figure 14 determines whether a power
down was initiated by a user pressing the push button
or by a battery drooping too low. If both ⎯I⎯N⎯T and ⎯P⎯F⎯O
outputs are low, then a low battery condition initiated a
power down.
UVLO
LOW SUPPLY CONDITION
tDB, OFF
INT
PFI and UVLO Thresholds
The circuit depicted in Figure 14 uses one resistive divider
network for both power fail and low battery comparators.
The power fail comparator trips at a higher battery voltage
than the low battery comparator, thus providing a battery
warning before a power down sequence is initiated. Due
0.5V
tPD, Min + tPDT
EN
LOW SUPPLY
LOCKS OUT
ENABLE
2953 F15b
Figure 15B. Low Supply Initiates System
Power Down and Locks Out Enable
2953f
15
LTC2953
TYPICAL APPLICATIONS
Push Button Buffer
Disconnect Input Resistive Divider To Save Power
The circuit of Figure 16 shows the power fail comparator
sensing the push button input. The ⎯P⎯F⎯O output toggles
each time the push button crosses 0.5V. This application
provides an early warning of push button activity.
In order to prolong battery life when system power has
been turned off, the LTC2953-2 power fail comparator can
be used to disconnect the external battery monitor resistive
divider. The circuit in Figure 18 connects ⎯P⎯F⎯I to ⎯E⎯N and
⎯P⎯F⎯O to the bottom end of the resistive divider.
8.4V
PFO
0.5V
PFI
R14
1070k
+
R5
100k
R9
100k
–
UVLO
PB
ON/OFF
R12
110k
2953 F16
VIN
EN
PFO
PFI
0.5V
–
+
Figure 16. Push Button Buffer
LTC2953-2
Power Path Switching
2953 F18
The high voltage ⎯E⎯N output of the LTC2953-2 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 17 shows the
LTC2953-2 in a 12V wall adapter application.
12V
TO LOAD
R5
100k
PB
ON/OFF
VIN
R9
100k
EN
LTC2953-2
Figure 18. Disconnect Input Resistive Divider to Save Power
When the user presses the push button to turn on system
power (⎯E⎯N low), the output of the power fail comparator
asserts ⎯P⎯F⎯O low. The low battery external resistive divider
is thus enabled to monitor the input supply. If the voltage
on the UVLO input falls to less than 0.5V, a system power
down sequence is initiated. Note that the IR drop across
the internal NFET is typically less than 0.2mV when the
UVLO pin voltage is 0.5V.
Once system power has been turned off (⎯E⎯N high), the
external resistive divider is disconnected and thus consumes zero DC current.
2953 F17
Figure 17. Power Path Switching
2953f
16
LTC2953
TYPICAL APPLICATIONS
Push Button Controlled μP Reset
Push Button Controlled Supply Sequencing
The circuit of Figure 19 can be used to keep a μP in reset
for 200ms after the push button has enabled system power.
After system power has stabilized, the voltage monitor
input continues to monitor the supply at the load end.
The circuit in Figure 20 uses the LTC2953-2 to sequence
3 supply rails. Power on sequencing begins by pressing
the push button for 32ms. This asserts the ⎯E⎯N output low,
which turns on the V1 supply. 200ms after V1 reaches 80%
of its final value (2.66V), the V2 supply is enabled. When
the V2 DC voltage reaches 80% of its final value (2V), the
V3 supply is enabled. Note that there is no internal delay
from the ⎯P⎯F⎯I input to the ⎯P⎯F⎯O output and so V3 is enabled
at the same time V2 rises above 2V.
TO LOAD
3.3V
R5
100k
VIN
PB
R9
100k
R3
499k
EN
A power down supply sequence begins when any of these
inputs is asserted: ⎯P⎯B , UVLO or ⎯K⎯I⎯L⎯L . When ⎯E⎯N pulls up
to VIN, V1 disconnects first. When V1 decays to 2.66V, V2
is immediately disabled (there is no 200ms delay from VM
to ⎯R⎯S⎯T during power down). When V2 decays to 2V, V3 is
immediately disabled. See Figure 21 timing diagram.
VM
LTC2953-2
R2
100k
ON/OFF
R11
510k
RST
2953 F19
PB
PB
0.5V
VM
POWER ON
POWER OFF
200ms
32ms
RST
EN
Figure 19. Push Button Controlled μP Reset
80%
80%
V1
3.3V
3.3V
R5
100k
VIN
LTC2953-2
200ms
R9
100k
V2
80%
80%
R3
866k
EN
VM
PB
V1
VTH = 2.66V
ON/OFF
R2
200k
V3
2953 F21
Figure 21. Push Button Controlled Supply Sequence Timing
VIN
DC/DC
#1
SHDN VOUT
RST
VTH = 2.01V
R15
604k
V2
2.5V
PFI
R16
200k
VIN
DC/DC
#2
PFO
SHDN VOUT
V3
1.8V
2953 F20
Figure 20. Push Button Controlled Supply Sequencing
2953f
17
LTC2953
TYPICAL APPLICATIONS
Dual Supply Monitor with μP Reset
Operation with Supply Transients over 40V
The circuit of Figure 22 monitors two supplies and provides
a μP reset. When either the ⎯P⎯F⎯I or the VM input voltage
falls below its threshold (0.5V), the ⎯R⎯S⎯T output is asserted
low. ⎯R⎯S⎯T remains low for 200ms after both inputs rise
above 0.5V. The low leakage ⎯P⎯F⎯O output allows for large
valued external resistors.
The application circuit of Figure 24 operates from a 24V
nominal supply, but can withstand supply transients as
high as 40V.
V2
LTC2953
PFI
PFO
–
V1
+
VM
The high voltage ⎯E⎯N output of the LTC2953-2 has an absolute maximum rating of 50V, which makes it suitable for
driving the gate of the external power PFET. The external
30V Zener diode (Z1) and the 10k current limiting resistor
(RZ) protect the VIN supply pin of the LTC2953-2. Note
that under normal 24V operation, the external Zener diode
does not conduct any current. The voltage drop across
RZ should be kept below 1V. Z2 should have a breakdown
voltage smaller than the PFET’s gate-to-source breakdown
voltage.
0.5V
RST
–
RST
24V NOMINAL,
40V TRANSIENTS
μP
+
0.5V
RZ
10k
30V
Z1
BZX84C30
1μF
50V
VIN
2953 F22
FDS4685
Si2319DS
NDS9407
10V
Z2
BZX84C10
R5
100k
R9
100k
EN
50V
ABS MAX
PB
Figure 22. Dual Supply Monitor with μP Reset
LTC2953-2
ON/OFF
Reverse Battery Protection
To protect the LTC2953 from a reverse battery connection, place a 1k resistor (R8) in series with the VIN pin.
See Figure 23.
2953 F24
Figure 24. Operation with 40V Supply Transients
Power Path Controller with Low Battery Detect
VIN
VOUT
+
8.4V
R8
1k
R5
910k
LT1761
SHDN
PB
VIN
EN
ON/OFF
LTC2953-1
2953 F23
The application in Figure 25 uses the push button to
completely disconnect the load from the battery. If the
battery voltage falls below the user specified threshold, the
push button is prevented from turning on system power
(asserting the enable output).
Figure 23. Reverse Battery Protection Using R8
2953f
18
LTC2953
PACKAGE DESCRIPTION
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
0.70 ±0.05
3.50 ±0.05
2.10 ±0.05
2.38 ±0.05
1.65 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.45 BSC
2.25 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
3.00 ±0.10
(4 SIDES)
R = 0.115
TYP
7
0.40 ± 0.10
12
2.38 ±0.10
1.65 ± 0.10
PIN 1 NOTCH
R = 0.20 OR
0.25 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
6
0.200 REF
1
0.23 ± 0.05
0.45 BSC
0.75 ±0.05
2.25 REF
(DD12) DFN 0106 REV A
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
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 AND TIE BARS SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
2953f
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.
19
LTC2953
TYPICAL APPLICATION
FDN360P
VIN
+
8.4V
R14
2150k
R5
100k
UVLO
R13
23.2k
VIN
R3
499k
LTC2953-2
PFI
R2
100k
PB
GND
PDT
3.3V
R11
100k
VM
RST
PFO
INT
KILL
DC/DC
SHDN
EN
R12
196k
ON/OFF
R9
100k
VOUT
R10
100k
R1
100k
RST
PFO
INT SYSTEM
LOGIC
KILL
2953 F25
1μF
tPDT = 6.4 SECONDS
Figure 25. PowerPath Controller with Low Battery Detect
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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LTC2952
Push Button Power Path Controller with
Supervisor
Automatic Low Loss Switchover Between DC Sources
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LTC4055
USB Power Controller and Li-Ion Charger
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2.6A Low Loss Ideal Diode in ThinSOT
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2953f
20 Linear Technology Corporation
LT 0607 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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