LINER LTC295ICDDB-2-TRPBF Push button on/off controller Datasheet

LTC2950-1/LTC2950-2
Push Button On/Off
Controller
FEATURES
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DESCRIPTION
Adjustable Push Button On/Off Timers
Low Supply Current: 6μA
Wide Operating Voltage Range: 2.7V to 26V
EN Output (LTC2950-1) Allows DC/DC Converter
Control
EN Output (LTC2950-2) Allows Circuit Breaker
Control
Simple Interface Allows Graceful μP Shut Down
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 ThinSOTTM Packages
APPLICATIONS
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Portable Instrumentation Meters
Blade Servers
Portable Customer Service PDA
Desktop and Notebook Computers
The LTC®2950 is a micropower, wide input voltage range,
push button ON/OFF controller. The part contains a push
button input with independently programmable ON and OFF
debounce times that control the toggling of an open drain
enable output. The part also contains a simple microprocessor interface to allow for proper system housekeeping
prior to power down. Under system fault conditions, an
internal KILL timer ensures proper power down.
The LTC2950 operates over a wide 2.7V to 26V input
voltage range to accommodate a wide variety of input
power supplies. Very low quiescent current (6μA typical)
makes the LTC2950 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 either 8-lead 3mm × 2mm DFN
or ThinSOT packages.
L, LT, LTC and LTM 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.
TYPICAL APPLICATION
Turn On Debounce
VIN
3V – 26V
VIN
VOUT
DC/DC
BUCK
SHDN
EN
VIN
R1
10k
EN
LTC2950-1
2V/DIV
PB
INT
INT
μP/μC
KILL
KILL
PB
GND
ONT
OFFT
2950 TA01
CONT*
0.033μF
10ms/DIV
COFFT*
0.033μF
2950 TA01b
*OPTIONAL
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LTC2950-1/LTC2950-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (VIN) ..................................– 0.3V to 33V
Input Voltages
PB ............................................................– 6V to 33V
ONT ......................................................– 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
LTC2950-C1 .............................................. 0°C to 70°C
LTC2950-C2 .............................................. 0°C to 70°C
LTC2950-I1 .......................................... – 40°C to 85°C
LTC2950-I2 .......................................... – 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
8
ONT 2
PB 3
VIN 4
9
TOP VIEW
INT
7
EN/EN
6
OFFT
5
KILL
VIN 1
PB 2
ONT 3
GND 4
8 KILL
7 OFFT
6 EN/EN
5 INT
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
DDB8 PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 140°C/W
TJMAX = 125°C, θJA = 165°C/W
EXPOSED PAD (PIN 9) UNCONNECTED
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
LTC2950CDDB-1#TRMPBF LTC2950CDDB-1#TRPBF LBKP
8-Lead Plastic DFN
LTC2950CDDB-2#TRMPBF LTC2950CDDB-2#TRPBF LBNG
8-Lead Plastic DFN
LTC295ICDDB-1#TRMPBF LTC295ICDDB-1#TRPBF
LBKP
8-Lead Plastic DFN
LTC295ICDDB-2#TRMPBF LTC295ICDDB-2#TRPBF
LBNG
8-Lead Plastic DFN
LTC2950CTS8-1#TRMPBF LTC2950CTS8-1#TRPBF
LTBKN
8-Lead Plastic TSOT-23
LTC2950CTS8-2#TRMPBF LTC2950CTS8-2#TRPBF
LTBNF
8-Lead Plastic TSOT-23
LTC2950ITS8-1#TRMPBF
LTC2950ITS8-1#TRPBF
LTBKN
8-Lead Plastic TSOT-23
LTC2950ITS8-2#TRMPBF
LTC2950ITS8-2#TRPBF
LTBNF
8-Lead Plastic TSOT-23
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on 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/
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
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LTC2950-1/LTC2950-2
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
VIN
Supply Voltage Range
Steady State Operation
●
IIN
VIN Supply Current
System Power On, VIN = 2.7V to 24V
●
VUVL
VIN Undervoltage Lockout
VIN Falling
●
VIN Undervoltage Lockout
Hysteresis
Push Button Pin (PB)
VUVL(HYST)
TYP
2.7
MAX
UNITS
26.4
V
6
12
μA
2.2
2.3
2.4
V
50
300
600
mV
VPB(MIN, MAX)
PB Voltage Range
Single-Ended
●
–1
26.4
V
IPB
PB Input Current
2.5V < VPB < 26.4V
VPB = 1V
VPB = 0.6V
●
●
●
–1
–3
–6
–9
±1
–12
–15
μA
μA
μA
●
0.6
0.8
1
V
1
1.6
2
V
VPB(VTH)
PB Input Threshold
PB Falling
VPB(VOC)
PB Open Circuit Voltage
IPB = –1μA
Debounce Timing Pins (ONT, OFFT)
IONT, OFFT(PU)
ONT/OFFT Pull Up Current
VONT, OFFT = 0V
●
–2.4
–3
–3.6
μA
IONT, OFFT(PD)
ONT/OFFT Pull Down Current
VONT, OFFT = 1.3V
●
2.4
3
3.6
μA
tDB, On
Internal Turn On Debounce Time
ONT Pin Float, PB Falling → Enable Asserted
●
26
32
41
ms
●
9
11.5
13.5
ms
●
26
32
41
ms
●
9
11.5
13.5
ms
±1
μA
tONT
Additional Adjustable Turn On Time CONT = 1500pF
tDB, Off
Internal Turn Off Debounce Time
tOFFT
Additional Adjustable Turn Off Time COFFT = 1500pF
OFFT Pin Float, PB Falling → INT Falling
μP Handshake Pins (INT, KILL)
IINT(LKG)
INT Leakage Current
VINT(VOL)
VKILL(TH)
VKILL(HYST)
KILL Input Threshold Hysteresis
IKILL(LKG)
KILL Leakage Current
tKILL(PW)
KILL Minimum Pulse Width
VINT = 3V
●
INT Output Voltage Low
IINT = 3mA
●
KILL Input Threshold Voltage
KILL Falling
●
0.11
0.4
V
0.57
0.6
0.63
V
10
30
50
mV
±0.1
μA
VKILL = 0.6V
●
30
μs
tKILL(PD)
KILL Propagation Delay
KILL Falling → Enable Released
●
30
μs
tKILL, On Blank
KILL Turn On Blanking (Note 3)
KILL = Low, Enable Asserted → Enable Released
●
400
512
650
ms
tKILL, Off Delay
KILL Turn Off Delay (Note 4)
KILL = High, INT Asserted → Enable Released
●
800
1024
1300
ms
tEN/EN, Lock Out
EN/EN Lock Out Time (Note 5)
Enable Released → Enable Asserted
●
200
256
325
ms
IEN/EN(LKG)
EN/EN Leakage Current
VEN/ EN = 1V, Sink Current Off
●
±0.1
μA
VEN/EN(VOL)
EN/EN Voltage Output Low
IEN/ EN = 3mA
●
0.4
V
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 tDB, ON or tONT.
0.11
Note 4: The KILL turn off delay is the maximum delay from the initiation
of a shutdown sequence (INT falling), to the release of the enable output.
If the KILL input switches low at any time during this period, enable is
released, thus turning off system power. This time is internally fixed at
1024ms. This time delay does not include tDB, OFF or tOFFT.
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. PB is ignored during this lock out
time. This time delay does not include tDB, ON or tONT.
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LTC2950-1/LTC2950-2
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
10
10
8
TA = 25°C
8
VIN = 2.7V
4
2
40
tDB, ON (ms)
IVIN (μA)
VIN = 3.3V
6
6
4
2
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
0
100
0
5
10
15
20
25
ONT PULL-DOWN CURRENT (μA)
tDB, ON + tONT (ms)
25
20
30
50
100
40
–3.2
VIN = 26.4V
–3.0
VIN = 2.7V
–2.8
–2.6
–50
1000
–25
0
25
50
TEMPERATURE (°C)
75
0
100
2950 G07
10
15
VIN (V)
20
–250
25
VIN = 26.4V
–3.0
VIN = 2.7V
–2.8
–2.6
–50
30
TA = 25°C
VIN = 3.3V
–200
–3.2
PB CURRENT (μA)
OFFT PULL-DOWN CURRENT (μA)
1000
5
PB Current vs PB Voltage
–3.4
100
0
2950 G06
OFFT Pull-Down Current
vs Temperature
10000
1000
20
2950 G05
Turn Off Debounce Time (tDB, OFF
+ tOFFT) vs OFFT External Capacitor
TA = 25°C
VIN = 3.3V
30
10
2950 G04
tDB, OFF + tOFFT (ms)
15
VIN (V)
TA = 25°C
1000
100
10
OFFT EXTERNAL CAPACITOR (nF)
10
5
Internal Default Turn Off
Debounce Time (tDB, OFF) vs VIN
–3.4
TA = 25°C
VIN = 3.3V
1
0
2950 G03
ONT Pull-Down Current
vs Temperature
10000
10
0
30
2950 G02
Turn On Debounce Time (tDB, ON
+ tONT) vs ONT External Capacitor
100
10
ONT EXTERNAL CAPACITOR (nF)
20
VIN (V)
2950 G01
1
30
10
tDB, OFF (ms)
IVIN (μA)
50
TA = 25°C
VIN = 26.4V
10
Internal Default Turn On
Debounce Time (tDB, ON) vs VIN
Supply Current vs Supply Voltage
–150
–100
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2950 G08
0
–10
–5
0
5
10 15
PB VOLTAGE (V)
20
25
30
2950 G09
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LTC2950-1/LTC2950-2
TYPICAL PERFORMANCE CHARACTERISTICS
PB Voltage vs External PB
Resistance to Ground
EN/EN VOL vs Current Load
300
500
VIN = 3.3V
TA = 25°C
VIN = 3.3V
400
200
EN/EN VOLTAGE (mV)
PB VOLTAGE (mV)
250
TA = 100°C
150
TA = 25°C
TA = –45°C
100
300
200
100
50
0
0
0
5
10
15
20
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
0
2
6
8
4
EN/EN CURRENT LOAD (mA)
2950 G10
2950 G11
EN (LTC2950-2) Voltage vs VIN
EN (LTC2950-1) Voltage vs VIN
1.0
4
TA = 25°C
100k PULL-UP FROM EN TO VIN
TA = 25°C
100k PULL-UP FROM EN TO VIN
0.8
3
0.6
EN (V)
EN (V)
10
2
0.4
1
0.2
0
0
1
2
3
4
VIN (V)
0
0
1
2
3
4
VIN (V)
2950 G12
2950 G13
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LTC2950-1/LTC2950-2
PIN FUNCTIONS
(TSOT-23/DFN)
VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.
PB (Pin 2/Pin 3): Push Button Input. Connecting PB to
ground through a momentary switch provides on/off
control via the EN/EN pin. An internal 100k pull-up resistor connects to an internal 1.9V bias voltage. The rugged
PB input can be pulled up to 26.4V externally without
consuming extra current.
ONT (Pin 3/Pin 2): Additional Adjustable Turn On Time
Input. Placing an external capacitor to ground determines
the additional time (beyond the internal default 32ms)
the PB pin must be held low before the enable output
is asserted. Floating this pin results in a default turn on
debounce time of 32ms.
GND (Pin 4/Pin 1): Device Ground.
INT (Pin 5/Pin 8): Open Drain Interrupt Output. After a push
button turn-off event is detected, the LTC2950 interrupts the
system (μP) by bringing the INT pin low. Once the system
finishes its power down and housekeeping tasks, it sets
KILL low, which in turn releases the enable output. If at the
end of the power down timer (1024ms) KILL is still high, the
enable output is released immediately. INT may optionally
be tied to KILL to release the enable output immediately
after the turn-off event has been detected (INT = low).
EN (LTC2950-2, Pin 6/Pin 7): Open Drain Enable Output.
This pin is intended to enable system power. EN is asserted low after a valid PB turn-on event. EN releases
high if: a) KILL is not driven high (by μP) within 512ms of
the initial valid PB power turn-on event, b) KILL is driven
low during normal operation, c) a second valid PB event
(power turn-off) is detected. The operating range of this
pin is 0V to 10V.
OFFT (Pin 7/Pin 6): Additional Adjustable Turn Off Time
Input. A capacitor to ground determines the additional
time (beyond the internal default 32ms) that the PB pin
must be held low before initiating a power down sequence
(INT falling). Floating this pin results in a default turn off
time of 32ms.
KILL (Pin 8/Pin 5): KILL Input. Forcing KILL low releases
the enable output. During system turn on, this pin is
blanked by a 512ms internal timer to allow the system to
pull KILL 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.
EN (LTC2950-1, Pin 6/Pin 7): Open Drain Enable Output.
This pin is intended to enable system power. EN is asserted high after a valid PB turn on event. EN is released
low if: a) KILL is not driven high (by μP) within 512ms of
the initial valid PB power turn-on event, b) KILL is driven
low during normal operation, c) a second valid PB event
(power turn-off) is detected. The operating range for this
pin is 0V to 10V.
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LTC2950-1/LTC2950-2
BLOCK DIAGRAMS
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
2950 BD
ONT
OFFT
TIMING DIAGRAMS
tKILL(PW)
KILL
tKILL(PD)
EN/EN
2950 TD01
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LTC2950-1/LTC2950-2
TIMING DIAGRAMS
PB
PB & KILL IGNORED
tDB, ON
tONT
tKILL, ON BLANK
16 CYCLES
EN
(LTC2950-1)
EN
(LTC2950-2)
2950 TD02
Power On Timing
PB
tDB, OFF
PB IGNORED
tOFFT
OFFT
16 CYCLES
INT
tKILL, OFF DELAY
EN
(LTC2950-1)
EN
(LTC2950-2)
2950 TD03
Power Off Timing, KILL > 0.6V
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LTC2950-1/LTC2950-2
APPLICATIONS INFORMATION
Description
The LTC2950 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 turn-on and turn-off debounce
times are extendable using optional external capacitors. A
simple interface (INT output, KILL input) allows a system to
power on and power off in a controlled manner.
Turn On
When power is first applied to the LTC2950, the part initializes the output pins. Any DC/DC converters connected
to the EN/EN pin will therefore be held off. To assert the
enable output, PB must be held low for a minimum of
32ms (tDB, ON). The LTC2950 provides additional turn on
debounce time via an optional capacitor connected to the
ONT pin (tONT). The following equation describes the additional time that PB must be held low before asserting the
enable output. CONT is the ONT external capacitor:
CONT = 1.56E-4 [μF/ms] • (tONT – 1ms)
Once the enable output is asserted, any DC/DC converters
connected to this pin are turned on. The KILL input from the
μP is ignored during a succeeding 512ms blanking time (tKILL,
ON BLANK). This blanking time represents the maximum
time required to power up the DC/DC converter and the μP.
If KILL 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, PB 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 PB 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 PB has been validly pressed, INT is switched low. This
alerts the μP to perform its power down and housekeeping
tasks. The power down time given to the μP is 1024ms.
Note that the KILL input can be pulled low (thereby releasing the
enable output) at any time after tKILL, ON BLANK period.
Simplified Power On/Off Sequence
Figure 1 shows a simplified LTC2950-1 power on and power
off sequence. A high to low transition on PB (t1) initiates
the power on sequence. This diagram does not show any
bounce on PB. In order to assert the enable output, the
PB pin must stay low continuously (PB high resets timers)
for a time controlled by the default 32ms and the external
ONT capacitor (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 KILL 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 LTC2950 does not sample KILL and
PB until after the 512ms internal timer has expired. The reason PB 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 PB pin is then debounced with an internal
32ms timer. The system has now properly powered on and
the LTC2950 monitors PB and KILL (for a turnoff command)
while consuming only 6μA of supply current.
A high to low transition on PB (t5) initiates the power off
sequence. PB must stay low continuously (PB 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 (INT) is set, signifying
that EN will be switched low in 1024ms. Once a system has
finished performing its power down operations, it can set
KILL low (t7) and thus immediately set EN low), terminating
the internal 1024ms timer. The release of the PB pin is then
debounced with an internal 32ms timer.
The system is now in its reset state: where the LTC2950
is in low power mode (6μA). PB is monitored for a high
to low transition.
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LTC2950-1/LTC2950-2
APPLICATIONS INFORMATION
t1
t2
PB
t3
t4
t5
t6
PB & KILL IGNORED
tDB, ON
PB IGNORED
tKILL, ON BLANK
tONT
t7
< tKILL,
OFF DELAY
tDB, OFF
ONT
tOFFT
OFFT
INT
<tKILL, OFF DELAY
KILL
EN
2950 F01
Figure 1. Simplified Power On/Off Sequence for LTC2950-1
tABORT
PB
tDB, ON + tONT
512ms
INTERNAL
TIMER
POWER ON
TIMING
POWER
TURNED OFF
EN
μP FAILED TO SET
KILL HIGH
KILL
2950 F02
Figure 2. Aborted Power On Sequence for LTC2950-1
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LTC2950-1/LTC2950-2
APPLICATIONS INFORMATION
Aborted Power On Sequence
The power on sequence is aborted when the KILL 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 KILL is still low, EN pulls low (thus
turning off the DC/DC converter).
Figure 4 shows the μP turning power off. After a low on
KILL releases enable, the internal 256ms timer ignores the
PB pin. This is shown as tEN/EN, LOCKOUT in Figure 4.
LTC2950-1, LTC2950-2 VERSIONS
DC/DC Turn Off Blanking
The LTC2950-1 (high true EN) and LTC2950-2 (low true
EN) differ only by the polarity of the EN/EN pin. Both versions allow the user to extend the amount of time that
the PB must be held low in order to begin a valid power
on/off sequence. An external capacitor placed on the ONT
pin adds additional time to the turn on time. An external
capacitor placed on the OFFT pin adds additional time to
the turn off time. If no capacitor is placed on the ONT
(OFFT) pin, then the turn on (off) duration is given by an
internally fixed 32ms timer.
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 PB) to restart
the converter. This condition guarantees that the μP has
always powered down completely before it is restarted.
The LTC2950 fixes the KILL turn off delay time (tKILL, OFF
DELAY) at 1024ms. This means that the EN/EN pin will be
switched low/high a maximum of 1024ms after initiating
a valid turn off sequence. Note that in a typical application,
a μP or μC would set KILL low prior to the 1024ms timer
period (t7 in Figure 1).
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 KILL low, as
shown in Figure 3. At time tKILL, KILL is set low by the
μP. This immediately pulls EN low, thus turning off the
DC/DC converter.
tEN/EN, LOCKOUT
PB
POWER ON
PB IGNORED
tKILL
DC/DC
TURNS OFF
PB
PB BLANKING
256ms
DC/DC
TURNS OFF
EN
EN
μP SETS
KILL LOW
KILL
μP SETS
KILL LOW
KILL
XXX DON’T CARE
XXX DON’T CARE
2950 F04
2950 F03
Figure 3. μP Turns Off Power (LTC2950-1)
Figure 4. DC/DC Turn Off Blanking (LTC2950-1)
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LTC2950-1/LTC2950-2
APPLICATIONS INFORMATION
The following equations describe the turn on and turn
off times. CONT and COFFT are the external programming
capacitors:
tBD,ON + tONT = 32ms + 1ms + (6.7x106) • CONT
tBD,OFF + tOFFT = 32ms + 1ms + (6.7x106) • COFFT
High Voltage Pins
The VIN and PB pins can operate at voltages up to 26.4V.
PB can, additionally, operate below ground (–6V) without
latching up the device. PB has an ESD HBM rating of ±10kV.
If the push button switch connected to PB 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 LTC2950 PB pin, parasitic
capacitances may couple onto the high impedance PB
input. Additionally, parasitic series inductance may cause
unpredictable ringing at the PB pin. Placing a 5k resistor
from the PB pin to the push button switch would mitigate
parasitic inductance problems. Placing a 0.1μF capacitor
on the PB pin would lessen the impact of parasitic capacitive coupling.
TYPICAL APPLICATIONS
Voltage Monitoring with KILL Input
The KILL pin can be used as a voltage monitor. Figure 5
shows an application where the KILL 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 KILL 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
KILL comparator.
The DC/DC converter shown has an internal pull-up current on
its SHDN pin. A pull-up resistor on EN is thus not needed.
Operation Without μP
Figure 6 shows how to connect the KILL pin when there
is no circuitry available to drive it. The minimum pulse
width detected is 30μs. If there are glitches on the resistor
VIN
VIN
9V
VIN
9V
3.3V
VOUT
VIN
LT1767-3.3
LT1767-3.3
SHDN
SHDN
5.4V THRESHOLD
R3
806k
1%
VIN
C4
0.1μF
3.3V
VOUT
EN
LTC2950-1
R2
100k
1%
R1
100k
R1
10k
C4
0.1μF
INT
INT
VIN
EN
LTC2950-1
INT
+
μP
PB
KILL
GND ONT
OFFT
KILL
(OPEN DRAIN)
PB
KILL
GND ONT
OFFT
C3*
0.01μF
2950 F05
CONT*
0.033μF
CONT*
0.033μF
COFFT*
0.033μF
*OPTIONAL
Figure 5. Input Voltage Monitoring with KILL Input
COFFT*
0.033μF
*OPTIONAL
2950 F06
Figure 6. No μP Application
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12
LTC2950-1/LTC2950-2
TYPICAL APPLICATIONS
PB Pin in a Noisy Environment
pull-up voltage that are wider than 30μs and transition
below 0.6V, then an appropriate bypass capacitor should
be connected to the KILL pin.
The rugged PB pin is designed to operate in noisy environments. Transients below ground (>–6V) and above VIN
(<30V) will not damage the rugged PB pin. Additionally,
the PB pin can withstand ESD HBM strikes up to ±10kV.
Power Path Switching
The EN open drain output of the LTC2950-2 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 PB pin. Figure 7 shows the LTC2950-2
controlling a two cell Li-Ion battery application. The INT
and KILL pins are connected to the output of the PFET
through a resistor divider. The KILL pin serves as a voltage
monitor. When VOUT drops below 6V, the EN pin is open
circuited 30μs later.
In order to keep external noise from coupling inside the
LTC2950, place an R-C network close to the PB pin. A
5k resistor and a 0.1μF capacitor should suffice for most
noisy applications (see Figure 8).
External Pull-Up Resistor on PB
An internal pull-up resistor on the PB pin makes an external pull-up resistor unnecessary. Leakage current on
VOUT
M1
R5
100K
4.2V
SINGLE CELL
Li-Ion BATTERY
R1
909k
1%
+
VIN
C4
0.1μF
CERAMIC
4.2V
SINGLE CELL
Li-Ion BATTERY
VOUT,TRIP POINT = 6V
EN
LTC2950-2
+
INT
PB
KILL
GND ONT
OFFT
CONT*
0.033μF
OPEN DRAIN OUTPUT
OPTIONAL GLITCH
FILTER CAPACITOR
VTH = 0.6V INPUT
R4
100k
1%
C3*
0.1μF
COFFT*
0.033μF
*OPTIONAL
2950 F07
Figure 7. Power Path Control with 6V Under Voltage Detect
VIN
PARASITICS
TRACE
CAPACITANCE
R6
5k
NOISE
TRACE
INDUCTANCE
C5
0.1μF
EN
VIN
PB
LTC2950-1
GND
ONT
INT
KILL
OFFT
DETAILS OMITTED
FOR CLARITY
2950 F08
Figure 8. Noisy PB Trace
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13
LTC2950-1/LTC2950-2
TYPICAL APPLICATIONS
the PB board trace, however, will affect the open circuit
voltage on the PB pin. If the leakage is too large (>2μA),
the PB 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).
VIN
Reverse Battery Protection
To protect the LTC2950 from a reverse battery connection, place a 1k resistor in series with the VIN pin (see
Figure 10).
VIN
LTC2950-1/
LTC2950-2
2.4V
R7
10k
100k
PB
EXTERNAL BOARD
LEAKAGE CURRENT
>2μA
GND
PINS OMITTED
FOR CLARITY
2950 F09
IF EXTERNAL PARASITIC BOARD
LEAKAGE >2μA, USE EXTERNAL
PULL-UP RESISTOR
Figure 9. External Pull-Up Resistor on PB Pin
PACKAGE DESCRIPTION
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702)
0.61 p 0.05
(2 SIDES)
3.00 p 0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 p 0.10
8
0.70 p 0.05
2.55 p 0.05
1.15 p 0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50 BSC
2.20 p 0.05
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
2.00 p 0.10
(2 SIDES)
0.56 p 0.05
(2 SIDES)
0.75 p 0.05
0 – 0.05
4
0.25 p 0.05
1
PIN 1
R = 0.20 OR
0.25 s 45°
CHAMFER
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 p 0.05
(2 SIDES)
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
295012fb
14
LTC2950-1/LTC2950-2
PACKAGE DESCRIPTION
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
295012fb
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
LTC2950-1/LTC2950-2
TYPICAL APPLICATION
VIN
9V
BATTERY
+
R5
910k
R8
1k
VOUT
LT1761-1.8
SHDN
1.8V
VIN
C4
0.1μF
R1
10k
EN
LTC2950-1
INT
INT
PB
KILL
KILL
GND ONT
OFFT
μP
CONT*
0.033μF
COFFT*
0.033μF
*OPTIONAL
2950 F10
Figure 10. Reverse Battery Protection
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2900
Programmable Quad Supply Monitor
Adjustable RESET, 10-Lead MSOP and 3mm x 3mm DFN Packages
LTC2904/2905
Pin-Programmable Dual Supply Monitors
Adjustable RESET and Tolerance, 8-Lead SOT-23 and 3mm x 2mm DFN Packages
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
295012fb
16
Linear Technology Corporation
LT 0208 REV B • PRINTED IN USA
FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
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