LTC2950ITS8-1#TRPBF - ANALOG DEVICES

LTC2950-1/LTC2950-2

295012fd

2V/DIV

10ms/DIV 2950 TA01b

Pushbutton On/Off

Controller

The LTC

2950 is a micropower, wide input voltage range,

pushbutton ON/OFF controller. The part contains a pushbut-

ton 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 micropro-

cessor 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 26.4V 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 ac-

commodate either positive or negative enable polarities.

The parts are available in either 8-lead 3mm × 2mm DFN

or ThinSOT packages.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other trademarks

are the property of their respective owners.

n Portable Instrumentation Meters

n Blade Servers

n Portable Customer Service PDA

n Desktop and Notebook Computers

n Adjustable Pushbutton On/Off Timers

n Low Supply Current: 6µA

n Wide Operating Voltage Range: 2.7V to 26.4V

n EN Output (LTC2950-1) Allows DC/DC Converter

Control

n EN Output (LTC2950-2) Allows Circuit Breaker

Control

n Simple Interface Allows Graceful µP Shut Down

n High Input Voltage PB Pin with Internal Pull Up

Resistor

n ±10kV ESD HBM on PB Input

n Accurate 0.6V Threshold on KILL Comparator Input

n 8-Pin 3mm × 2mm DFN and ThinSOT™ Packages

VIN

SHDN**

VIN

VOUT

INT

KILL

INT

KILL

LTC2950-1

ONT OFFT

DC/DC

BUCK

µP/µC

2.7V TO 26.4V

*OPTIONAL

**SHDN INTERNALLY PULLED UP BY DC/DC

10k

2950 TA01

CONT*

0.033µF

COFFT*

0.033µF

GND

VIN

Typical applicaTion

Turn On Debounce

DescripTion

FeaTures

applicaTions

LTC2950-1/LTC2950-2

295012fd

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

LTC2950C-1 ............................................. 0°C to 70°C

LTC2950C-2 ............................................. 0°C to 70°C

LTC2950I-1 ..........................................–40°C to 85°C

LTC2950I-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

TOP VIEW

DDB8 PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

1GND

ONT

VIN

INT

EN/EN

OFFT

KILL

TJMAX = 125°C, θJA = 165°C/W

EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL

VIN 1

PB 2

ONT 3

GND 4

8 KILL

7 OFFT

6 EN/EN

5 INT

TOP VIEW

TS8 PACKAGE

8-LEAD PLASTIC TSOT-23

TJMAX = 125°C, θJA = 140°C/W

Lead Free Finish

TAPE AND REEL (MINI) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC2950CDDB-1#TRMPBF LTC2950CDDB-1#TRPBF LBKP 8-Lead Plastic DFN 0°C to 70°C

LTC2950CDDB-2#TRMPBF LTC2950CDDB-2#TRPBF LBNG 8-Lead Plastic DFN 0°C to 70°C

LTC2950IDDB-1#TRMPBF LTC2950IDDB-1#TRPBF LBKP 8-Lead Plastic DFN –40°C to 85°C

LTC2950IDDB-2#TRMPBF LTC2950IDDB-2#TRPBF LBNG 8-Lead Plastic DFN –40°C to 85°C

LTC2950CTS8-1#TRMPBF LTC2950CTS8-1#TRPBF LTBKN 8-Lead Plastic TSOT-23 0°C to 70°C

LTC2950CTS8-2#TRMPBF LTC2950CTS8-2#TRPBF LTBNF 8-Lead Plastic TSOT-23 0°C to 70°C

LTC2950ITS8-1#TRMPBF LTC2950ITS8-1#TRPBF LTBKN 8-Lead Plastic TSOT-23 –40°C to 85°C

LTC2950ITS8-2#TRMPBF LTC2950ITS8-2#TRPBF LTBNF 8-Lead Plastic TSOT-23 –40°C to 85°C

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/

pin conFiguraTion

absoluTe MaxiMuM raTings

(Note 1)

orDer inForMaTion

LTC2950-1/LTC2950-2

295012fd

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VIN Supply Voltage Range Steady State Operation l2.7 26.4 V

IIN VIN Supply Current System Power On, VIN = 2.7V to 24V l6 12 µA

VUVL VIN Undervoltage Lockout VIN Falling l2.2 2.3 2.4 V

VUVL(HYST) VIN Undervoltage Lockout

Hysteresis

50 300 600 mV

Pushbutton, Enable (PB, EN/EN)

VPB(MIN, MAX) PB Voltage Range Single-Ended l–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

VPB(VTH) PB Input Threshold PB Falling l0.6 0.8 1 V

VPB(VOC) PB Open Circuit Voltage IPB = –1µA 1 1.6 2 V

tEN/EN, Lock Out EN/EN Lock Out Time (Note 5) Enable Released → Enable Asserted l200 256 325 ms

IEN/EN(LKG) EN/EN Leakage Current VEN/

EN = 1V, Sink Current Off l±0.1 µA

VEN/EN(VOL) EN/EN Voltage Output Low IEN/

EN = 3mA l0.11 0.4 V

Debounce Timing Pins (ONT, OFFT)

IONT, OFFT(PU) ONT/OFFT Pull Up Current VONT, OFFT = 0V l–2.4 –3 –3.6 µA

IONT, OFFT(PD) ONT/OFFT Pull Down Current VONT, OFFT = 1.3V l2.4 3 3.6 µA

tDB, On Internal Turn On Debounce Time ONT Pin Float, PB Falling → Enable Asserted l26 32 41 ms

tONT Additional Adjustable Turn On Time CONT = 1500pF l9 11.5 13.5 ms

tDB, Off Internal Turn Off Debounce Time OFFT Pin Float, PB Falling → INT Falling l26 32 41 ms

tOFFT Additional Adjustable Turn Off Time COFFT = 1500pF l9 11.5 13.5 ms

µP Handshake Pins (INT, KILL)

IINT(LKG) INT Leakage Current VINT = 3V l±1 µA

VINT(VOL) INT Output Voltage Low IINT = 3mA l0.11 0.4 V

VKILL(TH) KILL Input Threshold Voltage KILL Falling l0.57 0.6 0.63 V

VKILL(HYST) KILL Input Threshold Hysteresis 10 30 50 mV

IKILL(LKG) KILL Leakage Current VKILL = 0.6V ±0.1 µA

tKILL(PW) KILL Minimum Pulse Width l30 µs

tKILL(PD) KILL Propagation Delay KILL Falling → Enable Released l30 µs

tKILL, On Blank KILL Turn On Blanking (Note 3) KILL = Low, Enable Asserted → Enable Released l400 512 650 ms

tKILL, Off Delay KILL Turn Off Delay (Note 4) KILL = High, INT Asserted → Enable Released l800 1024 1300 ms

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.

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.

elecTrical characTerisTics

The l 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)

LTC2950-1/LTC2950-2

295012fd

TEMPERATURE (°C)

–50

IVIN (µA)

–25 0 25 50

2950 G01

75 100

VIN = 26.4V

VIN = 3.3V

VIN = 2.7V

0510 15 20 25 30

VIN (V)

IVIN (µA)

2950 G02

TA = 25°C

2950 G03

VIN (V)

tDB, ON (ms)

510 15 20 25 30

TA = 25°C

Supply Current vs Temperature

Supply Current vs Supply Voltage

Internal Default Turn On

Debounce Time (tDB, ON) vs VIN

tDB, ON + tONT (ms)

100

1000

2950 G04

10 10 100

10000 TA = 25°C

VIN = 3.3V

ONT EXTERNAL CAPACITOR (nF) TEMPERATURE (°C)

–50 –25 0 25 50 75 100

ONT PULL-DOWN CURRENT (µA)

2950 G05

–3.4

–3.2

–3.0

–2.8

–2.6

VIN = 26.4V

VIN = 2.7V

VIN (V)

tDB, OFF (ms)

5 10 15 20

2950 G06

25 30

TA = 25°C

2950 G07

tDB, OFF + tOFFT (ms)

100

1000

10 10 100

10000 TA = 25°C

VIN = 3.3V

OFFT EXTERNAL CAPACITOR (nF)

2950 G08

TEMPERATURE (°C)

–50 –25 0 25 50 75 100

OFFT PULL-DOWN CURRENT (µA)

–3.4

–3.2

–3.0

–2.8

–2.6

VIN = 26.4V

VIN = 2.7V

PB CURRENT (µA)

2950 G09

–10 0 10 20 30–5 5 15 25

–250

–200

–150

–100

–50

PB VOLTAGE (V)

TA = 25°C

VIN = 3.3V

Turn On Debounce Time (tDB, ON

+ tONT) vs ONT External Capacitor

ONT Pull-Down Current

vs Temperature

Internal Default Turn Off

Debounce Time (tDB, OFF) vs VIN

Turn Off Debounce Time (tDB, OFF

+ tOFFT) vs OFFT External Capacitor

OFFT Pull-Down Current

vs Temperature

PB Current vs PB Voltage

Typical perForMance characTerisTics

LTC2950-1/LTC2950-2

295012fd

2950 G10

100

150

200

250

300

5 10 15 20

VIN = 3.3V

TA = 25°C

PB VOLTAGE (mV)

EXTERNAL PB RESISTANCE TO GROUND (kΩ)

TA = –45°C

TA = 100°C

EN/EN CURRENT LOAD (mA)

EN/EN VOLTAGE (mV)

500

400

300

200

100

2950 G11

24610

TA = 25°C

VIN = 3.3V

VIN (V)

EN (V)

2950 G12

123

TA = 25°C

100k PULL-UP FROM EN TO VIN

1.0

0.8

0.6

0.4

0.2

EN (V)

2950 G13

VIN (V)

0 4

123

TA = 25°C

100k PULL-UP FROM EN TO VIN

EN (LTC2950-1) Voltage vs VIN

EN (LTC2950-2) Voltage vs VIN

PB Voltage vs External PB

Resistance to Ground

EN/EN VOL vs Current Load

Typical perForMance characTerisTics

LTC2950-1/LTC2950-2

295012fd

VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.

PB (Pin 2/Pin 3): Pushbutton Input. Connecting PB to

ground through a momentary switch provides on/off

control via the EN/EN pin. An internal 100k pull-up resis-

tor 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

pushbutton turn-off event is detected, the LTC2950 inter-

rupts 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 (LTC2950-1, 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 dur-

ing normal operation, c) a second valid PB event (power

turn-off) is detected. This pin can connect directly to a

DC/DC converter shutdown pin that provides an internal

pull-up. Otherwise a pull-up resistor to an external supply

is required. The operating range for this pin is 0V to 10V.

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 dur-

ing normal operation, c) a second valid PB event (power

turn-off) is detected. This pin can connect directly to a

DC/DC converter shutdown pin that provides an internal

pull-up. Otherwise a pull-up resistor to an external supply

is required. 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. If unused, connect to a

low voltage output supply (see Figure 6).

Exposed Pad (Pin 9): Exposed Pad may be left open or

connected to device ground.

(TSOT-23/DFN)

pin FuncTions

LTC2950-1/LTC2950-2

295012fd

KILL

EN/EN

tKILL(PW)

tKILL(PD)

2950 TD01

LOGIC

OSCILLATOR

DEBOUNCE

2.4V

100k

GND

VIN

2.7V TO 26.4V

EN/EN

KILL

INT

ONT OFFT

0.8V

0.6V

2950 BD

REGULATOR

10µS

FILTER

block DiagraM

TiMing DiagraMs

LTC2950-1/LTC2950-2

295012fd

Power On Timing

Power Off Timing, KILL > 0.6V

tDB, ON tONT

16 CYCLES

PB & KILL IGNORED

(LTC2950-1)

(LTC2950-2)

tKILL, ON BLANK

2950 TD02

tDB, OFF tOFFT

INT

OFFT

PB IGNORED

tKILL, OFF DELAY

2950 TD03

16 CYCLES

(LTC2950-1)

(LTC2950-2)

TiMing DiagraMs

LTC2950-1/LTC2950-2

295012fd

Description

The LTC2950 is a low power (6µA), wide input voltage

range (2.7V to 26.4V), pushbutton 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 ini-

tializes 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 ad-

ditional 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.

applicaTions inForMaTion

LTC2950-1/LTC2950-2

295012fd

Figure 1. Simplified Power On/Off Sequence for LTC2950-1

Figure 2. Aborted Power On Sequence for LTC2950-1

tABORT

KILL

POWER ON

TIMING

512ms

INTERNAL

TIMER

tDB, ON + tONT

POWER

TURNED OFF

2950 F02

µP FAILED TO SET

KILL HIGH

t1t2

tDB, ON tONT

t3t4t5t6t7

ONT

OFFT

KILL

INT

PB & KILL IGNORED PB IGNORED

2950 F01

tKILL, ON BLANK tDB, OFF

tOFFT

<tKILL, OFF DELAY

< tKILL,

OFF DELAY

applicaTions inForMaTion

LTC2950-1/LTC2950-2

295012fd

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

The LTC2950-1 (high true EN) and LTC2950-2 (low true

EN) differ only by the polarity of the EN/EN pin. Both ver-

sions 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.

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).

Figure 3. µP Turns Off Power (LTC2950-1)

tKILL

DC/DC

TURNS OFF

2950 F03

KILL XXX DON’T CARE

µP SETS

KILL LOW

PB PB IGNORED

KILL

PB BLANKING

XXX DON’T CARE

256ms

POWER ON

2950 F04

DC/DC

TURNS OFF

µP SETS

KILL LOW

tEN/EN, LOCKOUT

Figure 4. DC/DC Turn Off Blanking (LTC2950-1)

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).

µP Turns Off Power During Normal Operation

Once the system has powered on and is operating nor-

mally, 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.

DC/DC Turn Off Blanking

When the DC/DC converter is turned off, it can take a sig-

nificant 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.

applicaTions inForMaTion

LTC2950-1/LTC2950-2

295012fd

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 pushbutton switch connected to PB exhibits high

leakage current, then an external pull-up resistor to VIN is

recommended. Furthermore, if the pushbutton 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 pushbutton switch would mitigate

parasitic inductance problems. Placing a 0.1µF capacitor

on the PB pin would lessen the impact of parasitic capaci-

tive coupling.

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

pull-up voltage that are wider than 30µs and transition

Figure 5. Input Voltage Monitoring with KILL Input Figure 6. No µP Application

VIN

SHDN**

VIN

VOUT

INT

KILL

INT

KILL

(OPEN DRAIN)

LTC2950-1

GND ONT OFFT

LT1767-3.3

µP

10k

3.3V

2950 F05

0.1µF

806k

100k

5.4V THRESHOLD

VIN

CONT*

0.033µF

COFFT*

0.033µF

*OPTIONAL

**SHDN INTERNALLY PULLED UP BY THE LT1767-3.3

VIN

SHDN**

VIN

VOUT

LT1767-3.3

9V 3.3V

100k

C3*

0.01µF

2950 F06

0.1µF

INT

KILL

LTC2950-1

GND ONT OFFT

VIN

CONT*

0.033µF

COFFT*

0.033µF

*OPTIONAL

**SHDN INTERNALLY PULLED UP BY THE LT1767-3.3

applicaTions inForMaTion

Typical applicaTions

LTC2950-1/LTC2950-2

295012fd

below 0.6V, then an appropriate bypass capacitor should

be connected to the KILL pin.

PowerPath™ 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.

VOUT

909k

100k

C3*

0.1µF

2950 F07

0.1µF

CERAMIC

*OPTIONAL

OPEN DRAIN OUTPUT

VTH = 0.6V INPUT

100K

4.2V

SINGLE CELL

Li-Ion BATTERY

4.2V

SINGLE CELL

Li-Ion BATTERY

OPTIONAL GLITCH

FILTER CAPACITOR

VOUT,TRIP POINT = 6V

INT

KILL

LTC2950-2

GND ONT OFFT

VIN

CONT*

0.033µF

COFFT*

0.033µF

VIN

LTC2950-1

GND ONT

2950 F08

TRACE

CAPACITANCE

PARASITICS

0.1µF

DETAILS OMITTED

FOR CLARITY

TRACE

INDUCTANCE

NOISE

INT

KILL

OFFT

VIN

Figure 7. PowerPath Control with 6V Undervoltage Detect

Figure 8. Noisy PB Trace

PB Pin in a Noisy Environment

The rugged PB pin is designed to operate in noisy envi-

ronments. 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.

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 ex-

ternal pull-up resistor unnecessary. Leakage current on

Typical applicaTions

LTC2950-1/LTC2950-2

295012fd

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

LTC2950-1/

LTC2950-2

GND

EXTERNAL BOARD

LEAKAGE CURRENT

100k

2.4V

10k

2950 F09

>2µA

PINS OMITTED

FOR CLARITY

IF EXTERNAL PARASITIC BOARD

LEAKAGE >2µA, USE EXTERNAL

PULL-UP RESISTOR

VIN

Figure 9. External Pull-Up Resistor on PB Pin

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).

Typical applicaTions

LTC2950-1/LTC2950-2

295012fd

package DescripTion

DDB Package

8-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1702 Rev B)

2.00 ±0.10

(2 SIDES)

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

0.40 ± 0.10

BOTTOM VIEW—EXPOSED PAD

0.56 ± 0.05

(2 SIDES)

0.75 ±0.05

R = 0.115

TYP

R = 0.05

TYP

2.15 ±0.05

(2 SIDES)

3.00 ±0.10

(2 SIDES)

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

0.200 REF

0 – 0.05

(DDB8) DFN 0905 REV B

0.25 ± 0.05

2.20 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

0.61 ±0.05

(2 SIDES)

1.15 ±0.05

0.70 ±0.05

2.55 ±0.05

PACKAGE

OUTLINE

0.25 ± 0.05

0.50 BSC

PIN 1

R = 0.20 OR

0.25 × 45°

CHAMFER

0.50 BSC

LTC2950-1/LTC2950-2

295012fd

package DescripTion

1.50 – 1.75

(NOTE 4)

2.80 BSC

0.22 – 0.36

8 PLCS (NOTE 3)

DATUM ‘A’

0.09 – 0.20

(NOTE 3)

TS8 TSOT-23 0710 REV A

2.90 BSC

(NOTE 4)

0.65 BSC

1.95 BSC

0.80 – 0.90

1.00 MAX 0.01 – 0.10

0.20 BSC

0.30 – 0.50 REF

PIN ONE ID

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

3.85 MAX

0.40

MAX

0.65

REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

1.4 MIN

2.62 REF

1.22 REF

TS8 Package

8-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1637 Rev A)

LTC2950-1/LTC2950-2

295012fd

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

How-

ever, 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.

revision hisTory

REV DATE DESCRIPTION PAGE NUMBER

D 02/11 Revised Typical Application.

Revised Absolute Maximum Ratings and Pin Configuration.

Updated Electrical Characteristics

Revised EN and EN pin descriptions in Pin Functions.

Updated Block Diagram

Revised Figures 5 and 6.

Updated Related Parts.

(Revision history begins at Rev D)

LTC2950-1/LTC2950-2

295012fd

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

 LINEAR TECHNOLOGY CORPORATION 2008

LT 0211 REV D • PRINTED IN USA

VIN

SHDN

VOUT

INT

KILL

LT1761-1.8

10k

910k

2950 F10

0.1µF

µP

1.8V

BATTERY

INT

KILL

LTC2950-1

GND ONT OFFT

CONT*

0.033µF

VIN

COFFT*

0.033µF

*OPTIONAL

Figure 10. Reverse Battery Protection

Typical applicaTion

relaTeD parTs

PART NUMBER DESCRIPTION COMMENTS

LTC2900 Programmable Quad Supply Monitor Adjustable RESET, 10-Lead MSOP and 3mm × 3mm DFN Packages

LTC2904/LTC2905 Pin-Programmable Dual Supply Monitors Adjustable RESET and Tolerance, 8-Lead SOT-23 and 3mm × 2mm DFN Packages

LTC4411 2.6A Low Loss Ideal Diode in ThinSOT No External MOSFET, Automatic Switching Between DC Sources

LTC4412HV PowerPath 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

LTC2951 Micropower Pushbutton On/Off Controller Adjustable Power-Off Timer

LTC2952 Pushbutton PowerPath Controller with

Supervisor

Automatic Low Loss Switchover Between DC Sources

LTC2953 Pushbutton On/Off Controller with Voltage

Monitoring

High Voltage Pushbutton Controller with 200ms Voltage Reset Monitor

LTC2954 Pushbutton On/Off Controller with µP Interrupt Allow Controlled Software System Shutdown