Datasheet

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LTC2951-1/LTC2951-2

295112fb

TYPICAL APPLICATION

APPLICATIONS

FEATURES DESCRIPTION

Pushbutton On/Off

Controller

The LTC

2951 is a micropower, wide input voltage range

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

button input which controls the toggling of an open-drain

enable output. The pushbutton turn OFF debounce time

is externally programmable, while the turn ON debounce

time is fixed at 128ms. A simple microprocessor interface

allows for proper system housekeeping prior to power-

down. Under system fault conditions, an adjustable KILL

timeout delay ensures proper power-down.

The LTC2951 operates over a 2.7V to 26.4V input voltage

range to accommodate a variety of input power supplies.

Very low quiescent current (6µA typical) makes the

LTC2951 ideally suited for battery powered applications.

Two versions of the part are available to accommodate

either positive or negative enable polarities. The parts

are available in 8-pin 3mm × 2mm DFN and ThinSOT

packages.

Portable Instrumentation Meters

Blade Servers

Portable Customer Service PDA

Desktop and Notebook Computers

Adjustable Pushbutton Debounce and Delay Timers

Low Supply Current: 6µA

Wide Operating Voltage Range: 2.7V to 26.4V

EN Output (LTC2951-1) Allows DC/DC Converter

Control

EN Output (LTC2951-2) Allows Circuit Breaker

Control

Simple Interface Allows Graceful µP Shutdown

High Input Voltage PB Pin with Internal Pull-Up

Resistor

±10kV ESD HBM on PB Input

Accurate 0.6V Threshold on KILL Comparator Input

8-Pin 3mm × 2mm DFN and ThinSOT

Packages

Turn-On Debounce

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.

OUT

2.7V TO 26.4V

INT

KILL

INT

KILL

LTC2951-1

KILLT

OFFT

DC/DC

BUCK

µP/µC

10k

2951 TA01

KILLT

0.033µF

OFFT

0.033µF

GND

SHDN**

*OPTIONAL

**SHDN INTERNALLY PULLED UP BY DC/DC

2V/DIV

25ms/DIV

2951 TA01b

128ms

Summary of content (20 pages)

PAGE 1
LTC2951-1/LTC2951-2 Pushbutton On/Off Controller FEATURES n n n n n n n n n n DESCRIPTION Adjustable Pushbutton Debounce and Delay Timers Low Supply Current: 6µA Wide Operating Voltage Range: 2.7V to 26.4V EN Output (LTC2951-1) Allows DC/DC Converter Control EN Output (LTC2951-2) Allows Circuit Breaker Control Simple Interface Allows Graceful µP Shutdown High Input Voltage PB Pin with Internal Pull-Up Resistor ±10kV ESD HBM on PB Input Accurate 0.
PAGE 2
LTC2951-1/LTC2951-2 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (VIN)................................... –0.3V to 33V Input Voltages PB.............................................................. –6V to 33V KILLT..................................................... –0.3V to 2.7V OFFT...................................................... –0.3V to 2.7V KILL .........................................................–0.3V to 7V Output Voltages INT.........................................................
PAGE 3
LTC2951-1/LTC2951-2 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) SYMBOL PARAMETER CONDITIONS VIN Supply Voltage Range Steady-State Operation l MIN IIN VIN Supply Current System Power-On, VIN = 2.7V to 24V l VUVL VIN Undervoltage Lockout VIN Falling l VUVL(HYST) VIN Undervoltage Lockout Hysteresis TYP 2.7 MAX UNITS 26.
PAGE 4
LTC2951-1/LTC2951-2 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Temperature Supply Current vs Supply Voltage 10 10 8 IVIN (µA) VIN = 3.3V 6 VIN = 2.7V 4 6 4 2 2 –25 0 25 50 TEMPERATURE (°C) 75 0 100 0 5 10 15 20 25 10000 TA = 25°C tDB, OFF + tOFFT (ms) tDB, OFF (ms) 30 20 10 15 VIN (V) 20 1000 100 25 10 30 1 100 10 OFFT EXTERNAL CAPACITOR (nF) tKILL, OFF DELAY (ms) 160 120 80 40 0 0 5 10 15 VIN (V) 20 25 2951 G07 20 25 VIN = 26.4V –3.0 VIN = 2.
PAGE 5
LTC2951-1/LTC2951-2 TYPICAL PERFORMANCE CHARACTERISTICS PB Voltage vs External PB Resistance to Ground PB Current vs PB Voltage –250 300 TA = 25°C VIN = 3.3V 250 PB VOLTAGE (mV) PB CURRENT (µA) –200 –150 –100 200 TA = 100°C 150 TA = 25°C TA = –45°C 100 –50 0 –10 VIN = 3.3V 50 –5 0 5 10 15 PB VOLTAGE (V) 20 25 0 30 0 5 10 15 20 EXTERNAL PB RESISTANCE TO GROUND (kΩ) 2951 G11 2951 G10 EN/EN VOL vs Current Load 0.8 300 0.6 200 0.4 100 0.
PAGE 6
LTC2951-1/LTC2951-2 PIN FUNCTIONS (TSOT-23/DFN) 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 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. KILLT (Pin 3/Pin 2): Additional, Adjustable KILL Turn-Off Delay Input (tKILL, OFF DELAY, ADDITIONAL).
PAGE 7
LTC2951-1/LTC2951-2 BLOCK DIAGRAM EN/EN VIN 2.7V TO 26.4V REGULATOR 2.4V 2.4V OSCILLATOR 100k KILL PB LOGIC 10µs FILTER DEBOUNCE 0.6V 0.
PAGE 8
LTC2951-1/LTC2951-2 TIMING DIAGRAMS tKILL(PW) KILL tKILL(PD) EN/EN 2951 TD01 PB PB & KILL IGNORED tDB, ON tKILL, ON BLANK EN (LTC2951-1) EN (LTC2951-2) 2951 TD02 Power-On Timing 295112fb 8
PAGE 9
LTC2951-1/LTC2951-2 TIMING DIAGRAMS PB PB IGNORED tDB, OFF t OFFT OFFT 16 CYCLES INT t KILL, OFF DELAY t KILL, OFF DELAY, ADDITIONAL KILLT 16 CYCLES EN (LTC2951-1) EN (LTC2951-2) 2951 TD03 Power-Off Timing, KILL > 0.
PAGE 10
LTC2951-1/LTC2951-2 APPLICATIONS INFORMATION Description Turn-Off The LTC2951 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 part incorporates all the flexible timing needed to debounce the pushbutton input (PB). The LTC2951 also provides a simple interface (INT output, KILL input) to allow a system to power on and power off in a controlled manner.
PAGE 11
LTC2951-1/LTC2951-2 APPLICATIONS INFORMATION Simplified Power-On/-Off Sequence Figure 1 shows a simplified LTC2951-1 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 128ms (t2–t1). Once EN goes high (t2), an internal 512ms blanking timer is started.
PAGE 12
LTC2951-1/LTC2951-2 APPLICATIONS INFORMATION 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 after the KILL turn-off (t KILL, OFF DELAY + t KILL, OFF DELAY, ADDITIONAL) timeout period. Once a system has finished performing its powerdown operations, it can set KILL low (t7) and thus immediately set EN low, terminating the KILL turn-off timer.
PAGE 13
LTC2951-1/LTC2951-2 APPLICATIONS INFORMATION DC/DC Turn-Off Blanking When the DC/DC converter is turned off, it can take a significant amount of time for its output to decay to ground. It is desirable to wait until the output of the DC/DC converter is near ground before allowing the user (via PB ) to restart the converter. This condition guarantees that the µP has always powered down completely before it is restarted. Figure 4 shows the µP turning power off.
PAGE 14
LTC2951-1/LTC2951-2 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.
PAGE 15
LTC2951-1/LTC2951-2 TYPICAL APPLICATIONS PowerPathTM Switching PB Pin in a Noisy Environment The EN open-drain output of the LTC2951-2 is designed to switch on/off an external power PFET. This allows a user to connect/disconnect a power supply (or battery) to its load by toggling the PB pin. Figure 7 shows the LTC2951-2 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.
PAGE 16
LTC2951-1/LTC2951-2 TYPICAL APPLICATIONS 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 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).
PAGE 17
LTC2951-1/LTC2951-2 PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ±0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.20 ±0.05 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 2.00 ±0.10 (2 SIDES) 0.56 ± 0.05 (2 SIDES) 0.75 ±0.05 0 – 0.05 4 0.25 ± 0.05 1 PIN 1 R = 0.20 OR 0.
PAGE 18
LTC2951-1/LTC2951-2 PACKAGE DESCRIPTION TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.40 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 0710 REV A NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2.
PAGE 19
LTC2951-1/LTC2951-2 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 01/11 Revised Features and Typical Application 1 Updated Pin Configuration 2 Revised Electrical Characteristics section 3 Revised Pin Functions section 6 Revised Block Diagram 7 Minor edit to Figure 1 11 Added C3 to Figure 6 14 Updated Figure 8 15 Updated Related Parts 20 295112fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
PAGE 20
LTC2951-1/LTC2951-2 TYPICAL APPLICATION 9V BATTERY + VIN R5 910k R8 1k VOUT LT1761-1.8 SHDN 1.8V C4 0.1µF VIN R1 10k EN LTC2951-1 INT INT PB KILL KILL GND KILLT OFFT CKILLT* 0.033µF COFFT* 0.033µF *OPTIONAL µP 2951 F10 Figure 10.