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LTC2954

2954fb

Pushbutton On/Off

Controller with µP Interrupt

The LTC

2954 is a pushbutton on/off controller that

manages system power via a pushbutton interface. An

enable output toggles system power while an interrupt

output provides debounced pushbutton status. The inter-

rupt output can be used in menu driven applications to

request a system power-down. A power kill input allows

a microprocessor or system to reset the enable output,

effectively powering down the system. Independently

adjustable on and off timers allow dependable pushbutton

control of the enable output and resistance to accidental

toggling of system power.

The LTC2954 operates over a wide 2.7V to 26.4V input volt-

age range to accommodate a wide variety of input power

supplies. Very low quiescent current (6μA typical) makes

the LTC2954 ideally suited for battery powered applications.

Two versions of the part are available to accommodate

either positive or negative enable polarities.

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

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

are the property of their respective owners.

Pushbutton PowerPath™ Control

Portable Instrumentation Meters

Blade Servers

Portable Customer Service PDA

Desktop and Notebook Computers

Adjustable Power On/Off Timers

Low Supply Current: 6μA

Wide Operating Voltage Range: 2.7V to 26.4V

Low Leakage EN Output (LTC2954-1) Allows DC/DC

Converter Control

High Voltage EN Output (LTC2954-2) 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

TYPICAL APPLICATION

FEATURES DESCRIPTION

APPLICATIONS

Pushbutton On/Off with Interrupt

OUT

INT

KILL

INT

KILL

LTC2954-2

ONT

PDT

DC/DC

μP/μC

10k

PDT

= 6.4 SECONDS

100k

2954 TA01a

1μF

GND

TURN-ON PULSE

TURNS ON STAYS ON

INTERRUPT INTERRUPT

TURNS OFF

SHORT PULSE

LONG PULSE

INT

2954 TA01b

Summary of content (18 pages)

PAGE 1
LTC2954 Pushbutton On/Off Controller with µP Interrupt FEATURES DESCRIPTION n The LTC®2954 is a pushbutton on/off controller that manages system power via a pushbutton interface. An enable output toggles system power while an interrupt output provides debounced pushbutton 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 system to reset the enable output, effectively powering down the system.
PAGE 2
LTC2954 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (VIN) .................................. –0.3V to 33V Input Voltages PB ............................................................ –6V to 33V ONT ...................................................... –0.3V to 2.7V PDT ....................................................... –0.3V to 2.7V KILL ......................................................... –0.3V to 7V Output Voltages INT ......................................................... –0.
PAGE 3
LTC2954 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 IIN VIN Supply Current System Power-On, VIN = 2.7V to 24V l VIN Falling l VUVL VIN Undervoltage Lockout VUVL(HYST) VIN Undervoltage Lockout Hysteresis MIN TYP 2.7 6 MAX UNITS 26.
PAGE 4
LTC2954 ELECTRICAL CHARACTERISTICS thus turning off system power. This time delay does not include t DB,ON or t ONT. Note 4: To manually force an immediate release of the EN/EN pin, the pushbutton input must be held low for at least tPD,MIN (internal default power-down timer) + t PDT (adjustable by placing external capacitor at PDT pin).
PAGE 5
LTC2954 TYPICAL PERFORMANCE CHARACTERISTICS PB Power-Down Debounce Time (tPD,MIN + tPDT) vs PDT External Capacitance Internal Default PB Power-Down Debounce Time (t PD,MIN) vs VIN PDT Pull-Up Current vs Temperature 10000 70 –3.4 TA = 25°C VIN = 3.3V 60 tPD, MIN + tPDT (ms) tPD, MIN (ms) 40 30 20 PDT PULL-UP CURRENT (μA) TA = 25°C 50 1000 100 –3.2 VIN = 26.4V –3.0 VIN = 2.7V –2.8 10 0 10 0 10 5 15 VIN (V) 20 25 30 100 10 PDT EXTERNAL CAPACITANCE (nF) 1 300 TA = 25°C VIN = 3.
PAGE 6
LTC2954 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 and INT outputs. An internal 100k pull-up resistor connects to an internal 1.9V bias voltage. The rugged PB input withstands ±10kV ESD HBM and can be pulled up to 26.4V externally without consuming extra current. ONT (Pin 3/Pin 2): Turn-On Time Input.
PAGE 7
LTC2954 BLOCK DIAGRAM EN (–1) EN (–2) HIGH VOLTAGE 1.5k VIN REGULATOR 2.7V TO 26.4V 2.4V 2.4V 29V ZENER KILL OSCILLATOR 100k PB LOGIC 10μS FILTER DEBOUNCE 0.6V 0.
PAGE 8
LTC2954 TIMING DIAGRAMS PB PB & KILL IGNORED tDB, ON tKILL, ON BLANK tONT ONT 16 CYCLES EN (LTC2954-1) 2954 TD02 Power-On Timing PB PB IGNORED tDB, OFF t < tPDT PDT tPD,MIN INT tINT,MIN 2954 TD03 Off Interrupt Timing, PB Pressed and Released, Enable Remains Active PB IGNORED PB tDB, OFF 16 CYCLES PDT tPD,MIN tPDT INT tINT,MAX EN (LTC2954-1) 2954 TD04 Forced Off, Power-Down Timing, PB Pressed and Held Low for t > (tPD,MIN + tPDT) 2954fb 8
PAGE 9
LTC2954 APPLICATIONS INFORMATION Description The LTC2954 is a pushbutton on/off controller that provides control of system power via a pushbutton interface. An enable output toggles system power while an interrupt output provides debounced pushbutton 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 system to release the enable output, effectively powering down the system.
PAGE 10
LTC2954 APPLICATIONS INFORMATION t1 t2 PB t3 t4 t5 t6 t8 t9 PB IGNORED PB & KILL IGNORED t KILL, ON BLANK tDB, ON t7 tDB, OFF ONT tONT PDT tPD, MIN INT t < tPDT KILL μP DRIVES KILL LOW XXX DON'T CARE EN 2954 F01 Figure 1. Simplified Power On/Off Sequence for LTC2954-1. μP Asserts KILL After an Interrupt tABORT PB tDB,ON + tONT 512ms INTERNAL TIMER POWER-ON TIMING POWER TURNED OFF EN μP FAILED TO SET KILL HIGH KILL 2954 F02 Figure 2.
PAGE 11
LTC2954 APPLICATIONS INFORMATION low 512ms after it went high. Note that the LTC2954 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 LTC2954 monitors PB and KILL for a turn-off command while consuming only 6μA of supply current.
PAGE 12
LTC2954 APPLICATIONS INFORMATION LTC2954-1, LTC2954-2 Versions The LTC2954-1 (high true EN) and LTC2954-2 (low true EN) differ only by the polarity of the high voltage (33V ABS MAX), enable pin. The LTC2954-1 EN pin is a low leakage high true open drain output designed to drive the shutdown pin of DC/DC converters. The LTC2954-2 is a low leakage, low true open drain enable output designed to drive the gate of an external PFET. The LTC2954-2 provides a user manual power path control.
PAGE 13
LTC2954 TYPICAL APPLICATIONS PFET through a resistive divider. The KILL pin serves as a voltage monitor. When VOUT drops below 6V, causing a KILL voltage below VKILL(TH), the EN pin becomes an open circuit 30μs later. Since the PDT pin is open-circuited, the power-down debounce time defaults to 64ms. width detected is 30μs. If there are glitches on the resistor pull-up voltage that are wider than 30μs and transition below 0.6V, then an appropriate bypass capacitor should be connected to the KILL pin.
PAGE 14
LTC2954 TYPICAL APPLICATIONS External Pull-Up Resistor On PB Reverse Battery Protection 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 15
LTC2954 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) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 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 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 16
LTC2954 PACKAGE DESCRIPTION TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637 Rev A) 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. DRAWING NOT TO SCALE 3.
PAGE 17
LTC2954 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 2/11 Revised Pin Descriptions for EN and EN pins 6 Revised notes for Figures 5 and 6 in Typical Applications 12 2954fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 18
LTC2954 TYPICAL APPLICATION 9V BATTERY VIN + R5 910k R8 1k VOUT LT1761-1.8 SHDN 1.8V VIN C4 0.1μF R1 10k EN INT INT PB KILL KILL GND ONT PDT LTC2954-1 CONT* 0.033μF μP CPDT* 1μF *OPTIONAL 2954 TA02 Figure 10.