LTC2951-1/LTC2951-2 Push Button On/Off Controller U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Adjustable Push Button Debounce and Delay Timers Low Supply Current: 6µA Wide Operating Voltage Range: 2.7V to 26V EN Output (LTC2951-1) Allows DC/DC Converter Control ⎯E⎯N Output (LTC2951-2) Allows Circuit Breaker Control Simple Interface Allows Graceful µP Shut Down High Input Voltage ⎯P⎯B Pin with Internal Pull Up Resistor ±10kV ESD HBM on ⎯P⎯B Input Accurate 0.6V Threshold on ⎯K⎯I⎯L⎯L Comparator Input 8-Pin 3mm × 2mm DFN and ThinSOTTM Packages U APPLICATIO S ■ ■ ■ Portable Instrumentation Meters Blade Servers Portable Customer Service PDA Desktop and Notebook Computers The LTC2951 operates over a 2.7V to 26V 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. , 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. U ■ The LTC®2951 is a micropower, wide input voltage range push button ON/OFF controller. The part contains a push button input which controls the toggling of an open drain enable output. The push button 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 ⎯K⎯I⎯L⎯L timeout delay ensures proper power down. TYPICAL APPLICATIO Turn On Debounce VIN 3V – 26V VIN VOUT DC/DC BUCK SHDN EN VIN R1 10k EN LTC2951-1 2V/DIV INT INT PB KILL KILL GND KILLT OFFT µP/µC PB 128ms 2951 TA01 CKILLT* 0.033µF 25ms/DIV COFFT* 0.033µF 2951 TA01b *OPTIONAL 295112fa 1 LTC2951-1/LTC2951-2 W W U W ABSOLUTE AXI U RATI GS (Note 1) Supply Voltage (VIN) ..................................– 0.3V to 33V Input Voltages ⎯P⎯B ............................................................– 6V to 33V KILLT ....................................................– 0.3V to 2.7V OFFT .....................................................– 0.3V to 2.7V ⎯K⎯I⎯L⎯L .........................................................– 0.3V to 7V Output Voltages ⎯I⎯N⎯T .........................................................– 0.3V to 10V EN/⎯E⎯N ....................................................– 0.3V to 10V Operating Temperature Range LTC2951C-1 .............................................. 0°C to 70°C LTC2951C-2 .............................................. 0°C to 70°C LTC2951I-1 .......................................... – 40°C to 85°C LTC2951I-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 U W U PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW GND 1 KILLT 2 PB 3 VIN 4 9 8 INT 7 EN/EN 6 OFFT 5 KILL 8 KILL 7 OFFT 6 EN/EN 5 INT VIN 1 PB 2 KILLT 3 GND 4 TS8 PACKAGE 8-LEAD PLASTIC TSOT-23 DDB8 PACKAGE 8-LEAD (3mm × 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 140°C/W TJMAX = 125°C, θJA = 165°C/W EXPOSED PAD (PIN 9) UNCONNECTED ORDER PART NUMBER DDB PART* MARKING ORDER PART NUMBER TS8 PART* MARKING LTC2951CDDB-1 LTC2951CDDB-2 LTC2951IDDB-1 LTC2951IDDB-2 LBTB LBTD LBTB LBTD LTC2951CTS8-1 LTC2951CTS8-2 LTC2951ITS8-1 LTC2951ITS8-2 LTBTC LTBTF LTBTC LTBTF Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult factory for parts specified with wider operating temperature ranges. * The temperature grade is identified by a label on the shipping container. 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 26.4V, unless otherwise noted. (Note 2) SYMBOL VIN IIN VUVL VUVL(HYST) PARAMETER Supply Voltage Range VIN Supply Current VIN Undervoltage Lockout VIN Undervoltage Lockout Hysteresis CONDITIONS Steady State Operation System Power On, VIN = 2.7V to 24V VIN Falling ● MIN 2.7 ● ● ● 2.2 50 TYP 6 2.3 300 MAX 26.4 12 2.4 600 UNITS V µA V mV 295112fa 2 LTC2951-1/LTC2951-2 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 26.4V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN V⎯P⎯B(MIN, MAX) ⎯P⎯B Voltage Range Single-Ended ● –1 I⎯P⎯B ⎯P⎯B Input Current 2.5V < V⎯P⎯B < 26.4V V⎯P⎯B = 1V V⎯P⎯B = 0.6V ● ● ● –1 –3 TYP MAX UNITS 26.4 V –6 –9 ±1 –12 –15 µA µA µA Push Button Pin (⎯P⎯B) V⎯P⎯B(VTH) ⎯P⎯B Input Threshold ⎯P⎯B Falling ● 0.6 0.8 1 V V⎯P⎯B(VOC) ⎯P⎯B Open Circuit Voltage I⎯P⎯B = –1µA ● 1 1.6 2 V Timing Pins (KILLT, OFFT) IKILLT, OFFT(PU) KILLT/OFFT Pull Up Current VKILLT, OFFT = 0V ● –2.4 –3 –3.6 µA IKILLT, OFFT(PD) KILLT/OFFT Pull Down Current VKILLT, OFFT = 1.3V ● 2.4 3 3.6 µA tDB, ON Turn On Debounce Time ⎯P⎯B Falling → Enable Asserted ● 100 128 163 ms tDB, OFF Internal Turn Off Debounce Time OFFT Pin Float, ⎯P⎯B Falling → ⎯I⎯N⎯T Falling ● 26 32 41 ms ● 9 11.5 13.5 ms ±1 µA 0.11 0.4 V 0.63 V tOFFT Additional Adjustable Turn Off Time COFFT = 1500pF µP Handshake Pins (⎯I⎯N⎯T, ⎯K⎯I⎯L⎯L) I⎯I⎯N⎯T(LKG) ⎯I⎯N⎯T Leakage Current V⎯ I⎯N⎯T = 3V ● V⎯I⎯N⎯T(VOL) ⎯I⎯N⎯T Output Voltage Low I⎯ I⎯N⎯T = 3mA ● V⎯K⎯I⎯L⎯L(TH) ⎯K⎯I⎯L⎯L Input Threshold Voltage ⎯K⎯I⎯L⎯L Falling ● 0.57 0.6 ● 10 30 V⎯K⎯I⎯L⎯L(HYST) ⎯K⎯I⎯L⎯L Input Threshold Hysteresis I⎯K⎯I⎯L⎯L(LKG) ⎯K⎯I⎯L⎯L Leakage Current t ⎯K⎯I⎯L⎯L(PW) ⎯K⎯I⎯L⎯L Minimum Pulse Width t ⎯K⎯I⎯L⎯L(PD) ⎯K⎯I⎯L⎯L Propagation Delay ⎯K⎯I⎯L⎯L Falling → Enable Released ● t ⎯K⎯I⎯L⎯L, ON BLANK ⎯K⎯I⎯L⎯L Turn On Blanking (Note 3) ⎯K⎯I⎯L⎯L = Low, Enable Asserted → Enable Released ● 400 t ⎯K⎯I⎯L⎯L, OFF DELAY Internal ⎯K⎯I⎯L⎯L Turn Off Delay (Note 4) KILLT Pin Float, ⎯K⎯I⎯L⎯L = High, ⎯I⎯N⎯T Asserted → Enable Released ● t ⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL Additional Adjustable ⎯K⎯I⎯L⎯L Turn Off CKILLT = 1500pF Delay (Note 4) tEN/⎯E⎯N, Lock Out EN/⎯E⎯N Lock Out Time (Note 5) IEN/⎯E⎯N(LKG) EN/⎯E⎯N Leakage Current VEN/⎯E⎯N(VOL) EN/⎯E⎯N Voltage Output Low ● V ⎯K⎯I⎯L⎯L = 0.6V ● 50 mV ±0.1 µA 30 µs 30 µs 512 650 ms 100 128 163 ms ● 9 11.5 13.5 ms Enable Released → Enable Asserted ● 200 256 325 ms VEN/ ⎯E⎯N = 1V, Sink Current Off ● ±0.1 µA IEN/ ⎯E⎯N = 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 ⎯K⎯I⎯L⎯L 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 ⎯K⎯I⎯L⎯L and ⎯P⎯B inputs are ignored during this period. If ⎯K⎯I⎯L⎯L 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. 0.11 Note 4: The internal ⎯K⎯I⎯L⎯L turn off delay (t⎯K⎯I⎯L⎯L, OFF DELAY) is the default delay from the initiation of a power off sequence (⎯I⎯N⎯T falling, ⎯K⎯I⎯L⎯L = high), to the release of the enable output. The additional, adjustable ⎯K⎯I⎯L⎯L turn off delay (t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL) uses an optional external capacitor (CKILLT) to provide extra delay from ⎯I⎯N⎯T falling to the release of the enable output. If the ⎯K⎯I⎯L⎯L input switches low at any time during ⎯K⎯I⎯L⎯L turn off delay, enable is released, thus turning off system power. 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. ⎯P⎯B is ignored during this lock out time. This time delay does not include tDB, ON. 295112fa 3 LTC2951-1/LTC2951-2 U W TYPICAL PERFOR A CE CHARACTERISTICS 10 10 8 TA = 25°C 8 VIN = 2.7V 4 2 160 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 10000 tDB, OFF + tOFFT (ms) tDB, OFF (ms) 40 30 20 1000 100 10 0 20 25 10 30 1 100 10 OFFT EXTERNAL CAPACITOR (nF) 2951 G06 tKILL, OFF DELAY (ms) 160 120 80 40 0 5 10 15 VIN (V) 20 25 30 2951 G03 20 25 VIN = 26.4V –3.0 VIN = 2.7V –2.8 –25 0 25 50 TEMPERATURE (°C) 75 100 2951 G08 KILLT Pull-Down Current vs Temperature 10000 –3.4 1000 100 10 30 –3.2 –2.6 –50 1000 KILLT PULL-DOWN CURRENT (µA) TA = 25°C 15 VIN (V) OFFT Pull-Down Current vs Temperature ⎯K⎯I⎯L⎯L Turn Off Delay vs KILLT External Capacitor 200 10 2951 G07 tKILL, OFF DELAY + tKILL, OFF DELAY, ADDITIONAL (ms) Internal Default ⎯K⎯I⎯L⎯L Turn Off Delay (t⎯K⎯I⎯L⎯L, OFF DELAY) vs VIN 0 5 –3.4 TA = 25°C VIN = 3.3V 15 VIN (V) 0 2951 G14 Turn Off Debounce Time (tDB, OFF + tOFFT) vs OFFT External Capacitor TA = 25°C 10 0 30 2951 G02 Internal Default Turn Off Debounce Time (tDB, OFF) vs VIN 5 80 VIN (V) 2951 G01 0 120 40 OFFT PULL-DOWN CURRENT (µA) IVIN (µA) 200 TA = 25°C VIN = 26.4V 50 Turn On Debounce Time (tDB, ON) vs VIN Supply Current vs Supply Voltage Supply Current vs Temperature 1 100 10 KILLT EXTERNAL CAPACITOR (nF) 1000 2951 G04 –3.2 VIN = 26.4V –3.0 VIN = 2.7V –2.8 –2.6 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 2951 G05 295112fa 4 LTC2951-1/LTC2951-2 U W TYPICAL PERFOR A CE CHARACTERISTICS ⎯P⎯B Voltage vs External ⎯P⎯B Resistance to Ground ⎯P⎯B Current vs ⎯P⎯B Voltage –250 300 TA = 25°C VIN = 3.3V VIN = 3.3V 250 PB VOLTAGE (mV) PB CURRENT (µA) –200 –150 –100 –50 0 –10 200 TA = 100°C 150 TA = 25°C TA = –45°C 100 50 0 –5 0 5 10 15 PB VOLTAGE (V) 20 25 0 5 10 15 20 EXTERNAL PB RESISTANCE TO GROUND (kΩ) 30 2951 G09 500 EN/⎯E⎯N VOL vs Current Load 1.0 EN (LTC2951-1) Voltage vs VIN 0.6 200 0.4 100 0.2 ⎯E⎯N (LTC2951-2) Voltage vs VIN TA = 25°C 100k PULL-UP FROM EN TO VIN 3 EN (V) 300 EN (V) EN/EN VOLTAGE (mV) 0.8 4 TA = 25°C 100k PULL-UP FROM EN TO VIN TA = 25°C VIN = 3.3V 400 2951 G10 2 1 0 0 2 6 8 4 EN/EN CURRENT LOAD (mA) 10 0 0 0 1 2 3 4 2951 G11 0 1 2 3 4 VIN (V) VIN (V) 2951 G12 2951 G13 295112fa 5 LTC2951-1/LTC2951-2 U U U PI FU CTIO S (TSOT-23/DFN) VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V. ⎯ ⎯B (Pin 2/Pin 3): Push Button Input. Connecting ⎯P⎯B to P ground through a momentary switch provides on/off control via the EN/⎯E⎯N pin. An internal 100k pull-up resistor connects to an internal 1.9V bias voltage. The rugged ⎯P⎯B input can be pulled up to 26.4V externally without consuming extra current. KILLT (Pin 3/Pin 2): Additional, Adjustable ⎯K⎯I⎯L⎯L Turn Off Delay Input (t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL). A capacitor to ground provides additional delay time (beyond the internal default 128ms, t⎯K⎯I⎯L⎯L, OFF DELAY) from ⎯I⎯N⎯T falling to the automatic release of the enable output. The ⎯K⎯I⎯L⎯L turn off delay feature ensures the release of the enable pin under system fault conditions, such as the µP not responding to the LTC2951 interrupt signal (⎯I⎯N⎯T low). GND (Pin 4/Pin 1): Device Ground. I⎯ ⎯N⎯T (Pin 5/Pin 8): Open Drain Interrupt Output. After a push button turn-off event is detected (tDB, OFF + tOFFT), the LTC2951 interrupts the system (µP) by bringing the ⎯I⎯N⎯T pin low. Once the system finishes its power down and housekeeping tasks, it sets ⎯K⎯I⎯L⎯L low, which in turn releases the enable output. If at the end of the power down timer period (t⎯K⎯I⎯L⎯L, OFF DELAY + t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL) ⎯K⎯I⎯L⎯L is still high, the enable output is released immediately. ⎯I⎯N⎯T may optionally be tied to ⎯K⎯I⎯L⎯L to release the enable output immediately after the turn-off event has been detected (⎯I⎯N⎯T low). EN (LTC2951-1, Pin 6/Pin 7): Open Drain Enable Output. This pin is intended to enable system power. EN goes high after a valid ⎯P⎯B turn on event (tDB, ON). EN goes low if: a) ⎯K⎯I⎯L⎯L is not driven high within 512ms of the initial valid ⎯P⎯B power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low during normal operation, or c) a second valid ⎯P⎯B event (power turn-off) is detected. The operating range for this pin is 0V to 10V. A 100k pull-up is recommended if not available in the DC/DC converter. ⎯E⎯N (LTC2951-2, Pin 6/Pin 7): Open Drain Enable Output. This pin is intended to enable system power. ⎯E⎯N is asserted low after a valid ⎯P⎯B turn-on event (tDB, ON). ⎯E⎯N releases high if: a) ⎯K⎯I⎯L⎯L is not driven high within 512ms of the initial valid ⎯P⎯B power turn-on event, b) ⎯K⎯I⎯L⎯L is driven low during normal operation, or c) a second valid ⎯P⎯B event (power turn-off) is detected. The operating range of this pin is 0V to 10V. A 100k pull-up is recommended if not available in the DC/DC converter. OFFT (Pin 7/Pin 6): Additional Adjustable Turn Off Time Input (tOFFT). A capacitor to ground determines the additional time (beyond the internal default 32ms, tDB, OFF) that the ⎯P⎯B pin must be held low before initiating a power down sequence (⎯I⎯N⎯T falling). Floating this pin results in a default turn off debounce time of 32ms. ⎯K⎯I⎯L⎯L (Pin 8/Pin 5): ⎯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 (t⎯K⎯I⎯L⎯L, 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 voltage monitor input. Exposed Pad (Pin 9): Exposed Pad may be left open or connected to device ground. 295112fa 6 LTC2951-1/LTC2951-2 W BLOCK DIAGRA 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 2951 BD KILLT OFFT W UW TI I G DIAGRA S tKILL(PW) KILL tKILL(PD) EN/EN 2951 TD01 295112fa 7 LTC2951-1/LTC2951-2 W UW TI I G DIAGRA S PB PB & KILL IGNORED tKILL, ON BLANK tDB, ON EN (LTC2951-1) EN (LTC2951-2) 2951 TD02 Power On Timing PB PB IGNORED tDB, OFF tOFFT OFFT 16 CYCLES INT tKILL, OFF DELAY tKILL, OFF DELAY, ADDITIONAL KILLT 16 CYCLES EN (LTC2951-1) EN (LTC2951-2) 2951 TD03 Power Off Timing, ⎯K⎯I⎯L⎯L > 0.6V 295112fa 8 LTC2951-1/LTC2951-2 U W U U APPLICATIO S I FOR ATIO Description ⎯K⎯I⎯L⎯L Turn Off Delay The LTC2951 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 part incorporates all the flexible timing needed to debounce the push button input (⎯P⎯B). The LTC2951 also provides a simple interface (⎯I⎯N⎯T output, ⎯K⎯I⎯L⎯L input) to allow a system to power on and power off in a controlled manner. The wide input voltage range allows a system designer to operate from single cell to multi-cell battery stacks. Very low quiescent current makes the LTC2951 ideal for continuously monitoring the On/Off push button of a handheld device. The LTC2951 provides a failsafe feature that allows the user to turn off system power (via ⎯P⎯B) under system fault conditions. During a normal power down sequence, the LTC2951 first interrupts the µP by setting ⎯I⎯N⎯T low. The µP then performs power down and housekeeping tasks and drives ⎯K⎯I⎯L⎯L low when done. The LTC2951 releases the enable output, thus turning off system power. The ⎯K⎯I⎯L⎯L turn off timer starts when ⎯I⎯N⎯T is driven low. If the µP fails to respond during this timeout period, the enable output will automatically release. The default power down timeout period is 128ms (t⎯K⎯I⎯L⎯L, OFF DELAY), which can be extended by placing an optional capacitor on the KILLT pin (t⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL). The following equation describes the additional power down timeout period. CKILLT is the KILLT external capacitor: Turn On When power is first applied to the LTC2951, the part initializes the output pins. Any DC/DC converters connected to the EN/⎯E⎯N pin will therefore be off. To assert the enable output, ⎯P⎯B must be held low for a minimum of 128ms (tDB, ON). Once the enable output is asserted, any DC/DC converters connected to this pin are turned on. The ⎯K⎯I⎯L⎯L input from the µP is ignored during the succeeding 512ms blanking time (t ⎯K⎯I⎯L⎯L, ON BLANK). This blanking time represents the maximum time required to power up the DC/DC converter and the µP. If ⎯K⎯I⎯L⎯L 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, ⎯P⎯B 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 ⎯P⎯B 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 ⎯P⎯B has been validly pressed, ⎯I⎯N⎯T is switched low. This alerts the µP to perform its power down and housekeeping tasks. CKILLT = 1.56e-4 [µF/ms] • (tK⎯ I⎯ L⎯ L⎯ , OFF DELAY, ADDITIONAL – 1ms) Note that ⎯K⎯I⎯L⎯L can be driven low (thereby releasing the enable output) at any time after t⎯K⎯I⎯L⎯L, ON BLANK period. Simplified Power On/Off Sequence Figure 1 shows a simplified LTC2951-1 power on and power off sequence. A high to low transition on ⎯P⎯B (t1) initiates the power on sequence. This diagram does not show any bounce on ⎯P⎯B. In order to assert the enable output, the ⎯P⎯B pin must stay low continuously (⎯P⎯B high resets timers) for 128ms (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 ⎯K⎯I⎯L⎯L 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 LTC2951 does not sample ⎯K⎯I⎯L⎯L and ⎯P⎯B until after the 512ms internal timer has expired. The reason ⎯P⎯B 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 ⎯P⎯B pin is then debounced with an internal 32ms timer. The system has now properly powered on and the LTC2951 monitors ⎯P⎯B 295112fa 9 LTC2951-1/LTC2951-2 U U W U APPLICATIO S I FOR ATIO t1 t2 PB t3 t4 t5 t6 PB & KILL IGNORED tDB, ON t7 PB IGNORED tKILL, ON BLANK < tKILL, OFF DELAY tDB, OFF tOFFT OFFT INT KILL EN 2951 F01 Figure 1. Simplified Power On/Off Sequence for LTC2951-1 tABORT PB tDB, ON 512ms INTERNAL TIMER POWER ON TIMING POWER TURNED OFF EN µP FAILED TO SET KILL HIGH KILL 2951 F02 Figure 2. Aborted Power On Sequence for LTC2951-1 295112fa 10 LTC2951-1/LTC2951-2 U W U U APPLICATIO S I FOR ATIO and ⎯K⎯I⎯L⎯L (for a turnoff command) while consuming only 6µA of supply current. A high to low transition on ⎯P⎯B (t5) initiates the power off sequence. ⎯P⎯B must stay low continuously (⎯P⎯B 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 (⎯I⎯N⎯T) is set, signifying that EN will be switched low after the ⎯K⎯I⎯L⎯L turn off (t ⎯K⎯I⎯L⎯L, OFF DELAY + t ⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL) timeout period. Once a system has finished performing its power down operations, it can set ⎯K⎯I⎯L⎯L low (t7) and thus immediately set EN low, terminating the ⎯K⎯I⎯L⎯L turn off timer. The release of the ⎯P⎯B pin is then debounced with an internal 32ms timer. The system is now in its reset state: where the LTC2951 is in low power mode (6µA). ⎯P⎯B is monitored for a high to low transition. Aborted Power On Sequence The power on sequence is aborted when the ⎯K⎯I⎯L⎯L 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 ⎯K⎯I⎯L⎯L 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 normally, the µP can turn off power by setting ⎯K⎯I⎯L⎯L low, as shown in Figure 3. At time t ⎯K⎯I⎯L⎯L, ⎯K⎯I⎯L⎯L 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 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 ⎯P⎯B) 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. After a low on ⎯K⎯I⎯L⎯L releases enable, ⎯P⎯B is ignored during the internal 256ms timer period. This is shown as tEN/⎯E⎯N, LOCKOUT in Figure 4. LTC2951-1, LTC2951-2 Versions The LTC2951-1 (high true EN) and LTC2951-2 (low true ⎯E⎯N) differ only by the polarity of the EN/⎯E⎯N pin. Both versions allow the user to extend the amount of time that the ⎯P⎯B must be held low in order to begin a valid power off sequence. An external capacitor placed on the OFFT pin adds additional time to the turn off debounce time. If no capacitor is placed on the OFFT pin, then the turn off debounce time is given by an internally fixed 32ms timer. Both versions of the LTC2951 provide extendable ⎯K⎯I⎯L⎯L turn off timer, t ⎯K⎯I⎯L⎯L, OFF DELAY, ADDITIONAL, by connecting an optional external capacitor on the KILLT pin. The default ⎯K⎯I⎯L⎯L turn off delay time is 128ms, t ⎯K⎯I⎯L⎯L, OFF DELAY. tEN/EN, LOCKOUT PB POWER ON tKILL PB PB & KILL IGNORED DC/DC TURNS OFF PB & KILL IGNORED PB BLANKING PB IGNORED 256ms DC/DC TURNS OFF EN EN µP SETS KILL LOW KILL µP SETS KILL LOW XXX DON’T CARE KILL XXX DON’T CARE 2951 F04 2951 F03 Figure 3. µP Turns Off Power (LTC2951-1) Figure 4. DC/DC Turn Off Blanking (LTC2951-1) 295112fa 11 LTC2951-1/LTC2951-2 U U W U APPLICATIO S I FOR ATIO High Voltage Pins The VIN and ⎯P⎯B pins can operate at voltages up to 26.4V. ⎯P⎯B can, additionally, operate below ground (–6V) without ⎯ B ⎯ has an ESD HBM rating of ±10kV. latching up the device. P If the push button switch connected to ⎯P⎯B 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 LTC2951 ⎯P⎯B pin, parasitic capacitances may couple onto the high impedance ⎯P⎯B input. Additionally, parasitic series inductance may cause unpredictable ringing at the ⎯P⎯B pin. Placing a 5k resistor from the ⎯P⎯B pin to the push button switch would mitigate parasitic inductance problems. Placing a 0.1µF capacitor on the ⎯P⎯B pin would lessen the impact of parasitic capacitive coupling. U TYPICAL APPLICATIO S Voltage Monitoring with ⎯K⎯I⎯L⎯L Input The ⎯K⎯I⎯L⎯L pin can be used as a voltage monitor. Figure 5 shows an application where the ⎯K⎯I⎯L⎯L 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 ⎯K⎯I⎯L⎯L 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 ⎯K⎯I⎯L⎯L comparator. The DC/DC converter shown has an internal pull-up current on its ⎯S⎯H⎯D⎯N pin. A pull-up resistor on EN is thus not needed. Operation Without µP Figure 6 shows how to connect the ⎯K⎯I⎯L⎯L 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 below 0.6V, then an appropriate bypass capacitor should be connected to the ⎯K⎯I⎯L⎯L pin. VIN VIN 9V 9V VIN VIN 3.3V VOUT LT1767-3.3 LT1767-3.3 SHDN SHDN 5.4V THRESHOLD C4 0.1µF 3.3V VOUT R3 806k 1% VIN EN LTC2951-1 R2 100k 1% R1 100k R1 10k INT INT PB KILL GND KILLT OFFT C4 0.1µF VIN EN LTC2951-1 INT + µP KILL (OPEN DRAIN) PB KILL GND KILLT OFFT C3* 0.01µF 2951 F05 CKILLT* 0.033µF CKILLT* 0.033µF COFFT* 0.033µF *OPTIONAL Figure 5. Input Voltage Monitoring with ⎯K⎯I⎯L⎯L Input COFFT* 0.033µF *OPTIONAL 2951 F06 Figure 6. No µP Application 295112fa 12 LTC2951-1/LTC2951-2 U TYPICAL APPLICATIO S Power Path Switching ⎯P⎯B Pin in a Noisy Environment The ⎯E⎯N 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 ⎯P⎯B pin. Figure 7 shows the LTC2951-2 controlling a two cell Li-Ion battery application. The ⎯I⎯N⎯T and ⎯K⎯I⎯L⎯L pins are connected to the output of the PFET through a resistor divider. The ⎯K⎯I⎯L⎯L pin serves as a voltage monitor. When VOUT drops below 6V, the ⎯E⎯N pin is open circuited 30µs later. The rugged ⎯P⎯B pin is designed to operate in noisy environments. Transients below ground (>–6V) and above VIN ⎯ ⎯B pin. Additionally, (<33V) will not damage the rugged P ⎯ ⎯ the PB pin can withstand ESD HBM strikes up to ±10kV. In order to keep external noise from coupling inside the ⎯ ⎯B pin. A LTC2951, place an R-C network close to the P 5k resistor and a 0.1µF capacitor should suffice for most noisy applications (see Figure 8). VOUT M1 R5 100K 4.2V SINGLE CELL Li-Ion BATTERY R1 909k 1% + C4 0.1µF CERAMIC 4.2V SINGLE CELL Li-Ion BATTERY VOUT,TRIP POINT = 6V + VIN EN LTC2951-2 INT PB KILL GND KILLT OFFT CKILLT* 0.033µF OPEN DRAIN OUTPUT OPTIONAL GLITCH FILTER CAPACITOR VTH = 0.6V INPUT R4 100k 1% C3* 0.1µF COFFT* 0.033µF *OPTIONAL 2951 F07 Figure 7. Power Path Control with 6V Under Voltage Detect VIN PARASITICS TRACE CAPACITANCE R6 5k EN VIN PB LTC2951-1 INT KILLT OFFT NOISE TRACE INDUCTANCE C5 0.1µF KILL GND DETAILS OMITTED FOR CLARITY 2951 F08 Figure 8. Filtering for Noisy ⎯P⎯B Traces 295112fa 13 LTC2951-1/LTC2951-2 U TYPICAL APPLICATIO S External Pull-Up Resistor on ⎯P⎯B Reverse Battery Protection ⎯ ⎯B pin makes an exAn internal pull-up resistor on the P ternal pull-up resistor unnecessary. Leakage current on ⎯ ⎯B board trace, however, will affect the open circuit the P voltage on the ⎯P⎯B pin. If the leakage is too large (>2µA), the ⎯P⎯B 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). To protect the LTC2951 from a reverse battery connection, place a 1k resistor (R8) in series with the VIN pin (see Figure 10). VIN VIN LTC2951-1/ LTC2951-2 2.4V R7 10k 100k PB EXTERNAL BOARD LEAKAGE CURRENT >2µA GND PINS OMITTED FOR CLARITY 2951 F09 IF EXTERNAL PARASITIC BOARD LEAKAGE >2µA, USE EXTERNAL PULL-UP RESISTOR Figure 9. External Pull-Up Resistor on ⎯P⎯B Pin 295112fa 14 LTC2951-1/LTC2951-2 U PACKAGE DESCRIPTIO DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702) 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 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.56 ± 0.05 (2 SIDES) 0.75 ±0.05 0.200 REF 0.50 BSC 2.20 ±0.05 (2 SIDES) 1 (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) 0 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 4 0.25 ± 0.05 PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER 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 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 295112fa 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 LTC2951-1/LTC2951-2 U TYPICAL APPLICATIO VIN 9V BATTERY + 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 µP CKILLT* 0.033µF COFFT* 0.033µF *OPTIONAL 2951 F10 Figure 10. Reverse Battery Protection Using R8 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC2900 Programmable Quad Supply Monitor Adjustable ⎯R⎯E⎯S⎯E⎯T, 10-Lead MSOP and 3mm x 3mm DFN Packages LTC2904/2905 Pin-Programmable Dual Supply Monitors Adjustable ⎯R⎯E⎯S⎯E⎯T and Tolerance, 8-Lead SOT-23 and 3mm × 2mm DFN Packages LTC2950 Micropower Push Button On/Off Controller High Voltage Push Button Controller with µP Interface and Adjustable ON Time 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 295112fa 16 Linear Technology Corporation LT/LWI 0706 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005