LTC2950-1/LTC2950-2 Push Button On/Off Controller FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 ■ ■ ■ ■ 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 295012fb 1 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 295012fb 2 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. 295012fb 3 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 295012fb 4 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 295012fb 5 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. 295012fb 6 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 295012fb 7 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 295012fb 8 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. 295012fb 9 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 295012fb 10 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) 295012fb 11 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 295012fb 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 295012fb 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 p0.05 (2 SIDES) 3.00 p0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 p0.10 8 0.70 p0.05 2.55 p0.05 1.15 p0.05 PACKAGE OUTLINE 0.25 p0.05 0.50 BSC 2.20 p0.05 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 2.00 p0.10 (2 SIDES) 0.56 p0.05 (2 SIDES) 0.75 p0.05 0 – 0.05 4 0.25 p0.05 1 PIN 1 R = 0.20 OR 0.25 s 45° CHAMFER (DDB8) DFN 0905 REV B 0.50 BSC 2.15 p0.05 (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 ●