LTC4412IS6#TRPBF

LTC4412 Low Loss PowerPath™ Controller in ThinSOT Features Description Very Low Loss Replacement for Power Supply OR’ing Diodes nn Minimal External Components nn Automatic Switching Between DC Sources nn Simplifies Load Sharing with Multiple Batteries nn Low Quiescent Current: 11µA nn 3V to 28V AC/DC Adapter Voltage Range nn 2.5V to 28V Battery Voltage Range nn Reverse Battery Protection nn Drives Almost Any Size MOSFET for Wide Range of Current Requirements nn MOSFET Gate Protection Clamp nn Manual Control Input nn Low Profile (1mm) ThinSOT™ Package The LTC®4412 controls an external P-channel MOSFET to create a near ideal diode function for power switchover or load sharing. This permits highly efficient OR’ing of multiple power sources for extended battery life and low self-heating. When conducting, the voltage drop across the MOSFET is typically 20mV. For applications with a wall adapter or other auxiliary power source, the load is automatically disconnected from the battery when the auxiliary source is connected. Two or more LTC4412s may be interconnected to allow load sharing between multiple batteries or charging of multiple batteries from a single charger. nn Applications Cellular Phones Notebook and Handheld Computers nn Digital Cameras nn USB-Powered Peripherals nn Uninterruptible Power Supplies nn Logic Controlled Power Switch nn The wide supply operating range supports operation from one to six Li-Ion cells in series. The low quiescent current (11µA typical) is independent of the load current. The gate driver includes an internal voltage clamp for MOSFET protection. The STAT pin can be used to enable an auxiliary P-channel MOSFET power switch when an auxiliary supply is detected. This pin may also be used to indicate to a microcontroller that an auxiliary supply is connected. The control (CTL) input enables the user to force the primary MOSFET off and the STAT pin low. nn 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. The LTC4412 is available in a low profile (1mm) ThinSOT package. Typical Application LTC4412 vs Schottky Diode Forward Voltage Drop 1 WALL ADAPTER INPUT TO LOAD LTC4412 VIN SENSE GND GATE CTL STAT COUT VCC 470k 4412 F01 STATUS OUTPUT LOW WHEN WALL ADAPTER PRESENT CURRENT (A) BATTERY CELL(S) CONSTANT RON Figure 1. Automatic Switchover of Load Between a Battery and a Wall Adapter LTC4412 CONSTANT VOLTAGE 0 SCHOTTKY DIODE 0.02 FORWARD VOLTAGE (V) 0.5 4412 F01b 4412fb For more information www.linear.com/LTC4412 1 LTC4412 Absolute Maximum Ratings Pin Configuration (Note 1) Supply Voltage (VIN)................................... –14V to 36V Voltage from VIN to SENSE......................... – 28V to 28V Input Voltage CTL.........................................................– 0.3V to 36V SENSE..................................................... –14V to 36V Output Voltage GATE ...................... –0.3V to the Higher of VIN + 0.3V or SENSE + 0.3V STAT.......................................................– 0.3V to 36V Operating Junction Temperature Range (Note 2) ............................................ – 55°C to 150°C Storage Temperature Range....................–65°C to 150°C Lead Temperature (Soldering, 10 sec)................... 300°C TOP VIEW VIN 1 6 SENSE GND 2 5 GATE CTL 3 4 STAT S6 PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX = 150°C, θJA = 230°C/W Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4412ES6#PBF LTC4412ES6#TRPBF LTA2 6-Lead Plastic TSOT-23 –40°C to 85°C LTC4412IS6#PBF LTC4412IS6#TRPBF LTA2 6-Lead Plastic TSOT-23 –40°C to 85°C LTC4412HS6#PBF LTC4412HS6#TRPBF LTA2 6-Lead Plastic TSOT-23 –40°C to 150°C LTC4412MPS6#PBF LTC4412MPS6#TRPBF LTA2 6-Lead Plastic TSOT-23 –55°C to 150°C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4412ES6 LTC4412ES6#TR LTA2 6-Lead Plastic TSOT-23 –40°C to 85°C LTC4412IS6 LTC4412IS6#TR LTA2 6-Lead Plastic TSOT-23 –40°C to 85°C LTC4412HS6 LTC4412HS6#TR LTA2 6-Lead Plastic TSOT-23 –40°C to 150°C LTC4412MPS6 LTC4412MPS6#TR LTA2 6-Lead Plastic TSOT-23 –55°C to 150°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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/ 2 4412fb For more information www.linear.com/LTC4412 LTC4412 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, unless otherwise noted specifications are at TA = 25°C, VIN = 12V, CTL and GND = 0V. Current into a pin is positive and current out of a pin is negative. All voltages are referenced to GND, unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN VIN, VSENSE Operating Supply Range VIN and/or VSENSE Must Be in This Range for Proper Operation l IQFL Quiescent Supply Current at Low Supply While in Forward Regulation VIN = 3.6V. Measure Combined Current at VIN and SENSE Pins Averaged with VSENSE = 3.5V and VSENSE = 3.6V (Note 3) l IQFH Quiescent Supply Current at High Supply While in Forward Regulation VIN = 28V. Measure Combined Current at VIN and SENSE Pins Averaged with VSENSE = 27.9V and VSENSE = 28V (Note 3) l IQRL Quiescent Supply Current at Low Supply While in Reverse Turn-Off IQRH TYP 2.5 MAX UNITS 28 V 11 19 µA 15 26 µA VIN = 3.6V, VSENSE = 3.7V. Measure Combined Current of VIN and SENSE Pins 10 19 µA Quiescent Supply Current at High Supply While in Reverse Turn-Off VIN = 27.9V, VSENSE = 28V. Measure Combined Current of VIN and SENSE Pins 16 28 µA IQCL Quiescent Supply Current at Low Supply with CTL Active VIN = 3.6V, VSENSE = 0V, VCTL = 1V 7 13 µA IQCH Quiescent Supply Current at High Supply with CTL Active VIN = 28V, VSENSE = 0V, VCTL = 1V 12 20 µA ILEAK VIN and SENSE Pin Leakage Currents When Other Pin Supplies Power VIN = 28V, VSENSE = 0V; VSENSE = 28V, VIN = 0V VIN = 14V, VSENSE = –14V; VSENSE = 14V, VIN = –14V –3 0 1 µA PowerPath Controller VFR PowerPath Switch Forward Regulation Voltage VIN – VSENSE, 2.5V ≤ VIN ≤ 28V l 10 20 32 mV VRTO PowerPath Switch Reverse Turn-Off Threshold Voltage VSENSE – VIN, 2.5V ≤ VIN ≤ 28V l 10 20 32 mV –1 25 –2.5 50 –5 85 µA µA 6.3 7 7.7 V GATE and STAT Outputs IG(SRC) IG(SNK) GATE Active Forward Regulation Source Current Sink Current (Note 4) VG(ON) GATE Clamp Voltage Apply IGATE = 1µA, VIN = 12V, VSENSE = 11.9V, Measure VIN – VGATE VG(OFF) GATE Off Voltage Apply IGATE = – 5µA, VIN = 12V, VSENSE = 12.1V, Measure VSENSE – VGATE 0.13 0.25 V tG(ON) GATE Turn-On Time VGS < –3V, CGATE = 1nF (Note 5) 110 175 µs tG(OFF) GATE Turn-Off Time VGS > –1.5V, CGATE = 1nF (Note 6) 13 22 µs IS(OFF) STAT Off Current 2.5V ≤ VIN ≤ 28V (Note 7) l –1 0 1 µA IS(SNK) STAT Sink Current 2.5V ≤ VIN ≤ 28V (Note 7) l 6 10 17 µA tS(ON) STAT Turn-On Time (Note 8) 4.5 25 µs tS(OFF) STAT Turn-Off Time (Note 8) 40 75 µs VIL CTL Input Low Voltage 2.5V ≤ VIN ≤ 28V l 0.5 0.35 V VIH CTL Input High Voltage 2.5V ≤ VIN ≤ 28V l ICTL CTL Input Pull-Down Current 0.35V ≤ VCTL ≤ 28V HCTL CTL Hysteresis 2.5V ≤ VIN ≤ 28V CTL Input 0.9 0.635 1 3.5 135 V 5.5 µA mV 4412fb For more information www.linear.com/LTC4412 3 LTC4412 Electrical Characteristics 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: The LTC4412 is tested under pulsed load conditions such that TJ ≈ TA. The LTC4412E is guaranteed to meet performance specifications from 0°C to 85°C operating junction temperature range. Specifications over the –40°C to 85°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC4412I is guaranteed over the –40°C to 85°C operating junction temperature range. The LTC4412MP is tested and guaranteed over the –55°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes; operating lifetime is degraded for junction temperatures greater than 125°C. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD • ΘJA), where ΘJA = 230°C/W for the TSOT-23 package. 4 Note 3: This results in the same supply current as would be observed with an external P-channel MOSFET connected to the LTC4412 and operating in forward regulation. Note 4: VIN is held at 12V and GATE is forced to 10.5V. SENSE is set at 12V to measure the source current at GATE. SENSE is set at 11.9V to measure sink current at GATE. Note 5: VIN is held at 12V and SENSE is stepped from 12.2V to 11.8V to trigger the event. GATE voltage is initially VG(OFF). Note 6: VIN is held at 12V and SENSE is stepped from 11.8V to 12.2V to trigger the event. GATE voltage is initially internally clamped at VG(ON). Note 7: STAT is forced to VIN – 1.5V. SENSE is set at VIN – 0.1V to measure the off current at STAT. SENSE is set VIN + 0.1V to measure the sink current at STAT. Note 8: STAT is forced to 9V and VIN is held at 12V. SENSE is stepped from 11.8V to 12.2V to measure the STAT turn-on time defined when ISTAT reaches one half the measured IS(SNK). SENSE is stepped from 12.2V to 11.8V to measure the STAT turn-off time defined when ISTAT reaches one half the measured IS(SNK) . 4412fb For more information www.linear.com/LTC4412 LTC4412 Typical Performance Characteristics VFR vs Temperature and Supply Voltage Normalized Quiescent Supply Current vs Temperature VRTO vs Temperature and Supply Voltage 25 1.15 25 VIN = 2.5V VIN = 28V 20 CURRENT (µA) VRTO (mV) VFR (mV) 1.10 VIN = 28V 20 VIN = 2.5V 1.05 3.6V ≤ VIN ≤ 28V 1.00 15 –75 –25 25 75 125 TEMPERATURE (°C) 15 –75 175 –25 25 75 125 TEMPERATURE (°C) 4412 G01 –0.2 0.95 –75 175 –25 25 75 125 TEMPERATURE (°C) 4412 G03 4412 G02 ILEAK vs Temperature 7.05 175 VG(ON) vs Temperature 0.30 8V ≤ VIN ≤ 28V IGATE = 1µA VG(OFF) vs Temperature and IGATE 2.5V ≤ VIN ≤ 28V –0.3 VOLTAGE (V) VOLTAGE (V) CURRENT (µA) –0.25 6.95 0.20 0.10 –0.35 –0.4 –75 –25 25 75 125 TEMPERATURE (°C) 6.85 –75 175 –25 25 75 125 TEMPERATURE (°C) 4412 G04 13.0 3.6V ≤ VIN ≤ 28V CGATE = 1nF 94 –75 –25 25 75 125 TEMPERATURE (°C) 175 4412 G07 25 75 125 TEMPERATURE (°C) tG(OFF) vs Temperature 11.5 3.6V ≤ VIN ≤ 28V CGATE = 1nF –25 25 75 125 TEMPERATURE (°C) IS(SNK) vs Temperature and VIN VSTAT = VIN – 1.5V 12.5 12.0 –75 175 4412 G06 CURRENT (µA) tG(ON) vs Temperature 100 –25 4412 G05 TIME (µs) TIME (µs) 106 0.00 –75 175 IGATE = –10µA IGATE = –5µA IGATE = 0µA 175 4412 G08 11.0 VIN = 28V VIN = 2.5V 10.5 10.0 –75 –25 25 75 125 TEMPERATURE (°C) 175 4412 G09 4412fb For more information www.linear.com/LTC4412 5 LTC4412 Pin Functions VIN (Pin 1): Primary Input Supply Voltage. Supplies power to the internal circuitry and is one of two voltage sense inputs to the internal analog controller (The other input to the controller is the SENSE pin). This input is usually supplied power from a battery or other power source which supplies current to the load. This pin can be bypassed to ground with a capacitor in the range of 0.1µF to 10µF if needed to suppress load transients. STAT (Pin 4): Open-Drain Output Status Pin. When the SENSE pin is pulled above the VIN pin with an auxiliary power source by about 20mV or more, the reverse turnoff threshold (VRTO) is reached. The STAT pin will then go from an open state to a 10µA current sink (IS(SNK)). The STAT pin current sink can be used, along with an external resistor, to turn on an auxiliary P-channel power switch and/or signal the presence of an auxiliary power source to a microcontroller. GND (Pin 2): Ground. Provides a power return for all the internal circuits. GATE (Pin 5): Primary P-Channel MOSFET Power Switch Gate Drive Pin. This pin is directed by the power controller to maintain a forward regulation voltage (VFR) of 20mV between the VIN and SENSE pins when an auxiliary power source is not present. When an auxiliary power source is connected, the GATE pin will pull up to the SENSE pin voltage, turning off the primary P-channel power switch. CTL (Pin 3): Digital Control Input. A logical high input (VIH) on this pin forces the gate to source voltage of the primary P-channel MOSFET power switch to a small voltage (VGOFF). This will turn the MOSFET off and no current will flow from the primary power input at VIN if the MOSFET is configured so that the drain to source diode does not forward bias. A high input also forces the STAT pin to sink 10µA of current (IS(SNK)). If the STAT pin is used to control an auxiliary P-channel power switch, then a second active source of power, such as an AC wall adaptor, will be connected to the load (see Applications Information). An internal current sink will pull the CTL pin voltage to ground (logical low) if the pin is open. AUXILIARY SUPPLY – + – + PRIMARY SUPPLY – + Block Diagram SENSE (Pin 6): Power Sense Input Pin. Supplies power to the internal circuitry and is a voltage sense input to the internal analog controller (The other input to the controller is the VIN pin). This input is usually supplied power from an auxiliary source such as an AC adapter or back-up battery which also supplies current to the load. 1 6 VIN SENSE – + POWER SOURCE SELECTOR OUTPUT TO LOAD A1 POWER LINEAR GATE DRIVER AND VOLTAGE CLAMP VOLTAGE/CURRENT REFERENCE 0.5V GATE 5 VCC ON/OFF 3 CTL + STAT C1 3.5µA ANALOG CONTROLLER – 2 6 ON/OFF STATUS OUTPUT 4 10µA GND 4412 BD *DRAIN-SOURCE DIODE OF MOSFET For more information www.linear.com/LTC4412 4412fb LTC4412 Operation Operation can best be understood by referring to the Block Diagram, which illustrates the internal circuit blocks along with the few external components, and the graph that accompanies Figure 1. The terms primary and auxiliary are arbitrary and may be changed to suit the application. Operation begins when either or both power sources are applied and the CTL control pin is below the input low voltage of 0.35V (VIL). If only the primary supply is present, the Power Source Selector will power the LTC4412 from the VIN pin. Amplifier A1 will deliver a current to the Analog Controller block that is proportional to the voltage difference in the VIN and SENSE pins. While the voltage on SENSE is lower than VIN ­– 20mV (VFR), the Analog Controller will instruct the Linear Gate Driver and Voltage Clamp block to pull down the GATE pin voltage and turn on the external P-channel MOSFET. The dynamic pull-down current of 50µA (IG(SNK)) stops when the GATE voltage reaches ground or the gate clamp voltage. The gate clamp voltage is 7V (VG(ON)) below the higher of VIN or VSENSE. As the SENSE voltage pulls up to VIN ­– 20mV, the LTC4412 will regulate the GATE voltage to maintain a 20mV difference between VIN and VSENSE which is also the VDS of the MOSFET. The system is now in the forward regulation mode and the load will be powered from the primary supply. As the load current varies, the GATE voltage will be controlled to maintain the 20mV difference. If the load current exceeds the P-channel MOSFET’s ability to deliver the current with a 20mV VDS the GATE voltage will clamp, the MOSFET will behave as a fixed resistor and the forward voltage will increase slightly. While the MOSFET is on the STAT pin is an open circuit. When an auxiliary supply is applied, the SENSE pin will be pulled higher than the VIN pin through the external diode. The Power Source Selector will power the LTC4412 from the SENSE pin. As the SENSE voltage pulls above VIN ­– 20mV, the Analog Controller will instruct the Linear Gate Driver and Voltage Clamp block to pull the GATE voltage up to turn off the P-channel MOSFET. When the voltage on SENSE is higher than VIN ­+ 20mV (VRTO), the Analog Controller will instruct the Linear Gate Driver and Voltage Clamp block to rapidly pull the GATE pin voltage to the SENSE pin voltage. This action will quickly finish turning off the external P-channel MOSFET if it hasn’t already turned completely off. For a clean transition, the reverse turn-off threshold has hysteresis to prevent uncertainty. The system is now in the reverse turn-off mode. Power to the load is being delivered through the external diode and no current is drawn from the primary supply. The external diode provides protection in case the auxiliary supply is below the primary supply, sinks current to ground or is connected reverse polarity. During the reverse turn-off mode of operation the STAT pin will sink 10µA of current (IS(SNK)) if connected. Note that the external MOSFET is wired so that the drain to source diode will momentarily forward bias when power is first applied to VIN and will become reverse biased when an auxiliary supply is applied. When the CTL (control) input is asserted high, the external MOSFET will have its gate to source voltage forced to a small voltage VG(OFF) and the STAT pin will sink 10µA of current if connected. This feature is useful to allow control input switching of the load between two power sources as shown in Figure 4 or as a switchable high side driver as shown in Figure 7. A 3.5µA internal pull-down current (ICTL) on the CTL pin will insure a low level input if the pin should become open. 4412fb For more information www.linear.com/LTC4412 7 LTC4412 Applications Information Introduction The system designer will find the LTC4412 useful in a variety of cost and space sensitive power control applications that include low loss diode OR’ing, fully automatic switchover from a primary to an auxiliary source of power, microcontroller controlled switchover from a primary to an auxiliary source of power, load sharing between two or more batteries, charging of multiple batteries from a single charger and high side power switching. External P-Channel MOSFET Transistor Selection Important parameters for the selection of MOSFETs are the maximum drain-source voltage VDS(MAX), threshold voltage VGS(VT) and on-resistance RDS(ON). The maximum allowable drain-source voltage, VDS(MAX), must be high enough to withstand the maximum drainsource voltage seen in the application. The maximum gate drive voltage for the primary MOSFET is set by the smaller of the VIN supply voltage or the internal clamping voltage VG(ON). A logic level MOSFET is commonly used, but if a low supply voltage limits the gate voltage, a sub-logic level threshold MOSFET should be considered. The maximum gate drive voltage for the auxiliary MOSFET, if used, is determined by the external resistor connected to the STAT pin and the STAT pin sink current. As a general rule, select a MOSFET with a low enough RDS(ON) to obtain the desired VDS while operating at full load current and an achievable VGS. The MOSFET normally operates in the linear region and acts like a voltage controlled resistor. If the MOSFET is grossly undersized, it can enter the saturation region and a large VDS may result. However, the drain-source diode of the MOSFET, if forward biased, will limit VDS. A large VDS, combined with the load current, will likely result in excessively high MOSFET power dissipation. Keep in mind that the LTC4412 will regulate the forward voltage drop across the primary MOSFET at 20mV if RDS(ON) is low enough. The required RDS(ON) can be calculated by dividing 0.02V by the load current in amps. Achieving forward regulation will minimize power loss and heat dissipation, but it is not a necessity. 8 If a forward voltage drop of more than 20mV is acceptable then a smaller MOSFET can be used, but must be sized compatible with the higher power dissipation. Care should be taken to ensure that the power dissipated is never allowed to rise above the manufacturer’s recommended maximum level. The auxiliary MOSFET power switch, if used, has similar considerations, but its VGS can be tailored by resistor selection. When choosing the resistor value consider the full range of STAT pin current (IS(SNK) ) that may flow through it. VIN and SENSE Pin Bypass Capacitors Many types of capacitors, ranging from 0.1µF to 10µF and located close to the LTC4412, will provide adequate VIN bypassing if needed. Voltage droop can occur at the load during a supply switchover because some time is required to turn on the MOSFET power switch. Factors that determine the magnitude of the voltage droop include the supply rise and fall times, the MOSFET’s characteristics, the value of COUT and the load current. Droop can be made insignificant by the proper choice of COUT, since the droop is inversely proportional to the capacitance. Bypass capacitance for the load also depends on the application’s dynamic load requirements and typically ranges from 1µF to 47µF. In all cases, the maximum droop is limited to the drain source diode forward drop inside the MOSFET. Caution must be exercised when using multilayer ceramic capacitors. Because of the self resonance and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions such as connecting a supply input to a hot power source. To reduce the Q and prevent these transients from exceeding the LTC4412’s absolute maximum voltage rating, the capacitor’s ESR can be increased by adding up to several ohms of resistance in series with the ceramic capacitor. Refer to Application Note 88. The selected capacitance value and capacitor’s ESR can be verified by observing VIN and SENSE for acceptable voltage transitions during dynamic conditions over the full load current range. This should be checked with each power source as well. Ringing may indicate an incorrect bypass capacitor value and/or too low an ESR. 4412fb For more information www.linear.com/LTC4412 LTC4412 applications information VIN and SENSE Pin Usage Since the analog controller’s thresholds are small (±20mV), the VIN and SENSE pin connections should be made in a way to avoid unwanted I • R drops in the power path. Both pins are protected from negative voltages. GATE Pin Usage The GATE pin controls the external P-channel MOSFET connected between the VIN and SENSE pins when the load current is supplied by the power source at VIN. In this mode of operation, the internal current source, which is responsible for pulling the GATE pin up, is limited to a few microamps (IG(SRC)). If external opposing leakage currents exceed this, the GATE pin voltage will reach the clamp voltage (VGON) and VDS will be smaller. The internal current sink, which is responsible for pulling the GATE pin down, has a higher current capability (IG(SNK)). With an auxiliary supply input pulling up on the SENSE pin and exceeding the VIN pin voltage by 20mV (VRTO), the device enters the reverse turn-off mode and a much stronger current source is available to oppose external leakage currents and turn off the MOSFET (VGOFF). While in forward regulation, if the on resistance of the MOSFET is too high to maintain forward regulation, the GATE pin will maximize the MOSFET’s VGS to that of the clamp voltage (VGON). The clamping action takes place between the higher of VIN or VSENSE and the GATE pin. Status Pin Usage During normal operation, the open-drain STAT pin can be biased at any voltage between ground and 28V regardless of the supply voltage to the LTC4412. It is usually connected to a resistor whose other end connects to a voltage source. In the forward regulation mode, the STAT pin will be open (IS(OFF)). When a wall adaptor input or other auxiliary supply is connected to that input, and the voltage on SENSE is higher than VIN ­+ 20mV (VRTO), the system is in the reverse turn-off mode. During this mode of operation the STAT pin will sink 10µA of current (IS(SNK)). This will result in a voltage change across the resistor, depending on the resistance, which is useful to turn on an auxiliary P‑channel MOSFET or signal to a microcontroller that an auxiliary power source is connected. External leakage currents, if significant, should be accounted for when determining the voltage across the resistor when the STAT pin is either on or off. Control Pin Usage This is a digital control input pin with low threshold voltages (VIL,VIH) for use with logic powered from as little as 1V. During normal operation, the CTL pin can be biased at any voltage between ground and 28V, regardless of the supply voltage to the LTC4412. A logical high input on this pin forces the gate to source voltage of the primary P‑channel MOSFET power switch to a small voltage (VGOFF). This will turn the MOSFET off and no current will flow from the primary power input at VIN if the MOSFET is configured so that the drain to source diode is not forward biased. The high input also forces the STAT pin to sink 10µA of current (IS(SNK)). See the Typical Applications for various examples on using the STAT pin. A 3.5µA internal pulldown current (ICTL) on the CTL pin will insure a logical low level input if the pin should be open. Protection Most of the application circuits shown provide some protection against supply faults such as shorted, low or reversed supply inputs. The fault protection does not protect shorted supplies but can isolate other supplies and the load from faults. A necessary condition of this protection is for all components to have sufficient breakdown voltages. In some cases, if protection of the auxiliary input (sometimes referred to as the wall adapter input) is not required, then the series diode or MOSFET may be eliminated. Internal protection for the LTC4412 is provided to prevent damaging pin currents and excessive internal self heating during a fault condition. These fault conditions can be a result of any LTC4412 pins shorted to ground or to a power source that is within the pin’s absolute maximum voltage limits. Both the VIN and SENSE pins are capable of being taken significantly below ground without current drain or damage to the IC (see Absolute Maximum Voltage Limits). This feature allows for reverse-battery condition without current drain or damage. This internal protection is not designed to prevent overcurrent or overheating of external components. 4412fb For more information www.linear.com/LTC4412 9 LTC4412 Typical Applications Automatic PowerPath Control The applications shown in Figures 1, 2 and 3 are automatic ideal diode controllers that require no assistance from a microcontroller. Each of these will automatically connect the higher supply voltage, after accounting for certain diode forward voltage drops, to the load with application of the higher supply voltage. Figure 1 illustrates an application circuit for automatic switchover of a load between a battery and a wall adapter or other power input. With application of the battery, the load will initially be pulled up by the drain-source diode of the P-channel MOSFET. As the LTC4412 comes into action, it will control the MOSFET’s gate to turn it on and reduce the MOSFET’s voltage drop from a diode drop to 20mV. The system is now in the low loss forward regulation mode. Should the wall adapter input be applied, the Schottky diode will pull up the SENSE pin, connected to the load, above the battery voltage and the LTC4412 will turn the MOSFET off. The STAT pin will then sink current indicating an auxiliary input is connected. The battery is now supplying no load current and all the load current flows through the Schottky diode. A silicon diode could be used instead of the Schottky, but will result in higher power dissipation and heating due to the higher forward voltage drop. AUXILIARY P-CHANNEL MOSFET * WALL ADAPTER INPUT BATTERY CHARGER TO LOAD LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT COUT 1 470k *DRAIN-SOURCE DIODE OF MOSFET 4412 F02 STATUS OUTPUT DROPS WHEN A WALL ADAPTER IS PRESENT Figure 2. Automatic Switchover of Load Between a Battery and a Wall Adapter with Auxiliary P-Channel MOSFET for Lowest Loss 10 Figure 3 illustrates an application circuit for the automatic switchover of a load between a battery and a wall adapter in the comparator mode. It also shows how a battery charger can be connected. This circuit differs from Figure 1 in the way the SENSE pin is connected. The SENSE pin is connected directly to the auxiliary power input and not the load. This change forces the LTC4412’s control circuitry to operate in an open-loop comparator mode. While the battery supplies the system, the GATE pin voltage will be forced to its lowest clamped potential, instead of being regulated to maintain a 20mV drop across the MOSFET. This has the advantages of minimizing power loss in the MOSFET by minimizing its RON and not having the influence of a linear control loop’s dynamics. A possible disadvantage is if the auxiliary input ramps up slow enough the load voltage will initially droop before rising. This is due to the WALL ADAPTER INPUT PRIMARY P-CHANNEL MOSFET * BATTERY CELL(S) Figure 2 illustrates an application circuit for automatic switchover of load between a battery and a wall adapter that features lowest power loss. Operation is similar to Figure 1 except that an auxiliary P-channel MOSFET replaces the diode. The STAT pin is used to turn on the MOSFET once the SENSE pin voltage exceeds the battery voltage by 20mV. When the wall adapter input is applied, the drain-source diode of the auxiliary MOSFET will turn on first to pull up the SENSE pin and turn off the primary MOSFET followed by turning on of the auxiliary MOSFET. Once the auxiliary MOSFET has turned on the voltage drop across it can be very low depending on the MOSFET’s characteristics. BATTERY CELL(S) P-CHANNEL MOSFET * TO LOAD LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT 1 COUT VCC 470k *DRAIN-SOURCE DIODE OF MOSFET 4412 F03 STATUS OUTPUT IS LOW WHEN A WALL ADAPTER IS PRESENT Figure 3. Automatic Switchover of Load Between a Battery and a Wall Adapter in Comparator Mode 4412fb For more information www.linear.com/LTC4412 LTC4412 typical applications SENSE pin voltage rising above the battery voltage and turning off the MOSFET before the Schottky diode turns on. The factors that determine the magnitude of the voltage droop are the auxiliary input rise time, the type of diode used, the value of COUT and the load current. Ideal Diode Control with a Microcontroller Figure 4 illustrates an application circuit for microcontroller monitoring and control of two power sources. The microcontroller’s analog inputs, perhaps with the aid of a resistor voltage divider, monitors each supply input and commands the LTC4412 through the CTL input. Back-toback MOSFETs are used so that the drain-source diode will not power the load when the MOSFET is turned off (dual MOSFETs in one package are commercially available). With a logical low input on the CTL pin, the primary input supplies power to the load regardless of the auxiliary voltage. When CTL is switched high, the auxiliary input will power the load whether or not it is higher or lower than the primary power voltage. Once the auxiliary is on, the primary power can be removed and the auxiliary will continue to power the load. Only when the primary voltage is higher than the auxiliary voltage will taking CTL low switch back to the primary power, otherwise AUXILIARY POWER SOURCE INPUT Load Sharing Figure 5 illustrates an application circuit for dual battery load sharing with automatic switchover of load from batteries to wall adapter. Whichever battery can supply the higher voltage will provide the load current until it is discharged to the voltage of the other battery. The load will then be shared between the two batteries according to the capacity of each battery. The higher capacity battery will provide proportionally higher current to the load. When a wall adapter input is applied, both MOSFETs will turn off and no load current will be drawn from the batteries. The STAT pins provide information as to which input is supplying the load current. This concept can be expanded to more power inputs. WALL ADAPTER INPUT AUXILIARY P-CHANNEL MOSFETS * the auxiliary stays connected. When the primary power is disconnected and VIN falls below VLOAD, it will turn on the auxiliary MOSFET if CTL is low, but VLOAD must stay up long enough for the MOSFET to turn on. At a minimum, COUT capacitance must be sized to hold up VLOAD until the transition between the sets of MOSFETs is complete. Sufficient capacitance on the load and low or no capacitance on VIN will help ensure this. If desired, this can be avoided by use of a capacitor on VIN to ensure that VIN falls more slowly than VLOAD. * TO LOAD BAT1 * LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT 1 470k MICROCONTROLLER PRIMARY P-CHANNEL MOSFETS * * TO LOAD LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT BAT2 1 LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT 1 4412 F04 *DRAIN-SOURCE DIODE OF MOSFET VCC 470k * COUT 0.1µF PRIMARY POWER SOURCE INPUT COUT WHEN BOTH STATUS LINES ARE HIGH, THEN BOTH BATTERIES ARE SUPPLYING LOAD CURRENTS. WHEN BOTH STATUS LINES ARE LOW THEN WALL ADAPTER IS PRESENT VCC 470k *DRAIN-SOURCE DIODE OF MOSFET Figure 4. Microcontroller Monitoring and Control of Two Power Sources STATUS IS HIGH WHEN BAT1 IS SUPPLYING LOAD CURRENT 4412 F05 STATUS IS HIGH WHEN BAT2 IS SUPPLYING LOAD CURRENT Figure 5. Dual Battery Load Sharing with Automatic Switchover of Load from Batteries to Wall Adapter 4412fb For more information www.linear.com/LTC4412 11 LTC4412 typical applications Multiple Battery Charging High Side Power Switch Figure 6 illustrates an application circuit for automatic dual battery charging from a single charger. Whichever battery has the lower voltage will receive the charging current until both battery voltages are equal, then both will be charged. When both are charged simultaneously, the higher capacity battery will get proportionally higher current from the charger. For Li-Ion batteries, both batteries will achieve the float voltage minus the forward regulation voltage of 20mV. This concept can apply to more than two batteries. The STAT pins provide information as to which batteries are being charged. For intelligent control, the CTL pin input can be used with a microcontroller and back-to-back MOSFETs as shown in Figure 4. This allows complete control for disconnection of the charger from either battery. Figure 7 illustrates an application circuit for a logic controlled high side power switch. When the CTL pin is a logical low, the LTC4412 will turn on the MOSFET. Because the SENSE pin is grounded, the LTC4412 will apply maximum clamped gate drive voltage to the MOSFET. When the CTL pin is a logical high, the LTC4412 will turn off the MOSFET by pulling its gate voltage up to the supply input voltage and thus deny power to the load. The MOSFET is connected with its source connected to the power source. This disables the drain-source diode from supplying voltage to the load when the MOSFET is off. Note that if the load is powered from another source, then the drain-source diode can forward bias and deliver current to the power supply connected to the VIN pin. * BATTERY CHARGER INPUT LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT 1 0.1µF TO LOAD OR PowerPath BAT1 CONTROLLER LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT 1 SUPPLY INPUT VCC 470k * P-CHANNEL MOSFET * STATUS IS HIGH WHEN BAT1 IS CHARGING TO LOAD OR PowerPath BAT2 CONTROLLER TO LOAD LTC4412 6 VIN SENSE 2 5 GND GATE 3 4 CTL STAT COUT 1 0.1µF LOGIC INPUT 4412 F07 *DRAIN-SOURCE DIODE OF MOSFET VCC 470k 4412 F06 STATUS IS HIGH WHEN BAT2 IS CHARGING Figure 7. Logic Controlled High Side Power Switch *DRAIN-SOURCE DIODE OF MOSFET Figure 6. Automatic Dual Battery Charging from Single Charging Source 12 4412fb For more information www.linear.com/LTC4412 LTC4412 Revision History (Revision history begins at Rev B) REV DATE DESCRIPTION B 02/15 Added H and MP-grade options. PAGE NUMBER Throughout 4412fb 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. For more information www.linear.com/LTC4412 13 LTC4412 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. S6Package Package S6 6-LeadPlastic PlasticTSOT-23 TSOT-23 6-Lead (Reference (ReferenceLTC LTCDWG DWG##05-08-1636) 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 2.80 BSC 1.4 MIN 3.85 MAX 2.62 REF 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 1.90 BSC 0.09 – 0.20 (NOTE 3) S6 TSOT-23 0302 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 Related Parts PART NUMBER DESCRIPTION COMMENTS LTC1473 Dual PowerPath Switch Driver Switches and Isolates Sources Up to 30V LTC1479 PowerPath Controller for Dual Battery Systems Complete PowerPath Management for Two Batteries; DC Power Source, Charger and Backup LTC1558/LTC1559 Back-Up Battery Controller with Programmable Output Adjustable Backup Voltage from 1.2V NiCd Button Cell, Includes Boost Converter LT®1579 300mA Dual Input Smart Battery Back-Up Regulator Maintains Output Regulation with Dual Inputs, 0.4V Dropout at 300mA LTC1733/LTC1734 Monolithic Linear Li-Ion Chargers Thermal Regulation, No External MOSFET/Sense Resistor LTC1960 Dual Battery Charger Selector with SPI Complete Dual Battery Charger/Selector System, 36-Lead SSOP LTC1998 2.5µA, 1% Accurate Programmable Battery Detector Adjustable Trip Voltage/Hysteresis, ThinSOT LTC4350 Hot Swappable Load Share Controller Allows N + 1 Redundant Supply, Equally Loads Multiple Power Supplies Connected in Parallel LTC4410 USB Power Manager in ThinSOT Enables Simultaneous Battery Charging and Operation of USB Component Peripheral Devices 14 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC4412 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC4412 4412fb LT 0215 REV B • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2002