LT1158 Half Bridge N-Channel Power MOSFET Driver FEATURES n n n n n n n n n n n n DESCRIPTION Drives Gate of Top Side MOSFET Above V+ Operates at Supply Voltages from 5V to 30V 150ns Transition Times Driving 3000pF Over 500mA Peak Driver Current Adaptive Non-Overlap Gate Drives Continuous Current Limit Protection Auto Shutdown and Retry Capability Internal Charge Pump for DC Operation Built-In Gate Voltage Protection Compatible with Current-Sensing MOSFETs TTL/CMOS Input Levels Fault Output Indication A single input pin on the LT®1158 synchronously controls two N-channel power MOSFETs in a totem pole configuration. Unique adaptive protection against shoot-through currents eliminates all matching requirements for the two MOSFETs. This greatly eases the design of high efficiency motor control and switching regulator systems. A continuous current limit loop in the LT1158 regulates short-circuit current in the top power MOSFET. Higher start-up currents are allowed as long as the MOSFET VDS does not exceed 1.2V. By returning the FAULT output to the enable input, the LT1158 will automatically shut down in the event of a fault and retry when an internal pull-up current has recharged the enable capacitor. APPLICATIONS n n n n n n An on-chip charge pump is switched in when needed to turn on the top N-channel MOSFET continuously. Special circuitry ensures that the top side gate drive is safely maintained in the transition between PWM and DC operation. The gate-to-source voltages are internally limited to 14.5V when operating at higher supply voltages. PWM of High Current Inductive Loads Half Bridge and Full Bridge Motor Control Synchronous Step-Down Switching Regulators Three-Phase Brushless Motor Drive High Current Transducer Drivers Battery-Operated Logic-Level MOSFETs L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5365118. TYPICAL APPLICATION 24V Top and Bottom Gate Waveforms 1N4148 BOOST DR + 10μF BOOST V+ T GATE DR V+ T GATE FB 0.1μF IRFZ34 + 500μF LOW ESR T SOURCE PWM 0Hz TO 100kHz SENSE+ INPUT + LT1158 + 1μF ENABLE FAULT B GATE DR BIAS 0.01μF RSENSE 0.015Ω SENSE– – LOAD VIN = 24V RL = 12Ω IRFZ34 1158 TA02 B GATE FB GND LT1158 TA01 1158fb 1 LT1158 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (Pins 2, 10) ......................................36V Boost Voltage (Pin 16) ..............................................56V Continuous Output Currents (Pins 1, 9, 15) .........100mA Sense Voltages (Pins 11, 12) .................. –5V to V+ + 5V Top Source Voltage (Pin 13) ................... –5V to V+ + 5V Boost to Source Voltage (V16 – V13) ........ –0.3V to 20V Operating Temperature Range LT1158C................................................... 0°C to 70°C LT1158I ................................................ –40°C to 85°C Junction Temperature (Note 2) LT1158C............................................................ 125°C LT1158I ............................................................. 150°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec.) ................. 300°C PIN CONFIGURATION TOP VIEW BOOST DR 1 TOP VIEW BOOST DR 1 16 BOOST V+ 2 15 T GATE DR 16 BOOST V+ 2 15 T GATE DR BIAS 3 14 T GATE FB BIAS 3 14 T GATE FB ENABLE 4 13 T SOURCE ENABLE 4 13 T SOURCE FAULT 5 12 SENSE+ FAULT 5 12 SENSE+ INPUT 6 11 SENSE– INPUT 6 11 SENSE– GND 7 10 V+ B GATE FB 8 9 B GATE DR GND 7 B GATE FB 8 10 V+ 9 B GATE DR SW PACKAGE 16-LEAD PLASTIC (WIDE) SO θJA = 110°C/W N PACKAGE 16-LEAD PLASTIC DIP θJA = 70°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LT1158CN#PBF PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1158CN#TRPBF 16-Lead Plastic DIP 0°C to 70°C LT1158IN#PBF LT1158IN#TRPBF 16-Lead Plastic DIP –40°C to 85°C LT1158CSW#PBF LT1158CSW#TRPBF 16-Lead Plastic (Wide) SO 0°C to 70°C LT1158ISW#PBF LT1158ISW#TRPBF 16-Lead Plastic (Wide) SO –40°C to 85°C LEAD BASED FINISH TAPE AND REEL PACKAGE DESCRIPTION TEMPERATURE RANGE LT1158CN LT1158CN#TR 16-Lead Plastic DIP 0°C to 70°C LT1158IN LT1158IN#TR 16-Lead Plastic DIP –40°C to 85°C PART MARKING* LT1158CSW LT1158CSW#TR 16-Lead Plastic (Wide) SO 0°C to 70°C LT1158ISW LT1158ISW#TR 16-Lead Plastic (Wide) SO –40°C to 85°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/ 1158fb 2 LT1158 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Test Circuit, V+ = V16 = 12V, V11 = V12 = V13 = 0V, Pins 1 and 4 open, Gate Feedback pins connected to Gate Drive pins unless otherwise specified. LT1158I SYMBOL I2 + I10 LT1158C PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX DC Supply Current (Note 2) V+ = 30V, V16 = 15V, V4 = 0.5V V+ = 30V, V16 = 15V, V6 = 0.8V V+ = 30V, V16 = 15V, V6 = 2V 4.5 8 2.2 7 13 3 10 18 4.5 8 2.2 7 13 3 10 18 mA mA mA 3 4.5 3 4.5 mA 0.8 1.4 2 0.8 1.4 2 V 5 15 5 15 μA V+ = V13 = 30V, V16 = 45V, V6 = 0.8V UNITS I16 Boost Current V6 Input Threshold I6 Input Current V6 = 5V l V4 Enable Low Threshold V6 = 0.8V, Monitor V9 l 0.9 1.15 1.4 0.85 1.15 1.4 V ΔV4 Enable Hysteresis V6 = 0.8V, Monitor V9 l 1.3 1.5 1.7 1.2 1.5 1.8 V l I4 Enable Pullup Current V4 = 0V l 15 25 35 15 25 35 μA V15 Charge Pump Voltage V+ = 5V, V6 = 2V, Pin 16 open, V13 → 5V V+ = 30V, V6 = 2V, Pin16 open, V13 → 30V l l 9 40 11 43 47 9 40 11 43 47 V V V9 Bottom Gate “ON” Voltage V+ = V16 = 18V, V6 = 0.8V l 12 14.5 17 12 14.5 17 V V1 Boost Drive Voltage V+ = V16 = 18V, V6 = 0.8V, 100mA Pulsed Load l 12 14.5 17 12 14.5 17 V V14 – V13 Top Turn-Off Threshold V+ = V16 = 5V, V6 = 0.8V 1 1.75 2.5 1 1.75 2.5 V V8 Bottom Turn-Off Threshold V+ = V16 = 5V, V6 = 2V 1 1.5 2 1 1.5 2 V Fault Output Leakage V+ = 30V, V16 = 15V, V6 = 2V 0.1 1 0.1 1 μA Fault Output Saturation V12 – V11 Current Limit Threshold V+ = 30V, V16 = 15V, V6 = 2V, I5 = 10mA V+ = 30V, V16 = 15V, V6 = 2V, I5 = 100μA V+ = 30V, V16 = 15V, V6 = 2V, Closed Loop V12 – V11 Current Limit Inhibit VDS Threshold V+ = V12 = 12V, V6 = 2V, Decrease V11 Until V15 Goes Low tR Top Gate Rise Time Pin 6 (+) Transition, Meas. V15 – V13 (Note 4) tD Top Gate Turn-Off Delay tF I5 l 0.5 1 0.5 1 90 110 130 85 110 135 mV 130 120 150 170 180 120 120 150 180 180 mV mV 1.1 1.25 1.4 1.1 1.25 1.4 V l 130 250 130 250 ns Pin 6 (–) Transition, Meas. V15 – V13 (Note 4) l 350 550 350 550 ns Top Gate Fall Time Pin 6 (–) Transition, Meas. V15 – V13 (Note 4) l 120 250 120 250 ns tR Bottom Gate Rise Time Pin 6 (–) Transition, Meas. V9 (Note 4) l 130 250 130 250 ns tD Bottom Gate Turn-Off Delay Pin 6 (+) Transition, Meas. V9 (Note 4) l 200 400 200 400 ns tF Bottom Gate Fall Time Pin 6 (+) Transition, Meas. V9 (Note 4) l 100 200 100 200 ns V5 V12 – V11 Fault Conduction Threshold 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: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formulas: LT1158IN, LT1158CN: TJ = TA + (PD × 70°C/W) LT1158ISW, LT1158CSW: TJ = TA + (PD × 110°C/W) l V Note 3: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. See typical performance characteristics and applications information. Note 4: Gate rise times are measured from 2V to 10V, delay times are measured from the input transition to when the gate voltage has decreased to 10V, and fall times are measured from 10V to 2V. 1158fb 3 LT1158 TYPICAL PERFORMANCE CHARACTERISTICS DC Supply Current 30 14 I2 + I10 + I16 V+ = 12V V13 = 0V 12 V13 = V+ SUPPLY CURRENT (mA) INPUT HIGH 10 INPUT LOW 8 6 4 ENABLE LOW 2 0 5 10 INPUT HIGH 10 8 INPUT LOW 6 4 ENABLE LOW 2 0 –50 –25 0 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 50 25 75 0 TEMPERATURE (°C) Dynamic Supply Current 100 50% DUTY CYCLE V+ = 12V V+ = 6V 1 10 INPUT FREQUENCY (kHz) 100 LT1158 G03 Input Thresholds 2.0 INPUT THRESHOLD VOLTAGE (V) 45 40 30 TOP GATE VOLTAGE (V) 25 CGATE = 10000pF CGATE = 3000pF 10 CGATE = 1000pF 35 30 NO LOAD 25 20 10μA LOAD 15 10 1.8 V(HIGH) 1.6 –40°C +25°C +85°C 1.4 –40°C +25°C +85°C 1.2 V(LOW) 1.0 5 0 1 10 INPUT FREQUENCY (kHz) 0.8 0 100 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) LT1158 G04 35 0 40 Enable Thresholds Fault Conduction Threshold FAULT CONDUCTION THRESHOLD (mV) V(HIGH) –40°C +25°C 2.5 +85°C 2.0 1.5 –40°C +25°C 1.0 V(LOW) +85°C 0.5 0 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 LT1158 G07 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 LT1158 G06 Current Limit Threshold 160 3.5 3.0 5 LT1158 G05 200 V11 = 0V 150 CURRENT LIMIT THRESHOLD (mV) SUPPLY CURRENT (mA) 10 Charge Pump Output Voltage 5 ENABLE THRESHOLD VOLTAGE (V) V+ = 12V 15 0 125 50 15 V+ = 24V LT1158 G02 40 20 20 5 LT1158 G01 35 50% DUTY CYCLE CGATE = 3000pF 25 SUPPLY CURRENT (mA) I2 + I10 + I16 12 SUPPLY CURRENT (mA) Dynamic Supply Current (V +) DC Supply Current 14 140 130 120 110 +85°C +25°C 100 –40°C 90 80 180 170 160 150 130 120 110 60 100 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 LT1158 G08 +85°C +25°C –40°C 140 70 0 CLOSED LOOP 190 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 LT1158 G09 1158fb 4 LT1158 TYPICAL PERFORMANCE CHARACTERISTICS Current Limit Inhibit VDS Threshold Bottom Gate Rise Time 1.40 1.35 1.30 –40°C 1.25 +25°C 1.20 +85°C 1.15 1.10 400 350 350 300 CGATE = 10000pF 250 200 150 CGATE = 3000pF 100 CGATE = 1000pF 50 1.05 0 1.00 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 300 200 Top Gate Rise Time 100 50 0 40 Top Gate Fall Time 350 700 TOP GATE FALL TIME (ns) CGATE = 3000pF 150 100 0 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 5 10 15 20 25 30 SUPPLY VOLTAGE (V) CGATE = 10000pF 250 200 CGATE = 3000pF 150 35 40 100 V+ = 12V CGATE = 3000pF 600 500 RISE TIME 400 FALL TIME 300 200 CGATE = 1000pF CGATE = 1000pF 50 300 TRANSITION TIMES (ns) 350 200 0 Transition Times vs RGate 800 250 CGATE = 1000pF LT1158 G12 400 CGATE = 10000pF CGATE = 3000pF 150 400 300 CGATE = 10000pF 250 LT1158 G11 LT1158 G10 TOP GATE RISE TIME (ns) Bottom Gate Fall Time 400 BOTTOM GATE FALL TIME (ns) V2 – V11 1.45 BOTTOM GATE RISE TIME (ns) CURRENT LIMIT INHIBIT THRESHOLD (V) 1.50 100 50 35 40 LT1158 G13 0 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 LT1158 G14 0 0 10 20 30 40 50 60 70 80 90 100 GATE RESISTANCE (Ω) LT1158 G15 1158fb 5 LT1158 PIN FUNCTIONS BOOST DR (Pin 1): Recharges and clamps the bootstrap capacitor to 14.5V higher than pin 13 via an external diode. V+ (Pin 2): Main supply pin; must be closely decoupled to the ground pin 7. BIAS (Pin 3): Decouple point for the internal 2.6V bias generator. Pin 3 cannot have any external DC loading. ENABLE (Pin 4): When left open, the LT1158 operates normally. Pulling pin 4 low holds both MOSFETs off regardless of the input state. FAULT (Pin 5): Open collector NPN output which turns on when V12 – V11 exceeds the fault conduction threshold. INPUT (Pin 6): Taking pin 6 high turns the top MOSFET on and bottom MOSFET off; pin 6 low reverses these states. An input latch captures each low state, ignoring an ensuing high until pin 13 has gone below 2.6V. B GATE FB (Pin 8): Must connect directly to the bottom power MOSFET gate. The top MOSFET turn-on is inhibited until pin 8 has discharged to 1.5V. A hold-on current source also feeds the bottom gate via pin 8. B GATE DR (Pin 9): The high current drive point for the bottom MOSFET. When a gate resistor is used, it is inserted between pin 9 and the gate of the MOSFET. V+ (Pin 10): Bottom side driver supply; must be connected to the same supply as pin 2. SENSE– (Pin 11): The floating reference for the current limit comparator. Connects to the low side of a current shunt or Kelvin lead of a current-sensing MOSFET. When pin 11 is within 1.2V of V+, current limit is inhibited. SENSE+ (Pin 12): Connects to the high side of the current shunt or sense lead of a current-sensing MOSFET. A built-in offset between pins 11 and 12 in conjunction with RSENSE sets the top MOSFET short-circuit current. T SOURCE (Pin 13): Top side driver return; connects to MOSFET source and low side of the bootstrap capacitor. T GATE FB (Pin 14): Must connect directly to the top power MOSFET gate. The bottom MOSFET turn-on is inhibited until V14 – V13 has discharged to 1.75V. An on-chip charge pump also feeds the top gate via pin 14. T GATE DR (Pin 15): The high current drive point for the top MOSFET. When a gate resistor is used, it is inserted between pin 15 and the gate of the MOSFET. BOOST (Pin 16): Top side driver supply; connects to the high side of the bootstrap capacitor and to a diode either from supply (V+ < 10V) or from pin 1 (V+ > 10V). 1158fb 6 LT1158 BLOCK DIAGRAM V+ V+ 16 BOOST CHG PUMP BOOST DR 1 15 T GATE DR V+ V+ 2 15V 14 T GATE FB LOGIC INPUT BIAS 3 – BIAS GEN T + 25μA 7.5V FAULT 1.75V + ENABLE 4 13 T SOURCE 2.7V – 1.2V 110mV 5 SENSE+ + 12 – 11 SENSE– S – O 2.6V + 7.5V 10 V+ 1-SHOT R INPUT 6 1.4V + – S R Q Q 15V 9 B GATE DR 1-SHOT R – B 1.5V + GND 7 8 1158 FD B GATE FB 1158fb 7 LT1158 TEST CIRCUIT 150Ω 2W 1 2 + V+ + 10μF 0.01μF 3 4 + 5 V4 3k 1/2W V6 50Ω 6 7 8 BOOST DR BOOST + T GATE DR BIAS T GATE FB V ENABLE FAULT T SOURCE LT1158 INPUT GND B GATE FB 16 + 15 V16 14 2k 1/2W 3000pF + 13 V14 – V13 12 SENSE+ SENSE– V+ B GATE DR + VN2222LL 1μF CLOSED LOOP + 100Ω 11 V12 + 10 V11 9 3000pF + V8 LT1158 TC01 OPERATION (Refer to Functional Diagram) The LT1158 self-enables via an internal 25μA pull-up on the enable pin 4. When pin 4 is pulled down, much of the input logic is disabled, reducing supply current to 2mA. With pin 4 low, the input state is ignored and both MOSFET gates are actively held low. With pin 4 enabled, one or the other of the 2 MOSFETs is turned on, depending on the state of the input pin 6: high for top side on, and low for bottom side on. The 1.4V input threshold is regulated and has 200mV of hysteresis. Whenever there is an input transition on pin 6, the LT1158 follows a logical sequence to turn off one MOSFET and turn on the other. First, turn-off is initiated, then VGS is monitored until it has decreased below the turn-off threshold, and finally the other gate is turned on. An input latch gets reset by every low state at pin 6, but can only be set if the top source pin has gone low, indicating that there will be sufficient charge in the bootstrap capacitor to safely turn on the top MOSFET. In order to allow operation over 5V to 30V nominal supply voltages, an internal bias generator is employed to furnish constant bias voltages and currents. The bias generator is decoupled at pin 3 to eliminate any effects from switching transients. No DC loading is allowed on pin 3. In order to conserve power, the gate drivers only provide turn-on current for up to 2μs, set by internal one-shot circuits. Each LT1158 driver can deliver 500mA for 2μs, or 1000nC of gate charge––more than enough to turn on multiple MOSFETs in parallel. Once turned on, each gate is held high by a DC gate sustaining current: the bottom gate by a 100μA current source, and the top gate by an on-chip charge pump running at approximately 500kHz. The top and bottom gate drivers in the LT1158 each utilize two gate connections: 1) A gate drive pin, which provides the turn-on and turn-off currents through an optional series gate resistor; and 2) A gate feedback pin which connects directly to the gate to monitor the gate-to-source voltage and supply the DC gate sustaining current. The floating supply for the top side driver is provided by a bootstrap capacitor between the boost pin 16 and top source pin 13. This capacitor is recharged each time pin 13 1158fb 8 LT1158 OPERATION (Refer to Functional Diagram) goes low in PWM operation, and is maintained by the charge pump when the top MOSFET is on DC. A regulated boost driver at pin 1 employs a source-referenced 15V clamp that prevents the bootstrap capacitor from overcharging regardless of V+ or output transients. The LT1158 provides a current-sense comparator and fault output circuit for protection of the top power MOSFET. The comparator input pins 11 and 12 are normally connected across a shunt in the source of the top power MOSFET (or to a current-sensing MOSFET). When pin 11 is more than 1.2V below V+ and V12 – V11 exceeds the 110mV offset, FAULT pin 5 begins to sink current. During a short circuit, the feedback loop regulates V12 – V11 to 150mV, thereby limiting the top MOSFET current. APPLICATIONS INFORMATION Power MOSFET Selection Since the LT1158 inherently protects the top and bottom MOSFETs from simultaneous conduction, there are no size or matching constraints. Therefore selection can be made based on the operating voltage and RDS(ON) requirements. The MOSFET BVDSS should be at least 2 • VSUPPLY, and should be increased to 3 • VSUPPLY in harsh environments with frequent fault conditions. For the LT1158 maximum operating supply of 30V, the MOSFET BVDSS should be from 60V to 100V. The MOSFET RDS(ON) is specified at TJ = 25°C and is generally chosen based on the operating efficiency required as long as the maximum MOSFET junction temperature is not exceeded. The dissipation in each MOSFET is given by: P =D (IDS ) (1+ ∂ ) RDS(ON) and the available heat sinking has a thermal resistance of 20°C/W, the MOSFET junction temperature will be 125°C, and ∂ = 0.007(125 – 25) = 0.7. This means that the required RDS(ON) of the MOSFET will be 0.089Ω/1.7 = 0.0523Ω, which can be satisfied by an IRFZ34. Note that these calculations are for the continuous operating condition; power MOSFETs can sustain far higher dissipations during transients. Additional RDS(ON)) constraints are discussed under Starting High In-Rush Current Loads. GATE DR LT1158 RG RG GATE FB 2 RG: OPTIONAL 10Ω where D is the duty cycle and ∂ is the increase in RDS(ON) at the anticipated MOSFET junction temperature. From this equation the required RDS(ON) can be derived: RDS(ON) = P D (IDS ) (1+ ∂ ) 2 For example, if the MOSFET loss is to be limited to 2W when operating at 5A and a 90% duty cycle, the required RDS(ON) would be 0.089Ω/(1 + ∂). (1 + ∂) is given for each MOSFET in the form of a normalized RDS(ON) vs temperature curve, but ∂ = 0.007/°C can be used as an approximation for low voltage MOSFETs. Thus if TA = 85°C 1158 F01 Figure 1. Paralleling MOSFETs Paralleling MOSFETs MOSFETs can be paralleled. The MOSFETs will inherently share the currents according to their RDS(ON) ratio. The LT1158 top and bottom drivers can each drive four power MOSFETs in parallel with only a small loss in switching speeds (see Typical Performance Characteristics). Individual gate resistors may be required to “decouple” each MOSFET from its neighbors to prevent high frequency oscillations—consult manufacturer’s recommendations. 1158fb 9 LT1158 APPLICATIONS INFORMATION If individual gate decoupling resistors are used, the gate feedback pins can be connected to any one of the gates. Driving multiple MOSFETs in parallel may restrict the operating frequency at high supply voltages to prevent over-dissipation in the LT1158 (see Gate Charge and Driver Dissipation below). When the total gate capacitance exceeds 10,000pF on the top side, the bootstrap capacitor should be increased proportionally above 0.1μF. Gate Charge and Driver Dissipation A useful indicator of the load presented to the driver by a power MOSFET is the total gate charge QG, which includes the additional charge required by the gate-to-drain swing. QG is usually specified for VGS = 10V and VDS = 0.8VDS(MAX). When the supply current is measured in a switching application, it will be larger than given by the DC electrical characteristics because of the additional supply current associated with sourcing the MOSFET gate charge: ⎛ dQ ⎞ ⎛ dQ ⎞ ISUPPLY = IDC + ⎜ G ⎟ +⎜ G⎟ ⎝ dt ⎠ TOP ⎝ dt ⎠ BOTTOM The actual increase in supply current is slightly higher due to LT1158 switching losses and the fact that the gates are being charged to more than 10V. Supply current vs switching frequency is given in the Typical Performance Characteristics. The LT1158 junction temperature can be estimated by using the equations given in Note 1 of the electrical characteristics. For example, the LT1158SI is limited to less than 25mA from a 24V supply: TJ = 85°C + (25mA • 24V • 110°C/W) = 151°C exceeds absolute maximum In order to prevent the maximum junction temperature from being exceeded, the LT1158 supply current must be checked with the actual MOSFETs operating at the maximum switching frequency. MOSFET Gate Drive Protection For supply voltages of over 8V, the LT1158 will protect standard N-channel MOSFETs from under or overvoltage gate drive conditions for any input duty cycle including DC. Gate-to-source Zener clamps are not required and not recommended since they can reduce operating efficiency. A discontinuity in tracking between the output pulse width and input pulse width may be noted as the top side MOSFET approaches 100% duty cycle. As the input low signal becomes narrower, it may become shorter than the time required to recharge the bootstrap capacitor to a safe voltage for the top side driver. Below this duty cycle the output pulse width will stop tracking the input until the input low signal is <100ns, at which point the output will jump to the DC condition of top MOSFET “on” and bottom MOSFET “off.” Low Voltage Operation The LT1158 can operate from 5V supplies (4.5V min) and in 6V battery-powered applications by using logic-level N-channel power MOSFETs. These MOSFETs have 2V maximum threshold voltages and guaranteed RDS(ON) limits at VGS = 4V. The switching speed of the LT1158, unlike CMOS drivers, does not degrade at low supply voltages. For operation down to 4.5V, the boost pin should be connected as shown in Figure 2 to maximize gate drive to the top side MOSFET. Supply voltages over 10V should not be used with logic-level MOSFETs because of their lower maximum gate-to-source voltage rating. 5V N.C. BOOST DR BOOST T GATE DR LT1158 T GATE FB D1 + 0.1μF LOGIC-LEVEL MOSFET T SOURCE D1: LOW-LEAKAGE SCHOTTKY BAT85 OR EQUIVALENT LT1158 F02 Figure 2. Low Voltage Operation 1158fb 10 LT1158 APPLICATIONS INFORMATION Ugly Transient Issues In PWM applications the drain current of the top MOSFET is a square wave at the input frequency and duty cycle. To prevent large voltage transients at the top drain, a low ESR electrolytic capacitor must be used and returned to the power ground. The capacitor is generally in the range of 250μF to 5000μF and must be physically sized for the RMS current flowing in the drain to prevent heating and premature failure. In addition, the LT1158 requires a separate 10μF capacitor connected closely between pins 2 and 7. The LT1158 top source and sense pins are internally protected against transients below ground and above supply. However, the gate drive pins cannot be forced below ground. In most applications, negative transients coupled from the source to the gate of the top MOSFET do not cause any problems. However, in some high current (10A and above) motor control applications, negative transients on the top gate drive may cause early tripping of the current limit. A small Schottky diode (BAT85) from pin 15 to ground avoids this problem. Switching Regulator Applications The LT1158 is ideal as a synchronous switch driver to improve the efficiency of step-down (buck) switching regulators. Most step-down regulators use a high current Schottky diode to conduct the inductor current when the switch is off. The fractions of the oscillator period that the switch is on (switch conducting) and off (diode conducting) are given by: ⎛V ⎞ SWITCH “ON” = ⎜ OUT ⎟ • TOTAL PERIOD ⎝ VIN ⎠ ⎛V −V ⎞ SWITCH “OFF” = ⎜ IN OUT ⎟ • TOTAL PERIOD VIN ⎝ ⎠ Note that for VIN > 2VOUT, the switch is off longer than it is on, making the diode losses more significant than the switch. The worst case for the diode is during a short circuit, when VOUT approaches zero and the diode conducts the short-circuit current almost continuosly. Figure 3 shows the LT1158 used to synchronously drive a pair of power MOSFETs in a step-down regulator application, where the top MOSFET is the switch and the bottom MOSFET replaces the Schottky diode. Since both conduction paths have low losses, this approach can result in very high efficiency—from 90% to 95% in most applications. And for regulators under 5A, using low RDS(ON) N-channel MOSFETs eliminates the need for heatsinks. VIN + T GATE DR T GATE FB RGS RSENSE VOUT T SOURCE LT1158 FAULT REF PWM SENSE+ + SENSE– B GATE DR INPUT B GATE FB 1158 F03 Figure 3. Adding Synchronous Switching to a Step-Down Switching Regulator 1158fb 11 LT1158 APPLICATIONS INFORMATION Current Limit in Switching Regulator Applications 100 EFFICIENCY (%) 90 FIGURE 12 CIRCUIT VIN = 12V 80 70 60 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT CURRENT (A) 3.5 4.0 LT1158 F04 Figure 4. Typical Efficiency Curve for Step-Down Regulator with Synchronous Switch One fundamental difference in the operation of a stepdown regulator with synchronous switching is that it never becomes discontinuous at light loads. The inductor current doesn’t stop ramping down when it reaches zero, but actually reverses polarity resulting in a constant ripple current independent of load. This does not cause any efficiency loss as might be expected, since the negative inductor current is returned to VIN when the switch turns back on. The LT1158 performs the synchronous MOSFET drive and current sense functions in a step-down switching regulator. A reference and PWM are required to complete the regulator. Any voltage-mode PWM controller may be used, but the LT3525 is particularly well suited to high power, high efficiency applications such as the 10A circuit shown in Figure 13. In higher current regulators a small Schottky diode across the bottom MOSFET helps to reduce reverse-recovery switching losses. The LT1158 input pin can also be driven directly with a ramp or sawtooth. In this case, the DC level of the input waveform relative to the 1.4V threshold sets the LT1158 duty cycle. In the 5V to 3.3V converter circuit shown in Figure 11, an LT1431 controls the DC level of a triangle wave generated by a CMOS 555. The Figure 10 and 12 circuits use an RC network to ramp the LT1158 input back up to its 1.4V threshold following each switch cycle, setting a constant off time. Figure 4 shows the efficiency vs output current for the Figure 12 regulator with VIN = 12V. Current is sensed by the LT1158 by measuring the voltage across a current shunt (low valued resistor). Normally, this shunt is placed in the source lead of the top MOSFET (see Short-Circuit Protection in Bridge Applications). However, in step-down switching regulator applications, the remote current sensing capability of the LT1158 allows the actual inductor current to be sensed. This is done by placing the shunt in the output lead of the inductor as shown in Figure 3. Routing of the SENSE+ and SENSE– PC traces is critical to prevent stray pickup. These traces must be routed together at minimum spacing and use a Kelvin connection at the shunt. When the voltage across RSENSE exceeds 110mV, the LT1158 FAULT pin begins to conduct. By feeding the FAULT signal back to a control input of the PWM, the LT1158 will assume control of the duty cycle forming a true current mode loop to limit the output current: IOUT = 110mV in current limit RSENSE In LT3525 based circuits, connecting the FAULT pin to the LT3525 soft-start pin accomplishes this function. In circuits where the LT1158 input is being driven with a ramp or sawtooth, the FAULT pin is used to pull down the DC level of the input. The constant off-time circuits shown in Figures 10 and 12 are unique in that they also use the current sense during normal operation. The LT1431 output reduces the normal LT1158 110mV fault conduction threshold such that the FAULT pin conducts at the required load current, thus discharging the input ramp capacitor. In current limit the LT1431 output turns off, allowing the fault conduction threshold to reach its normal value. The resistor RGS shown in Figure 3 is necessary to prevent output voltage overshoot due to charge coupled into the gate of the top MOSFET by a large start-up dv/dt on VIN. If DC operation of the top MOSFET is required, RGS must be 330k or greater to prevent loading the charge pump. 1158fb 12 LT1158 APPLICATIONS INFORMATION Low Current Shutdown The LT1158 may be shutdown to a current level of 2mA by pulling the enable pin 4 low. In this state both the top and bottom MOSFETs are actively held off against any transients which might occur on the output during shutdown. This is important in applications such as 3-phase DC motor control when one of the phases is disabled while the other two are switching. If zero standby current is required and the load returns to ground, then a switch can be inserted into the supply path of the LT1158 as shown in Figure 5. Resistor RGS ensures that the top MOSFET gate discharges, while the voltage across the bottom MOSFET goes to zero. The voltage drop across the P-channel supply switch must be less than 300mV, and RGS must be 330k or greater for DC operation. This technique is not recommended for applications which require the LT1158 VDS sensing function. (Figure 6). For the current-sensing MOSFET shown in Figure 7, the sense resistor is inserted between the sense and Kelvin leads. The SENSE+ and SENSE– PC traces must be routed together at minimum spacing to prevent stray pickup, and a Kelvin connection must be used at the current shunt for the 3-lead MOSFET. Using a twisted pair is the safest approach and is recommended for sense runs of several inches. When the voltage across RSENSE exceeds 110mV, the LT1158 FAULT pin begins to conduct, signaling a fault condition. The current in a short circuit ramps very rapidly, limited only by the series inductance and ultimately the MOSFET and shunt resistance. Due to the response time V+ + T GATE DR T GATE FB + V T SOURCE 5V + 100k T GATE DR VP0300 V+ 2N2222 SENSE+ RSENSE 10k SENSE– FAULT T GATE FB RGS V+ 100k LT1158 T SOURCE + CMOS ON/OFF TO OTHER CONTROL CIRCUITS 1158 F06 LT1158 LOAD GND Figure 6. Short-Circuit Protection with Standard MOSFET B GATE DR V+ B GATE FB + 1158 F05 T GATE DR Figure 5. Adding Zero Current Shutdown T GATE FB SENSE Short-Circuit Protection in Bridge Applications The LT1158 protects the top power MOSFET from output shorts to ground, or in a full bridge application, shorts across the load. Both standard 3-lead MOSFETs and current-sensing 5-lead MOSFETs can be protected. The bottom MOSFET is not protected from shorts to supply. KELVIN T SOURCE 5V LT1158 SENSE+ RSENSE OUTPUT 10k FAULT SENSE– 1158 F07 Current is sensed by measuring the voltage across a current shunt in the source lead of a standard 3-lead MOSFET Figure 7. Short-Circuit Protection with Current-Sensing MOSFET 1158fb 13 LT1158 APPLICATIONS INFORMATION 5A/DIV of the LT1158 current limit loop, an initial current spike of from 2 to 5 times the final value will be present for a few μs, followed by an interval in which IDS = 0. The current spike is normally well within the safe operating area (SOA) of the MOSFET, but can be further reduced with a small (0.5μH) inductor in series with the output. the value of RSENSE for the 5-lead MOSFET increases by the current sensing ratio (typically 1000 – 3000), thus eliminating the need for a low valued shunt. ΔV is in the range of 1V to 3V in most applications. Assuming a dead short, the MOSFET dissipation will rise to VSUPPLY • ISC. For example, with a 24V supply and ISC = 10A, the dissipation would be 240W. To determine how long the MOSFET can remain at this dissipation level before it must be shut down, refer to the SOA curves given in the MOSFET data sheet. For example, an IRFZ34 would be safe if shut down within 10ms. A Tektronix A6303 current probe is highly recommended for viewing output fault currents. ISC If Short-Circuit Protection is Not Required 5μs/DIV LT1158 F08 Figure 8. Top MOSFET Short-Circuit Turn-On current If neither the enable nor input pins are pulled low in response to the fault indication, the top MOSFET current will recover to a steady-state value ISC regulated by the LT1158 as shown in Figure 8: ISC = 150mV RSENSE RSENSE = 150mV ISC r (150mV ) ⎛ 150mV ⎞ −2 ISC = 1− RSENSE ⎜⎝ ΔV ⎟⎠ r (150mV ) ⎛ 150mV ⎞ −2 RSENSE = ⎜⎝ 1− ΔV ⎟⎠ ISC r = current sense ratio, ΔV = VGS = VGS − VT The time for the current to recover to ISC following the initial current spike is approximately QGS/0.5mA, where QGS is the MOSFET gate-to-source charge. ISC need not be set higher than the required start-up current for motors (see Starting High In-Rush Current Loads). Note that In applications which do not require the current sense capability of the LT1158, the sense pins 11 and 12 should both be connected to pin 13, and the FAULT pin 5 left open. The enable pin 4 may still be used to shut down the device. Note, however, that when unprotected the top MOSFET can be easily (and often dramatically) destroyed by even a momentary short. Self-Protection with Automatic Restart When using the current sense circuits of Figures 6 and 7, local shutdown can be achieved by connecting the FAULT pin through resistor RF to the enable pin as shown in Figure 9. An optional thermostat mounted to the load or MOSFET heatsink can also be used to pull enable low. An internal 25μA current source normally keeps the enable capacitor CEN charged to the 7.5V clamp voltage (or to V+, for V+ < 7.5V). When a fault occurs, CEN is discharged to below the enable low threshold (1.15V typ) which shuts down both MOSFETs. When the FAULT pin or thermostat releases, CEN recharges to the upper enable threshold where restart is attempted. In a sustained short circuit, FAULT will again pull low and the cycle will repeat until the short is removed. The time to shut down for a DC input or thermal fault is given by: tSHUTDOWN = (100 + 0.8RF) CEN DC input 1158fb 14 LT1158 APPLICATIONS INFORMATION Note that for the first event only, tSHUTDOWN is approximately twice the above value since CEN is being discharged all the way from its quiescent voltage. Allowable values for RF are from zero to 10k. 7.5V 1.15V 25μA ENABLE CEN 1μF SENSE– pin is within 1.2V of supply. Under these conditions the current is limited only by the RDS(ON) in series with RSENSE. For a 5-lead MOSFET the current is limited by RDS(ON) alone, since RSENSE is not in the output path (see Figure 7). Again adjusting RDS(ON) for temperature, the worst-case start currents are: (1+ ∂) RDS(ON) + RSENSE ISTART = 1.2V (1+ ∂) RDS (ON) + 7.5V RF 1k LT1158 1.2V ISTART = 3-Lead MOSFET 5-Lead MOSFET FAULT Properly sizing the MOSFET for ISTART allows inductive loads with long time constants, such as motors with high mechanical inertia, to be started. OPTIONAL THERMOSTAT CLOSE ON RISE AIRPAX #67FXXX 1158 F09 Figure 9. Self-Protection with Auto Restart tSHUTDOWN becomes more difficult to analyze when the output is shorted with a PWM input. This is because the FAULT pin only conducts when fault currents are actually present in the MOSFET. FAULT does not conduct while the input is low in Figures 6 and 7 or during the interval IDS = 0 in Figure 8. Thus tSHUTDOWN will safely increase when the duty cycle of the current in the top MOSFET is low, maintaining the average MOSFET current at a relatively constant level. The length of time following shutdown before restart is attempted is given by: ( ) ⎛ 1.5V ⎞ t RESTART = ⎜ C = 6 × 10 4 CEN ⎝ 25μA ⎟⎠ EN In Figure 9, the top MOSFET would shut down after being in DC current limit for 0.9ms and try to restart at 60ms intervals, thus producing a duty cyle of 1.5% in short circuit. The resulting average top MOSFET dissipation during a short is easily measured by taking the product of the supply voltage and the average supply current. Starting High In-Rush Current Loads The LT1158 has a VDS sensing function which allows more than ISC to flow in the top MOSFET providing that the Returning to the example used in Power MOSFET Selection, an IRFZ34 (RDS(ON) = 0.05Ω max) was selected for operation at 5A. If the short-circuit current is also set at 5A, what start current can be supported? From the equation for RSENSE, a 0.03Ω shunt would be required, allowing the worst-case start current to be calculated: ISTART = 1 .2V = 10 A (1.7) 0.05 Ω +0.03Ω This calculation gives the minimum current which could be delivered with the IRFZ34 at TJ = 125°C without activating the FAULT pin on the LT1158. If more start current is required, using an IRFZ44 (RDS(ON) = 0.028Ω max) would increase ISTART to over 15A at TJ = 110°C, even though the short-circuit current remains at 5A. In order for the VDS sensing function to work properly, the supply pins for the LT1158 must be connected at the drain of the top MOSFET, which must be properly decoupled (see Ugly Transient Issues). Driving Lamps Incandescent lamps represent a challenging load because they have much in common with a short circuit when cold. The top gate driver in the LT1158 can be configured to turn on large lamps while still protecting the power MOSFET 1158fb 15 LT1158 APPLICATIONS INFORMATION from a true short. This is done by using the current limit to control cold filament current in conjunction with the selfprotection circuit of Figure 9. The reduced cold filament current also extends the life of the filament. down the top MOSFET. The LT1158 will then go into the automatic restart mode described in Self-Protection with Automatic Restart above. The time constant for an incandescent filament is tens of milliseconds, which means that tSHUTDOWN will have to be longer than in most other applications. This places increased SOA demands on the MOSFET during a short circuit, requiring that a larger than normal device be used. A protected high current lamp driver application is shown in Figure 18. A good guideline is to choose RSENSE to set ISC at approximately twice the steady state “on” current of the lamp(s). tSHUTDOWN is then made long enough to guarantee that the lamp filaments heat and drop out of current limit before the enable capacitor discharges to the enable low threshold. For a short-circuit, the enable capacitor will continue to discharge below the threshold, shutting TYPICAL APPLICATIONS 5V TO 10V INPUT (USE LOGIC-LEVEL Q1, Q2) 8V TO 20V INPUT (USE STANDARD Q1, Q2 AND CONNECT BOOST DIODE TO PIN 1) 1N4148 100k s 1 VP0300 2 0.01μF 3 INSERT FOR ZERO POWER SHUTDOWN 4 + 100k 10μF 2N2222 5 CMOS ON/OFF 6 7 8 Q1, Q2: IRLZ44 (LOGIC-LEVEL) IRFZ44 (STANDARD) BOOST + T GATE DR BIAS T GATE FB ENABLE T SOURCE V FAULT INPUT GND B GATE FB LT1158 SENSE 16 500μF LOW ESR 15 14 0.1μF 680k L1 22μH 13 + + 12 100Ω 11 100Ω SENSE– + Q1 SHORT-CIRCUIT RS CURRENT = 8A 0.015Ω +3.3V/6A OUTPUT – + Q2 B GATE DR 9 510Ω 1.62k 1% 1N4148 CONSTANT OFF TIME CURRENT MODE CONTROL LOOP 8 1 1000pF RS: VISHAY/DALE TYPE LVR-3 VISHAY/ULTRONIX RCS01, SM1 ISOTEK CORP. ISA-PLAN SMR 0.05μF 1k 7 2 3 4 LT1431 6 4.99k 1% 200pF 5 V 1 1 – OUT WHERE tOFF ≈ 10μs tOFF VIN ( 1000μF LOW ESR 10 V+ 24k L1: HURRICANE LAB HL-KK122T/BB FREQUENCY = BOOST DR ) LT1158 F10 Figure 10. High Efficiency 3.3V Step-Down Switching Regulator (Requires No Heatsinks) 1158fb 16 LT1158 TYPICAL APPLICATIONS DRIVER SUPPLY 10V TO 15V (CAN BE POWERED FROM VIN WITH LOGIC-LEVEL Q1, Q2) 0.33μF 16k 0.01μF + 10μF 1 8 2 7 LT1431 3 3.3k 1 2 200pF 6 3 4.99k 1% SHUTDOWN 4 5 1000pF 1 24k 6 8 470pF 7 2 CMOS 555 3 BOOST DR BOOST V+ T GATE DR 16 6 RX 1% 7 8 BIAS T GATE FB ENABLE T SOURCE LT1158 FAULT INPUT SENSE– 11 V+ 10 220μF 10V OS-CON s 4 Q1 0.22μF 500k L1 8μH 13 12 B GATE DR B GATE FB 14 SENSE+ GND + BAS16 15 0.01μF 5 4 VIN 4.5V TO 6V SHORT-CIRCUIT CURRENT = 22A RS + – + 0.01Ω EA 9 VOUT 15A 330μF 6.3V AVX s 4 Q2 5 4 LT1158 F11 VOUT 2.90V 3.05V 3.30V 3.45V 3.60V RX (1%) 806Ω 1.62k 1.91k 1.10k L1: COILTRONICS CTX02-12171-1 RS: KRL/BANTRY SL-1R010J s 2 Q1, Q2: MTB75N05HD (USE WITH 10V TO 15V DRIVER SUPPLY) MTB75N03HDL (USE WITH VIN DRIVER SUPLY) CMOS 555: LMC555 OR TLC555 2.21k Figure 11. 5V to 3.XXV,15A Converter (Uses PC Board Area for Heatsink) 8V TO 20V INPUT 1N4148 100k s 1 BOOST DR BOOST 16 IRFZ34 VP0300 2 0.01μF INSERT FOR ZERO POWER SHUTDOWN 3 4 + 100k 10μF 2N2222 CMOS ON/OFF 5 6 + T GATE DR BIAS T GATE FB V ENABLE FAULT INPUT T SOURCE LT1158 + 500μF LOW ESR 15 14 SHORT-CIRCUIT CURRENT = 6A 510k 0.1μF L1 50μH 13 SENSE+ 12 100Ω SENSE– 11 100Ω V+ 10 RS 20mΩ + – + +5V/4A OUTPUT 1000μF LOW ESR IRFZ44 7 8 GND B GATE FB B GATE DR 9 24k 510Ω L1: COILTRONICS CTX50-5-52 1N4148 0.05μF RS: VISHAY/DALE TYPE LVR-3 VISHAY/ULTRONIX RCS01, SM1 ISOTEK CORP. ISA-PLAN SMR V FREQUENCY = 1 – OUT tOFF VIN 1 ( ) WHERE t 1k SEE FIGURE 4 FOR EFFICIENCY CURVE 7 2 3 CONSTANT OFF TIME CURRENT MODE CONTROL LOOP 8 1 1000pF LT1431 4 OFF ≈ 10μs 6 5 LT1158 F12 Figure 12. High Efficiency 5V Step-Down Switching Regulator (Requires No Heatsinks) 1158fb 17 LT1158 TYPICAL APPLICATIONS INPUT 30V MAX SHUTDOWN 4.7k 0.01μF 1N4148 4.7k 1μF 16 0.1μF *3.4k 1 + 1 15 2 2 + EXT SYNC 30k f = 25kHz 3 14 10μF 4 13 2.2nF 0.01μF 3 4 1N4148 BOOST DR V+ T GATE DR BIAS T GATE FB ENABLE T SOURCE LT3525 12 5 0.01μF 6 11 7 10 8 9 5 1N4148 6 BOOST LT1158 FAULT SENSE+ + 16 + 500μF EA LOW ESR IRFZ44 15 SHORT-CIRCUIT CURRENT = 15A 0.1μF 14 330k 13 L1 70μH RS 0.007Ω + – 12 + 11 SENSE– INPUT 5V OR 12V* 1000μF LOW ESR 27k + 510Ω 7 1μF * 330pF 10k 8 V+ GND B GATE FB B GATE DR (2) IRFZ44 10 9 MBR340 LT1158 F13 * ADD THESE COMPONENTS TO IMPLEMENT RS: DALE TYPE LVR-3 L1: MAGNETICS CORE #55585-A2 ULTRONIX RCS01 30 TURNS 14GA MAGNET WIRE LOW-DROPOUT 12V REGULATOR Figure 13. 90% Efficiency 24V to 5V 10A Switching Regulator 95% Efficiency 24V to 12V 10A Low Dropout Switching Regulator MOTOR SPEED 0 TO 100% 10V TO 30V 5.1k 1N4148 10k + 1 1N5231A 1μF BOOST DR BOOST 16 7.5k 2 + 0.01μF 3 10μF 13k 1 8 2 7 3 4 CMOS 555 0.33μF 1k 6 5 4 5 6 2.2nF 510Ω 7 8 THE CMOS 555 IS USED AS A 25kHz TRIANGLE-WAVE OSCILLATOR DRIVING THE LT1158 INPUT PIN. THE D.C. LEVEL OF THE TRIANGLE WAVE IS SET BY THE POTENTIOMETER ON THE CMOS 555 SUPPLY PIN, AND ALLOW ADJUSTMENT OF THE LT1158 DUTY CYCLE FROM 0 TO 100%. V+ T GATE DR BIAS T GATE FB ENABLE T SOURCE FAULT INPUT GND B GATE FB LT1158 15 + 0.1μF 14 1000μF LOW ESR Q1 13 SENSE+ 12 SENSE– 11 V+ 10 B GATE DR 24Ω 9 + START CURRENT = 15A MINIMUM 0.02Ω – 24Ω Q2 CMOS 555: LMC555 OR TLC555 Q1, Q2: MTP35N06E - LT1158 F14 Figure 14. Potentiometer-Adjusted Open Loop Motor Speed Control with Short-Circuit Protection 1158fb 18 LT1158 TYPICAL APPLICATIONS 7.2V NOMINAL + BAT85 1 2 + 0.01μF 10μF STOP (FREE RUN) 3 1N4148 4 + 1k 1μF 5 6 PWM 7 8 BOOST DR BOOST V+ T GATE DR BIAS T GATE FB ENABLE T SOURCE FAULT INPUT LT1158 B GATE FB 15 15Ω 0.1μF 14 Q1 13 + 12 SENSE+ B GATE DR – 10 9 START CURRENT = 25A MINIMUM RS 0.015Ω 11 SENSE– V+ GND 100μF 16 15Ω Q2 - LT1158 F15 Q1, Q2: IRLZ44 (LOGIC-LEVEL) RS: DALE TYPE LVR-3 ULTRONIX RCS01 Figure 15. High Efficiency 6-Cell NiCd Protected Motor Drive V+ V+ LT1158 ENABLE FAULT 5V INPUT V+ LT1158 LT1158 ENABLE FA FAULT ENABLE FB INPUT FAULT FC INPUT SHUTDOWN COMMUTATING LOGIC PWM CONTROLS LT1158 INPUTS POSITION FEEDBACK CONTROLS LT1158 ENABLE INPUTS 1158 F16 Figure 16. 3-Phase Brushless DC Motor Control 1158fb 19 LT1158 TYPICAL APPLICATIONS 1N4148 1 BOOST DR 2 V 0.01μF 3 ENABLE A 4 + 10μF FAULT A 5 BOOST + T GATE DR BIAS T GATE FB ENABLE T SOURCE FAULT 6 INPUT A LT1158 INPUT 7 14 15Ω + Q1 D1 SIDE A: SHOWS STANDARD MOSFET CONNECTION 470μF LOW ESR 13 12 SENSE– 11 V+ 10 B GATE DR B GATE FB 0.1μF 15 SENSE+ GND 8 10V TO 30V 16 + RS 0.015Ω – 9 Q2 2.4k 15Ω 1N4148 1 2 BOOST DR BOOST V+ T GATE DR BIAS T GATE FB 15 0.01μF 3 4 ENABLE B + 10μF 5 FAULT B 6 INPUT B 7 8 ENABLE FAULT T SOURCE LT1158 INPUT GND B GATE FB 14 470μF LOW ESR Q3 15Ω SIDE B: SHOWS CURRENT-SENSING MOSFET CONNECTION 0.1μF D2 + – 13 SENSE+ 12 SENSE– 11 V+ 10 B GATE DR + 16 9 2.4k 47Ω Q4 Q1, Q3: IRF540 (STANDARD) IRC540 (SENSE FET) Q2, Q4: IRFZ44 D1, D2: BAT83 RS: DALE TYPE LVR-3 ULTRONIX RCS01 15Ω LT1158 F17a Control Logic for Locked Anti-Phase Drive Motor stops if either side is shorted to ground Control Logic for Sign/Magnitude Drive 5V ENABLE A 74HC132 FAULT A 74HC02 5.1k ENABLE A 0.01μF INPUT A FAULT A INPUT A PWM PWM DIRECTION STOP (FREE RUN) 1N4148 ENABLE B + 1μF FAULT B 150k 0.1μF INPUT B 1158F17b ENABLE B 1N4148 FAULT B INPUT B 1158F17c Figure 17. 10A Full Bridge Motor Control 1158fb 20 LT1158 PACKAGE DESCRIPTION N Package 16-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .770* (19.558) MAX 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 .255 ± .015* (6.477 ± 0.381) .130 ± .005 (3.302 ± 0.127) .300 – .325 (7.620 – 8.255) .020 (0.508) MIN .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 +0.889 8.255 –0.381 .045 – .065 (1.143 – 1.651) .065 (1.651) TYP .120 (3.048) MIN ) .018 ± .003 (0.457 ± 0.076) .100 (2.54) BSC NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) N16 1002 SW Package 16-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) .050 BSC .045 ±.005 .030 ±.005 TYP .398 – .413 (10.109 – 10.490) NOTE 4 16 N 15 14 13 12 11 10 9 N .325 ±.005 .420 MIN .394 – .419 (10.007 – 10.643) NOTE 3 1 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .291 – .299 (7.391 – 7.595) NOTE 4 .010 – .029 × 45° (0.254 – 0.737) .005 (0.127) RAD MIN 2 3 4 5 6 .093 – .104 (2.362 – 2.642) 7 8 .037 – .045 (0.940 – 1.143) 0° – 8° TYP .009 – .013 (0.229 – 0.330) NOTE 3 .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN .050 (1.270) BSC .004 – .012 (0.102 – 0.305) .014 – .019 (0.356 – 0.482) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS 4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) S16 (WIDE) 0502 1158fb 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. 21 LT1158 TYPICAL APPLICATION 12V 1N4148 1 2 + 10μF 0.01μF 3 4 + 10μF 6.2k 5 6 ON/OFF 7 8 BOOST DR BOOST V+ T GATE DR BIAS T GATE FB ENABLE T SOURCE FAULT INPUT GND B GATE FB LT1158 1000μF IRCZ44 15 14 0.1μF + – 13 SENSE+ 12 SENSE– 11 V+ 10 B GATE DR + 16 12V 55W MBR330 51Ω 9 ISC: 10A tSHUTDOWN = 50ms tRESTART = 600ms LT1158 F18 Figure 18. High Current Lamp Driver with Short-Circuit Protection 1158fb 22 Linear Technology Corporation LT 0309 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1994