LTC1157 3.3V Dual Micropower High-Side/Low-Side MOSFET Driver U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Allows Lowest Drop 3.3V Supply Switching Operates on 3.3V or 5V Nominal Supplies 3 Microamps Standby Current 80 Microamps ON Current Drives Low Cost N-Channel Power MOSFETs No External Charge Pump Components Controlled Switching ON and OFF Times Compatible with 3.3V and 5V Logic Families Available in 8-Pin SOIC The LTC1157 dual 3.3V micropower MOSFET gate driver makes it possible to switch either supply or ground reference loads through a low RDS(ON) N-channel switch (N-channel switches are required at 3.3V because Pchannel MOSFETs do not have guaranteed RDS(ON) with VGS ≤ 3.3V). The LTC1157 internal charge pump boosts the gate drive voltage 5.4V above the positive rail (8.7V above ground), fully enhancing a logic level N-channel switch for 3.3V high-side applications and a standard Nchannel switch for 3.3V low-side applications. The gate drive voltage at 5V is typically 8.8V above supply (13.8V above ground), so standard N-channel MOSFET switches can be used for both high-side and low-side applications. UO APPLICATI ■ ■ ■ ■ ■ ■ Notebook Computer Power Management Palmtop Computer Power Management P-Channel Switch Replacement Battery Charging and Management Mixed 5V and 3.3V Supply Switching Stepper Motor and DC Motor Control Cellular Telephones and Beepers Micropower operation, with 3µA standby current and 80µA operating current, makes the LTC1157 well suited for battery-powered applications. The LTC1157 is available in both 8-pin DIP and SOIC. UO ■ S TYPICAL APPLICATI Ultra Low Voltage Drop 3.3V Dual High-Side Switch Gate Voltage Above Supply 3.3V + 10µF VS 3.3V LOGIC IN1 G1 LTC1157 IN2 G2 (8.7V) (8.7V) IRLR024 IRLR024 3.3V LOAD GND LTC1157 • TA01 3.3V LOAD GATE VOLTAGE – SUPPLY VOLTAGE (V) 12 10 8 6 4 2 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) 6.0 LTC1157 • TA02 1 LTC1157 W W W AXI U U ABSOLUTE RATI GS Supply Voltage ........................................... – 0.3V to 7V Any Input Voltage ............. (VS + 0.3V) to (GND – 0.3V) Any Output Voltage ............. (VS + 12V) to (GND – 0.3V) Current (Any Pin)................................................. 50mA Operating Temperature Range LTC1157C............................................... 0°C to 70°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO TOP VIEW NC 1 GATE 1 2 8 NC 7 GATE 2 GND 3 6 VS IN1 4 5 IN2 ORDER PART NUMBER LTC1157CN8 NC 1 8 NC GATE 1 2 7 GATE 2 GND 3 6 VS IN1 4 5 IN2 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 100°C, θJA = 130°C/ W TJMAX = 100°C, θJA = 150°C/ W PARAMETER CONDITIONS IQ Quiescent Current OFF Quiescent Current ON VS = 3.3V, VIN1 = VIN2 = 0V (Note 1) VS = 3.3V, VIN = 3.3V (Note 2) VS = 5V, VIN = 5V (Note 2) VINH VINL IIN CIN VGATE – VS Input High Voltage Input Low Voltage Input Current Input Capacitance Gate Voltage Above Supply tON Turn-ON Time Turn-OFF Time MIN ● LTC1157C TYP MAX UNITS 3 80 180 10 160 400 4.0 4.5 7.5 5 4.7 5.4 8.8 6.5 7.0 12.0 µA µA µA V V µA pF V V V 30 75 130 240 300 750 µs µs 30 75 85 230 300 750 µs µs 10 36 60 µs 10 31 60 µs 70% × VS 15% × VS ±1 ● 0V ≤ VIN ≤ VS ● VS = 3V VS = 3.3V VS = 5V VS = 3.3V, CGATE = 1000pF Time for VGATE > VS + 1V Time for VGATE > VS + 2V VS = 5V, CGATE = 1000pF Time for VGATE > VS + 1V Time for VGATE > VS + 2V VS = 3.3V, CGATE = 1000pF Time for VGATE < 0.5V VS = 5V, CGATE = 1000pF Time for VGATE < 0.5V ● ● ● The ● denotes specifications which apply over the full operating temperature range. Note 1: Quiescent current OFF is for both channels in OFF condition. Note 2: Quiescent current ON is per driver and is measured independently. 2 1157 VS = 2.7V to 5.5V, TA = 25°C, unless otherwise noted. SYMBOL tOFF LTC1157CS8 S8 PART MARKING N8 PACKAGE 8-LEAD PLASTIC DIP ELECTRICAL CHARACTERISTICS ORDER PART NUMBER TOP VIEW LTC1157 U W TYPICAL PERFOR A CE CHARACTERISTICS Standby Supply Current Supply Current per Driver ON 12 ONE INPUT = ON OTHER INPUT = OFF TA = 25°C 500 SUPPLY CURRENT (µA) 8 6 4 2 400 300 200 100 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 0 6.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) LTC1157 • TPC01 Input Threshold Voltage 2 2.0 1.0 0.5 600 400 VGS = 2V VGS = 5V 300 2.0 2.5 40 30 20 10 VGS = 1V 0 6.0 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) LTC1157 • TPC04 5.5 0 6.0 2.0 10 250 SUPPLY CURRENT (µA) 300 6 VS = 5V VS = 3.3V 2 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 5.5 6.0 LTC1157 • TPC06 Supply Current per Driver ON Standby Supply Current 8 2.5 LTC1157 • TPC05 12 6.0 CGATE = 1000pF TIME FOR VGATE < 0.5V 50 200 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) 5.5 Turn-OFF Time 800 1.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 60 TURN-OFF TIME (µs) 2.5 2.0 2.5 LTC1157 • TPC03 CGATE = 1000pF TURN-ON TIME (µs) INPUT THRESHOLD VOLTAGE (V) 4 Turn-ON Time TA = 25°C 4 6 0 1000 2.0 2.5 8 LTC1157 • TPC02 3.0 0 10 6.0 Gate Drive Current 1000 TA = 25°C GATE DRIVE CURRENT (µA) SUPPLY CURRENT (µA) 12 GATE VOLTAGE – SUPPLY VOLTAGE (V) VIN1 = VIN2 = 0V TA = 25°C 10 SUPPLY CURRENT (µA) Gate Voltage Above Supply 600 200 VS = 5V 150 100 VS = 3.3V 100 VS = 5V 10 VS = 3.3V 1 50 0 0 10 40 30 50 20 TEMPERATURE (˚C) 60 70 LTC1157 • TPC07 0.1 0 0 10 40 30 50 20 TEMPERATURE (˚C) 60 70 LTC1157 • TPC08 0 2 4 6 8 GATE VOLTAGE ABOVE SUPPLY (V) 10 LTC1157 • TPC09 3 LTC1157 U U U PI FU CTIO S Input Pins: The LTC1157 input pins are active high and activate the charge pump circuitry when switched ON. The LTC1157 logic inputs are high impedance CMOS gates with ESD protection diodes to ground and supply and therefore should not be forced beyond the power supply rails. Gate Drive Pins: The gate drive pin is either driven to ground when the switch is turned OFF or driven above the supply rail when the switch is turned ON. This pin is a OPERATIO relatively high impedance when driven above the rail (the equivalent of a few hundred kΩ). Care should be taken to minimize any loading of this pin by parasitic resistance to ground or supply. Supply Pin: The supply pin of the LTC1157 should never be forced below ground as this may result in permanent damage to the device. A 300Ω resistor should be inserted in series with the ground pin if negative supply voltage transients are anticipated. U The LTC1157 is a dual micropower MOSFET driver designed specifically for operation at 3.3V and 5V and includes the following functional blocks: 3.3V Logic Compatible Inputs The LTC1157 inputs have been designed to accommodate a wide range of 3.3V and 5V logic families. Approximately 50mV of hysteresis is provided to ensure clean switching. An ultra low standby current voltage regulator provides continuous bias for the logic-to-CMOS converter. The logic-to-CMOS converter output enables the rest of the circuitry. In this way the power consumption is kept to an absolute minimum in the standby mode. W BLOCK DIAGRA Gate Charge Pump Gate drive for the power MOSFET is produced by an internal charge pump circuit which generates a gate voltage substantially higher than the power supply voltage. The charge pump capacitors are included on-chip and therefore no external components are required to generate the gate drive. Controlled Gate Rise and Fall Times When the input is switched ON and OFF, the gate is charged by the internal charge pump and discharged in a controlled manner. The charge and discharge rates have been set to minimize RFI and EMI emissions. (One Channel) VS INPUT LOW STANDBY CURRENT REGULATOR HIGH FREQUENCY OSCILLATOR CHARGE PUMP LOGIC-TO-CMOS CONVERTER VOLTAGE REGULATOR GATE DISCHARGE LOGIC LTC1157 • BD GND 4 GATE LTC1157 U U W U APPLICATIO S I FOR ATIO MOSFET Selection The LTC1157 is designed to operate with both standard and logic level N-channel MOSFET switches. The choice of switch is determined primarily by the operating supply voltage. Obviously, this is too much current for the regulator (or output capacitor) to supply and the output will glitch by as much as a few volts. The start-up current can be substantially reduced by limiting the slew rate at the gate of an N-channel switch as shown in Figure 1. The gate drive output of the LTC1157 Logic Level MOSFET Switches at 3.3V Logic level switches should be used with the LTC1157 when powered from 2.7V to 4V. Although there is some variation among manufacturers, logic level MOSFET switches are typically rated with VGS = 4V with a maximum continuous VGS rating of ±10V. RDS(ON) and maximum VDS ratings are similar to standard MOSFETs and there is generally little price differential. Logic level MOSFETs are frequently designated by an “L” and are usually available in surface mount packaging. Some logic level MOSFETs are rated up to ±15V and can be used in applications which require operation over the entire 2.7V to 5.5V range. Standard MOSFET Switches at 5V Standard N-channel MOSFET switches should be used with the LTC1157 when powered from 4V to 5.5V supply as the built-in charge pump produces ample gate drive to fully enhance these switches when powered from a 5V nominal supply. Standard N-channel MOSFET switches are rated with VGS = 10V and are generally restricted to a maximum of ±20V. Powering Large Capacitive Loads Electrical subsystems in portable battery-powered equipment are typically bypassed with large filter capacitors to reduce supply transients and supply induced glitching. If not properly powered however, these capacitors may themselves become the source of supply glitching. For example, if a 100µF capacitor is powered through a switch with a slew rate of 0.1V/µs, the current during startup is: ISTART = C(dV/dt) = (100 × 10 – 6) (1 × 10 5) = 10A VIN 3.3V LT1129-3.3 + 3.3µF R1 100k VS ON/0FF IN1 R2 1k MTD3055EL G1 1/2 LTC1157 GND C1 0.1µF + CLOAD 100µF 3.3V LOAD LTC1157 • TA02 Figure 1. Powering a Large Capacitive Load is passed through a simple RC network, R1 and C1, which substantially slows the slew rate of the MOSFET gate to approximately 1.5 × 10 – 4 V/µs. Since the MOSFET is operating as a source follower, the slew rate at the source is essentially the same as that at the gate, reducing the start-up current to approximately 15mA which is easily managed by the system regulator. R2 is required to eliminate the possibility of parasitic MOSFET oscillations during switch transitions. Also, it is good practice to isolate the gates of paralleled MOSFETs with 1k resistors to decrease the possibility of interaction between switches. Reverse Battery Protection The LTC1157 can be protected against reverse battery conditions by connecting a 300Ω resistor in series with the ground pin. The resistor limits the supply current to less than 12mA with – 3.6V applied. Since the LTC1157 draws very little current while in normal operation, the drop across the ground resistor is minimal. The 3.3V µP (or control logic) can be protected by adding 10k resistors in series with the input pins. 5 LTC1157 U TYPICAL APPLICATIO S Ultra Low Drop 3 to 4 Cell Dual High-Side Switch + 3 TO 4 CELL BATTERY PACK 0.47µF Si9956DY 7,8 5,6 VS IN1 CONTROL LOGIC OR µP G1 2 LTC1157 IN2 1 G2 4 3 GND LOAD LOAD LTC1157 • TA03 Mixed 5V and 3.3V Dual High-Side Switch 5V + 3.3V 10µF 6.3V RFD16N05SM VS IN1 CONTROL LOGIC OR µP + MTD10N05E 10µF 4V 51k G1 LTC1157 IN2 51k G2 GND 5V LOAD 3.3V LOAD LTC1157 • TA04 Mixed 3.3V and 12V High- and Low-Side Switching 3.3V + 12V 10µF 4V + IRLR024 12V LOAD VS CONTROL LOGIC OR µP IN1 G1 LTC1157 IN2 30k G2 GND 10µF 16V MTD3055EL 3.3V LOAD LTC1157 • TA05 6 LTC1157 U TYPICAL APPLICATIO S Ultra Low Voltage Drop Battery Switch with Reverse Battery Protection, Ramped Output and 3µA Standby Current 5,6,7,8 1 3 + 3 TO 4 CELL BATTERY PACK SWITCHED (RAMPED) BATTERY Si9956DY 0.47µF 2 4 + VS IN1 CONTROL LOGIC OR µP 100µF 6.3V G1 LTC1157 IN2 100k 1k G2 GND 0.1µF 300Ω LTC1157 • TA06 Generating 3.3V and 5V from a 3.3V or 5V Source (Automatic Switching) 3.3V OR 5V 1M 1M 1 7,8 2 3 5,6 Si9956DY 4 VS IN1 G1 7,8 1 G2 2 5,6 3 LTC1157 IN2 GND 2N7002 4 *20µH 1 1M + 6 180µF 6V ILIM 2 AO SW2 430k SET FB GND 5 Si9956DY 120µF/10V MBRS12OT3 2N7002 *20µH 4 39Ω ZTX869-M1 LT1111 7 3.3V/150mA + 3 VIN SW1 5V/150mA 8 47Ω 105k 1% 174k 1% 140k 1% + 100µF 6V LTC1157 • TA07 *CTX20-3 COILTRONICS 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. 7 LTC1157 U TYPICAL APPLICATIO S 3.3V Ultra Low Voltage Drop Regulator with Optional Reverse Battery Protection and 3µA Standby Current Q1 IRLR024* + + 3 TO 4 CELL BATTERY PACK Q2 IRLR024 C1 10µF VS IN1 CONTROL LOGIC OR µP G1 IN2 1 R5 100k LTC1157 G2 LT1431 GND 5 R1 300Ω* 3.3V/1A 3 C2 330pF R3 3.3k 8 + 6 R2 680Ω C3 220µF R4 10k LTC1157 • TA08 *OPTIONAL REVERSE BATTERY PROTECTION. ADD R1 IN SERIES WITH THE GROUND LEAD AND ADD Q1 IN SERIES WITH THE BATTERY AS SHOWN. U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N Package 8-Lead Plastic DIP 0.300 – 0.320 (7.620 – 8.128) 0.045 – 0.065 (1.143 – 1.651) +0.025 0.325 –0.015 8.255 +0.635 –0.381 0.130 ± 0.005 (3.302 ± 0.127) 8 7 0.125 (3.175) MIN 0.100 ± 0.010 (2.540 ± 0.254) 0.020 (0.508) MIN 1 2 0.010 – 0.020 × 45° (0.254 – 0.508) 4 3 0.018 ± 0.003 (0.457 ± 0.076) N8 0392 S Package 8-Lead SOIC 0.189 – 0.197 (4.801 – 5.004) 8 0.053 – 0.069 (1.346 – 1.752) 7 6 5 0.004 – 0.010 (0.101 – 0.254) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 5 0.250 ± 0.010 (6.350 ± 0.254) 0.045 ± 0.015 (1.143 ± 0.381) ) 0.016 – 0.050 0.406 – 1.270 6 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) ( 0.400 (10.160) MAX 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157 (3.810 – 3.988) SO8 0392 1 8 Linear Technology Corporation 2 3 4 LT/GP 0193 10K REV 0 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1993