LTC1623 SMBus Dual High Side Switch Controller U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ SMBus and I2C Compatible Built-In Charge Pumps Drive N-Channel Switches 16 Available Switches on the Same Bus 0.6V VIL and 1.4V VIH for DATA and CLK Available in 8-Lead MSOP and S0 Packages Low Standby Current: 14µA Eight Addresses from Two Three-State Address Pins Internal Power-On Reset Timer Internal Undervoltage Lockout No Need for External Pull-Up Resistors at Output No Need for Secondary Power Source The LTC ®1623 SMBus switch controller is a slave device that controls two high-side N-channel MOSFETs on either the SMBus or the I2C bus. The LTC1623 operates with an input voltage from 2.7V to 5.5V with a low standby current of 14µA (at 3.3V). In accordance with the SMBus specification, the LTC1623 maintains the 0.6V VIL and 1.4V VIH input thresholds throughout the supply voltage range. Using the 2-wire interface, CLK and DATA, the LTC1623 monitors the bus for a start condition (DATA going from high to low while CLK is high). Once detected, the LTC1623 compares its address with the first (address) byte sent over the bus from the master. If matched, the LTC1623 will execute the second (command) byte from the master and independently control the built-in charge pumps to drive two external switches. U APPLICATIONS ■ ■ ■ ■ ■ Computer Peripheral Control Laptop Computer Power Plane Switching Portable Equipment Power Control Industrial Control Systems Handheld Equipment The LTC1623 has two three-state programmable address pins, thus allowing eight different addresses and a total of sixteen available switches on the same bus. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION VCC 2.7V TO 5.5V Gate Drive Voltage 14 TJ = 25°C 10µF CLK GA DATA GB Q1 GATE VOLTAGE (V) (FROM SMBus) Q2 LTC1623 (PROGRAMMABLE) AD0 AD1 GND * SILICONIX Si69260Q 12 * VCC LOAD1 LOAD2 1623 TA01 10 8 6 4 2 0 0 1 2 3 4 SUPPLY VOLTAGE (V) 5 6 1623 G01 1 LTC1623 U W W W ABSOLUTE MAXIMUM RATINGS (Voltages Referred to GND Pin) Input Supply Voltage (VCC) ..........................– 0.3V to 6V DATA, CLK (Bus Pins 1, 2) ..........................– 0.3V to 6V AD0, AD1 (Address Pins 3, 5) ..... – 0.3V to (VCC + 0.3V) GA,GB (Gate Drive Pins 6, 7) .......... – 0.3V to (VCC + 7V) Junction Temperature ........................................... 125°C Operating Temperature Range LTC1623C.................................................. 0° to 70°C LTC1623I ............................................ –40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C W U U PACKAGE/ORDER INFORMATION ORDER PART NUMBER TOP VIEW DATA CLK AD0 GND 1 2 3 4 8 7 6 5 VCC GA GB AD1 MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 150°C/ W LTC1623CMS8 MS8 PART MARKING ORDER PART NUMBER TOP VIEW DATA 1 8 VCC CLK 2 7 GA AD0 3 6 GB GND 4 5 AD1 LTC1623CS8 LTC1623IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO LTCH 1623 1623I TJMAX = 125°C, θJA = 110°C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER TA = 25°C, VCC = 5V unless otherwise specified. CGA = 1000pF, CGB = 1000pF CONDITIONS MIN VCC Operating Supply Voltage Range IVCC Supply Current Charge Pump Off, AD0 and AD1High or Low, VCC = 2.7V DATA and CLK High VCC = 3.3V VCC = 5V ● ● ● IVCC Supply Current GA or GB High (Command Byte 00000001 or 00000010) Both GA and GB High (Command Byte 00000011) ● ● VGS Gate Voltage Above Supply VCC = 2.7V VCC = 3.3V VCC = 5.5V ● ● ● 2.7 4.5 4.5 VUVLO Undervoltage Lockout Falling Edge (Note1) ● 1.5 tPOR Power-On Reset Delay Time VCC = 2.7V (Note2) VCC = 5.5V fOSC Charge Pump Oscillator Frequency (Note 3) tON Turn-On Time into 1000pF tOFF TYP MAX UNITS 5.5 V 12 14 17 30 30 30 µA µA µA 140 162 250 250 µA µA 4.2 5.4 6.4 7 7 7 V V V 2.7 2.0 2.5 V 300 300 1000 1000 µs µs 300 kHz VCC = 2.7V (From ON to GA, GB = VCC + 1V) (Note 4) VCC = 5.5V (From ON to GA, GB = VCC + 2V) (Note 4) 170 180 µs µs Turn-Off Time into 1000pF VCC = 2.7V (From OFF to GA, GB = 100mV) (Note 5) VCC = 5.5V (From OFF to GA, GB = 100mV) (Note 5) 17 12 µs µs VIL DATA/CLK Input Low Voltage VCC = 2.7V to 5.5V VIH DATA/CLK Input High Voltage VCC = 2.7V to 5.5V 2 0.6 1.4 V V LTC1623 ELECTRICAL CHARACTERISTICS TA = 25°C, VCC = 5V unless otherwise specified. CGA = 1000pF, CGB = 1000pF SYMBOL PARAMETER CONDITIONS MIN VIL AD0 and AD1 Input Low Voltage VCC = 2.7V to 5.5V ● VIH AD0 and AD1 Input High Voltage VCC = 2.7V to 5.5V ● VOL Data Output Low Voltage VCC = 2.7 to 5.5V, IPULLUP = 350µA ● CIN Input Capacitance (DATA, CLK, AD0, AD1) IIN Input Leakage Current (DATA, CLK) TYP MAX 0.2 VCC – 0.2 V V 0.22 0.4 5 Input Leakage Current(AD0, AD1) UNITS V pF ±1 µA ±250 nA 100 kHz SMBus Related Specs (Note 6) fSMB SMBus Operating Frequency 10 tSUSTA Start Condition Setup Time 4.7 µs tBUF Bus Free Time Between Stop and Start 4.7 µs tHDSTA Start Condition Hold Time 4.0 µs tSUSTP Stop Condition Setup Time 4.0 µs tHDDAT Data Hold Time 300 ns tSUDAT Data Setup Time 250 ns tLOW Clock Low Period 4.7 tHIGH Clock High Period 4.0 tf Clock /Data Fall Time tr Clock/Data Rise Time IPULLUP Current Through External Pull-Up Resistor on DATA Pin (Data Pull-Down Current Capacity) VCC = 2.7V to 5.5V The ● denotes the specifications which apply over the full operating temperature range. Note 1: Approximately 3% hysteresis is provided to ensure stable operation and eliminate false triggering by minor VCC glitches. Note 2: Measured from VCC > VUVLO to SMBus ready for data input. Note 3: The oscillator frequency is not tested directly but is inferred from turn-on time. 100 µs 50 µs 300 ns 1000 ns 350 µA Note 4: ON is enabled upon receiving the Stop condition from the SMBus master. Note 5: OFF is enabled upon receiving the Stop condition from the SMBus master. Note 6: SMBus timing specs are guaranteed but not tested. U U U PIN FUNCTIONS DATA: (Pin 1) Open-Drain Connected Serial Data Interface. Must be pulled high to VCC with external resistor. The pull-up current must be limited to 350µA. AD1: (Pin 5) Higher Three-State Programmable Address Pin. Must be connected directly to VCC, GND, or VCC /2 (using two resistors ≤ 1M). Do not float this pin. CLK: (Pin 2) Serial Clock Interface. Must be pulled high to VCC with external resistor. The pull-up current must be limited to 350µA. GB: (Pin 6) Gate Drive to External High-Side Switch. Fully enhanced by internal charge pump. Controlled by 2nd LSB of command byte. AD0: (Pin 3) Lower Three-State Programmable Address Pin. Must be connected directly to VCC, GND, or VCC /2 (using two resistors ≤ 1M). Do not float this pin. GA: (Pin 7) Gate Drive to External High-Side Switch. Fully enhanced by internal charge pump. Controlled by LSB of command byte. GND: (Pin 4) Ground. VCC: (Pin 8) Input Supply Voltage. Range from 2.7V to 5.5V. 3 LTC1623 U W TYPICAL PERFORMANCE CHARACTERISTICS Supply Current 400 30 350 SUPPLY CURRENT (µA) STANDBY CURRENT (µA) Standby Current 35 25 20 VCC = 5V 15 VCC = 2.7V 10 5 VCC = 2.7V 300 250 200 150 BOTH CHANNELS ON 100 ONE CHANNEL ON 50 0 20 40 60 –60 –40 –20 0 TEMPERATURE (°C) 80 0 –60 –40 –20 100 0 20 40 60 Supply Current Supply Current 400 400 VCC = 5V 350 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 350 300 250 200 BOTH CHANNELS ON 150 ONE CHANNEL ON 100 50 VCC = 6V 300 250 BOTH CHANNELS ON 200 ONE CHANNEL ON 150 100 50 0 –60 –40 –20 0 40 20 80 60 0 –60 –40 –20 100 TEMPERATURE (°C) 0 20 40 60 tON vs Temperature tOFF vs Temperature 450 18 400 16 350 14 300 12 tOFF (µs) 20 250 150 VCC = 2.7V VCC = 5.5V VCC = 2.7V VCC = 5.5V 10 8 6 100 4 50 2 0 –60 –40 –20 100 1623 G05 500 200 80 TEMPERATURE (°C) 1623 G03 tON (µs) 100 1623 G04 1623 G02 0 20 40 60 80 100 TEMPERATURE (°C) 0 –60 –40 –20 0 20 40 60 80 100 TEMPERATURE (°C) 1623 G06 4 80 TEMPERATURE (°C) 1623 G07 LTC1623 U W TYPICAL PERFORMANCE CHARACTERISTICS GA, GB Output Voltage DATA VOL vs Temperature 16 14 500 VCC = 5V VCC = 5V I PULLUP = 350µA 450 DATA VOL (mV) OUTPUT VOLTAGE (V) 400 12 10 8 6 350 300 250 200 150 4 100 2 50 0 –60 –40 –20 0 20 40 60 80 0 –60 –40 –20 100 TEMPERATURE (°C) 0 20 1623 G08 VGS vs Temperature 80 100 Gate Drive Current 100 VCC = 5.5V VCC = 6V GATE CURRENT (µA) 5 VCC = 3.3V Vgs (V) 60 1623 G09 7 6 40 TEMPERATURE (°C) 4 VCC = 2.7V 3 2 VCC = 5V 10 VCC = 3.3V VCC = 2.7V 1 1 0 20 40 60 –60 –40 –20 0 TEMPERATURE (°C) 80 100 1623 G10 0.1 0 2 3 4 5 6 1 GATE VOLTAGE ABOVE SUPPLY (VGS) 7 1623 G11 5 LTC1623 WU W TI I G DIAGRA tHDSTA tHIGH tr tf tSUSTP CLK t HDDAT t SUSTA tLOW tSUDAT DATA STOP START 1623 TD01 W FU CTIO AL BLOCK DIAGRA U U VCC UNDERVOLTAGE LOCKOUT POWER-ON RESET PORB 2V STARTAND-STOP DETECTORS DATA 1 CLK 2 AD0 3 AD1 5 INPUT BUFFER INPUT BUFFER ADDRESS DECODER SHIFT REGISTER ACK GLUE LOGIC 10k OUTPUT LATCHES COUNTER ADDRESS COMPARATOR 1623 BD 6 REGULATING CHARGE PUMPS 7 GA 10k 6 GB LTC1623 U OPERATIO SMBus Operation SMBus is a serial bus interface that uses only two bus lines, DATA and CLK, to control low power peripheral devices in portable equipment. It consists of masters, also known as hosts, and slave devices. The master of the SMBus is always the one to initiate communications to its slave devices by varying the status of the DATA and CLK lines. The SMBus specification establishes a set of protocols that devices on the bus must follow during communications. The protocol that the LTC1623 uses is the Send Byte Protocol. In this protocol, the master first sends out a Start signal by switching the DATA line from high to low while CLK is high. (Because there may be more than one master on the same bus, an arbitration process takes place if two masters attempt to take control of the DATA line simultaneously; the first master that outputs a one while the other master is zero loses the arbitration and becomes a slave itself.) Upon detecting this Start signal, all slave devices on the bus wake up and get ready to shift in the next byte of data. The master then sends out the first byte. The first seven bits of this byte consist of the address of the device that the master wishes to communicate with. The last bit indicates whether the command will be a read (logic one) or write (logic zero). Because the LTC1623 is a slave device that can only be written to by a master, it will ignore the ensuing commands of the master if it wants to read from the LTC1623, even if the address sent by the master matches that of the LTC1623. After reception of the first byte, the slave device (LTC1623) with the matching address then acknowledges the master by pulling the data line low before the rising edge of the ninth clock cycle. By now, all other nonmatching slave devices will have gone back to their original standby states to wait for the next start signal. Meanwhile, upon receiving the acknowledge from the matching slave, the master then sends out the command byte. In the case of the LTC1623, the two LSBs of this second byte from the master are the signals controlling the status of the external switches; a digital “one” turns on the charge pump to drive up the output gate voltage while a digital “zero” shuts down the charge pump and discharges the output gate voltage to zero. After receiving the command byte, the slave device (LTC1623) needs to again acknowledge the master by pulling the DATA line low on the following clock cycle. The master then ends this Send Byte Protocol by sending the Stop signal, which is a transition from low to high on the DATA line while the CLK line is high. Valid data is shifted into the output latch on the last acknowledge signal; the external switch will not be enabled, however, until the Stop signal is detected. This double-buffering feature allows the user to daisy-chain several differently addressed SMBus devices such that their output executions are synchronous to the Stop signal even though valid data were loaded into their output latches at different times. Figure 1 shows an example of this special protocol. If somehow either the Start or the Stop signal is detected in the middle of a byte, the slave device (LTC1623) will regard this as an error and reject all previous data. Other than the Stop and Start conditions, DATA must be stable during CLK high; DATA can change state only during CLK low. START ADD1 A COMMAND A START ADD2 A COMMAND A START ADD3 A COMMAND A STOP 1623 F01 Figure 1. Daisy-Chaining Multiple SMBus Devices Example of Send Byte Protocol to Slave Address 1011000 Turning GA and GB On CLK START DATA 1 0 1 1 0 0 0 (PROGRAMMABLE) ADDRESS BYTE 0 ACK (WRITE) 0 0 0 0 0 0 1 1 ACK STOP (GB ON)(GA ON) COMMAND BYTE 1623 TD02 7 LTC1623 U OPERATIO Address Charge Pump The LTC1623 has an address of 1011XXX; the four MSBs are hard-wired, but the 3 LSBs are programmed by the user with the help of two three-state address pins. Refer to Table 1 for the pin configurations and their corresponding addresses. To fully enhance the external N-channel switches, an internal charge pump is used to boost the output gate drive to a minimum of 2.7V and a maximum of 6V above VCC, depending on VCC itself. The reason for the maximum output voltage limit is to avoid switch gate source breakdown due to excessive gate overdrive. A feedback network is used to limit the charge pump output to 6V above VCC. Because the output will only need to drive the gate of the external switch by charging and discharging the parasitic gate capacitances, the internal charge pump, clocked by an approximately 300KHz oscillator, is appropriately sized to source less than 100µA. To conserve standby current, it is preferable to tie the address pins to either VCC or GND. If more than four addresses are needed, then either one of the address pins can be tied to the third state of VCC /2 by using two equal value resistors (≤1M) shown in Figure 2. Do not connect both address pins to the VCC /2 state simultaneously because this is not a valid address. Power-On Reset and Undervoltage Lockout The LTC1623 starts up with both gate drives low. An internal power-on reset (POR) signal inhibits operation until about 300µs after VCC crosses the undervoltage lockout threshold (typically 2V). The circuit includes some hysteresis and delay to avoid nuisance resets. Once operation begins, VCC must drop below the threshold for at least 100µs to trigger another POR sequence. Table 1. Address Pin Truth Table AD0 AD1 ADDRESS GND GND 1011000 GND VCC /2 1011001 GND VCC 1011010 VCC /2 GND 1011011 VCC /2 VCC /2 UNUSED VCC /2 VCC 1011100 VCC GND 1011101 VCC VCC /2 1011110 VCC VCC 1011111 DATA CLOCK 1 2 DATA VCC CLK GA During standby, when both gate drive outputs are disabled, quiescent current is kept to a minimum (13µA typical) because only the UVLO block is active. Input Threshold 8 7 1M LTC1623 3 4 Anticipating the trend toward lower supply voltages, the SMBus is specified with a VIH of 1.4V and a VIL of 0.6V. While some SMBus parts may violate this stringent SMBus specification by allowing a higher VIH value for a correspondingly higher input supply voltage, the LTC1623 meets and maintains the constant SMBus input threshold specification across the entire supply voltage range of 2.7V to 5.5V. AD0 GB GND AD1 6 5 1M LOAD1 LOAD2 1623 F02 Figure 2. LTC1623 Programmed with Address 1011001 8 LTC1623 U U W U APPLICATIONS INFORMATION To avoid turning on the external power MOSFETs too quickly, an internal 10k resistor has been placed in series with each of the output gate drive pins (see Functional Block Diagram). Therefore, it only needs an external 0.1µF capacitor to create enough RC delay (10k • 0.1µF = 1ms) to slow down the ramp rate of the output gate drive. In other words, it will take a minimum of 1ms to charge up the external MOSFET. An additional external 1k resistor between the 0.1µF capacitor and the gate of the MOSFET (Figure 3) is required to eliminate possible MOSFET self oscillations. For active-low applications in which the load needs to be on upon power-up, an external P-channel switch can be used (Figure 3). This load can be switched off later after the proper protocol has been sent. Used with the LT ®1431, the LTC1623 makes a 3.3V/3A extremely low voltage drop regulator (Figures 4 and 5). In this application, the other output channel can be used to drive a separate load, or it can also be used to control the output of the LDO so that the user has total control over the switching in and switching out of the LDO (Figure 5). Also, with the help of the LT1304-5, the LTC1623 can be used to make a boost switching regulator with a low standby current of 22µA (Figure 6). VCC 3.5V TO 5.5V VCC 2.7V TO 5.5V 10µF CLK DATA (FROM SMBus) 10µF VCC 1k DATA 0.1µF (PROGRAMMABLE) 1k Q2 Si6433DQ LTC1623 GB 0.1µF AD0 (PROGRAMMABLE) 1k GA Si3442DV 0.1µF LTC1623 GB AD0 Q1 Si3442DV GA CLK (FROM SMBus) VCC Si3442DV AD1 GND 1 GND 5 FAN DISPLAY 510pF 3.3k + 8 LT1431 AD1 VOUT 3.3V 3 470µF LOAD 6V 6 10k 680Ω 1623 F04 1623 F03 Figure 3. Dual Load Switch with Q2 On upon Power-Up Figure 4. 3.3V/3A Extremely Low Voltage Drop Regulator and Load Switch VCC 2.7V TO 4.5V VCC 3.5V TO 5.5V 10µF 10µF (FROM SMBus) CLK DATA VCC (FROM SMBus) LTC1623 GB AD0 (PROGRAMMABLE) Si3442DV GA 1 AD1 GND 510pF 3.3k 8 LT1431 5 VOUT 3.3V 3 + (PROGRAMMABLE) AD0 GB Si3442DV 0.1µF 22µH* 470µF 6V 3 8 + 100µF 1k 0.1µF 1623 TA03 SWITCHED VOUT 3.3V Figure 5. SMBus Controlled Low Dropout Regulator LT1304-5 7 *SUMIDA CD54-220 100k 2 604k Si3442DV 1N5817 4 499k 680Ω LOAD Si3442DV AD1 GND 10k 6 1k V CLK CC GA DATA LTC1623 SHDN + 5V 200mA 2200µF LBO 5 1623 F05 Figure 6. Switching Regulator with Low-Battery Detect Using 22µA Standby Current 9 LTC1623 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.192 ± 0.004 (4.88 ± 0.10) 1 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 2 3 4 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.006 ± 0.004 (0.15 ± 0.102) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 10 MSOP (MS8) 1197 LTC1623 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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. SO8 0996 11 LTC1623 U TYPICAL APPLICATIONS Single Slot PCMCIA 3.3V/5V Switch 5V 10µF VCC 1k Q1 Si3442DY GA CLK DATA TO PC CARD VCC 0V/3.3V/5V 0.1µF Q2* LTC1623 AD0 10k 1µF 1k 1623 TA02 Q3* GB AD1 GND 0.1µF 3.3V *1/2 Si6926DQ LTC1623 Driving Both High Side and Low Side Switches VEXT (30V MAX) VCC 2.7V TO 5.5V LOW SIDE LOAD 10µF VCC 1k GA CLK (FROM SMBus) DATA 0.1µF Si6954DQ 1k Si6954DQ LTC1623 GB (PROGRAMMABLE) 0.1µF AD0 AD1 GND HIGH SIDE LOAD 1623 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1153/LTC1154 Single High Side Micropower MOSFET Drivers Circuit Breaker with Auto Reset LTC1155/LTC1255 Dual High Side Micropower MOSFET Drivers Latch-Off Current Limit LTC1163 Triple 1.8V to 6V High Side MOSFET Driver Three MOSFET Drivers in 8-Lead SO Package LT1304 Micropower DC/DC Converter Low-Battery Detector Active in Shutdown TM LTC1473 Dual PowerPath Switch Matrix Current Limit with Timer LTC1479 PowerPath Controller for Dual Battery Systems Complete Smart Battery Controller PowerPath is a trademark of Linear Technology Corporation. 12 Linear Technology Corporation 1623f LT/TP 0598 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1997