MIC74 Evaluation Board Micrel MIC74 Evaluation Board SMBus™ I/O Expander and Fan Controller Evaluation Board User configurable jumpers allow each of the MIC74’s I/O lines to be used as an input or output, or the high-order lines can be configured for fan speed control. An MIC29152, a highcurrent low-dropout regulator, is included to drive common 12V brushless DC fans. A 4-pin connector is provided to interface the evaluation board with a serial bus host such as the IPort™, an I2C™ Host Adapter from MCC Corp. This connector is commonly used for interoperability testing among SMBus™ or ACCESS.bus hosts and peripherals. For more information regarding the IPort™ I2C™ Host Adapter and the I2C™ Message Manager™ Software, see Appendix A. General Description This evaluation board demonstrates use of the MIC74 Serial I/O expander and fan controller. It is designed to support rapid prototyping of circuits employing the MIC74 as an I/O expander and/or a fan speed controller. Support is included for dual power supplies in order to demonstrate the 5V-tolerant I/O capabilities of the MIC74. An MIC5205 150mA LDO regulator can be configured to supply 3.3V to the MIC74 while the other circuitry is supplied from a single external 5V supply. +2.7 - 3.3V Input +5V Input Fan supply terminal JP20 MIC74BSM-16 J1 5V J2 VDD J3 12V MIC 29152BU 0000 X LED0 Slave address jumpers JP17 - JP19 A0 JP20 A1 U1 A2 I0 Output jumpers JP9 - JP16 & LEDs I1 I2 I3 Input jumpers JP1 - JP8 I4 /SHDN I5 /FS0 I6 /FS1 J4 VOUT LED7 07 Fan mode jumpers /FS2JP23 - JP26 I7 JP21 TP1 TP2 + Fan terminals - TP3 (DATA) TP2 (/ALERT) (CLOCK) TP1 TP3 JP21 JP22 J5 GND J6 GND CON1 Ground JP22 Ground Host connections MIC74 Evaluation Board Jumper and Connector Layout SMBus™ is a trademark of Intel Corporation. I2C™ is a trademark of Philips Electronics, N.V. IPort™ and Message Manager™ are trademarks of Microcomputer Control Corporation. Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com August 2000 1 MIC74 2 1 3 5 7 9 11 13 15 17 19 JP22 TP3 R1 10k 14 16 4 6 8 10 12 14 16 18 20 2 8 1 2 3 15 TP1 TP2 R16 1.8k 13 2 1 2 JP21 1 3 CON1 GND +5V SMB_D Molex 4 SMB_C J2 VDD JP20 2 1 JP17 A0 3 2 1 JP18 A1 3 2 1 JP19 A2 3 2 1 P3 P2 P1 P0 12 4 5 6 7 9 10 11 Figure 1. Evaluation Board Schematic A2 A1 A0 GND U1 MIC74BMM P7/FS2 VDD CLK P6/FS1 P5/FS0 DATA /ALERT P4/SHDN C1 0.01µF LED0 1 2 J5 GND 3 1 MIC5205-3.3BM5 IN OUT C4 EN BYP 2.2µF 10V GND 2 JP1 IN0 JP9 OUT0 R9 LED1 1 2 JP10 OUT1 R8 LED2 1 2 2 JP2 IN1 3 1 R7 LED3 JP11 OUT2 C2 0.01µF 3 1 1 2 2 1 2 JP4 IN3 2 JP3 IN2 3 1 R6 LED4 R2–R9 1kΩ 1 JP12 OUT3 R5 LED5 JP13 OUT4 3 JP5 IN4 2 C5 0.01µF 3 1 1 2 JP14 OUT5 R4 LED6 1 2 J1 +5V 3 JP6 IN5 2 1 2 JP15 OUT6 R3 LED7 1 R10 3.3k 1 2 JP23 /SHDN 1 2 R2 JP16 OUT7 3 1 JP7 IN6 2 JP8 IN7 2 EN IN 3 GND FB OUT MIC29152BU 5 4 RMIN 1k RFB 3.01k RF0 3.6k JP26 /FS0 1 2 C3 22µF 20V RF1 RF2 1.8k 1k JP25 /FS1 1 2 JP24 /FS2 MIC74 1 2 J3 +12V J6 GND J4 VOUT MIC74 Evaluation Board Micrel August 2000 MIC74 Evaluation Board Micrel Getting Started Powering the Board What’s Included Review the packing list in Table 1 to confirm that you received all listed items. If any of the items are missing or damaged, contact Micrel Semiconductor. The absolute latest version of all Micrel device datasheets may be obtained from our website at www.micrel.com. The MIC74 evaluation board supports the use of dual power supplies in order to demonstrate and make use of the MIC74’s voltage-tolerant I/O capability. The LED indicators can be powered from a 5V supply while the MIC74 is powered from a lower voltage (2.7 to 3.6V). The MIC29152 linear regulator in the optional fan control section requires a third, higher voltage power supply. Three options are available for powering the digital section of the evaluation board. Note that in all cases, the pull-up resistors on /ALERT and the serial data line are connected to the supply voltage present at J1. Option 1: An MIC5205-3.3BM5 linear regulator, U2, permits powering the board from a single 5V power supply connected to J1 when a shorting block is installed at location JP20. The MIC5205 generates the lower voltage (3.3V) required by the MIC74 and feeds its VDD input via JP20. The LED’s indicators on the board are powered from the 5V supply connected to J1. JP21 should be removed or the 5V supply will be fed to pin 3 of the serial bus connector, CON1. Note that the pull-up resistors on /ALERT and the serial data line are connected to the supply voltage present at J1. The 3.3V output of U2 will be present at J2. Option 2: The board can be powered via CON1 by a single 5V power supply connected to pin 3 when a shorting block is installed at locations JP20 and JP21. The MIC5205 generates the lower voltage (3.3V) required by the MIC74 and feeds its VDD input via JP20. The supply voltage applied at CON1 will also be present at J1. The LED’s indicators on the board are powered from the 5V supply connected to CON1. The pull-up resistors on /ALERT and the serial data line are connected to the supply voltage present at pin 3 of CON1. The 3.3V output of U2 will be present at J2. Option 3: A single power supply between 2.7V and 3.6V can power the entire evaluation board via J1 and J2. J1 and J2 should be connected together and JP20 is removed. This isolates the MIC5205 from the circuit and ties both sections together. The LED indicators will be powered from the same supply as the MIC74. JP21 should be removed or the supply voltage will be fed to pin 3 of the serial bus connector, CON1. Note that the pull-up resistors on /ALERT and the serial data line are connected to the supply voltage present at J1. These options are summarized in Table 2. For each case, the terminal used as the power supply input is highlighted in bold. Item Qty Description 1 1 MIC74 Evaluation Board with Jumpers Installed 2 1 MIC74 Evaluation Board User's Manual 3 1 MIC74 Data Sheet 4 2 MIC74BQS Samples 5 1 MIC29152 Data Sheet 6 2 MIC29152BU Samples 7 1 MIC5205 Data Sheet 8 2 MIC5205-3.3BM5 Samples Table 1. Packing List What You Must Provide The following items are required for use with the MIC74 Evaluation Board: • 5V, 100mA regulated power supply • Power supply leads or cables • SMBus/I2C compatible serial bus host for communication with the MIC74 • Cable for serial host connection • 12V-power supply rated to deliver the required fan current* • 12V brushless DC fan rated at no more than 1.5A maximum* * Required only for fan control applications The following additional items are useful, but not required: • Logic probe(s) • Voltmeter(s) • SMBus/I2C bus analyzer Option Description J1 J2 CON1:3 JP20 JP21 Single 5V suppy via J1; supply fed to CON1:3 5V Supply Input 3.3V Present 5V Present Shorted Shorted Single 5V suppy via J1; supply not fed to CON1:3 5V Supply Input 3.3V Present Open Shorted Open Single 5V suppy via CON1 5V Present 3.3V Present 5V Supply Input Shorted Shorted Single 2.7 to 3.3V supply; supply fed to CON1:3 3V Supply Input Connect to J1 Supply Voltage Present Open Shorted Single 2.7 to 3.3V supply; supply not fed to CON1:3 3V Supply Input Connect to J1 Open Open Open Table 2. Options for Powering the Evaluation Board August 2000 3 MIC74 MIC74 Evaluation Board Micrel For fan control applications, an additional power supply is connected to J3. This is nominally a 12V supply, but may be higher, limited only by the MIC29152’s maximum input voltage of 26V. Care must be taken, however, to insure that the maximum power dissipation of the regulator is not exceeded. If the regulator overheats, its internal thermal shutdown circuitry will deactivate it. See MIC29152 datasheet. Any of the power supply arrangements listed in Table 2 may be used in conjunction with a fan power supply at J3. There are eight possible slave addressess. Table 4 shows each of the jumper settings and resulting slave addresses. Jumper Settings MIC74 Slave Address JP19 JP18 JP17 A2 A0 A1 Binary Hex GND GND GND 010 0000b 20h GND GND 5V 010 0001b 21h Serial Bus Host GND 5V GND 010 0010b 22h The connector provided for the serial bus host is a Molex part number 15-83-0064, 4-conductor shielded receptacle. The pinout of this connector is shown below. The mating connector is Molex part number 15-83-1564. See Appendix A for more information on these connectors. The serial bus signals are also present on dual-row header JP22 and at test points TP1 and TP2. One or more of these connection points can be used in lieu of the specialized connector. The various serial bus connection points are summarized in Table 3 below. GND 5V 5V 010 0011b 23h 5V GND GND 010 0100b 24h 5V GND 5V 010 0101b 25h 5V 5V GND 010 0110b 26h 5V 5V 5V 010 0111b 27h Table 4. Selecting the MIC74 Slave Address Pull-up Resistors FRONT CLK 4 The MIC74 evaluation board includes a pull-up resistor on the serial data line and the MIC74’s /ALERT output, resistors R16 and R1, respectively. The serial clock line also requires a pullup resistor or current source somewhere in the system. If the host does not have a provision for this pull-up, a pull-up resistor will have to be added somewhere on the board, such as between TP2 and J1. Guidelines for sizing this pull-up resistor can be found in the SMBus specification. See source in Appendix A. +5V DATA GND 3 2 1 Molex 15-83-0064 Molex 15-83-0064 Pin# JP22 Pin# Serial Data 2 9 TP1 Serial Clock 4 7 TP2 +5V 3 n/a n/a GND 1 2,5,6,15,17,19 J5,J6 /ALERT n/a 8 TP3 Signal Checkout Test Point Proper operation of all of the MIC74’s various functions can be demonstrated and tested by a series of short exercises. Each I/O pin is tested in its output mode and its input mode, including the generation of interrupts. Lastly, the MIC74’s fan mode operation is verified. If fan mode operation is not desired, this section can be skipped. Input Mode The following steps will configure all I/O pins as inputs and verify that the MIC74 is detecting and passing valid data. 1. Verify that jumpers JP1 - JP8 are adjusted so that all MIC74 inputs will be grounded. See Figure 2. 2. Verify that the address selection jumpers are set to match the slave address that will be used by the host to communicate with the MIC74. 3. Apply power to the MIC74 evaluation board. The MIC74 will be initialized to its default state, all I/Os will be configured as inputs. 4. Read the data register, DATA. The value returned should be 00h = 0000 0000b. 5. Connect any one of the input pins to 5V by moving one of jumpers JP1-JP8. For example, move JP3 to connect input I3 to 5V (logic high). 6. Read the data register, DATA. The value returned should be 08h = 0000 1000b. Table 3. Serial Bus Connection Points Personal computer based host adapters, cables, bus analyzers and other useful items can be obtained from the sources listed in Appendix A. Slave Address Selection Before communication between the serial bus host and the MIC74 can take place, the MIC74’s slave address must be established. Jumpers JP17-19, marked “A0”, “A1”, and “A2” on the PCB establish the slave address by connecting the A0, A1, and A2 pins to 5V or ground. The address of the MIC74 is only registered at power-on and cannot be changed during operation. To change the MIC74’s slave address, power must be removed and then reapplied once the new settings of JP17-19 have been established. The factory setting for the MIC74’s slave address is 010 0000b (JP17 = JP18 = JP19 = GND). MIC74 4 August 2000 MIC74 Evaluation Board Micrel 7. Repeat steps 5 through 6 for each input in turn. 8. Confirm that the correct values were returned. 15. Connect any of the input pins to 5V by moving one of JP1 - JP8. For example, move JP4 to connect input I3 to 5V (logic high). 16. Confirm that /ALERT goes low and remains low indefinitely. 17. Clear the interrupt by reading STATUS. The value returned should match the input pattern. (For example: 08h = 0000 1000b) 18. Verify that /ALERT returns high 19. Read DATA and verify that the value returned matches the input data. (For example: 0000 1000b) 20. Repeat steps 15 through 19 for each input in turn. 21. Remove all power from the MIC74 evaluation board. Wait a few seconds for C4 to discharge. The following additional steps will verify that interrupts are operating properly: 9. Configure jumpers JP1 - JP8 so that all inputs are low. 10. Clear any pending interrupts by reading STATUS 11. Enable interrupts by setting the interrupt enable bit, IE, in the configuration register. 12. Enable interrupts on all inputs by setting all bits in the interrupt mask register. 13. Connect a logic probe or voltmeter to TP3 to monitor the /ALERT output. /ALERT should be in its high state. 14. Read DATA. The data returned should be 0000 0000b. J1 +5V J2 VDD O0 JP19 A0 JP18 U2 C1 JP20 JP17 A2 JP1 JP3 I2 JP4 C4 MIC74 I1 JP2 J3 12V R9 MIC5205 A1 I0 LED0 U3 O1 R8 O2 R7 O3 R6 R10 O4 R5 O5 R4 RFB R3 R2 /SHDN JP6 I5 /FS0 O7 LED7 RF0 C2 JP7 I6 J4 VOUT RF1 JP5 I4 U1 RMIN RF2 O6 I3 MIC29152BU C3 R1 /FS1 JP8 I7 /FS2 JP21 J5 GND R16 TP2 Molex Connector 71565 JP22 TP1 TP3 1 J6 GND 2 Figure 2. Input Configuration August 2000 5 MIC74 MIC74 Evaluation Board Micrel Output Mode The following steps will configure all I/O pins as outputs and verify that the MIC74 is passing valid data. 1. Completely remove the jumpers from JP1 to JP8 and connect them to JP9 - JP16 to configure all I/Os to drive the LED’s. See Figure 3 below. 2. Apply power to the board. The MIC74 will be initialized to its power-up state. 3. Verify that all the LEDs are off at this point. 4. Configure all I/Os as outputs by setting all bits in the data direction register, i.e., write DIR with FFh. J1 +5V J2 VDD JP9 O0 A0 U2 MIC5205 O1 A1 JP20 C1 A2 I0 I1 I2 O3 LED0 J3 12V R9 JP10 R8 JP11 R7 MIC29152BU R6 R10 O4 O5 O6 I3 RFB R4 /SHDN I5 /FS0 R3 RF1 I6 /FS1 I7 /FS2 R2 O7 J4 VOUT RF2 JP15 JP16 I4 RMIN R5 JP14 U3 U1 JP12 JP13 MIC74 C4 O2 5. Set all I/Os to their high (open-drain) state by setting all bits in DATA, i.e., write DATA with FFh 6. Verify that all the LEDs are off at this point. 7. Clear any bit in the data register. For example, write DATA with F7h = 1111 0111b to clear output #3. 8. Verify that LED #3 turns on and all other LED’s are off. 9. Repeat steps 7 and 8 for each output bit. 10. Remove all power from the MIC74 evaluation board. Wait a few seconds for C4 to discharge. LED7 RF0 C2 C3 R1 JP21 J5 GND R16 TP2 Molex Connector 71565 JP22 TP1 TP3 1 J6 GND 2 Figure 3. Output Configuration MIC74 6 August 2000 MIC74 Evaluation Board Micrel Fan Mode The following steps will configure the board for fan speed control and verify proper operation. 1. Remove the eight jumpers from JP1 - JP8 and use four of the jumpers to short JP23 - JP26. See Figure 4 below. 2. Connect the positive lead of the 12V fan to J4 (MIC29152’s output) and the negative wire of the 12V fan to J6 (Ground). 3. Apply power to the board. The MIC74 will be initialized to its power-up state. See the datasheet Applications section. 4. Connect the 12V power supply to the MIC29152’s input at J3. 5. Verify that the fan comes on at its minimum speed. (It will remain in this state while the MIC74 is programmed for fan mode.) J1 +5V J2 VDD LED0 O0 A0 U2 J3 12V R9 MIC5205 A1 JP20 C1 A2 I0 6. Enable fan mode by setting the fan bit in DEV_CFG, i.e., write DEV_CFG with 02h. 7. Select the desired speed by writing to FAN_SPEED. (Table 3 shows the output voltage for the seven available speeds.) 8. Verify by observation that the fan speed changes. 9. Verify that the output voltage of the MIC29152 is close to the value given in Table 3 (This voltage will vary slightly due to resistor tolerances, component accuracy, etc.) 10. Repeat steps six and seven for each possible fan speed value. 11. Remove all power from the MIC74 evaluation board. Wait a few seconds for C4 to discharge. MIC74 C4 I1 I2 U3 O1 R8 O2 R7 O3 R6 R10 O4 R5 O5 R4 RFB R3 R2 /SHDN JP26 I5 /FS0 O7 LED7 RF0 C2 JP25 I6 J4 VOUT RF1 JP23 I4 U1 RMIN RF2 O6 I3 MIC29152BU C3 R1 /FS1 JP24 I7 /FS2 JP21 J5 GND R16 TP2 Molex Connector 71565 JP22 TP1 TP3 1 J6 GND 2 Figure 4. Fan Configuration August 2000 7 MIC74 MIC74 Evaluation Board Micrel resistance that results from the parallel combination of RF0, RF1, RF2, RMIN, as applicable for each speed setting. Refer to the Applications section of the MIC74 datasheet for a detailed explanation of fan mode and how to select resistors for a given application. Table 5 lists the fan speed and MIC29152 output voltage produced by a given value written into FAN_SPEED. The actual measured voltage may vary slightly from the values shown in the table due to resistor tolerances, component accuracy, etc. REQ in the table is the equivalent feedback FAN_SPEED Value Fan Speed Selected 0000 0000b RFB RMIN power-up 3k 0000 0000b fan off 0000 0001b RF2 RF1 RF0 REQ VOUT 1k open open open 1k 4.96V 3k 1k open open open 1k 0V lowest 3k 1k open open 3.6k 783 5.99V 0000 0010b 2nd lowest 3k 1k open 1.8k open 643 7.03V 0000 0011b 3rd lowest 3k 1k open 1.8k 3.6k 545 8.06V 0000 0100b medium 3k 1k 1k open open 500 8.68V 0000 0101b 3rd highest 3k 1k 1k open 3.6k 439 9.71V 0000 0110b 2nd highest 3k 1k 1k 1.8k open 391 10.75V 0000 0111b highest 3k 1k 1k 1.8k 3.6k 353 11.78V Table 5. Fan Drive Voltages vs. Value in FAN_SPEED Hardware Reference Designator Description Designator Description J1 5V Power Supply Input TP1 DATA J2 MIC74's VDD Input TP2 CLOCK J3 12V Power Supply Input TP3 /ALERT J4 Fan Drive Voltage (MIC29152 VOUT) J5 Ground J6 Ground Table 7. Test Points Table 6. Terminals MIC74 8 August 2000 MIC74 Evaluation Board Micrel Jumper Position Function Factory Setting JP1 1 to 2 2 to 3 Connect P0 to Ground in the input mode Connect P0 to 5V in the input mode Shorted Open JP2 1 to 2 2 to 3 Connect P1 to Ground in the input mode Connect P1 to 5V in the input mode Shorted Open JP3 1 to 2 2 to 3 Connect P2 to Ground in the input mode Connect P2 to 5V in the input mode Shorted Open JP4 1 to 2 2 to 3 Connect P3 to Ground in the input mode Connect P3 to 5V in the input mode Shorted Open JP5 1 to 2 2 to 3 Connect P4 to Ground in the input mode Connect P4 to 5V in the input mode Shorted Open JP6 1 to 2 2 to 3 Connect P5 to Ground in the input mode Connect P5 to 5V in the input mode Shorted Open JP7 1 to 2 2 to 3 Connect P6 to Ground in the input mode Connect P6 to 5V in the input mode Shorted Open JP8 1 to 2 2 to 3 Connect P7 to Ground in the input mode Connect P7 to 5V in the input mode Shorted Open JP9 1 to 2 Connect LED0 to P0 in open-drain output mode Open JP10 1 to 2 Connect LED1 to P1 in open-drain output mode Open JP11 1 to 2 Connect LED2 to P2 in open-drain output mode Open JP12 1 to 2 Connect LED3 to P3 in open-drain output mode Open JP13 1 to 2 Connect LED4 to P4 in open-drain output mode Open JP14 1 to 2 Connect LED5 to P5 in open-drain output mode Open JP15 1 to 2 Connect LED6 to P6 in open-drain output mode Open JP16 1 to 2 Connect LED7 to P7 in open-drain output mode Open JP17 1 to 2 2 to 3 Connect A0 to 5V Connect A0 to Ground Open Shorted JP18 1 to 2 2 to 3 Connect A1 to 5V Connect A1 to Ground Open Shorted JP19 1 to 2 2 to 3 Connect A2 to 5V Connect A2 to Ground Open Shorted JP20 1 to 2 Provide 3.3V to the MIC74 Open JP21 1 to 2 Use 5V from the Molex Connector Open JP23 1 to 2 Connect MIC29152's enable pin to /SHDN pin in fan mode Open JP24 1 to 2 Connect RF2 to /FS2 pin in fan mode Open JP25 1 to 2 Connect RF1 to /FS1 pin in fan mode Open JP26 1 to 2 Connect RF0 to /FS0 pin in fan mode Open Table 8. Jumper Options August 2000 9 MIC74 MIC74 Evaluation Board Micrel Printed Circuit Layouts MIC74 Top-Side Silk Screen Bottom-Side Silk Screen Top-Side Copper Bottom-Side Copper 10 August 2000 MIC74 Evaluation Board Micrel Bill of Materials Item Part Number C1, C2, C5 08055C103MAT2 Manufacturer Description Qty. AVX 0.01µF 50V 3 C3 TPSC226M016R0375 AVX 22µF 16V 1 C4 TAJA225M010R AVX 2.2µF 10V 1 LED0–LED7 LTC-16KE LED 8 R1 CRCW08051002FRT1 Vishay-Dale 10k ±1%, size 0805 or 1206 1 R10 CRCW08053301FRT1 Vishay-Dale 3.3k ±1%, size 0805 or 1206 1 RF0 CRCW08053601FRT1 Vishay-Dale 3.6k ±1%, size 0805 or 1206 1 RF1, R16 CRCW08051801FRT1 Vishay-Dale 1.8k ±1%, size 0805 or 1206 2 RMIN, RF2, R2–R9 CRCW08051001FRT1 Vishay-Dale 1k ±1%, size 0805 or 1206 10 RFB CRCW08053011FRT1 Vishay-Dale 3.01k ±1%, size 0805 or 1206 1 U1 MIC29152-BU Micrel High-Current LDO Regulator 1 U2 MIC5205-3.3BM5 Micrel 150mA Low-Noise LDO Regulator 1 U3 MIC74BMM Micrel SMBus™ I/O Expander and Fan Controller 1 CON1 15-83-0064 Molex 4-position female connector 1 August 2000 Vishay Lite-On 11 MIC74 MIC74 Evaluation Board Micrel The current SMBus specification and other information regarding SMBus may be obtained from the SMBus website SMBus Forum (website) http://www.smbus.org. Appendix A: SMBus Resources* PC host adapters and software, bus analyzers, cables, and other items can be purchased from: Micro Computer Control Corporation PO Box 275/ 17 Model Ave Hopewell, New Jersey 08525 USA Telephone: 609-466-1751 Email: [email protected] http://www.mcc-us.com *Micrel does not necessarily endorse or recommend any of the products, services, or information sources listed above. Micrel is not affiliated in any way with any listed company, person, or other entity. The above information is presented without warranty of any kind. The 4-conductor serial bus connector is available from Molex as part number 15-83-0064. Mating plugs for constructing cable assemblies are also available. A list of distributors is available on the Molex website. Molex Incorporated 2222 Wellington Court Lisle, IL 60532-1682 Tel: 800/78MOLEX, 630/969-4550 (Outside USA) Fax: 630/968-8356 Telex: 254069 E-mail: [email protected] http://www.molex.com MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL USA + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 2000 Micrel Incorporated MIC74 12 August 2000