MIC5216 Micrel MIC5216 500mA-Peak Output LDO Regulator Preliminary Information General Description Features The MIC5216 is an efficient linear voltage regulator with high peak output current capability, very low dropout voltage, and better than 1% output voltage accuracy. Dropout is typically 10mV at light loads and less than 500mV at full load. • Error Flag indicates undervoltage fault • Guaranteed 500mA-peak output over the full operating temperature range • Low 500mV maximum dropout voltage at full load • Extremely tight load and line regulation • Tiny SOT-23-5 and MM8™ power MSOP-8 package • Low-noise output • Low temperature coefficient • Current and thermal limiting • Reversed-battery protection • CMOS/TTL-compatible enable/shutdown control • Near-zero shutdown current The MIC5216 is designed to provide a peak output current for startup conditions where higher inrush current is demanded. It features a 500mA peak output rating. Continuous output current is limited only by package and layout. The MIC5216 has an internal undervoltage monitor with a flag output. It also can be enabled or shutdown by a CMOS or TTL compatible signal. When disabled, power consumption drops nearly to zero. Dropout ground current is minimized to help prolong battery life. Other key features include reversedbattery protection, current limiting, overtemperature shutdown, and low noise performance. The MIC5216 is available in fixed output voltages in spacesaving SOT-23-5 and MM8™ 8-lead power MSOP packages. For higher power requirements see the MIC5209 or MIC5237. Applications • • • • • • Laptop, notebook, and palmtop computers Cellular telephones and battery-powered equipment Consumer and personal electronics PC Card VCC and VPP regulation and switching SMPS post-regulator/dc-to-dc modules High-efficiency linear power supplies Ordering Information Part Number Marking Volts Junction Temp. Range Package MIC5216-3.0BMM — 3.0V –40°C to +125°C MSOP-8 MIC5216-3.3BMM — 3.3V –40°C to +125°C MSOP-8 MIC5216-3.6BMM — 3.6V –40°C to +125°C MSOP-8 MIC5216-5.0BMM — 5.0V –40°C to +125°C MSOP-8 MIC5216-3.0BM5 LH30 3.0V –40°C to +125°C SOT-23-5 MIC5216-3.3BM5 LH33 3.3V –40°C to +125°C SOT-23-5 MIC5216-3.6BM5 LH36 3.6V –40°C to +125°C SOT-23-5 MIC5216-5.0BM5 LH50 5.0V –40°C to +125°C SOT-23-5 Typical Applications MIC5216-5.0BMM VIN 6V 100k Flag VOUT 5V 1 8 2 7 3 6 4 5 MIC5216-3.3BM5 VIN 4V 1 2 ENABLE SHUTDOWN 3 VOUT 3.3V 5 100k 4 1.0µF tantalum Flag 1.0µF tantalum 3.3V Low-Noise Regulator 5V Low-Noise Regulator Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com January 2000 1 MIC5216 MIC5216 Micrel Pin Configuration EN 1 8 GND IN 2 7 GND OUT 3 6 GND FLG 4 5 GND EN GND IN 3 2 1 LHxx MIC5216-x.xBMM MM8™ MSOP-8 Fixed Voltages 4 5 FLG OUT MIC5216-x.xBM5 SOT-23-5 Fixed Voltages Pin Description Pin No. MSOP-8 Pin No. SOT-23-5 Pin Name Pin Function 2 1 IN Supply Input 5–8 2 GND Ground: MSOP-8 pins 5 through 8 are internally connected. 3 5 OUT Regulator Output 1 3 EN Enable (Input): CMOS compatible control input. Logic high = enable; logic low or open = shutdown. 4 4 FLG Error Flag (Output): Open-Collector output. Active low indicates an output undervoltage condition. Absolute Maximum Ratings Operating Ratings Supply Input Voltage (VIN) ............................ –20V to +20V Power Dissipation (PD) ............................ Internally Limited Junction Temperature (TJ) ....................... –40°C to +125°C Lead Temperature (Soldering, 5 sec.) ...................... 260°C Supply Input Voltage (VIN) ........................... +2.5V to +12V Enable Input Voltage (VEN) .................................. 0V to VIN Junction Temperature (TJ) ....................... –40°C to +125°C Package Thermal Resistance ........................... see Note 1 MIC5216 2 January 2000 MIC5216 Micrel Electrical Characteristics VIN = VOUT + 1.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted. Symbol Parameter Conditions VOUT Output Voltage Accuracy variation from nominal VOUT ∆VOUT/∆T Output Voltage Temperature Coefficient Note 2 ∆VOUT/VOUT Line Regulation VIN = VOUT + 1V to 12V 0.009 0.05 0.1 %/V ∆VOUT/VOUT Load Regulation IOUT = 100µA to 500mA Note 3 0.05 0.5 0.7 % VIN – VOUT Dropout Voltage, Note 4 IOUT = 100µA 10 60 80 mV IOUT = 50mA 115 175 250 mV IOUT = 150mA 165 300 400 mV IOUT = 500mA 300 500 600 mV VEN ≥ 3.0V, IOUT = 100µA 80 130 170 µA VEN ≥ 3.0V, IOUT = 50mA 350 650 900 µA VEN ≥ 3.0V, IOUT = 150mA 1.8 2.5 3.0 mA VEN ≥ 3.0V, IOUT = 500mA 8 20 25 mA VEN ≤ 0.4V 0.05 3 µA VEN ≤ 0.18V 0.10 8 µA IGND Ground Pin Current, Notes 5, 6 Ground Pin Quiescent Current, Note 6 Min Typical –1 –2 Max Units 1 2 % % 40 ppm/°C PSRR Ripple Rejection f = 120Hz 75 dB ILIMIT Current Limit VOUT = 0V 700 ∆VOUT/∆PD Thermal Regulation Note 7 0.05 %/W eno Output Noise IOUT = 50mA, COUT = 2.2µF 500 nV/ Hz 1000 mA ENABLE Input VENL Enable Input Voltage VENH IENL VEN = logic low (regulator shutdown) VEN = logic high (regulator enabled) Enable Input Current IENH 0.4 0.18 2.0 V V VENL ≤ 0.4V 0.01 –1 µA VENL ≤ 0.18V 0.01 –2 µA VENH ≥ 2.0V 5 20 25 µA –6 –10 % 0.2 0.4 V 0.1 +1 µA Error Flag Output VERR Flag Threshold undervoltage condition (below nominal) Note 8 VIL Output Logic-Low Voltage IL = 1mA, undervoltage condition IFL Flag Leakage Current flag off, VFLAG = 0V to 12V January 2000 3 –2 –1 MIC5216 MIC5216 Micrel Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD(max) = (TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. See Table 1 and the “Thermal Considerations” section for details. Note 2: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 3: Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from 100mA to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. Note 4: Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V differential. Note 5: Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of the load current plus the ground pin current. Note 6: VEN is the voltage externally applied to devices with the EN (enable) input pin. Note 7: Thermal regulation is defined as the change in output voltage at a time “t” after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 500mA load pulse at VIN = 12V for t = 10ms. Note 8: The error flag comparator includes 3% hysteresis. Block Diagrams VIN OUT IN Current Limit Threshold Shutdown VOUT COUT Bandgap Ref. V REF EN FLG Flag 60mV Error Comparator MIC5216-x.xBM5/MM GND MIC5216 Fixed Regulator with External Components MIC5216 4 January 2000 MIC5216 Micrel Typical Characteristics Power Supply Rejection Ratio -40 -60 -80 -100 1k 1E+4 1E+1 10k 1E+5 1M 1E+7 10M 10 1E+2 100k 1E+6 100 1E+3 FREQUENCY (Hz) -60 -100 1k 1E+4 1E+1 10k 1E+5 1M 1E+7 10M 10 1E+2 100k 1E+6 100 1E+3 FREQUENCY (Hz) Noise Performance 10mA, COUT = 1µF IOUT = 100mA 20 1 0.1 0.01 500mA Pending 0.001 10 COUT = 1µF 0 January 2000 0.1 0.2 0.3 VOLTAGE DROP (V) 0.4 NOISE (µV/√Hz) 1mA 10mA IOUT = 100mA COUT = 1µF 10 1 NOISE (µV/√Hz) RIPPLE REJECTION (dB) 500mA pending 50 30 -60 -100 1k 1E+4 1E+1 10k 1E+5 1M 1E+7 10M 10 1E+2 100k 1E+6 100 1E+3 FREQUENCY (Hz) 10 40 -40 Noise Performance 60 VIN = 6V VOUT = 5V -80 IOUT = 1mA COUT = 1µF Power Supply Ripple Rejection vs. Voltage Drop 0 -20 -40 -80 IOUT = 100µA COUT = 1µF 0 VIN = 6V VOUT = 5V -20 PSRR (dB) -20 PSRR (dB) 0 VIN = 6V VOUT = 5V Power Supply Rejection Ratio PSRR (dB) 0 Power Supply Rejection Ratio 5 10mA 0.1 500mA Pending 0.01 0.001 VOUT = 5V 0.0001 10 1E+2 1E+1 1k 1E+4 100 1E+3 10k 1E+5 100k 1E+6 1M 1E+7 10M FREQUENCY (Hz) 100mA VOUT = 5V COUT = 10µF electrolytic 1mA 0.0001 1k 1E+4 10 1E+2 1M 1E+7 10k 1E+5 100k 1E+6 10M 1E+1 100 1E+3 FREQUENCY (Hz) MIC5216 MIC5216 Micrel TJ(MAX) is the maximum junction temperature of the die, 125°C, and TA is the ambient operating temperature. θJA is layout dependent; table 1 shows examples of thermal resistance, junction-to-ambient, for the MIC5216. Applications Information The MIC5216 is designed for 150mA to 200mA output current applications where a high current spike (500mA) is needed for short, startup conditions. Basic application of the device will be discussed initially followed by a more detailed discussion of higher current applications. Enable/Shutdown Forcing EN (enable/shutdown) high (> 2V) enables the regulator. EN is compatible with CMOS logic. If the enable/ shutdown feature is not required, connect EN to IN (supply input). See Figure 5. Input Capacitor MM8™ (MM) 160°C/W 70°C/W 30°C/W SOT-23-5 (M5) 220°C/W 170°C/W 130°C/W The actual power dissipation of the regulator circuit can be determined using one simple equation. PD = (VIN – VOUT) IOUT + VIN IGND Substituting PD(MAX) for PD and solving for the operating conditions that are critical to the application will give the maximum operating conditions for the regulator circuit. For example, if we are operating the MIC5216-3.3BM5 at room temperature, with a minimum footprint layout, we can determine the maximum input voltage for a set output current. An output capacitor is required between OUT and GND to prevent oscillation. 1µF minimum is recommended. Larger values improve the regulator’s transient response. The output capacitor value may be increased without limit. The output capacitor should have an ESR (equivalent series resistance) of about 5Ω or less and a resonant frequency above 1MHz. Ultralow-ESR capacitors could cause oscillation and/or underdamped transient response. Most tantalum or aluminum electrolytic capacitors are adequate; film types will work, but more expensive. Many aluminum electrolytics have electrolytes that freeze at about –30°C, so solid tantalums are recommended for operation below –25°C. At lower values of output current, less output capacitance is needed for stability. The capacitor can be reduced to 0.47µF for current below 10mA or 0.33µF for currents below 1mA. PD(MAX) = (125°C – 25°C) 220°C/W PD(MAX) = 455mW The thermal resistance, junction-to-ambient, for the minimum footprint is 220°C/W, taken from table 1. The maximum power dissipation number cannot be exceeded for proper operation of the device. Using the output voltage of 3.3V, and an output current of 150mA, we can determine the maximum input voltage. Ground current, maximum of 3mA for 150mA of output current, can be taken from the Electrical Characteristics section of the data sheet. 455mW = (VIN – 3.3V) 150mA + VIN × 3mA No-Load Stability The MIC5216 will remain stable and in regulation with no load (other than the internal voltage divider) unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. 455mW + 3.3V (150mA) VIN 150mA + 3mA VIN = 6.2VMAX Error Flag Ouput The error flag is an open-collector output and is active (low) when an undervoltage of approximately 5% below the nominal output voltage is detected. A pullup resistor from IN to FLAG is shown in all schematics. If an error indication is not required, FLAG may be left open and the pullup resistor may be omitted. Therefore, a 3.3V application at 150mA of output current can accept a maximum input voltage of 6.2V in a SOT-23-5 package. For a full discussion of heat sinking and thermal effects on voltage regulators, refer to the Regulator Thermals section of Micrel’s Designing with Low-Dropout Voltage Regulators handbook. Peak Current Applications The MIC5216 is designed for applications where high startup currents are demanded from space constrained regulators. This device will deliver 500mA start-up current from a SOT-23-5 or MM8 package, allowing high power from a very low profile device. The MIC5216 can subsequently provide output current that is only limited by the thermal characteristics of the device. You can obtain higher continuous currents from the device with the proper design. This is easily proved with some thermal calculations. Thermal Considerations The MIC5216 is designed to provide 200mA of continuous current in two very small profile packages. Maximum power dissipation can be calculated based on the output current and the voltage drop across the part. To determine the maximum power dissipation of the package, use the thermal resistance, junction-to-ambient, of the device and the following basic equation. MIC5216 θJC Table 1. MIC5216 Thermal Resistance A 1µF capacitor should be placed from IN to GND if there is more than 10 inches of wire between the input and the ac filter capacitor or if a battery is used as the input. Output Capacitor PD(MAX) = θJA Recommended θJA 1" Square Minimum Footprint Copper Clad Package (TJ(MAX) – TA ) If we look at a specific example, it may be easier to follow. The MIC5216 can be used to provide up to 500mA continuous θ JA 6 January 2000 MIC5216 Micrel output current. First, calculate the maximum power dissipation of the device, as was done in the thermal considerations section. Worst case thermal resistance (θJA = 220°C/W for the MIC5216-x.xBM5), will be used for this example. PD(MAX) = The information used to determine the safe operating regions can be obtained in a similar manner to that used in determining typical power dissipation, already discussed. Determining the maximum power dissipation based on the layout is the first step, this is done in the same manner as in the previous two sections. Then, a larger power dissipation number multiplied by a set maximum duty cycle would give that maximum power dissipation number for the layout. This is best shown through an example. If the application calls for 5V at 500mA for short pulses, but the only supply voltage available is 8V, then the duty cycle has to be adjusted to determine an average power that does not exceed the maximum power dissipation for the layout. (TJ(MAX) – TA ) θ JA Assuming room temperature, we have a maximum power dissipation number of PD(MAX) = (125°C – 25°C) 220°C/W PD = 455mW % DC Avg.PD = V – VOUT IOUT + VIN IGND 100 IN ( Then we can determine the maximum input voltage for a fivevolt regulator operating at 500mA, using worst case ground current. PD(max) = 455mW = (VIN – VOUT) IOUT + VIN IGND ) % DC 455mW = (8V – 5V) 500mA + 8V × 20mA 100 IOUT = 500mA VOUT = 5V IGND = 20mA % Duty Cycle 455mW = 1.66W 100 455mW = (VIN – 5V) 500mA + VIN × 20mA 0.274 = 2.995W = 520mA × VIN % Duty Cycle Max = 27.4% 2.955W VIN(max) = = 5.683V 520mA Therefore, to be able to obtain a constant 500mA output current from the 5216-5.0BM5 at room temperature, you need extremely tight input-output voltage differential, barely above the maximum dropout voltage for that current rating. You can run the part from larger supply voltages if the proper precautions are taken. Varying the duty cycle using the enable pin can increase the power dissipation of the device by maintaining a lower average power figure. This is ideal for applications where high current is only needed in short bursts. Figure 1 shows the safe operating regions for the MIC5216-x.xBM5 at three different ambient temperatures and at different output currents. The data used to determine this figure assumed a minimum footprint PCB design for minimum heat sinking. Figure 2 incorporates the same factors as the first figure, but assumes a much better heat sink. A 1”square copper trace on the PC board reduces the thermal resistance of the device. This improved thermal resistance improves power dissipation and allows for a larger safe operating region. With an output current of 500mA and a three-volt drop across the MIC5216-xxBMM, the maximum duty cycle is 27.4%. Applications also call for a set nominal current output with a greater amount of current needed for short durations. This is a tricky situation, but it is easily remedied. Calculate the average power dissipation for each current section, then add the two numbers giving the total power dissipation for the regulator. For example, if the regulator is operating normally at 50mA, but for 12.5% of the time it operates at 500mA output, the total power dissipation of the part can be easily determined. First, calculate the power dissipation of the device at 50mA. We will use the MIC5216-3.3BM5 with 5V input voltage as our example. PD × 50mA = (5V – 3.3V) × 50mA + 5V × 650µA PD × 50mA = 173mW However, this is continuous power dissipation, the actual on-time for the device at 50mA is (100%-12.5%) or 87.5% of the time, or 87.5% duty cycle. Therefore, PD must be multiplied by the duty cycle to obtain the actual average power dissipation at 50mA. PD × 50mA = 0.875 × 173mW Figures 3 and 4 show safe operating regions for the MIC5216x.xBMM, the power MSOP package part. These graphs show three typical operating regions at different temperatures. The lower the temperature, the larger the operating region. The graphs were obtained in a similar way to the graphs for the MIC5216-x.xBM5, taking all factors into consideration and using two different board layouts, minimum footprint and 1” square copper PC board heat sink. (For further discussion of PC board heat sink characteristics, refer to Application Hint 17, “Designing PC Board Heat Sinks”. January 2000 % Duty Cycle 100 PD × 50mA = 151mW The power dissipation at 500mA must also be calculated. PD × 500mA = (5V – 3.3V) 500mA + 5V × 20mA PD × 500mA = 950mW This number must be multiplied by the duty cycle at which it would be operating, 12.5%. PD × = 0.125 × 950mW PD × = 119mW 7 MIC5216 MIC5216 Micrel 10 10 10 6 200mA 4 300mA 400mA 2 8 100mA 6 200mA 4 300mA 2 400mA 500mA 0 0 20 40 60 80 DUTY CYCLE (%) 0 100 VOLTAGE DROP (V) 8 VOLTAGE DROP (V) VOLTAGE DROP (V) 100mA 0 20 500mA 40 60 80 DUTY CYCLE (%) 8 6 4 200mA 300mA 2 500mA 0 100 100mA 400mA 0 20 40 60 80 DUTY CYCLE (%) 100 a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient Figure 1. MIC5216-x.xBM5 (SOT-23-5) on Minimum Recommended Footprint 10 10 10 6 200mA 300mA 4 400mA 2 8 100mA 6 200mA 4 300mA 2 400mA 500mA 0 0 20 40 60 80 DUTY CYCLE (%) 0 100 VOLTAGE DROP (V) 8 VOLTAGE DROP (V) VOLTAGE DROP (V) 100mA 500mA 0 20 40 60 80 DUTY CYCLE (%) 8 100mA 6 200mA 4 2 0 100 300mA 400mA 0 500mA 20 40 60 80 DUTY CYCLE (%) 100 a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient Figure 2. MIC5216-x.xBM5 (SOT-23-5) on 1-inch2 Copper Cladding 10 10 10 100mA 200mA 6 300mA 4 400mA 2 8 6 200mA 300mA 4 400mA 2 500mA 0 0 20 VOLTAGE DROP (V) 8 VOLTAGE DROP (V) VOLTAGE DROP (V) 100mA 500mA 40 60 80 DUTY CYCLE (%) 0 100 0 20 40 60 80 DUTY CYCLE (%) 8 6 200mA 300mA 4 2 400mA 0 100 100mA 0 500mA 20 40 60 80 DUTY CYCLE (%) 100 a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient Figure 3. MIC5216-x.xBMM (MSOP-8) on Minimum Recommended Footprint 10 8 300mA 6 400mA 4 500mA 2 10 100mA 200mA 8 6 VOLTAGE DROP (V) 200mA VOLTAGE DROP (V) VOLTAGE DROP (V) 10 300mA 400mA 4 500mA 2 8 200mA 6 300mA 4 400mA 2 500mA 0 0 20 40 60 80 DUTY CYCLE (%) 100 0 0 20 40 60 80 DUTY CYCLE (%) 100 0 0 20 40 60 80 DUTY CYCLE (%) 100 a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient Figure 4. MIC5216-x.xBMM (MSOP-8) on 1-inch2 Copper Cladding MIC5216 8 January 2000 MIC5216 Micrel The total power dissipation of the device under these conditions is the sum of the two power dissipation figures. PD(total) = PD × 50mA + PD × 500mA Fixed Regulator Circuits MIC5216 VIN IN PD(total) = 151mW + 119mW EN PD(total) = 270mW The total power dissipation of the regulator is less than the maximum power dissipation of the SOT-23-5 package at room temperature, on a minimum footprint board and therefore would operate properly. FLG GND 1µF 100k Figure 5. Low-Noise Fixed Voltage Regulator Figure 5 shows a basic MIC5216-x.xBMx fixed-voltage regulator circuit. A 1µF minimum output capacitor is required for basic fixed-voltage applications. Multilayer boards with a ground plane, wide traces near the pads, and large supply-bus lines will have better thermal conductivity. For additional heat sink characteristics, please refer to Micrel Application Hint 17, “Designing P.C. Board Heat Sinks”, included in Micrel’s Databook. For a full discussion of heat sinking and thermal effects on voltage regulators, refer to Regulator Thermals section of Micrel’s Designing with LowDropout Voltage Regulators handbook. January 2000 VOUT OUT The flag output is an open-collector output and requires a pull-up resistor to the input voltage. The flag indicates an undervoltage condition on the output of the device. 9 MIC5216 MIC5216 Micrel Package Information 0.199 (5.05) 0.187 (4.74) 0.122 (3.10) 0.112 (2.84) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.007 (0.18) 0.005 (0.13) 0.012 (0.30) R 0.012 (0.03) 0.0256 (0.65) TYP 0.008 (0.20) 0.004 (0.10) 5° MAX 0° MIN 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Pin MSOP (MM) 1.90 (0.075) REF 0.95 (0.037) REF 1.75 (0.069) 1.50 (0.059) 3.00 (0.118) 2.60 (0.102) DIMENSIONS: MM (INCH) 3.02 (0.119) 2.80 (0.110) 0.50 (0.020) 0.35 (0.014) 1.30 (0.051) 0.90 (0.035) 0.20 (0.008) 0.09 (0.004) 10° 0° 0.15 (0.006) 0.00 (0.000) 0.60 (0.024) 0.10 (0.004) SOT-23-5 (M5) MIC5216 10 January 2000 MIC5216 January 2000 Micrel 11 MIC5216 MIC5216 Micrel MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA 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 MIC5216 12 January 2000