MIC5204 Micrel MIC5204 SCSI-II Active Terminator Preliminary Information General Description Features The MIC5204 is an active terminator designed to comply with SCSI-II specifications. The MIC5204 is enabled by a CMOS or TTL compatible logic signal. When disabled, power consumption drops nearly to zero and the output goes into a high impedance state. Key MIC5204 features include protection against reversed battery, current limiting, and overtemperature shutdown. • • • • • • • • • • ± 1% output voltage accuracy Guaranteed 500mA output Low quiescent current Low dropout voltage Extremely tight load and line regulation Very low temperature coefficient Current and thermal limiting Zero off-mode current Logic-controlled electronic shutdown Available in SO-8 and SOT-223 packages 2 Applications • • • • • • SCSI-II active terminator Desktop, laptop, notebook, and palmtop computers Intelligent instrumentation Printers Disk drives Voltage reference Ordering Information Pin Configuration Part Number Junction Temp. Range Package MIC5204BM –40°C to +125°C SO-8 MIC5204BS –40°C to +125°C SOT-223 VIN VIN VOUT VOUT NC GROUND NC ENABLE MIC5204BM Typical Application Both VIN and both VOUT pins must be tied together. ENABLE must be pulled high for operation. 110Ω TAB IS GROUND 110Ω 110Ω MIC5204 +5V + + 10µF 22µF 110Ω February 1999 SCSI Bus 18 to 27 Lines 59 1 2 3 IN GND OUT MIC5204-xxBS MIC5204 MIC5204 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Input Voltage (VIN) ........................................ –20V to +20V Enable Input Voltage (VEN) .......................... –0.3V to +20V Power Dissipation (PD) ................ Internally Limited, Note 3 Lead Temperature (soldering, 5 sec.) ....................... 260°C ESD Rating ............................................................. >2000V Input Voltage (VIN) ............................................ +3V to +6V Enable Input Voltage (VEN) ............................. –0.3V to VIN Junction Temperature Range (TJ) ........... –40°C to +125°C Electrical Characteristics VIN = VOUT + 1V; IL = 1mA; CL = 3.3µF; VEN ≥ 2.0V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted. Symbol Parameter VO Output Voltage Accuracy Conditions Min Typical Max Units 2.821 2.793 2.85 2.87 2.907 V ∆VO/∆T Output Voltage Temperature Coef. Note 4 20 100 ppm/°C ∆VO/VIN Line Regulation VIN = VOUT + 1V to 6V 0.004 0.10 0.40 % ∆VO/IL Load Regulation IL = 0.1mA to 100mA, Note 5 0.04 0.16 0.30 % VIN–VO Dropout Voltage, Note 6 IL = 100µA 30 75 190 240 210 350 450 750 mV IL = 50mA IL = 100mA IL = 500mA IQ Quiescent Current VENABLE ≤ 0.7V (Shutdown) 0.01 µA IGND Ground Pin Current VENABLE ≥ 2.0V, IL = 100µA IL = 20mA IL = 30mA IL = 50mA IL = 100mA 130 240 300 450 900 µA PSRR Ripple Rejection 70 dB IGNDDO Ground Pin Current at Dropout VIN = 0.5V less than designed VOUT IL = 100µA, Note 7 270 ILIMIT Current Limit VOUT = 0V 750 mA ∆VO/∆PD Thermal Regulation Note 8 0.05 %/W en Output Noise 30 µV 330 µA Enable Input VIL IIL IIH Input Voltage Level Logic Low Logic High Enable Input Current February 1999 off on 0.7 V 2.0 VIL ≤ 0.7V VIH ≥ 2.0V 0.01 15 60 µA 50 MIC5204 Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. 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: P(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. The θJC of the MIC5204BS is 15°C/W and θJA for the MIC5204BM is 160°C/W mounted on a PC board (see “Thermal Considerations” for details). Note 4. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 5. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from 0.1mA to 100mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. Note 6. 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 7. 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 8. 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 = 6V for t = 10ms. Output Voltage Variation vs. Junction Temperature 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -50 -25 0 25 50 75 100 125 JUNCTION TEMPERATURE (˚C) 6.0 GROUND CURRENT (mA) OUTPUT VOLTAGE VARIATION (%) Typical Characteristics Ground Current vs. Junction Temperature RL = 20Ω 5.5 VIN = 6V 5.0 4.5 4.0 3.5 3.0 -50 -25 0 25 50 75 100 125 JUNCTION TEMPERATURE (˚C) MIC5204 Micrel Applications Information Thermal Considerations Part I. Layout External Capacitors A 2.2µF capacitor is recommended between the MIC5204 output and ground to prevent oscillations due to instability. Larger values serve to improve the regulator's transient response. Most types of tantalum or aluminum electrolytics will be adequate; film types will work. Many aluminum electrolytics have electrolytes that freeze at about –30°C, so solid tantalums are recommended for operation below –25°C. The important parameters of the capacitor are an effective series resistance of about 5Ω or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. A 1µF capacitor should be placed from the MIC5204 input to ground 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. The MIC5204 will remain stable and in regulation with no load in addition to the internal voltage divider. The MIC5204BM (8-pin surface mount package) has the following thermal characteristics when mounted on a single layer copper-clad printed circuit board. θJA PC Board Dielectric FR4 Ceramic 160°C/W 120°C/W Multi-layer boards having a ground plane, wide traces near the pads, and large supply bus lines provide better thermal conductivity. The "worst case" value of 160°C/W assumes no ground plane, minimum trace widths, and a FR4 material board. Part II. Nominal Power Dissipation and Die Temperature The MIC5204BM at a 25°C ambient temperature will operate reliably at up to 625mW power dissipation when mounted in the "worst case" manner described above. At an ambient temperature of 55°C, the device may safely dissipate 440mW. These power levels are equivalent to a die temperature of 125°C, the recommended maximum temperature for nonmilitary grade silicon integrated circuits. In normal SCSI terminator applications, the average power dissipation is very small and this minimum geometry heat sink is suitable. The total dissipation does not approact the 400mW to 625mW range described above. For MIC5204BS (SOT-223 package) heat sink characteristics, please refer to Micrel Application Hint 17, “P.C. Board Heat Sinking”. As with the SO-8, average power dissipation in SCSI terminator applications is low and a minimum pad size is generally adequate. 50 mil 245 mil 150 mil 30 mil 50 mil Minimum recommended board pad size, SO-8. February 1999 62 MIC5204