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MIC5204
Micrel
MIC5204
SCSI-II Active Terminator
Preliminary Information
General Description
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.
Features
* * * * * * * * * * 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
Part Number Junction Temp. Range Package MIC5204BM MIC5204BS -40C to +125C -40C to +125C SO-8 SOT-223
Pin Configuration
VOUT VOUT NC GROUND MIC5204BM VIN VIN NC ENABLE
Typical Application
110 110 110
Both VIN and both VOUT pins must be tied together. ENABLE must be pulled high for operation. TAB IS GROUND
+5V + 10F
MIC5204 + 22F
110
SCSI Bus 18 to 27 Lines
12 3 IN GND OUT MIC5204-xxBS
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MIC5204
MIC5204
Micrel
Absolute Maximum Ratings (Note 1)
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.) ....................... 260C ESD Rating ............................................................. >2000V
Operating Ratings (Note 2)
Input Voltage (VIN) ............................................ +3V to +6V Enable Input Voltage (VEN) ............................. -0.3V to VIN Junction Temperature Range (TJ) ........... -40C to +125C
Electrical Characteristics
VIN = VOUT + 1V; IL = 1mA; CL = 3.3F; VEN 2.0V; TJ = 25C, bold values indicate -40C TJ +125C; unless noted. Symbol VO VO/T VO/VIN VO/IL Parameter Output Voltage Accuracy Output Voltage Temperature Coef. Line Regulation Load Regulation Note 4 VIN = VOUT + 1V to 6V IL = 0.1mA to 100mA, Note 5 Conditions Min 2.821 2.793 Typical 2.85 20 0.004 0.04 Max 2.87 2.907 100 0.10 0.40 0.16 0.30 Units V ppm/C % %
VIN-VO
Dropout Voltage, Note 6
IL = 100A IL = 50mA IL = 100mA IL = 500mA
30 75 190 240 210 350 450 750 0.01 130 240 300 450 900 70
mV
IQ IGND
Quiescent Current Ground Pin Current
VENABLE 0.7V (Shutdown) VENABLE 2.0V, IL = 100A IL = 20mA IL = 30mA IL = 50mA IL = 100mA VIN = 0.5V less than designed VOUT IL = 100A, Note 7 VOUT = 0V Note 8
A A
PSRR IGNDDO ILIMIT VO/PD en Enable Input VIL IIL IIH
Ripple Rejection Ground Pin Current at Dropout Current Limit Thermal Regulation Output Noise
dB 330 A mA %/W V
270 750 0.05 30
Input Voltage Level Logic Low Logic High Enable Input Current
off on VIL 0.7V VIH 2.0V
0.7 2.0 0.01 15
V A
50
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MIC5204
Note 1. Note 2. Note 3.
Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: P(max) = (TJ(max) - TA) JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The JC of the MIC5204BS is 15C/W and JA for the MIC5204BM is 160C/W mounted on a PC board (see "Thermal Considerations" for details). Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. 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. 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. 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. 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.
Note 4. Note 5. Note 6. Note 7. Note 8.
Typical Characteristics
Output Voltage Variation vs. Junction Temperature Ground Current vs. Junction Temperature
OUTPUT VOLTAGE VARIATION (%)
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)
RL = 20 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
External Capacitors
A 2.2F 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 -30C, so solid tantalums are recommended for operation below -25C. The important parameters of the capacitor are an effective series resistance of about 5 or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. A 1F 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.
Thermal Considerations
Part I. Layout The MIC5204BM (8-pin surface mount package) has the following thermal characteristics when mounted on a single layer copper-clad printed circuit board.
PC Board Dielectric FR4 Ceramic JA 160C/W 120C/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 160C/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 25C 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 55C, the device may safely dissipate 440mW. These power levels are equivalent to a die temperature of 125C, 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.
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MIC5204

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