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 protec-
tion against reversed battery, current limiting, and over-
temperature 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
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
–40°C to +125°C
–40°C to +125°C
SO-8
SOT-223
Pin Configuration
VOUT
VOUT
NC
GROUND
MIC5204BM
VIN
VIN
NC
ENABLE
Typical Application
110Ω
110Ω
110Ω
Both V
IN
and both V
OUT
pins must be tied
together. ENABLE must be pulled high for
operation.
TAB IS GROUND
+5V
+
10µF
MIC5204
+
22µF
110Ω
SCSI Bus
18 to 27
Lines
1 2
3
IN GND OUT
MIC5204-xxBS
February 1999
59
MIC5204
MIC5204
Micrel
Absolute Maximum Ratings
(Note 1)
Input Voltage (V
IN
) ........................................ –20V to +20V
Enable Input Voltage (V
EN
) .......................... –0.3V to +20V
Power Dissipation (P
D
) ................ Internally Limited,
Note 3
Lead Temperature (soldering, 5 sec.) ....................... 260°C
ESD Rating ............................................................. >2000V
Operating Ratings
(Note 2)
Input Voltage (V
IN
) ............................................ +3V to +6V
Enable Input Voltage (V
EN
) ............................. –0.3V to V
IN
Junction Temperature Range (T
J
) ........... –40°C to +125°C
Electrical Characteristics
V
IN
= V
OUT
+ 1V; I
L
= 1mA; C
L
= 3.3µF; V
EN
≥
2.0V; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤
+125°C; unless noted.
Symbol
V
O
∆V
O
/∆T
∆V
O
/V
IN
∆V
O
/I
L
Parameter
Output Voltage Accuracy
Output Voltage
Temperature Coef.
Line Regulation
Load Regulation
Note 4
V
IN
= V
OUT
+ 1V to 6V
I
L
= 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
%
%
V
IN
–V
O
Dropout Voltage,
Note 6
I
L
= 100µA
I
L
= 50mA
I
L
= 100mA
I
L
= 500mA
30
75
190
240
210
350
450
750
0.01
130
240
300
450
900
70
mV
I
Q
I
GND
Quiescent Current
Ground Pin Current
V
ENABLE
≤
0.7V (Shutdown)
V
ENABLE
≥
2.0V, I
L
= 100µA
I
L
= 20mA
I
L
= 30mA
I
L
= 50mA
I
L
= 100mA
V
IN
= 0.5V less than designed V
OUT
I
L
= 100µA,
Note 7
V
OUT
= 0V
Note 8
µA
µA
PSRR
I
GNDDO
I
LIMIT
∆V
O
/∆P
D
e
n
Enable Input
V
IL
I
IL
I
IH
Ripple Rejection
Ground Pin
Current at Dropout
Current Limit
Thermal Regulation
Output Noise
dB
330
µA
mA
%/W
µV
270
750
0.05
30
Input Voltage Level
Logic Low
Logic High
Enable Input Current
off
on
V
IL
≤
0.7V
V
IH
≥
2.0V
0.7
2.0
0.01
15
V
µA
50
February 1999
60
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, T
J(max)
, the junction-to-ambient thermal
resistance,
θ
JA
, and the ambient temperature, T
A
. The maximum allowable power dissipation at any ambient temperature is calculated using:
P
(max)
= (T
J(max)
– T
A
)
θ
JA
. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will
go into thermal shutdown. The
θ
JC
of the MIC5204BS is 15°C/W and
θ
JA
for the MIC5204BM is 160°C/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 V
IN
= 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)
R
L
= 20Ω
5.5 V
IN
= 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 2.2µF capacitor is recommended between the MIC5204
output and ground to prevent oscillations due to instability.
Larger values serve to improve the regulator's transient re-
sponse. 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.
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
θ
JA
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 non-
military 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 characteris-
tics, 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
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MIC5204
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