MIL-PRF-38534 AND 38535 CERTIFIED FACILITY
M.S.KENNEDY CORP.
4707 Dey Road Liverpool, N.Y. 13088
3A LOW NOISE,
FIXED OUTPUT LDO
REGULATOR
5142
SERIES
(315) 701-6751
FEATURES:
Fast Transient Response
Low Dropout Voltage: 340mV @ 3A
Low Noise: 40uVrms (10Hz to 100KHz)
1mA Quiescent Current
Fixed Output Voltages: 1.5V, 1.7V, 1.8V, 1.9V, 2.0V, 2.5V, 3.3V
No Protection Diodes Required
Stable with 10uF Output Capacitor
Available with Top Tab or Tabless Package
Available in Four Lead Configurations
Contact MSK for MIL-PRF-38534 Qualification Status
NO TAB
TOP TAB
DESCRIPTION:
The MSK 5142 series regulators offer a low 340mV dropout voltage while supplying to 3A of output current. With fast
transient response, these regulators have very low output noise. Excellent line and load regulation characteristics ensure
accurate performance for multiple applications with a low operating quiescent current of 1mA. These regulators offer
internal short circuit current limit, thermal limiting and reverse current protection which eliminates the need for external
components and excessive derating. The MSK 5142 series regulators are available in a hermetically sealed space efficient
TO-257 package with multiple lead form options.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
Post Regulator For Switching Power Supplies
Battery Powered Equipment
Microprocessor Power Supplies
Pre-amplifier Power Supplies
PIN-OUT INFORMATION
1 GND
2 VOUT
3 VIN
1
8548-105 Rev. B 5/13
ABSOLUTE MAXIMUM RATINGS
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7
ELECTRICAL SPECIFICATIONS
NOTES:
1 The output is decoupled to ground using a 100μF low ESR tantalum capacitor in parallel with a 1μF ceramic capacitor. See figure 1 for
typical circuit.
2 Guaranteed by design but not tested. Typical parameters are representative of actual device performance but are for reference only.
3 Industrial grade devices shall be tested to subgroups 1 unless otherwise requested.
4 Military grade devices ("H" suffix) shall be 100% tested to subgroups 1,2 and 3.
TA=+25°C
5 Subgroup 1
Subgroup 2
TA=+125°C
Subgroup 3
TA=-55°C
6 Not applicable to versions where VIN + V
DROPOUT
< VIN min. The minimum input voltage requirement must be maintained.
7 Reference current limit typical performance curves for input to output differential limitations.
8 Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle.
2
8548-105 Rev. B 5/13
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J
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IN
I
OUT
VIN
T
C
Supply Voltage
20V
Output Current
3A
Differential Input Voltage
20V
Case Operating Temperature range
MSK 5142H
-55°C to +125°C
MSK 5142
-40°C to +85°C
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T
ST
T
LD
Storage Temperature Range
Lead Temperature Range
(10 Seconds)
Junction Temperature
-65°C to +150°C
300°C
+150°C
APPLICATION NOTES
INPUT BYPASS CAPACITORS
Unless the regulator is located very close to the main input
filter capacitor, a 1μF to 10μF low ESR tantalum capacitor
should be added to the regulator's input to maximize tran-
sient response and minimize power supply transients. A
0.1μF ceramic capacitor should also be used for high fre-
quency bypassing.
LOAD REGULATION
In voltage regulator applications where very large load cur-
rents are present, the load connection is very important.
The path connecting the output of the regulator to the load
must be extremely low impedance to avoid affecting the
load regulation specifications. As shown in figure 2, any
impedance (Rs) in this path will form a voltage divider with
the load. For best results the ground pin should be connected
directly to the load as shown in figure 2. The direct connec-
tion eliminates the effect the potential voltage drop in the
power ground path can have on the internal ground sensing,
thus improving load regulation. The MSK 5142 ground pin
trace must be designed to carry the ground pin current with-
out significant voltage drops. See typical performance curves.
FIGURE 1
OUTPUT CAPACITOR SELECTION
For most applications a 10μF low ESR tantalum capacitor,
as close to the regulators output as possible, is all that is
required for the MSK 5142 to be stable. When using a 10μF
capacitor on the lower output voltage devices, a minimum
ESR is required of the capacitor. This requirement decreases
from 20mΩ on the 1.5V output regulator to 5mΩ on the
3.3V output regulator. With an increase in capacitance, the
minimum ESR requirement decreases. At 100μF, the mini-
mum ESR requirement decreases to 5mΩ for all versions of
the MSK 5142. To reduce ringing and improve transient
response, capacitors with slightly larger ESR in the range
of 20mΩ to 50mΩ provides improved damping. Capacitors
with higher ESR can be combined in parallel with low ESR
ceramic capacitors for good high frequency response and
settling time. The maximum ESR value must be less than
3Ω. Care must be taken when selecting a ceramic type.
The X5R and X7R are the best choice for output stability
when considering response due to applied voltage and tem-
perature.
FIGURE 2
OVERLOAD PROTECTION
The MSK 5142 series regulators feature both current limit
and thermal overload protection. Within the safe operating
region, the regulators will current limit above their 1.6amp
rating. As the input to output voltage increases, however,
the current limit decreases to keep the output transistor
within its power dissipation limitation. See the Current Limit
Typical Curves for conditional performance detail. If the de-
vice heats enough to exceed its rated die junction tempera-
ture due to excessive ambient temperature, improper heat
sinking etc., the regulators also shutdown until an appropri-
ate junction temperature is maintained. To bring the regula-
tor out of shutdown, the device input may need to be cycled
to zero and power reapplied to eliminate the shutdown con-
dition.
REVERSE VOLTAGE PROTECTION
The regulators are protected against reverse input and out-
put voltages. Reverse input voltages up to 20V will be
blocked from the input while current flow is limited to less
than 1mA. The reverse voltage on the input is also pre-
vented from appearing on the output and the load. When
the input voltage is pulled down to ground and the output is
held up by a second source, the current flow between them
is limited to typically 600μA. See the electrical specifica-
tions table.
3
8548-105 Rev. B 5/13
APPLICATION NOTES CONT'D
MINIMIZING POWER DISSIPATION:
To maximize the performance and reduce power dissipation
of the MSK 5142 series devices, VIN should be maintained
as close to dropout or at VIN minimum when possible. See
Input Supply Voltage requirements. A series resistor can be
used to lower VIN close to the dropout specification, lower-
ing the input to output voltage differential. In turn, this will
decrease the power that the device is required to dissipate.
Knowing peak current requirements and worst case volt-
ages, a resistor can be selected that will drop a portion of
the excess voltage and help to distribute the heating. The
circuit below illustrates this method.
HEAT SINK SELECTION
To select a heat sink for the MSK 5142, the following for-
mula for convective heat flow may be used.
Governing Equation:
T
J
=
P
D
X (R
θJC
+ R
θCS
+ R
θSA
) + T
A
Where
T
J
P
D
R
θJC
R
θCS
R
θSA
T
A
=
=
=
=
=
=
Junction Temperature
Total Power Dissipation
Junction to Case Thermal Resistance
Case to Heat Sink Thermal Resistance
Heat Sink to Ambient Thermal Resistance
Ambient Temperature
Power Dissipation=(VIN-VOUT) x I
OUT
Next, the user must select a maximum junction tempera-
ture. The absolute maximum allowable junction temperature
is 150°C. The equation may now be rearranged to solve for
the required heat sink to ambient thermal resistance (R
θSA
).
The maximum resistor value can be calculated from the
following:
R1 max = VIN min - (VOUT max + V
DROP
)
I
OUT
peak + GND Pin Current
Where:
VIN min=Minimum input voltage
VOUT max=Maximum output voltage across the full
temperature range
V
DROP
=Worst case dropout voltage (Typically 430mV)
I
OUT
peak=Maximum load current
GND Pin Current=Max. GND Pin Current at I
OUT
peak
Example:
An MSK 5142 is connected for VIN=+5V and
VOUT=+3.3V. I
OUT i
s a continuous 2A DC level. The am-
bient temperature is +25°C. The maximum desired junc-
tion temperature is +125°C.
R
θJC
=5.6°C/W and R
θCS
=0.15°C/W for most thermal
greases
Power Dissipation=(5V-3.3V) x (2A)
=3.4 Watts
Solve for R
θSA:
R
θSA
= 125°C - 25°C - 3.8°C/W - 0.15°C/W
3.4W
= 25.5°C/W
In this example, a heat sink with a thermal resistance of no
more than 25.5°C/W must be used to maintain a maximum
junction temperature of no more than 125°C.
4
8548-105 Rev. B 5/13
TYPICAL PERFORMANCE CURVES
5
8548-105 Rev. B 5/13
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