MIL-PRF-38534 AND 38535 CERTIFIED FACILITY
M.S.KENNEDY CORP.
1.5A, NEGATIVE
ADJUSTABLE
LINEAR REGULATOR
5173
4707 Dey Road Liverpool, N.Y. 13088
(315) 701-6751
SMD-1
3 PAD
CERAMIC
FEATURES:
Output Current Limit
Internal Thermal Overload Protection
Output Current to 1.5 Amps
Adjustable Output using two External Resistors
Available in 3 Lead Form Options: Straight, Up and Down (TO-257)
Electrically Isolated Package (TO-257)
Equivalent Rad Hard Device MSK 5973RH
Contact MSK for MIL-PRF-38534 Qualification Status
TO-257
DESCRIPTION:
The MSK 5173 is a 3-terminal negative adjustable regulator capable of supplying up to 1.5A of current. The output is
adjustable using external resistors for a range of Vref to -27V. Excellent line and load regulation characteristics ensure
accurate performance. The MSK 5173 has full protection with current and thermal limiting. The MSK 5173 is packaged in
two space saving packages, the 3 pin power surface mount ceramic SMD-1 or the TO-257 package with 3 lead form
options: straight, up and down.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
PIN-OUT INFORMATION
System Power Supplies
Switching Power Supply Post Regulators
Constant Voltage/Current Regulators
High Efficiency Linear Regulators
TO-257
SMD-1
1 ADJ
2 VIN
3 VOUT
1 ADJ
2 VOUT
3 VIN
PACKAGE=ISOLATED
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8548-85 Rev. C 10/12
ABSOLUTE MAXIMUM RATINGS
VIN
PD
IOUT
TJ
Input Voltage (VIN-VOUT)
Power Dissipation
Output Current
Junction Temperature
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TST Storage Temperature Range
TLD Lead Temperature Range
(10 Seconds)
TC Case Operating Temperature
MSK 5173
MSK 5173H
30VDC
Internally Limited
1.5A
+150°C
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-65°C to +150°C
300°C
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-55°C to +125°C
-55°C to +125°C
ELECTRICAL SPECIFICATIONS
NOTES:
1 Output is decoupled to ground using 10μF low ESR tantalum capacitors and 0.1μF ceramic.
2 Guaranteed by design but not tested. Typical parameters are representative of actual device
performance but are for reference only.
3 All output parameters are tested using a low duty cycle pulse to maintain TJ = TC.
4 Industrial grade and devices shall be tested to subgroup 1 unless otherwise specified.
5 Military grade devices ("H" suffix) shall be 100% tested to subgroups 1,2 and 3.
6 Subgroup 1
TA=TC=+25°C
Subgroup 2
TA=TC=+125°C
Subgroup 3
TA=TC=-55°C
7 The output current limit function provides protection from transient overloads but it may exceed the maximum continuous rating.
Continuous operation in current limit may damage the device.
8 Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle.
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8548-85 Rev. C 10/12
APPLICATION NOTES
OUTPUT VOLTAGE
LOAD REGULATION
The MSK 5173 develops a nominal -1.25V reference voltage
between the output and adjustment terminal. With a constant
reference voltage drop across program resistor R1, a constant
current flows through the output set resistor R2. Since the current from the adjustment terminal represents an error in the programmed output voltage, the MSK 5173 was designed to minimize IADJ and make it very constant with line and load changes.
To do this, all quiescent operating current is returned to the
output establishing a minimum load current requirement. If there
is insufficient load on the output, the output will rise. Figure 1
shows the output voltage calculations.
The MSK 5173 is capable of providing extremely good load
regulation but a few precautions are needed to obtain maximum
performance. The current set resistor connected between the
adjustment terminal and the output terminal should be tied directly to the output pin as close to the case of the regulator as
possible rather than near the load. This eliminates package pin
and trace drops from appearing effectively in series with the
reference and degrading regulation. For example, if the regulator
is set to -5V with 0.05Ω resistance between the regulator and
the current set resistor, the output will droop 225mV at 1A due
to package pin and trace resistance. The amount of droop can be
calculated as follows: (Vout at 5mA) - (1.250(0.05Ω*IL))*(1+R2/R1). The ground of R2 can be returned
near the ground of the load to provide remote ground sensing
and improve load regulation. Figure 2A shows the effect of resistance between the regulator and 240Ω set resistor.
FIGURE 1
INPUT VOLTAGE
FIGURE 2A
(Degraded Regulation)
The minimum required input voltage for proper operation is
Vout+ Dropout voltage. See typical performance curves for
dropout performance.
EXTERNAL CAPACITORS
Input bypassing with a 1uF tantalum in parallel with a 0.1uF
ceramic on the input is suitable in most applications. To maximize transient response and minimize input supply transients
more input capacitance can be added. The adjustment terminal
can be bypassed to ground on the MSK 5173 to improve ripple
rejection. This bypass capacitor prevents ripple from being amplified at higher output voltages. The impedance of the adjust
pin capacitor at the ripple frequency should be less than the
value of R1. For most application a 10μF bypass capacitor will
provide sufficient ripple rejection at any output level. Increases
over 10μF do not appreciably improve the ripple rejection at
frequencies above 120Hz. Output bypassing with 10μF low
ESR tantalum in parallel with a 0.1μF ceramic attached as close
to the regulator's output as possible is best. This will effectively
lower the regulator output impedance, increase transient response
and eliminate any oscillations. Any increase of the load capacitance larger than 10μF will merely improve the loop stability and
output impedance. See Figure 3 for typical application schematic.
FIGURE 2B
(Best Case Regulation)
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8548-85 Rev. C 10/12
APPLICATION NOTES CONT'D
HEAT SINKING
PROTECTION DIODES
When external capacitors are used with any IC regulator it is
sometimes necessary to add protection diodes to prevent the
capacitors from discharging through low current points into the
regulator. Most 10μF capacitors have low enough internal series resistance to deliver 20A spikes when shorted. Although
the surge is short, there is enough energy to stress MSK 5173.
When an output capacitor is connected to a regulator and the
input is shorted or crowbarred, the output capacitor will discharge into the output of the regulator. The discharge current
depends on the value of the capacitor, the output voltage of the
regulator, and the rate of decrease of VIN. Figure 3 shows an
MSK 5173 with protection diodes included. D2 is only required
if the adjust pin has external capacitance tied to it .
To determine if a heat sink is required for your application
and if so, what type, refer to the thermal model and governing equation below.
Governing Equation: Tj = Pd x (Rθjc + Rθcs + Rθsa) + Ta
WHERE
Tj = Junction Temperature
Pd = Total Power Dissipation
Rθjc= Junction to Case Thermal Resistance
Rθcs= Case to Heat Sink Thermal Resistance
Rθsa = Heat Sink to Ambient Thermal Resistance
Tc = Case Temperature
Ta = Ambient Temperature
Ts = Heat Sink Temperature
EXAMPLE:
This example demonstrates an analysis with the output set
to -10V, where the output current is at 0.5 amp and the
input is -15V.
Conditions for MSK 5173:
Vin = -15V; Iout = 0.5A
1.) Assume 45° heat spreading model.
2.) Find regulator power dissipation:
Pd = (Vin - Vout)(Iout)
Pd = (15V-10V)(0.5A)
Pd = 2.5W
FIGURE 3
3.) For conservative design, set Tj = +125°C Max.
4.) For this example, worst case Ta= +90°C.
5.) Rθjc = 6.7°C/W from the Electrical Specification Table.
6.) Rθcs= 0.15°C/W for most thermal greases.
7.) Rearrange governing equation to solve for Rθsa:
Rθsa=((Tj - Ta)/Pd) - (Rθjc) - (Rθcs)
= (125°C-90°C)/2.5W - 6.7°C/W - 0.15°C/
= 7.2°C/W
In this case the result is 7.2°C/W. Therefore, a heat sink
with a thermal resistance of no more than 7.2°C/W must be
used in this application to maintain regulator circuit junction
temperature under 125°C.
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8548-85 Rev. C 10/12
TYPICAL PERFORMANCE CURVES
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8548-85 Rev. C 10/12
MECHANICAL SPECIFICATIONS
ESD TRIANGLE INDICATES PIN 1
WEIGHT=3.2 GRAMS TYPICAL
ORDERING INFORMATION
MSK5173 H U
LEAD CONFIGURATIONS
S= STRAIGHT; U= BENT UP; D= BENT DOWN
SCREENING
BLANK= INDUSTRIAL; H=MIL-PRF-38534 CLASS H;
GENERAL PART NUMBER
The above example is a Class H regulator with leads bent up.
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8548-85 Rev. C 10/12
MECHANICAL SPECIFICATIONS
WEIGHT=2.2 GRAMS TYPICAL
ORDERING INFORMATION
MSK5173 H L
3 PAD CERAMIC SMD-1 PACKAGE
SCREENING
BLANK= INDUSTRIAL; H=MIL-PRF-38534 CLASS H;
GENERAL PART NUMBER
The above example is a Class H regulator in the 3 Pad Ceramic Package.
M.S. Kennedy Corp.
4707 Dey Road, Liverpool, New York 13088
Phone (315) 701-6751
FAX (315) 701-6752
www.mskennedy.com
The information contained herein is believed to be accurate at the time of printing. MSK reserves the right to make
changes to its products or specifications without notice, however, and assumes no liability for the use of its products.
Please visit our website for the most recent revision of this datasheet.
Contact MSK for MIL-PRF-38534 qualification status.
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8548-85 Rev. C 10/12