Total Dose Tested to TBDK RAD (Method 1019.7 Condition A)
Ultra Low Dropout for Reduced Power Consumption
External Shutdown/Reset Function
Latching Overload Protection
Adjustable Output Using Two External Resistors
Three Versions for Highest Performance at Particular VIN to VOUT Levels.
Custom Versions Available
Output Current Limit
Low Input Voltage for Maximum Efficiency
Up to 10A Output Current
Contact MSK for MIL-PRF-38534 Qualification and Appendix G (Radiation) Status
DESCRIPTION:
The MSK 5951RH is a radiation hardened adjustable linear regulator capable of delivering up to 10A of current.
The device is available in three different options that provide different output current and dropout voltage character-
istics at various input and output voltages. Dropout of less than 0.75V at 8A in some configurations and typically less
than 0.21V at 2A for all three options is available. An external shutdown/reset function is ideal for power supply
sequencing. The MSK 5951RH also offers overload protection that requires no external current sense resistor.
These devices are radiation hardened and were designed with many space/satellite applications in mind. The MSK
5951RH is packaged in a hermetically sealed, space efficient 12 pin power dual inline package that has high thermal
conductivity for efficient device cooling.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
TYPICAL APPLICATIONS
Satellite System Power Supplies
Switching Power Supply Post Regulators
Constant Voltage/Current Regulators
Microprocessor Power Supplies
1
2
3
4
5
6
1
PIN-OUT INFORMATION
VINA
VINB
VINC
VBIAS
GND1
SHUTDOWN
12
11
10
9
8
7
VOUTC
VOUTB
VOUTA
FB
GND2
LATCH
PRELIMINARY Rev. B 1/10
ABSOLUTE MAXIMUM RATINGS
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8
ELECTRICAL SPECIFICATIONS
NOTES:
1
Unless otherwise specified:
-1 version, VOUT=1.5V, VIN=2.5V, VBIAS=5.0V V
SHUTDOWN
=0V. I
OUT
is subtracted from I
Q
measurement. See typical applications circuit.
-2 version, VOUT=2.5V, VIN=3.3V, VBIAS=5.0V V
SHUTDOWN
=0V. I
OUT
is subtracted from I
Q
measurement. See typical applications circuit.
-3 version, VOUT=3.3V, VIN=VBIAS=5.0V V
SHUTDOWN
=0V. I
OUT
is subtracted from I
Q
measurement. See typical applications circuit.
Guaranteed by design but not tested. Typical parameters are representative of actual device performance but are for reference only.
Industrial grade and "E" suffix devices shall be tested to subgroups 1 and 4 unless otherwise requested.
Military grade devices ("H" suffix) shall be 100% tested to subgroups 1,2,3 and 4.
Subgroup 5 and 6 testing available upon request.
Subgroup 1,4 TC=+25°C
Subgroup 2,5 TC=+125°C
Subgroup 3,6 TA=-55°C
Output current limit is tested with a low duty cycle pulse to minimize junction heating and is dependent on the values of VIN, VOUT and case temperature. See
Typical Performance Curves.
Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle.
Pre and post irradiation limits, up to 300Krad TID, are identical unless otherwise specified.
2
3
4
5
6
7
8
9
2
PRELIMINARY Rev. B 1/10
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P
D
T
C
See SOA Curve
150°C
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+VBIAS
+VIN
I
OUT
T
C
Bias Supply Voltage
10.0V
Supply Voltage
10.0V
Output Current
7
10A
Case Operating Temperature Range
MSK5951K/H/E RH
-55°C to +125°C
MSK5951RH
-40°C to +85°C
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T
ST
T
LD
Storage Temperature Range
Lead Temperature Range
(10 Seconds)
Power Dissipation
Junction Temperature
-65°C to +150°C
300°C
APPLICATION NOTES
PIN FUNCTIONS
VIN A,B,C -
These pins provide the input power connection to the
MSK 5951RH. This is the supply that will be regulated to the
output. All three pins must be connected for proper operation.
VBIAS -
This pin provides power to all internal circuitry including
bias, start-up, thermal limit and overcurrent latch. VBIAS voltage
range is 2.9V to 7.5V. VBIAS should be kept greater than or equal
to VIN.
GND1 -
Internally connected to input ground, this pin should be
connected externally by the user to the circuit ground and the
GND2 pins.
LATCH -
The MSK 5951RH LATCH pin is used for both current
limit and thermal limit. A capacitor between the LATCH pin and
ground sets a time out delay in the event of an over current or
short circuit condition. The capacitor is charged to approximately
1.6V from a 7.2µA (nominal) current source. Exceeding the ther-
mal limit will charge the latch capacitor from a larger current source
for a near instant shutdown. Once the latch capacitor is charged
the device latches off until the latch is reset. Momentarily pull the
LATCH pin low, toggle the shutdown pin high then low or cycle
the power to reset the latch. Toggling the shutdown pin or cycling
the bias power both disable the device during the reset operation
(see SHUTDOWN pin description). Pulling the LATCH pin low im-
mediately enables the device for as long as the LATCH pin is held
low plus the time delay to re-charge the latch capacitor whether or
not the fault has been corrected. Disable the latch feature by tying
the LATCH pin low. With the LATCH pin held low the thermal limit
feature is disabled and the current limit feature will force the out-
put voltage to droop but remain active if excessive current is drawn.
SHUTDOWN -
There are two functions to the SHUTDOWN pin. It
may be used to disable the output voltage or to reset the LATCH
pin. To activate the shutdown/reset functions the user must apply
a voltage greater than 1.3V to the SHUTDOWN pin. The output
voltage will turn on when the SHUTDOWN pin is pulled below the
threshold voltage. If the SHUTDOWN pin is not used, it should be
connected to ground.
FB -
The FB pin is the inverting input of the internal error amplifier.
The non-inverting input is connected to an internal 1.265V refer-
ence. This error amplifier controls the drive to the output transistor
to force the FB pin to 1.265V. An external resistor divider is con-
nected to the output, FB pin and ground to set the output voltage.
GND2 -
Internally connected to output ground, this pin should be
connected externally by the user to the circuit ground and the
GND1 pins.
VOUT A,B,C -
These are the output pins for the device. All three
pins must be connected for proper operation.
The MSK 5951RH starts up and begins regulating immediately
when VBIAS and VIN are applied simultaneously. Applying VBIAS
before VIN starts the MSK 5951RH up in a disabled or latched
state. When starting in a latched state the device output can be
enabled either by pulling the latch pin low to drain the latch ca-
pacitor or pulsing the shutdown pin high. The shutdown pulse
duration is partially dependent upon the size of the latch capacitor
and should be characterized for each application; 30uS is typically
adequate for a 1uF latch capacitor at 25°C. A momentary high
pulse on the shutdown pin can be achieved using the RC circuit
below if VIN rises rapidly. The resistor and capacitor must be
selected based on the required pulse duration, the rise character-
istic of VIN and the shutdown pin threshold (see shutdown pin
threshold and current curves).
START UP OPTIONS
The shutdown pin can be held high and pulled low after VIN comes
up or the latch pin held low and released after VIN comes up to
ensure automatic startup when applying VBIAS before VIN. Ei-
ther of the basic circuits below can be adapted to a variety of
applications for automatic start up when VBIAS rises before VIN.
As previously mentioned, the LATCH pin provides over cur-
rent/output short circuit protection with a timed latch-off circuit.
Reference the LATCH pin description note. The latch off time
OUTPUT CAPACITOR SELECTION
out is determined with an external capacitor connected from the
Typically, large bulk capacitance is required at the output of a
LATCH pin to ground. The time-out period is equal to the time it
linear regulator to maintain good load transient response. How-
takes to charge this external capacitor from 0V to 1.6V. The
ever, with the MSK 5951RH this is not the case. A 100µF surface
latch charging current is provided by an internal current source.
mount tantalum capacitor in parallel with a 0.1µF ceramic capaci-
This current is a function of bias voltage and temperature (see
tor from the output to ground should suffice under most condi-
latch charging current curve). In the latch-off mode, some addi-
tions. If the user finds that tighter voltage regulation is needed
tional current will be drawn from the bias supply. This additional
during output transients, more capacitance may be added. If more
latching current is also a function of bias voltage and tempera-
capacitance is added to the output, the bandwidth may suffer.
ture (see typical performance curves). The MSK 5951RH current
See typical gain and phase curves.
limit function is directly affected by the input and output volt-
POWER SUPPLY BYPASSING
ages. At elevated temperatures or input voltages the device may
To maximize transient response and minimize power supply tran- simply limit the output current without activating the latch fea-
sients it is recommended that a 100µF minimum tantalum capaci- ture. A thermal limit condition will trigger the latch with no time
tor is connected between VIN and ground. A 0.1µF ceramic ca- out delay. Custom current limit is available; contact the factory
pacitor should also be used for high frequency bypassing.
for more information.
PRELIMINARY Rev. B 1/10
3
OVERCURRENT LATCH-OFF/LATCH PIN CAPACITOR
SELECTION
APPLICATION NOTES CONT'D
THERMAL LIMITING
The MSK 5951RH control circuitry has a thermal shut-
down temperature of approximately 150°C. This ther-
mal shutdown can be used as a protection feature, but
for continuous operation, the junction temperature of the
pass transistor must be maintained below 150°C. Proper
heat sink selection is essential to maintain these condi-
tions. Exceeding the thermal limit activates the latch fea-
ture of the MSK 5951RH. See LATCH pin description for
instructions to reset the latch or disable the latch fea-
ture.
TYPICAL APPLICATIONS CIRCUIT
HEAT SINK SELECTION
To select a heat sink for the MSK 5951RH, the follow-
ing formula 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
V
OUT
=1.265(1+R1/R2)
OUTPUT VOLTAGE SELECTION
As noted in the above typical applications circuit,
the formula for output voltage selection is
V
OUT
=1.265 1+ R1
R2
A good starting point for this output voltage selection is
to set R2=1K. By rearranging the formula it is simple to
calculate the final R1 value.
R1=R2
V
OUT
-1
1.265
Power Dissipation=(V
IN
-V
OUT
) x I
OUT
Next, the user must select a maximum junction tem-
perature. The absolute maximum allowable junction tem-
perature is 150°C. The equation may now be rearranged
to solve for the required heat sink to ambient thermal
resistance (R
θSA
).
Table 1 below lists some of the most probable resistor
combinations based on industry standard usage.
TABLE 1
OUTPUT VOLTAGE
(V)
1.5
1.8
2.0
2.5
2.8
3.3
4.0
5.0
R2
(Ω)
Ω
1K
1K
1K
1K
1K
1K
1K
1K
R1 (nearest 1%)
(Ω)
Ω
187
422
576
976
1.21K
1.62K
2.15K
2.94K
Example:
An MSK 5951RH is connected for V
IN
=+5V and
V
OUT
=+3.3V. I
OUT
is a continuous 4A DC level. The
ambient temperature is +25°C. The maximum desired
junction temperature is +125°C.
R
θJC
=2.1°C/W and R
θCS
=0.15°C/W for most thermal
greases
Power Dissipation=(5V-3.3V) x (4A)
=6.8 Watts
Solve for R
θSA:
125°C - 25°C
6.8W
START UP CURRENT
The MSK 5951RH sinks increased current during startup
to bring up the output voltage. Reference the "Saturated
Drive Current vs. Input Voltage graph in the typical per-
formance curves of this data sheet and the "Understand-
ing Startup Surge Current With MS Kennedy's RH1573
Based Rad Hard LDO Regulators" application note in the
application notes section of the MS Kennedy Web site
for more information.
http://www.mskennedy.com/
4
PRELIMINARY Rev. B 1/10
R
θSA
=
= 12.5°C/W
-2.1°C/W - 0.15°C/W
In this example, a heat sink with a thermal resistance
of no more than 12.5°C/W must be used to maintain a
junction temperature of no more than 125°C.
APPLICATION NOTES CONT.
CONT'D
LOW OUTPUT VOLTAGE APPLICATION
The MSK 5951RH can be configured for output voltage levels
below the internal 1.265V reference. For output levels below
the feedback voltage an external reference such as the MSK
109RH shown in Figure 1 is used in the feedback network.
Configure the feedback divider between VOUT and the external
reference. When using the MSK 109RH external reference as
shown in Figure 1 the output voltage is calculated as follows.
Given
V
FB
=1.265V
V
REF
=2.5V
VOUT=V
FB
-R1*(V
REF
-V
FB
)/R2
R
REF
must be selected to supply the proper current to the MSK
109RH and the current through R2 under all operating condi-
tions. The MSK 109RH requires a minimum of 0.5mA and a
maximum of 10mA for regulation. The current in R2 is equal to
(V
REF
-V
FB
)/R2.
R
REF
=(VBIAS-V
REF
)/(I
R2
+I
REF
)
Given
I
REF
=The current in the MSK 109RH (typically 1 to 5mA)
TOTAL DOSE RADIATION TEST
PERFORMANCE
Radiation performance curves for TID testing have been gen-
erated for all radiation testing performed by MS Kennedy. These
curves show performance trends throughout the TID test pro-
cess and will be located in the MSK 5951RH radiation test
report after TID testing has been performed. The complete ra-
diation test report will be available in the RAD HARD PROD-
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