MSK5976RH M. S Kennedy, MSK5976RH Datasheet - Page 4

• Manufacturer Part Number: MSK5976RH
• Description: Rad Hard Positive, 1.0 Amp, Single Resistor Adj Voltage Regulator
• Manufacturer: M. S Kennedy

IMPROVING INITIAL ACCURACY AND
REDUCING TEMPERATURE DRIFT
current tolerance and set point resistor accuracy can be reduced
to 0.2% using the MSK 109RH radiation hardened precision
reference. Minimal drift of the MSK 109RH from temperature
extremes and irradiation ensure very tight regulation. The circuit
can be configured to use the 2.5V reference to directly set the
output at 2.5V or with a slight variation it can provide any out-
put within the operating range of the MSK 5976RH down to 0V
output. Select Rs to maintain between 1mA and 10mA of cur-
rent through the reference; see Figure 4 below. Rs may be tied to
Vin or another power source. The optional trim resistor can be
used to further trim out initial output and system error. Reference
the MSK 109RH data sheet for application circuits that provide
stable output voltages across the full operating range of the MSK
5976RH including down to 0V output and the operating charac-
teristics of the MSK 109RH.
ADDING SHUTDOWN
Rset to 0 or connecting a transistor from the set pin to ground.
By connecting two transistors, as shown in Figure 5, a low
current voltage source is all that is required to take the set pin to
ground as well as pull the output voltage to ground. Q2 pulls the
output voltage to ground when no load is present and only needs
to sink 10mA. Use a low leakage switching diode between Vout
and Set to avoid overstress during shutdown transitions.
The initial output accuracy of the MSK 5976RH due to set pin
APPLICATION NOTES CONT'D
The MSK 5976RH can be easily shutdown by either reducing
APPLICATION NOTES CONT'D
FIGURE 4
FIGURE 5
4
HEAT SINKING
so, what type, refer to the thermal model and governing equation
below.
Governing Equation: Tj = Pd x (R jc + R cs + R sa) + Ta
WHERE
EXAMPLE:
This example demonstrates the thermal calculations for the TO-
257 package with the regulator operating at one-half of its maxi-
mum rated output current.
Conditions for MSK 5976RH:
Vin = +3.0V; Iout = +0.50A Vout=+1.0V
1.) Assume 45° heat spreading model.
2.) Find regulator power dissipation:
3.) For conservative design, set Tj = +125°C Max.
4.) For this example, worst case Ta = +90°C.
5.) R jc = 7.3°C/W from the Electrical Specification Table.
6.) R cs= 0.15°C/W for most thermal greases.
7.) Rearrange governing equation to solve for R sa:
thermal resistance of no more than 27.6°C/W must be used in
this application to maintain regulator circuit junction temperature
under 125°C.
TOTAL DOSE RADIATION TEST
PERFORMANCE
for all radiation testing performed by MS Kennedy. These curves
show performance trends throughout the TID test process and can
be located in the MSK 5976RH radiation test report. The complete
radiation test report will be available in the RAD HARD PROD-
UCTS section on the MSK website.
ADDITIONAL APPLICATION INFORMATION
Technology Corporation's® LT3080 and RH3080 data sheets.
In this case the result is 27.6°C/W. Therefore, a heat sink with a
R jc = Junction to Case Thermal Resistance
R cs = Case to Heat Sink Thermal Resistance
R sa = Heat Sink to Ambient Thermal Resistance
Tc = Case Temperature
Ta = Ambient Temperature
Tj = Junction Temperature
Pd = Total Power Dissipation
Ts = Heat Sink Temperature
To determine if a heat sink is required for your application and if
Radiation performance curves for TID testing will be generated
For additional applications information, please reference Linear
APPLICATION NOTES
Pd = (Vin - Vout)(Iout)
Pd = (3-1)(0.50)
R sa=
= 1.0W
=
=
((Tj - Ta)/Pd) - (R jc) - (R cs)
(125°C - 90°C)/1.0W - 7.3°C/W - 0.15°C/W
27.6°C/W
PRELIMINARY Rev. A 8/09