APPLICATION NOTES
PIN FUNCTIONS
VIN- This pin provides power to all internal circuitry in-
cluding bias, start-up, thermal limit and overcurrent latch.
Input voltage range is 2.9V to 6.5V.
GND - Internally connected to ground, this pin should be
connected externally by the user to the circuit ground.
SHUTDOWN - There are two functions to the SHUTDOWN
pin. It may be used to disable the output voltage or to
reset a current latch condition. To activate the shutdown/
reset functions the user must apply a voltage greater than
1.6V to the SHUTDOWN pin. The output voltage will turn
on when the SHUTDOWN pin is pulled below the thresh-
old voltage. If the SHUTDOWN pin is not used, it should
be connected to ground. It should be noted that with the
shutdown pin tied to ground, a current latch condition
can only be reset by cycling power off, then on.
VOUT - This is the output pin for the device.
INPUT POWER SUPPLY BYPASSING
3
FIGURE 1
Overcurrent protection is provided by the MSK 5820RH
series through the use of a timed latch off circuit. The
internal latch timeout is triggered by an overcurrent con-
dition. To allow for start up surge currents, the timeout is
approximately 5.5mS at 25°C. If the overcurrent condi-
tion remains at the end of the timeout cycle, the regulator
will latch off until the latch is reset. Reset the latch by
pulling the shutdown pin high or cycling VIN off then back
on. A thermal limit condition will trigger the latch with no
time out delay.
OVERCURRENT LATCH
To maximize transient response and minimize power sup-
ply transients it is recommended that two 47μF tantalum
capacitors are connected between VIN and ground. A
0.1μF ceramic capacitor should also be used for high fre-
quency bypassing. See typical application circuit.
CURRENT LIMIT AND SOA
The MSK 5820RH current limit function is directly af-
fected by the input and output voltages. Figure 1 illus-
trates the relationship between VIN and ICL for various
output voltages. It is very important for the user to con-
sult the SOA curve when using input voltages which re-
sult in current limit conditions beyond 4.5 Amps. When
using input voltages which result in current limit above
4.5 Amps, the user must maintain output current within
the SOA curve to avoid damage to the device. Note that 5
Amp maximum is due to current carrying capability of the
internal wirebonds.
REPLACING THE OMR9601/IRUH33P253AIM
When the MSK 5820-2.5RH is used as a replacement
for the IR OMR9601 or IRUH33P253B, the user should
recognize that the MSK 5820-2.5RH does not contain in-
ternal tantalum capacitors on the input and output.
The MSK 5820RH 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/
START UP CURRENT
OUTPUT CAPACITOR SELECTION
Low ESR output capacitors are required to maintain regu-
lation and stability. Four CWR29FB227 (AVX PN
TAZH227K010L) tantalum capacitors in parallel with ce-
ramic decoupling capacitors (0.1μF typical) provides suf-
ficient gain and phase margin for most applications. The
maximum ESR specification for the CWR29FB227 capaci-
tor is 180mΩ at 100kHz and is sufficient for many appli-
cations. MSK has found through full WCCA that screen-
ing for a maximum ESR of 57mΩ ensures EOL stability
criteria to be met for many applications with the most
stringent requirements. The typical ESR of the
TAZH227K010L from AVX is 49mΩ . Analysis of the fi-
nal design is recommended to ensure stability require-
ments are met. 8548-14 Rev. H 1/12