MSK5142-32 Datasheet, PDF (3/9 Pages) M.S. Kennedy Corporation – Fast Transient Response

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 MSK5142 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 MSK5142 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 MSK5142. To reduce ringing and improve transient re-
sponse, 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.
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.
FIGURE 2
OVERLOAD PROTECTION
The MSK5142 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.
3
8548-105 Rev. C 8/14