MSK5900RH MSK, MSK5900RH Datasheet - Page 3

• Manufacturer Part Number: MSK5900RH
• Description: RAD TOLERANT ULTRA LOW DROPOUT ADJUSTABLE POSITIVE LINEAR REGULATOR
• Manufacturer: MSK

PIN FUNCTIONS
VIN A,B,C - These pins provide power to all internal
including bias, start-up, thermal limit and overcurrent latch. In-
put voltage range is 2.9V to 7.5V. All three pins must be con-
nected for proper operation.
GND1 - Internally connected to input ground, these pins should
be connected externally by the user to the circuit ground and
the GND2 pins.
LATCH - The MSK 5900RH 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 approxi-
mately 1.6V from a 7.2µA (nominal) current source. Exceeding
the thermal limt charges the latch capacitor from a larger cur-
rent source for a near instant shutdown. Once the latch capaci-
tor 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 power both disable the device
during the reset operation (see SHUTDOWN pin description).
Pulling the LATCH pin low immediately 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 output volt-
age 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 ampli-
fier. The non-inverting input is connected to an internal 1.265V
reference. This error amplifier controls the drive to the output
transistor to force the FB pin to 1.265V. An external resistor
divider is connected to the output, FB pin and ground to set the
output voltage.
GND2 - Internally connected to output ground, these pins 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.
POWER SUPPLY BYPASSING
transients it is recommended that a 33µF
tantalum capacitor is connected between VIN and ground. A
0.1µF ceramic capacitor should also be used for high frequency
bypassing.
To maximize transient response and minimize power supply
APPLICATION NOTES
minimum
circuitry
3
OUTPUT CAPACITOR SELECTION
bility. A 220µF surface mount tantalum capacitor in parallel
with a 0.1µF ceramic capacitor from the output to ground should
suffice under most conditions. If the user finds that tighter
voltage regulation is needed during output transients, more
capacitance may be added. If more capacitance is added to the
output, the bandwidth may suffer. ESR of the output capaci-
tors should be maintained at 0.1
gain and phase margin. See the gain and phase curves.
OVERCURRENT LATCH-OFF/LATCH PIN
CAPACITOR SELECTION
rent/output short circuit protection with a timed latch-off cir-
cuit. Reference the LATCH pin description note. The latch off
time out is determined with an external capacitor connected
from the LATCH pin to ground. The time-out period is equal to
the time it takes to charge this external capacitor from 0V to
1.6V. The latch charging current is provided by an internal
current source. This current is a function of input voltage and
temperature (see latch charging current curve). For instance,
at 25°C, the latch charging current is 7.2µA at VIN=3V and
8µA at VIN=7V.
from the input. This additional latching current is also a func-
tion of input voltage and temperature (see latching current
curves).
THERMAL LIMITING
by the input and output voltages. Figure 1 illustrates the rela-
tionship between VIN and ICL for three output voltages.
Output capacitors are required to maintain regulation and sta-
In the latch-off mode, some additional current will be drawn
The MSK 5900RH current limit function is directly
As previously mentioned, the LATCH pin provides over cur-
FIGURE 1
to 1 to maintain adequate
Rev. H 11/06
affected