LM9071T/NOPB National Semiconductor, LM9071T/NOPB Datasheet - Page 6

• Manufacturer Part Number: LM9071T/NOPB
• Description: IC REG LDO W/DELAY TO-220-5
• Manufacturer: National Semiconductor

Specifications of LM9071T/NOPB

• Regulator Topology: Positive Fixed
• Voltage - Output: 5V
• Voltage - Input: 6 ~ 26 V
• Number Of Regulators: 1
• Current - Output: 250mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: TO-220-5 (Straight Leads)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Dropout (typical): -
• Current - Limit (min): -
• Other names: *LM9071T; *LM9071T/NOPB; LM9071T

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Application Hints
RESET FLAG
Excessive loading of the output to the point where the output
voltage drops by 300 mV to 500 mV will signal a reset flag to
the micro. This will warn of a V
unpredictable operation of the system. On power-up and
recovery from a fault condition the delay capacitor is used to
hold the micro in a reset condition for a programmable time
interval to allow the system operating voltages and clock to
stabilize before executing code. The delay time interval can
be estimated by the following equation:
INPUT STABILITY
Low dropout voltage regulators which utilize a PNP power
transistor usually exhibit a large increase in current when in
dropout (V
ration characteristics (β reduction) of the PNP transistor. To
significantly minimize this increase in current the LM9071
detects when the PNP enters saturation and reduces the
operating current.
This reduction in input current can create a stability problem
in applications with higher load current (
the input voltage is applied through a long length of wire,
which in effect adds a significant amount of inductance in
series with the input. The drop in input current may create a
positive input voltage transient which may take the PNP out
of saturation. If the input voltage is held constant at the
threshold where the PNP is going in and out of saturation, an
oscillation may be created.
This is only observed where a large series inductance is
present in the input supply line and when the rise and fall
time of the input supply is very slow. If the application and
IN
<
5.5V). This increase is caused by the satu-
CC
(Continued)
supply that may produce
FIGURE 1. Typical TO-263 PC Board Heatsinking
>
100 mA) where
6
removal of the input voltage changes at a rate greater than
500 mV/µs it will move through the dropout region of the
regulator (V
be established.
THERMAL MANAGEMENT
The LM9071 is packaged in both a TO-263 surface mount
power package and a narrow lead-pitch TO-220 package. To
obtain operation over the highest possible load current and
input voltage ranges, care must be taken to control the
operating temperature of the device. Thermal shutdown pro-
tection is built in, with a threshold above 150˚C. Conven-
tional heat-sinking techniques can be used with the TO-220
package. When applying the TO-263 package, on board
heat-sinking is important to prevent premature thermal shut-
down. More copper foil area under the tab of the device will
directly improve the operating θ
which will reduce the junction temperature of the device.
The θ
heat sink) is rated at 80˚C/W. The effective θ
TO-263 package can be reduced by increasing the printed
circuit board area that is connected (soldered) to the pack-
age tab. Using 1 ounce (1.4 mils thick) copper clad with no
solder mask, an area of 0.5 square inches will reduce θ
50˚C/W, an area of 1.0 square inches will reduce θ
37˚C/W, and an area of 1.6 square inches will reduce θ
32˚C/W. If the printed circuit board uses a solder mask, the
copper clad area under the solder mask should be increased
by at least 50% to maintain a similar θ
The use of a double sided PC board with soldered filled vias
between two planes of copper, as shown in Figure 1, will
improve thermal performance while optimizing the PC board
surface area required. Using the double sided PC board
arrangement shown in Figure 1, with 1 ounce (1.4 mils thick)
copper clad with no solder mask and solder filled vias, an
area of 0.5 square inches on both sides will reduce θ
43˚C/W.
J-A
value for the TO-263 package (still air, no additional
IN
of 3V to 5.5V) too quickly for an oscillation to
J-A
01283219
of the TO-263 package,
J-A
rating.
J-A
value of the
J-A
J-A
J-A
J-A
to
to
to
to