lt1963aes8-trpbf Linear Technology Corporation, lt1963aes8-trpbf Datasheet - Page 16

• Manufacturer Part Number: lt1963aes8-trpbf
• Description: 1.5a, Low Noise, Fast Transient Response Ldo Regulators
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LT1963A Series
Table 4. SO-8 Package, 8-Lead SO
*Device is mounted on topside.
Table 5. SOT-223 Package, 3-Lead SOT-223
*Device is mounted on topside.
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 4°C/W
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage
range of 4V to 6V, an output current range of 0mA to
500mA and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The power dissipated by the device will be equal to:
where,
So,
Using a DD package, the thermal resistance will be in the
range of 23°C/W to 33°C/W depending on the copper area.
So the junction temperature rise above ambient will be
approximately equal to:
16
TOPSIDE*
TOPSIDE*
2500mm
1000mm
2500mm
1000mm
1000mm
1000mm
225mm
100mm
225mm
100mm
I
I
V
I
P = 500mA(6V – 3.3V) + 10mA(6V) = 1.41W
1.41W(28°C/W) = 39.5°C
OUT(MAX)
OUT(MAX)
GND
IN(MAX)
COPPER AREA
COPPER AREA
at (I
2
2
2
2
2
2
2
2
2
2
= 6V
OUT
(V
= 500mA
BACKSIDE
BACKSIDE
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
1000mm
IN(MAX)
0mm
= 500mA, V
2
U
2
2
2
2
2
2
2
2
2
– V
BOARD AREA (JUNCTION-TO-AMBIENT)
BOARD AREA (JUNCTION-TO-AMBIENT)
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
1000mm
1000mm
U
OUT
IN
) + I
= 6V) = 10mA
2
2
2
2
2
2
2
2
2
2
GND
W
THERMAL RESISTANCE
THERMAL RESISTANCE
(V
IN(MAX)
55°C/W
55°C/W
63°C/W
69°C/W
42°C/W
42°C/W
50°C/W
56°C/W
49°C/W
52°C/W
U
)
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
Protection Features
The LT1963A regulators incorporate several protection
features which make them ideal for use in battery-powered
circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the devices are protected
against reverse input voltages, reverse output voltages
and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal opera-
tion, the junction temperature should not exceed 125°C.
The input of the device will withstand reverse voltages of
20V. Current flow into the device will be limited to less than
1mA (typically less than 100µA) and no negative voltage
will appear at the output. The device will protect both itself
and the load. This provides protection against batteries
that can be plugged in backward.
The output of the LT1963A can be pulled below ground
without damaging the device. If the input is left open circuit
or grounded, the output can be pulled below ground by
20V. For fixed voltage versions, the output will act like a
large resistor, typically 5k or higher, limiting current flow
to typically less than 600µA. For adjustable versions, the
output will act like an open circuit; no current will flow out
of the pin. If the input is powered by a voltage source, the
output will source the short-circuit current of the device
and will protect itself by thermal limiting. In this case,
grounding the SHDN pin will turn off the device and stop
the output from sourcing the short-circuit current.
The ADJ pin of the adjustable device can be pulled above
or below ground by as much as 7V without damaging the
device. If the input is left open circuit or grounded, the ADJ
pin will act like an open circuit when pulled below ground
and like a large resistor (typically 5k) in series with a diode
when pulled above ground.
In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp
T
JMAX
= 50°C + 39.5°C = 89.5°C
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