lt3015edd Linear Technology Corporation, lt3015edd Datasheet - Page 15

• Manufacturer Part Number: lt3015edd
• Description: 1.5a, Low Noise, Negative Linear Regulator With Precision Current Limit
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
Table 2. Measured Thermal Resistance for DFN Package
Table 3. Measured Thermal Resistance for MSOP Package
Table 4. Measured Thermal Resistance for DD-Pak Package
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 3°C/W
Calculating Junction Temperature
Example: Given an output voltage of –2.5V, an input voltage
range of –3.3V ± 5%, an output current range of 1mA to
500mA, and a maximum ambient temperature of 85°C,
what is the maximum junction temperature?
The power dissipated by the LT3015 equals:
where:
*Device is mounted on topside
*Device is mounted on topside
*Device is mounted on topside
TOP SIDE*
TOP SIDE*
TOP SIDE*
2500mm
1000mm
2500mm
1000mm
2500mm
1000mm
225mm
100mm
225mm
100mm
225mm
I
I
V
I
OUT(MAX)
OUT(MAX)
GND
IN(MAX)
COPPER AREA
COPPER AREA
COPPER AREA
at (I
2
2
2
2
2
2
2
2
2
2
2
= –3.465V
OUT
• (V
= –500mA
BACKSIDE
BACKSIDE
BACKSIDE
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
= –500mA, V
IN(MAX)
2
2
2
2
2
2
2
2
2
2
2
- V
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
BOARD
BOARD
BOARD
AREA
AREA
AREA
OUT
IN
) + I
= –3.465V) = –6.5mA
2
2
2
2
2
2
2
2
2
2
2
GND
(JUNCTION-TO-AMBIENT)
(JUNCTION-TO-AMBIENT)
(JUNCTION-TO-AMBIENT)
THERMAL RESISTANCE
THERMAL RESISTANCE
THERMAL RESISTANCE
• (V
40°C/W
40°C/W
41°C/W
42°C/W
37°C/W
37°C/W
38°C/W
40°C/W
14°C/W
16°C/W
19°C/W
IN(MAX)
)
Thus:
Using a DFN package, the thermal resistance is in the
range of 40°C/W to 42°C/W depending on the copper area.
Therefore, the junction temperature rise above ambient
approximately equals:
The maximum junction temperature equals the maxi-
mum ambient temperature plus the maximum junction
temperature rise above ambient or:
Protection Features
The LT3015 incorporates several protection features that
make it ideal for use in battery-powered applications. In
addition to the normal protection features associated
with monolithic regulators, such as current limiting and
thermal limiting, the device protects itself against reverse
input voltages and reverse output voltages.
Precision current limit and thermal overload protections
are intended to protect the LT3015 against current over-
load conditions at the output of the device. For normal
operation, do not allow the the junction temperature to
exceed 125°C.
Pulling the LT3015’s output above ground induces no
damage to the part. If IN is left open circuit or grounded,
OUT can be pulled above GND by 30V. In addition, OUT acts
like an open circuit, i.e. no current flows into the pin. If IN
is powered by a voltage source, OUT sinks the LT3105’s
short-circuit current and protects itself by thermal limiting.
In this case, grounding the SHDN pin turns off the device
and stops OUT from sinking the short-circuit current.
P = –500mA(–3.465V + 2.5V) + –6.5mA • (–3.465V) =
0.505W
0.505W • 41°C/W = 20.7°C
T
JMAX
= 85°C + 20.7°C = 105.7°C
LT3015
15
3015f