LT1587CT-1.5 Linear Technology, LT1587CT-1.5 Datasheet - Page 6

• Manufacturer Part Number: LT1587CT-1.5
• Description: IC LDO REGULATOR 3A 1.5V TO220-3
• Manufacturer: Linear Technology

Specifications of LT1587CT-1.5

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.5V
• Voltage - Input: 2.7 ~ 7 V
• Voltage - Dropout (typical): 1.15V @ 3A
• Number Of Regulators: 1
• Current - Output: 3A
• Current - Limit (min): 3.1A
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: TO-220-3 (Straight Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LT1587-1.5
APPLICATIONS
regulation is limited by the resistance of the wire connect-
ing the regulators to the load. Load regulation per the data
sheet specification is measured at the bottom of the
package.
For fixed voltage devices, negative side sensing is a true
Kelvin connection with the Ground pin of the device re-
turned to the negative side of the load. This is illustrated in
Figure 3.
Thermal Considerations
The LT1587-1.5 protects the device under overload condi-
tions with internal power and thermal limiting circuitry.
However, for normal continuous load conditions, do not
exceed maximum junction temperature ratings. It is impor-
tant to consider all sources of thermal resistance from
junction-to-ambient. These sources include the junction-
to-case resistance, the case-to-heat sink interface resis-
tance, and the heat sink resistance. Thermal resistance
specifications have been developed to more accurately
reflect device temperature and ensure safe operating tem-
peratures. The electrical characteristics section provides a
separate thermal resistance and maximum junction tem-
perature for both the control circuitry and the power
transistor. Older regulators with a single junction-to-case
thermal resistance specification, use an average of the two
values provided here and allow excessive junction tem-
peratures under certain conditions of ambient temperature
and heat sink resistance. Calculate the maximum junction
temperature for both sections to ensure that both thermal
limits are met.
6
V
Figure 3. Connection for Best Load Regulation
IN
IN
LT1587-1.5
GND
U
OUT
INFORMATION
U
LINE RESISTANCE
PARASITIC
R
P
W
LT1587 • F03
U
R
L
Junction-to-case thermal resistance is specified from the
IC junction to the bottom of the case directly below the die.
This is the lowest resistance path for heat flow. Proper
mounting ensures the best thermal flow from this area of
the package to the heat sink. Linear Technology strongly
recommends thermal compound at the case-to-heat sink
interface. Use a thermally conductive spacer if the case of
the device must be electrically isolated and include its
contribution to the total thermal resistance. Please consult
“Mounting Considerations for Power Semiconductors”
1990 Linear Applications Handbook, Volume I , Pages
RR3-1 to RR3-20. The output connects to the case of the
device in the LT1587-1.5.
For example, using an LT1587CT-1.5 (TO-220, commer-
cial) and assuming:
Power dissipation under these conditions is equal to:
Junction temperature will be equal to:
For the Control Section:
For the Power Transistor:
In both cases the junction temperature is below the maxi-
mum rating for the respective sections, ensuring reliable
operation.
V
I
T
P
T
T
121.3 C < 125 C = T
Range)
T
134.8 C < 150 C = T
Range)
OUT
A
J
J
J
IN
CASE-TO-HEAT SINK
D
= 70 C + 5.895W (7 C/W + 1 C/W + 0.7 C/W) = 121.3 C
= 70 C + 5.895W (7 C/W + 1 C/W + 3 C/W) = 134.8 C
= T
= 70 C,
(Max Continuous) = 3.465V (3.3V + 5%), V
= (V
= 3A
A
IN
+ P
– V
D
(
HEAT SINK
OUT
HEAT SINK
)(I
= 1 C/W (with Thermal Compound)
OUT
JMAX
JMAX
= 7 C/W
) = (3.465 – 1.5)(3A) = 5.895W
+
(Power Transistor Commercial
(Control Section Commercial
CASE-TO-HEAT SINK
OUT
+
JC
= 1.5V
)