FAN1581MX Fairchild Semiconductor, FAN1581MX Datasheet - Page 7

• Manufacturer Part Number: FAN1581MX
• Description: IC REG LDO 5A ADJ VOLT TO-263
• Manufacturer: Fairchild Semiconductor

Specifications of FAN1581MX

• Regulator Topology: Positive Adjustable
• Voltage - Output: 1.25 ~ 5.7 V
• Voltage - Input: Up to 7V
• Voltage - Dropout (typical): 0.4V @ 5A
• Number Of Regulators: 1
• Current - Output: 5A
• Current - Limit (min): 5.2A
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: TO-263-3, D²Pak (3 leads + Tab), TO-263AA
• Number Of Outputs: 1
• Polarity: Positive
• Input Voltage Max: 7 V
• Output Voltage: 1.237 V to 5.7 V
• Output Type: Adjustable
• Dropout Voltage (max): 1.18 V
• Output Current: 5 A
• Line Regulation: 3 mV
• Load Regulation: 5 mV
• Voltage Regulation Accuracy: 0.5 %
• Maximum Power Dissipation: 18 W
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: 0 C
• Reference Voltage: 1.263 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PRODUCT SPECIFICATION
The current out of the adjust pin adds to the current from R1
and is typically 50µA. Its output voltage contribution is
small and only needs consideration when a very precise out-
put voltage setting is required.
Load Regulation
The FAN1581 family provides true remote sensing, eliminat-
ing output voltage errors due to trace resistance. To utilize
remote sensing, connect the VSENSE pin directly to the
load, rather than at the VOUT pin. If the load is more than 1"
away from the FAN1581, it may be necessary to increase the
load capacitance to ensure stability.
Thermal Considerations
The FAN1581 series protect themselves under overload con-
ditions with internal power and thermal limiting circuitry.
However, for normal continuous load conditions, do not exceed
maximum junction temperature ratings. It is important 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 resistance, and the heat sink
resistance. Thermal resistance specifications have been
developed to more accurately reflect device temperature and
ensure safe operating temperatures. The electrical character-
istics section provides a separate thermal resistance and
REV. 1.2.1 7/2/09
V
V
V
C1
10μF
cntl
OUT
IN
= V
+
REF
(1+R2/R1) + I
Figure 2. Basic Regulator Circuit
I
50μA
ADJ
Vin
Vcntl
FAN1581
Adj Vout
Vsense
ADJ
(R2)
V
REF
R1
R2
+
C2
22μF
V
OUT
maximum junction temperature for both the control circuitry
and the power transistor. Calculate the maximum junction
temperature for both sections to ensure that both thermal
limits are met.
For example, look at using an FAN1581M-1.5 to generate
5A @ 1.5V ± 2% from a 3.3V source (3.2V to 3.6V).
Assumptions:
• V
• V
• I
• T
• Θ
The power dissipation in this application is:
P
From the specification table,
T
= 40 + (10.65) * (5 + 3) = 125°C
The junction temperature is within the maximum rating.
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. Use of a thermally conductive
material at the case-to-heat sink interface is recommended.
Use a thermally conductive spacer if the case of the device
must be electrically isolated and include its contribution to
the total thermal resistance.
D
J
thermally conductive material)
= T
= (V
OUT
A
in
OUT
Case-to-Ambient
= 40°C
A
= 3.6V worst case
IN
= 5A continuous
+ (P
= 1.47V worst case
- V
D
OUT
) * (Θ Case-to-Ambient + Θ
) * (I
= 5°C/W (assuming both a heatsink and a
OUT
) = (3.6-1.47) * (5) = 10.65W
JC
)
FAN1581
7