lt3083idf Linear Technology Corporation, lt3083idf Datasheet - Page 18

• Manufacturer Part Number: lt3083idf
• Description: Lt3083 - Adjustable 3a Single Resistor Low Dropout Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LT3083
The second technique for reducing power dissipation,
shown in Figure 8, uses a resistor in parallel with the
LT3083. This resistor provides a parallel path for current
fl ow, reducing the current fl owing through the LT3083.
This technique works well if input voltage is reasonably
constant and output load current changes are small. This
technique also increases the maximum available output
current at the expense of minimum load requirements.
18
Figure 8. Reducing Power Dissipation Using a Parallel Resistor
C1
V
SET
R
CONTROL
SET
LT3083
+
–
3083 F08
OUT
IN
R
P
C2
V
V
IN
OUT
As an example, assume: V
5.5V, V
I
than 90% of I
Calculating R
The maximum total power dissipation is (5.5V – 3.2V) •
2A = 4.6W. However, the LT3083 supplies only:
Therefore, the LT3083’s power dissipation is only:
R
choose appropriate wattage resistors to handle and dis-
sipate the power properly. With this confi guration, the
LT3083 supplies only 1.36A. Therefore, load current can
increase by 1.64A to a total output current of 3.64A while
keeping the LT3083 in its normal operating range.
OUT(MIN)
P
P
R
(5% Standard Value = 3.6Ω)
2A −
dissipates 1.47W of power. As with the fi rst technique,
DISS
P
=
OUT
5.5V − 3.2V
5.5V − 3.2V
= (5.5V – 3.2V) • 1.36A = 3.13W
= 0.7A. Also, assuming that R
= 3.3V, V
0.63A
3.6Ω
P
OUT(MIN)
yields:
OUT(MIN)
= 3.65Ω
= 1.36A
= 630mA.
IN
= V
= 3.2V, I
CONTROL
OUT(MAX)
P
= 5V, V
carries no more
= 2A and
IN(MAX)
3083f
=