lt3080-1 Linear Technology Corporation, lt3080-1 Datasheet - Page 16

• Manufacturer Part Number: lt3080-1
• Description: Parallelable 1.1a Adjustable Single Resistor Low Dropout Regulator
• Manufacturer: Linear Technology Corporation

LT3080-1
APPLICATIONS INFORMATION
The second technique for reducing power dissipation,
shown in Figure 9, uses a resistor in parallel with the
LT3080-1. This resistor provides a parallel path for current
fl ow, reducing the current fl owing through the LT3080-1.
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.
As an example, assume: V
5.5V, V
I
than 90% of I
Calculating R
16
OUT(MIN)
(5% Standard value = 3.6Ω)
R
P
=
OUT
5 5
= 0.7A. Also, assuming that R
.
= 3.3V, V
0 63
V
.
P
OUT(MIN)
– .
yields:
3 2
A
V
OUT(MIN)
=
= 630mA.
3 65
. Ω
IN
= V
= 3.2V, I
Figure 9. Reducing Power Dissipation Using a Parallel Resistor
CONTROL
OUT(MAX)
P
= 5V, V
carries no more
C1
V
SET
= 1A and
R
IN(MAX)
CONTROL
SET
+
–
LT3080-1
=
The maximum total power dissipation is (5.5V – 3.2V) •
1A = 2.3W. However, the LT3080-1 supplies only:
Therefore, the LT3080-1’s power dissipation is only:
R
choose appropriate wattage resistors to handle and dis-
sipate the power properly. With this confi guration, the
LT3080-1 supplies only 0.36A. Therefore, load current can
increase by 0.64A to 1.64A while keeping the LT3080-1 in
its normal operating range.
25mΩ
P
P
1
dissipates 1.47W of power. As with the fi rst technique,
A
DIS
–
OUT
IN
= (5.5V – 3.2V) • 0.36A = 0.83W
5 5
.
R
V
3 6
P
C2
.
30801 F09
– .
Ω
3 2
V
V
IN
OUT
V
=
0 36
.
A
30801f