Datasheet

LT6110
24
6110fa
For more information www.linear.com/LT6110
applicaTions inForMaTion
traces at the top and bottom corner squares. There are five
connecting traces and their total resistance is 0.125mΩ
([0.015 inch/0.15 inch] • 0.25mΩ • 5).
Temperature Errors
In addition to the initial errors at 25°C the errors due to
a temperature variation must be included. The ambient
temperature variation of the LT6110 and the wire can
have the following cases: The LT6110 and wire are at
the same temperature, the LT6110 and wire are at much
different temperatures or the temperature of the LT6110
circuit is known and the wire temperature can only be ap
-
proximated. The
design procedure targets a load voltage
equal to V
REG(NOM)
at maximum load current and cancels
V
DROP
by setting I
IOUT
• R
F
= V
DROP
. If, over the specified
temperature range, {I
IOUT
• R
F
– V
DROP
} is not zero volts,
then there will be an error to the expected load voltage
at maximum load current (for example, if V
LOAD
= 5V at
25°C and at 75°C {I
IOUT
• R
F
– V
DROP
} is 5mV then the
V
LOAD
error is 100 • (5mV/5V) = 0.1%).
Since I
IOUT
= V
SENSE
/R
IN
, the temperature errors must
include the errors due to R
IN
, R
SENSE
and V
OS
.
NC IOUT IMON V
–
+IN
V
+
RS
–IN
R
IN
TO
LOAD
TO
REGULATOR
A B
6110 F16
BA
21 SQUARES (6 COLUMNS)
A 3.5-SQUARE COLUMN
3/4 CORNER SQUARES
0.15 INCH × 0.15 INCH
ONE SQUARE
0.15 INCH × 0.15 INCH
5.4mΩ ±15% AT 25°C PCB RESISTOR
21 2oz COPPER SQUARES
— 3/4 SQUARE
— 3/4 SQUARE
— ONE SQUARE
— ONE SQUARE
Figure 16. LT6110 and PCB Trace Resistor Layout
The error sources due to temperature of an LT6110
circuit are:
The IOUT current error vs temperature coefficient is
–50ppm/°C
The V
OS
temperature coefficient is ±1µV/°C
The R
IN
and R
F
resistors temperature coefficient is
±100ppm/°C
The internal R
SENSE
resistor temperature coefficient is
+3400ppm/°C
An additional temperature error is due to R
WIRE
. The
copper wire temperature coefficient is +3900ppm/°C
The IOUT current, V
OS
, R
IN
and R
F
errors are small com-
pared to the errors of the internal R
SENSE
and R
WIRE
. For
a 50°C temperature rise the IOUT current, V
OS
, R
IN
and R
F
resistor error is 0.25%, 50µV and 0.5% respectively and
the internal R
SENSE
and R
WIRE
error is 17% and 19.5%
respectively.
Using the example of V
LOAD
= 5V, I
LOAD
= 2A, I
IOUT
=
71.2µA, R
F
= 10k, R
IN
= 562Ω and R
WIRE
= 0.336Ω the
V
LOAD
error due to the following three example cases is
calculated: