Datasheet

LT6110
21
6110fa
For more information www.linear.com/LT6110
applicaTions inForMaTion
In addition to using a regulator capacitor to adjust the loop
response, an RC pole in the LT6110 circuit can provide
frequency compensation. Figure 11 shows an LT6110 with
an input RC filter. Using the input RC filter introduces a
second pole to the LT6110 one pole response (Figure 9).
The LT6110 poles become a zero in the regulator’s open-
loop response that includes the LT6110 in its feedback
path (providing the same function as the regulator’s R
F
with a shunt capacitor).
Loop compensation with an LT6110 RC filter is not
required if the regulator’s loop is compensated with a
zero in the feedback divider (refer to the Regulator Loop
Stability section).
0dB
–3dB
0
–30
–60
PHASE (DEG)
–90
–120
1 10
FREQUENCY (kHz)I
IOUT
= 100µA
100 1000
6110 F08
Figure 8. LT6110 Frequency Response
Figure 11. LT6110 Frequency Compensation
Figure 12. Using an External R
SENSE
(Resistor, Inductor or PCB Trace)
Figure 9. V
LOAD
Compensated
Figure 10. Removing Load
V
REG
500mV/DIV
V
LOAD
500mV/DIV
2A
1A
100µs/DIV
6110 F09
V
REG
500mV/DIV
V
LOAD
500mV/DIV
2A
0A
C
LOAD
= 100µF 10ms/DIV
6110 F10
EXTERNAL CURRENT SENSE RESISTORS
The LT6110 internal current sense resistor, R
SENSE
, is
provided for convenient use in many applications with a
maximum load current less than 3A. For higher current
or greater precision wire loss compensation an external
sense resistor can be used. The external R
SENSE
resistor
can be a low valued current sense or shunt resistor, the
DC resistance (DCR) of an inductor, or the resistance of
a printed circuit board trace. Figure 12 shows an LT6110
circuit configuration using an external sense resistor. The
internal resistor at the RS pin is left open circuited.
IOUT
+IN –IN
R
–IN
1k
R
+IN
LT6110
V
+
V
–
RS
IMON
+
–
6110 F11
20mΩ
C1
IOUT
+IN –IN
R
IN
TO V
REG
TO LOAD
LT6110
V
+
V
–
RS
IMON
+
–
6110 F12
20mΩ
EXTERNAL
R
SENSE