Datasheet

LT6110
22
6110fa
For more information www.linear.com/LT6110
applicaTions inForMaTion
The value of the external R
SENSE
determines the V
SENSE
voltage. If I
IOUT
is 100µA then a V
SENSE
of 50mV is large
enough to minimize the compensating IOUT current error
due to V
OS
to less than 1% (see Figure 13).
Figure 13. V
SENSE
Figure 14. LT6110 with an External R
SENSE
and LT3972 Buck Regulator
Precision Current Shunt Resistor
A precision, very low V
LOAD
error, compensation circuit
can be implemented with an LT6110 and a precision ex-
ternal R
SENSE
. A ±1% to ±5% tolerance or better R
SENSE
resistor significantly reduces I
IOUT
compensation current
error due to part to part variations. In addition, the low
temperature coefficient (TCR of typically ±100ppm/°C) of
an external sense resistor greatly reduces the contribution
of R
SENSE
to the total voltage drop loss at higher operating
temperatures. Figure 14 shows a 5V, 3.5A buck regulator
with an LT6110 using an external R
SENSE
. Table 2 is a list
of typical current sense resistors.
V
SENSE
(mV)
0 10 20 30
IOUT CURRENT ERROR (%)
1
10
100
40 50 60 70 80 90
100
6110 F13
0.1
I
IOUT
= 300µA
I
IOUT
= 100µA
I
IOUT
= 30µA
0.4V ≤ V
IOUT
≤ V
+
– 1.5V
V
IMON
= V
–
= 0V
V
OS(MAX)
63.4k
I = 600kHz
V
IN
V
IN
8V TO 36V
RUN/SS
0.047µF
47µF
MBRA340
0.79V
47pF9.53k
523k
6.8µH
LT3972
GND
100k
BD
NC +IN
IOUT
LT6110
V
+
RSIMON
–INV
–
BOOST
SW
RT
15k
V
C
SYNC
FB
6110 F14
V
LOAD
5V
3.5A
0.1µF
22µF 4.7µF
R
WIRE
0.25Ω
10 FT
24AWG
EXTERNAL
R
SENSE
25mΩ
±5%
866Ω
LOAD
1nF
100pF
Table 2. Surface Mount R
SENSE
Resistors
PART NUMBER THICK FILM VALUE RANGE TOLERANCE TCR POWER SIZE
IRC LRC-LRF-2512 2mΩ to 1Ω 1% to 5% 100ppm 2W 2512
Stackpole Electronics CSR2512 10mΩ to 1Ω 1% to 5% 200ppm 2W 2512
Vishay RCWE2512 33mΩ to 51Ω 1% to 5% 200ppm 2W 2512
Panasonic ERJM1W 1mΩ to 20mΩ 1% to 5% 100ppm 2W 2512
Susumu PRL1632
Susumu PRL3264
10mΩ to 100mΩ
10mΩ to 100mΩ
1% to 2%
1% to 2%
100ppm (20mΩ to 51mΩ)
100ppm (20mΩ to 51mΩ)
1W
2W
1206
2512