Linear Technology DC1185B-A Demo Manual page 5

INDUCTOR DCR SENSING
Demonstration circuit 1185 provides an optional circuit
for DCR sensing. DCR sensing uses the DCR of the in-
ductor to sense the inductor current instead of discrete
sense resistors. The advantages of DCR sensing are lower
cost, reduced board space and higher efficiency, but the
disadvantage is a less accurate current limit. If DCR sens-
ing is used, be sure to select an inductor current with a
sufficiently high saturation current or use an iron powder
type. Tables 3 and 4 show an example of how to modify
the DC1185 for DCR sensing using these parameters:
Table 3. V Configured as a 2.0V/10A Converter Using DCR Sensing and Discrete Sense Resistors
OUT1
CONFIGURATION RS1
DCR Sensing Short with Cu
Strip or Very
Short and Thick
Piece of Wire
Discrete R 3mΩ
SENSE
(Original Board) 2010 Package
Table 4. V Configured as a 1.8V/10A Converter Using DCR Sensing and Discrete Sense Resistors
OUT2
CONFIGURATION RS2
DCR Sensing Short with Cu
Strip or Very
Short and Thick
Piece of Wire
Discrete R 3mΩ
SENSE
(Original Board) 2010 Package
R FILTER
SENSE
RESISTORS
L1 R29, R30
Toko Open
FDU0650-R56M=P3
Toko 100Ω
FDU0650-R56M=P3
R FILTER
SENSE
RESISTORS
L2 R39, R40
Toko Open
FDU0650-R56M=P3
Toko 100Ω
FDU0650-R56M=P3
DEMO MANUAL
V = 2.0V/10A
OUT1
V = 1.8V/10A
OUT2
V = 6.5V to 14V
IN
f = 500kHz, typical
SW
L1, L2 = Toko FDU0650-R56M=P3
(0.56µH, DCR = 2.45mΩ Typ, 3.2mΩ Max)
ILIM = Floating (R42, R44 = Open)
DCR FILTER/DIVIDER RESISTORS
SENSE FIILTER
CAPACITOR TOP
C14 R45
0.1µF 2.37kΩ
1nF Open
DCR FILTER/DIVIDER RESISTORS
SENSE FIILTER
CAPACITOR TOP
C15 R51
0.1µF 2.37kΩ
1nF Open
DC1185B-A/-B
SENSE1– TO L1–
BOTTOM JUMPER
R47 R61
6.49kΩ 0Ω
Open Open
SENSE1– TO L1–
BOTTOM JUMPER
R53 R62
6.49kΩ 0Ω
Open Open
dc1185b-a/-bf
5