LTC1772 Linear Technology, LTC1772 Datasheet - Page 11

• Manufacturer Part Number: LTC1772
• Description: Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23
• Manufacturer: Linear Technology

PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1772. These items are illustrated graphically in the
layout diagram in Figure 6. Check the following in your
layout:
1. Is the Schottky diode closely connected between ground
2. Does the (+) plate of C
3. Is the input decoupling capacitor (0.1 F) connected
APPLICATIONS
(Pin 2) and drain of the external MOSFET?
as closely as possible? This capacitor provides AC
current to the MOSFET.
closely between V
U
C
IN
R
ITH
ITH
(Pin 5) and ground (Pin 2)?
INFORMATION
IN
U
connect to the sense resistor
Figure 6. LTC1772 Layout Diagram (See PC Board Layout Checklist)
BOLD LINES INDICATE HIGH CURRENT PATHS
W
1
2
3
C1
I
GND
V
TH
FB
/RUN
LTC1772
SENSE
PGATE
U
V
IN
–
6
5
4
0.1 F
R
S
4. Connect the end of R
5. Is the trace from SENSE
6. Keep the switching node PGATE away from sensitive
7. Does the V
possible. The V
comparator.
kept short? Does the trace connect close to R
small signal nodes.
resistors? The resistive divider R1 and R2 must be
connected between the (+) plate of C
ground. The 100pF capacitor should be as close as
possible to the LTC1772.
M1
+
C
5W
IN
D1
FB
L1
pin connect directly to the feedback
IN
R1
+
pin is the SENSE
1772 F06
SENSE
C
OUT
–
R2
(Pin 4) to the Sense resistor
as close to V
V
V
IN
OUT
+
LTC1772
OUT
of the current
IN
and signal
(Pin 5) as
11
SENSE
?