LTC3632 LINER [Linear Technology], LTC3632 Datasheet - Page 16

• Manufacturer Part Number: LTC3632
• Description: High Effi ciency, High Voltage 20mA Synchronous Step-Down Converter
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
LTC3632
Choose standard values for R2 = 226k and R3 = 91k.
The I
maximum peak current (50mA). Figure 9 shows a complete
schematic for this design example.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3632. Check the following in your layout:
1. Large switched currents fl ow in the power switches
2. Connect the (+) terminal of the input capacitor, C
3. Keep the switching node, SW, away from all sensi-
16
and input capacitor. The loop formed by these compo-
nents should be as small as possible. A ground plane
is recommended to minimize ground impedance.
close as possible to the V
the AC current into the internal power MOSFETs.
tive small-signal nodes. The rapid transitions on the
switching node can couple to high impedance nodes,
in particular V
24V
V
SET
IN
Figure 9. 24V to 3.3V, 20mA Regulator at 250kHz
pin should be left open in this example to select
1μF
FB
2M
226k
91k
, and create increased output ripple.
V
RUN
HYST
IN
LTC3632
GND
IN
I
V
SW
SET
SS
pin. This capacitor provides
FB
220μH
750k
240k
3632 F09
10μF
V
3.3V
20mA
OUT
IN
, as
4. Flood all unused area on all layers with copper. Flooding
V
with copper will reduce the temperature rise of power
components. You can connect the copper areas to any
DC net (V
system).
IN
V
IN
R
SET
VIAS TO GROUND PLANE
VIAS TO INPUT SUPPLY (V
OUTLINE OF LOCAL GROUND PLANE
C
IN
IN
, V
C
Figure 10. Layout Example
C
SS
OUT
SS
2
5
7
4
, GND or any other DC rail in your
SS
V
RUN
HYST
IN
LTC3632
GND
L1
8, 9
C
GND
IN
I
SW
V
SET
IN
FB
)
C
1
6
3
OUT
L1
R
SET
R1
R1
R2
3632 F10a
3632 F10b
R2
C
V
OUT
OUT
V
OUT
3632fb