LTC3410_15 Datasheet, PDF (12/16 Pages) Linear Technology – 2.25MHz, 300mA Synchronous Step-Down Regulator in SC70

LTC3410
APPLICATIO S I FOR ATIO
–
V_OUT
+
C_OUT
L1
1
RUN
LTC3410
2
6
GND V_FB
3 _SW
V_IN ⁴
5
C_IN
R2
R1
C_FWD
V_IN
BOLD LINES INDICATE HIGH CURRENT PATHS
3410 F04a
Figure 4a. LTC3410 Layout Diagram
1
RUN
–
V_OUT
+
C_OUT
L1
LTC3410-1.875
2
GND
6
V_OUT
3
SW
5
V_IN ⁴
C_IN
V_IN
3410 F04b
BOLD LINES INDICATE HIGH CURRENT PATHS
Figure 4b. LTC3410-1.875 Layout Diagram
V_OUT
PIN 1
L1
SW
VIA TO V_IN
LTC3410
VIA TO GND
R1
R2
C_FWD
V_IN
VIA TO V_OUT
V_OUT
V_IN
VIA TO V_IN
PIN 1
L1
SW
LTC3410-
1.875
C_OUT
C_IN
GND
3410 F05a
C_OUT
C_IN
3410 F05b
Figure 5a. LTC3410 Suggested Layout
Figure 5b. LTC3410 Fixed Output Voltage
Suggested Layout
2. Does the V_FB pin connect directly to the feedback
resistors? The resistive divider R1/R2 must be con-
nected between the (+) plate of C_OUT and ground.
3. Does the (+) plate of C_IN connect to V_IN as closely as
possible? This capacitor provides the AC current to the
internal power MOSFETs.
4. Keep the (–) plates of C_IN and C_OUT as close as possible.
5. Keep the switching node, SW, away from the sensitive
V_FB node.
Design Example
As a design example, assume the LTC3410 is used in a
single lithium-ion battery-powered cellular phone
application. The V_IN will be operating from a maximum of
4.2V down to about 2.7V. The load current requirement
is a maximum of 0.3A but most of the time it will be in
standby mode, requiring only 2mA. Efficiency at both low
and high load currents is important. Output voltage is
3V. With this information we can calculate L using
Equation (1),
L
=
(
1
f₎₍∆I_L
)
V_OUT
⎛⎝⎜_1−
V_OUT
V_IN
⎞
⎠⎟
(3)
3410fb
12