LTC3602_15 Datasheet, PDF (15/20 Pages) Linear Technology – 2.5A, 10V, Monolithic Synchronous Step-Down Regulator

LTC3602
APPLICATIONS INFORMATION
capacitance and a ceramic capacitor in parallel to lower
the total effective ESR. For this design, a 100μF ceramic
capacitor will be used. C_IN should be sized for a maximum
current rating of:
I_RMS
=
2.5A
•
3.3V
8.4V
•
8.4V
3.3V
–
1
=
1.22A_RMS
Decoupling the PV_IN pin with a 22μF ceramic capacitor is
adequate for most applications.
The output voltage can now be programmed by choosing
the values of R1 and R2. Chose R1 = 105k and calculate
R2 as:
⎛
R2 =R1_{⎝⎜⎜}
V_OUT
0.6V
–
⎞
1_{⎠⎟⎟}
=
472.5k
Choose a standard value of R2 = 475k. The voltage on
the MODE pin will be set to 0.6V by tying the MODE pin
to the FB pin. This will set the burst current equal to ap-
proximately 1A. Figure 6 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
LTC3602. Check the following in your layout:
1. A ground plane is recommended. If a ground plane layer
is not used, the signal and power grounds should be
segregated with all small signal components returning
to the SGND pin at one point which is then connected
to the PGND pin close to the LTC3602.
2. Connect the (+) terminal of the input capacitor(s), C_IN, as
close as possible to the PV_IN pin. This capacitor provides
the AC current into the internal power MOSFETs.
3. Keep the switching node, SW, away from all sensitive
small signal nodes.
4. Flood all unused areas on all layers with copper. Flooding
with copper will reduce the temperature rise of power
components. You can connect the copper areas to any
DC net (PV_IN, INTV_CC, V_OUT, PGND, SGND, or any other
DC rail in your system).
R_PG
200k
PGOOD
R_OSC
105k
C_ITH
1nF
R_ITH
4.32k
R1
105k
R2
C_FB
475k
22pF
SYNC/MODE
PGOOD
INTV_CC
PV_IN
R_T
BOOST
I_TH
LTC3602
SW
V_FB
SW
RUN
SW
TRACK/SS
PGND
PGND
PGND
C_VCC
1μF
V_IN
8.4V
C_IN
22μF
D1
C_BST
0.22μF
L1
2.2μH
V_OUT
3.3V
2.5A
C_OUT
100μF
L1: VISHAY IHLP2525CZER2R2MO1
C_IN: TAIYO YUDEN TMK325BJ226MM-T
C_OUT: TDK C3225X5ROJ107M
3602 F06
Figure 6. 8.4V to 3.3V, 2.5A Regulator at 1MHz, Burst Mode Operation
3602fb
15