LTC1700 Linear Technology, LTC1700 Datasheet - Page 14

• Manufacturer Part Number: LTC1700
• Description: No RSENSE Synchronous Step-Up DC/DC Controller
• Manufacturer: Linear Technology

LTC1700
APPLICATIONS
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1700. These items are illustrated graphically in the
layout diagram in Figure 8. Check the following in your
layout:
1. Are all the components connected close to the SW node
(Pin 10)? The SW pin is the input to the V
amplifier and the current reverse comparator.
2. Connect the V
P-channel MOSFET. Besides supplying current to the
LTC1700, it also serves as the other input to the current
reverse comparator.
14
OUT
U
C1: TAIYO YUDEN CERAMIC JMK316BJ106ML
C2: AVX TAJB68K006R
C3: TAIYO YUDEN CERAMIC JMK325BJ226M
lead directly to the source of the
220pF
INFORMATION
30k
270pF
U
C4
C3
Figure 8. LTC1700 Layout Diagram (See PC Board Layout Checklist)
470pF
2.2k
R1
95k
R2
R3
W
1
2
3
4
5
1
2
4
3
5
SGND
I
V
RUN/SS
SYNC/MODE
TH
FB
SGND
I
RUN/SS
V
SYNC/MODE
TH
Figure 7. Design Example Schematic
FB
LTC1700
LTC1700
DS
U
PGND
V
sense
PGND
OUT
V
SW
BG
TG
OUT
SW
BG
TG
C4: SANYO POSCAP 6TPA150M
L1: SUMIDA CEP1234R6
10
9
8
7
6
10
8
9
6
7
V
IN
3. Connect the (+) plate of C2 to the source of the P-channel
MOSFET. This capacitor supports the load current when
the inductor is being “recharged”.
4. Connect the (–) plate of C2 to the source of the N-channel
MOSFET. Connect the power and signal ground to this
node.
5. Does the V
resistors? The resistive divider R1 and R2 must be con-
nected between the (+) plate of C2 and signal ground.
6. Keep the switching node SW away from sensitive small
signal nodes.
7. Switched currents flow in M1, M2 and C2, keep the loop
formed by these components as small as possible.
C1
L1
M1
FDS6670A
M1
4.6 H
FDS6375
L1
M2
M2
FB
pin connects directly to the feedback
+
C1
10 F
C3
22 F
C2
+
+
1700 • F08
V
OUT
C2
68 F
6.3V
C4
150 F
6.3V
2
1700 • F07
V
3.3V
V
5V/3A
OUT
IN