LTC1439 Linear Technology, LTC1439 Datasheet - Page 23

• Manufacturer Part Number: LTC1439
• Description: Dual High Efficiency/ Low Noise/ Synchronous Step-Down Switching Regulators
• Manufacturer: Linear Technology

APPLICATIONS
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1438/LTC1439. These items are also illustrated graphi-
cally in the layout diagram of Figure 13. Check the follow-
ing in your layout:
1. Are the high current power ground current paths using
or running through any part of signal ground? The
LTC1438/LTC1438X/LTC1439 ICs have their sensitive
pins on one side of the package. These pins include the
signal ground for the reference, the oscillator input, the
voltage and current sensing for both controllers and the
low-battery/comparator input. The signal ground area
used on this side of the IC must return to the bottom
NOT ALL PINS CONNECTED FOR CLARITY
BOLD LINES INDICATE HIGH CURRENT PATHS
OUTPUT DIVIDER
REQUIRED WITH
R
R
10k
R
10k
10k
V
LP
C2
C1
PROG
220pF
0.1 F
220pF
470pF
C
C
OPEN
C
C1B
C2B
SS
1000pF
1000pF
1000pF
0.01 F
C
C
C
C
C1A
OSC
C2A
LP
U
10
INFORMATION
U
1000pF
10
V
100pF
1000pF
IN
22pF
INTV
INTV
0.1 F
C
SS
100k
CC
CC
W
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
Figure 13. LTC1439 Physical Layout Diagram
RUN/SS1
SENSE
SENSE
V
I
POR2
C
SGND
LBI
LBO
SFB1
I
V
V
SENSE
SENSE
RUN/SS2
AUXDR
TH1
TH2
PROG1
OSC
PROG2
OSENSE2
LTC1439
+
+
–
–
2
1
1
2
BOOST 1
BOOST 2
U
PLL LPF
EXTV
AUXON
INTV
AUXFB
PLLIN
PGND
TGS1
TGS2
TGL1
TGL2
SW1
SW2
BG1
BG2
V
CC
CC
IN
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
CLOCK
EXT
0.1 F
+
0.1 F
C
2. Do the LTC1438/LTC1439 SENSE
C
B1
D
B2
D
B2
B1
plates of all of the output capacitors. The high current
power loops formed by the input capacitors and the
ground returns to the sources of the bottom N-channel
MOSFETs, anodes of the Schottky diodes and (–) plates
of C
a low resistance path to the bottom plates of the output
capacitors for the ground return.
connect to the (+) plates of C
tions, the resistive divider R1/R2 must be connected
between the (+) plate of C
HF decoupling capacitor should be as close as possible
to the LTC1438/LTC1439.
4.7 F
IN
M3
M6
, should be as short as possible and tied through
M1
M2
M5
M4
L1
L2
D1
D2
C
C
IN1
IN2
LTC1438/LTC1439
R
SENSE1
GROUND PLANE
OUT
+
+
OUT
and signal ground and the
R
C
C
SENSE2
OUT1
OUT2
? In adjustable applica-
–
1 and V
OSENSE2
V
V
OUT1
OUT2
+
–
–
+
1438 F13
23
V
+
–
IN
pins