LTC1439 Linear Technology, LTC1439 Datasheet - Page 25

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

APPLICATIONS
current, reducing the susceptibility to both the “loop”
radiated magnetic fields and the transformer or inductor
leakage fields.
The capacitor on INTV
high transient currents to the bottom gates and to re-
charge the boost capacitor. This capacitor should be a
4.7 F tantalum capacitor placed as close as possible to the
INTV
MOSFET gates exceeds 1A. The PGND pin of the IC,
connected to this capacitor, should connect directly to the
lower plates of the output capacitors to minimize the AC
ripple on the INTV
TYPICAL APPLICATIONS
221k, 1%
10k
10k
CC
1000pF
220pF
470pF
220pF
0.1 F
0.1 F
and PGND pins of the IC. Peak current driving the
56pF
1000pF
392k, 1%
56pF
1000pF
10
CC
U
1N4148
100
IC power supply.
CC
INTV
1k
1N4148
INFORMATION
acts as a reservoir to supply the
CC
U
1000pF
1000pF
22pF
100
10
POR2
LBO
LBI
U
10
11
12
13
14
W
1
2
3
4
5
6
7
8
9
SENSE
SENSE
V
I
POR2
C
SGND
LBI
LBO
SFB1
I
V
SENSE
SENSE
TH1
TH2
PROG1
OSC
OSENSE2
LTC1438
+
+
–
–
LTC1438 5V/3A, 3.3V/3.5A Regulator
2
1
1
2
RUN/SS1
RUN/SS2
BOOST 1
BOOST 2
EXTV
INTV
U
PGND
TGL1
TGL2
SW1
SW2
BG1
BG2
V
CC
CC
IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
OUT1
0.1 F
The previous instructions will yield a PC layout which has
three separate ground regions returning separately to the
bottom plates of the output capacitors: a signal ground, a
MOSFET gate/INTV
input capacitors, Schottky diode and synchronous
MOSFET. In practice, this may produce a long power
ground path from the input and output capacitors. A long,
low resistance path between the input and output capaci-
tor power grounds will not upset the operation of the
switching controllers as long as the signal and power
grounds from the IC pins does not “tap in” along this path.
10
0.1 F
+
0.1 F
CMDSH-3
CMDSH-3
4.7 F 16V
+
22 F
35V
V
5V, 3A/3.3V, 3.5A
M1 TO M4: Si4412DY
INPUT CAPACITORS ARE AVX-TPS SERIES
OUTPUT CAPACITORS ARE AVX-TPSV LEVEL II SERIES
IN
5.2V TO 28V: SWITCHING FREQUENCY = 180kHz
M1
M2
M4
M3
+
CC
CDRH125-100MC
CDRH125-100MC
ground and the ground from the
SUMIDA
22 F
35V
SUMIDA
MBRS140T3
LTC1438/LTC1439
10 H
MBRS140T3
10 H
0.033
+
0.033
+
220 F
10V
22 F
35V
+
+
220 F
10V
22 F
35V
1438 TA01
25
V
5.2V
TO
28V
V
5V
3A
GND
V
3.3V
3.5A
IN
OUT1
OUT2