LTC3831EGN-1#PBF Linear Technology, LTC3831EGN-1#PBF Datasheet - Page 14

• Manufacturer Part Number: LTC3831EGN-1#PBF
• Description: IC CTRLR SW REG SYNC DDR 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC3831EGN-1#PBF

• Applications: Controller, DDR
• Voltage - Input: 3 ~ 8 V
• Number Of Outputs: 1
• Voltage - Output: 0.4 ~ 4 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC3831-1
APPLICATIO S I FOR ATIO
efficiency circuit designed for 1.5V input and 0.75V at 5A
output might allow no more than 3% efficiency loss at full
load for each MOSFET. Assuming roughly 90% efficiency
at this current level, this gives a P
and a required R
Note that while the required R
MOSFETs, the power dissipation numbers are only 0.125W
per device or less; large TO-220 packages and heat sinks
are not necessarily required in high efficiency applications.
Siliconix Si4410DY or International Rectifier IRF7413 (both
in SO-8) or Siliconix SUD50N03-10 (TO-252) or ON Semi-
conductor MTD20N03HDL (DPAK) are small footprint
surface mount devices with R
5V of V
higher P
Table 1. Recommended MOSFETs for LTC3831-1 Applications
PARTS
Siliconix SUD50N03-10
TO-252
Siliconix Si4410DY
SO-8
ON Semiconductor MTD20N03HDL
D PAK
Fairchild FDS6670A
S0-8
Fairchild FDS6680
SO-8
ON Semiconductor MTB75N03HDL
DD PAK
IR IRL3103S
DD PAK
IR IRLZ44
TO-220
Fuji 2SK1388
TO-220
Note: Please refer to the manufacturer’s data sheet for testing conditions and detailed information.
14
(0.75V)(5A/0.9)(0.03) = 0.125W per FET
R
R
DS ON Q
DS ON Q
(
(
GS
MAX
)
)
that work well in LTC3831-1 circuits. Using a
1
2
value in the R
( .
( .
1 5
DS(ON)
1 5
( .
( .
1 5
0 75
U
V
V
) • ( .
V
– .
) • ( .
of:
V
0 75
0 125
)(
U
0 125
5
DS(ON)
A
DS(ON)
V
DS(ON)
)
)(
2
W
AT 25 C (m )
5
W
)
A
MAX
calculations generally
R
W
)
values below 0.03 at
)
DS(ON)
2
values suggest large
19
20
35
10
19
28
37
0 01
8
9
.
value of:
0 01
.
U
RATED CURRENT (A)
11.5 at 25 C
10 at 100 C
16 at 100 C
59 at 100 C
45 at 100 C
36 at 100 C
50 at 25 C
35 at 25 C
15 at 25 C
10 at 25 C
20 at 25 C
13 at 25 C
75 at 25 C
64 at 25 C
8 at 70 C
decreases the MOSFET cost and the circuit efficiency and
increases the MOSFET heat sink requirements.
Table 1 highlights a variety of power MOSFETs that are for
use in LTC3831-1 applications.
Inductor Selection
The inductor is often the largest component in an
LTC3831-1 design and must be chosen carefully. Choose
the inductor value and type based on output slew rate re-
quirements. The maximum rate of rise of inductor current
is set by the inductor’s value, the input-to-output voltage
differential and the LTC3831-1’s maximum duty cycle. In
a typical 1.5V input 0.75V output application, the maximum
rise time will be:
where L
quency compensation, the combination of the inductor
and output capacitor values determine the transient recov-
ery time. In general, a smaller value inductor improves
transient response at the expense of ripple and inductor
core saturation rating. A 1 H inductor has a 0.713A/ s rise
DC
MAX
O
is the inductor value in H. With proper fre-
• (
TYPICAL INPUT
CAPACITANCE
L
V
O
IN
C
ISS
3200
2700
3200
2070
4025
1600
3300
1750
880
–
(pF)
V
OUT
)
. 0 713
L
O
JC
1.67
2.08
1.8
1.4
( C/W)
25
25
1
1
A
s
T
JMAX
175
150
150
150
150
150
175
175
150
( C)
38311f