LTC3831EGN#TR Linear Technology, LTC3831EGN#TR Datasheet - Page 14

• Manufacturer Part Number: LTC3831EGN#TR
• Description: IC SW REG CONTROLLR SYNC 16-SSOP
• Manufacturer: Linear Technology

Specifications of LTC3831EGN#TR

• Applications: Controller, DDR
• Voltage - Input: 3 ~ 8 V
• Number Of Outputs: 1
• Voltage - Output: 1.27 ~ 4 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC3831EGNTR

APPLICATIONS INFORMATION
LTC3831
output might allow no more than 3% effi ciency loss at full
load for each MOSFET. Assuming roughly 90% effi ciency
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 0.21W
per device or less; large TO-220 packages and heat sinks
are not necessarily required in high effi ciency applications.
Siliconix Si4410DY or International Rectifi er IRF7413
(both in SO-8) or Siliconix SUD50N03-10 (TO-252) or ON
Semiconductor MTD20N03HDL (DPAK) are small footprint
surface mount devices with R
at 5V of V
Table 1. Recommended MOSFETs for LTC3831 Applications
PARTS
Siliconix SUD50N03-10
T0-252
Siliconix Si4410DY
SO-8
ON Semiconductor MTD20N03DHL
D PAK
Fairchild FDS6670A
SO-8
Fairchild FDS6680
SO-8
ON Semiconductor MTB75N03HDL
DS 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
(1.25V)(5A/0.9)(0.03) = 0.21W per FET
R
R
DS(ON)Q1
DS(ON)Q2
GS
that work well in LTC3831 circuits. Using a
=
=
(2.5V) • (0.21W)
(2.5V – 1.25V)(5A)
DS(ON)
(1.25V)(5A)
(2.5V) • (0.21W)
of:
DS(ON)
2
DS(ON)
= 0.017Ω
MAX
AT 25ºC (mΩ)
2
values suggest large
R
values below 0.03Ω
= 0.017Ω
DS(ON)
value of:
19
20
35
10
19
28
37
8
9
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
15 at 25°C
10 at 25°C
20 at 25°C
13 at 25°C
75 at 25°C
64 at 25°C
50 at 25°C
35 at 25°C
8 at 70°C
higher P
decreases the MOSFET cost and the circuit effi ciency and
increases the MOSFET heat sink requirements.
Table 1 highlights a variety of power MOSFETs that are
for use in LTC3831 applications.
Inductor Selection
The inductor is often the largest component in an LTC3831
design and must be chosen carefully. Choose the inductor
value and type based on output slew rate requirements.
The maximum rate of rise of inductor current is set by
the inductor’s value, the input-to-output voltage differen-
tial and the LTC3831’s maximum duty cycle. In a typical
2.5V input 1.25V output application, the maximum rise
time will be:
where L
compensation, the combination of the inductor and output
DC
MAX
O
MAX
is the inductor value in μH. With proper frequency
• (V
L
TYPICAL INPUT
CAPACITANCE
value in the R
O
IN
C
ISS
3200
2700
3200
2070
4025
1600
3300
1750
– V
880
(pF)
OUT
)
=
1.138
DS(ON)
L
O
θ
calculations generally
JC
μs
A
1.67
2.08
1.8
1.4
(°C/W)
25
25
1
1
T
JMAX
175
150
150
150
150
150
175
175
150
(°C)
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