LTC1530C Linear Technology, LTC1530C Datasheet - Page 12

• Manufacturer Part Number: LTC1530C
• Description: High Power Synchronous Switching Regulator Controller
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC1530
P
efficiency or allowable thermal dissipation. A high effi-
ciency buck converter designed for the Pentium II with 5V
input and a 2.8V, 11.2A output might allow no more than
4% 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 1.39W
per device or less — large TO-220 packages and heat
sinks are not necessarily required in high efficiency appli-
cations. Siliconix Si4410DY or International Rectifier
Table 1. Recommended MOSFETs for LTC1530 Applications
MANUFACTURER
Siliconix
Siliconix
ON Semiconductor
Fairchild
ON Semiconductor
IR
IR
Fuji
Note: Please refer to the manufacturer’s data sheet for testing conditions and detailed information.
*Users must consider the power dissipation and thermal effects in the LTC1530 if driving external MOSFETs with high values of input capacitance.
Refer to the PV
12
MAX
MAX
(2.8)(11.2A/0.9)(0.04) = 1.39W per FET
R
R
DS ON Q
DS ON Q
value of:
should be calculated based primarily on required
CC
1
2
Supply Current vs GATE Capacitance in the Typical Performance Characteristics section.
2 8 11 2
DS(ON)
5
5 1 39
V
V
U
MTB75N03HDL*
V
MTD20N03HDL
SUD50N03-10
5 1 39
PART NO.
Si4410DY
IRL3103S
FDS6680
2SK1388
2 8
V
IRLZ44
of:
U
V
W
A
2
DS(ON)
11 2
W
0 020
A
W
2
values suggest large
PACKAGE
TO-252
TO-220
TO-220
D
D
DPAK
SO-8
SO-8
2
2
PAK
PAK
0 025
U
RDS(ON)
AT 25 C
0.0075
0.019
0.020
0.035
0.014
0.028
0.037
0.01
( )
IRF7413 (both in SO-8) or Siliconix SUD50N03 or Motorola
MTD20N03HDL (both in DPAK) are small footprint sur-
face mount devices with R
of V
output voltages, the R
cantly lower than that for Q2. These conditions can often
be met by paralleling two MOSFETs for Q1 and using a
single device for Q2. Using a higher P
R
cost and the circuit efficiency and increases the MOSFET
heat sink requirements.
In most LTC1530 applications, R
current sensing element. MOSFET R
temperature coefficient. Therefore, the LTC1530 I
current is designed with a positive 3300ppm/ C tempera-
ture coefficient. The positive tempco of I
order correction for current limit vs temperature. There-
fore, current limit does not have to be set to an increased
level at room temperature to guarantee a desired output
current at elevated temperatures.
Table 1 highlights a variety of power MOSFETs that are
suitable for use in LTC1530 applications.
RATED CURRENT
DS(ON)
11.5A at 25 C
10A at 100 C
16A at 100 C
59A at 100 C
40A at 100 C
36A at 100 C
15A at 25 C
10A at 25 C
20A at 25 C
75A at 25 C
56A at 25 C
50A at 25 C
35A at 25 C
8A at 75 C
GS
(A)
that work well in LTC1530 circuits. With higher
calculations generally decreases the MOSFET
TYPICAL INPUT
CAPACITANCE
Ciss (pF)
DS(ON)
3200
2700
2070
4025
1600
3300
1750
880
DS(ON)
of Q1 may need to be signifi-
values below 0.03 at 5V
DS(ON)
DS(ON)
( C/W)
1.67
2.08
1.8
1.0
1.8
1.0
—
25
JC
MAX
MAX
is used as the
has a positive
provides first
value in the
MAX
T
( C)
175
150
150
150
150
175
175
150
JMAX
sink