參數(shù)資料
型號: LTC1629C
廠商: Linear Technology Corporation
英文描述: Dual LinCMOS(TM) Timer 14-SOIC
中文描述: 多相,高效率同步降壓型開關(guān)穩(wěn)壓器
文件頁數(shù): 22/28頁
文件大?。?/td> 330K
代理商: LTC1629C
22
LTC1629/LTC1629-PG
Although the LTC1629 has a maximum input voltage of
36V, most applications will be limited to 30V by the
MOSFET BV
DSS
.
Since the output voltage is below 2.4V the output resistive
divider will need to be sized to not only set the output
voltage but also to absorb the sense pin input current for
both channels.
R
k
V
V
1 8
.
V
k
V
1 8
.
V
V
k
MIN
(
OUT
OUT
1
20
2
2 4
.
10
2 4
.
30
)
=
=
=
Choosing 1% resistors: R1=13.2k and R2=16.5k yields an
output voltage of 1.80V and satisfies the above condition.
The power dissipation on the topside MOSFET can be
easily estimated. Using a Siliconix Si4420DY for example;
R
DS(ON)
= 0.013
, C
RSS
= 300pF. At maximum input
voltage with T
j
(estimated) = 110
°
C at an elevated ambient
temperature:
P
V
V
C
C
V
A
pF
kHz
W
MAIN
=
( )
+
(
(
)
°
)(
°
(
)
[
]
+
)
=
) (
)
(
1 8
5 5
.
10
1
0 005 110
.
25
0.
1 7 5 5
.
10
300
310
0 61
.
2
2
.
.
The worst-case power disipated by the synchronous
MOSFET under normal operating conditions at elevated
ambient temperature and estimated 50
°
C junction tem-
perature rise is:
P
V
5 5
.
V
V
A
W
SYNC
=
(
) (
)
(
)
=
5 5
.
1 8
.
10
1 48 0 013
.
1 29
.
2
.
A short-circuit to ground will result in a folded back current
of:
I
mV
ns
V
H
A
SC
=
+
(
)
μ
25
0 005
.
1
2
200
5 5
.
2
5 28
.
APPLICATIU
W
U
U
Figure 8. Automotive Application Protection
V
IN
1629 F08
12V
50A I
PK
RATING
TRANSIENT VOLTAGE
SUPPRESSOR
GENERAL INSTRUMENT
1.5KA24A
LTC1629
Design Example (Using Two Phases)
As a design example, assume V
IN
= 5V (nominal), V
IN
=5.5V
(max), V
OUT
= 1.8V, I
MAX
= 20A, T
A
= 70
°
C and f=300kHz.
The inductance value is chosen first based on a 30% ripple
current assumption. The highest value of ripple current
occurs at the maximum input voltage. Tie the FREQSET pin
to the INTV
CC
pin for 300kHz operation. The minimum
inductance for 30% ripple current is:
L
V
f
I
V
V
V
kHz
H
μ
A
V
V
OUT
( )
OUT
IN
(
)(
)(
)
1
1 8
.
300
1 35
.
30
10
1
1 8
5 5
.
%
.
A 2
μ
H inductor will produce 20% ripple current. The peak
inductor current will be the maximum DC value plus one
half the ripple current, or 11.5A. The minimum on-time
occurs at maximum V
IN
:
t
V
V f
V
V
kHz
s
ON MIN
OUT
)
=
=
(
)(
)
=
μ
1 8
.
5 5
.
300
1 1
.
The R
SENSE
resistors value can be calculated by using the
maximum current sense voltage specification with some
accomodation for tolerances:
R
mV
.
A
SENSE
=
60
11 5
0 005
.
相關(guān)PDF資料
PDF描述
LTC1629C-PG Dual LinCMOS(TM) Timer 14-SOIC
LTC1629CG Dual LinCMOS(TM) Timer 14-SOIC
LTC1629I Dual LinCMOS(TM) Timer 14-PDIP
LTC1629IG RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LTC1629IG-PG RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
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