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參數(shù)資料
| 型號： | LTC1708EG-PG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Dual Adjustable 5-Bit VID High Efficiency, 2-Phase Current Mode Synchronous Buck Regulator Controller |
| 中文描述： | 3 A DUAL SWITCHING CONTROLLER, 310 kHz SWITCHING FREQ-MAX, PDSO36 |
| 封裝： | 0.209 INCH, PLASTIC, SSOP-36 |
| 文件頁數(shù)： | 26/32頁 |
| 文件大?。?/td> | 358K |
| 代理商： | LTC1708EG-PG |
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26
LTC1708-PG
APPLICATIU
Design Example
As a design example for one channel, assume V
IN
=
12V(nominal), V
IN
= 22V(max), V
OUT
= 1.6V, I
MAX
= 14A,
and f = 300kHz, R
SENSE
can immediately be calculated:
R
SENSE
= 50mV/14A
≈
0.0035
→
0.003
Tie the FREQSET pin to the INTV
CC
pin for 300kHz opera-
tion, or use a resistive divider from INTV
CC
according to
Figure 5 to reduce the operating frequency.
Assume a 1
μ
H inductor and check the actual value of the
ripple current. The following equation is used:
W
U
U
I
V
( )( )
f L
V
V
L
OUT
OUT
IN
=
–
1
The highest value of the ripple current occurs at the
maximum input voltage:
I
V
(
kHz
H
V
V
A
L
=
μ
=
1 6
.
300
1
1
1 6
22
4 95
.
)
–
.
The ripple current is 35% of maximum output current.
Increasing the ripple current will also help ensure that the
minimum on-time of 200ns is not violated. The minimum
on-time occurs at maximum V
IN
:
t
V
V
f
V
V
kHz
ns
ON MIN
(
OUT
IN MAX
(
)
)
.
(
)
=
=
=
1 6
22 300
242
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 pins current.
R
k
V
V
V
–1 6
V
0 8
.
K
V
V
k
MAX
(
OUT
1
24
0 8
.
2 4
.
24
2 4
.
24
)
–
=
=
=
Choosing 1% resistors; R1 = R2 = 20k yields an output
voltage of 1.600V. If the VID section of the LTC1708-PG is
used, R1 will range from a value of 6.6k to 64k. If the forced
continuous mode is not selected and the programmed
voltage is less than 1.4V with no external load, it is
necessary to preload the output in order to prevent the
current comparator input bias current from causing the
output voltage to rise above the designed level. A 16k
preload resistor will prevent this from happening for all
programmed output voltages down to the minimum 0.925V
level.
The power dissipation on the topside MOSFET can be
easily estimated. Choosing a International Rectifier IRF7811
results in; R
DS(ON)
= 0.011
, C
RSS
= 240pF. At maximum
input voltage with T(estimated) = 50
°
C:
P
V
V
C
C
)(
V
A
pF
kHz
W
MAIN
=
( )
)
+
+
(
°
)(
°
[
]
(
) (
)
=
1 6
22
14
1
0 005 50
25
0 011
.
1 7 22
.
14
240
300
1 0
.
2
2
.
)(
–
)
A short-circuit to ground will result in a folded back current
of:
I
mV
ns
μ
1
V
H
A
SC
=
+
=
25
0 003
.
1
2
200
22
(
12 7
)
.
with a typical value of R
DS(ON)
and
δ
= (0.005/
°
C)(20) =
0.1. The resulting power dissipated in the bottom MOSFET
is:
(
=
1 23
.
P
V
V
V
A
W
SYNC
=
) ( )
(
)
22
22
12 7
1 1 0 0075
.
.
2
–1 6
.
which is similar to full-load conditions.
C
IN
is chosen for an RMS current rating of at least 5A at
temperature assuming only this channel is on. C
OUT
is
chosen with an ESR of 0.01
for low output ripple. The
output ripple in continuous mode will be highest at the
maximum input voltage. The output voltage ripple due to
ESR is approximately:
V
ORIPPLE
= R
ESR(
IL)
= 0.01
(4.95A) = 50mV
P–P
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1708EG-PG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1708EG-PG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1708EG-PG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1709EG | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1709EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
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