- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄44988 > LTC1871EMS#PBF-1 (LINEAR TECHNOLOGY CORP) SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 PDF資料下載
參數(shù)資料
| 型號： | LTC1871EMS#PBF-1 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 19/36頁 |
| 文件大?。?/td> | 354K |
| 代理商： | LTC1871EMS#PBF-1 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁當(dāng)前第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁
26
LTC1871-1
18711fa
are limited to 30V or less. Check the switching waveforms
directly across the drain and source terminals of the power
MOSFET to ensure the VDS remains below the maximum
rating for the device.
During the MOSFET’s on-time, the control circuit limits the
maximum voltage drop across the power MOSFET to
about 150mV (at low duty cycle). The peak inductor
current is therefore limited to 150mV/RDS(ON). The rela-
tionship between the maximum load current, duty cycle
and the RDS(ON) of the power MOSFET is:
R
V
I
DS ON
SENSE MAX
OMAX
T
()
≤
+
1
2
1
χ
ρ
V
VV
V
OD
IN MIN
+
+
()
1
The VSENSE(MAX) term is typically 150mV at low duty cycle
and is reduced to about 100mV at a duty cycle of 92% due
to slope compensation, as shown in Figure 8. The constant
‘χ’ in the denominator represents the ripple current in the
inductors relative to their maximum current. For example,
if 30% ripple current is chosen, then χ = 0.30. The
ρT term
accounts for the temperature coefficient of the RDS(ON) of
the MOSFET, which is typically 0.4%/
°C. Figure 9 illus-
trates the variation of normalized RDS(ON) over tempera-
ture for a typical power MOSFET.
Another method of choosing which power MOSFET to use
is to check what the maximum output current is for a given
RDS(ON) since MOSFET on-resistances are available in
discrete values.
I
V
R
OMAX
SENSE MAX
DS ON
T
()
≤
+
1
2
1
χ
ρ
V
VV
V
OD
IN MIN
+
+
()
1
Calculating Power MOSFET Switching and Conduction
Losses and Junction Temperatures
In order to calculate the junction temperature of the power
MOSFET, the power dissipated by the device must be
known. This power dissipation is a function of the duty
cycle, the load current and the junction temperature itself.
As a result, some iterative calculation is normally required
to determine a reasonably accurate value. Since the con-
troller is using the MOSFET as both a switching and a
sensing element, care should be taken to ensure that the
converter is capable of delivering the required load current
over all operating conditions (load, line and temperature)
and for the worst-case specifications for VSENSE(MAX) and
the RDS(ON) of the MOSFET listed in the manufacturer’s
data sheet.
The power dissipated by the MOSFET in a SEPIC converter is:
PI
D
RD
FET
O MAX
MAX
DS ON
MAX
=
()
(
)
–
1
2
–
()
.
()
ρT
IN MIN
O
O MAX
MAX
kV
V
I
D
++
()185
1
Cf
RSS
The first term in the equation above represents the I2R
losses in the device and the second term, the switching
losses. The constant k = 1.7 is an empirical factor inversely
related to the gate drive current and has the dimension of
1/current.
From a known power dissipated in the power MOSFET, its
junction temperature can be obtained using the following
formula:
TJ = TA + PFET RTH(JA)
The RTH(JA) to be used in this equation normally includes
the RTH(JC) for the device plus the thermal resistance from
the board to the ambient temperature in the enclosure.
This value of TJ can then be used to check the original
assumption for the junction temperature in the iterative
calculation process.
SEPIC Converter: Output Diode Selection
To maximize efficiency, a fast-switching diode with low
forward drop and low reverse leakage is desired. The
output diode in a SEPIC converter conducts current during
the switch off-time. The peak reverse voltage that the
diode must withstand is equal to VIN(MAX) + VO. The
average forward current in normal operation is equal to the
output current, and the peak current is equal to:
II
VV
V
DPEAK
O MAX
OD
IN MIN
()
(
)
()
=+
+
1
2
1
χ
The power dissipated by the diode is:
PD = IO(MAX) VD
APPLICATIO S I FOR ATIO
WU
UU
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1871EMS#TR-1 | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| LTC1871IMS#TRPBF-1 | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| LTC1871HMS#TR | 0.05 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| LTC1871HMS | 0.05 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| LTC1877IMS8#TRPBF | 1.5 A SWITCHING REGULATOR, 605 kHz SWITCHING FREQ-MAX, PDSO8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1871HMS#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871HMS#TRPBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871HMSPBF | 制造商:Linear Technology 功能描述:PWM Controller Current Mode MSOP10 |
| LTC1871IMS | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871IMS#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。