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参数资料
| 型号： | ISL6721AARZ-T |
| 厂商： | Intersil |
| 文件页数： | 15/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK ISO 16QFN |
| 标准包装： | 6,000 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 100% |
| 电源电压： | 9 V ~ 18 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 105°C |
| 封装/外壳： | 16-VFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
ISL6721A
Pswcap = --- ? Cfet ? Vin ? f sw
The RMS current for the primary winding is 0.72A, for the
3.3V output, 4.23A, for the 1.8V output, 1.69A, and for the
bias winding, 85mA.
To minimize the transformer leakage inductance, the primary
was split into two sections connected in parallel and
positioned such that the other windings were sandwiched
between them. The output windings were configured so that
the 1.8V winding is a tap off of the 3.3V winding. Tapping the
1.8V output requires that the shared portion of the
secondary conduct the combined current of both outputs.
The secondary wire gauge must be selected accordingly.
The determination of current carrying capacity of wire is a
compromise between performance, size, and cost. It is
affected by many design constraints such as operating
frequency (harmonic content of the waveform) and the
winding proximity/geometry. It generally ranges between 250
and 1000 circular mils per ampere. A circular mil is defined
as the area of a circle 0.001” (1 mil) in diameter. As the
frequency of operation increases, the AC resistance of the
wire increases due to skin and proximity effects. Using
heavier gauge wire may not alleviate the problem. Instead
multiple strands of wire in parallel must be used. In some
cases, Litz wire is required.
conduction losses is complicated by the variation of r DS(ON)
with temperature. As junction temperature increases, so
does r DS(ON) , which increases losses and raises the
junction temperature more, and so on. It is possible for the
device to enter a thermal runaway situation without proper
heatsinking. As a general rule of thumb, doubling the +25°C
r DS(ON) specification yields a reasonable value for
estimating the conduction losses at +125°C junction
temperature.
The switching losses have two components: capacitive
switching losses and voltage/current overlap losses. The
capacitive losses occur during turn on of the device and may
be calculated in Equation 19:
1 2
W (EQ. 19)
2
where Cfet is the equivalent output capacitance of the
MOSFET. Device output capacitance is specified on
datasheets as Coss and is non-linear with applied voltage.
To find the equivalent discrete capacitance, Cfet, a charge
model is used. Using a known current source, the time
required to charge the MOSFET drain to the desired
operating voltage is determined and the equivalent
capacitance may be calculated in Equation 20:
Ichg ? t
The winding configuration selected is:
Cfet = --------------------
V
F
(EQ. 20)
Primary #1: 40T, 2 #30 bifilar
The other component of the switching loss is due to the
Secondary: 5T, 0.003” (3 mil) copper foil tapped at 3T
Bias: 17T #32
Primary #2: 40T, 2 #30 bifilar
The internal spacing and insulation system was designed for
1500VDC dielectric withstand rating between the primary
and secondary windings.
overlap of voltage and current during the switching
transition. A switching transition occurs when the MOSFET
is in the process of either turning on or off. Since the load is
inductive, there is no overlap of voltage and current during
the turn on transition, so only the turn off transition is of
significance. The power dissipation may be estimated using
Equation 21:
P sw ≈ --- ? I PPK ? V IN ? t OL ? f sw
Power MOSFET Selection
1
x
(EQ. 21)
Selection of the main switching MOSFET requires
consideration of the voltage and current stresses that will be
encountered in the application, the power dissipated by the
device, its size, and its cost.
The input voltage range of the converter is 36VDC to
75VDC. This suggests a MOSFET with a voltage rating of
150V is required due to the flyback voltage likely to be seen
on the primary of the isolation transformer.
The losses associated with MOSFET operation may be
divided into three categories: conduction, switching, and
gate drive.
The conduction losses are due to the MOSFET’s ON
resistance (Equation 18).
where t OL is the duration of the overlap period and x ranges
from about 3 through 6 in typical applications and depends
on where the waveforms intersect. This estimate may predict
higher dissipation than is realized because a portion of the
turn off drain current is attributable to the charging of the
device output capacitance (Coss) and is not dissipative
during this portion of the switching cycle (Figure 6).
Pcond = r DS ( ON ) ? Iprms
2
W
(EQ. 18)
where r DS(ON) is the ON resistance of the MOSFET and
Iprms is the RMS primary current. Determining the
15
FN6797.0
August 23, 2011
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PDF描述 |
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| GSC19DREN-S13 | CONN EDGECARD 38POS .100 EXTEND |
| ISL6721AAVZ-T | IC REG CTRLR PWM CM 16-TSSOP |
| GMC19DREN-S13 | CONN EDGECARD 38POS .100 EXTEND |
| ISL6721AARZ | IC REG CTRLR BST FLYBK ISO 16QFN |
| GSC19DREH-S13 | CONN EDGECARD 38POS .100 EXTEND |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6721AAVZ | 功能描述:IC REG CTRLR PWM CM 16-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL6721AAVZ-T | 功能描述:IC REG CTRLR PWM CM 16-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL6721AB | 功能描述:IC REG CTRLR PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:100% 电源电压:8.2 V ~ 30 V 降压:无 升压:无 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:0°C ~ 70°C 封装/外壳:8-DIP（0.300"，7.62mm） 包装:管件 产品目录页面:1316 (CN2011-ZH PDF) |
| ISL6721AB-T | 功能描述:IC REG CTRLR PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:100% 电源电压:8.2 V ~ 30 V 降压:无 升压:无 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:0°C ~ 70°C 封装/外壳:8-DIP（0.300"，7.62mm） 包装:管件 产品目录页面:1316 (CN2011-ZH PDF) |
| ISL6721ABZ | 功能描述:电流型 PWM 控制器 FLEX SNG ENDED CUR MODE PWM CONTRLR RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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