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| 型号： | ISL9443IRZ-T |
| 厂商： | Intersil |
| 文件页数： | 20/23页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 6,000 |
| PWM 型： | 电流模式 |
| 输出数： | 3 |
| 频率 - 最大： | 1.32MHz |
| 电源电压： | 4.5 V ~ 26 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | * |
| 包装： | * |
ISL9443
General PowerPAD Design Considerations
The following is an example of how to use vias to remove heat
form the IC.
Output Inductor Selection
The PWM converters require output inductors. The output
inductor is selected to meet the output voltage ripple
requirements. The inductor value determines the converter’s
ripple current and the ripple voltage is a function of the ripple
current and the output capacitor(s) ESR. The ripple voltage
expression is given in the capacitor selection section and the
ripple current is approximated by Equation 14:
( V IN – V OUT ) ( V OUT )
Δ I L = ---------------------------------------------------
( f S ) ( L ) ( V IN )
(EQ. 14)
Output Capacitor Selection
The output capacitors for each output have unique requirements.
( L O ) ( I TRAN )
2 ( V IN – V O ) ( DV OUT )
( I O ) ( r DS ( ON ) ) ( V OUT )
( I O ) ( V IN ) ( t SW ) ( F SW )
V IN
( I O ) ( r DS ( ON ) ) ( V IN – V OUT )
P LOWER = ------------------------------------------------------------------------
V IN
V RIPPLE = Δ I L ( ESR )
FIGURE 23. PCB VIA PATTERN
It is recommended to fill the thermal pad area with vias. A typical
via array fills the thermal pad foot print such that their centers
are 3x the radius apart from each other. Keep the vias small but
not so small that their inside diameter prevents solder wicking
through during reflow.
Connect all vias to the ground plane. It is important the vias have
a low thermal resistance for efficient heat transfer. It is
important to have a complete connection of the plated-through
hole to each plane.
Component Selection Guideline
MOSFET Considerations
The logic level MOSFETs are chosen for optimum efficiency given
the potentially wide input voltage range and output power
requirements. Two N-Channel MOSFETs are used in each of the
synchronous-rectified buck converters for the 3 PWM outputs.
These MOSFETs should be selected based upon r DS(ON) , gate
supply requirements, and thermal management considerations.
The power dissipation includes two loss components; conduction
loss and switching loss. These losses are distributed between the
upper and lower MOSFETs according to duty cycle (see the
following equations). The conduction losses are the main
component of power dissipation for the lower MOSFETs. Only the
upper MOSFET has significant switching losses, since the lower
device turns on and off into near zero voltage. The equations
assume linear voltage-current transitions and do not model
power loss due to the reverse-recovery of the lower MOSFET’s
body diode.
2
2
P UPPER = ---------------------------------------------------------- + --------------------------------------------------------
(EQ. 12)
2
(EQ. 13)
A large gate-charge increases the switching time, t SW , which
increases the upper MOSFETs’ switching losses. Ensure that both
MOSFETs are within their maximum junction temperature at high
ambient temperature by calculating the temperature rise
according to package thermal-resistance specifications.
20
In general, the output capacitors should be selected to meet the
dynamic regulation requirements including ripple voltage and
load transients. Selection of output capacitors is also dependent
on the output inductor, so some inductor analysis is required to
select the output capacitors.
One of the parameters limiting the converter’s response to a load
transient is the time required for the inductor current to slew to
its new level. The ISL9443 will provide either 0% or maximum
duty cycle in response to a load transient.
The response time is the time interval required to slew the
inductor current from an initial current value to the load current
level. During this interval the difference between the inductor
current and the transient current level must be supplied by the
output capacitor(s). Minimizing the response time can minimize
the output capacitance required. Also, if the load transient rise
time is slower than the inductor response time, as in a hard drive
or CD drive, it reduces the requirement on the output capacitor.
The maximum capacitor value required to provide the full, rising
step, transient load current during the response time of the
inductor is:
2
C OUT = ----------------------------------------------------- (EQ. 15)
Where C OUT is the output capacitor(s) required, L O is the output
inductor, I TRAN is the transient load current step, V IN is the input
voltage, V O is output voltage, and DV OUT is the drop in output
voltage allowed during the load transient.
High frequency capacitors initially supply the transient current
and slow the load rate-of-change seen by the bulk capacitors. The
bulk filter capacitor values are generally determined by the ESR
(Equivalent Series Resistance) and voltage rating requirements
as well as actual capacitance requirements.
The output voltage ripple is due to the inductor ripple current and
the ESR of the output capacitors as defined by:
(EQ. 16)
as close to the power pins of the load as physically possible. Be
careful not to add inductance in the circuit board wiring that
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load circuitry
for specific decoupling requirements.
FN7663.1
February 24, 2012
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL9443IRZ-T7A | 功能描述:软开关 PWM 控制器 ISL9443 TRIPLE STEP CONTRLR IMVP-6. 32LD RoHS:否 制造商:Fairchild Semiconductor 输出端数量: 输出电流: 开关频率: 工作电源电压:30 V 电源电流: 最大工作温度:+ 105 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
| ISL9443IRZ-T7AS2750 | 制造商:Intersil Corporation 功能描述:ISL9443 TRIPLE, STEP- DOWN PWM CONTROLLER IMVP-6. 32 LD MLFP - Tape and Reel |
| ISL9443IRZ-TS2750 | 制造商:Intersil Corporation 功能描述:PB FREE. ISL9443 TRIPLE, STEP- DOWN PWM CONTROLLER IMVP-6. 3 - Tape and Reel |
| ISL9444CRZ | 制造商:Intersil Corporation 功能描述:PB FREE. ISL9444 TRIPLE, STEP- DOWN PWM CONTROLLER IMVP-6. 4 - Rail/Tube 制造商:Intersil Corporation 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN 制造商:Intersil 功能描述:Pb Free. ISL9444 Tri ple, Step- Down PWM |
| ISL9444CRZ-T | 制造商:Intersil Corporation 功能描述:PB FREE. ISL9444 TRIPLE, STEP- DOWN PWM CONTROLLER IMVP-6. 4 - Tape and Reel 制造商:Intersil Corporation 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN 制造商:Intersil 功能描述:Pb Free. ISL9444 Tri ple, Step- Down PWM |
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