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参数资料
| 型号： | ISL6430 |
| 厂商： | Intersil Corporation |
| 英文描述： | Single Sync Buck PWM Controller for Broadband Gateway Applications |
| 中文描述： | 单同步降压PWM控制器，宽带网关应用 |
| 文件页数： | 11/12页 |
| 文件大小： | 400K |
| 代理商： | ISL6430 |
8
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors.
The bulk capacitor’s ESR will determine the output ripple
voltage and the initial voltage drop after a high slew-rate
transient. An aluminum electrolytic capacitor's ESR value is
related to the case size with lower ESR available in larger
case sizes. However, the equivalent series inductance
(ESL) of these capacitors increases with case size and can
reduce the usefulness of the capacitor to high slew-rate
transient loading. Unfortunately, ESL is not a specified
parameter. Work with your capacitor supplier and measure
the capacitor’s impedance with frequency to select a
suitable component. In most cases, multiple electrolytic
capacitors of small case size perform better than a single
large case capacitor.
Output Inductor Selection
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. The inductor value determines the
converter’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage and current are
approximated by the following equations:
Increasing the value of inductance reduces the ripple current
and voltage. However, the large inductance values reduce
the converter’s response time to a load transient.
One of the parameters limiting the converter’s response to a
load transient is the time required to change the inductor
current. Given a sufficiently fast control loop design, the
ISL6430 will provide either 0% or 100% duty cycle in
response to a load transient. The response time is the time
required to slew the inductor current from an initial current
value to the transient current level. During this interval the
difference between the inductor current and the transient
current level must be supplied by the output capacitor.
Minimizing the response time can minimize the output
capacitance required.
The response time to a transient is different for the
application of load and the removal of load. The following
equations give the approximate response time interval for
application and removal of a transient load:
where: ITRAN is the transient load current step, tRISE is the
response time to the application of load, and tFALL is the
response time to the removal of load. With a +5V input
source, the worst case response time can be either at the
application or removal of load and dependent upon the
output voltage setting. Be sure to check both of these
equations at the minimum and maximum output levels for
the worst case response time.
Input Capacitor Selection
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic
capacitors for high frequency decoupling and bulk capacitors
to supply the current needed each time Q1 turns on. Place
the small ceramic capacitors physically close to the
MOSFETs and between the drain of Q1 and the source of
Q2.
The important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the maximum
input voltage and a voltage rating of 1.5 times is a
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
For a through hole design, several electrolytic capacitors
(Panasonic HFQ series or Nichicon PL series or Sanyo MV-
GX or equivalent) may be needed. For surface mount
designs, solid tantalum capacitors can be used, but caution
must be exercised with regard to the capacitor surge current
rating. These capacitors must be capable of handling the
surge-current at power-up. The TPS series available from
AVX, and the 593D series from Sprague are both surge
current tested.
MOSFET Selection/Considerations
The ISL6430 requires 2 N-Channel power MOSFETs. These
should be selected based upon rDS(ON), gate supply
requirements, and thermal management requirements.
In high-current applications, the MOSFET power dissipation,
package selection and heatsink are the dominant design
factors. The power dissipation includes two loss
components; conduction loss and switching loss. The
conduction losses are the largest component of power
dissipation for both the upper and the lower MOSFETs.
These losses are distributed between the two MOSFETs
according to duty factor (see the equations below). Only the
upper MOSFET has switching losses, since the Schottky
rectifier clamps the switching node before the synchronous
rectifier turns on.
VOUT= I x ESR
I =
V
IN - VOUT
Fs x L
--------------------------------
V
OUT
V
IN
----------------
t
FALL
L
O
I
TRAN
×
V
OUT
-------------------------------
=
t
RISE
L
O
I
TRAN
×
V
IN
V
OUT
–
--------------------------------
=
PUPPER = IO2 x rDS(ON) x D +
1
2
Io x VIN x tSW x Fs
PLOWER = IO2 x rDS(ON) x (1 - D)
Where: D is the duty cycle = VO / VIN,
tSW is the switching interval, and
Fs is the switching frequency.
ISL6430
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| ISL6430CB | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述: |
| ISL6430CR | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述: |
| ISL6431ACB | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ISL6431CB | 功能描述:电压模式 PWM 控制器 For Home Gateways RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| ISL6431CB-T | 功能描述:IC REG CTRLR BUCK PWM VM 8-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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
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