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參數(shù)資料
| 型號(hào)： | ISL6741 |
| 廠商： | Intersil Corporation |
| 英文描述： | Flexible Double Ended Voltage and Current Mode PWM Controllers(靈活的雙端電壓和電流模式PWM控制器) |
| 中文描述： | 靈活的雙端電壓和電流模式PWM控制器（靈活的雙端電壓和電流模式的PWM控制器） |
| 文件頁數(shù)： | 19/29頁 |
| 文件大小： | 635K |
| 代理商： | ISL6741 |
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19
FN9111.4
July 13, 2007
appropriate for this frequency. A value of 220pF was
selected.
To obtain the proper value for R
TD
, Equation 3 is used.
Since there is a 10ns propagation delay in the oscillator
circuit, it must be included in the calculation. The value of
R
TD
selected is 8.06k
Ω
.
A similar procedure is used to determine the value of R
TC
using
Equation 2. The value of R
TC
selected is the series
combination of 17.4k
Ω
and 1.27k
Ω
. See section “Overcurrent
Component Selection” on page 19 for further explanation.
Output Filter Design
The output filter inductor and capacitor selection is simple
and straightforward. Under steady state operating conditions
the voltage across the inductor is very small due to the large
duty cycle. Voltage is applied across the inductor only during
the switch transition time, about 45ns in this application.
Ignoring the voltage drop across the SR FETs, the voltage
across the inductor during the ON time with V
IN
= 48V is
where
V
L
is the inductor voltage
V
S
is the voltage across the secondary winding
V
OUT
is the output voltage
If we allow a current ramp,
Δ
I, of 5% of the rated output
current, the minimum inductance required is
An inductor value of 1.4
μ
H, rated for 18A was selected.
With a maximum input voltage of 53V, the maximum output
voltage is about 13V. The closest higher voltage rated
capacitor is 16V. Under steady state operating conditions the
ripple current in the capacitor is small, so it would seem
appropriate to have a low ripple current rated capacitor.
However, a high rated ripple current capacitor was selected
based on the nature of the intended load, multiple buck
regulators. To minimize the output impedance of the filter, a
Sanyo OSCON 16SH150M capacitor in parallel with a 22
μ
F
ceramic capacitor were selected.
Overcurrent Component Selection
There are two circuit areas to consider when selecting the
components for overcurrent protection, current limit and
short circuit shutdown. The current limit threshold is fixed at
0.6V while the short circuit threshold is set to a fraction of the
duty cycle the designer wishes to define as a short circuit.
The current level that corresponds to the overcurrent
threshold must be chosen to allow for the dynamic behavior
of an open loop converter. In particular, the low inductor
ripple current under steady state operation increases
significantly as the duty cycle decreases.
Figures 8 and 9 show the behavior of the inductor ripple
under steady state and overcurrent conditions. In this
example, the peak current limit is set at 11A. The peak
current limit causes the duty cycle to decrease resulting in a
reduction of the average current through the inductor. The
implication is that the converter can not supply the same
output current in current limit that it can supply under steady
state conditions. The peak current limit setpoint must take
this behavior into consideration. A 3.32
Ω
current sense
resistor was selected for the rectified secondary of current
transformer T2, corresponding to a peak current limit
setpoint of 16.5A.
The short circuit protection involves setting a voltage
between 0 and 2V on the SCSET pin. The applied voltage
divided by 2 is the percent of maximum duty cycle that
corresponds to a short circuit when the peak current limit is
active. A divider from RTC to ground provides an easy
V
L
V
S
V
OUT
–
V
-----------------------------------------------
N
P
1
D
–
(
)
250
≈
=
=
mV
(EQ. 22)
L
V
------------------------
T
≥
----------------------------
1.04
=
=
μ
H
(EQ. 23)
FIGURE 8. STEADY STATE SECONDARY WINDING
VOLTAGE AND INDUCTOR CURRENT
14
13
12
11
10
9
8
0.9950
0.9960
0.9970
0.9980
0.9990
1.000
TIME (ms)
V (L1:1)
I
(L1)
FIGURE 9. SECONDARY WINDING VOLTAGE AND
INDUCTOR CURRENT DURING CURRENT LIMIT
OPERATION
0.986
0.988
0.990
0.992
0.994
1.000
TIME (ms)
0.996
0.998
15
10
5
V (L1:1)
I
(L1)
ISL6740, 1SL6741
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| ISL6845IBZ | Improved Industry Standard Single-Ended Current Mode PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6741IB | 功能描述:電流型 PWM 控制器 CUR PWM MODE CNTRLR 16LD N RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| ISL6741IB-T | 功能描述:IC REG CTRLR PWM CM 16-SOIC 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:100% 電源電壓:8.2 V ~ 30 V 降壓:無 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁面:1316 (CN2011-ZH PDF) |
| ISL6741IBZ | 功能描述:IC REG CTRLR PWM CM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 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:275kHz 占空比:50% 電源電壓:18 V ~ 110 V 降壓:無 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:-40°C ~ 85°C 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) |
| ISL6741IBZ-T | 功能描述:IC REG CTRLR PWM CM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 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:275kHz 占空比:50% 電源電壓:18 V ~ 110 V 降壓:無 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:-40°C ~ 85°C 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) |
| ISL6741IV | 功能描述:IC REG CTRLR PWM CM 16-TSSOP 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:100% 電源電壓:8.2 V ~ 30 V 降壓:無 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁面:1316 (CN2011-ZH PDF) |
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