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| 型号： | MAX1518BETJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 18/25页 |
| 文件大小： | 0K |
| 描述： | IC DC-DC CONV TFT-LCD 32-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 应用： | 转换器，TFT，LCD |
| 输入电压： | 2.6 V ~ 6.5 V |
| 输出数： | 1 |
| 输出电压： | 2.6 V ~ 13 V |
| 工作温度： | -40°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
| 包装： | 管件 |
TFT-LCD DC-DC Converter with
Operational Amplifiers
? V IN ? 2 ? V MAIN ? V IN ? ? η TYP ?
? ? I
L = ? ? ? ?
Design Procedure
Main Step-Up Regulator
Inductor Selection
The minimum inductance value, peak current rating,
and series resistance are factors to consider when
selecting the inductor. These factors influence the con-
verter’s efficiency, maximum output load capability,
transient-response time, and output voltage ripple. Size
and cost are also important factors to consider.
? V MAIN ? ? MAIN ( MAX ) × f OSC ? ? LIR ?
Choose an available inductor value from an appropriate
inductor family. Calculate the maximum DC input cur-
rent at the minimum input voltage (V IN(MIN) ) using con-
servation of energy and the expected efficiency at that
operating point ( η MIN ) taken from the appropriate curve
in the Typical Operating Characteristics :
The maximum output current, input voltage, output volt-
age, and switching frequency determine the inductor
value. Very high inductance values minimize the cur-
rent ripple and therefore reduce the peak current,
,
I IN ( DCMAX ) =
I MAIN(MAX ) × V MAIN
V IN ( MIN ) × η MIN
which decreases core losses in the inductor and con-
duction losses in the entire power path. However, large
inductor values also require more energy storage and
Calculate the ripple current at that operating point and
the peak current required for the inductor:
more turns of wire, which increases size and can
increase conduction losses in the inductor. Low induc-
tance values decrease the size but increase the current
I RIPPLE =
V IN ( MIN ) × ( V MAIN ? V IN ( MIN ) )
L × V MAIN × f OSC
I PEAK IN ( DCMAX ) + RIPPLE
= I
2
L = ?
? ≈ 3 . 3 μ H
? 5 V ? 2 ? 13 V ? 5 V ? ? 0 . 85 ?
? 13 V ? ? 0 . 5 A × 1 . 2 MHz ? ? 0 . 5 ?
ripple and peak current. Finding the best inductor
involves choosing the best compromise between circuit
efficiency, inductor size, and cost.
The equations used here include a constant LIR, which
is the ratio of the inductor peak-to-peak ripple current
to the average DC inductor current at the full load cur-
rent. The best trade-off between inductor size and cir-
cuit efficiency for step-up regulators generally has an
LIR between 0.3 and 0.5. However, depending on the
AC characteristics of the inductor core material and
ratio of inductor resistance to other power-path resis-
tances, the best LIR can shift up or down. If the induc-
tor resistance is relatively high, more ripple can be
accepted to reduce the number of turns required and
increase the wire diameter. If the inductor resistance is
relatively low, increasing inductance to lower the peak
current can decrease losses throughout the power
path. If extremely thin high-resistance inductors are
used, as is common for LCD-panel applications, the
I
,
The inductor ’s saturation current rating and the
MAX1518B’s LX current limit (I LIM ) should exceed I PEAK ,
and the inductor’s DC current rating should exceed
I IN(DC,MAX) . For good efficiency, choose an inductor with
less than 0.1 ? series resistance.
Considering the Typical Operating Circuit, the maximum
load current (I MAIN(MAX) ) is 500mA with a 13V output and
a typical input voltage of 5V. Choosing an LIR of 0.5 and
estimating efficiency of 85% at this operating point:
? ? ? ?
Using the circuit’s minimum input voltage (4.5V) and
estimating efficiency of 80% at that operating point:
best LIR can increase to between 0.5 and 1.0.
Once a physical inductor is chosen, higher and lower
values of the inductor should be evaluated for efficien-
,
I IN ( DCMAX ) =
0.5A × 13V
4 . 5 V × 0 . 8
≈ 1 . 8 A
cy improvements in typical operating regions.
The ripple current and the peak current are:
Calculate the approximate inductor value using the typ-
ical input voltage (V IN ), the maximum output current
(I MAIN(MAX) ), the expected efficiency ( η TYP ) taken from
I RIPPLE =
4 . 5 V × ( 13 V ? 4 . 5 V )
3 . 3 μ H × 13 V × 1 . 2 MHz
≈ 0 . 74 A
I PEAK = 1 . 8 A + ≈ 2 . 2 A
an appropriate curve in the Typical Operating
Characteristics section, and an estimate of LIR based
on the above discussion:
0 . 74 A
2
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1518BETJ+ | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1518BETJ+T | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1518ETJ | 功能描述:LCD 驱动器 RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1518ETJ+ | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
| MAX1518ETJ+T | 功能描述:LCD 驱动器 TFT-LCD DC-DC Conv w/Op Amps RoHS:否 制造商:Maxim Integrated 数位数量:4.5 片段数量:30 最大时钟频率:19 KHz 工作电源电压:3 V to 3.6 V 最大工作温度:+ 85 C 最小工作温度:- 20 C 封装 / 箱体:PDIP-40 封装:Tube |
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