参数资料
| 型号： | MAX8758ETG+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/20页 |
| 文件大小： | 0K |
| 描述： | IC REG STEP UP 24-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 转换器，TFT，LCD |
| 输入电压： | 1.8 V ~ 5.5 V |
| 输出数： | 1 |
| 输出电压： | 5V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 供应商设备封装： | 24-TQFN-EP（4x4） |
| 包装： | 带卷 (TR) |
Step-Up Regulator with Switch Control
and Operational Amplifier for TFT LCD
In Figure 1’s Typical Operating Circuit , the LCD’s gate-
on and gate-off voltages are generated from two unreg-
ulated charge pumps driven by the step-up regulator’s
LX node. The additional load on LX must therefore be
considered in the inductance calculation. The effective
maximum output current I MAIN(EFF) becomes the sum
of the maximum load current on the step-up regulator’s
output plus the contributions from the positive and neg-
ative charge pumps:
Considering the Typical Operating Circuit , the maxi-
mum load current (I MAIN(MAX) ) is 300mA for the step-
up regulator, 20mA for the two-stage positive charge
pump, and 20mA for the one-stage negative charge
pump. Altogether, the effective maximum output cur-
rent, I MAIN(EFF) is 360mA with an 8.5V output and a
typical input voltage of 3.3V. The switching frequency is
set to 1.2MHz. Choosing an LIR of 0.4 and estimating
efficiency of 85% at this operating point:
L = ?
? 3 . 3 V ?
? 8 . 5 V ?
? ≈ 4 . 2 μ H
× ?
? × ?
I MAIN(EFF) = I MAIN(MAX) + n NEG x I NEG
+ (n POS + 1) x I POS
where I MAIN(MAX) is the maximum output current, n NEG
?
2
? 8 . 5 V ? 3 . 3 V ? ? 0 . 85 ?
? 0 . 36 A × 1 . 2 MHz ? ? 0 . 4 ?
is the number of negative charge-pump stages, n POS is
the number of positive charge-pump stages, I NEG is
the negative charge-pump output current, and I POS is
Using the circuit’s minimum input voltage (3V) and esti-
mating efficiency of 80% at that operating point:
the positive charge-pump output current, assuming the
pump source for I POS is V MAIN .
The required inductance can then be calculated as
I IN ( DC , MAX ) =
0.36 A × 8.5 V
3 V × 0 . 8
≈ 1 . 28 A
follows:
The ripple current and the peak current are:
L = ?
? V MAIN ?
? η TYP ?
? ? V ?
× ?
? × ? ?
?
? V IN ?
?
2
V MAIN IN
? I MAIN ( EFF ) × f OSC ? LIR ?
I RIPPLE =
3 V × ( 8 . 5 V ? 3 V )
4 . 2 μ H × 8 . 5 V × 1 . 2 MHz
≈ 0 . 4 A
where V IN is the typical input voltage and η TYP is the
expected efficiency obtained from the appropriate
curve in the Typical Operating Characteristics.
I PEAK = 1 . 28 A +
0.4 A
2
≈ 1 . 48 A
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 an appropriate curve
in the Typical Operating Characteristics :
The peak-inductor current does not exceed the guaran-
teed minimum value of the LX current limit in the
Electrical Characteristics table.
Step-Up Regulator Output Capacitor Selection
The total output voltage ripple has two components: the
,
I IN ( DCMAX ) =
I MAIN(EFF) × V MAIN
V IN ( MIN ) × η MIN
capacitive ripple caused by the charging and discharg-
ing of the output capacitance, and the ohmic ripple due
to the capacitor’s equivalent series resistance (ESR):
Calculate the ripple current at that operating point and
V RIPPLE = V RIPPLE(C) + V ARIPPLE(ESR)
V IN ( MIN ) × ( V MAIN IN ( MIN )
L × V MAIN OSC
I RIPPLE =
× ? MAIN IN ?
the peak current required for the inductor:
? V
× f
)
and
V RIPPLE ( C ) ≈
I MAIN
C MAIN
? V ? V ?
? V MAIN × f SW ?
I PEAK IN ( DC , MAX ) + RIPPLE
= I
I
2
The inductor’s saturation current rating and the guaran-
teed minimum value of the MAX8758’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.
V RIPPLE(ESR) ≈ I PEAK x R ESR
where I PEAK is the peak inductor current (see the Step-
Up Regulator Inductor Selection section). For ceramic
capacitors, the output voltage ripple is typically dominat-
ed by V RIPPLE(C) . The voltage rating and temperature
characteristics of the output capacitor must also be con-
sidered.
16
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX8759ETI+T | IC CNTRL CCFL BACKLIGHT 28TQFN |
| MAX8760ETL+T | IC CNTRLR QUICK PWM 40-TQFN |
| MAX8761ETG+T | IC REG LINEAR LCD 24-TQFN |
| MAX8764ETP+T | IC CNTRL STP DWN HS 20-TQFN |
| MAX8765AETI+ | IC BATT CHARGER MULTICHEM 28TQFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8758ETJ | 功能描述:LCD 驱动器 Step-Up Regulator 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 |
| MAX8758EVKIT | 功能描述:电源管理IC开发工具 MAX8758 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX8759AETI+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX8759ETI+ | 功能描述:显示驱动器和控制器 SMBus CCFL Backlight Controller RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8759ETI+T | 功能描述:显示驱动器和控制器 SMBus CCFL Backlight Controller RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
发布紧急采购，3分钟左右您将得到回复。