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| 型号： | MAX17100ETM+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/35页 |
| 文件大小： | 0K |
| 描述： | IC REG BOOST INT-SWITCH 48-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | LCD 电视机/监控器 |
| 电源电压： | 2.5 V ~ 6 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-WFQFN 裸露焊盘 |
| 供应商设备封装： | 48-TQFN-EP（6x6） |
| 包装： | 带卷 (TR) |
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Internal-Switch Boost Regulator with Integrated Scan
Driver, VCOM Calibrator, and Op Amp for TFT LCDs
×η
V RIPPLE(C ) ≈
I MAIN V MAIN -V IN
× f
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:
I MAIN(MAX) × V MAIN
I IN(DC,MAX) =
V IN(MIN) MIN
Output-Capacitor Selection
The total output voltage ripple has two components: the
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):
V RIPPLE = V RIPPLE(C ) +V R IPPLE(ESR)
( )
C OUT V MAIN OSC
Calculate the ripple current at that operating point and
the peak current required for the inductor:
and
V RIPPLE(ESR ) ≈ I PEAK × R ESR(CO U T)
I RIPPLE =
V IN(MIN) × (V MAIN - V IN(MIN)
L × V MAIN × f OSC
where I PEAK is the peak inductor current (see the
Inductor Selection section). For ceramic capacitors, the
output voltage ripple is typically dominated by
I PEAK IN(DC,MAX) + RIPPLE
I
=I
2
The inductor ’s saturation current rating and the
MAX17100 ’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 14V output and
a typical input voltage of 5V. Choosing an LIR of 0.55 and
estimating efficiency of 85% at this operating point:
V RIPPLE(C) . The voltage rating and temperature charac-
teristics of the output capacitor must also be considered.
Input-Capacitor Selection
The input capacitor (C IN ) reduces the current peaks
drawn from the input supply and reduces noise injec-
tion into the IC. Two 10μF ceramic capacitors are used
in the typical applications circuit (Figure 2) because of
the high source impedance seen in typical lab setups.
Actual applications usually have much lower source
impedance since the step-up regulator often runs
directly from the output of another regulated supply.
Typically, C IN can be reduced below the values used in
5V 2
)( ) ≈ 3 . 0 μ H
L=(
14V
) (
14 V ? 5 V 0.85
0 . 5 A × 1 . 2 MHz 0.55
the typical applications circuit. Ensure a low-noise sup-
ply at IN by using adequate C IN .
Rectifier Diode
Using the circuit’s minimum input voltage (4.5V) and
estimating efficiency of 80% at that operating point:
The MAX17100’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommend-
ed for most applications because of their fast recovery
I IN(DC,MAX) =
0.5A × 14 V
4.5V × 0 . 8
= 1 . 94 A
time and low forward voltage. In general, a 3A Schottky
diode complements the internal MOSFET well.
Output-Voltage Selection
The ripple current and the peak current are:
The output voltage of the main step-up regulator can be
adjusted by connecting a resistive voltage-divider from
I RIPPLE =
4 . 5 V × (14V - 4.5V)
3 . 0 μ H × 14 V × 1 . 2 MHz
= 0 . 848 A
the output (V MAIN ) to AGND with the center tap con-
nected to FB (see Figure 2). Select R2 in the 10k ? to
50k ? range. Calculate R1 with the following equation:
I PEAK = 1.94A +
0.848A
2
≈ 2 . 36 A
R1 = R2 × (
V MAIN
V FB
-1)
where V FB , the step-up regulator’s feedback set point,
is 1.233V. Place R1 and R2 close to the IC.
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| MAX17101ETJ+T | 功能描述:DC/DC 开关控制器 Dual PWM Step-Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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