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| 型号： | MAX8723ETE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 14/18页 |
| 文件大小： | 0K |
| 描述： | IC REG FOR LCD DISPLAY 16-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，LCD |
| 输入电压： | 6 V ~ 13.2 V |
| 输出数： | 1 |
| 输出电压： | 3.3V，2 V ~ 3.6 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WQFN 裸露焊盘 |
| 供应商设备封装： | 16-TQFN-EP（4x4） |
| 包装： | 带卷 (TR) |
Low-Cost, Internal-Switch, Step-Down
Regulator for LCD Displays
Input Capacitors
The input filter capacitors reduce peak currents drawn
from the power source and reduce noise and voltage
ripple on the input caused by the regulator’s switching.
They are usually selected according to input ripple cur-
rent requirements and voltage rating, rather than
capacitance value. The input voltage and load current
determine the RMS input ripple current (I RMS ):
each should be less than 50% of the total peak-to-
peak ripple, then the ESR should be less than 55m ?
and the output capacitance should be more than 1.5μF
to meet the total ripple requirement.
A 22μF capacitor with ESR (including PC board
trace resistance) of 10m ? is selected for the standard
application circuit in Figure 1, which easily meets the
voltage-ripple requirement.
I RMS = I OUT x
V OUT × ( V IN ? V OUT )
V IN
The step-down regulator’s output capacitor and ESR
also affect the voltage undershoot and overshoot when
the load steps up and down abruptly. The undershoot
and overshoot also have two components: the voltage
The worst case is I RMS = 0.5 x I OUT , which occurs at
V IN = 2 x V OUT .
For most applications, ceramic capacitors are used
because of their high ripple current and surge-current
capabilities. For optimal circuit long-term reliability,
choose an input capacitor that exhibits less than +10°C
temperature rise at the RMS input current corresponding
to the maximum load current. If necessary, add multiple
capacitors in parallel to distribute the ripple current.
Output Capacitor Selection
Since the MAX8723’s step-down regulator is internally
compensated, it is stable with any reasonable amount
of output capacitance. However, the actual capaci-
steps caused by ESR, and voltage sag and soar due to
the finite capacitance and inductor slew rate. Use the
following formulas to check if the ESR is low enough
and the output capacitance is large enough to prevent
excessive soar and sag.
The amplitude of the ESR step is a function of the load
step and the ESR of the output capacitor:
V OUT_ESR_STEP = ? I OUT x R ESR_OUT
The amplitude of the capacitive sag is a function of the
load step, the output capacitor value, the inductor
value, the input-to-output voltage differential, and the
maximum duty cycle:
L OUT × ( ? I OUT )
2 × C OUT ( IN ( MIN ) × D MAX OUT
tance and equivalent series resistance (ESR) affect the
regulator ’s output ripple voltage and transient
response. The rest of this section deals with how to
determine the output capacitance and ESR needs
V OUT _ SAG =
× V ? V
2
)
L OUT OUT )
× ( ? I
according to the ripple voltage and load transient
requirements.
The output voltage ripple has two components: varia-
tions in the charge stored in the output capacitor, and
the voltage drop across the capacitor’s ESR caused by
the current into and out of the capacitor:
V OUT _ RIPPLE = V OUT _ RIPPLE ( ESR ) + V OUT _ RIPPLE ( C )
V OUT _ RIPPLE ( ESR ) = I OUT _ RIPPLE × R ESR _ OUT
The amplitude of the capacitive soar is a function of the
load step, the output capacitor value, the inductor
value, and the output voltage:
2
V OUT _ SOAR =
2 × C OUT × V OUT
Given the component values in the 1.5MHz circuit of
Figure 1, during a 2A step-load transient, the voltage
V OUT _ RIPPLE ( C ) =
I OUT
8 × C OUT × f SW
step due to capacitor ESR is negligible. The voltage
sag and soar are 40.2mV and 71.6mV, respectively.
where I OUT _ RIPPLE is defined in the Inductor Selection
section, C OUT is the output capacitance, and
R ESR _ OUT is the ESR of the output capacitor C OUT . In
Figure 1’s circuit, the inductor peak-to-peak ripple cur-
rent is 0.6A. If the voltage-ripple requirement of Figure
1 ’s circuit is ±1% of the 3.3V output, then the total
peak-to-peak ripple voltage should be less than 66mV.
Assuming that the ESR ripple and the capacitive ripple
Rectifier Diode
The MAX8723’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended
for most applications because of their fast recovery time
and low forward voltage. Based on the 2A capability of
the high-side switch, a 2A Schottky diode works well for
most applications. The Schottky diode’s current rating
can be reduced or the diode can be omitted entirely, if
an external synchronous rectifier MOSFET is used.
14
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| MAX8723EVKIT | 功能描述:电源管理IC开发工具 MAX8723 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 |
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| MAX8724ETI+ | 功能描述:电池管理 Multichemistry Battery Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| MAX8724ETI+T | 功能描述:电池管理 Multichemistry Battery Charger RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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