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参数资料
| 型号： | MAX8784ETL+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/24页 |
| 文件大小： | 0K |
| 描述： | IC REG STP UP W/AMP 40-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 应用： | LCD 电视机/监控器 |
| 电源电压： | 4 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 40-WFQFN 裸露焊盘 |
| 供应商设备封装： | 40-TQFN-EP（5x5） |
| 包装： | 管件 |
Step-Up Regulator, Internal Charge Pumps, Switch
Control, and Operational Amplifier for TFT LCDs
Output-Capacitor Selection
The total output-voltage ripple has two components: the
capacitive ripple caused by the charging and dis-
charging of the output capacitance, and the ohmic ripple
due to the capacitor’s equivalent series resistance (ESR):
V AVDD _ RIPPLE = V AVDD _ RIPPLE ( C ) + V AVDD _ RIPPLE ( ESR )
Loop Compensation
Choose R COMP (R9 in Figure 1) to set the high-frequen-
cy integrator gain for fast transient response. Choose
C COMP (C11 in Figure 1) to set the integrator zero to
maintain loop stability.
For low-ESR output capacitors, use the following equa-
tions to obtain stable performance and good transient
C AVDDT ? V AVDD × f SW ?
V AVDD _ RIPPLE ( C ) ≈
I AVDD ? V AVDD ? V IN ?
? ?
response:
R COMP ≈
251 × V IN × V AVDD × C AVDD
L I × I AVDD ( MAX )
and:
V AVDD _ RIPPLE ( ESR ) ≈ I AVDD _ PEAK × R ESR _ AVDD
C COMP ≈
V AVDD × C AVDD
10 × I AVDD ( MAX ) × R COMP
where I AVDD _ PEAK is the peak inductor current (see the
Inductor Selection section). For ceramic capacitors, the
output-voltage ripple is typically dominated by
V AVDD _ RIPPLE(C) . The voltage rating and temperature
characteristics of the output capacitor must also be
considered.
Input-Capacitor Selection
The input capacitor reduces the current peaks drawn
from the input supply and reduces noise injection into
the IC. Two 10μF ceramic capacitors are used in the
typical operating circuit (Figure 1) because of the high
source impedance seen in the typical lab setups.
Actual applications usually have much lower source
To further optimize transient response, vary R COMP in
20% steps and C COMP in 50% steps while observing
transient response waveforms.
If additional noise rejection is desired, add a high-fre-
quency pole by placing a 10pF to 47pF capacitor from
COMP to GND.
Charge-Pump Regulators
Selecting the Number of Charge-Pump Stages
For highest efficiency, always choose the lowest num-
ber of charge-pump stages that meet the output
requirement.
The number of negative charge-pump stages is given by:
impedance since the step-up regulator often runs
directly from the output of another regulated supply.
Typically, the input capacitance can be reduced below
the values used in Figure 1.
n NEG =
? V GOFF + V DROPOUT
V SUP ? 2 × V D
Rectifier Diode
The MAX8784’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommend-
ed for most applications because of their fast recovery
time and low forward voltage. In general, a 2A Schottky
diode complements the internal MOSFET well.
Output-Voltage Selection
The output voltage of the step-up regulator can be
adjusted by connecting a resistive voltage-divider from
the output (AVDD) to AGND with the center tap con-
nected to FB1 (see Figure 1). Select R10 in the 10k ? to
50k ? range. Calculate R11 with the following equation:
where n NEG is the number of negative charge-pump
stages, V GOFF is the output of the negative charge-
pump regulator, V SUP is the supply voltage of the
charge-pump regulators, V D is the forward voltage drop
of the charge-pump diode, and V DROPOUT is the
dropout margin for the regulator. Use V DROPOUT = 0.6V.
The above equations are derived based on the assump-
tion that the first stage of the negative charge pump is
connected to ground. Sometimes fractional stages are
more desirable for better efficiency. This can be done
by connecting the first stage to VIN or another available
supply. If the first-stage charge pump is powered from
VIN, then the above equation becomes:
R 11 = R 10 × ? AVDD ? 1 ?
? V ?
? V FB ?
n NEG =
? V GOFF + V DROPOUT + V IN
V SUP ? 2 × V D
where V FB is the step-up regulator ’s feedback set
point. Place R10 and R11 close to the IC.
The MAX8784’s positive charge-pump regulator is a
fixed two-stage charge pump with built-in switches.
20
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| MAX8784ETL+ | 功能描述:显示驱动器和控制器 Reg, CP, Op Amp for TFT LCDs 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 |
| MAX8784ETL+T | 功能描述:显示驱动器和控制器 Reg, CP, Op Amp for TFT LCDs 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 |
| MAX8784EVKIT+ | 功能描述:显示开发工具 MAX8784 Eval Kit RoHS:否 制造商:4D Systems 产品:4Display Shields 工具用于评估:?OLED-160-G1, ?OLED-160-G2 接口类型:Serial 工作电源电压:5 V |
| MAX8785AETI+ | 功能描述:显示驱动器和控制器 Full-Bridge CCFL 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 |
| MAX8785AETI+T | 功能描述:显示驱动器和控制器 Full-Bridge CCFL 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 |
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