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| 型号： | MAX1778EUG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 29/39页 |
| 文件大小： | 0K |
| 描述： | IC DCDC CONV MULTI OUT 24TSSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 62 |
| 应用： | 转换器，TFT，LCD |
| 输入电压： | 2.7 V ~ 5.5 V |
| 输出数： | 5 |
| 输出电压： | 2.7 V ~ 13 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 24-TSSOP |
| 包装： | 管件 |
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MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC/DC
Converters with Buffer
at higher output currents (see the Typical Operating
Characteristics). So the maximum efficiency can be
approximated by:
V CXN ( NEG ) > 1 . 5 ( V SUPN N )
η POS ?
V POS
V SUPD + V SUPP N
for the negative charge pump, where N is the stage
number in which the flying capacitor appears, and
V SUPD is the positive charge pump ’s diode supply
(Figure 4). For example, the two-stage positive charge
for the positive charge pump, and:
pump in the typical application circuit (Figure 1) where
V SUPP = V SUPD = 8V contains two flying capacitors.
η NEG ?
V NEG
V SUPN N
The flying capacitor in the first stage (C4) requires a
voltage rating over 12V. The flying capacitor in the
second stage (C6) requires a voltage rating over 24V.
for the negative charge pump, where V SUPD is the
positive charge pump’s diode supply (Figure 4).
Output-Voltage Selection
Adjust the positive output voltage by connecting a volt-
age-divider from the output (V POS ) to FBP to GND (see
the Typical Operating Circuit ). Adjust the negative
output voltage by connecting a voltage-divider from the
Charge-Pump Output Capacitor
Increasing the output capacitance or decreasing the
ESR reduces the output ripple voltage and the peak-to-
peak transient voltage. With ceramic capacitors, the
output-voltage ripple is dominated by the capacitance
value. Use the following equation to approximate the
required capacitor value:
output (V NEG ) to FBN to REF. Select R4 and R6 in the
50k ? to 100k ? range. Higher resistor values improve
efficiency at low output current but increase output-
C OUT ≥
I LOAD
f CHP V RIPPLE
voltage error due to the feedback input bias current. For
the negative charge pump, higher resistor values also
reduce the load on the reference, which should not
exceed 50μA for greatest accuracy (including current
through the FLTSET resistors) to guarantee that V REF
remains in regulation (see the Electrical Characteristics).
Calculate the remaining resistors with the following
equations:
R3 = R4 [(V POS /V REF ) - 1]
R5 = R6 |V NEG /V REF |
where V REF = 1.25V. V POS can range from V SUPP to
40V, and V NEG can range from 0V to -40V.
Flying Capacitor
Increasing the flying capacitor (CX) value increases the
output current capability. Above a certain point,
increasing the capacitance has a negligible effect
because the output current capability becomes domi-
nated by the internal switch resistance and the diode
impedance. The flying capacitor’s voltage rating must
exceed the following:
V CXN ( POS ) > 1 . 5 [ V SUPD + V SUPP ( N - 1 ) ]
for the positive charge pump, and:
Maxim Integrated
where f CHP is typically f OSC /2 (see the Electrical
Characteristics).
Charge-Pump Input Capacitor
Use a bypass capacitor with a value equal to or greater
than the flying capacitor. Place the capacitor as close
as possible to the IC. Connect directly to power ground
(PGND).
Charge-Pump Rectifier Diodes
Use Schottky diodes with a current rating equal to or
greater than two times the average charge-pump input
current, and a voltage rating at least 1.5 times V SUPP
for the positive charge pump and V SUPN for the
negative charge pump.
Low-Dropout Linear Regulator (MAX1778/
MAX1881/MAX1883/MAX1884 Only)
Output-Voltage Selection
Adjust the linear-regulator output voltage by connecting
a voltage-divider from LDOOUT to FBL to GND
(Figure 5). Select R8 in the 5k ? to 50k ? range. Calculate
R7 with the following equation:
R7 = R8 [(V LDOOUT /V FBL ) - 1]
where V FBL = 1.25V, and V LDOOUT can range from
1.25V to (V SUPL - 300mV). FBL’s input bias current is
0.8μA (max). For less than 0.5% error due to FBL input
bias current (I FBL ), R8 must be less than 8k ? .
29
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1778EUG+ | 功能描述:直流/直流开关转换器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EUG+T | 功能描述:直流/直流开关转换器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EUG-T | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EVKIT | 功能描述:电源管理IC开发工具 MAX1778/80/81/82 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 |
| MAX1779EUE | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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