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| 型号： | MAX749CSA-T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/12页 |
| 文件大小： | 0K |
| 描述： | IC BIAS SUPPLY LCD DIG ADJ 8SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | LCD 显示器 |
| 电流 - 电源： | 60µA |
| 电源电压： | 2 V ~ 6 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOIC |
| 包装： | 带卷 (TR) |
Digitally Adjustable LCD Bias Supply
The Sumida CD54-470N (47μH, 720mA, 370m ? ) is suit-
Table 2. Component Suppliers
able for a wide range of applications, and the larger
CD105-470N (47μH, 1.17A, 170m ? ) permits higher cur-
rent levels and efficiencies.
Diode Selection
The MAX749’s high switching frequency demands a high-
speed rectifier. Schottky diodes such as the 1N5817-
1N5822 family are recommended. Choose a diode with an
average current rating approximately equal to the peak
current, as determined by 180mV/R SENSE and a break-
down voltage greater than V+ + I -V OUTMAX I .
External Switching Transistor
The MAX749 can drive a PNP transistor or a P-channel
logic-level MOSFET. The choice of a power switch is
dictated by the input voltage range, cost, and efficiency.
MOSFETs provide the highest efficiency because they
do not draw any DC gate-drive current (see Typical
Operating Characteristics graphs). However, a gate-
source voltage of several volts is needed to turn on a
MOSFET, so a 5V or greater input supply is required
(although this restriction may change as lower-thresh-
old P-channel MOSFETs become available). PNP tran-
sistors, meanwhile, may be used over the entire 2V to
SUPPLIER
INDUCTORS
Coiltronics
Gowanda
Sumida USA
Sumida Japan
CAPACITORS
Kemet
Matsuo
Nichicon
Sprague
Sanyo USA
Sanyo Japan
United Chemi-Con
DIODES
Motorola
Nihon USA
Nihon Japan
PHONE
(305) 781-8900
(716) 532-2234
(708) 956-0666
81-3-3607-511
(803) 963-6300
(714) 969-2491
(708) 843-7500
(603) 224-1961
(619) 661-6322
81-3-3837-6242
(714) 255-9500
(800) 521-6274
(805) 867-2555
81-3-3494-7411
FAX
(305) 782-4163
(716) 532-2702
(708) 956-0702
81-3-3607-5428
(803) 963-6322
(714) 960-6492
(708) 843-2798
(603) 224-1430
(714) 255-9400
(805) 867-2698
81-3-3494-7414
6V operating voltage range of the MAX749.
POWER TRANSISTORS - MOSFETS
When using a MOSFET, connect DHI and DLOW to its
gate (see Typical Operating Circuit). When using a PNP
Harris
(407) 724-3739
(407) 724-3937
transistor, connect DHI to its base, and connect a resis-
tor between the base and DLOW (R BASE ) (Figure 1). The
PNP transistor is turned off quickly by the direct pull-up
of DHI, and turned on by the base current provided
through R BASE . This resistor limits the transistor’s base-
drive current to (V IN - 140mV - V BE )/R BASE , where V IN is
the input voltage, 140mV is the drop across R SENSE , V BE
is the transistor’s base-emitter voltage, and R BASE is the
current-limiting resistor. For maximum efficiency, make
R BASE as large as possible, but small enough so that the
transistor is always driven into saturation.
Highest efficiency with a PNP transistor comes from
using a device with a low collector-emitter saturation
voltage and a high current gain. Use a fast-switching
type. For example the Zetex ZTX792A has switching
speeds of 40ns (t ON ) and 500ns (t OFF ).
The transistor must have a collector-to-emitter (PNP) or
drain-to-source (MOSFET) voltage rating greater than the
input-to-output voltage differential (V IN - V OUT ). In either
case the transistor must have a current rating that exceeds
the peak current set by the current-sense resistor.
PNP transistors are generally less expensive than P-
channel MOSFETs. Table 2 lists some suppliers of
switching transistors suitable for use with the MAX749.
International
(213) 772-2000 (213) 772-9028
Rectifier
Siliconix (408) 988-8000 (408) 727-5414
POWER TRANSISTORS - PNP TRANSISTORS
Zetex USA (516) 543-7100 (516) 864-7630
Zetex UK 44 (61) 727 5105 44 (61) 627 5467
CURRENT-SENSE RESISTORS
IRC (512) 992-7900 (512) 992-3377
Base Resistor
The base resistor, R BASE in Figure 1, controls the amount of
base current in the PNP transistor. A low value for R BASE
increases base drive, which provides higher output cur-
rents and compensates for lower input voltages, but
decreases efficiency. Conversely, a high R BASE value
increases efficiency but reduces the output capability,
especially at low voltages. When using high-gain transis-
tors, e.g. the Zetex ZTX750 or ZTX792, typical values for
R BASE are in the 150 ? to 510 ? range, but will depend on
the required input voltage range and output current (see
Typical Operating Characteristics). Lower-gain transistors
require lower values for R BASE and are less efficient. Larger
R BASE values are suitable if less output power is required.
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX749EPA | 功能描述:显示驱动器和控制器 Digitally Adjustable LCD Bias Supply 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 |
| MAX749EPA+ | 功能描述:其他电源管理 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX749ESA | 功能描述:显示驱动器和控制器 Digitally Adjustable LCD Bias Supply 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 |
| MAX749ESA+ | 功能描述:其他电源管理 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX749ESA+ | 制造商:Maxim Integrated Products 功能描述:IC LCD BIAS SUPPLY 8-SOIC 制造商:Maxim Integrated Products 功能描述:IC, LCD BIAS SUPPLY, 8-SOIC |
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