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| 型号： | MAX1901EAI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 23/33页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PWR SPLY LN 28-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 4.2 V ~ 30 V |
| 输出数： | 4 |
| 输出电压： | 2.5 V ~ 5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
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500kHz Multi-Output, Low-Noise Power-Supply
Controllers for Notebook Computers
P TOTAL = The sum of the output power from all outputs
I TOTAL = P TOTAL / V OUT = The equivalent output cur-
rent referred to V OUT
distributed between Q1 and Q2 according to duty fac-
tor (see the following equations). Generally, switching
losses affect only the upper MOSFET, since the
Schottky rectifier clamps the switching node in most
L PRIMARY =
V OUT ( V IN ( MAX ) - V OUT )
V IN ( MAX ) × f × I TOTAL × LIR
cases before the synchronous rectifier turns on. Gate
charge losses are dissipated by the driver and don ’ t
heat the MOSFET. Calculate the temperature rise
Turns Ratio N =
V SEC + V FWD
V OUT ( MIN ) + V RECT + V SENSE
according to package thermal-resistance specifications
to ensure that both MOSFETs are within their maximum
junction temperature at high ambient temperature. The
PD upperFET LOAD DS ( ON ) × DUTY
= I
× R
+ 20 ns ?
?
?
?
PD upperFET LOAD DS ( ON ) × ( 1 - DUTY )
= I
× R
DUTY = ( V OUT + V Q 2 ) ( V IN Q 1 )
where: V SEC = the minimum required rectified sec
ondary output voltage
V FWD = the forward drop across the secondary
rectifier
V OUT(MIN) = the minimum value of the main out
put voltage (from the Electrical
Characteristics tables)
V RECT = the on-state voltage drop across the
synchronous rectifier MOSFET
V SENSE = the voltage drop across the sense
resistor
In positive-output applications, the transformer sec-
ondary return is often referred to the main output volt-
age, rather than to ground, to reduce the needed turns
ratio. In this case, the main output voltage must first be
subtracted from the secondary voltage to obtain V SEC .
Selecting Other Components
MOSFET Switches
The high-current N-channel MOSFETs must be logic-
level types with guaranteed on-resistance specifica-
tions at V GS = 4.5V. Lower gate threshold
specifications are better (i.e., 2V max rather than 3V
max). Drain-source breakdown voltage ratings must at
least equal the maximum input voltage, preferably with
a 20% derating factor. The best MOSFETs will have the
lowest on-resistance per nanocoulomb of gate charge.
Multiplying R DS(ON) ? Q G provides a good figure for
comparing various MOSFETs. Newer MOSFET process
technologies with dense cell structures generally per-
form best. The internal gate drivers tolerate >100nC
total gate charge, but 70nC is a more practical upper
limit to maintain best switching times.
In high-current applications, MOSFET package power
dissipation often becomes a dominant design factor.
I 2 R power losses are the greatest heat contributor for
both high-side and low-side MOSFETs. I 2 R losses are
worst-case dissipation for the high-side MOSFET
occurs at both extremes of input voltage, and the
worst-case dissipation for the low-side MOSFET occurs
at maximum input voltage:
2
+ V IN × I LOAD × f ×
? V IN × C RSS ?
I GATE
2
/ - V
where: On-state voltage drop V Q_ = I LOAD ? R DS(ON)
C RSS = MOSFET reverse transfer capacitance
I GATE = DH driver peak output current capability
(1A typ)
20ns = DH driver inherent rise/fall time
Under output short-circuit, the MAX1904 synchronous
rectifier MOSFET suffers extra stress because its duty
factor can increase to greater than 0.9. It may need to
be oversized to tolerate a continuous DC short circuit.
During short circuit, the MAX1901/MAX1902 ’ s output
undervoltage shutdown protects the synchronous recti-
fier under output short-circuit conditions.
To reduce EMI, add a 0.1μF ceramic capacitor from the
high-side switch drain to the low-side switch source.
Rectifier Clamp Diode
The rectifier diode is a clamp across the low-side MOS-
FET that catches the negative inductor swing during
the 60ns dead time between turning one MOSFET off
and each low-side MOSFET on. The latest generations
of MOSFETs incorporate a high-speed Schottky diode,
which serves as an adequate clamp diode. For
MOSFETs without integrated Schottky diodes, place a
Schottky diode in parallel with the low-side MOSFET.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1901ETJ | 功能描述:DC/DC 开关控制器 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 |
| MAX1901ETJ+ | 功能描述:DC/DC 开关控制器 500kHz Multi-Output Power-Supply Ctlr 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 |
| MAX1901ETJ+T | 功能描述:DC/DC 开关控制器 500kHz Multi-Output Power-Supply Ctlr 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 |
| MAX1901ETJ-T | 功能描述:DC/DC 开关控制器 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 |
| MAX1902EAI | 功能描述:DC/DC 开关控制器 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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