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参数资料
| 型号： | MAX8745ETJ+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 30/36页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PWR SUP QUAD 32TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 6 V ~ 26 V |
| 输出数： | 4 |
| 输出电压： | 3.3V，5V，1 V ~ 26 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
INPUT CAPACITOR RMS CURRENT
vs. INPUT VOLTAGE
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
IN PHASE
50/50 INTERLEAVING
40/60 OPTIMAL
INTERLEAVING
6
8
10
12
14
16
18
20
V IN (V)
INPUT RMS CURRENT FOR INTERLEAVED OPERATION:
? I IN ) ( D LX 5 ? D OL ) + ( I OUT 3 ? I IN ) ( D LX 3 ? D OL ) + ( I OUT 5 + I OUT 3 ? I IN
I RMS =
( OUT 5
2 2
)
2
D OL + I IN 2 ( 1 ? D LX 5 ? D LX 3 + D OL
)
D LX 5 = OUT 5
D LX 3 = OUT 3
V
V IN
V
V IN
D OL = DUTY ? CYCLE OVERLAP FRACTION
I IN =
V OUT5 I OUT5 + V OUT3 I OUT3
V IN
INPUT RMS CURRENT FOR SINGLE-PHASE OPERATION:
I RMS = I LOAD ?
?
(
?
?
?
?
V IN
V OUT V IN ? V OUT
) ? ?
?
?
Figure 8. Input RMS Current
The 40/60 optimal interleaved architecture of the
MAX8744/MAX8745 allows the input voltage to go as
low 8.3V before the duty cycles begin to overlap. This
offers improved efficiency over a regular 180° out-of-
phase architecture where the duty cycles begin to
overlap below 10V. Figure 8 shows the input-capacitor
RMS current vs. input voltage for an application that
requires 5V/5A and 3.3V/5A. This shows the improve-
ment of the 40/60 optimal interleaving over 50/50 inter-
leaving and in-phase operation.
For most applications, nontantalum chemistries (ceram-
ic, aluminum, or OS-CON) are preferred due to their
resistance to power-up surge currents typical of sys-
tems with a mechanical switch or connector in series
with the input. Choose a capacitor that has less than
10°C temperature rise at the RMS input current for opti-
mal reliability and lifetime.
Power-MOSFET Selection
Most of the following MOSFET guidelines focus on the
challenge of obtaining high load-current capability
when using high-voltage (> 20V) AC adapters. Low-
current applications usually require less attention.
The high-side MOSFET (N H ) must be able to dissipate
the resistive losses plus the switching losses at both
V IN(MIN) and V IN(MAX) . Ideally, the losses at V IN(MIN)
should be roughly equal to the losses at V IN(MAX) , with
lower losses in between. If the losses at V IN(MIN) are
significantly higher, consider increasing the size of N H .
Conversely, if the losses at V IN(MAX) are significantly
higher, consider reducing the size of N H . If V IN does not
vary over a wide range, maximum efficiency is achieved
by selecting a high-side MOSFET (N H ) that has conduc-
tion losses equal to the switching losses.
30
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