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参数资料
| 型号： | FAN5236MTCX |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 16/19页 |
| 文件大小： | 0K |
| 描述： | IC CTLR DDR/PWM DUAL HE 28TSSOP |
| 产品变化通告： | Mold Compound Change 30/Nov/2007 |
| 标准包装： | 1 |
| 应用： | 控制器，移动式 DDR |
| 输入电压： | 5 V ~ 24 V |
| 输出数： | 2 |
| 输出电压： | 0.9 V ~ 5 V |
| 工作温度： | -10°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 28-TSSOP |
| 包装： | 标准包装 |
| 产品目录页面： | 1221 (CN2011-ZH PDF) |
| 其它名称： | FAN5236MTCXDKR |
Dual Converter 180° Phased
In dual mode (shown in Figure 6), both converters
contribute to the capacitor input ripple current. With
each converter operating 180° out of phase, the RMS
currents add in the following fashion:
P UPPER is the upper MOSFET’s total losses and P SW
and P COND are the switching and conduction losses for a
given MOSFET. R DS(ON) is at the maximum junction
temperature (T J ). t S is the switching period (rise or fall
time), shown as t2+t3 in Figure 17.
I
RMS
= I
RMS ( 1 )
2
+ I
RMS ( 2 )
2
or
(24)
V DS
C ISS
C GD
C ISS
I RMS =
( I 1 ) 2 ( D 1 ? D 1 2 ) + ( I 2 ) 2 ( D 2 ? D 2 2 )
(25)
which, for the dual 3A converters shown in Figure 6,
calculates to:
I
RMS
= 1 . 4 A
(26)
I D
Power MOSFET Selection
Losses in a MOSFET are the sum of its switching (P SW )
and conduction (P COND ) losses.
In typical applications, the FAN5236 converter’s output
voltage is low with respect to its input voltage.
V SP
V TH
V GS
Q GS
Q GD
Q G(SW)
4.5V
Therefore, the lower MOSFET (Q2) is conducting the
full load current for most of the cycle. Q2 should
therefore be selected to minimize conduction losses,
t1
Figure 17.
t2
t3 t4 t5
Switching Losses and Q G
thereby selecting a MOSFET with low R DS(ON) .
In contrast, the high-side MOSFET (Q1) has a shorter
duty cycle and it’s conduction loss has less impact. Q1,
5V
VIN
however, sees most of the switching losses, so Q1’s
primary selection criteria should be gate charge.
High-Side Losses
Figure 17 shows a MOSFET’s switching interval, with
the upper graph being the voltage and current on the
R D
HDRV
SW
G
C GD
R GATE
C GS
drain-to-source and the lower graph detailing V GS vs.
time with a constant current charging the gate. The X-
axis, therefore, is also representative of gate charge
Figure 18.
Drive Equivalent Circuit
(Q G ). C ISS = C GD + C GS and it controls t1, t2, and t4
timing. C GD receives the current from the gate driver
during t3 (as V DS is falling). The gate charge (Q G )
parameters on the lower graph are either specified or
can be derived from MOSFET datasheets.
Assuming switching losses are about the same for both
The driver’s impedance and C ISS determine t2, while
t3’s period is controlled by the driver’s impedance and
Q GD . Since most of t S occurs when V GS = V SP , use a
constant current assumption for the driver to simplify
the calculation of t S :
V CC ? V SP
?
?
+ R GATE ? ?
? R
the rising edge and falling edge, Q1’s switching losses
occur during the shaded time when the MOSFET has
voltage across it and current through it.
These losses are given by:
t s =
Q G ( SW )
I DRIVER
=
Q G ( SW )
? DRIVER
? ?
(30)
× I L
× 2 × t s ? f SW
P SW = ? DS
? ?
?
?
× I OUT 2 × R DS ( ON )
P COND =
Q G ( SW ) = Q GD + Q GS ? Q TH
P UPPER = P SW + P COND
? V ?
2
V OUT
V IN
? 2002 Fairchild Semiconductor Corporation
FAN5236 ? Rev. 1.3.2
(27)
(28)
(29)
16
Most MOSFET vendors specify Q GD and Q GS. Q G(SW)
can be determined as:
(31)
where Q TH is the gate charge required to get the
MOSFET to its threshold (V TH ).
www.fairchildsemi.com
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| FAN5236QSC | 功能描述:开关变换器、稳压器与控制器 DC/DC RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FAN5236QSC_Q | 功能描述:开关变换器、稳压器与控制器 DC/DC RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FAN5236QSCX | 功能描述:开关变换器、稳压器与控制器 PWM Controller RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FAN5240 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:Multi-Phase PWM Controller for AMD Mobile Athlon TM and Duron TM |
| FAN5240_06 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:Multi-Phase PWM Controller for AMD Mobile Athlon and Duron |
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