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参数资料
| 型号： | IRDC3629 |
| 厂商： | International Rectifier |
| 文件页数： | 13/23页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL SYNC BUCK CONTROLLER |
| 标准包装： | 1 |
| 系列： | * |
IR3629/IR3629A MPbF
Power MOSFET Selection
The IR3629A uses two N-Channel MOSFETs per
channel. The selection criteria to meet power
transfer requirements are based on maximum
drain-source voltage (V DSS ), gate-source drive
voltage (V gs ), maximum output current, On-
resistance R DS(on) , and thermal management.
switching losses in a synchronous Buck
converter. The synchronous MOSFET turns on
under zero voltage conditions, therefore, the turn
on losses for synchronous MOSFET can be
neglected. With a linear approximation, the total
switching loss can be expressed as:
V ds ( off ) t r + t f
The MOSFET must have a maximum operating
voltage (V DSS ) exceeding the maximum input
voltage (V in ).
Where:
P sw =
*
2 T
* I load - - - (10)
P cond = (upper switch) = I load ? R ds(on) ? D ? ?
P cond = (lower switch) = I load ? R ds(on) ? (1 ? D) ? ?
The gate drive requirement is almost the same
for both MOSFETs. A logic-level transistor can
be used and caution should be taken with
devices at very low gate threshold voltage (V gs )
to prevent undesired turn-on of the
complementary MOSFET, which results in a
shoot-through current.
The total power dissipation for MOSFETs
includes conduction and switching losses. For
the Buck converter the average inductor current
is equal to the DC load current. The conduction
loss is defined as:
2
2
? = R ds(on) temperatu re dependency
V ds(off) = Drain to source voltage at the off time
t r = Rise time
t f = Fall time
T = Switching period
I load = Load current
The switching time waveforms is shown in
figure12.
V DS
90%
10%
The R DS(on) temperature dependency should be
considered for the worst case operation. This is
V GS
t d (ON)
t r
t d (OFF)
t f
typically given in the MOSFET datasheet. Ensure
that the conduction losses and switching losses
do not exceed the package ratings or violate the
overall thermal budget.
For this design, the IRF6712 is selected for
control FET and IRF6715 is selected for the
synchronous FET. These devices provide low on
resistance in a DirectFET package.
The MOSFETs have the following data:
Fig. 12: switching time waveforms
From IRF6712 data sheet:
tr = 11ns
tf = 19ns
These values are taken under a certain test
condition. For more details please refer to the
IRF6712 data sheet.
By using equation (10), we can calculate the
ControlFET (IRF6712) :
V ds = 25 V,Q g = 12 nC
R ds(on) = 3 . 8 m ? @ V gs = 10 V
SyncFET (IRF6715) :
V ds = 25 V,Q g = 40 nC
R ds(on) = 1 . 3 m ? @ V gs = 10 V
switching losses. P sw =1.35W at Io=25A.
The reverse recovery loss is also another
contributing factor in control FET switching
losses. This is equivalent to extra current
The conduction losses will be: P con =1.05W at
Io=25A. The switching loss is more difficult to
calculate, even though the switching transition is
well understood. The reason is the effect of the
parasitic components and switching times during
the switching procedures such as turn-on / turn-
off delays and rise and fall times. The control
MOSFET contributes to the majority of the
11/29/2007
required to remove the minority charges from the
synchronous FET. The reverse recovery loss can
be expressed as:
P Qrr = Q rr *t rr *F s
Q rr : Re verse Re cov ery Ch arg e
t rr : Re verse Re cov ery Time
F s : Switchin g Frequen cy
13
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| IRDC3629A | 功能描述:电源管理IC开发工具 IR3629A Eval BRD 300kHz Controller 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 |
| IRDC3637 | 功能描述:电源管理IC开发工具 250kHz to 9MHz IR350B Xphase IC 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 |
| IRDC3637EVAL | 制造商:IRF 制造商全称:International Rectifier 功能描述:IR3637 EVALUATION BOARD USER GUIDE |
| IRDC3640 | 功能描述:电源管理IC开发工具 IR3640 12V PWM 1.5MHz Controller 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 |
| IRDC3651 | 功能描述:电源管理IC开发工具 IR3651 EVAL BRD 400kHz 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 |
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