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| 型号： | ZL2004EVK1 |
| 厂商： | Intersil |
| 文件页数： | 21/42页 |
| 文件大小： | 0K |
| 描述： | KIT EVAL FOR ZL2004 |
| 标准包装： | 1 |
| 系列： | * |
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ZL2004
5.7.6 QL Selection
The bottom MOSFET should be selected primarily
based on the device’s R DS(ON) and secondarily based on
its gate charge. To choose QL, use the following
equation and allow 2 – 5% of the output power to be
dissipated in the R DS(ON) of QL (lower output voltages
and higher step-down ratios will be closer to 5%):
5.7.7 QH Selection
In addition to the R DS(ON) loss and gate charge loss, QH
also has switching loss. The procedure to select QH is
similar to the procedure for QL. First, assign 2 – 5% of
the output power to be dissipated in the R DS(ON) of QH
using the equation for QL above. As was done with
QL, calculate the RMS current as follows:
P QL
0 . 05 V OUT
I OUT
I toprms
I Lrms
D
Calculate the RMS current in QL as follows:
Calculate a starting R DS(ON) as follows, in this example
I botrms I Lrms
1 D
using 5%:
Calculate the desired maximum R DS(ON) as follows:
P QH
0 . 05 V OUT
I OUT
R DS ( ON )
P QL
I botrms
2
R DS ( ON )
P QH
I toprms
2
Note that the R DS(ON) given in the manufacturer’s
datasheet is measured at 25°C. The actual R DS(ON) in
the end-use application will be much higher. For
example, a Vishay Si7114 MOSFET with a junction
temperature of 125°C has an R DS(ON) that is 1.4 times
Select a MOSFET and calculate the resulting gate
drive current. Verify that the combined gate drive
current from QL and QH does not exceed 80 mA.
Next, calculate the switching time using:
higher than the value at 25°C. Select a candidate
MOSFET, and calculate the required gate drive current
as follows:
t SW
Q g
I gdr
I g
f SW
Q g
where Q g is the gate charge of the selected QH and I gdr
Keep in mind that the total allowed gate drive current
for both QH and QL is 80 mA.
MOSFETs with lower R DS(ON) tend to have higher gate
charge requirements, which increases the current and
resulting power required to turn them on and off. Since
the MOSFET gate drive circuits are integrated in the
ZL1505, this power is dissipated in the ZL1505
is the peak gate drive current available from the
ZL1505.
Although the ZL1505 has a typical gate drive current
of 3.2 A, use the minimum guaranteed current of 2 A
for a conservative design. Using the calculated
switching time, calculate the switching power loss in
QH using:
according to the following equation:
P swtop V INM
t sw I OUT
f sw
P QL
f sw Q g V INM
The total power dissipated by QH is given by the
following equation:
P QHtot
P QH
P swtop
5.7.8 MOSFET Thermal Check
Once the power dissipations for QH and QL have been
calculated, the MOSFET ’ s junction temperature can be
estimated. Using the junction-to-case
thermal
resistance (R th ) given in the MOSFET manufacturer’s
datasheet and the expected maximum printed circuit
board temperature, calculate the junction temperature
as follows:
21
T j max
T pcb
P Q
R th
FN6846.3
February 15, 2011
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ZL2005 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Digital-DC? Integrated Power Management and Conversion IC |
| ZL2005ALNF | 制造商:Intersil Corporation 功能描述:DIGITAL DC-DC CONTROLLER W/ DRIVERS - TRAY100 - Trays 制造商:Intersil Corporation 功能描述:IC REG CNTRLR BUCK PWM 36-QFN 制造商:Intersil Corporation 功能描述:Digital DC-DC Controller w/ Drivers - BULK 50 |
| ZL2005ALNFT | 功能描述:电压模式 PWM 控制器 DIGTL DC-DC CNTRLR W/DRVRS TR100 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| ZL2005ALNFT1 | 功能描述:电压模式 PWM 控制器 DIGTL DC-DC CNTRLR W/DRVRS TR1K RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| ZL2005P | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Digital-DC? Controller with Drivers and POLA/DOSA Trim |
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