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参数资料
| 型号： | IRDC3870 |
| 厂商： | International Rectifier |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL REG SUPIRBUCK DC/DC |
| 产品变化通告： | (EP) Parts Discontinuation 25/May/2012 |
| 标准包装： | 1 |
| 系列： | * |
IR3870MPBF
Boot Capacitor Selection
The boot capacitor starts the cycle fully charged
to a voltage of VB(0). Cg equals 1.16nF in
IR3870. Choose a sufficiently small Δ V such
that VB(0)- Δ V exceeds the maximum gate
Choose the soft start capacitor:
Once the soft start time has chosen, such as
1000us to reach to the reference voltage, a
22nF for CSS is used to meet 1000us.
C BOOT ? C g ? ? B
? 1 ? (8)
V OUT ? ? V IN ? V OUT ? 1.1 V ? ? 21 V - 1.1 V ?
threshold voltage to turn on the high side
MOSFET.
? V (0) ?
? Δ V ?
Choose an inductor to meet the design
specification:
L ? ?
V IN ? Δ I ? F s 21 V ? 4 A ? 500K Hz
? 0.52u H
Choose a boot capacitor value larger than the
calculated C BOOT in equation 8. A typically
value of 0.1uF uses. The voltage rating of this
Δ I ?
1.1 V ? ? 21 V - 1.1 V ?
21 V ? 0.56u H ? 500K Hz
? 3.7 A
part needs to be larger than VB(0) plus the
desired derating voltage. Its ESR and ESL
needs to be low in order to allow it to deliver the
large current and di/dt’s which drive MOSFETs
most efficiently. In support of these
requirements a ceramic capacitor should be
chosen.
Choose an inductor with the lowest DCR and
AC power loss as possible to increase the
overall system efficiency. For instance,
choose an FDU0650-R56M manufactured by
TOKO. The inductance of this part is 820nH
and has 3.2m ? DCR. Ripple current needs
to be recalculated using the chosen inductor.
DESIGN EXAMPLE
Choose an input capacitor:
Design Criteria:
1 ? 3.7 A ?
Input Voltage, VIN, = 6V to 21V
Output Voltage, VOUT = 1.1V
Switching Frequency, FS = 500KHz
I IN_RMS ? 10 A ?
1.1 V
21 V
2
? 1 ? ? ? ? ? 2.4 A
3 ? 10 A ?
Inductor Ripple Current, Δ I = 4A
Maximum Output Current, IOUT = 10A
Over Current Trip, IOC = 14A
Overshoot Allowance, VOS = VOUT + 100mV
Undershoot Allowance, VDROP = 100mV
A Panasonic 10uF (ECJ3YB1E106M)
accommodates 6 Arms of ripple current at
300KHz. Due to the chemistry of multilayer
ceramic capacitors, the capacitance varies
Find R FF :
over temperature and operating voltage,
both AC and DC. One 10uF capacitor is
R FF ?
1.1 V
1 V ? 20 pF ? 500K Hz
? 110 K ?
recommended. In a practical solution, one
1uF capacitor is required along with 10uF.
The purpose of the 1uF capacitor is to
Pick a standard value 110 k ? , 1% resistor.
Find R SET :
suppress the switching noise and deliver
high frequency current.
R ISET ?
? 6.7K ?
1.4 ? 6.8m ? ? 14 A
20 ? A
The R DSON of the lower MOSFET could be
expected to increase by a factor of 1.4 over
temperature. Therefore, pick a 6.81 k ? , 1%
standard resistor.
Choose an output capacitor:
To meet the undershoot specification, select a set
of output capacitors which has an equivalent ESR
of 10m ? (100mV/10A). To meet the overshoot
specification, equation 7 will be used to calculate
the minimum output capacitance. As a result,
Find a resistive voltage divider for V OUT = 1.1V:
243uF will be needed for 10A load remover.
Combine those two requirements, one can
V FB ?
R 2
R 2 ? R 1
? V OUT ? 0.5 V
choose a set of output capacitors from
manufactures such as SP-Cap (Specialty
Polymer Capacitor) from Panasonic or POSCAP
R 2 = 1.65k ? , R 1 = 1.96 k ? , both 1% standard
resistors .
from Sanyo. A 270uF (EEFSX0D271) from
Panasonic is recommended.
15
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| IRDC3895 | 功能描述:电源管理IC开发工具 Design Kit Featuring IR3895M 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 |
| IRDC3897 | 功能描述:电源管理IC开发工具 Design Kit POL 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 |
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