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參數(shù)資料
| 型號(hào)： | SMH4814NR01 |
| 廠商： | Summit Microelectronics, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Dual Feed Active-ORing Programmable Hot Swap Controller |
| 中文描述： | 雙飼料有源ORing提供可編程熱插拔控制器 |
| 文件頁數(shù)： | 21/44頁 |
| 文件大?。?/td> | 935K |
| 代理商： | SMH4814NR01 |
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SMH4814
APPLICATIONS INFORMATION (CONTINUED)
Preliminary Information
Summit Microelectronics, Inc
2080 2.0 07/21/05
21
Operating at High Voltages
The breakdown voltage of the external active and
passive components limits the maximum operating
voltage
of
the
SMH4814
Components that must be able to withstand the full
supply voltage are: the input and output decoupling
capacitors, the protection diode in series with the
DRAIN SENSE pin, the power MOSFET switch and
the capacitor connected between its drain and gate,
the high-voltage transistors connected to the power
good outputs, and the dropper resistor connected to
the controller’s V
DD
pin.
hot-swap controller.
Over-Voltage and Under-Voltage Resistors
In Figure 15A, the three resistors (R1, R2, and R3)
connected to the OV and UV inputs must be capable
of withstanding the maximum supply voltage of several
hundred volts. The resistor values should be chosen
so that the UV or OV input reaches its corresponding
trip point (Vuv or Vov) when the incoming power feed
reaches its low or high operational limit. As the input
impedance of UV and OV is very high, large value
resistors can be used in the resistive divider. The
divider resistors should be high stability, 1% metal-film
resistors to keep the under-voltage and over-voltage
trip points accurate.
Telecom Design Example
A hot-swap telecom application may use a 48V power
supply with a –25% to +50% tolerance (i.e., the 48V
supply can vary from 36V to 72V). The formula for
calculating R1, R2, and R3 are as follows.
First, a peak current, ID
MAX
, must be specified for the
resistive network. The value of the current is arbitrary,
but it cannot be too high (self-heating in R3 becomes a
problem), or too low (the value of R3 becomes very
large, and leakage currents can reduce the accuracy
of the OV and UV trip points). The value of IDMAX
should be
≥
200μA for the best accuracy at the OV and
UV trip points. A value of 250μA for IDMAX is used to
illustrate the following calculations.
With V
OV
(2.864V) being the over-voltage trip point, R1
is calculated by the formula:
R1 =
V
OV
ID
MAX
Substituting:
R1 =
2.864V
250
μ
A
= 11.46 k
The closest standard 1% resistor value is 11.8k
Next the minimum current that flows through the
resistive divider, ID
MIN
, is calculated from the ratio of
minimum and maximum supply voltage levels
:
ID
M IN
= ID
MAX
x VS
MIN
VS
MAX
Substituting:
ID
M IN
=
250
μ
72 V
μΑ
Now the value of R3 is calculated from ID
MIN
:
R3 = VS
MIN
x V
UV
ID
MIN
V
UV
is the under-voltage trip point, also 2.864V.
Substituting:
R3 = 3125
x 2.864V
μΑ
= 825 k
The closest standard 1% resistor value is 825k
Then R2 is calculated:
(R1 + R2) = ID
UV
MIN
Or
R2 =
V
UV
ID
MIN
- R1
Substituting:
R2 =
2.864V
125
μΑ
- 11.8 k
=
20 k
10 k
=
11 k
Excel
spread
sheet
(
http://www.summitmicro.com/
)
or contact Summit
to simplify the resistor value calculations and tolerance
analysis for R1, R2, and R3.
An
is
available
at:
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| SMH4814NR02 | Dual Feed Active-ORing Programmable Hot Swap Controller |
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| SMH4814NR05 | Dual Feed Active-ORing Programmable Hot Swap Controller |
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相關(guān)代理商/技術(shù)參數(shù) |
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| SMH4814NR02 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Dual Feed Active-ORing Programmable Hot Swap Controller |
| SMH4814NR03 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Dual Feed Active-ORing Programmable Hot Swap Controller |
| SMH4814NR04 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Dual Feed Active-ORing Programmable Hot Swap Controller |
| SMH4814NR05 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Dual Feed Active-ORing Programmable Hot Swap Controller |
| SMH4814SCR00 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Dual Feed Active-ORing Programmable Hot Swap Controller |
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