SMH4811A(2000) 데이터 시트보기 (PDF) - Summit Microelectronics
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SMH4811A Datasheet PDF : 16 Pages
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SMH4811A
APPLICATIONS CIRCUITS
Temperature Sensing
The 2.5V reference and 5V outputs on the SMH4811A
make it easy to expand the enable or monitoring inputs.
The circuit in Figure 4 illustrates how a low-voltage com-
parator is used to make an over-temperature detector.
The comparator draws power from the 5V output on the
SMH4811A and uses the 2.5V reference for the switching
threshold. R6 is an NTC resistor that causes the
SMH4811A to shut down when the maximum ambient
temperature is exceeded. The temperature trip point is
altered by changing R6 and/or R7. A 1MΩ resistor adds
hysteresis around the comparator to prevent oscillation
near the trip point.
Reversing Polarity of the Power Good Outputs
The open-drain Power Good outputs on the SMH4811A
are active low. The output polarity may be changed to
active high, when required, with a minor circuit change
around the high-voltage buffer transistor. See Figure 5.
The 1N4148 blocking diode must be included to prevent
high-voltage damage to the SMH4811A.
Illustrations
Notes:
1.
In Figures 4, 5, 6, and 7 the resistor
RV must be physically located as close to the FET
as possible.
2.
The "Pin Detect" pins must be
shorter than the other pins so that they do not
make contact with the card connector until the
card is well seated.
3.
In Figure 4 the following values are
used: R4 = 1kW, R5 = 1MW, R6 = NTC 50kW @
TMAX, R7 = 50kW, U1 = LMV331. Formulas for
determining these values appear in the previous
section of the Data Sheet.
4.
In Figure 6 the "On/Off" transistor
must be physically close to the DC/DC converter.
48V
RD
100kΩ
MM6T-
A06LT1
PG#
100nF
25V
0V
PD1# VDD
EN/TS
CBFAULT#
PG#
5.0VREF
ENPG
R3
UV
SMH4811A
R2
OV
R1
PD2# VSS CBSENSE VGATE
EN/TS
2.5VREF
DRAIN
SENSE
R4
R5
R6
+
– U1
R7
1kΩ
100nF
100nF
1kΩ
100nF
100V
20mΩ
10Ω RV*
10nF
1N4148
4.7µF
100V
Figure 4. Basic Distributed Power Hot Swap Circuit
2044 4.1 8/1/00
SUMMIT MICROELECTRONICS, Inc.
10
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