SMH4042 Datasheet, PDF (18/28 Pages) Summit Microelectronics, Inc. – Hot Swap™ Controller

SMH4042
CompactPCI Applications Aid
I/O Buffers
Depending upon the application requirements there are a number of silicon solutions that employ low on-resistance
CMOS switches. Figure 6 shows one implementation using a QuickSwitch^® from Quality Semiconductor. This
particular device exhibits very Flat R_ON characteristics from 0 to 5V. The only drawback is the extra space required
for the external pull-up resistors.
early power
SMH4042
1Vref
SGNL_VLD
-
+
LMV321
OE1 OE2 OE3 OE4
B0
A0
A1
B1
B2
A28
B29
A29
B30
A30
QS34XVH245
B31
A31
2037 ILL27.0
Figure 6. Bus buffers with external pull-ups
Figure 7 shows another implementation, but the pull-up resistor structure is incorporated in the switch. The circuit also
automatically switches the bias voltage out of the circuit as the CMOS switches are enabled. A potential advantage
is the ability to place the interface closer to the edge of the card. The board designer should evaluate their requirements
and design goals and determine their best solution. The bus switches are available from both Texas Instruments and
Pericom Semiconductor.
BIASV
ON
2037-07 9/23/99
1Vref
SGNL_VLD
A0
A1
-
+
LMV321
A1
B1
Equivalent Internal
Circuit
ON
BIASV
B0
B1
B2
A8
B9
A9
A10
SN74CBT6800
or PI5C6800
B10
2037 ILL28.0
Figure 7. Bus buffers with integrated pull-ups
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