LTC1472_15 Datasheet, PDF (10/16 Pages) Linear Technology – Protected PCMCIA VCC and VPP Switching Matrix

LTC1472
APPLICATIONS INFORMATION
Interfacing to “365” Type Controllers
The LTC1472 also interfaces directly with “365” type
controllers as shown in Figure 2. The V_CC Enable inputs
are connected differently than to the CL-PD6710 control-
ler because the “365” type controllers use active-high
logic control of the V_CC switches (see the V_CC Switch Truth
Table). No “glue logic” is required to interface to this type
of PCMCIA compatible controller.
12V Power Requirements
Note that in Figure 2, a “local” 5V to 12V converter is not
used. The LTC1472 works equally well with or without
continuous 12V power. If the main power supply system
has 12V continuously available, simply connect it to the
VPP_IN pin. Internal circuitry automatically senses its pres-
ence and uses it to switch the internal VPP switches.
The 12V shutdown output can be used to shut down the
system 12V power supply (if not required for any purpose
other than VPP programming).
5V Power Requirements
The LTC1472 has been designed to operate without con-
tinuous 12V power, but continuous 5V power is required
at the V_DD and 5V_IN supply pins for proper operation and
should always be present when a card is powered (whether
it is a 5V or 3.3V only card).
If the 5V power must be turned off, for example, to enter
a 3.3V only full system “sleep” mode, the 5V supply must
be turned off at least 100µs after the V_CC and VPP switches
have been programmed to the Hi-Z or 0V states. This
ensures that the gates of the NMOS switches are com-
pletely discharged.
Also, the V_CC switches cannot be operated properly with-
out 5V power. They must be programmed to the off state
at least 100µs prior to turning the 5V supply off, or they
may be left in an indeterminate state.
Supply Bypassing
For best results, bypass the supply input pins with 1µF
capacitors as close as possible to the LTC1472. Some-
times, much larger capacitors are already available at the
outputs of the 3.3V, 5V and 12V power supply. In this case,
it is still good practice to use 0.1µF capacitors as close as
possible to the LTC1472, especially if the power supply
output capacitors are more than 2" away on the printed
circuit board.
12V
12V SHUTDOWN
(OPTIONAL)
3.3V
5V
0.1µF
0.1µF
“365”TYPE
CONTROLLER
A_VPP_EN0
A_VPP_EN1
A_V_CC _EN0
A_V_CC _EN1
10k
3V_IN
5V_IN
3V_IN SHDN
VPP_IN
VPP_OUT
V_CC(IN)
LTC1472
V_DD
VPP EN0
VPP EN1
V_CC EN0
V_CC EN1
GND
V_CC(OUT)
V_CC(OUT)
GND
(0V, V_CC, 12V, Hi-Z)
0.1µF
+
10k
(OFF, 3.3V, 5V)
1µF
TANT
VPP1
VPP2
PCMCIA
CARD SLOT
V_CC
V_CC
LTC1472-F02
Figure 2. Direct Interface to Industry Standard PCMCIA Controller and LT1301 Step-Up Switching Regulator
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