MIC2561 Datasheet, PDF (7/8 Pages) Micrel Semiconductor – PCMCIA Card Socket VCC & VPP Switching Matrix

MIC2561
5V
System
Power 3.3V
Supply
12V
PCMCIA
Card Slot
Controller
VPPIN VCC3IN VCC5IN
EN0
EN1
MIC2561
VCC5_EN
VCC3_EN
VPP1
VPP2 PCMCIA
Card Slot
VCC
Micrel
Figure 4. MIC2561 Typical PCMCIA memory card application with dual V_CC (5.0V or 3.3V). Note that V_PP1 and V_PP2 are
driven together.
However, many cost sensitive designs (especially notebook/
palmtop computers) connect V_PP1 to V_PP2 and the MIC2557
is not required. This circuit is shown in Figure 4.
When a memory card is initially inserted, it should receive
V_CC — either 3.3V ± 0.3V or 5.0V ±5%. The initial voltage is
determined by a combination of mechanical socket “keys”
and voltage sense pins. The card sends a handshaking data
stream to the controller, which then determines whether or
not this card requires V_PP and if the card is designed for dual
V_CC. If the card is compatible with and desires a different V_CC
level, the controller commands this change by disabling V_CC,
waiting at least 100ms, and then re-enabling the other V_CC
voltage.
If no card is inserted or the system is in sleep mode, the
controller outputs a (V_CC3 IN, V_CC5 IN) = (0,0) to the
MIC2561, which shuts down V_CC. This also places the switch
into a high impedance output shutdown (sleep) mode, where
current consumption drops to nearly zero, with only tiny
CMOS leakage currents flowing.
During Flash memory programming with standard (+12V)
Flash memories, the PCMCIA controller outputs a (1,0) to the
EN0, EN1 control pins of the MIC2561, which connects
V_PP IN to V_{PP OUT}. The low ON resistance of the MIC2561
switches allow using small bypass capacitors (in some cases,
none at all) on the V_{CC OUT} and V_{PP OUT} pins, with the main
filtering action performed by a large filter capacitor on the
input supply voltage to V_PP IN (usually the main power
supply filter capacitor is sufficient). The V_{PP OUT} transition
from V_CC to 12.0V typically takes 15µs. After programming is
completed, the controller outputs a (EN1, EN0) = (0,1) to the
MIC2561, which then reduces V_{PP OUT} to the V_CC level for
read verification. Break-before-make switching action re-
duces switching transients and lowers maximum current
spikes through the switch from the output capacitor. The flag
comparator prevents having high voltage on the V_{PP OUT}
capacitor from contaminating the V_CC inputs, by disabling the
low voltage V_PP switches until V_{PP OUT} drops below the V_CC
level selected. The lockout delay time varies with the load
current and the capacitor on V_{PP OUT}. With a 0.1µF capacitor
and nominal I_{PP OUT}, the delay is approximately 250µs.
Internal drive and bias voltage is derived from V_PP IN. Internal
device control logic is powered from V_CC3 IN. Input logic
threshold voltages are compatible with common PCMCIA
controllers using either 3.3V or 5V supplies. No pull-up
resistors are required at the control inputs of the MIC2561.
Output Current and Protection
MIC2561 output switches are capable of more current than
needed in PCMCIA applications and meet or exceed all
PCMCIA specifications. For system and card protection,
output currents are internally limited. For full system protec-
tion, long term (millisecond or longer) output short circuits
invoke overtemperature shutdown, protecting the MIC2561,
the system power supplies, the card socket pins, and the
memory card. The MIC2561 overtemperature shutdown oc-
curs at a die temperature of 110°C.
Suspend Mode
An additional feature in the MIC2561 is a pseudo power-down
mode, Suspend Mode, which allows operation without a V_PP
IN supply. In Suspend Mode, the MIC2561 supplies 3.3V to
V_CC OUT whenever a V_CC output of 3.3V is enabled by the
PCMCIA controller. This mode allows the system designer
the ability to turn OFF the V_PP supply generator to save
power when it is not specifically required. The PCMCIA card
receives V_CC at reduced capacity during Suspend Mode, as
the switch resistance rises to approximately 4.5Ω.
High Current V_CC Operation Without a
+12V Supply
Figure 5 shows the MIC2561 with V_CC switch bias provided
by a simple charge pump. This enables the system designer
to achieve full V_CC performance without a +12V supply,
which is often helpful in battery powered systems that only
provide +12V when it is needed. These on-demand +12V
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1997