MIC2560_06 Datasheet, PDF (7/8 Pages) Micrel Semiconductor – PCMCIA Card Socket VCC and VPP Switching Matrix

Micrel, Inc.
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
MIC2560, 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 MIC2560,
which connects V_{PP IN} to V_{PP OUT}. The low ON resistance
of the MIC2560 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 250µs. After programming is completed,
the controller outputs a (EN1, EN0) = (0,1) to the
MIC2560, which then reduces V_{PP OUT} to the V_CC level for
read verification. Break-before-make switching action
reduces 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 MIC2560.
Output Current and Protection
MIC2560 output switches are capable of more current
than needed in PC Card applications (1A) and meet or
exceed all PCMCIA specifications. For system and card
protection, output currents are internally limited. For full
system protection, long term (millisecond or longer)
output short circuits invoke overtemperature shutdown,
protecting the MIC2560, the system power supplies, the
card socket pins, and the memory card. Overtemp-
erature shutdown typically occurs at a die temperature of
115°C.
Single V_CC Operation
For PC Card slots requiring only a single V_CC, connect
V_{CC3 IN} and V_{CC5 IN} together and to the system V_CC supply
(i.e., Pins 1, 3, and 15 are all connected to system V_CC).
MIC2560
Either the V_CC5 switch or the V_CC3 switch may be used to
enable the card slot V_CC; generally the V_CC3 switch is
preferred because of its lower ON resistance.
Suspend Mode
An additional feature in the MIC2560 is a pseudo power-
down mode, Suspend Mode, which allows operation
without a V_{PP IN} supply. In Suspend Mode, the MIC2560
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.
Figure 5. Circuit for Generating Bias Drive for the V_CC
Switches when +12V is Not Readily Available.
High Current V_CC Operation Without a +12V Supply
Figure 5 shows the MIC2560 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 supplies generally have a
quiescent current draw of a few milli-amperes, which is
far more than the microamperes used by the MIC2560.
The charge pump of figure 5 provides this low current,
using about 100µA when enabled. When V_{PP OUT} =12V is
selected, however, the on-demand V_PP generator must
be used, as this charge pump cannot deliver the current
required for Flash memory programming. The Schottky
diode may not be necessary, depending on the
configuration of the on-demand +12V generator and
whether any other loads are on this line.
September 2006
7
M9999-092106