MIC2562A Ver la hoja de datos (PDF) - Micrel
Número de pieza
componentes Descripción
Lista de partido
MIC2562A Datasheet PDF : 12 Pages
| |||
MIC2562A
Applications Information
PC Card VCC and VPP control is easily accomplished using
the MIC2562A PC Card/CardBus slot VCC and VPP power
controller IC. Four control bits determine VCC OUT and
VPP OUT voltage and standby/operate mode condition. VCC
outputs of 3.3V and 5V at the maximum allowable PC Card
current are supported. VPP OUT output voltages of VCC (3.3V
or 5V), VPP, 0V, or a high impedance state are available.
When the VCC clamped to ground condition is selected, the
device switches into “sleep” mode and draws only nano-
amperes of leakage current. An error flag alerts the user if the
output voltage is too low because of overtemperature or
overcurrent faults. Protection from hot switching is provided
which prevents feedback from the VCC OUT (from 5V to 3.3V,
for example), by locking out the low-voltage switch until the
initial switch’s gate voltage drops below the desired lower
VCC.
The MIC2562A operates from the computer system’s main
power supply. Device logic and internal MOSFET drive is
generated internally by charge pump voltage multipliers
powered from VCC3 IN. Switching speeds are carefully con-
trolled to prevent damage to sensitive loads and meet all PC
Card specification speed requirements.
Supply Bypassing
External capacitors are not required for operation. The
MIC2562A is a switch and has no stability problems. For best
results however, bypass VCC3 IN, VCC5 IN, and VPP IN inputs
with 1µF capacitors to improve output ripple. As all internal
device logic and comparison functions are powered from the
VCC3 IN line, the power supply quality of this line is the most
important, and a bypass capacitor may be necessary for
some layouts. Both VCC OUT and VPP OUT pins may use
0.01µF to 0.1µF capacitors for noise reduction and electro-
static discharge (ESD) damage prevention. Larger values of
output capacitors are not necessary.
PC Card Slot Implementation
The MIC2562A is designed for full compatibility with the
PCMCIA PC Card Specification (March 1995), including the
CardBus option. One MIC2562A is required for each PC Card
slot.
When a memory card is initially inserted, it should receive
VCC (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 VPP and if the card is designed for dual
VCC. If the card is compatible with and desires a different VCC
level, the controller commands this change by disabling VCC,
waiting at least 100ms, and then re-enabling the other VCC
voltage.
VCC switches are turned ON and OFF slowly. If commanded
to immediately switch from one VCC to the other (without
turning OFF and waiting 100ms first), enhancement of the
second switch begins after the first is OFF, realizing break-
before-make protection. VPP switches are turned ON slowly
and OFF quickly, which also prevents cross conduction.
Micrel
If no card is inserted or the system is in sleep mode, the slot
logic controller outputs a (VCC3 IN, VCC5 IN) = (0,0) to the
MIC2562A, which shuts down VCC. 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.
Internal device control logic, MOSFET drive and bias voltage
is powered from VCC3 IN. The high voltage bias is generated
by an internal charge pump quadrupler. Systems without
3.3V may connect VCC3 IN to 5V. Input logic threshold
voltages are compatible with common PC Card logic control-
lers using either 3.3V or 5V supplies.
The PC Card specification defines two VPP supply pins per
card slot. The two VPP supply pins may be programmed to
different voltages. VPP is primarily used for programming
Flash memory cards. Implementing two independent VPP
voltages is easily accomplished with the MIC2562A and a
MIC2557 PCMCIA VPP switching matrix. Figure 3 shows this
full configuration, supporting independent VPP and both 5.0V
and 3.3V VCC operation. However, few logic controllers
support multiple VPP — most systems connect VPP1 to VPP2
and the MIC2557 is not required. This circuit is shown in
Figure 4.
During flash memory programming with standard (+12V)
flash memories, the PC Card slot logic controller outputs a
(0,1) to the EN0, EN1 control pins of the MIC2562A, which
connects VPP IN (nominally +12V) to VPP OUT. The low on
resistance of the MIC2562A switch allows using a small
bypass capacitor on the VPP OUT pins, with the main filtering
action performed by a large filter capacitor on VPP IN (usually
the main power supply filter capacitor is sufficient). Using a
small-value capacitor such as 0.1µF on the output causes
little or no timing delays. The VPP OUT transition from VCC to
12.0V typically takes 250µs. After programming is com-
pleted, the controller outputs a (EN1, EN0) = (0,1) to the
MIC2562A, which then reduces VPP OUT to the VCC level.
Break-before-make switching action and controlled rise times
reduces switching transients and lowers maximum current
spikes through the switch.
Figure 5 shows MIC2562A configuration for situations where
only a single +5V VCC is available.
Output Current and Protection
MIC2562A output switches are capable of passing the maxi-
mum current needed by any PC Card. The MIC2562A meets or
exceeds 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 MIC2562A,
the system power supplies, the card socket pins, and the PC
Card. A final protective feature is the error FLAG, which signals
the PC Card slot logic controller when a fault condition exists,
allowing the controller to notify the user that the card inserted
has a problem. The open-drain FLAG monitors the voltage level
on both VCC OUT and VPP OUT and activates (pulls low) when
either output is 1V below its programmed level or an
overtemperature fault exists.
This FLAG signals output voltage transitions as well as fault
conditions. Refer to Figures 1 and 2 for details.
June 2004
8
M9999-062204
Share Link: 