MIC2564A Datasheet, PDF (10/16 Pages) Micrel Semiconductor – Dual Serial PCMCIA/CardBus Power Controller Preliminary Information

MIC2564A
Micrel
Applications Information
PC Card power control for two sockets is easily accomplished
using the MIC2564A PC Card/CardBus power controller.
Control commands from a three-wire (plus Reset) serial bus
determine V_CC and V_PP output voltages and select standby
or operate mode.
V_CC outputs of 3.3V and 5V at the maximum allowable PC
Card current are supported. The V_CC outputs also support
GND (0V) and high-impedance states. The V_PP outputs
support V_PP (12V), V_CC voltages (3.3V or 5V), GND (0V), or
high impedance. When the V_CC = Hi-Z (high impedance)
condition is selected, the device switches into sleep mode
and draws only leakage current.
Full protection during hot switching is provided which pre-
vents feedback from the V_CC output (for example, from the 5V
supply into the 3.3V supply) by locking out the low voltage
switch until the initial switch’s gate voltage drops below 0.7V.
MIC2564A internal logic and MOSFET drive circuitry is
powered from the V_CC3 input and internal charge-pump
voltage multipliers. Switching speeds are carefully controlled
to prevent damage to sensitive loads and meet all PC Card
Specification timing requirements, including those for the
CardBus option.
Supply Bypassing
The MIC2564A is a switch and has no stability problems;
however, supply bypass capacitors are recommended to
reduce inductive transients and improve output ripple. As all
internal device logic and comparison functions are powered
from the V_CC3 input, the power supply quality on this line is the
most important. Micrel recommends placing 1µF surface-
mount ceramic (low ESR) capacitors from V_CC3 IN and
V_CC5 IN pins to ground and two 0.1µF surface-mount ceramic
capacitors, one from each V_PP IN pin, to ground. Also, the
V_CC OUT and V_PP OUT pins may use 0.01µF to 0.1µF
capacitors for noise reduction and to reduce the chance of
ESD (electrostatic discharge) damage.
Power Status Feedback (Flags)
Two flag outputs monitor the V_CC and V_PP output voltages on
both slot A and B, falling low when the voltage is not proper.
Use of these open-drain flag outputs is optional; if they are
used, a pull-up resistor to either the 3.3V or 5V supply is
required. Unused flag outputs may be left open.
PC Card Slot Implementation
The MIC2564A is designed for full compatibility with the
Personal Computer Memory Card International Association
(PCMCIA) PC Card Specification including the CardBus and
Zoom Video (ZV) options.
When a PC card is initially inserted, it should receive V_CC
(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
logic controller, which then determines if this card requires
V_PP and if the card is designed for dual V_CC. If the card is
compatible with, and requires, a different V_CC level, the logic
controller commands the power controller to make 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 logic
controller commands the MIC2564A to shut down V_CC. This
also places the switch into a 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 V_CC3 IN. The high voltage bias is generated
by an internal charge pump multiplier. Input logic threshold
voltages are compatible with common PC Card logic control-
lers using either 3.3V or 5V supplies.
PC Card Voltage Regulation
The MIC2564A has been designed to meet or exceed PC
Card voltage regulation specifications. The on-resistance of
the FET switches will meet regulation requirements at 600mA
and 1A respectively for V_CC = 5V ±3% and 3.3V ±3%.
Flash Memory Implementation
When programming flash memory (standard +12V flash
memories), the PC Card slot logic controller enables V_PP on
the MIC2564A, which connects V_PP IN (nominally +12V) to
V_PP OUT. The low on-resistance of the MIC2564A switch
allows using a small bypass capacitor on the V_PP OUT pins,
with the main filtering performed by a large filter capacitor on
V_PP 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 V_PP OUT transition from V_CC to 12.0V typically takes
200µs. After programming is completed, the logic controller
signals to the MIC2564A, which then reduces V_PP OUT to the
V_CC level. Break-before-make switching action and con-
trolled rise times reduce switching transients and lower
current spikes through the switch.
Output Current and Protection
The MIC2564A meets or exceeds all PCMCIA specifications.
MIC2564A output switches are capable of passing the maxi-
mum current needed by any PC Card. For system and card
protection, output currents are internally limited. For full
system protection, long term (longer than a few milliseconds)
output short circuits invoke overtemperature shutdown, pro-
tecting the MIC2564A, the system power supplies, the card
socket pins, board traces, and the PC Card. Individual
internal status registers for each slot indicate when power
problems exist.
Control Bus Interface Overview
The MIC2564A power controller communicates with a logic
controller (host adapter) via a 3-wire serial interface. A fourth
control line attaches to the system reset line (RST#) and
places all MIC2564A switches in the high impedance (off)
state. The reset function is active low.
MIC2564A
10
September 1999