MIC2566 Datasheet, PDF (8/10 Pages) Micrel Semiconductor – Single-Slot PC Card/CardBus Power Controller

MIC2566
Applications Information
PC Card V_CC and V_PP control is easily accomplished using
the MIC2566 PC Card/CardBus Slot V_CC and V_PP Power
Controller IC. Four control bits determine V_{CC OUT} and
V_{PP OUT} voltage and standby/operate mode condition. V_CC
outputs of 3.3V and 5V at the maximum allowable PC Card
current are supported. V_{PP OUT} output voltages of V_CC (3.3V
or 5V), 0V or a high impedance state are available. When the
V_CC clamped to ground condition is selected, the device
switches into “sleep” mode and draws only nanoamperes 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 pre-
vents feedback from the V_{CC 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 V_CC.
The MIC2566 operates from the computer system main
power supply. Device logic and internal MOSFET drive is
generated internally by charge pump voltage multipliers
powered from V_CC3 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
MIC2566 is a switch and has no stability problems. For best
results however, bypass V_CC3 IN and V_CC5 IN inputs with 1µF
capacitors to improve output ripple. As all internal device logic
and comparison functions are powered from the V_CC3 IN line,
the power supply quality of this line is the most important, and
a bypass capacitor may be necessary for some layouts. Both
V_{CC OUT} and V_{PP OUT} pins may use 0.01µF to 0.1µF capaci-
tors for noise reduction and electrostatic discharge (ESD)
damage prevention. Larger values of output capacitors are
not necessary.
PC Card Slot Implementation
The MIC2566 is designed for PC Card applications, including
the CardBus option, that do not require a 12V bias. One
MIC2566 is required for each PC Card slot.
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
Micrel
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.
V_CC switches are turned ON and OFF slowly. If commanded
to immediately switch from one V_CC 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. V_PP switches are turned ON slowly
and OFF quickly, which also prevents cross conduction.
If no card is inserted or the system is in sleep mode, the slot
logic controller outputs a (V_CC3 IN, V_CC5 IN) = (0,0) to the
MIC2566, 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.
Internal device control logic and MOSFET drive and bias
voltage is powered from V_CC3 IN. The high voltage bias is
generated by an internal charge pump quadrupler. Systems
without 3.3V may connect V_CC3 IN to 5V. Input logic threshold
voltages are compatible with common PC Card logic control-
lers using either 3.3V or 5V supplies.
Figure 3 shows MIC2566 configuration for situations where
only a single +5V V_CC is available.
Output Current and Protection
MIC2566 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 (millisecond or longer) output
short circuits invoke overtemperature shutdown, protecting
the MIC2566, 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 V_{CC OUT} and
V_{PP 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.
MIC2566
8
May 2003