LTC4558

6

4558f

PIN FUNCTIONS

logic.

tions of the LTC4558.

by ENABLEA and ENABLEB. They can be set to 1.8V or 3V

via the VSELA and VSELB inputs.

CLKA,CKLB (Pins 5, 20): Card Socket. The CLKA,CKLB

pins should be connected to the CLK pins of the respective

card sockets. The CLKA,CKLB signals are derived from the

CLKIN pin. They provide a level shifted CLKIN signal to

the selected card. The CLKA,CKLB pins are gated off until

is deselected, its CLK pin may be left active or brought

LOW using the CLKRUNA, CLKRUNB pins.

RSTA,RSTB (Pins 6, 19): Card Socket. The RSTA,RSTB

pins should be connected to the RST pins of the respec-

tive card sockets. The RSTA,RSTB signals are derived

from the RSTIN pin. When a card is selected, its RST

pin follows RSTIN. The RSTA,RSTB pins are gated off

socket is deselected, the state of its RST pin is latched to

its current state.

I/OA,I/OB (Pins 7, 18): Card Socket. The I/OA,I/OB pins

should be connected to the I/O pins of the respective card

sockets. When a card is selected, its I/O pin transmits/re-

ceives data to/from the DATA pin. The I/OA,I/OB pins are

DATA (Pin 8): Input/Output. Microcontroller side data I/O

pin. The DATA pin provides the bidirectional communication

path to both cards. One of the cards may be selected to

communicate via the DATA pin at a time. The pin possesses

a weak pull-up current source, allowing the controller to

use an open drain output and maintain a HIGH state during

RSTIN (Pin 9): Input. The RSTIN pin supplies the reset

signal to the cards. It is level shifted and transmitted

directly to the RST pin of the selected card.

CLKIN (Pin 10): Input. The CLKIN pin supplies the clock

signal to the cards. It is level shifted and transmitted di-

rectly to the CLK pin of the selected card. If CLKRUNA,B

is HIGH, the clock signal will be transmitted to the CLKA,B

pin, regardless of whether that card is selected, as long

as that card socket is enabled.

ENABLEA, ENABLEB (Pins 11, 17): Inputs. The ENABLEA

and ENABLEB pins enable or disable channel A and chan-

nel B, respectively.

VSELA, VSELB (Pins 12, 16): Inputs. The VSELA and

VSELB pins select the voltage level of each set of SIM/

Smart Card pins. Bringing either of these pins HIGH will

set the output level of its respective channel to 3V. Bring-

ing either of these pins LOW will set the output level of

its respective channel to 1.8V.

CSEL (Pin 13): Input. The CSEL pin selects which set of

SIM/Smart Card pins are active.

CLKRUNA, CLKRUNB (Pins 14, 15): Inputs. The CLKRUNA

and CLKRUNB inputs are used to select whether the clock

signal is always sent to card sockets that are enabled or

whether the clock is gated with the CSEL pin.

Exposed Pad (Pin 21): Ground. This ground pad must be

soldered directly to a PCB ground plane.