LTC1756 查看數據表（PDF） - Linear Technology

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LTC1756

Smart Card Interface

Linear Technology 

LTC1755/LTC1756

PI FU CTIO S LTC1755/LTC1756

Note: If a normally closed switch is used, a small current

(several microamperes) will flow through the switch when-

ever a Smart Card is not present. For ultralow power

consumption in shutdown, a normally open switch is

optimum.

DVCC sets the logic reference level for the NC/NO pin.

GND (Pins 5/3): Ground Reference for the IC. This pin

should be connected to a low impedance ground plane.

Bypass capacitors for VIN and VCC should be in close

proximity to the GND pin.

VIN (Pins 6/4): Supply Voltage for the Charge Pump. May

be between 2.7V and 6V. A 10µF low ESR ceramic bypass

capacitor is required on this pin for optimum performance.

VCC (Pins 7/5): Regulated Smart Card Supply Voltage.

This pin should be connected to the Smart Card VCC

contact. The 5V/3V pin determines the VCC output voltage.

The VCC pin is protected against short circuits by compar-

ing the actual output voltage with an internal reference

voltage. If VCC is below its correct level (for as little as 5µs)

the LTC1755/LTC1756 switch to the Alarm state (see the

State Diagram). The VCC pin requires a 10µF charge

storage capacitor to ground. For optimum performance a

low ESR ceramic capacitor should be used.

During the Idle and Alarm states the VCC pin is rapidly

discharged to ground to comply with the deactivation

requirements of the EMV and ISO-7816 specifications.

AUX1 (Pin 8, LTC1755 Only): (Input/Output) Smart Card

Side Auxiliary I/O Pin. This pin is used for auxiliary

bidirectional data transfer between the microcontroller

and the Smart Card. It has the same characteristics as the

I/O pin.

AUX2 (Pin 9, LTC1755 Only): (Input/Output) Smart Card

Side Auxiliary I/O Pin. This pin is used for auxiliary

bidirectional data transfer between the microcontroller

and the Smart Card. It has the same characteristics as the

I/O pin.

I/O (Pins 10/6): (Input/Output) Smart Card Side Data I/O

Pin. This pin is used for bidirectional data transfer between

the microcontroller and the Smart Card. It should be con-

nected to the Smart Card I/O contact. The Smart Card I/O

pin must be able to sink up to 250µA when driving the I/O

pin low due to the pull-up current source. The I/O pin be-

comes a low impedance to ground during the Idle state. It

does not become active until READY goes low indicating

that VCC is stable.

Once READY is low the I/O pin is protected against short

circuits to VCC by current limiting to 5mA maximum.

The DATA-I/O channel is bidirectional for half-duplex

transmissions. Its idle state is H-H. Once an L is detected

on one side of the channel the direction of transmission is

established. Specifically, the side which received an L first

is now the input, and the opposite side is the output.

Transmission from the output side back to the input side

is inhibited, thereby preventing a latch condition. Once the

input side releases its L, both sides return to H, and the

channel is now ready for a new L to be transmitted in either

direction. If an L is forced externally on the output side, and

it persists until after the L on the input side is released, this

illegal input will not be transmitted to the input side

because the transmission direction will not have changed.

The direction of transmission can only be established from

the idle (H-H) state and is determined by the first receipt

of an L on either side.

RST (Pins 11/7): (Output) Level-Shifted Reset Output Pin.

This pin should be connected to the Smart Card RST

contact. The RST pin becomes a low impedance to ground

during the Idle state (see the State Diagram). The reset

channel does not become active until the READY signal

goes low indicating that VCC is stable.

Short-circuit protection is provided on the RST pin by

comparing RST with RIN. If these signals differ for several

microseconds then the LTC1755/LTC1756 switch to the

Alarm state. This fault checking is only performed after the

VCC pin has reached its final value (as indicated by the

READY pin).

CLK (Pins 12/8): (Output) Level-Shifted Clock Output Pin.

This pin should be connected to the Smart Card CLK

contact. The CLK pin becomes a low impedance to ground

during the Idle state (see the State Diagram). The clock

channel does not become active until the READY signal

goes low indicating that VCC is stable.

Short-circuit protection is provided on the CLK pin by

comparing CLK with CIN. If these signals differ for several

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