NCN4555 View Datasheet(PDF) - ON Semiconductor

Part Name

Description

Manufacturer

NCN4555

1.8V / 3V SIM Card Power Supply and Level Shifter

ON Semiconductor 

NCN4555

APPLICATION INFORMATION

CARD SUPPLY CONVERTER

The NCN4555 interface DC−DC converter is a

Low Dropout Voltage Regulator capable of suppling a

current in excess of 50 mA under 1.8 V or 3.0 V. This device

features a very low quiescent current typically lower than

25 mA (Figure 6 and 7). MOD_VCC is a select input

allowing a logic level signal to select a regulated voltage of

1.8 V (MOD_VCC = LOW) or 3.0 V (MOD_VCC = HIGH).

Additionally, the NCN4555 has a shutdown input allowing

it to turn off or turn on the regulator output. The shutdown

mode power consumption is typically in the range of a few

tens of nA (30 nA Typical). Figure 8 shows a simplified

view of the NCN4555 voltage regulator. The SIM_VCC

output is internally current limited and protected against

short circuits. The short−circuit current IVCC is constant

over the temperature and SIM_VCC. It varies with VBAT

typically in the range of 60 mA to 90 mA (Figure 4 and 5).

In order to guarantee a stable and satisfying operating of

the LDO the SIM_VCC output will be connected to a 1.0 mF

bypass ceramic capacitor to the ground. At the input, VBAT

will be bypassed to the ground with a 0.1 mF ceramic

capacitor.

LEVEL SHIFTERS

The level shifters accommodate the voltage difference

that might exist between the microcontroller and the smart

card. The RESET and CLOCK level shifters are

monodirectional and feature both the same architecture.

The bidirectional I/O line provides a way to automatically

adapt the voltage difference between the MCU and the SIM

card in both directions. In addition with the pullup resistor,

an active pullup circuit (Figure 8, Q1 and Q2) provides a fast

charge of the stray capacitance, yielding a rise time fully

within the ISO7816 specifications.

VBAT

Q1

Ilim

R1

SIM_VCC

CIN = 0.1 mF

STOP

+

R2

VREF

COUT = 1.0 mF

MOD_VCC

GND

Figure 8. Simplified Block Diagram of the LDO Voltage Regulator

VDD

SIM_VCC

Q1

18 k

200 ns

Q2

14 k

200 ns

I/O

SIM_I/O

IO/CONTROL

GND

LOGIC

Q3

GND

Figure 9. Basic I/O Line Interface

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