DIO74557

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© 2024 Dioo Microcircuits Co.,Ltd. Jiangsu

DIO74557• Rev. 1.5

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Descriptions

Embedded Enable

The embedded enable feature is available for QFN1.8*1.4-10 package. The DIO74557 includes an automatic

enable function that activates the level shifter function when the voltage of VCCB exceeds VCCB_EN. Conversely,

the SIM card side drivers and level shifter function are deactivated as soon as VCCB falls below VCCB_DIS.

Additionally, the IO pin on the host side is set up as an input with a 5 kΩ resistor that is pulled up to VCCA.

When VCCB falls below VCCB_DIS but remains above the MOS threshold voltage (VTH), the pull-down NMOS in the

one-directional and bidirectional drivers will be turned off, while the NMOS controlled by CTL will be turned on.

As a result, the CLK/RST/IO pins on the card side will be pulled low by the 400 Ω resistor. Furthermore, both the

host and card side CLK/RST pins have a 100 kΩ pull-down resistor. The 400 Ω resistor is used for discharge

during VCCB power off (when VTH < VCCB < VCCB_EN), while the 100 kΩ resistor is used to keep RST_SIM/CLK_SIM

low when VCCB is below VTH.

Figure 5. RST/CLK voltage level translation architecture

Figure 6. IO voltage level translation architecture