Inquiry about 6.78MHz operation for wireless power transfer

Dear Engineer,

I purchased the LTC4442 for a wireless power transmission experiment with a frequency of 6.78MHz. In particular, I am using the LTC442 to drive the TX power switch. The LTC4442 works well at frequencies below 500kHz but does not operate above 500kHz. That is, the output of the LTC4442 is not generated even though the square wave(V_Peak=5V) is delivered to the input.

What is the operating frequency range of the LTC4442?

Is the LTC4442 capable of operating at 6.78MHz?

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Other components for LTC4442,

    - Switches : ZXMN6A11Z (60V N-CHANNEL ENHANCEMENT MODE MOSFET)

    - Diode : PMEG3050EP (A low VF MEGA Schottky barrier rectifier)

    - Capacitor : 0.22uF (SMD Type)

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Thank you.