This paper presents a wireless power and data transmitter designed for central implanted units (CIUs) in the context of biomedical applications. This CIU is positioned within the human body or brain to supply power from stored battery energy to specific implants, subsequently initiating data communication to send stimulation commands. The core of the system consists of an on-chip implantable relaxation oscillator, for generating the clock signal. This clock signal is then modulated in amplitude and transmitted via a class-E power amplifier through the designed inductive link. Additionally, the CIU is equipped to receive load-shift keying (LSK) uplink data from the implant side and demodulate the data. The proposed system is realized and fabricated using a 180 nm CMOS technology, with a total area of 0.045 mm2. This system enables the simultaneous transmission of power and data utilizing amplitude shift keying (ASK) modulation, operating within the frequency range of 6.78-13.56 MHz. Furthermore, it offers the capability to demodulate uplink data at a rate of up to 1.1 megabits per second (Mbps), achieving a minimum modulation index of 24%.