AD7011

a FEATURES Single +5 V Supply On-Chip ␲/4 DQPSK Modulator Modulator Bypass Analog Mode Root-Raised Cosine Tx Filters, ␣ = 0.35 Two 10-Bit D/A Converters 4th Order Reconstruction Filters Differential Analog Outputs On-Chip Ramp Up/Down Power Control On-Chip Tx Offset Calibration Dual Mode Operation, Analog and Digital Very Low Power Dissipation, 30 mW typical Power Down Mode < 10 ␮ A On-Chip Voltage Reference 24-Pin SSOP APPLICATIONS American Digital Cellular Telephony American Analog Cellular Telephony CMOS, ADC ␲/4 DQPSK Baseband Transmit Port AD7011 GENERAL DESCRIPTION The AD7011 is a complete low power, CMOS, π/4 DQPSK modulator with single +5 V power supply. The part is designed to perform the baseband conversion of I and Q transmit waveforms in accordance with the American Digital Cellular Telephone system (TIA IS-54). The on-chip π/4 Differential Quadrature Phase Shift Keying (DQPSK) digital modulator, which includes the root raised cosine filters, generates I and Q data in response to the transmit data stream. The AD7011 also contains ramp control envelope logic to shape the I and Q output waveforms when ramping up or down at the beginning or end of a transmit burst. Besides providing all the necessary logic to perform π/4 DQPSK modulation, the part also provides reconstruction filters to smooth the DAC outputs, providing continuous time analog outputs. The AD7011 generates differential analog outputs for both the I and Q signals. As it is a necessity for all digital...