The SKY74068-21 transmitter is a highly integrated device for dual-band Code Division Multiple Access (CDMA) femtocells. The SKY74068-21 supports femtocells in the cellular CDMA and Personal Communications System (PCS) modes.
The device requires a minimum number of external components to complete a CDMA radio subsystem. Included on-chip are the baseband filter, direct up conversion In-Phase and Quadrature (I/Q) mixers, variable gain power amplifier (PA) drivers, a fully integrated Voltage Controlled Oscillator (VCO) with Local Oscillator (LO) generation blocks, and a dual-mode fractional-N/integer-N Phase Locked Loop (PLL).
External components needed for operation include bias resistors, bypass capacitors, and passives to comprise the PLL loop filter.
The signal enters the chip as an analog baseband I/Q signal. It is filtered by the baseband filter and upconverted to the desired RF transmit frequency. The signal is amplified by one of two upconverters, depending on whether the chip is operating in cellular or PCS mode. The resulting signal is fed through the appropriate PA driver stage to provide variable output power and to drive the external PA. The signal is then filtered by an external Surface Acoustic Wave (SAW) filter and sent to the PA to obtain the final rated power.
- Low power consumption in all operating modes
- Direct up conversion architecture
- Device controlled using a three-wire read/write serial bus interface with independent supply voltage
- Baseband RC filter to reject receive band noise
- Fully integrated VCO with auto-tuning
- Dual-mode fractional-N/integer-N PLL
- Variable gain PA drivers
- Differential cellular driver output matched to 200
- Single-ended PCS driver output matched to 50
- Transmit power control with >75 dB dynamic range
- Low current consumption at low transmit power minimizes current consumption and noise
- Hardware TX_ENABLE for gated mode operation
- RFLGA™ (32-pin, 5 x 5 x 1 mm) package with down set paddle (MSL3, 260 °C per JEDEC J-STD-020)