The Apple iPhone 3G's GPS uses Infineon PMB 2525 Hammerhead II chip. The chip integrates a A-GPS baseband processor and a low-noise GPS RF front end. It is accurate in 2m at steady state and the Time-to-First Fix (mobile based) is 1 second@5m. High sensitivity, -160dBm for indoor and deep urban operation (cold start, -130 dBm).
Hammerhead II uses serial communication interfaces (UART, SPI, I2C) with speed as low as 38,400 bps. Both A-GPS control software and LBS (Location based services) application executed on host CPU. No additional TCXO required, uses host 32 kHz standby clock & reference clock (10 to 40 MHz)
