SAA1575HL Datasheet, PDF (3/56 Pages) NXP Semiconductors – Global Positioning System GPS baseband processor

Philips Semiconductors
Global Positioning System (GPS)
baseband processor
Product specification
SAA1575HL
1 FEATURES
• Single-chip GPS baseband solution with built-in 16-bit
microcontroller
• All digital, 0.5 micron CMOS technology
• Single power supply with full 3 V operation
• Separate I/O power supply pins for operation with
3 or 5 V external devices
• Up to 30 MHz system clock from on-chip crystal
oscillator or external clock input
• 2 kbytes words internal data memory for fast execution
• External bus for up to 512 kbytes words data memory
and 512 kbytes words program memory
• Programmable external bus timing to match external
memory speed
• Chip selection outputs to reduce glue logic requirements
• Reset controller for power-down detection and servicing
• 8 GPS channel correlators driven by firmware for
flexible GPS correlation algorithms
• 1 second pulse output of GPS time
• 2-bit digital IF GPS signal input synchronized to external
sample clock
• 2 fully duplex UARTs for communication with host
system processor and other devices
• Real-time clock with 32.768 kHz crystal and supply for
low power timekeeping
• Watchdog timer
• Power-down modes under firmware control
• 100-pin LQFP package
• 50 mA supply current (typ.) when 8 GPS channels in
track (approximate).
2 GENERAL DESCRIPTION
The SAA1575HL is an integrated circuit which implements
a complete baseband function for Global Positioning
System (GPS) receivers. It combines a 16-bit Philips
80C51XA microcontroller, 8 GPS channel correlators and
related peripherals in a single IC. Users can implement a
complete GPS receiver using only the SAA1575HL, the
UAA1570HL front-end Philips IC (or similar), external
memory and a few discrete components.
The IC is aimed at low cost applications. A low power
solution was also used where possible, although this was
of secondary importance to cost. The core of the
SAA1575HL operates at 3 V.
However, for compatibility with current automotive
applications, the periphery is supplied from separate pins
and can be operated between 3 and 5 V, as required.
The function of the SAA1575HL is to read the 1 or 2-bit
sampled IF bitstream from a front-end IC and, under
control of firmware on an external ROM, calculate the full
GPS solution. The results are communicated to a host in
National Maritime Electronics Association (NMEA) format
via a standard serial port. A second serial port can be used
to provide differential GPS information to the processor for
more advance applications. In addition, various other
functions are integrated onto the IC such as a real-time
GPS clock, a power-down/reset controller, timer/counters
and a watchdog timer.
To summarise, the SAA1575HL has the following
functional units:
• 16-bit 80C51XA microcontroller core
• 2 kbytes words on-chip SRAM (16-bit words)
• 8 GPS channel correlators
• 2 UARTs
• 8 general purpose I/O lines
• 3 timer/counters
• 1 real-time clock
• 1 watchdog timer
• 1 power-down/reset controller.
The structure is based on a 16-bit microcontroller core
operating on all other units as memory mapped
peripherals and registers. A 16-bit data bus and a 19-bit
address bus are extended to external pins so that external
data and program memory can be accessed. On-chip
decoder circuits eliminate the need for external glue logic
for external memory access.
Each of the 8 GPS channel correlators includes a carrier
Numerically Controlled Oscillator (NCO), PN code
generator, phase rotator and low-pass filter. They
correlate the local PN sequence with the digitized input
GPS signal and generate the filtered correlation result for
the microcontroller. The firmware provided then generates
a navigation solution and provides standard GPS data
outputs to the user.
1999 Jun 04
3