atr0603 ATMEL Corporation, atr0603 Datasheet - Page 4

• Manufacturer Part Number: atr0603
• Description: Gps Front-end Ic
• Manufacturer: ATMEL Corporation

3.6
3.7
3.8
3.9
4
IF Filter
IF Amplifier
A/D Converter
Clock and Data Driver
ATR0603 [Preliminary]
The mixer directly drives an external LC bandpass filter via open collector outputs. In order to
provide highest selectivity and conversion gain, it is recommended to design the external filter,
according to the application proposal in chapter 10, as a 2-pole filter with a quality factor Q > 25.
The output of the IF filter drives an IF amplifier which is combined with additional low-pass filter-
ing. The gain of this amplifier can be set to three different levels in order to optimally charge the
input of the following analog-to-digital converter for each application.
The gain is internally set to high gain mode but can be adjusted by using external pull-down
resistors at pin 18 (AMP1) and pin 19 (AMP2). If high gain mode is desired, pins 18 and 19 have
to be left floating (see
The analog-to-digital converter stage has a total resolution of 1 bit. It comprises a sub-sampling
unit, clocked by the reference frequency (f
signal (f
selected sub-sampling factor (n = 6) leads to the designated digital output signal, with a center
frequency given by:
f
CMOS output drivers provide the output bit as well as the system clock to the baseband IC. The
amplitude of this signal strongly depends on the value for the digital supply voltage (see
8. ”Electrical Characteristics” on page
OUT
=
OUT
f
IF
), present at the data output SIG, is then given by: f
– f
TCXO
Section 8. ”Electrical Characteristics”
6
=
102.32997 MHz – 16.367667 MHz
7).
TCXO
). The frequency spectrum of the digital output
).
OUT
=
6
= 4.123968 MHz.
f
IF
– f
TCXO
4950B–GPS–11/06
n
Section
. The