ATR0601_06 ATMEL [ATMEL Corporation], ATR0601_06 Datasheet - Page 4

• Manufacturer Part Number: ATR0601_06
• Description: GPS Front-end IC
• Manufacturer: ATMEL [ATMEL Corporation]

3.7
3.8
3.9
4
VGA/AGC
A/D Converter
Clock and Data Driver
ATR0601
The output of the IF-Filter drives an on-chip Variable Gain Amplifier (VGA) which is combined
with additional low-pass filtering. The on-chip Automatic Gain Control (AGC) stage sets the gain
of the VGA in order to optimally charge the input of the following analog-to-digital converter. The
AGC control loop can be selected for on-chip closed loop operation or for external gain control
mode. For external gain control mode, the loop needs to be closed by the baseband IC
ATR0621.
The analog-to-digital converter stage has a total resolution of 1.5 bit. It comprises balanced com-
parators and a sub sampling unit, clocked by the reference frequency (f
spectrum of the digital output signal (f
by: f
digital output signal, with a centre frequency given by:
f
CMOS output drivers are providing 1.5 bit data (SH, SL) and the system clock (SC). The
rail-to-rail output signal level is determined by the digital supply voltage (VDIG).
OUT
OUT
= f
IF
=
– f
XTO
f
IF
– f
4 = 96.764 MHz – 23.104 MHz – 4 = 4.348 MHz.
XTO
n . The selected sub sampling factor (n = 4) leads to the designated
OUT
), present at the data outputs SL and SH, is then given
XTO
). The frequency
4866G–GPS–11/06