S1M8662A Samsung Semiconductor, Inc., S1M8662A Datasheet - Page 12

• Manufacturer Part Number: S1M8662A
• Description: Cdma/pcs/gps Triple Mode If/ Baseband Ic
• Manufacturer: Samsung Semiconductor, Inc.

S1M8662A (Preliminary)
RX IF/BBA WITH GPS
GPS Rx Signal Path
The difference of the S1M8662A from the S1M8656A is that S1M8662A provides GPS receiving operation.
While GPS receiving path shares function blocks with CDMA modes, it needs independent AGC and lowpass
filter.
GPS IF signal from GPS RF-IF mixer is applied to S1M8662A via GPS SAW filter. GPS IF is differential input
pins.
The operation of I/Q demodulator is the same in CDMA modes and the phase relation of I/Q signal of the output
is the same as depicted in Figure 5.
GPS lowpass filter of S1M8662A has its cut off frequency at around 800kHz.
A-D converter, as output of GPS path, is the 4bit parallel converter which is the same one used in CDMA path.
But the sampling frequency is different from that of CDMA mode. And in operating in GPS mode, sampling clock
of A-D converter should be supplied from the modem.
TCXO Clock Generator
In S1M8656A and S1M8660A, the output of TCXO is divided by 1, 2, and 4 and then clocked out. But in
S1M8662A the output of TCXO is just amplified and clocked out. So, there is no SPI control which controls the
division ratio of TCXO clock. In this product, the TCXO_in pin can input both TCXO signal (TCXO_sig) and
TCXO control (TCXO_cont) at the same time.
S1M8662A
Buffer
C
TCXO_sig
TCXO_out
22
x1
9
R
LPF
TCXO_cont
Figure 5. TCXO Clock Generating
If TCXO_cont pin is held low or high-impedance (floating), TCXO_out keeps high, and on the contrary, if
TCXO_cont pin is held high, TCXO_out outputs TCXO clock. If TCXO_cont pin is low or high-impedance
(floating), S1M8662A can be pin to pin compatible with IFR3500 of Qualcomm.
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