User Guide

Technical Documentation
NHD–4
System Module
P.A.M.S
Page 4–32
Original 11/97
AGC Functional Description
Signal Descriptions
Below are descriptions of the signals found within the CDCONT circuitry.
9.8304 MHz
The 9.8304 MHz line is the output of the synthesizer onboard the
CDCONT IC (N201). Measured at C217 this signal should be
approximately 700 mV when measured with an oscilloscope and a high
impedance scope probe. This signal is used to clock the baseband
portions of the phone while operating in CDMA mode.
15.36 MHz
The 15.36 MHz line is the reference frequency input to the synthesizer on
board the CDCONT IC (N201). Measured at the CDCONT side of R319
this signal should be approximately 540 mV when measured with an
oscilloscope and high impedance scope probe. This signal originates
from the VCTCXO (G300).
AGC_REF
This is a PDM voltage used to control the level of attenuation of the
AT–109 (V106). This signal originates at the CDSB ASIC (D704), pin 115.
Measured at this pin, this PDM will vary from 0 to 3.15 V when moved
over its dynamic range. The ASIC side of R701 would be another good
probe point. Be aware that at this node the voltage will still be pulsed AC,
however a true RMS meter will average out the current to provide the
correct DC voltage.
LIM_ADJ
This control signal is the output of the comparator used in the CDMA TX
Gain Limiting control feature. It signals the CDSB ASIC (D704) when the
maximum allowed CDMA TX output power has been achieved. This
signal can be read at C807. When not at the output power limit, this
signal will be logic high at approximately 3.15 V. When the limit has been
reached this signal will toggle low (0.0 V) and high (3.15 V) at a frequency
of approximately 400 Hz.
RFEN 0–2
The three RFE lines determine the mode of the phone. They originate
from the CDSB ASIC (D704) at pins 150, 149, and 134 for RFE0, RFE1
and RFE2 respectively.
RX_GAIN
RX_Gain originates at pin 7 of the CDRFI, and is used for CDMA RX Gain
control.