User Guide

Technical Documentation
NHD–4
System Module
P.A.M.S
Page 4–34
Original 11/97
VC
VC is the control voltage to the AT–109 variable attenuator. VC will
typically be about 3.8 V when signaling the AT–109 for minimum
attenuation, as it does in AMPS mode operation.
VCO_EN
VCO_EN is better known as the Reset line. It originates at the CDSB
ASIC (D704) pin 128. It terminates at the CDCONT IC (N201) pin 23, the
Reset pin.
DC Voltage Supplies
The CDCONT IC (N201) contains the DC voltage regulators, or supplies,
used to provide DC bias throughout the RF modules of the phone. There
are nine regulators. Voltage regulation is performed within the CDCONT
IC for six of these; VRX90, VRX, VRXS, VTXS, VRXD and VRXA. The
remaining three, VTX, VBBFIL, and VRXD_R have some additional
regulation external to the CDCONT. VBAT, the battery voltage, is the
voltage source. These voltage supplies are turned on and off depending
upon the mode of the phone. The table below details the active supplies
and their approximate voltages for operation in both the AMPS RX/TX
mode and the CDMA RX/TX mode. A shaded box indicates that supply is
on for the respective mode. Test points for voltage measurement of the
respective supplies are also listed.
Mode VBBFIL VNEG VRX VRXA VRXD VRXD_R VRXS VRX90 VTX VTXS
Measurement
point
C224 N200
pin 5
C206 C219 C218 N706
pin 4
C207 C205 C212 C200
AMPS RX/TX
~ 0.0 –4.10 4.45 4.45 1.65 ~ 0.0 4.45 4.45 5.30 4.45
CDMA RX/TX
3.15 –4.10 4.45 1.20 4.45 4.50 4.45 4.45 5.35 4.45
* Values are in volts (V)
VBBFIL
VBBFIL provides bias to the BFILCT2 IC (N2). The VBBFIL voltage
supply circuit uses an external PNP transistor (V203) for regulation. This
supply is on during CDMA RX/TX operation. When VBBFIL is active the
collector of V203 will be approximately 3.15 V, the emitter voltage will be
VBAT, the battery voltage, and the base voltage will be approximately 0.7
V less than the emitter voltage.
VNEG
VNEG is created by the negative voltage generator N200. The VTXS
supply is used as the positive voltage bias from which to generated the
negative voltage. Whenever VTXS is active, VNEG will be present.
VNEG is approximately
– 4.1 V when VTXS is 4.45 V.