Motorola A920 Service Manual page 60

A920: GSM TX VCO
GMSK
Look-up
Table
Mux Delay
Pre-dist
Sys
MAGIC LV
Description
The VCO frequencies are 897 - 1880MHz, handling the three technology bands. The technology bands are controlled by MAGIC_LV via the data lines: N_BAND_0 and
N_BAND_1. CP_TX and GPO3 provides a dual port modulation mode for the TXVCO. N_BAND_0 and N_BAND_1 will select which VCO band will be activated.
GSM_EXC_EN and N_GSM_EXC_EN will enable the buffer stage of U570. TX_EN is activated prior to enabling the buffer and PA. TX_VCO_PRSC is fed back to the
MAGICLV for proper PLL operation. The output frequency for GSM is TX_VCO_LB and PCS / DCS is TX_VCO_HB. The charge pump output (CPTX) from
MAGIC_LV is the input (VT) for the VCO.
GSM_EXC_EN
RF_TOP
N_GSM_EXC_EN
Section
NB_TX_EN
POG
N_BAND_0
N_BAND_1
9 bit
CP_TX
Dual Port
D/A
GPO3
FN
TX_VCO_PRSC
SF_OUT
Q700
Decoder
GSM VCO
Loop Tank
Filter Ckt
DCS/PCS VCO
U700
TXVCO
TX_VCO_LB
TX_VCO_HB