User Guide

PAMS
Technical Documentation
NSE–8/9
System Module
Page 2– 44
Issue 1 07/99
CCONT
SIM
BOTTOM CONNECTOR
PSCC
COBBA
BATTERY
PA SUPPLY
RF SUPPLIES
VBB
BASEBAND
VB
VCOBBA
VSIM
VBB
PWM
Vdc_out
PWRONX
PURX
VIN
MAD2PR1
VBB
DC/DC
Converter
Vcore
EEProm
VBB
VBB
PSCC_pwm
Charge_off
LCD
UISwitch
VBB
Ctrl
LED’s
Buzzer
Vibra
Ctrl
RAM
VBB
VBB
Vpp
Flash Rom
Vdc_out
Vcon_1/2
RF reg.
Figure 10. Baseband power Distribution
DC/DC Converter
The DC/DC–converter principal implementation in NSE–8/9 is shown
Figure 11. V105 is the switcher ic, TEA1210 which contains the control
logic together with the switching transistors.
R102, R105 and R112 forms the main voltage divider for the feedback
voltage to the FB pin. The switcher will adjust the output voltage in order
to achieve 1.24V at the FB pin. The two transistors V108a & b forms
together with R113 and R114 a simple 2 bit DAC, which depending upon
the control signals Vcon_1 (LSB) and Vcon_2 (MSB) from the MAD2PR1,
changes the voltage divider. V105 responds by changing Vdc_out in order
to keep the voltage on the FB pin constant.
The voltage control has been implemented to reduce Baseband loss in
idle mode and PA loss at low Tx power levels while achieving better
conversion efficiency due to lower conversion ratio. Additionally at high
power levels it is necessary to increase the output voltage to
accommodate the PA current consumption which exceeds the current
capability of the converter IC.