Service manual

V1 is a programmable linear regulator. It is programmed through the SPI bus to either
5.0V or 2.775V. For Taichi V1 is programmed to 5.0V and is supplied by
V_BOOST1. This regulator is on whenever the radio is turned on. V1 supplies the
DSC bus.
• V_BOOST1 Switcher Regulator
V_BOOST1 is a switching regulator. At power up pins PMG0 and PMG1 determine
the mode of the switcher. For Taichi V_BOOST1 is programmed to 5.6V because
PMG0 is shorted to B+ and PMG1 is shorted to ground. The regulator is on whenever
the radio is turned on. V_BOOST1 supplies V1 and VSIM.
• V_BUCK Switcher
V_BUCK is a switching regulator. At power up, pins PMG0 and PMG1 determine the
mode of swither. For Taichi V_BUCK is not used.
• PA_DRV Alert/Backlight Regulator
PA_DRV is a programmable linear regulator which drives an external P channel
MOSFET. It is programmed by setting PA_B3-0 to one of 16 codes corresponding to
an output of 2.6V to 7.00V incremented by 0.40V steps. Initially PA_DRV is off until
set via SPI. For Taichi PA_DRV regulates ALRT_VCC to 3.0V (PA_B3-0 = 000).
This regulator is turned on and off by LS3_TX if PA_ON1 is enabled (high).
PA_DRV powers the alert and backlights.
7.4 Battery Charge
Taichi battery
There is a charge control circuit built into Taichi radio. When a battery is
attached and with a external charger insert into the radio through BUTT-
PLUG, the radio will charge the attached battery according to the battery type.
Before describing this radio charger circuitry, lets introduce the battery
package itself.
There is four pins output from battery package: Serial Data, Ground, Power( +
) and Thermister.
SERIAL DATA connection is used by GSM radio to communicate to and
from the internal EEPROM, located inside the battery, to the radio’s
microprocessor. This bi-directional line is used to adjust the operation of the
battery charger and battery meters.
GROUND connection is used as a reference ground for the battery to the
GSM radio.
POWER ( + ) connection provides sufficient voltage to the GSM radio. The
voltage range of a GSM battery ranges from 1.4 volts DC (fully discharged) to
5.1 volts DC (fully charged).