Nokia RH-128 Service Manual

Also see for 1506: User guide Service manual User guide

Nokia RH-128 Service Manual Manual pdf 97 page image

RH-128Baseband Description and TroubleshootingCOMPANY CONFIDENTIALCopyright © 2009 Nokia. All rights reserved.Page 5-9Issue 1Power UpThe mobile terminal uses the power key and a charger to power up.Power KeyWhen the power key is pressed, the PMU enters the power-up sequence. Pressing the power keycauses the POWER_ON pin to VBAT. The POWER_ON signal is not part of the keypad matrix. Thepower key is connected to the PM. This means that when the power key is pressed, an interrupt will begenerated to the CBP in order to power on the CBP. The CBP reads the PMU IC’s interrupt register andnotifies that it is a KPADPWR_N interrupt. The CBP reads the status of the POWER_ON signal usingthe PMU’s (I2C) control bus. If the POWER_ON signal stays High for a certain time, the CBP acceptsthis as a valid power-on state and continues with the software baseband initialization. If the power keydoes not indicate a valid power-on situation, the CBP powers off the baseband.ChargerCharging is controlled by start-up charging circuitry in order to detect and start charging in case themain battery is not full and the PMU has no supply.Power OffWhile the PS_HOLD signal from the CBP is high, and the PMU IC is in power-on status. The PMUcontinually monitors three events that could trigger a power-off sequence:z The CBP drives the PS_HOLD signal low responding to the pressing of the keypad power button.z Battery voltage drops below power off threshold (Battery Voltage < 3.2 V).z The PMU IC die temperature exceeds its “severe” over-temperature threshold.Clock DistributionThe CBP derives its internal clock from two clock inputs, VC-TCXO and SLEEP_CLK.The main clock signal for the baseband is generated from TCXO.(Temperature-compensated crystal oscillator) The CBP’s TCXO clock input supports the frequency 19.2