Power Distribution Control and Reset

All power (except backup battery power) is drawn from BL5-C Li-Ion battery located in the B cover. Current flows through ZOCUS current sense resister which is used for current measurement by ZOCUS and thus for remaining operating time estimation.

CS7 board contains one power ASIC, UEM and discrete regulators needed for generating the different operating voltages. The discrete regulators consist of an SMPS to power UPPWD2 voltage core and two linear regulators. The first linear regulator provides 2.8V to the SDRAM, LCD and IR module. This regulator and the SMPS regulator are powered at all times and feature low quiescent current consumption modes for sleep mode. The second linear regulator supplies 2.8V to the camera and hardware accelerator only. In addition there is a SMPS in CS7 generating the operating voltage for display module backlighting. In CS7 the keyboard backlight is powered with a charge pump

Power-up sequence (Reset mode)

RESET mode can be entered in four ways: by inserting the battery or charger, by RTC alarm or by pressing the power key. The VCXO is Powered by UEM. After a 220 ms delay regulators are configured and UEM enters PWR_ON mode and system reset PURX is released.

During system start-up, in RESET state, the regulators are enabled, and each regulator charges the capacitor(s) at the output with the maximum current (short circuit current) it can deliver. This results in battery voltage dropping during start-up. When a battery with voltage level just above the hardware cutoff limit is inserted, the system may not start due to excessive voltage dipping. Dropping below 2.8 V for longer than 5 us forces the system to PWR_0FF state.

Powering off

Controlled powering off is done when the user requests it by pressing the power-key or when the battery voltage falls too low. Uncontrolled powering off happens when the battery is suddenly removed or if over-temperature condition is detected in regulator block while in RESET mode. Then all UEM's regulators are disabled immediately and discrete regulators are disabled as Vbat supply disappears.

Controlled powering off

For NHL-8 powering off is initiated by pressing the power key and Power off sequence is activated in UEM and SW. Basically Power key cause UEM Interrupt to UPP_WD2 and SW sets Watchdog time value to zero and as this happens, PURX is forced low and all regulators are disabled.

If the battery voltage falls below the very last SW-cutoff level, SW will power off the system by letting the UEM's watchdog elapse.

If thermal shutdown limit in UEM regulator block is exceeded, the system is powered off. System reset PURXis forced low.

Uncontrolled powering off

This happens when the battery is suddenly removed. UEM's state machine notices battery removal after battery voltage has been below Vcoff- for 5 us and enters PWR_0FF mode. PURX is set low and all UEM's regulators are disabled.

There are three watchdogs in UEM. The first one is for controlling system power-on and power-down sequences. The initial time for this watchdog after reset is 32 s and the watchdog can not be disabled. The time can be set using a register. This watchdog is used for powering the system off in a controlled manner. The other one is for security block and is used during IMEI code setting. The third one is a power key watchdog. It is used to power off the system in case SW is stuck and the user presses the power key. This WD is SW configurable.

There is also a "soft watchdog" in UPP_WD2. It is used to reset the chip in case software gets stuck for any reason. The Bluetooth module also contains a watchdog.

Charging control and charge switch is in UEM. There are two different charging modes; charging empty battery (start-up charge mode), and SW controlled charging.

Watchdogs

Charging

UEM digital part takes care of charger detection (generates interrupt to UPP_WD2), pulse width modulated charging control (for internal charge switch) and over voltage and current detection. SW using registers controls all these.

NHL-8 BB supports a standard charger (two wires), Chargers ACP-8 and ACP-12, Cigarette Charger LCH-8 and LCH-12 are supported.

NHL-8 Battery is a detachable, semi-fixed Lithium-Ion BL5-C battery. Nominal voltage is thus 3.7 V (max charging voltage 4.2 V).

The interface consists of three pins:VBAT, GND and BSI. Pull-down resistor inside ofthe batteries (BSI signal) recognizes the batterytypes. Voltage level at BSI line is measured using UEM's AD-converter.

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DIY Battery Repair

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