K850
1203-2528 rev. 1
FUNCTIONAL OVERVIEW
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Charger Control
A programmable charger is used for battery charging.
Limits can be set for the output voltage at CHSENSE- and the output current from DCIO
through the sense resistor to CHSENSE-.
The programmable charger is enabled or disabled by the assertion/negation of the external
signal DCIO. Parts of the programmable charger are activated and deactivated depending on
the level of VBAT. The rest of the programmable charger is activated and deactivated through
I2C.
The programmable charger supports the following functions:
• Constant current charging
• Constant voltage charging
• Trickle charging
• PWM controlled charging
• Over-voltage and over current detection
• Watchdog termination
• DCIO assertion/removal detection
• Voltage and current measure functions
• Low resistive path (reverse mode)
The programmable charger is able to control the voltage and limit the current to a load seen at
CHSENSE-. The programmable charger can also be run in PWM mode to turn the charging on
and off in accordance with the particular period and duty cycle. When the charging is on, it is
set to the current and voltage selected by I2C. A low resistive path from VBAT to DCIO can be
formed when DCIO is not detected. When this setting is done in the appropriate registers, a
lowering of CHREG to 0 V turns on the external pass device. The pass device is automatically
turned off when an external source is detected on DCIO, or when the watchdog termination
block times out. The watchdog termination block must be active when the external switch is
enabled, both in normal charging mode and in the low resistive path mode. The watchdog is set
through the serial interface, and if it has not been set again before timeout, the watchdog turns
off the external switch. The watchdog is disregarded during trickle charging. When no battery is
present, the system can be booted and supplied from DCIO by applying the correct voltage on
DCIO.
USB Charger
The analog baseband controller contains a standalone USB charger. The USB charger has a
separate input and incorporates full functionality during low VBAT.
The programmable charger supports the following functions:
• Trickle charging
• Constant current charging
• Watchdog termination
• Trickle LED indication
• VBUS assertion/removal detection
Resistance Identification and Temperature Measurement
The resistance identification mode utilizes the constant current source to feed the battery data
output while monitoring the voltage at the battery data node with general purpose ADC. The
conversion is started through I2C.
Resistance Identification (A) and Temperature Measurement (B)
SIM Interface
The SIM interface supplies level shifting between the digital baseband controller and the
SIM/USIM card. Moreover, hard-wired SIM deactivation functionality manages removal of a SIM
card that has not been powered down.
Block Diagram of the SIM Interface.
CODEC Overview
The CODEC is encoding analog audio signals and analog voice signals into digital signals using
ADCs. This is done in the coder section of the CODEC, also named the TX path (transfer
section). The CODEC is also decoding digital audio signals and digital voice signals into analog
signals using DACs. This is done in the decoder section of the CODEC, also named the RX path
(receiver section).
Technical Description
SEMC Troubleshooting Manual
64
(101)
