
Analog Integrated Circuit Device Data
Freescale Semiconductor
21
PC34708
General IC Functional Description and Application Information
Functional Description
6.4.1.1
Supply Flow
Refer to the representative tables and text specifying each supply for information on performance metrics and operating ranges.
Table 8 summarizes the available power supplies.
6.4.2
Battery Management
The PC34708 supports power path management, which allows power to the system even in the absence of the battery, or in the
case of a deeply discharged battery. The charger supports charging from a USB host or a wall charger.
The charger interface provides switching operations via an integrated DAC at programmable current levels. It incorporates a
standalone trickle charge mode, in case of a dead battery, with a dual LED indicator driver. Over-voltage, short-circuit, and under-
voltage detectors are included, as well as charger detection and removal. The charger includes the necessary circuitry to allow
for USB charging. The battery management system also provides a battery presence detector and an A to D converter that serves
for measuring the charge current, battery, and other supply voltages, as well as for measuring the battery thermistor and die
temperature. The charger has two charge paths, a main and an aux charge path. Finally, a system is included for monitoring the
current drawn from, or charged into the main battery, for support of a Coulomb Counter function.
6.4.3
Logic
The PC34708 PMIC is fully programmable via the SPI interface and associated register map. Additional communication is
provided by direct logic interfacing, including interrupt, watchdog, and reset. Default startup of the device is selectable by
hardwiring the Power Up Mode Select (PUMS) pins.
Power cycling of the application is driven by the PC34708 PMIC. It has the interfaces for the power buttons and dedicated
signaling interfacing with the processor. It also ensures the supply of the Real Time Clock (RTC), critical internal logic, and other
circuits from the coin cell, in case of brief interruptions from the main battery. A charger for the coin cell is included to ensure that
it is kept topped off until needed.
Table 8. Power Tree Summary
Supply
Purpose (typical application)
Output Voltage (in V)
Load Capability (in mA)
SW1
Buck switcher for processor VDDGP domain
0.650 - 1.4375
2000
SW2
Buck switcher for processor VCC domain
0.650 - 1.4375
1000
SW3
Buck switcher for processor VDD domain and peripherals
0.650 - 1.425
500
SW4A
Buck switcher for DDR memory and peripherals
1.200 – 1.85: 2.5/3.15/3.3
500
SW4B
Buck switcher for DDR memory and peripherals
1.200 – 1.85: 2.5/3.15/3.3
500
SW5
Buck switcher for I/O domain
1.200 – 1.85
1000
SWBST
Boost switcher for USB OTG
5.00/5.05/5.10/5.15
380
VSRTC
Secure Real Time Clock supply
1.2
0.05
VPLL
Quiet Analog supply
1.2/1.25/1.5/1.8
50
VREFDDR
DDR Ref supply
0.6-0.9V
10
VDAC
TV DAC supply, external PNP
2.5/2.6/2.7/2.775
250
VUSB2
VUSB/peripherals supply, internal PMOS
2.5/2.6/2.75/3.0
65
VUSB/peripherals external PNP
2.5/2.6/2.75/3.0
350
VGEN1
General peripherals supply #1
1.2/1.25/1.3/1.35/1.4/1.45/1.5/1.55
250
VGEN2
General peripherals supply #2, internal PMOS
2.5/2.7/2.8/2.9/3.0/3.1/3.15/3.3
50
General peripherals supply #2, external PNP
2.5/2.7/2.8/2.9/3.0/3.1/3.15/3.3
250
VUSB
USB Transceiver supply
3.3
100