Analog Integrated Circuit Device Data
Freescale Semiconductor
53
13892
FUNCTIONAL DEVICE OPERATION
Because of an order from the United States International Trade Commission, BGA-packaged product lines and part numbers indicated here currently are not
available from Freescale for import or sale in the United States prior to September 2010: MC13892VK and MC13892VL in 139, 186 MAPBGA packages.
skipping feature improves efficiency by reducing dynamic
switching losses simply by switching less often.
In its lowest power mode, the switcher can regulate using
hysteresis control known as a Pulse Frequency Modulation
(PFM) control scheme. The frequency spectrum will be a
function of input and output voltage, loading, and the external
components. Due to its spectral variance and lighter drive
capability, PFM mode is generally reserved for non-active
radio modes and Deep Sleep operation.
CURRENT LIMITER
A built in current limiter ensures that during normal
operation the maximum current through the coil is not
limiter can be disabled by SPI bits.
SWITCHING FREQUENCY
A PLL generates the switcher system clocking from the
32.768 kHz crystal oscillator reference. To allow for spectral
optimization for reduction of spurious influence in a radion
environment, the PLL can be programmed via SPI from a
multiplication factor of 84 to 105, in steps of 3.
BOOST CONVERTERS
SWBST
SWBST is a boost switching regulator with a fixed 5.0 V
output. It runs at 2/3 of the switcher PLL frequency. SWBST
supplies the VUSB regulator for the USB system in OTG
mode, as well as the VBUS voltage at the UVBUS pin.
When SWBST is configured to supply the UVBUS pin in
OTG mode, the feedback will be switched to sense the
UVBUS pin instead of the SWBSTFB pin. Therefore, when
driving the VBUS for OTG mode, the output of the switcher
may rise to 5.75 V to compensate for the voltage drops in the
internal switches. Note that the parasitic leakage path for a
boost switcher will cause the output voltage SWBSTOUT and
SWBSTFB to sit at a Schottky drop below the battery voltage,
whenever SWBST is disabled. The switching NMOS
transistor is integrated on-chip. An external fly back Schottky
diode, inductor, and capacitor are required.
Figure 8. 13892 SWBST Block Diagram.