sccsp900842/r2 Freescale Semiconductor, Inc, sccsp900842/r2 Datasheet - Page 9

• Manufacturer Part Number: sccsp900842/r2
• Description: Sc900842, Buck-boost Dc-dc And Ldo Power Management Ic
• Manufacturer: Freescale Semiconductor, Inc

synchronous Buck-Boost DC/DC converter and its control
circuit, a linear regulator, and a bandgap voltage reference.
cell, and steps down or up an input voltage range of 2.8 -
the fixed output voltage of 3.3 V. The IC operates in Buck
mode when V
otherwise.
used as a low side synchronous rectifier FET, M4 is on, and
M3 is open
open, M3 is the switching FET, and M4 is the synchronous
rectifier FET.
mode following the variation in the input voltage, V
Buck-Boost converter is compensated internally.
status of the IC:
as a reference and provides a low noise supply. The nominal
regulator output voltage, V
Analog Integrated Circuit Device Data
Freescale Semiconductor
The 900842 consists of an integrated switched-mode
The 900842 is supplied from a single Lithium-Ion battery
The integrated Buck-Boost converter is used to generate
When in Buck mode, M1 is used as a high side FET, M2 is
The IC transitions seamlessly between Buck and Boost
There are 2 output pins that can be used to monitor the
STTS - Status output pin, active low.
ISNS - Current sense pin
The low dropout (LDO) linear regulator uses the bandgap
current limit, or V
STTS = 0 if the output voltage V
STTS =1 if the IC is under thermal shutdown, IC is in
(Figure
IN
is greater that 3.3 V and in Boost mode
2). When in Boost mode, M1 is on, M2 is
OUTP
REGOUT
is too low.
, is 2.775 V and is
OUTP
LOW DROPOUT LINEAR REGULATOR
FUNCTIONAL DESCRIPTION
is up
BUCK/BOOST CONVERTER
IN
. The
INTRODUCTION
4.7 V, to a fixed output voltage of 3.3 V. A high switching
frequency of 1.625 MHz enables the use of small passive
filter components, and improves the dynamic response of the
converter.
current. When PVIN = 3.6 V, a typical ratio is 2.084 V/A.
Current Limiting
overload conditions. If the current through the PMOS power
switch M1 exceeds the I
converter will skip the next cycle. This forces the inductor
current to be reduced to a safe value. The PMOS power
switch M1 is turned on again and the cycle is repeated until
the load current is reduced.
Low Power Mode
system power dissipation at low loads. In Low Power Mode,
the IC operates as an LDO, with a quiescent current of 1mA.
applied to the EN pin. The Low Power Mode can only be
entered after the Buck-Boost has started up in Normal
Operation (EN = 1.8 V).
designed for a steady state maximum current of 100 mA. The
V
currents exceeding the current limit.
REGOUT
The ISNS pin voltage is proportional to the average output
A peak current limit circuit protects the converter during
A Low Power Mode is provided in the IC to minimize
To enter Low Power Mode, a voltage of 1.2 V must be
voltage will decrease when the load demands
LIM33
value, M1 will turn off and the
FUNCTIONAL DESCRIPTION
INTRODUCTION
900842
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