STW41412/T ST-Ericsson Inc, STW41412/T Datasheet - Page 19

• Manufacturer Part Number: STW41412/T
• Description: IC CONV DC/DC STPDN 16-TFBGA
• Manufacturer: ST-Ericsson Inc
• Type: Step-Down (Buck)r

Specifications of STW41412/T

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 1.3V, 1.8V
• Current - Output: 200mA, 400mA
• Frequency - Switching: 900kHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TFBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

Functional description
3
Introduction
PWM and PFM mode operation
Current limiter
Short circuit protection
Thermal shutdown protection
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Functional description
The STw4141 is an easy to use, single coil dual outputs step down DC/DC converter
optimized to supply low-voltage to CPUs or DSPs in cell phones and other miniature devices
powered by single cell lithium-ion or 3 cell NiMH/NiCd batteries. It provides two different
output voltages with high efficiency operation in a wide range of output currents. The device
offers high DC voltage regulation accuracy and load transient response to satisfy
demanding processor core supply. The converter is based on voltage mode buck
architecture using PWM and PFM operation modes.
At light load currents, the device can operate in PFM mode to maintain high efficiency over
the entire load current range. Switching between PWM and PFM modes can be done
automatically or can be forced by external pins (AUTO and MODE/SYNC). Externally
synchronized or fixed frequency (internal oscillator) PWM mode offers full output current
capability while minimizing interference to sensitive RF and data acquisition circuits.
PWM (Pulse Width Modulation) mode is intended for normal load to high load currents.
Energy is delivered to the load with an accurate and defined frequency of 900 kHz.
PFM (Pulse Frequency Modulation) mode is intended for low load currents to maintain high
efficiency conversion.
Forced mode: When AUTO pin is LOW, the operating mode is selectable by the user itself.
It means that system controls the behavior of the STw4141 according to processor needs.
STw4141 is switched from PWM to PFM mode using MODE/SYNC pin (refer to
Automatic PWM / PFM switch: When AUTO pin is HIGH, the operating mode is directly
controlled by internal digital circuit according to processor needs. The device switches from
PWM to PFM by itself if sum of output currents is lower than approximately 100 mA during at
least 16 clock cycles. The device can be forced to PWM mode connecting MODE/SYNC to
HIGH level. (see
This protection limits the current flowing through coil. As soon as ILIM is detected, the duty
cycle is terminated and prevents the coil current against rising above peak current limit.
There is no reset of device.
It protects the device against short-circuit at output terminals. When one or both output
voltages are decreased by 0.7 V below their nominal output values the device enters into
reset followed by soft start sequence.
Thermal shutdown protects the device against damage due to overheating when maximum
operating junction temperature is exceeded. The device is kept in reset until junction
temperature decreases by 25°C approximately.
Section 2.8
and
Section 2.9
).
Section 4.1
STw4141
).