STOD13AS STMicroelectronics, STOD13AS Datasheet - Page 17

• Manufacturer Part Number: STOD13AS
• Description: 250 mA dual DC-DC converter for powering AMOLED display
• Manufacturer: STMicroelectronics

Specifications of STOD13AS

• Typical Efficiency: 85%
• Temperature Range: -40 °C to 85 °C

STOD13AS
8
8.1
8.1.1
8.1.2
8.1.3
8.1.4
Detailed description
General description
The STOD13AS is a high efficiency dual DC-DC converter which integrates a step-up and
inverting power stage suitable for supplying AMOLED panels. Thanks to the high level of
integration it needs only 6 external components to operate and it achieves very high
efficiency using a synchronous rectification technique for each of the two DC-DC converters.
The controller uses an average current mode technique in order to obtain good stability and
precise voltage regulation in all possible conditions of input voltage, output voltage, and
output current. In addition, the peak inductor current is monitored in order to avoid saturation
of the coils.
The STOD13AS implements a power saving technique in order to maintain high efficiency at
very light load and it switches to PWM operation as the load increases in order to guarantee
the best dynamic performance and low noise operation.
The STOD13AS avoids battery leakage thanks to the true-shutdown feature and it is self
protected from overtemperature. Undervoltage lockout and soft-start guarantee proper
operation during startup.
Multiple operation modes
Both the step-up and the inverting stage of the STOD13AS operate in three different modes:
pulse skipping (PSM), discontinuous conduction mode (DCM) and continuous conduction
mode (CCM). It switches automatically between the three modes according to input voltage,
output current, and output voltage conditions.
Pulse skipping operation
The STOD13AS works in pulse skipping mode when the load current is below some tens of
mA. The load current level at which this way of operation occurs depends on input voltage
only for the step-up converter and on input voltage and negative output voltage (VO2) for the
inverting converter.
Discontinuous conduction mode
When the load increases above a few mA, the STOD13AS enters DCM operation. In order
to obtain this type of operation the controller must avoid the inductor current going negative.
The discontinuous mode detector (DMD) blocks sense the voltage across the synchronous
rectifiers (P1B for the step-up and N2 for the inverting) and turn off the switches when the
voltage crosses a defined threshold which, in turn, represents a certain current in the
inductor. This current can vary according to the slope of the inductor current which depends
on input voltage, inductance value, and output voltage.
Continuous conduction mode
At medium/high output loads, the STOD13AS enters full CCM at constant switching
frequency mode for each of the two DC-DC converters.
Doc ID 022733 Rev 1
Detailed description
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