STOD13A STMicroelectronics, STOD13A Datasheet - Page 18

• Manufacturer Part Number: STOD13A
• Description: 250 mA dual DC-DC converter for powering AMOLED displays
• Manufacturer: STMicroelectronics

Detailed description
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Detailed description
General description
The STOD13A 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 STOD13A 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 performances and low noise operation.
The STOD13A 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 STOD13A 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 STOD13A works in pulse skipping mode when the load current is below a few 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 some tens of mA, the STOD13A 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 STOD13A enters in full CCM at constant switching
frequency mode for each of the two DC-DC converters.
Doc ID 022599 Rev 1
STOD13A