Application information

STOD03A

16/22

DocID17785 Rev 3

7.3

General description

The STOD03A is a high efficiency dual DC-DC converter which integrates a step-up and

inverting power stages 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 STOD03A 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 STOD03A 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.

7.3.1

Multiple operation modes

Both the step-up and the inverting stage of the STOD03A operate in three different modes:

pulse skipping mode (PS), 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 STOD03A works in pulse skipping mode when the load current is below some tens of

mA. The load current level at which this way of operating occurs depends on input voltage

inverting converter.

Discontinuous conduction mode:

When the load increases above some tens of mA, the STOD03A 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 STOD03A enters full CCM at constant switching

frequency mode for each of the two DC-DC converters.

7.3.2

Enable pin

The device operates when the EN pin is set high. If the EN pin is set low, the device stops

switching, and all the internal blocks are turned off. In this condition the current drawn from