Datasheet

DocID022607 Rev 2 11/22
STOD1317B Detailed description
6 Detailed description
The STOD1317B is a high efficiency DC-DC converter which integrates a step-up and LDO
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.
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 STOD1317B 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.
In order to guarantee very low ripple on the output voltage, the step-up output is filtered by
the LDO. There are two control loops; the LDO control loop regulates V
OUT
in order to
provide the right voltage to the output, while the boost control loop is internally set to provide
and output voltage 380 mV higher than V
OUT
in order to maintain the LDO in regulation at
the minimum possible drop.
The STOD1317B avoids battery leakage thanks to the true-shutdown feature and it is self
protected from overtemperature and short-circuit on the V
OUT
pin. Undervoltage lockout and
soft-start guarantee proper operation during startup.
6.1 BOOST multiple mode of operation
The boost DC-DC operates in three different modes: pulse skipping (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.
6.1.1 Pulse skipping operation
The STOD1317B 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 the input and
output voltage.
6.1.2 Discontinuous conduction mode
When the load increases above some tens of mA, the STOD1317B 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) block senses the voltage across the
synchronous rectifier and turns off the switch 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.
6.1.3 Continuous conduction mode
At medium/high output loads the STOD1317B enters full CCM at constant switching
frequency mode.