STOD14

Detailed description

Doc ID 023562 Rev 1

13/22

7

Detailed description

The STOD14 is a high efficiency dual DC-DC converter which integrates a step-down 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 both the 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 inductor

saturation.

The STOD14 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.

7.1

Mode of operation

To guarantee the minimal output voltage ripple, the device works just in continuous

conduction mode (CCM). In this mode, reverse current pulses flowing back to the power

supply can appear, especially at low load.

7.2

Enable pin

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

stops switching, and all the internal blocks are turned off. In addition, the internal switches

are in an OFF state so the load is electrically disconnected from the input. This avoids

unwanted current leakage from the input to the load.

When the EN is pulled high, the P1 switch is turned on for 100 µs. In normal operation,

7.3

Soft-start and inrush current limiting

technique in order to keep the charge current below 400 mA. This avoids battery

overloading during startup.

After VO1 reaches VINP voltage level, the P1 switch is fully turned on and the soft-start

procedure for the step-down is started.

After around 2 ms the soft-start for the inverting is started. The positive and negative voltage

is under regulation around 6 ms after the Enable pin is asserted high.

7.4

Startup sequence