UM0613 User manual Dual DC-DC converter for powering an AMOLED display based on the STOD02 Introduction The STOD02 demonstration board is dedicated to showing the performance of the STOD02 dual DC-DC device, which is used to power AMOLED displays up to 3.0 with an input voltage range from 2.5 to 4.5 V. It integrates a step-up and inverting DC-DC converter, able to deliver the positive and negative voltages needed for the AMOLED panel to operate. Due to the high switching frequency and to the full integration of the synchronous switches, the STOD02 needs very few and small external components, therefore reducing the BOM cost and the PCB area. At the same time, this small size solution does not penalize the overall performance: efficiency stays above 85 % in the most used range of output current and input voltage while very good line and load transients allow the maintaining of a stable output voltage when the input voltage changes rapidly due to series resistance of the battery. The STOD02 works in pulse-skipping mode during low load condition and in PWM mode (at 1.6 MHz) for medium/high load conditions. The Enable pin allows the turning off of the device, therefore reducing the current consumption to less that 1 A. The negative output voltage can be programmed by an MCU through a dedicated pin which implements S-wire protocol. Soft-start with controlled inrush current limit and thermal shutdown are integrated functions of the device. Figure 1. Typical application schematic , 6IN0 6IN ,X IN O 6REF -/,% / 34 9 )30, REF 3 WIRE O %. ,X / 0 . /&& , - V November 2010 Doc ID 15186 Rev 1 1/11 www.st.com 6O 6OContents UM0613 Contents 1 Package description and order codes . 3 2 External component selection . 4 2.1 Input and output capacitor selection 4 2.2 Inductor selection 4 3 Demonstration board BOM and schematic . 5 4 Connector description . 6 5 PCB layout . 7 5.1 Demonstration board PCB layout 7 6 Efficiency results 9 7 Revision history . 10 2/11 Doc ID 15186 Rev 1