SEA05TR

SEA05 Advanced constant voltage and constant current controller Features ■ Constant voltage and constant current control ■ Wide operating VCC range [3.5 - 36] V ■ Low quiescent consumption: 200 µA ■ Voltage reference: 2.5 V ■ Voltage control loop accuracy +/- 0.5% ■ Current sense threshold: 50 mV ■ Open-drain output stage ■ Low external component count ■ SOT23-6L micro package SOT23 - 6L adequately rated in terms of power dissipation; the frequency compensation components (R-C networks) for both loops. The device, housed in one of the smallest available package, is ideal for space-shrunk applications such as adapters and chargers. Applications ■ Battery chargers ■ AC-DC adapters ■ LED drivers   Figure 1. Internal schematic Description 1.23 V The SEA05 is a highly integrated solution for SMPS applications requiring a dual control loop to perform CV (constant voltage) and CC (constant current) regulation. The voltage reference, along with one op-amp, is the core of the voltage control loop; the current sensing circuit and the other op-amp make up the current control loop. The external components needed to complete the two control loops are: a resistor divider that senses the output of the power supply and fixes the voltage regulation setpoint at the specified value; a sense resistor that feeds the current sensing circuit with a voltage proportional to the dc output current; this resistor determines the current regulation setpoint and must be + + - The device integrates a voltage reference, two opamps (with OR-ed open-drain outputs), and a lowside current sensing circuit. April 2010 Vcc 6 2.5 V Table 1. 5 Out 3 Vctrl 2 Gnd 4 1 Ictrl Isense Device summary Order code Package Packing SEA05TR SOT23-6L Tape and reel Doc ID 17014 Rev 1 1/10 www.st.com 10 Pin description 1 SEA05 Pin description Figure 2. Pin configuration   Note: 1 6 Vcc GND 2 5 Out Vctrl 3 4 Ictrl The adjacent pins have the same AMR to increase the robustness of the IC against accidental short circuit among pins. Table 2. 2/10 Isense Pin description n. Name Function 1 Isense Inverting input of the current loop op-amp. The pin is tied to the cold end of the current sense resistor through a decoupling resistor. 2 GND Ground. Return of the bias current of the device. 0 V reference for all voltages. The pin should be tied as close to the ground output terminal of the converter as possible to minimize load current effect on the voltage regulation setpoint. 3 Vctrl Inverting input of the voltage loop op-amp. The pin is tied to the mid-point of a resistor divider that senses the output voltage. 4 Ictrl Non-inverting input of the current loop op-amp. It is tied directly to the hot (negative) end of the current sense resistor 5 OUT Common open-drain output of the two internal op-amps. The pin, able to sink current only, is connected to the branch of the optocoupler’s photodiode to transmit the error signal to the primary side. 6 Vcc Supply Voltage of the device. A small bypass capacitor (0.1 µF typ.) to GND, located as close to IC’s pins as possible, might be useful to get a clean supply voltage. Doc ID 17014 Rev 1 SEA05 2 Maximum ratings Maximum ratings Table 3. Absolute maximum ratings Symbol Pin Vcc 6 Vout Value Unit Dc supply voltage -0.3 to 38 V 5 Open-drain voltage -0.3 to Vcc V Iout 5 Max sink current 20 mA Ictrl 4 Analog input -0.3 to Vcc V Isense 1 Analog input -0.3 to 3.3 V Vctrl 3 Analog input -0.3 to 3.3 V Value Unit 250 °C/W Table 4. Parameter Thermal data Symbol 3 Parameter RthJA Thermal resistance, junction-to-ambient Tjop Junction temperature operating range -40 to 150 TSTG Storage temperature -55 to 150 °C Typical application schematic Figure 3. Typical application schematic 0.1μF Vcc 1.23 V + - 0V 5 Out 3 Vctrl + - 4 -50 mV R1 6 2.5 V 2 Gnd R2 1 Ictrl Vo Isense Vcsth Rsense Io VO = Doc ID 17014 Rev 1 R1 + R2 * 2.5 V R2 IO max = 0 .05 V R sense 3/10 Electrical characteristics 4 SEA05 Electrical characteristics -25 °C