STOD2540 PMOLED display power supply Feature summary ■ Inductor switcher boost controller. ■ PFM mode control. ■ High efficiency over wide range of load (1mA to 40mA). ■ Integrated Load disconnect switch. ■ Over voltage protection with automatic restart ■ Soft start with adjustable peak current limit ■ Enable pin ■ Low shutdown current. ■ Small external inductor. ■ Supply voltage from 3.0V to 5.5V STOD2540 is a boost converter that operates from 3.0V to 5.5V and can provide an output voltage as high as 25V. The output current capability is maximum 40mA up to 25V output voltage. The regulation is performed by a resistor divider network (Figure 3.) that detects the output voltage. Application ■ QFN8 (3mm x 3mm) PMOLED display driver Description STOD2540 is dedicated to Passive Matrix OLED (PMOLED) displays for portable handsets and provides the pre-charge and biasing voltage of the column matrix driver as shown in Figure 3. The current capability of STOD2540 allows feeding a 1", 1.3" or 1.5" color PMOLED. In this state-of-the-art boost converter, a DC current path exists between the battery source and the load. In order to reduce the consumption in Shutdown mode, a high-side load isolation switch is necessary to cut this DC current path in Standby mode. The Load Disconnect Switch (LDS) actsas an isolation switch in Shutdown mode. Order codes Part number Package Packaging STOD2540PMR QFN8 (3mm x 3mm) 4500 parts per reel September 2006 Rev. 5 1/19 www.st.com 19 STOD2540 Contents 1 Schematic diagram 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 ......................................... 3 5.1 Boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2 Adjustable peak inductor current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.3 Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.4 OVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.5 Load isolation switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.6 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.7 Under voltage lockout (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1 Demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2/19 STOD2540 Schematic diagram 1 Schematic diagram Figure 1. Block diagram 3/19 Pin configuration STOD2540 2 Pin configuration Figure 2. Pin connections (top view) Table 1. Pin description 4/19 PlN N° SYMBOL NOTE 1 VI 2 RSET Peak inductor current adjust 3 AGND Analog Ground 4 FB Feedback for the LED current regulation 5 VO Output voltage for LED supply 6 VCAP Load Disconnect Switch input 7 ENABLE 8 VSW 9 PGND Supply voltage IC enable signal Boost switch drain Power Ground STOD2540 Maximum ratings 3 Maximum ratings Table 2. Absolute maximum ratings Symbol VBSW, VBO VI RSET EN Parameter Value Unit Breakdown voltage at OUT and SW pin 40 V Supply voltage range 6 V RSET pin VI + 0.3 V Enable pin VI + 0.3 V 2 kV VESD ESD ratings, HBM MIL STD 883C TSTG Storage Temperature Range -65 to 150 °C TOP Operating Junction Temperature Range -40 to 85 °C Value Unit 52 °C/W Table 3. Symbol RthJA Thermal Data Parameter Thermal Resistance Junction-Ambient 5/19 Electrical characteristics STOD2540 4 Electrical characteristics Table 4. Electrical characteristics (TJ = 40°C to 85°C, VI = 3.6V, VEN = 3V, CI = CO = 4.7µF, L = 4.7µH, R1 = 180kΩ, R2 = 10kΩ, VO = 24V, Typ. values @ 25°C, unless otherwise specified). Symbol Parameter VI Input voltage range VO Regulated output voltage VOVP Over voltage protection on output IO Continuous output current ISD Stand-by current IQ Quiescent current consumption RDSON-SW RDSON-LDS Boost switch RDSON Note: 1 Test VI = 3V to 5.5V Peak inductor limit range Note: 1 ILIM-MAX VI + 0.5 25 Max. Unit 5.5 V 35 V 35 VO = 25V V 1 40 VEN = Low, VI = 3.6V 3 VEN = Low, VI = 3V to 4.2V 10 0.4 0.8 VI = 5.5V @ 25°C 0.8 1.2 VI = 4.2V, ISW = 100mA 0.4 mA Ω 40 VO = 25V, IO = 30mA V Ω 2 40 RSET = 10kΩ to 100kΩ mA µA VI = 3V to 4.2V @ 25°C BVDS Breakdown voltage ILIM-ADJ Typ. 3.0 BVDS Breakdown voltage RDSON Note: 1 Min. V 0.2 1.1 A Maximum peak inductor current VI = 3V to 5.5V, RSET = VI Note: 1 0.75 1.2 A Feedback voltage 5% @ 25°C 1.18 1.30 V TON_MAX Maximum ON Time VI = 4.2V 5.5 µs TOFF_MIN Minimum OFF Time VI = 4.2V 300 ns FB Efficiency, VI = 3.6V Note: 1 Eff Efficiency, VI =4.2V Note: 1 Ripple OVHYST 6/19 Output ripple and noise Overvoltage hysteresis IO = 1 mA to 5mA 65 IO = 5 mA to 40mA 70 IO = 1 mA to 5mA 65 IO = 5 mA to 40mA 70 1.24 % VI = 3.6V, IO = 5 mA, VO = 24V 1.3 VI = 3.6V, IO = 30 mA, VO = 24V 1.3 VI = 4.2V, IO = 5 mA, VO = 24V 1.3 VI = 4.2V, IO = 30 mA, VO = 24V 1.3 2 % V STOD2540 Table 4. Electrical characteristics Electrical characteristics (TJ = 40°C to 85°C, VI = 3.6V, VEN = 3V, CI = CO = 4.7µF, L = 4.7µH, R1 = 180kΩ, R2 = 10kΩ, VO = 24V, Typ. values @ 25°C, unless otherwise specified). Symbol Parameter Test Min. Typ. Max. Unit Enable input logic low Disable Low VIL Enable input logic high Enable High VIH Line_VFB Line regulation VFB VI = 3V to 5.5V, IO = 5 mA 5 35 mV Load_VFB Line regulation VFB VI = 3V to 5.5V, IO = 5 mA 5 35 mV VEN Note: 1 0.3 V 1.2 Guaranteed by design. 7/19 Functional description 5 Functional description 5.1 Boost controller STOD2540 STOD2540 is a boost converter operating in PFM (pulsed frequency modulation) mode. The converter monitors the output voltage through the bridge resistor divider R1 and R2 and when the feedback voltage falls below the reference voltage, REF2, the boost switch tSW turns ON and the current ramps up. The inductor current is measured by detect the temperature compensated drain voltage of the boost MOSFET. The boost turns off when its drain voltage reaches the reference REF1, the main switch remains off until the minimum off time (300ns typical) has passed and the feedback voltage is below the reference again. A maximum ON time of 4µs prevent the switch tSW to stay ON during a too long period of time. In order to well calculate the bridge resistors values with a fixed VO, the following formula can be used: 5.2 Adjustable peak inductor current limit The peak inductor current is monitored by sensing the drain voltage of the switch tSW. Since it exceeds the temperature compensated and supply voltage compensated reference REF1, the RS Flip flop is reset and tSW is turned OFF. By connecting a resistance between the pin RSET and GND, the peak current limit can be adjusted from 200mA to 1.1A (RSET from 10kΩ to 100kΩ). When the pin RSET is directly connected to VI, the default value is 1A. 5.3 Enable The ENABLE pin is a high logic input signal and allows turning on/off the controller without cutting the input voltage from the boost regulator circuit. With a high input voltage (1.2V <VEN< VI+0.3V) on this pin, the device is allowed to work normally. No pull-up or pull down is present on this pin. 5.4 OVP If the regulation loop is cut, there is no signal at the feedback pin, the PFM controller will then continue to switch without control and generate an output voltage at the SW, VCAP and VO pin exceeding the breakdown value VBSW, VBCAP and VBO. The Over Voltage Protection (OVP) senses the voltage at the VCAP pin.When the voltage exceed the breakdown voltage of the device the controller is automatically turned Off. A hysteresis control enables the device to automatically restart when the output voltage drops below a 2V typical value. 8/19 STOD2540 5.5 Functional description Load isolation switch When the device is in Shutdown mode, a DC current path always exists between the power source and the load; increasing the standby consumption. A high side switch LDS isolates the load from the source when the STOD2540 is disabled. 5.6 Efficiency The total consumption of some PMOLED display, can be as low as 1mA. In order to increase the battery run time of the device, STOD2540 offers a high efficiency over a wide range of load and input voltage range. 5.7 Under voltage lockout (UVLO) The minimum supply voltage is 3.0 V, under this value the undervoltage lockout circuit operates with typical threshold 2.8V. When supply voltage is below 3.0V, possible noise in the supply line could disturb the UVLO circuit causing loss of output regulation. This behavior is eliminated choosing CI = 10µF or higher. 9/19 Typical application STOD2540 6 Typical application Figure 3. Basic Connection Table 5. External components (see fig. 3 and note) Symbol Parameter Test VRRM D Boost schottky diode Min. Typ. 30 VF at IF = 300mA, TJ = 25°C 0.5 V IR at VR = 10V, TJ = 25°C 30 µA Feedback resistor 180 R2 Feedback resistor 10 Peak current limit adjust IPK = 200mA to 1.1A CI Input ceramic type low ESR Ceramic Type CO Output capacitance: ceramic low ESR L Note: 10/19 Boost inductor (height < 2mm) Unit V R1 RSET Max. 10 kΩ 100 4.7 µF Capacitance 4.7 µF Voltage 42 V ESR 1.6 Ω Inductance 4.7 µH 1 A ISAT, RSET pin to VI The external components suggested in this document should be considered as a design reference guide. The performances mentioned in the electrical characteristics table are not guaranteed for all the possible electrical parameters of the components included in this list. On other hand, the operation of STOD2540 is not limited to the use of components included in this list. STOD2540 Typical application 6.1 Demoboard Figure 4. Suggested demoboard schematic (Top layer view) 11/19 Typical performance characteristics 7 STOD2540 Typical performance characteristics (TJ = 40°C to 85°C, VI = 3.6V, VEN = 3V, CI = CO = 4.7µF, L = 4.7µH, R1 = 180kΩ, R2 = 10kΩ, VO = 24V, Typ. values @ 25°C, unless otherwise specified) Figure 5. Efficiency vs output current Figure 6. Efficiency vs input voltage Figure 7. VEN vs temperature Figure 8. VFB vs input voltage Figure 9. VFB vs output current Figure 10. VFB vs output current 12/19 STOD2540 Typical performance characteristics Figure 11. VOVP vs temperature Figure 12. VRIPPLE vs input voltage Figure 13. ILIM_MAX vs input voltage Figure 14. ILIM_MAX vs temperature Figure 15. ILIM_MAX vs RSET Figure 16. IQ vs temperature 13/19 Typical performance characteristics STOD2540 Figure 17. tON_MAX vs temperature Figure 18. tOFF_MIN vs temperature Figure 19. Line VFB vs temperature Figure 20. Load VFB vs temperature 14/19 STOD2540 8 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. 15/19 Package mechanical data STOD2540 QFN8 (3x3) MECHANICAL DATA DIM. A mm. inch MIN. TYP MAX. MIN. TYP. MAX. 0.80 0.90 1.00 0.032 0.035 0.039 0.03 0.05 0.001 0.002 A1 A2 0.65 0.70 0.75 0.026 0.028 0.030 A3 0.15 0.20 0.25 0.006 0.008 0.010 b 0.29 0.31 0.39 0.011 0.012 0.015 b1 0.17 0.30 0.007 D D2 3.00 1.92 E E2 2.02 0.118 2.12 0.076 3.00 1.11 e 1.21 0.012 0.080 0.084 0.118 1.31 0.044 0.65 0.048 0.052 0.026 K 0.20 0.008 L 0.20 0.29 0.45 0.008 0.011 0.018 L1 0.16 0.24 0.40 0.006 0.009 0.016 L2 0.13 0.005 r 0.15 0.006 r1 0.15 0.006 7517789 16/19 STOD2540 Package mechanical data Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP A MAX. MIN. TYP. 330 13.2 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T MAX. 0.504 0.519 18.4 0.724 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 17/19 Revision history STOD2540 9 Revision history Table 6. Revision history Date Revision 22-Mar-2006 1 Initial release. 03-Apr-2006 2 Add fig. 2 demoboard on page 3. 08-Jun-2006 3 Description in cover page updated. 23-Jun-2006 4 Change range of RSET value and add description paragraph 5.7. 11-Sep-2006 5 Mistake on table 4 Ripple test value 3.6V ==> 4.2V. 18/19 Changes STOD2540 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. 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