RT8509

RT8509 RICHTEK | Alldatasheet

Document overview

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Technical content

Features

zzzzz 90% Efficiency zzzzz Adjustable Output Up to 24V zzzzz 2.8V to 14V Input Supply Voltage zzzzz Input Supply Under Voltage Lockout zzzzz Fixed 1.2MHz Switching Frequency zzzzz Programmable Soft-Start zzzzz VOUT Over Voltage Protection zzzzz Over Temperature Protection zzzzz Thin 10-Lead WDFN Package zzzzz RoHS Compliant and Halogen Free

Applications

H4= : Product Code YMDNN : Date Code Typical Application Circuit COMP FB GND GND SS VIN VSUP LX LX EN GND H4=YM DNN LX RT8509VIN EN VSUP FB SS COMPGND Chip Enable COUT VOUT 18V CSS 6, 7 CIN VIN 12V 4, 5, 11 (Exposed Pad) 10µF x 2 1µF 4.7µH 134k 10k 4.7µF x 3 33nF 56k 1nF 1µF Package Type QW : WDFN-10L 3x3 (W-Type) RT8509 Lead Plating System G : Green (Halogen Free and Pb Free)

DS8509-01 March 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Functional Pin Description Pin No. Pin Name Pin Function 1 COMP Compensation Pin for Error Amplifier. Connect a series RC from COMP to ground. 2 FB Feedback. The FB regulation voltage is 1.25V nominal. Connect an external resistive voltage divider between the step-up regulator’s output (V OUT) and GND, with the center tap connected to FB. Place the divider close to the IC and minimize the trace area to reduce noise coupling. 3 EN Chip Enable. Drive EN low to turn off the Boost. 4, 5, 11 (Exposed Pad) GND Ground. The Exposed Pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 6, 7 LX Switch. LX is the drain of the internal MOSFET. Connect the inductor/rectifier diode junction to LX and minimize the trace area for lower EMI. 8 VSUP Boost Converter Over Voltage Protection Input. Bypass VSUP with a minimum 1 μF ceramic capacitor directly to GND. 9 VIN Supply Input . Bypass VIN with a minimum 1 μF ceramic capacitor directly to GND. 10 SS Soft-Start Control. Connect a soft-start capacitor (C SS) to this pin. The soft-start capacitor is charged with a constant current of 5 μA. The soft-start capacitor is discharged to ground when EN is low. Function Block Diagram Soft Start Control and Driver Logic Current Sense Protection Slope CompensationOscillator OVP LX OTP Error Amplifier VDD 1.25V FB COMP EN VIN VSUP Summing Comparator LX SS GNDClock

DS8509-01 March 2012 www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.

Electrical Characteristics

Recommended Operating Conditions (Note 4) Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 2) z ESD Susceptibility (Note 3) (VIN = 3.3V, VOUT = 10V, TA =25°C unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Supply Current Input Voltage Range V IN 2.8 -- 14 V Output Voltage Range VOUT -- -- 24 V Under Voltage Lockout Threshold VUVLO V IN Rising -- 2.5 3 V UVLO Hysteresis ΔVUVLO -- 200 -- mV VFB = 1.3V, LX Not Switching -- 1 -- VIN Quiescent Current IQ VFB = 1V, LX Switching -- 5 -- mA Thermal Shutdown Threshold TSD Temperature Rising -- 155 -- °C Thermal Shutdown Hysteresis ΔTSD -- 10 -- °C VSUP Over Voltage Threshold VSUP Rising -- 26 -- V Oscillator Oscillator Frequency fOSC 1000 1200 1500 kHz Maximum Duty Cycle DMAX -- 90 -- % Error Amplifier FB Regulation Voltage VREF -- 1.25 -- V FB Input Bias Current IFB -- -- 100 nA FB Line Regulation -- 0.05 0.2 %/V

DS8509-01 March 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Parameter Symbol Test Conditions Min Typ Max Unit Transconductance gm ΔI = ±2.5μA at VCOMP = 1V -- 100 -- μA/V Voltage Gain AV FB to COMP -- 700 -- V/V N-MOSFET Current Limit ILIM 3 3.5 -- A On-Resistance RDS(ON) -- 100 250 mΩ Leakage Current ILEAK V LX = 24V -- 30 45 μA Current Sense Transresistance RCS -- 0.25 -- V/A Soft-Start Charge Current -- 5 -- μA Control Inputs Logic-High VIH 1.5 -- -- EN Input Voltage Logic-Low VIL -- -- 0.5 V Note 1. Stresses beyond those listed “Absolute Maximum Ratings ” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θ JA is measured at T A = 25 °C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.

DS8509-01 March 2012 www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Boost Reference Voltage vs. Input Voltage 1.1 1.2 1.3 1.4 1.5 2 4 6 8 1 01 21 4 Input Voltage (V) Boost Reference Voltage (V) Boost Current Limit vs. Input Voltage 2468 1 0 1 2 1 4 Input Voltage (V) Boost Current Limit (A) Typical Operating Characteristics Boost Efficiency vs. Load Current 100 Load Current (A) Boost Efficiency (%) VOUT = 18V, fOSC = 1.2MHz VIN = 14V VIN = 12V VIN = 10V Boost Efficiency vs. Load Current 100 Load Current (A) Boost Efficiency (%) VOUT = 13.5V, fOSC = 1.2MHz VIN = 3.3V VIN = 5V Boost Reference Voltage vs. Temperature 1.1 1.2 1.3 1.4 1.5 -50 -25 0 25 50 75 100 125 Temperature (°C) Boost Reference Voltage (V) VIN = 3.3V Boost Frequency vs. Temperature 900 1000 1100 1200 1300 1400 -50 -25 0 25 50 75 100 125 Temperature (°C) Boost Frequency (kHz ) VIN = 3.3V

DS8509-01 March 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.

Application Information

The RT8509 is a high performance step-up DC/DC converter that provides a regulated supply voltage for panel source driver ICs. The RT8509 incorporates current mode, fixed frequency, Pulse Width Modulation (PWM) circuitry with a built in N-MOSFET to achieve high efficiency and fast transient response. The following content contains detailed description and information for component selection. Boost Regulator The RT8509 is a current mode boost converter integrated with a 24V/3.5A power switch, covering a wide V IN range from 2.8V to 14V. It performs fast transient responses to generate source driver supplies for TFT LCD display. The high operation frequency allows use of smaller components to minimize the thickness of the LCD panel. The output voltage can be adjusted by setting the resistive voltage-divider sensing at the FB pin. The error amplifier varies the COMP voltage by sensing the FB pin to regulate the output voltage. For better stability, the slope compensation signal summed with the current sense signal will be compared with the COMP voltage to determine the current trip point and duty cycle. Soft-Start The RT8509 provides soft-start function to minimize the inrush current. When powered on, an internal constant current charges an external capacitor. The rising voltage rate on the COMP pin is limited from V SS = 0V to 1.24V and the inductor peak current will also be limited at the same time. When powered off, the external capacitor will be discharged until the next soft-start time. The soft-start function is implemented by the external capacitor with a 5μA constant current charging to the soft- start capacitor. Therefore, the capacitor should be large enough for output voltage regulation. A typical value for soft-start capacitor is 33nF. The available soft-start capacitor range is from 10nF to 100nF. If C SS < 220pF, the internal soft-start function will be turned on and period time is approximately 1ms. OUT REF REF R1V = V x 1 , where V = 1.25V (typ.)R2 The recommended value for R2 should be at least 10kΩ without some sacrificing. Place the resistive voltage divider as close as possible to the chip to reduce noise sensitivity. Loop Compensation The voltage feedback loop can be compensated with an external compensation network consisting of R3. Choose R3 to set high frequency integrator gain for fast transient response and C1 to set the integrator zero to maintain loop stability. For typical application, V IN = 5V, VOUT = 13.6V, COUT = 4.7μF x 3, L1 = 4.7 μH, while the recommended value for compensation is as follows : R3 = 56kΩ, C1 = 1nF. Over Current Protection The RT8509 boost converter has over current protection to limit the peak inductor current. It prevents large current from damaging the inductor and diode. During the On-time, once the inductor current exceeds the current limit, the internal LX switch turns off immediately and shortens the duty cycle. Therefore, the output voltage drops if the over current condition occurs. The current limit is also affected by the input voltage, duty cycle, and inductor value. Over Temperature Protection The RT8509 boost converter has thermal protection function to prevent the chip from overheating. When the junction temperature exceeds 155°C, the function shuts down the device. Once the device cools down by approximately 10°C, it will automatically restart to normal operation. To guarantee continuous operation, do not operate over the maximum junction temperature rating of 125°C. Inductor Selection The inductance depends on the maximum input current. As a general rule, the inductor ripple current range is 20% to 40% of the maximum input current. If 40% is selected Output Voltage Setting The regulated output voltage is shown as the following equation :

©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. it will increase with temperature. The output capacitor, COUT, should be selected accordingly. Figure 1. The Output Ripple Voltage without the 10μF capacitor is sufficient for most applications.

DS8509-01 March 2012 www.richtek.com Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnish ed by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringeme nts of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of R ichtek or its subsidiaries. Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 2.950 3.050 0.116 0.120 D2 2.300 2.650 0.091 0.104 E 2.950 3.050 0.116 0.120 E2 1.500 1.750 0.059 0.069 e 0.500 0.020 L 0.350 0.450 0.014 0.018 W-Type 10L DFN 3x3 Package 1 122 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. DETAIL A Pin #1 ID and Tie Bar Mark Options D E A L be SEE DETAIL A