DS9535A RICHTEK | Alldatasheet
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Technical content
Features
Fast Charging for Li-Ion, NiMH and NiCd Batteries Adjustable Battery Voltages from 2.5V to 22V High Efficiency : Up to 95% Charging Current Programmed by Resistor Precision 0.5% Charging Voltage Accuracy Provide 5% Charging Current Accuracy 500kHz Switching Frequency Auto Shutdown with Adapter Removal
Applications
Notebook Computers Portable Instruments Chargers for Li -lon, NiMH, NiCd and Lead Acid Rechargeable Batteries Simplified Application Circuit VFB RT9535A V5V BOOT HSD SW SNSH SNSL BATT GND VFB VC ISET VIN EN SS VHH VHH NTC PGND CIN VIN D2 D3 RNTC RS3 RS2 RS1 To RS3 VHH CBATT RF2 RF1 VBATT To VFB C11 C10
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016
Ordering Information
QW : WQFN-16L 4x4 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) RT9535A Note : Richtek products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes Pin Configurations (TOP VIEW) EN SS ISET VC NTC VFB VHH BATT SW PGND SNSL SNSH HSD V5V VIN BOOT 5 6 7 8 1316 1415 GND WQFN-16L 4x4 Marking Information 1Y=YM DNN 1Y= : Product Code YMDNN : Date Code
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com Functional Pin Description Pin No. Pin Name Pin Function 1 EN Enable Control Input (Active High). It must be connected to a logical voltage or pulled up to VIN with a 100k resistor. 2 SS Soft-Start Control Input. SS controls the soft -start time. Connect a capacitor from SS pin to GND to set the soft-start time. 3 ISET Charge Current Setting and System Loop Compensation Pin. Connect a resistor from this pin to ground to set the charge current. 4 VC Control Signal of the Inner Loop of the Current Mode PWM. A capacitor of at least 0.1F with a serial resistor to GND filters out the current ripple. 5 NTC Input for an external NTC thermistor for battery temperature monitoring. 6 VFB Battery Voltage Feedback. Using an external resistor divider to set battery full charge voltage.
7 VHH
To supply the current sense amplifier CA for very low dropout condition. It must be connected as shown in the typical application circuit or connected to VIN if VIN is always larger than BATT by at least 1.8V. 8 BATT Battery Voltage Sensing Input . A 10 F or larger X5R ceramic capacitor is recommended for filtering charge current ripple and stability purpose. 9 SNSL Negative Terminal for Sensing Charge Current. 10 SNSH Positive Terminal for Sensing Charge Current. 11 PGND Power Ground. 12 SW Switch Node. This pin switches between ground and VIN with high dv/dt rates. Care needs to be taken in the PC B layout to keep this node from coupling to other sensitive nodes. 13 HSD Drain of Internal High-Side Power N-MOSFET Switch. Connect a low ESR capacitor of 10F or higher from this pin to ground for good bypass.
14 BOOT Bootstrap Supply for the High-Side Power Switch Gate Driver and Control
Circuitry. In normal operation, VBOOT ≈ VSW + 5V. 15 VIN Input Power Supply. Connect a low ESR capacitor of 10F or higher from this pin to ground for good bypass. 16 V5V Output of Internal 5V LDO. Connect a 1 F ceramic capacitor from this pin to GND for stability. (Exposed Pad) GND Exposed Pad. Connect the exposed pad to PGND.
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Function Block Diagram VREF 2.5V R S EA VA CA PWM LDO + C2 VIN IVA ICHG EN 1.4VR1 200k UVLO SLOP COMPICHG 0.4V SD COUNTER 1.3V 3.9V SNSH SNSL BATT ISET VC PGND VHH SW HSD BOOT 0.5uA5V VIN C3 REFERENCE VREF 2.5V OSCILLATOR UVLO VIN VFB THERMISTOR NTC SS Soft-StartGND V5V 2.5V VREF
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com Operation The RT9535A is a current mode PWM step -down switching charger controller. The battery DC charge current is programmed by a resistor R4 at the ISET pin and the ratio of sense resistor RS2 over RS1 in the typical application circuit. Amplifier CA converts the charge current through RS1 to a much lower sampled current I CHG (ICHG = IBATT x RS1 / RS2) fed into the ISET pin. Amplifier EA compares the output of CA with 2.5V reference voltage and drives the PWM loop to force them to be equal. Note that ICHG has both AC and DC components. High DC accuracy is achieved with averaging filter R3 and C3 at ISET pin. ICHG is mirrored to go through R4 and generates a ramp signal that is fed to the PWM control comparator, forming the current mode inner loop. An internal LDO generates a 5V to power high-side MOSFET gate driver. For batteries like lithium that require both con stant current and constant voltage charging, the 0.5% 2.5V reference and the voltage amplifier VA reduce the charge current when battery voltage reaches the normal charge voltage level. For NiMH and NiCd, VA can be used for over -voltage protection.
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Absolute Maximum Ratings (Note 1) Power Dissipation, PD @ TA = 25C Package Thermal Resistance (Note 2) ESD Susceptibility (Note 3) Recommended Operating Conditions (Note 4)
Electrical Characteristics
(VIN = VBAT + 3V, VBAT is the full charge voltage, pull-up EN to VIN with 100k resistor, TA = 25C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Overall Supply Quiescent Current IQ No Charge Current 0.5 1.3 2 mA Supply Shutdown Current ISD VEN = 0 -- -- 12 A Reverse Current from Battery IREV VIN Floating, VEN = 0 VBATT = VSW = VSNSH = VSNSL = 20V -- -- 10 A VIN Under-Voltage Lockout VUVLO 3.6 3.8 4.3 V VIN Under-Voltage Lockout Hysteresis VUVLO_HYS -- 300 -- mV Reference Reference Voltage VFB 2.486 2.5 2.514 V FB Bias current IFB VFB = 2.5V -- -- 0.1 A
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com Parameter Symbol Test Conditions Min Typ Max Unit Charge Current Full-Scale Charge Current Sense Voltage VICHG Measure the Voltage Drop Across RS1 95 100 105 mV ISET Output Current IISET −1 -- -- mA SNSL Bias Current ISNSL No Charge Current −36 −12 −6 A SNSH Bias Current ISNSH No Charge Current −36 −12 −6 A Battery Voltage VHH Minimum Voltage with Respect to BATT VHH -- -- 2 V VIN Minimum Voltage with Respect to BATT VDROP (Note 5) -- 0.3 0.4 V VHH Input Current IVHH VHH = 28V 40 95 150 A BATT Bias Current IBATT VEN = 0, VBATT = VSW = VSNSH = VSNSL = 20V -- -- 10 A VC Pin Current IVC VVC = 0V −25 −15 −1 A Switch Characteristics Switching Frequency fOSC 430 500 545 kHz High-Side Switch On-Resistance RON -- 150 -- m High-Side Switch leakage Current IHSD VHSD = 28V, VEN = 0V -- -- 10 A BOOT Leakage Current IBOOT VBOOT = 30V, VEN = 0V (Note 5) -- 1 -- A Maximum Duty VVC = 0V 95 -- -- % SW Leakage Current ILKGL VSW = 28V, VEN = 0V -- -- 10 A Regulator and Logic Characteristics LDO Output Voltage VLDO 50mA Load at V5V, VVC = 0V 4 5 6 V EN Input Voltage Logic-High VENH 2.5 -- -- V Logic-Low VENL -- -- 0.6 EN Input Current IEN 0V ≤ VEN ≤ 5V -- -- 10 A Soft-Start Sourcing Current ISS 1.5 3.3 6 A Thermal Comparator and Protection NTC Threshold, Cold VCOLD NTC Voltage Rising, 1% Hysteresis 73.5% VV5V 75% VV5V 76.5% VV5V V NTC Threshold, Hot VHOT NTC Voltage Rising, 1% Hysteresis 31% VV5V 32.5% VV5V 34% VV5V V NTC Disable Threshold VDISNTC NTC Voltage Rising, 1% Hysteresis 0.2% Vv5v 1.7% Vv5v 3.2% Vv5v V NTC Bias Current INTC -- 2 10 A Thermal Shutdown Temperature TSD (Note 5) -- 160 -- °C Thermal Shutdown Hysteresis TSD (Note 5) -- 30 -- °C
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. 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 for extended periods may remain possibility to affect device reliability. Note 2. JA is measured at T A = 25C on a h igh effective thermal conductivity four -layer test board per JEDEC 51 -7. JC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design, not subjected to production test.
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com Typical Application Circuit VFB 17 (Exposed Pad) RT9535A V5V BOOT HSD SW SNSH SNSL BATT GND VFB VC ISET VIN EN SS VHH VHH7 NTC 5 PGND 11 10μF x 2 100k 100k CIN 1μF VIN 10μF 3.3nF 0.01μF 10k (Optional) (Optional) PMEG4020 D2 D3 100k RNTC 1μF 0.1μF PMEG2030 402 RS3 402 RS2 0.1 RS1 0.1μF To RS3 VHH CBATT 22μF 390k RF2 100k RF1 VBATT To VFB (Optional) 10μH TVS C11 0.1μF C10 0.1μF Note : (1). For application with removable battery, a TVS with appropriate rating is required as shown above. (2). VIN = 15V to 28V, 3 – cell, ICHARGE = 1A
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Typical Operating Characteristics 100 0 5 10 15 20 25 30 Efficiency (%) Supply Voltage (V) Efficiency vs. Supply Voltage
1 Cell : VBATT = 4V
2 Cell : VBATT = 8V
3 Cell : VBATT = 12V
4 Cell : VBATT = 16V
5 Cell : VBATT = 20V IBATT = 1A
0.5 1 1.5 2 2.5 Efficiency (%) Charge Current (A) Efficiency vs. Charge Current
1 Cell : VIN = 12V, VBATT = 4V
2 Cell : VIN = 24V, VBATT = 8V
3 Cell : VIN = 24V, VBATT = 12V
4 Cell : VIN = 24V, VBATT = 16V
5 Cell : VIN = 24V, VBATT = 20V
0.80 0.84 0.88 0.92 0.96 1.00 1.04 1.08 1.12 1.16 1.20 0 10 20 30 Charge Current (A) Supply Voltage (V) Charge Current vs. Supply Voltage 0.0 0.2 0.4 0.6 0.8 1.0 1.2 -50 -25 0 25 50 75 100 125 Supply Current (mA) Temperature (℃) Supply Current vs. Temperature VIN = 28V VIN = 12V -50 -25 0 25 50 75 100 125 Shutdown Current (A) Temperature (℃) Shutdown Current vs. Temperature VIN = 28V VIN = 12V 4.70 4.75 4.80 4.85 4.90 4.95 5.00 -50 -25 0 25 50 75 100 125 V5V Voltage (V) Temperature (℃) V5V Voltage vs. Temperature VIN = 12V, IV5V = 40mA
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com 100 102 104 106 108 110 -50 -25 0 25 50 75 100 125 VICHG (mV) Temperature (°C) VICHG vs. Temperature VIN = 4.5V VIN = 12V VIN = 28V 2.45 2.47 2.49 2.51 2.53 2.55 -50 -25 0 25 50 75 100 125 VFB Voltage (V) Temperature (°C) VFB Voltage vs. Temperature VIN = 4.5V VIN = 12V VIN = 28V 480 485 490 495 500 505 510 0 5 10 15 20 25 30 Switching Frequency (kHz) Supply Voltage (V) Switching Frequency vs. Supply Voltage -50 -25 0 25 50 75 100 125 BATT Bias Current (A) Temperature (℃) BATT Bias Current vs.Temperature Charge Enable and Disable Time (25ms/Div) VBATT (2V/Div) SW-GND (10V/Div) EN (2V/Div) IBATT (500mA/Div) VIN = 12V, VBATT = 4V, IBATT = 1A Adapter Insert and Remove Time (25ms/Div) VBATT (2V/Div) SW-GND (10V/Div) VIN (5V/Div) IBATT (500mA/Div) VIN = 12V, VBATT = 4V, IBATT = 1A
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Charge Enable Time (10ms/Div) VBATT (2V/Div) SW-GND (10V/Div) EN (2V/Div) IBATT (500mA/Div) VIN = 12V, VBATT = 4V, IBATT = 1A Charge Disable Time (10ms/Div) VBATT (2V/Div) SW-GND (10V/Div) EN (2V/Div) IBATT (500mA/Div) VIN = 12V, VBATT = 4V, IBATT = 1A Switching Time (1s/Div) VBATT (5V/Div) IL (500mA/Div) SW-GND (10V/Div) IBATT (1A/Div) VIN = 12V, VBATT = 4V, IBATT = 1A BATT to GND Short Response Time (10ms/Div) VBATT (5V/Div) IL (500mA/Div) SW-GND (10V/Div) IIN (1A/Div) VIN = 12V, VBATT = 4V, IBATT = 1A
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com
Application Information
Input and Output Capacitors In the typical application circuit, the input capacitor (C2) is assumed to absorb all input switching ripple current in the converter, so it must have adequate ripple current rating. Typically, at high charging currents, the converter will operate in continuous conduction mode. In this case, the RMS current I RMSIN of the input capacitor C2 can be estimated by the equation : 2RMSIN BATTI = I D-D Where IBATT is the battery charge current and D is the duty cycle. In worst case, the RMS ripple current will be equal to one half of output charging current at 50% duty cycle. For example, I BATT = 2A, the maximum RMS current will be 1A. A low -ESR ceramic capacitor s uch as X7R or X5R is preferred for the input -decoupling capacitor and should be placed to the drain of the high-side MOSFET and source of the low -side MOSFET as close as possible. The voltage rating of the capacitor must be higher than the norma l input voltage level. Above 20F capacitance is suggested for typical of 2A charging current. The output capacitor (C BATT) is also assumed to absorb output switching current ripple. The general formula for capacitor current is : BATTBATT VINRMSCB osc VV 1- VI= 2 3 L1 f For exampl e, V VIN = 19V, V BATT = 8.4V, L1 = 10 H, and fOSC = 500kHz, IRMS = 0.15A. EMI considerations usually make it desirable to minimize ripple current in the battery leads. Beads or inductors may be added to increase battery impedance at the 500kHz switching frequency. Switching ripple current splits between the battery and the output capacitor depending on the ESR of the output capacitor and the battery impedance. If the ESR of COUT is 0.2 and the battery impedance is raised to 4 with a bead or inductor, only 5% of the ripple current will flow in the battery. Inductor The inductor value will be changed for more or less current ripple. The higher the inductance, the lower the current ripple will be. As the physical size is kept the same, typically, higher inductance will result in higher series resistance and lower saturation current. A good tradeoff is to choose the inductor so that the current ripple is approximately 30% to 50% of the full -scale charge current. The inductor value is calculated as : BATT VIN BATT VIN OSC L V V -VL1 = V f I Δ Where IL is the inductor current ripple. For example, VVIN = 19V, choose the inductor current ripple to be 40% of the full -scale charge current in the typical application circuit for 2A, 2 -cell battery charger, IL = 0.8A, V BATT = 8.4V, calculate L1 to be 12 H. So choose L1 to be 10H which is close to 12H. Soft-Start and Under-Voltage Lockout The soft-start is controlled by the voltage rise time at SS pin. There are internal soft -start and external soft-start in the RT9535A . With a 0.01F capacitor, time to reach full charge current is about 20ms and it is assumed that input voltage to the charger will reach full value in less than 20ms. The capacitor can be increased if longer input start-up times are needed. For the RT9535 A, it provides Under -Voltage Lockout (UVLO) protection. If 5V5LDO output voltage is lower than 3.5V, high-side internal power MOSFET. This will protect the adapter from entering a quasi “latch” state where the adapter output stays in a current limited state at reduced output voltage.
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Full-Scale Charge Current Programming The basic formula for full -scale charge current is (see Block Diagram) : REFBATT V RS2I= R4 RS1 Where R4 is the total resistance from ISET pin to ground. For the sense amplifier CA biasing purpose, RS3 should have the same value as RS2 with 1% accuracy. For example, 2A full-scale charging current is needed. For low power dissipation on RS1 and enough signal to drive the amplifier CA, let RS1 = 100mV/2A = 50m. This limits RS1 power to 0.2W. Let R4 = 10k, then : BATT REF I R4 RS1 2A 10k 0.05RS2 = RS3 = = = 400V 2.5V Ω Note that for charge current accuracy and noise immunity, 100mV full scale level across the sense resistor RS1 is required. Consequently , both RS2 and RS3 should be 402. The R4 should be set to between 5k and 15k for the best operation. It is critical to have a good Kelvin connection on the current sense resistor RS1 to minimize stray resistive and inductive pickup. RS1 should have low parasitic inductance (typical 3nH or less). The layout pat h from RS2 and RS3 to RS1 should be kept away from the fast switching SW node. A 1nF ceramic capacitor can be used across SNSH and SNSL and be kept away from the fast switching SW node. Battery Voltage Regulation The RT953 5A uses high -accuracy voltage band gap and regulator for the high charging -voltage accuracy. The charge voltage is programmed via a resistor divider from the battery to ground, with the midpoint tied to the VFB pin. The voltage at the VFB pin is regulated to 2.5V, giving the following equation for the regulation voltage: BATT RF2V = 2.5 1+ RF1 where RF2 is connected from VFB to the battery and RF1 is connected from VFB to GND. Charging The 2A Battery Charger (typical application circuit) charges lithium -ion batteries at a constant 2A until battery voltage reaches the setting value. The charger will then automatically go into a constant voltage mode with current decreasing to near zero over time as the battery reaches full charge. Dropout Operation The RT9535A can charge the battery eve n when VIN goes as low as 2V above the combined voltages of the battery and the drops on the sense resistor as well as parasitic wiring. This low VIN sometimes forces 100% duty cycle and high-side power switch stays on for many switching cycles. While high-side power switch stays on, the voltage V BOOT across the capacitor C8 drops down slowly because the current sink at BOOT pin. C8 needs to be recharged before VBOOT drops too low to keep the topside switch on. A unique design allows the RT9535A to oper ate under these conditions. If SW pin voltage keeps larger than 1.3V for 32 oscillation periods, high-side power MOSFET will be turned off and an internal MOSFET will be turned on to pull SW pin down. This function refreshes V BOOT voltage to a higher value . It is important to use 0.1F to hold VBOOT up for a sufficient amount of time. Shutdown When adapter power is removed, VIN will drift down. As soon as VIN goes down to 0.1V above V BATT, the RT9535A will go into sleep mode drawing only ~10 A from the battery. There are two suggest ways to stop switching: pulling the EN pin low or pulling the VC pin low. Pulling the EN pin low will shut down the whole
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS9535A-04 February 2016 www.richtek.com chip. Pulling the VC pin low will only stop switching and 5V5LDO stays active. Make sure there is a pull-up resistor on the EN pin even if the EN pin is not used, otherwise internal pull -down current will keep the EN pin low to shut down mode when power turns on. Charger Protection Note that the RT9535A will operate even when VBATT is grounded. If VBATT of typical application circuit charger gets shorted to ground very quickly from a high battery voltage, slow loop response may allow charge current to build up and damage the high-side internal N-MOSFET . A small diode from the EN pin to VBATT will shut down switching and protect the charger. Temperature Qualification The controller RT9535A continuously monitors battery temperature by measuring the voltage between the NTC pin and GND. A negative temperature coefficient thermistor (NTC) and an external voltag e divider typically generate this voltage. The controller compares this voltage against its internal thresholds to determine if charging is allowed. To initiate a charge cycle, the battery temperature must be within the VCOLD. If battery temperature is out side of this range, the controller suspends charge and the safety timer and waits until the battery temperature is within the VCOLD to VHOT range. During the charge cycle, the battery temperature must be within the VCOLD and VDISNTC thresholds. If the batt ery temperature is outside of this range, the controller suspends charge and waits until the battery temperature is within the VCOLD to VHOT range. The controller suspends charge by turning off the PWM charge MOSFETs. Assuming a 103AT NTC thermistor on the battery pack as shown in the below, the values of RT1 and RT2 can be determined by using the following equations : V5V COLD HOT COLD HOT V5V V5VHOT HOT HOT COLD 11V RTH RTH - VVRT2 = VVRTH -1 -RTH -1VV V5V COLD COLD V -1VRT1 = 11 +RT2 RTH RT9535A V5V NTC RT1 RT2 RTH 103AT TS Resistor Network Where RTHCOLD and RTHHOT which have defined in the spec of the 103AT NTC thermistor. Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperatu re. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) TA) / JA
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. temperature on the maximum power dissipation. Figure 1. Derating Curve of Maximum Power
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. the SS/VC/ISET pin as close as possible. close to the SW pin as possible. the NTC/VFB pin as close as possible. Figure 2. PCB Layout Guide
Copyright © 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS9535A-04 February 2016 Outline Dimension Symbol Dimensions In Millimeters Dimensions In Inches 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 0.250 0.380 0.010 0.015 D 3.950 4.050 0.156 0.159 D2 2.000 2.450 0.079 0.096 E 3.950 4.050 0.156 0.159 E2 2.000 2.450 0.079 0.096 e 0.650 0.026 L 0.500 0.600 0.020 0.024 W-Type 16L QFN 4x4 Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st 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 curre nt and complete. Ric htek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsid iaries for its use; nor for any infringements 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 Richtek or its su bsidiaries.