RT9534 High Efficiency Switching Mode Battery Charger General Description Features The RT9534 is a PWM switch mode battery charger Fast Charging for Li-Ion, NiMH and NiCd Batteries controller to fast charge single or multiple Li-Ion, NiMH Adjustable Battery Voltages from 2.5V to 22V and NiCd batteries, using constant current or constant High Efficiency : Up to 95% voltage control. Maximum current can be easily Charging Current Programmed by Resistor programmed by external resistor. The constant voltage Precision 0.5% Charging Voltage Accuracy output can support up to 22V with 0.5% accuracy. Provide 5% Charging Current Accuracy A third control loop limits the input current drawing from Input Current Limit Maximizes Charging Rate the adapter during charging. This allows simultaneous Synchronous Converter with 400kHz Switching operation of the equipment and fast battery charging Frequency without over loading to the adapter. Flag Indicates Li-Ion Charge Completion The RT9534 can charge batteries from 2.5V to 22V Auto Shutdown with Adapter Removal with dropout voltage as low as 0.4V. A diode is not required in series with the battery because the charger automatically enters a 10μA sleep mode when the Applications Notebook Computers Portable Instruments Chargers for Li-lon, NiMH, NiCd and Lead Acid adapter is unplugged. A logic output indicates Li-Ion full charge when current drops to 20% of the full-scale Rechargeable Batteries programmed charge current. The RT9534 is available in WQFN-24L 4x4 Package. Simplified Application Circuit M1 SI4435 VIN RS4 CIN R2 C2 D2 MMSD4148T1G C1 R1 V5V ACN To VHH Pin C7 EN M2 SI4412 R6 RT9534 R5 M3 SI4412 BG MODE S2 FBR C3 C4 RS3 RS2 BATT RF2 CBATT SGND C5 RS1 RF2 RF1+200 PGND VC R4 L1 SW ISET R3 VBATT = 2.5 1+ C8 TG ACDRV VIN BOOT ACP S1 D3 MMSD4148T1G SGND V5V RF1 NTC VFB R9 STATUS C6 August 2015 Css C9 R 10 SNS RNTC C11 Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 SNSH SNSL VHH 200 BATT SS is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9534 Ordering Information Pin Configurations RT9534 (TOP VIEW) 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. 24 23 22 21 20 19 EN NTC VC ISET FBR VFB 1 18 2 17 3 SGND 4 25 5 6 16 15 14 13 7 8 BOOT TG SW PGND BG VIN 9 10 11 12 BATT SNSL SNSH SNS VHH V5V Lead Plating System G : Green (Halogen Free and Pb Free) ACDRV ACP ACN SS STATUS MODE Package Type QW : WQFN-24L 4x4 (W-Type) (Exposed Pad-Option 1) Marking Information 1B= : Product Code 1B=YM DNN YMDNN : Date Code Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 WQFN-24L 4x4 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 Functional Pin Description Pin No. Pin Name Pin Function 1 EN 2 NTC 3 VC 4 ISET 5 FBR 6 VFB 7 BATT 8 SNSL Enable Control Input (Active High). It must be connected to a logical voltage or pulled up to VIN with a 100k resistor. Input for an external NTC thermistor for battery temperature monitoring. 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. Charge Current Setting and System Loop Compensation Pin. Connect a resistor from this pin to ground to set the charge current. Negative Terminal of External Resistor Divider for Battery Voltage Feedback. A 200 resistor connect from FBR to GND. Battery Voltage Feedback. Using an external resistor divider to set battery full charge voltage. Battery Voltage Sensing Input. A 10F or larger X5R ceramic capacitor is recommended for filtering charge current ripple and stability purpose. Negative Terminal for Sensing Charge Current. 9 SNSH Positive Terminal for Sensing Charge Current. 10 SNS Input terminal for reversal current comparator. 11 VHH 12 V5V 13 VIN 14 BG Output of low side driver. 15 PGND 16 SW Power Ground. Switch Node. This pin switches between ground and VIN with high dv/dt rates. Care needs to be taken in the PCB layout to keep this node from coupling to other sensitive nodes. 17 TG Output of High-Side Driver with BOOT and SW as Floating Power and Return. 18 BOOT Bootstrap Supply for the High-Side Gate Driver and Control Circuitry. In normal operation, VBOOT ≈ VSW + 5V. 19 MODE Input control pin for CCM of DCM mode selection. Tying MODE pin to V5V for CCM mode selection and GND for DCM. 20 STATUS Flag to Indicate Charge Completion. It turns to logical high when the charge current drops blew 20% of the setting charge current. A 0.1F capacitor from STATUS to ground is needed to filter the sampled charge current ripple. 21 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. 22 ACN Negative Terminal to Sense Input Current. A filter is needed to filter out the 500kHz switching noise. 23 ACP Positive Terminal to Sense Input Current. 24 ACDRV Drive Signal for the Gate of Input Power PFET. 25 (Exposed Pad) SGND Signal Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation. 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 3.6V. Output of Internal 5V LDO. Connect a 1F ceramic capacitor from this pin to GND for stability. Input Power Supply. Connect a low ESR capacitor of 10F or higher from this pin to ground for good bypass. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9534 Function Block Diagram VIN ACDRV NTC ACN R1 200k 5V 1.4V THERMAL CMP C3 EN DRIVER 0.5uA 5V VREF 2.5V REFERENCE SD VIN UVLO V5V LDO + VIN BATT C2 0.4V UVLO SGND 3.9V IVA ICHG VHH STATUS SLOP COMP ICHG 5 OSCILLATOR R2 SNSH CA SNSL ICHG BOOT PWM S C1 VFB VREF 2.5V FBR VA VREF 2.5V IVA TG R EA SW 200 SD 1.3V 100mV + ACP ICL Soft-Start V5V CL ACN LOGIC BG SNS BATT PGND REV ISET Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 SS VC MODE is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 Operation The RT9534 is a current mode PWM step-down CL Amplifier switching charger controller. The battery DC charge The amplifier CL monitors and limits the input current, current is programmed by a resistor R4 at the ISET pin normally from the AC adapter, to a preset level (100mV and the ratio of sense resistor RS2 over RS1 in the / RS4). At input current limit, CL will supply the typical application circuit. Amplifier CA converts the programming current at ISET pin, thus reducing battery charge current through RS1 to a much lower sampled charging current. current ICHG (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 Charge STATUS When the charger is in voltage mode and the charge current level is reduced to 20%, STATUS pin will turn to logic high. This charge completion signal can be used to start a timer for charge termination. A 0.1F 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 capacitor from STATUS to ground is needed to filter the sampled charging current ripple. current mode inner loop. An internal LDO generates a ACDRV Driver 5V to power topside FET gate driver. For batteries like The ACDRV pin drives an external P-MOSFET to avoid lithium that require both constant current and constant reverse current from battery to input supply. When voltage charging, the 0.5% 2.5V reference and the input supply is removed, the RT9534 goes into a low voltage amplifier VA reduce the charge current when current, 10A maximum, sleep mode as VIN drops battery voltage reaches the normal charge voltage level. below the battery voltage. For NiMH and NiCd, VA can be used for over voltage protection. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9534 Absolute Maximum Ratings (Note 1) VIN, SW, EN, ACN, VHH to GND --------------------------------------------------------- 0.3V to 30V ACDRV ------------------------------------------------------------------------------------------- (ACN 6V) to (ACN 0.3V) ACP ------------------------------------------------------------------------------------------------ (ACN 0.3V) to (ACN 0.6V) BATT to GND------------------------------------------------------------------------------------ 0.3V to 28V ISET, VC, VFB, V5V, BG to GND ---------------------------------------------------------- 0.3V to 6V SNSL ---------------------------------------------------------------------------------------------- (BATT 0.3V) to (BATT 0.3V) SNSH---------------------------------------------------------------------------------------------- (SNSL 0.3V) to (SNSL 0.3V) BOOT --------------------------------------------------------------------------------------------- (SW 0.3V) to (SW 6V) TG -------------------------------------------------------------------------------------------------- (SW 0.3V) to (BOOT + 0.3V) Power Dissipation, PD @ TA = 25C WQFN-24L 4x4 --------------------------------------------------------------------------------- 3.57W Package Thermal Resistance (Note 2) WQFN-24L 4x4, JA --------------------------------------------------------------------------- 28C/W WQFN-24L 4x4, JC --------------------------------------------------------------------------- 7C/W Lead Temperature (Soldering, 10 sec.) --------------------------------------------------- 260C Junction Temperature ------------------------------------------------------------------------- 150C Storage Temperature Range ---------------------------------------------------------------- 65C to 150C ESD Susceptibility (Note 3) HBM (Human Body Model) ------------------------------------------------------------------ 2kV MM (Machine Model) -------------------------------------------------------------------------- 200V Recommended Operating Conditions (Note 4) Supply Input Voltage -------------------------------------------------------------------------- 4.5V to 28V Battery Voltage, VBAT ------------------------------------------------------------------------ 2.5V to 22V Ambient Temperature Range---------------------------------------------------------------- 40C to 85C Junction Temperature Range --------------------------------------------------------------- 40C to 125C 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 0.5 1.3 2 mA Overall Supply Quiescent Current IQ No Charge Current Supply Shutdown Current ISD VEN = 0 -- -- 12 A Reverse Current from Battery IREV VIN Floating -- -- 10 A VIN Under-Voltage Lockout VUVLO 3.6 3.8 4.3 V VIN Under-Voltage Lockout Hysteresis VUVLO_HYS -- 300 -- mV Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 Parameter Symbol Test Conditions Min Typ Max Unit 2.488 2.5 2.512 V -- -- 0.1 A Reference Reference Voltage VFB FB Bias current IFB VFB = 2.5V FBR to GND Resistance RFBR SD = 2V 160 200 220 SD = 0V -- -- 1 A R4 = 10k, RS2 = RS3 = 402, Measure the Voltage Drop Across RS1 95 100 105 mV -- -- −0.5 mA FBR leakage Current Charge Current Full-Scale Charge Current Sense Voltage VICHG ISET Output Current IISET Termination current Set Factor VITM SNSL Bias Current ISNSH 1/5-Scale Charge Current when STATUS from Low to High No Charge Current SNSH Bias Current ISNSH No Charge Current -- 20 27 % −36 −12 −6 A −36 −12 −6 A -- -- 3.6 V -- 0.3 0.4 V Battery Voltage VHH Minimum Voltage with Respect to BATT VIN Minimum Voltage with Respect to BATT VHH Input Current VHH VDROP IVHH VIN = 28V 150 180 210 A BATT Bias Current IBATT VBATT = 25V 0.8 2 8 A VC Pin Current IVC VVC = 0V −25 −15 −1 A SNS Bias Current ISNS −36 −12 −6 A Input Current Limit Input Current Limit Sense Voltage VILMT Measure the Voltage Drop Across RS4 95 100 105 mV ACN Input Current IACN VACP − VACN = 0.1V 5 16 37 A ACP Input Current IACP VACP − VACN = 0.1V 25 50 80 A ACDRV ON Voltage VACON 4 5.4 6 V ACDRV OFF Voltage VACOFF -- -- 0.1 V ARDRV Pull-Down Current IACPD 5 10 40 A ARDRV Pull-Up Current IACPU −10 −5 −2 A 350 400 450 kHz -- 25 75 ns Measure the Voltage (VACN − VACDRV) Measure the Voltage (VACN − VACDRV), VEN = 0V VACN − VACDRV = 3.8V VACN − VACDRV = 0.5V, VEN = 0V Switch Characteristics Switching Frequency fOSC TG Rise Time TR Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 VBOOT − VSW = 5V, 1nF Load at TG Pin is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9534 Parameter Symbol Test Conditions VBOOT − VSW = 5V, 1nF Min Typ Max Unit -- 25 75 ns TG Fall Time TF BG Rise Time BR CBG =1nF -- 25 75 ns BG Fall Time BF CBG =1nF -- 25 75 ns Maximum Duty 95 -- -- % Dead Time -- 20 -- ns Load at TG Pin TG ON Voltage VTG VTG – VSW -- 4.2 -- V BG ON Voltage VTG VBG -- 4.2 -- V BOOT Leakage Current IBOOT VBOOT = 28V, VEN = 0V -- 1 -- A VVC = 0V 95 -- -- % VSW = 28V, VEN = 0V -- -- 10 A 4 5.2 6 V -- 5 -- V Maximum Duty SW Leakage Current ILKGL Regulator and Logic Characteristics LDO Output Voltage VLDO STATUS High Voltage EN Input Voltage 50mA Load at V5V, VVC = 0V STATUS Cap = 1F Logic-High VENH 2.5 -- -- Logic-Low VENL -- -- 0.6 -- -- 10 A 0V ≤ VEN ≤ 5V V EN Input Current IEN Soft-Start Sourcing Current ISS 1.5 3.3 6 A MODE Pin Threshold ON VMODE 0.8 -- 3.5 V Thermal Comparator and Protection NTC Voltage Rising, 1% 73.5% 75% Hysteresis VV5V VV5V NTC Voltage Rising, 1% 31% 32.5% Hysteresis VV5V VV5V --- NTC Threshold, Cold VCOLD NTC Threshold, Hot VHOT NTC Bias Current INTC Thermal Shutdown Temperature TSD -- Thermal Shutdown Hysteresis TSD -- 76.5% VV5V 34% VV5V 0.1 A 160 -- °C 30 -- °C V 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. JA is measured at TA = 25C on a high 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. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 Typical Application Circuit M1 SI4435 VIN RS4 50 mohm R2 56 CIN 10μF C1 33nF R1 100k C2 10μFx2 22 23 24 S1 R3 (Optional) 1 C3 (Optional) R5 1k C5 (Optional) EN VIN 6 TG ACDRV ISET 25 BOOT ACP 4 5 C4 1μF ACN 13 3 R4 10k V5V SW BG PGND VC MODE FBR NTC VFB STATUS 11 C6 0.1μF 8 17 M2 SI4412 R6 10 C8 0.1μF L1 6.8μH VBATT = 2.5 1+ RS1 50 mohm RF2 RF1+200 BATT 9 14 M3 SI4412 RS3 402 15 RS2 402 TVS 1430k 19 S2 SGND V5V CBATT 10μF R7 250k 2 R9 500k 20 21 Css 0.1μF C9 0.1μF R10 500k SNS SNSH BATT 7 SNSL VHH SS 200 To VHH Pin C7 1μF 18 16 D3 MMSD4148T1G R8 RT9534 SGND D2 MMSD4148T1G 12 10 C11 0.1μF Note : (1). For application with removable battery, a TVS with appropriate rating is required as shown above. (2). VIN = 18V to 28V, 4 cell, ICHARGE = 2A Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9534 Typical Operating Characteristics Efficiency vs. Charge Current 100 95 95 90 90 Efficiency (%) Efficiency (%) Efficiency vs. Supply Voltage 100 85 1 Cell : VBATT 2 Cell : VBATT 3 Cell : VBATT 4 Cell : VBATT 5 Cell : VBATT 80 75 = 4V = 8V = 12V = 16V = 20V 85 1 Cell : VIN = 10V, VBATT 2 Cell : VIN = 12V, VBATT 3 Cell : VIN = 16V, VBATT 4 Cell : VIN = 20V, VBATT 5 Cell : VIN = 28V, VBATT 80 75 IBATT = 2A 70 70 0 5 10 15 20 25 1 30 2 4 5 Quiescent Current vs. Temperature Charge Current vs. Supply Voltage 0.9 2.20 2.12 2.08 2.04 = 4V = 8V = 12V = 16V = 20V 0.8 Quiescent Current(mA) 1 Cell : VBATT 2 Cell : VBATT 3 Cell : VBATT 4 Cell : VBATT 5 Cell : VBATT 2.16 Charge Current (A) 3 Charge Current (A) Supply Voltage (V) 2.00 1.96 1.92 1.88 0.7 0.6 0.5 0.4 0.3 0.2 VIN = 28V VIN = 12V 0.1 1.84 0 1.80 0 5 10 15 20 25 -50 30 -25 25 50 75 100 125 V5V Voltage vs. Temperature Shutdown Current vs. Temperature 5.00 25 4.95 V5V Voltage (V) 30 20 15 VIN = 28V VIN = 12V 10 0 Temperature(℃) Supply Voltage (V) Shutdown Current(μA) = 4V = 8V = 12V = 16V = 22V 4.90 4.85 4.80 5 4.75 0 4.70 VIN = 12V, IV5V = 40mA -50 -25 0 25 50 75 100 Temperature (℃) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 125 -50 -25 0 25 50 75 100 125 Temperature (℃) is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 VICHG vs. Temperature Feedback Voltage vs. Temperature 110 2.6 108 106 Feedback Voltage (V) 2.55 VICHG (mV) 104 102 100 98 96 VIN = 4.5V VIN = 12V VIN = 28V 94 92 -25 0 25 50 75 100 2.45 2.4 2.3 125 -50 Temperature (°C) 25 50 75 100 125 BATT Bias Current vs.Temperature 12 395 BATT Bias Current (A) Switching Frequency (kHz) 0 14 400 390 385 380 375 10 8 6 4 2 370 0 3 6 9 12 15 18 21 24 27 30 -50 -25 0 25 50 75 Input Voltage (V) Temperature (℃) Charge Enable Charge Enable 100 125 EN (2V/Div) VBATT (5V/Div) VBATT (5V/Div) SW-GND (10V/Div) SW-GND (10V/Div) VIN = 16V, VBATT = 12V, IBATT = 2A Time (2.5ms/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 -25 Temperature (°C) Switching Frequency vs. Input Voltage EN (2V/Div) IBATT (1A/Div) VIN = 4.5V VIN = 12V VIN = 28V 2.35 90 -50 2.5 August 2015 IBATT (1A/Div) VIN = 16V VBATT = 12V IBATT = 2A Time (2.5ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT9534 Adapter Insert Adapter Remove SW-GND (10V/Div) SW-GND (10V/Div) VBATT (2V/Div) VIN (5V/Div) IBATT (1A/Div) VBATT (2V/Div) VIN (5V/Div) VIN = 16V, VBATT = 12V, IBATT = 2A IBATT (1A/Div) Time (25ms/Div) Time (25ms/Div) CCM Switching DCM Switching TG (20V/Div) VBATT (5V/Div) TG (20V/Div) VBATT (5V/Div) BG (5V/Div) BG (5V/Div) IL (500mA/Div) IL (500mA/Div) VIN = 16V, VBATT = 12V, IBATT = 100mA Time (1s/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 VIN = 16V, VBATT = 12V IBATT = 2A VIN = 16V, VBATT = 12V, IBATT = 100mA Time (1s/Div) is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 Application Information Input and Output Capacitors and the battery impedance is raised to 4 with a bead In the typical application circuit, the input capacitor (C2) or inductor, only 5% of the ripple current will flow in the is assumed to absorb all input switching ripple current battery. 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 IRMSIN of the input capacitor C2 can be estimated by the equation: IRMSIN = IBATT D D2 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 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, IBATT = 2A, the maximum RMS current will be 1A. A low-ESR ceramic capacitor such 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 normal input voltage level. Above 20F capacitance is suggested for ripple is approximately 30% to 50% of the full-scale charge current. The inductor value is calculated as : L1 = VBATT VVIN VBATT VVIN fOSC ΔIL 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, VBATT = 8.4V, calculate L1 to be 12H. So choose L1 to be 10H which is close to 12H. typical of 2A charging current. Soft-Start and Under-Voltage Lockout The output capacitor (CBATT) is also assumed to The soft-start is controlled by the voltage rise time at absorb output switching current ripple. The general VC pin. There are internal soft-start and external formula for capacitor current is : soft-start in the RT9534. With a 1F capacitor, time to IRMSCB VBATT VBATT 1 VVIN = 2 3 L1 fosc reach full charge current is about 60ms and it is assumed that input voltage to the charger will reach full value in less than 60ms. The capacitor can be For example, VVIN = 19V, VBATT = 8.4V, L1 = 10H, increased if longer input start-up times are needed. and f OSC = 400kHz, IRMS = 0.15A. For the RT9534, it provides Under-Voltage Lockout EMI considerations usually make it desirable to (UVLO) protection. If LDO output voltage is lower than minimize ripple current in the battery leads. Beads or 3.9V, the internal top side power FET and input power inductors may be added to increase battery impedance FET M1 will be cut off. This will protect the adapter from at the 400kHz switching frequency. Switching ripple entering a quasi “latch” state where the adapter output current splits between the battery and the output stays in a current limited state at reduced output capacitor depending on the ESR of the output capacitor voltage. and the battery impedance. If the ESR of COUT is 0.2 Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT9534 Adapter Current Limiting 5.5k to 60k range. An important feature of RT9534 is the ability to For for 40C to 85C application temperature range, automatically adjust charge current to a level which the value for R4 must be within 6k to 30k range. avoids overloading the wall adapter. This allows the product to operate, and at the same time batteries are being charged without complex load management algorithms. Additionally, batteries will automatically be charged at the maximum possible rate of which the adapter is capable. This is accomplished by sensing total adapter output current and adjusting charge current downward if a preset adapter current limit is 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 path 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. exceeded. Amplifier CL in typical application circuit senses the voltage across RS4, connected between Battery Voltage Regulation the ACP and ACN pins. When this voltage exceeds The RT9534 uses high-accuracy voltage bandgap and 100mV, the amplifier will override programmed charge regulator for the high charging-voltage accuracy. The current to limit adapter current to 100mV/RS4. A low charge voltage is programmed via a resistor divider pass filter formed by 56 and 33nF is required to from the battery to ground, with the midpoint tied to the eliminate switching noise. VFB pin. The voltage at the VFB pin is regulated to 2.5V, giving the following equation for the regulation Full-Scale Charge Current Programming The basic formula for full-scale charge current is (see Block Diagram) : voltage : RF2 VBATT = 2.5 1 + RF1+200 VREF RS2 IBATT = R4 RS1 where RF2 is connected from VFB to the battery and Where R4 is the total resistance from ISET pin to RF1 is connected from VFB to GND. 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 : IBATT R4 RS1 2A 10k 0.05 RS2 = RS3 = = = 400Ω VREF 2.5V 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. Charging Completion Note that for charge current accuracy and noise Some battery manufacturers recommend termination of immunity, 100mV full scale level across the sense constant voltage float mode after charge current has resistor RS1 is required. Consequently, both RS2 and dropped below a specified level (typically around 20% RS3 should be 399. For for 0C to 85C application of the full-scale charge current) and a further time-out temperature range, the value for R4 must be within period of 30 minutes to 90 minutes has elapsed. Check Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 RT9534 with manufacturers for details. The RT9534 provides a VACN. In sleep mode, when VIN is removed, ACDRV signal at the STATUS pin when charging is in voltage will clamp M1 VSG to less than 0.1V. mode and charge current is reduced to 20% of full-scale charge current, assuming full-scale charge current is programmed to have 100mV across the current sense resistor (VRS1). The charge current sample ICHG is compared with the output current IVA of voltage amplifier VA. When the charge current drops to 20% of full-scale charge current, IVA will be equal to 20% of ICHG and the STATUS pin voltage will go logic high and can be used to start an external timer. When this feature is used, a capacitor of at least 0.1F is required at the STATUS pin to filter out the switching noise. If this feature is not used, the capacitor is not needed. Dropout Operation The RT9534 can charge the battery even 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 TG stays on for many switching cycles. While TG stays on, the voltage VBOOT 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 RT9534 to operate under these conditions. If SW pin voltage keeps larger than 1.3V for 32 oscillation periods, topside power FET will be turned off and an internal FET will be turned on to Shutdown When adapter power is removed, VIN will drift down. As soon as VIN goes down to 0.1V above VBATT, the RT9534 will go into sleep mode drawing only ~10μA from the battery. There are two 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 chip. Pulling the VC pin low will only stop switching and LDO stays work. 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 If the VIN connector of typical application circuit can be instantaneously shorted to ground, the P-MOSFET M1 must be quickly turned off, otherwise, high reverse surge current might damage M1. An internal transient enhancement circuit is designed to quickly charge ACDRV pin voltage to ACN pin voltage. Note that the RT9534 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 topside N-MOSFET M2. A small diode from the EN pin to VBATT will shut down switching and protect the charger. pull SW pin down. This function refreshes VBOOT Temperature Qualification voltage to a higher value. It is important to use 0.1F to The controller RT9534 continuously monitors battery hold VBOOT up for a sufficient amount of time. The temperature by measuring the voltage between the P-MOSFET M1 is optional and can be replaced with a NTC pin and GND. A negative temperature coefficient diode if VIN is at least 2.5V higher than VBATT. The thermistor (NTC) and an external voltage divider gate control pin ACDRV turns on M1 when V5V gets up typically develop this voltage. The controller compares above the under-voltage lockout level and is clamped this voltage against its internal thresholds to determine internally to 5V below VACN. In sleep mode, when VIN if charging is allowed. To initiate a charge cycle, the is removed, ACDRV will clamped internally to 5V below battery temperature must be within the VCOLD. If Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 RT9534 battery temperature is outside of this range, the ambient thermal resistance. controller suspends charge and the safety timer and For recommended operating condition specifications, waits until the battery temperature is within the VCOLD the maximum junction temperature is 125C. The to VHOT range. If the battery temperature is outside of junction to ambient thermal resistance, JA, is layout this range, the controller suspends charge and waits dependent. For WQFN-24L 4x4 package, the thermal until the battery temperature is within the VCOLD to resistance, JA, is 28C/W on a standard JEDEC 51-7 VHOT range. The controller suspends charge by four-layer thermal test board. The maximum power turning off the PWM charge FETs. dissipation at TA = 25C can be calculated by the Assuming a 103AT NTC thermistor on the battery pack following formula : as shown in the below, the values of RT1 and RT2 can PD(MAX) = (125C 25C) / (28C/W) = 3.57W for be determined by using the following equations: WQFN-24L 4x4 package 1 1 VV5V RTHCOLD RTHHOT V V HOT COLD RT2 = VV5V VV5V RTHHOT 1 RTHCOLD 1 V V HOT COLD The maximum power dissipation depends on the VV5V 1 VCOLD RT1 = 1 1 RT2 RTHCOLD temperature on the maximum power dissipation. operating ambient temperature for fixed TJ(MAX) and thermal resistance, JA. The derating curve in Figure 1 allows the designer to see the effect of rising ambient V5V RT9534 RT1 NTC 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 temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) TA) / JA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and JA is the junction to Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 16 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015 Maximum Power Dissipation (W)1 RT9534 5.0 Four-Layer PCB 4.0 3.0 2.0 1.0 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve of Maximum Power Dissipation Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9534-00 August 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 17 RT9534 Outline Dimension Symbol D2 E2 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 0.180 0.300 0.007 0.012 D 3.950 4.050 0.156 0.159 Option 1 2.400 2.500 0.094 0.098 Option 2 2.650 2.750 0.104 0.108 E 3.950 4.050 0.156 0.159 Option 1 2.400 2.500 0.094 0.098 Option 2 2.650 2.750 0.104 0.108 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 24L 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 current and complete. Richtek 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 subsidiaries 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 subsidiaries. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 18 is a registered trademark of Richtek Technology Corporation. DS9534-00 August 2015