RT9526A Linear Single Cell Li-Ion Battery Charger with Input Over Voltage Protection General Description Features The RT9526A is a fully integrated low cost single cell Liion battery charger ideal for portable applications. The RT9526A is capable of being powered up from AC adapter and USB (Universal Serial Bus) port inputs. The RT9526A enters sleep mode when supplies are removed. The RT9526A optimizes the charging task by using a control algorithm including preconditioning mode, fast charge mode, and constant voltage mode. The charging task will remain in constant voltage mode to hold the battery in a full charge condition. The charge current can be programmed with an external resistor. The internal thermal feedback circuitry regulates the die temperature to optimize the charge rate under all ambient temperatures. The RT9526A features 28V maximum rating voltage for VIN. The other features are under voltage protection and over voltage protection for the AC adapter supply. z The RT9526A is available in WDFN-8L 2x3 package to achieve best solution for PCB space and total BOM cost saving considerations. z z z z z z z z z 28V Maximum Rating for AC Adapter Internal Integrated Power FETs AC Adapter Power Good Status Indicator Programmed Charging Current Charge Status Indicator Programmed End of Charge Current Under Voltage Protection Over Voltage Protection Thermal Feedback Optimizing Charge Rate RoHS Compliant and Halogen Free Applications z z z z Cellular Phones Digital Cameras PDAs and Smart Phones Portable Instruments Pin Configurations Ordering Information VIN PGB CHG_SB ENB RT9526A Package Type QW : WDFN-8L 2x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) ` 9 8 7 6 5 BATT ISET IMIN GND WDFN-8L 2x3 Marking Information Note : Richtek products are : 1 2 3 4 GND (TOP VIEW) 05 : Product Code 05W W : Date Code RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. DS9526A-01 April 2011 www.richtek.com 1 RT9526A Typical Application Circuit Adapter or USB VIN CIN RISET RIMIN BATT COUT RT9526A ISET R1 PGB IMIN GND VBATT R2 CHG_SB VBATT ENB Function Pin Description Pin No. Pin Name 1 VIN 2 PGB 3 CHG_SB 4 ENB 5, GND 9 (Exposed Pad) 6 IMIN 7 ISET 8 BATT Pin Function Supply Voltage Input. VIN can withstand up to 28V input. Power Good Indicator. This pin connects to VIN with 10SL N-MOSFET as power good condition. Charge Status Indicator Output (Open drain). Indicate low when battery is charging; indicate high when battery charging finished or any fault happened. Charge Enable (Active Low). Connect this pin with 200kΩ pull low resistor. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. EOC Current Setting Pin. Charge Current Set Point. Battery Charge Current Output. Function Block Diagram Switch Well BATT VIN BASE VREF IBIAS Sleep Mode ISET Current Set Block CC/CV/TR Multi Loop Controller EOC Set Block IMIN CHG_SB OVP UVLO PGB Logic ENB 200k www.richtek.com 2 GND DS9526A-01 April 2011 RT9526A Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Voltage, VIN -----------------------------------------------------------------------------------------------------CHG_SB, PGB Pins -----------------------------------------------------------------------------------------------------Others -----------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-8L 2x3 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-8L 2x3, θJA --------------------------------------------------------------------------------------------------------WDFN-8L 2x3, θJC --------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------- Recommended Operating Conditions z z −0.3V to 28V −0.3V to 7V −0.3V to 6V 0.833W 120°C/W 8.2°C/W 260°C 150°C −65°C to 150°C (Note 3) Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 4.5V, TA = 25°C unless otherwise specified) Parameter Min Typ Max Unit VPOR_H 3.4 3.8 4.2 V VPOR_L 3.1 3.5 3.9 V VIN − VBATT VOS Rising VOS_H -- 90 150 mV VIN − VBATT VOS Falling VOS_L 10 50 -- mV --4.158 -- 400 1 4.2 0.6 600 5 4.242 -- μA μA V Ω -- 1.22 -- V 450 500 550 mA VIN POR Rising Threshold Voltage VIN POR Falling Threshold Voltage VIN Standby Current BATT Sleep Leakage Current Battery Regulation Voltage VIN Power FET On-Resistance ISET Set Voltage (Fast Charge Phase) Charge Current Accuracy Symbol Test Conditions VBATT = 4.5V ISLEEP VREG RDS(ON) IBATT = 0.5A VISET RISET = 24.3kΩ BATT Pre-Charge Threshold VCHG_PRE 2.45 2.55 2.65 V BATT Pre-Charge Threshold Hysteresis ΔVCHG_PRE 40 100 150 mV Pre-Charge Current ICHG_PRE 12 16.7 21.3 % 1.5 --- --115 -0.4 -- V V °C 6.7 7 7.5 V -- 0.1 -- V ENB Input Threshold Voltage Logic-High VIH Logic-Low VIL Thermal Regulation TREG VIN Over Voltage Protection VOVP Threshold VIN OVP Hysteresis ΔVOVP VIN = 4.2V to 24V PGB Pull Down Voltage 5mA -- 200 -- mV CHG_SB Pull Down Voltage 5mA -- 200 -- mV To be continued DS9526A-01 April 2011 www.richtek.com 3 RT9526A Parameter EOC Current Setting EOC Rising Threshold Symbol IIMIN Test Conditions Min Typ Max Unit RIMIN = 243kΩ -- 45 -- mA RIREF = 24.3kΩ 337.5 375 412.5 mA 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. θJA is measured in natural convection at TA = 25°C on a low-effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. The measurement case position of θJC is on the exposed pad of the packages. Note 3. The device is not guaranteed to function outside its operating conditions. www.richtek.com 4 DS9526A-01 April 2011 RT9526A Typical Operating Characteristics VOUT Regulation Voltage vs. Input Voltage BATT Sleep Leakage Current vs. Battery Voltage BATT Sleep Leakage Current (µA)1 VOUT Regulation Voltage (V)1 4.2420 4.2252 4.2084 4.1916 4.1748 4.1580 4.5 5 5.5 6 6.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 7 1 1.5 Input Voltage (V) 2 2.5 3 3.5 4 4.5 Battery Voltage (V) Pre-Charge Current vs. Input Voltage Charge Current vs. Input Voltage 550 95 Pre-Charge Current (mA) 540 Charge Current (mA) 530 520 510 500 490 480 470 460 91 87 83 79 VBATT = 3.8V, RISET = 24.3kΩ VBATT = 3.8V, RISET = 24.3kΩ 450 75 4 4.5 5 5.5 6 6.5 7 4 4.5 5 5.5 6 Input Voltage (V) Input Voltage (V) ISET Voltage vs. Input Voltage OVP 6.5 7 1.25 ISET Voltage (V) ENB : Low VIN (10V/Div) 1.24 1.23 VBATT (2V/Div) 1.22 V CHG_SB (2V/Div) I CHG (500mA/Div) 1.21 VBATT = 3.8V, RISET = 24.3kΩ VIN = 0V to 12V, VBATT = 3.8V, RISET = 24.3kΩ 1.20 4 4.5 5 5.5 6 6.5 7 Time (500μs/Div) Input Voltage (V) DS9526A-01 April 2011 www.richtek.com 5 RT9526A Shutdown Power On ENB : Low ENB : Low VIN (5V/Div) VIN (5V/Div) VBATT (2V/Div) V CHG_SB (2V/Div) VBATT (2V/Div) V CHG_SB (2V/Div) I CHG (500mA/Div) I CHG (500mA/Div) VBATT = 3.8V, RISET = 24.3kΩ Time (500μs/Div) www.richtek.com 6 VBATT = 3.8V, RISET = 24.3kΩ Time (5ms/Div) DS9526A-01 April 2011 RT9526A Application Information The RT9526A is a fully integrated low cost single cell Liion battery charger operable in Constant Current (CC) mode or Constant Voltage (CV) mode. The CC mode current is set with the external resistor, RISET, and the CV mode voltage is fixed at 4.2V. If the battery voltage is below a typical 2.55V pre-charge threshold, the RT9526A charges the battery with a trickle current until the battery voltage rises above the pre-charge threshold. The RT9526A is capable of being powered up from AC adapter and USB (Universal Serial Bus) port inputs. Trickle CC CV 4.2V Charge Voltage ICHG_FAST 75 % ICHG_FAST Charge Current 2.8V IIMIN 16.7 % ICHG_FAST CHG_SB CHG Indication Time Figure 1. Typical Charge Profile VIN Over Voltage Protection a. Battery Pre-Charge Current The input voltage is monitored by the internal comparator. The OVP threshold is set at 7V (typ.). When the input voltage exceeds the threshold, the controller outputs a logic signal to turn off the power P-MOSFET to prevent high input voltage from damaging the electronics in the handheld system. Nevertheless, an AC input voltage over 28V will still damage the RT9526A. When the input over voltage condition is removed, the controller will enable the output again by running through soft-start. During a charge cycle, if the battery voltage is below the pre-charge threshold, the RT9526A applies a pre-charge mode to the battery. This feature revives deeply discharged cells and protects battery life. The internally determined pre-charge rate of the RT9526A is 16.7% of the constant charge current. Charger Enable Input ENB is an active-low logic input to enable the charger. Drive the ENB pin low or leave it floating to enable the charger. This pin has a 200kΩ internal pull down resistor. So when left floating, the input is equivalent to logic-low. Drive this pin high to disable the charger. b. Battery Fast-Charge Current (CC Mode) The RT9526A offers ISET pin to determine the fast-charge current via an external resistor, RISET, connected between ISET and GND. The fast-charge current can be calculated by the following equation : V ICHG_FAST = KISET x ISET (mA) RISET KSET = 9959; VSET = 1.22 (typ.) Battery Charge Current vs. RISET Battery Charge Profile The RT9526A charges a Li-ion battery under Constant Current (CC) mode or Constant Voltage (CV) mode. The constant current of ISET is set via the external resistor, RISET, and the constant voltage is fixed at 4.2V. If the battery voltage is below a typical 2.55V pre-charge threshold, the RT9526A charges the battery with a trickle current until the battery voltage rises above the pre-charge threshold. When the battery voltage reaches 4.2V, the charger enters CV mode and regulates the battery voltage at 4.2V to fully charge the battery without the risk of over charge. Battery Charge Current (mA) 1 1400 1200 1000 800 600 400 200 0 10 19 28 37 46 55 RISET (k Ω ) Figure 2 DS9526A-01 April 2011 www.richtek.com 7 RT9526A c. Battery Voltage Regulation (CV Mode) The battery voltage regulation feedback is through the BATT pin. The RT9526A monitors the battery voltage between the BATT and GND pins. When battery voltage is close to battery regulation voltage threshold, the voltage regulation phase begins and the charging current begins to taper down. When battery voltage is over battery regulation voltage threshold and charge mode stops, the RT9526A still monitors the battery voltage. Charge current is resumed when the battery voltage falls under battery regulation voltage threshold. Sleep Mode The RT9526A enters sleep mode if both AC and USB are removed from the input. This feature prevents draining the battery during the absence of input supply. Power Good This open-drain output pin is used to indicate the input voltage status. The PGB output asserts low when 1. VIN > VPOR 2. VIN − VBATT > VOS 3. VIN < VOVP CHG_SB Indication The CHG_SB pin is an open-drain output capable to at least 10mA current when the charger starts to charge and turns off when the EOC current is reached. The CHG_SB signal is interfaced either with a micro processor GPIO or an LED for indication. End-Of-Charge Current (EOC) Connect a resistor between the IMIN pin and GND to set the EOC current. The EOC current level, I IMIN, is programmable via the external resistor, RIMIN (kΩ), as shown in the following equation : www.richtek.com 8 Temperature Regulation and Thermal Protection In order to maximize charge rate, the RT9526A features a junction temperature regulation loop. If the power dissipation of the IC results in junction temperature greater than the thermal regulation threshold (115°C), the RT9526A will cut back on the charge current and disconnect the battery in order to maintain thermal regulation at around 115°C. This operation continues until the junction temperature falls below thermal regulation threshold (115°C) by the hysteresis level. This feature prevents the maximum power dissipation from exceeding typical design conditions. Selecting the Input and Output Capacitors It can be used to drive an LED or communicate to the host processor. Note that ON indicates the open-drain transistor is turned on and LED is bright. IIMIN = 10935 RIMIN Upon reaching the End-Of-Charge (EOC) current, the charger indicates charge completion via the CHG_SB pin, but the charger continues to output 4.2V voltage. Figure 1 shows the typical charge profile and the EOC/reset event. The CHG_SB signal asserts low when the trickle charge starts and changes to high at EOC. After EOC is reached, the charge current has to rise above 75% of ICHG_FAST before the CHG_SB signal is allowed to turn on again. A current surge after EOC may occur due to a load connected to the battery. (mA) In most applications, a 1μF high frequency decoupling capacitor placed in close proximity to the input is sufficient. However, depending on the power supply characteristics and cable length, it may be necessary to add an additional 10μF ceramic capacitor to the input. For the RT9526A, a small output capacitor is required for loop stability. A 1μF ceramic capacitor placed between the BATT pin and GND is typically sufficient. Thermal Considerations For recommended operating condition specifications of the RT9526A, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θJA, is layout dependent. For WDFN8L 2x3 packages, the thermal resistance, θJA, is 120°C/ W on a standard JEDEC 51-3 single-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : DS9526A-01 April 2011 RT9526A PD(MAX) = (125°C − 25°C) / (120°C/W) = 0.833W for WDFN-8L 2x3 package Layout Consideration The RT9526A is a fully integrated low cost single-cell Liion battery charger ideal for portable applications. Careful PCB layout is necessary. For best performance, place all peripheral components as close to the IC as possible. A short connection is highly recommended. The following guidelines should be strictly followed when designing a PCB layout for the RT9526A. The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. For the RT9526A packages, the derating curves in Figure 3 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W)1 0.9 ` Input capacitor should be placed close to the IC and connected to the ground plane. The trace of input on the PCB should be placed far away from the sensitive devices and shielded by the ground. ` The GND and exposed pad should be connected to a strong ground plane for heat sinking and noise protection. ` The connection of RISET should be isolated from other noisy traces. ` Output capacitor should be placed close to the IC and connected to the ground plane to reduce noise coupling. Four-Layer PCB 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 3. Derating Curve for RT9526A Package CIN should be placed near the IC to improve performance. VIN BATT R1 BATT BATT R2 VIN PGB CHG_SB ENB 1 2 3 4 COUT GND CIN The copper area connecting the resistors of ISET and IMIN should be minimized and kept far away from noise sources. 9 8 7 6 5 BATT RISET ISET IMIN GND RIMIN GND The GND plane should be connected to a strong ground plane for heat sinking and noise protection. Figure 4. PCB Layout Guide DS9526A-01 April 2011 www.richtek.com 9 RT9526A Outline Dimension D D2 L E E2 SEE DETAIL A 1 e b 2 A A1 1 2 1 A3 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. 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 0.200 0.300 0.008 0.012 D 1.900 2.100 0.075 0.083 D2 1.550 1.650 0.061 0.065 E 2.900 3.100 0.114 0.122 E2 1.650 1.750 0.065 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 8L DFN 2x3 Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. www.richtek.com 10 DS9526A-01 April 2011