AOZ1960 Multi-String Boost White LED Driver General Description Features The AOZ1960 is a high-efficiency boost regulator with integrated 55V boost switch and 30V input protection switch. It is designed to drive 6 parallel strings of multiple series-connected white LEDs for LCD backlight applications. The current of each string is individually regulated by an internal current regulator. The AOZ1960 has a wide input voltage range from 7V to 24V. The maximum LED current can be adjusted from 15mA to 30mA using an external resistor connected to ISET pin. z 7V to 24V input voltage range The AOZ1960 support two dimming control modes to enable a wide variety of applications. In analog dimming mode, the LED current can be directly adjusted through ABRT pin to achieve 10% to 100% brightness range. In digital dimming mode, a PWM signal on DBRT controls the brightness by turning the current regulators on and off. The brightness is proportional to the duty cycle of the PWM signal. z Digital PWM dimming via DBRT pin The AOZ1960 has multiple features to protect the regulator under fault conditions. An internal 30V input protection switch protects against catastrophic failure conditions such as output short-circuits. A separate over-voltage protection (OVP) loop limits the output voltage if LED strings fail open. Cycle-by-cycle over-current protection (OCP) limits the peak inductor current. Built-in soft-start minimizes the inrush current during startup. Thermal shutdown provides another level of protection. z 7mm x 4mm DFN package z Integrated 30V input switch z 55V/2A internal N-channel MOSFET z Six parallel strings z Programmable switching frequency z 500mV low dropout current regulator z Resistor programmable maximum LED current z Analog dimming via ABRT pin z Dimming range with 8-bit resolution z Cycle-by-cycle current limit z Open and short LED protection z Output over-voltage and short protection z Thermal overload protection z Internal Soft-start Applications z Notebook PC display z Tablet PC display z Desktop monitors z Portable DVD players z Digital photo frames z Car navigation display The integrated 55V power MOSFET reduces the cost and external component count, while allowing output voltages as high as 55V. Low dropout voltage of LED current regulator (500mV) minimizes power loss. In addition, automatic pulse skipping operation improves efficiency at light loads. The AOZ1960 features programmable switching frequency allows for trade-offs between solution size and electrical efficiency. The AOZ1960 is available in a thermally enhanced 24-pin 7mm x 4mm DFN package and operates over the temperature range of -40°C to +85°C. Rev. 1.0 August 2010 www.aosmd.com Page 1 of 20 AOZ1960 Typical Application Circuit L1 D1 10μH R9 1kΩ LIN LX R1 500kΩ IN INPUT 6V TO 24V OVP C1 22μF C4 4.7μF R2 12.5kΩ C8 4.7μF AGND BIAS C5 1μF PGND AOZ1960DI R3 100kΩ FAULT COMP R5 10kΩ FLT C6 100nF ENABLE EN ISET ANALOG DIMMING ABRT DIGITAL DIMMING DBRT R4 46.4kΩ LED1 LED2 FSET LED3 R6 84.5kΩ LED4 LED5 LED6 Ordering Information Part Number Ambient Temperature Range Package Environmental AOZ1960DI -40°C to +85°C 7 x 4 DFN-24 Green Product AOS Green Products use reduced levels of Halogens, and are also RoHS compliant. Please visit www.aosmd.com/web/quality/rohs_compliant.jsp for additional information. Rev. 1.0 August 2010 www.aosmd.com Page 2 of 20 AOZ1960 Pin Configuration AOZ1960DI IN 1 EN 2 24 LIN 23 LIN LIN BIAS 3 22 LED1 ISET 4 21 LED2 AGND 5 20 LED3 COMP 6 19 AGND AGND FSET 7 18 LED4 AGND 8 17 LED5 ABRT 9 16 LED6 DBRT 10 15 PGND LX FLT 11 14 LX OVP 12 13 LX 7x4 DFN-24 (Top View) Rev. 1.0 August 2010 www.aosmd.com Page 3 of 20 AOZ1960 Pin Description Pin Number Pin Name 1 IN Input Supply Pin. 2 EN Enable Input. Pull EN above 2V to enable the LED driver and pull EN below 0.8V to disable the LED driver. 3 BIAS Internal 5V Linear Regulator Output. Connect a minimum 0.22μF ceramic capacitor from BIAS to ground. 4 ISET LED Current Set Pin. Connect a resistor from ISET to ground to set the nominal LED current (100% brightness) for each string. 5, 8, 19 AGND Analog ground. 6 COMP Compensation Pin. COMP is the output of the internal error amplifier. Connect a RC network from COMP to ground to compensate the control loop. 7 FSEL Frequency Select Pin. Connect FSEL to ground via a resistor to set the switching frequency. 9 ABRT Analog Brightness Control Input. ABRT controls the LED brightness by adjusting the LED current in proportion to ABRT voltage. The input range of ABRT is between 0 to 2V. When VBRT is below 0.2V, the LED current is 10% of the nominal setting. When BRT voltage is 2V or above, the LED current is 100% of the normal setting. 10 DBRT PWM Brightness Control Input. DBRT controls the LED brightness by turning the LED on and off using a PWM signal. The brightness is proportional to the PWM duty. 11 FLT Fault Output. FLT is an open-drain output. Connect a pull-up resistor between BIAS and FLT. 12 OVP Over-voltage protection Input. Use a voltage divider to set the boost regulator output over-voltage protection threshold. 13, 14 LX 15 PGND Power Ground. 16 LED6 Internal LED Current Regulator 1 Input. 17 LED5 Internal LED Current Regulator 2 Input. 18 LED4 Internal LED Current Regulator 3 Input. 20 LED3 Internal LED Current Regulator 4 Input. 21 LED2 Internal LED Current Regulator 5 Input. 22 LED1 Internal LED Current Regulator 6 Input. 23, 24 LIN Rev. 1.0 August 2010 Pin Function Boost Regulator Switching Pin. LX is the drain of the 55V internal boost switch. Boost Regulator Input Pin. LIN is drain of the input protection switch. www.aosmd.com Page 4 of 20 AOZ1960 Block Diagram LX INPUT VIN 5V Regulator Bias Generator EN S Q OVP VLIM UVLO Comp BIAS OSC UVLO Threshold FLT R PWM Comp Fault Logic COMP Gm EN Error Amp TSD FSEL VCC Ref Min LED1 Current Regulator 1 ISET Analog Dimming Control ABRT PWM Dimming Control DBRT AOZ1960 Rev. 1.0 August 2010 Current Regulator 2 LED2 Current Regulator 3 LED3 Current Regulator 4 LED4 Current Regulator 5 LED5 Current Regulator 6 LED6 www.aosmd.com Page 5 of 20 AOZ1960 Absolute Maximum Rating Maximum Operating Ratings Exceeding the Absolute Maximum Ratings may damage the device. The device is not guaranteed to operate beyond the Maximum Operating Ratings. Parameter Rating Parameter Rating IN, LIN to AGND -0.3V to +28V Supply Voltage (VIN) LX to AGND -0.3V to +60V Ambient Temperature (TA) LED1, LED2, LED3, LED4, LED5, LED6 to AGND -0.3V to +40V Package Thermal Resistance 7x4 DFN-24 (ΘJA) BIAS, EN, FLT, FSEL, ISET, COMP, ABRT, DBRT, OVP, to AGND Storage Temperature (TS) ESD Rating 7V to 24V -40°C to +85°C 45°C/W -0.3V to +6V -65°C to +150°C (1) 2kV Note: 1. Devices are inherently ESD sensitive, handling precautions are required. Human body model rating: 1.5kΩ in series with 100pF. Electrical Characteristics TA = 25°C, VIN = 3.3V, unless otherwise specified. Symbol VIN Parameter Conditions IN Supply Voltage 10 LEDs per channel (3.2V/20mA type) IIN_ON IN Quiescent Current EN = 5V IIN_OFF IN Shutdown Current EN = AGND VBIAS BIAS Regulation Voltage Min. Typ. 7 4.7 Max. Units 24 V 2.5 mA 10 40 μA 5.0 5.3 V 4.5 VBIAS_UVLO BIAS UVLO Threshold VEN = 5V 4.3 VBIAS_HYS BIAS UVLO Hysteresis VEN = 5V 700 V mV INPUT SWITCH IN to LIN On Resistance 50 IN to LIN Leakage 80 mΩ 1 μA LED CURRENT REGULATION ILED_MAX VLED_ LED_ Full Scale Current RISET = 46.4kΩ 20.0 mA Minimum LED_ Regulation Voltage ILED_ = 20mA 500 mV LED_ Leakage Current VLED_ = 36V Current Matching Accuracy ILED_ = 20mA -3 200 μA +3 % BRIGHTNESS CONTROL DBRT Input High Voltage 2 V DBRT Input Low Voltage 0.6 V DBRT Input Bias Current 200 nA DBRT Input Frequency(2) 2 20 kHz ABRT Input Range 0 5.5 V ABRT 10% Scale Voltage 0.25 V ABRT Leakage Current 200 nA ABRT Full Scale Voltage Rev. 1.0 August 2010 1.9 www.aosmd.com V Page 6 of 20 AOZ1960 Electrical Characteristics (Continued) TA = 25°C, VIN = 3.3V, unless otherwise specified. Symbol Parameter Conditions Min. Typ. Max. Units 800 1000 1200 kHz OSCILLATOR fSW Switching Frequency DMAX Maximum Duty Cycle RSEL = 84.5kΩ 87 % POWER SWITCH RON_LX LX On Resistance 0.14 LX Leakage Current 0.20 Ω 1 μA PROTECTIONS ILIM VOVP VOVP_HYS IOVP Current Limit 2.5 OVP Threshold Voltage 1.18 OVP Hysterisis 1.25 1.33 70 OVP Input Bias Current μA Ω 300 FLT Leakage Current V mV 0.2 FLT On Resistance TSD A 100 nA Thermal Shutdown Threshold 145 °C Thermal Shutdown Hysteresis 35 °C LOGIC INPUT VEN_H EN Logic High Threshold VEN_L EN Logic Low Threshold VEN_HYS EN Input Hysteresis IEN EN Leakage Current 2.0 V 0.6 180 VEN = 5V FSEL Leakage Current V mV 1 μA 1 μA Note: 2. DBRT Input Frequency is guaranteed by design only. Rev. 1.0 August 2010 www.aosmd.com Page 7 of 20 AOZ1960 Typical Operating Characteristics LED Current Regulation 20.6 95 20.4 LED Current (mA) Efficiency (%) Electrical Efficiency 100 90 85 80 20.2 20.0 19.8 19.6 75 70 5 19.4 10 15 20 25 30 5 10 Input Voltage (V) 20 25 30 Analog Dimming Linearity PWM Dimming Linearity 24.0 24.0 20.0 20.0 LED Current (mA) Average LED Current (mA) 15 Input Voltage (V) 16.0 12.0 8.0 4.0 16.0 12.0 8.0 4.0 0.0 0 10 20 30 40 50 60 70 80 90 100 0.0 0.0 PWM Duty Cycle (%) Rev. 1.0 August 2010 0.4 0.8 1.2 1.6 2.0 2.4 Analog Dimming Votlage (V) www.aosmd.com Page 8 of 20 AOZ1960 Typical Operating Characteristics (Continued) Startup Waveforms (Vin = 12V) Switching Waveforms (Vin = 12V) EN 5V/div LZ 20V/div Vout 20V/div IL 500mA/div IL 500mA/div 2ms/div 500ns/div Switching Waveforms (Vin = 7V) Switching Waveforms (Vin = 24V) LX 20V/div LX 20V/div IL 500mA/div IL 500mA/div 500ns/div Rev. 1.0 August 2010 500ns/div www.aosmd.com Page 9 of 20 AOZ1960 Typical Operating Characteristics (Continued) 10% DPWM 50% DPWM DPWM Signal 5V/div DPWM Signal 5V/div LX 20V/div LX 20V/div LED Current 20mA/div LED Current 20mA/div 200μs/div 200μs/div 90% DPWM DPWM Signal 5V/div LX 20V/div LED Current 20mA/div 200μs/div Rev. 1.0 August 2010 www.aosmd.com Page 10 of 20 AOZ1960 Typical Operating Characteristics (Continued) Output Short to GND (Hard-short) Output Short to GND (Soft-short) Vout 20V/div Vout 20V/div LIN 10V/div LIN 10V/div LX 20V/div LX 20V/div 500μs/div 1ms/div LED Short Protection LED Open Protection OVP Voltage 1V/Div OVP Voltage 1V/Div Channel Voltage 10V/Div Channel Voltage 10V/Div Output Voltage 20V/Div Output Voltage 20V/Div Fault Voltage 5V/Div 20ms/div Rev. 1.0 August 2010 Fault Voltage 5V/Div 100ms/div www.aosmd.com Page 11 of 20 AOZ1960 Detailed Description AOZ1960 is a 6-string boost LED driver with integrated boost switch and input protection switch. The input voltage range is from 7V to 24V and output voltage can go as high as 55V and drive up to 12 LEDs in series for each string. LED current of each string is individually regulated by an internal current regulator to achieve ±3% current matching. AOZ1960 supports two brightness control methods: analog dimming and digital dimming. In analog dimming mode, the LED current can be directly adjusted through ABRT pin to achieve 10% to 100% brightness range. In digital dimming mode, a PWM signal on DBRT controls the brightness by turning the current regulators on and off. The brightness is proportional to the duty cycle of the PWM signal. The maximum LED current is set with an external resistor in ISET pin. AOZ1960 features multiple protection functions. The cycle by cycle over-current protection (OCP) limits the inductor peak current to less than 2.5A. The input protection switch turns off when a short circuit is detected at the output. The cycle by cycle over-voltage protection (OVP) prevents the output voltage from running away when LED strings are open. OVP threshold can be adjusted using a voltage divider. The maximum allowed output voltage is 55V. Thermal shutdown function provides another layer of protection when junction temperature reaches 145ºC. Internal soft-start effectively limits the inrush current during startup. In addition, AOZ1960 provides an open-drain fault indicator when a fault such as open LED, shorted LED, short circuit, or over temperature occurs. Normal Operation AOZ1960 boost LED driver uses constant frequency PWM control architecture. Different from regular boost regulators which regulate output voltage, AOZ1960 regulates LED current. There are six internal current regulators. The minimum of the six current sense signals is fed to a transconductance error amplifier and compared with an internal reference. The PWM comparator compares the error amplifier output with the inductor current ramp signal to set a flip-flop, which turns off the boost switch. The boost switch turns on when the oscillator clock comes, connecting the inductor between the input supply and ground. The inductor current linearly ramps up storing energy in the magnetic field. The boost switch is turned off by PWM comparator. When the boost switch is off, the inductor current freewheels through the output Schottky diode, connecting the inductor between the input supply and output. The inductor current linearly ramps down and Rev. 1.0 August 2010 energy stored in the inductor is transferred to the output. Therefore, if minimum of the six current sense signals is below internal reference, AOZ1960 will keep boosting the output voltage until it reaches regulation. This control method ensures the output voltage is just high enough to drive all six LED strings without wasting any extra power. Input Protection Switch (LIN) A major problem of traditional boost regulators is that they cannot protect against output short-circuit fault. When the output is shorted to ground, short-circuit current will flow directly from input supply, through the inductor and Schottky diode, to ground. Typically a fuse is required for output short-circuit protection. AOZ1960 solves this issue by integrating a high-voltage (30V) low on-resistance (50mΩ) P-channel input protection switch. The input switch is connected between the input supply (IN) and boost inductor (LIN). In normal operation, the switch is fully turned on connecting the input supply to the inductor. The input switch is turned off whenever AOZ1960 detects the output voltage is below the input. To ensure startup, a startup resistor (1kΩ) should be connected between IN (source of input switch) and LIN (drain of input switch) to make sure output is close to input before AOZ1960 is enabled. Linear Regulator (BIAS) AOZ1960 has an internal 5V linear regulator that powers all the internal circuitry including power MOSFET driver. BIAS is the output of the internal regulator. Connect a 1μF or larger ceramic capacitor between BIAS and ground. The regulator is used for internal circuitry only. Do not connect any external load to BIAS pin. The regulator is enabled when EN is logic high. If BIAS voltage is above UVLO threshold (4.3V), AOZ1960 is enabled: the input switch is turned on and the boost regulator starts switching. If BIAS voltage is below UVLO threshold, AOZ1960 remains off. Current Regulators (LED1 to LED6) There are six internal current regulators. Each consists of a driver, a MOSFET, and a current sense resistor. The driver controls the MOSFET gate voltage based on the current sense feedback to achieve current regulation. When current sense signal is below a preset regulation point, the driver will reduce the MOSFET drain-to-source voltage by increasing gate voltage, allowing more voltage across the LED string. When current sense signal is above the regulation point, the driver will increase the MOSFET drain-to-source voltage by lowering gate www.aosmd.com Page 12 of 20 AOZ1960 When one or two LEDs in a string are shorted, the current regulator in that string takes the additional voltage drop and continues to regulate LED current. If four or more LEDs in a string are shorted, the current regulator in that string is disabled and AOZ1960 ignores the current feedback signal from that string. Analog Dimming AOZ1960 supports analog dimming through ABRT pin. In analog dimming mode, LED current linearly changes with ABRT voltage. The current adjustment range is from 10% to 100% of the full brightness LED current, corresponding to 0.2V to 2V on ABRT. When ABRT is below 0.2V, LED current remains at 10%. When ABRT is above 2V, LED current remains at 100%. To disable analog dimming, connect ABRT to a voltage higher than 4V. Applications Information LED Current Setting The maximum LED current is set with an external resistor in ISET pin. The current can be set from 15mA to 25mA. RSET can be calculated using Eq.1: 928 I LED = -------------R SET 30 RSET (Ω) ILED (mA) 62k 15 46.4k 20 37k 25 AOZ1960DI RISET vs. LED Current 25 20 15 10 DPWM Dimming AOZ1960 supports digital PWM dimming through DBRT pin. In DPWM dimming mode, current regulators are turned on and off by a PWM signal on DBRT. The brightness is proportional to the duty cycle of the PWM signal. For example, the duty cycle can be adjusted from 3% to 100% for 20kHz DPWM frequency. (Eq. 1) To set the LED current from 15mA to 25mA, use the figure below. LED Current (mA) voltage, reducing voltage across the LED string. There are six internal current regulators. Each consists of a driver, a MOSFET, and a current sense resistor. The driver controls the MOSFET gate voltage based on the current sense feedback to achieve current regulation. When current sense signal is below a preset regulation point, the driver will reduce the MOSFET drain-to-source voltage by increasing gate voltage, allowing more voltage across the LED string. When current sense signal is above the regulation point, the driver will increase the MOSFET drain-to-source voltage by lowering gate voltage, reducing voltage across the LED string. 5 0 36 41 46 51 RISET (kΩ) 56 61 Input Capacitor The input capacitor is connected to VIN and GND pins of the AOZ1960 to filter and maintain a steady input DC voltage. The voltage rating of input capacitor must be greater than maximum input voltage plus ripple voltage. The RMS current rating should be greater than the inductor ripple current: The input capacitor value should be 22μF or higher for normal operation. The capacitor can be electrolytic, tantalum or ceramic. The input capacitor should be place as close as possible to the IC; if not possible, a 0.1μF decoupling ceramic capacitor between VIN pin and GND in close proximity. Rev. 1.0 August 2010 www.aosmd.com Page 13 of 20 AOZ1960 Inductor The inductor is used to supply higher output voltage when the NMOS switch is off. For a given input and output voltage, the inductance and switching frequency determine the inductor ripple current, defined as, V OUT – V IN ΔI L = ------------------------------ × I OFFPULSE L (Eq. 2) V IN ⎞ (Eq. 6) ⎛ ⎜ 1 – ---------------⎟ V OUT⎠ ⎝ ΔV O = I L × -----------------------------f × C OUT The peak inductor current is: ΔI L I Lpeak = I IN + -------2 When low ESR ceramic output capacitors are used, the impedance of the capacitor at the switching frequency dominates. Output ripple is mainly caused by capacitor value and load current with the frequency, input and output voltage. The output ripple voltage calculation can be simplified to: (Eq. 3) An output capacitor with the value of 10μF is usually sufficient to meet most applications requirements. Higher boost inductance will yield lower inductor ripple current but this will require an inductor with higher saturation current rating at the highest operating temperature. Lower ripple current helps to reduce inductor core losses. It also reduces RMS current through inductor, switch and freewheeling diode, which results in less conduction loss. The peak to peak ripple current of the inductor should be between 30% to 50% of input current. An inductor value of 10μH is recommended for 10 to 12 LED operation. Output Boost Diode Output Capacitor AOZ1960 employs constant off time control and does not require slope compensation. The right half plane zero that is often problematic in all most boost converters has no significant effect in the AOZ1960’s frequency response. The RHP zero has the effect of a zero in the gain causing +20dB/decade on the roll off, but has the effect of a pole in the phase, subtracting 90o in the phase. The RHP zero can cause instability issues if the bandwidth is higher, therefore it is recommended to lower the bandwidth by one half frequency of the RHP zero. The output ripple voltage specification is key in the selection of the output capacitor. In a boost converter, the output ripple voltage is determined by load current, input voltage, output voltage, switching frequency, output capacitor value and ESR. It can be calculated by the equation below: The voltage rating of the output capacitor must be higher than the intended output boost voltage plus the output ripple voltage. Therefore some de-rating is required for ensure long term reliability. V IN ⎞ ⎞ ⎛ ⎛ ⎜ 1 – ---------------⎟ ⎟ ⎜ V OUT⎠ ⎟ ⎝ ⎜ VO ΔV O = I LED × ⎜ --------- × ESR CO + ------------------------------⎟ f × C OUT ⎟ ⎜ V IN ⎜ ⎟ ⎝ ⎠ (Eq. 4) A low forward drop Schottky with fast transit time should be selected to improve converter efficiency. Its current rating should be higher than the peak current that commutates during its conduction interval. In addition, the rated breakdown voltage should be higher than the application boost voltage plus some margin of transient overshoot. Loop Compensation The RHPZ can be calculated as follows: 2 D P ( I LOAD ) × R OUT ( I LOAD ) f RHPZ = --------------------------------------------------------------------------2π × L (Eq. 7) where, D P ( I LOAD ) = 1 – D ( I LOAD ) (Eq. 8) V IN f = --------------------------------- (Eq. 5) V OUT × t OFF V OUT ( I LOAD ) R OUT ( I LOAD ) = ------------------------------------ (Eq. 9) I LOAD where, ILED is the load current or LED current, COUT is output capacitor value, and ESRCO is the Equivalent Series Resistor of output capacitor. Rev. 1.0 August 2010 www.aosmd.com Page 14 of 20 AOZ1960 The cross over frequency in typical applications should be a fifth of the frequency of the RHPZ location. f RHPZ (Eq. 10) f CROSS = ---------------5 The objective of compensation is to shape the gain and phase of the converter’s closed loop transfer function ultimately to achieve stability. The compensation pin of AOZ1960 is serves as the output of the voltage transconductance error amplifier. In a typical application, a series capacitor and resistor network connected to the COMP pin creates the pole-zero compensation network enabling a very stable high-bandwidth control loop. The closed loop transfer function: s(w) G M × R EA × ⎛ 1 + ------------⎞ (Eq. 11) ⎝ wz ⎠ H ( w ) = -----------------------------------------------------------s ( w -)⎞ ⎛ 1 + ----------⎝ w ⎠ Circuit Layout and Thermal management To minimize unwanted noise and voltage transients, careful PCB layout must be exercised to reduce the main current loop areas. This optimization helps to reduce the switching noise associated with current commutation in the circuit and also helps to improve the efficiency of the converter. In addition to reducing the main power loops it is also important to keep sensitive nodes such as compensation and enable pins in quieter ground areas away from the main power ground connection. In the AOZ1960 boost LED driver circuit, there are two main switching loops that pulsate current flow when the NMOS turns on and off. The first loop starts when the NMOS switches on, the input current or inductor current ramps positively through the inductor and NMOS device. During this interval, the output boost diode is reversed biased with its anode pulled low to ground. Since the NMOS is internal in the AOZ1960 much of the parasitic inductance is made from the power return to the ground connection of the input capacitors. P1 Based on the duty cycle arrangement, the controller will signal the internal driver to turn-off the NMOS to initiate the fixed off time. After the NMOS is fully off, the continuous inductor current continues to freewheel through the output boost diode. The key parasitics in this loop consist of PCB trace inductance from the anode to the LX connection and lastly the connection from cathode to power ground return. Both input and output capacitors should be ceramic in type to achieve low ESR and ESL specifications. The corresponding pole is: 1 f P = --------------------------------------------------2π × R EA × C COMP (Eq. 12) The corresponding zero is: 1 f Z = ---------------------------------------------------------------- (Eq. 13) R COMP × R EA ------------------------------------× C COMP R COMP + R EA Below are some key tips in minimize the two main switching loops and improving noise immunity: where, GM is the error amplifier transconductance, which is 100μA / V, REA = 5MΩ, CCOMP is compensation capacitor, RCOMP is compensation resistor. A compensation resistor of 10kΩ and compensation capacitor of 100nF. 1. Maximized the copper area to the GND pin and the VIN pin for improved thermal dissipation. 2. Incorporate a ground plane on both top and bottom layers if possible. 3. To minimize trace inductance connects the device to the LX pin with a short wire and adoption of this technique for connections to the output capacitor and ground. 4. Add thermal vias for the GND pad for improved thermal dissipation between top and bottom layers. 5. To maximize thermal dissipation pour incorporate copper planes in unused areas. 6. Route sensitive signals such as OVP and COMP pins a far distance away from the LX switching node and pin. Rev. 1.0 August 2010 www.aosmd.com Page 15 of 20 AOZ1960 In the AOZ1960 boost regulator circuit, the major power dissipating components are the AOZ1960 and output inductor. The total power dissipation of converter circuit can be measured by difference between the input and output power. P total_loss = ( V IN × I IN ) – ( V O × I O ) (Eq. 14) The power dissipation of inductor can be approximately calculated by input current and DCR of inductor. P inductor_loss = I IN 2 × R inductor × 1.1 (Eq. 15) The actual AOZ1960 junction temperature can be calculated with power dissipation and the thermal impedance from junction to ambient. T junction = ( P total_loss – P inductor_loss ) × Θ + T amb (Eq. 16) The maximum junction temperature of AOZ1960 is rated at 145ºC The thermal performance of the AOZ1960 is strongly affected by the PCB layout and proper care should be taken to ensure that the device will operate under the recommended environmental conditions. Rev. 1.0 August 2010 www.aosmd.com Page 16 of 20 AOZ1960 Package Dimensions, DFN 7x4 24L EP3_S D A B D/2 aaa C 2x E/2 E aaa C 2x TOP VIEW 6 ccc C A3 A C SEATING PLANE A1 5 ddd C SIDE VIEW 4 b bbb C A B PIN#1 IDA e 1 R L E2 3 INDEX AREA (D/2xE/2) D2 D3 L1 BOTTOM VIEW Note: 1. Dimensioning and tolerancing conform to ASME Y14.5M-1994. 2. All dimensions are in millimeters. 3. The location of the terminal #1 identifier and terminal numbering convention conforms to JEDEC publication 95 SPP-002. 4. Dimension b applies to metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. If the terminal has the optional radius on the other end of the terminal, the dimension b should not be measured in that radius area. 5. Coplanarity applies to the terminals and all other bottom surface metallization. 6. Drawing shown are for illustration only. Rev. 1.0 August 2010 www.aosmd.com Page 17 of 20 AOZ1960 Package Dimensions, DFN 7x4 24L EP3_S (Continued) RECOMMENDED LAND PATTERN 0.5 0.3 1.7 0.25 1.7 3.6 2.7 1.8 0.5 2.2 0.3 2.4 2.4 UNIT: mm Dimensions in millimeters Symbols A A1 A3 b D D2 D3 E E2 e L L1 R aaa bbb ccc ddd Min. 0.80 0.00 0.17 1.975 1.625 2.650 0.300 – Nom. 0.90 0.02 0.20 REF 0.25 7.00 BSC 2.200 1.700 4.00 BSC 2.700 0.50 BSC 0.400 0.200 0.45 REF 0.15 0.10 0.10 0.08 Max. 1.00 0.05 0.35 2.225 1.775 2.750 0.500 – Dimensions in inches Symbols A A1 A3 b D D2 D3 E E2 e L L1 R aaa bbb ccc ddd Min. 0.031 0.000 Nom. Max. 0.035 0.039 0.001 0.002 0.008 REF 0.007 0.010 0.014 0.276 BSC 0.078 0.087 0.088 0.064 0.067 0.070 0.157 BSC 0.104 0.106 0.108 0.020 BSC 0.012 0.016 0.020 – 0.008 – 0.018 REF 0.006 0.004 0.004 0.003 l Rev. 1.0 August 2010 www.aosmd.com Page 18 of 20 AOZ1960 Tape and Reel Dimensions, DFN 7x4 24L EP3_S Tape P1 D1 T P2 E1 E2 E B0 D0 K0 A0 Feeding Direction P0 UNIT: MM Package A0 B0 K0 D0 DFN7x4 (12 mm) 7.4 ±0.1 4.4 ±0.1 1.0 ±0.1 1.55 ±0.05 D1 1.55 ±0.05 E 12.0 ±0.3 E1 E2 P0 P1 P2 1.75 ±0.10 5.5 ±0.1 12.0 ±0.1 4.0 ±0.1 2.0 ±0.1 T 0.30 ±0.05 Reel W1 S G N M K V R H W UNIT: MM Tape Size 12 mm Reel Size Ø330 M N Ø330 Max. Ø100 Min. W W1 H K S G R V 12.4 +2.0 -0.0 18.4 Max. Ø13.0 +0.5 -0.2 10.1 Min. 1.5 Min. --- --- --- Leader/Trailer and Orientation Trailer Tape 300mm min. or 75 Empty Pockets Rev. 1.0 August 2010 Components Tape Orientation in Pocket www.aosmd.com Leader Tape 500mm min. or 125 Empty Pockets Page 19 of 20 AOZ1960 Part Marking AOZ1960DI (7x4 DFN-8) Z1960DI FAYWLT Part Number Code Assembly Lot Code Fab & Assembly Location Year & Week Code This data sheet contains preliminary data; supplementary data may be published at a later date. Alpha & Omega Semiconductor reserves the right to make changes at any time without notice. LIFE SUPPORT POLICY ALPHA & OMEGA SEMICONDUCTOR PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. Rev. 1.0 August 2010 2. A critical component in any component of a life support, device, or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.aosmd.com Page 20 of 20