AOZ1977AI

AOZ1977 High Voltage LED Driver IC General Description Features The AOZ1977 is a high-efficiency LED driver controller for high voltage LED backlighting applications. It is designed to drive a high-brightness LED light bar in LED TV applications. The AOZ1977 can support a wide range of input and output voltages. The input bias voltage of the AOZ1977 is from 8 V to 30 V.  8 V to 30 V input bias voltage The AOZ1977 has multiple features to protect the regulator under fault conditions. A control pin can disable an external switch to disconnect the LEDs current path from the output in PWM dimming or under catastrophic failure conditions. Cycle-by-cycle current protection limits the peak inductor current. Thermal shutdown provides an additional level of protection.  500 mV feedback regulation Low feedback voltage (500 mV) helps reduce power loss.  SO-16 package  Up to 16 V driving capability at GATE pin and DPWM pin.  Disconnect control pin for PWM dimming or fault conditions.  Bi-directional clock synchronization  8 bit PWM dimming resolution  Cycle-by-cycle current limit  Output over-voltage protection  LED short and open protection  Thermal shutdown protection The AOZ1977 features a sync function to allow for synchronization with an external clock or multiple AOZ1977 devices. Applications  LCD TV LED backlight The AOZ1977 is available in a standard SO-16 package and operates over the -40 C to +85 C temperature range.  Monitor LED backlight Typical Application PVIN L1 D1 C1 DBR RT C2 AOZ1977 8V-30V C C3 C4 Q1 RS S CAuto 1 VIN 2 FB 16 VDD 3 ISET 15 4 GATE COMP 14 GND DBRT 13 5 CS 6 AUTO 7 OSC 8 SYNC OVP 12 DPWM 11 VREF 10 ILIM Rov1 Q2 9 R RL1 Rosc Rr1 Rc RF FB Cc R RL2 Rr2 Rov2 SYNC Rev. 2.1 May 2012 www.aosmd.com Page 1 of 16 AOZ1977 Ordering Information Part Number Ambient Temperature Range Package Environmental AOZ1977AI -40 °C to +85 °C SOIC-16 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. Pin Configuration VIN 1 16 FB VDD 2 15 ISET GATE 3 14 COMP GND 4 13 DBRT CS 5 12 OVP AUTO 6 11 DPWM OSC 7 10 VREF SYNC 8 9 ILIM SOIC-16 (Top View) Pin Description Pin Number Pin Name Pin Function 1 VIN Input supply pin. 2 VDD Internal 8 V linear regulator output pin for date driver. Connect a minimum 0.22 F ceramic capacitor from VDD to ground. 3 GATE External boost NMOS gate controller pin. Connect to the gate of external NMOS switch. 4 GND Ground pin. 5 CS 6 AUTO Auto restart mode control for protection. Connect appropriate capacitor to set desired Auto restart time or connect to GND for latch off. 7 OSC Frequency set pin. Connect OSC to ground via a resistor to set the switching frequency. 8 SYNC NMOS switch current sense pin. Frequency synchronous pin. Connect SYNC to external clock for desired switching frequency or connect to multiple controllers for phase locked frequency synchronization. 9 ILIM Current limit set pin. 10 VREF Reference voltage. 11 DPWM Fault and dimming control output pin. DPWM = High for LED connect. DPWM = Low for LED disconnect. Connect to the gate of external NMOS switch. 12 OVP Over-voltage feedback input pin. Use a voltage divider to set the boost regulator output over-voltage protection threshold. 13 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 cycle. 14 COMP Compensation pin. COMP is the output of the internal error amplifier. For loop compensation connect a RC network from COMP to ground. 15 ISET 16 FB Rev. 2.1 May 2012 LED current set pin. Connect ISET to VREF resistor divider to set the LED current level. Feedback input pin. Connect to sense resistor at LED string. www.aosmd.com Page 2 of 16 AOZ1977 Pin Functions Pin 1: VIN PIN 6: AUTO This is the input power for the controller IC. If the input of the boost converter is less than 30 V, VIN can be connected directly to the boost supply voltage. If the boost supply voltage is higher than 30 V, a separate supply rail between 8 V to 30 V is required for the VIN pin. It is recommended that an RC filter is added between VIN and the boost supply voltage if they are connected directly. This is the mode control for fault condition. The selection of control when under fault condition is either auto restart mode or latch-off mode. For latch-off mode, this pin should be connected directly to ground. For auto restart mode, this pin should connect a capacitor to ground. The auto restart period will be determined by the following equation: Please note that when VIN is not directly connected to the boost supply voltage, proper power up sequence will be required. Boost supply voltage must be ready before powering up VIN. There is no power down sequence required. Pin 2: VDD This is the output of an internal 8 V regulator. It requires a 2.2 F decoupling capacitor to be connected to ground. The internal regulator can be over-driven by an external supply between 8 V to 16 V if higher gate drive is desired. PIN3: GATE This is the driver output for the gate of the boost NMOS switch. The GATE = high voltage is equal to VDD voltage. It is recommended to add a 1 resistor between this pin and the NMOS gate. The resistor value can be optimized depending on the switching frequency and selection of the NMOS switch. PIN 4: GND This is the signal and power ground for the IC controller. It is recommended that all the low current paths are connected to this pin as close as possible to the IC controller. It is not recommended to connect any output or input filter capacitors and any current sense resistors to this pin directly. The IC controller ground should be an island around the IC connected to the PWR GND at a single point in the layout. PIN 5: CS This is the input for peak current sense. This pin serves the functions of current feedback, peak current limit detection, and fault current detection. The pin current limit is set by the voltage defined at PIN 9 ILIM. The current limit is defined as voltage at ILIM divided by the sense resistor connected from this pin to ground. If the CS pin detect a fault current detection such as short circuit condition, it will trigger a fault signal. The IC controller sets to either latch-off mode or auto restart mode depends on the setting at PIN 6 AUTO. Rev. 2.1 May 2012 C  AUTO  T AUTORESTART = --------------------------1.25uA PIN 7: OSC OSC is the pin to select the switching frequency for the boost controller. A resistor should be connected between this pin to ground. The switching frequency is determined by the following equation: 1 F SW = ----------------------------------------R OSC   10pF It is recommended that the switching frequency for normal operation is between 50 kHz to 350 kHz. Pin 8: SYNC This is a bidirectional pin for oscillator clock synchronization. Clock synchronization will choose either the internal clock or the external clock through this pin, whichever is faster. The faster external clock must be ready before power is applied to this IC controller. If the internal clock is faster, the SYNC pin will have the same frequency as the internal clock. When multiple IC controllers are used in the design, it is recommended to connect all SYNC pins together. This will reduce the interference of “beat” frequencies associated with multiple switching frequencies. PIN 9: ILIM This is the current limit set point. The voltage at this pin will determine the CS current limit threshold detected at PIN 5: CS. The voltage can be derived from a resistor divider from the 1.2 V reference voltage at PIN 10: VREF. To minimize power consumption, it is recommended that the total resistance for the divider is approximately 20 kΩ. PIN 10: VREF This is a 1.2 V voltage reference for all external bias. This reference voltage can be used for PIN 15: ISET and PIN 9: ILIM bias. www.aosmd.com Page 3 of 16 AOZ1977 PIN 11: DPWM PIN 14: COMP This is the driver output for the gate of the LED current control NMOS switch. DPWM = low if PIN13: DBRT signal is low or fault condition is triggered. DPWM = high if PIN 13: DBRT signal is high under normal operation. The high voltage is equal to VDD voltage. It is recommended to add a 1 Ω resistor between this pin and the NMOS gate. The resistor value can be optimized depending on the switching frequency and selection of the NMOS. This is for feedback loop compensation. It is the output of the error amplifier that controls PWM logic for the boost controller. An RC network should be used to generate the compensation for boost feedback loop. PIN 12: OVP This is the input for LED Over-Voltage Protection. OVP monitors the LED output voltage through a resistor divider. When the voltage at this pin is higher than 1 V, the controller will stop switching immediately until the voltage at this pin is below 0.8 V. PIN 15: ISET This is for full scale LED current setting. A reference voltage between 0.5 V and 0.8 V should be applied to this pin. The voltage can be derived from a resistor divider from the 1.2 V reference voltage at PIN 10: VREF. To minimize power consumption, it is recommended that the total resistance for the divider is approximately 20 kΩ. The FB voltage will regulate to this voltage level. The full scale LED current is derived by the FB voltage divided by the Sense resistor. PIN 16: FB PIN 13: DBRT This is the input for digital brightness control. A PWM logic signal is applied to this pin to vary the brightness of the LED. The brightness of the LED is proportional to the duty cycle of the PWM logic signal. The input signal will control the output driver at DPWM pin. This input pin cannot be left floating. Rev. 2.1 May 2012 This is the feedback input for boost controller. This pin should connect to a resistor that senses the LED current. The FB voltage will be regulated to ISET voltage to determine the desired LED current when LED current control NMOS switch is on. www.aosmd.com Page 4 of 16 AOZ1977 Block Diagram OVP Freq Set Driver LDO Control LDO 1V Bias Generator Oscillator OSC VIN OV Protect VDD UVLO Freq Sync SYNC Thermal Detect Driver GATE Driver DPWM Logic Controller OCP ILIM DBRT Detect DBRT Isense CS Auto-restart Detection PWM Control GND FB EA Amp 1.2V Ref ISET Buffer VREF AOZ1977 AUTO COMP Absolute Maximum Ratings Recommended Operating Conditions Exceeding the Absolute Maximum Ratings may damage the device. The device is not guaranteed to operate beyond the maximum Recommended Operating Conditions. Parameter Rating Parameter VIN to GND -0.3 V to +32 V Supply Voltage (VVIN) GATE, DPWM to GND -0.3 V to +16 V Ambient Temperature (TA) VDD to GND -0.3 V to +16 V Package Thermal Resistance SOIC-16 (JA)(2) DBRT, OSC, ISET, COMP, FB, AUTO, SYNC, CS, ILIM, VREF, OVP to GND Storage Temperature (TS) ESD Rating(1) -0.3 V to +6 V -65 °C to +150 °C 2 kV Note: 1. Devices are inherently ESD sensitive, handling precautions are required. Human body model rating: 1.5 k in series with 100 pF. Rev. 2.1 May 2012 Rating 8 V to 30 V -40 °C to +85 °C 105 °C/W Note: 2. The value of JA is measured with the device mounted on a 1-in2 FR-4 board with 2 oz. Copper, in a still air environment with TA = 25 °C. The value in any given application depends on the user’s specific board design. www.aosmd.com Page 5 of 16 AOZ1977 Electrical Characteristics TA = 25 °C, VViN = 24 V, unless otherwise specified. Symbol VVIN IVIN_ON VUVLO_RISE Parameter VIN Supply Voltage VVDD Min. Typ. 8 VIN Quiescent Current Not Switching VIN UVLO Threshold VIN Rising VUVLO_FALL VVIN_HYS Conditions VIN Falling 7 6.2 VIN UVLO Hysteresis Max Units 30 V 2 mA 7.3 V 6.5 500 mV VDD Regulation Voltage 8.5 V < VVIN < 30 V 7.5 8 8.5 V Switching Frequency ROSC = 1 MΩ 85 100 115 kHz ROSC = 285 kΩ 298 350 402 kHz 150 200 ns OSCILLATOR FSW Minimum ON Time (PWM) ROSC = 1 MΩ Source Current GATE = 0 V, VDD = 8 V 200 250 mA IGATE_SINK Sink Current GATE = 8 V, VDD = 8 V 400 450 mA TGATE_RISE Rise Time CGATE = 1 nF, VDD = 8 V, 10 % to 90 % of VDD 50 85 ns TGATE_FALL Fall Time CGATE = 1 nF, VDD = 8V, 90 % to 10 % of VDD 25 45 ns TON GATE DRIVER IGATE_SOURCE INPUTS CS Input Current CS = 0.3 V 5 A IISET ISET Input Current ISET = 0.5 V 5 A IILIM ILIM Input Current ILIM = 0.4 V (140 % of CS) 5 A IDBRT DBRT Input Current DBRT = 5 V 5 A IOVP OVP Input Current OVP = 1.2 V 5 A FB Input Current FB = 0.5 V 5 A DBRT Dimming Frequency PWM duty cycle 0.1 % to 99.9 % 2000 Hz ICS IFB FDBRT 100 OUTPUTS IVREF VREF Output Source Current RVREF = 6 kΩ to GND VVREF VREF Reference Voltage RVREF = 6 kΩ to GND VILIM Current Limit Set CS = 0.3 V VOVP OVP Threshold Voltage 200 A 1.188 1.2 1.212 V 120 133 146 % of VCS 1 1.1 PROTECTION 0.9 V OVP Hysteresis 200 mV IAUTO Auto-Restart Charge Current 1.25 A TTHERMAL_SD Thermal Shutdown Threshold 145 °C TTHERMAL_HYS Thermal Shutdown Hysteresis 35 °C VOVP_HYS DPWM DRIVE IDPWM_SOURCE IDPWM_SINK DPWM Source current GATE = 0 V 36 mA DPWM Sink current GATE = 8 V 46 mA 2.0 V LOGIC INPUT VDBRT_HI DBRT Logic High VDBRT_LO DBRT Logic Low Rev. 2.1 May 2012 0.8 www.aosmd.com V Page 6 of 16 AOZ1977 Typical Performance Characteristics Switching Waveforms of Gate, Inductor Current and LX Voltage OUT = 195 V, LED = 200 mA PVIN = 85V PVIN = 110V Gate (10V/div) Gate (10V/div) Inductor Current (0.5A/div) Inductor Current (0.5A/div) LX Voltage (100V/div) LX Voltage (100V/div) 5µs/div 5µs/div PVIN = 130V PVIN = 150V Gate (10V/div) Gate (10V/div) Inductor Current (0.5A/div) Inductor Current (0.5A/div) LX Voltage (100V/div) LX Voltage (100V/div) 5µs/div Rev. 2.1 May 2012 5µs/div www.aosmd.com Page 7 of 16 AOZ1977 PWM Dimming Waveforms for PVIN = 130 V, VOUT = 195 V, ILED = 0.2 A, DBRT = 400 Hz DBRT = 10% DBRT = 50% LED Voltage (50V/div) LED Voltage (50V/div) LED Current (0.2A/div) LED Current (0.2A/div) DBRT (2V/div) DBRT (2V/div) 1ms/div 1ms/div DBRT = 90% Zoomed DBRT = 0.5% LED Voltage (50V/div) LED Voltage (50V/div) LED Current (0.2A/div) LED Current (0.2A/div) DBRT (2V/div) DBRT (2V/div) 2µs/div 1ms/div PVIN = 130 V, VOUT = 195 V, ILED = 0.2 A, DBRT Duty Cycle = 100% LED Voltage (50V/div) LED Current (100mA/div) VDD (5V/div) 20ms/div Rev. 2.1 May 2012 www.aosmd.com Page 8 of 16 AOZ1977 Additional Waveforms Non-latching LED Short Protection, Pin 6 AUTO Connected to 1nF Latching LED Short Protection, Pin 6 AUTO Connected to GND LED Voltage (20V/div) LED Voltage (20V/div) Inductor Current (0.5A/div) Inductor Current (0.5A/div) Feedback Voltage (0.5V/div) Feedback Voltage (0.5V/div) 200µs/div 200µs/div LED Short and Recovery Non-latching OVP Protection LED Voltage (20V/div) Inductor Current (0.5A/div) Inductor Current (0.5A/div) LED Voltage (20V/div) 500µs/div 500ms/div DBRT Control Linearity (PVIN = 130V, VOUT = 195V) Efficiency vs. VIN @ OUT = 195V (LED Current = 200mA, Boost Frequency = 100kHz) 220 98.5 200 Average LED Current (mA) Efficiency (%) 98.0 97.5 97.0 96.5 180 160 140 120 100 96.0 95.0 90 100 110 120 130 140 150 VIN (v) Rev. 2.1 May 2012 80 60 40 DBRT = 100Hz 20 DBRT = 2kHz 0 0 20 40 60 80 100 DBRT Duty Cycle (%) www.aosmd.com Page 9 of 16 AOZ1977 Detailed Description The AOZ1977 is a boost DC/DC controller designed to power a series of LEDs by regulating the current into the LED string. The LED current information is provided to the system through the sense resistor RFB at the bottom of the LED string, between FB pin and GND pin. LED Short Protection Protection Features LED Open Protection Over-Current Protection at Boost Switch When all LEDs are open, the system will respond by boosting the output voltage. Once the output voltage reaches the OVP threshold, OVP protection will trigger. The current limit is a function of RS resistor value at CS pin and the voltage setting at ILIM pin. The voltage at ILIM is directly compared to the sense voltage at CS pin. When CS voltage reaches ILIM set voltage, current limit protection triggers and the boost switch will be turned off immediately until the next clock cycle. To make sure that current limit protection does not affect the normal operation, the current limit should be set at least 30 % higher than the inductor peak current. However, the voltage at ILIM must be less than 0.4 V. When CS voltage is higher than 0.4V, fault detection is active and that may affect normal operation. ILIM voltage is generated by connecting a resistor divider (RL1 and RL2 in the Typical Application diagram on page 1) from 1.2 V VREF pin to ILIM and GND pins. To minimize power consumption, it is recommended that the total resistance for the divider is approximately 20 kΩ. For example, - If peak current is 0.55 A. When FB voltage is higher than 1 V when LED current control switch is ON, the system will consider some LEDs are shorted instantaneously. Under this condition, the controller will enter the fault state. Latch Off or Auto Restart Mode AOZ1977 can select either auto restart mode or latch-off mode under fault condition. Typical fault conditions are excessive current at boost switch, or LED short. For latch-off mode, the AUTO pin can be connected directly to ground. For auto restart mode, the AUTO pin should connect a capacitor to ground. The auto restart period will be determined by the following equation: C  AUTO  T AUTORESTART = --------------------------1.25uA Thermal Protection An internal temperature sensor monitors the junction temperature. It shuts down the internal control circuit and all drivers if the junction temperature exceeds 145 ºC. - 30% higher is 0.72 A. - CS voltage is 0.72 V x 0.55 Ω = 0.4 V. Over-Voltage Protection at Output Over-voltage protection is monitoring the LED output voltage through a resistor divider (Rov1 and Rov2 on page 1) from VOUT to OVP and GND pins. When the voltage at this pin is higher than 1 V, the controller will stop switching immediately until the voltage at this pin is below 0.8 V. Rev. 2.1 May 2012 www.aosmd.com Page 10 of 16 AOZ1977 Application Information Inductor Selection Inductor choice will be affected by many parameters, including duty cycle based on input/output setting, switching frequency, full scale LED current level, and mode of operations. The boost controller can operate under discontinuous mode, continuous mode, or critical conduction mode. For high voltage boost LED driver applications, it is recommended to use critical conduction mode for good stability and best efficiency. ILpeak Inductor Current in Critical Conduction Mode Diode Selection It is recommended to use fast recovery diode for D1. For most applications, Schottky diodes with correct current and voltage ratings are suitable. The diode current rating should be at least higher than the full scale LED current. The diode voltage rating should be higher than the OVP level of VOUT voltage. Output Capacitors The amount and type of capacitor used is mainly determined by the design output ripple requirement, and mainly by the output ripple current which is usually higher for boost converters and equals: In critical conduction mode: ILpeak = di = 2  Iin The duty cycle for the boost DC/DC system is defined as: Vout – Vin DutyCycle = D = ---------------------------V OUT To determine the ON time for the boost switch: D ONtime = dt = ----------Fsw For the application with VIN = 130 V, VOUT = 180 V, LED current = 200mA: 180V  0.2A lin = --------------------------------- = 0.277A 130V Vout – Vin Iripple = --------------------------------Vin When selecting output capacitors, it is more important to check the effective ESR of the capacitor than the actual capacitance value. For example, a 10 F capacitor with 0.02 Ω ESR will handle higher ripple current but produce less output ripple than a 33 F capacitor with 0.04 Ω ESR. It is recommended to use low ESR MLCC ceramic capacitors. For high voltage cost effective application, multiple Electrolytic capacitors in parallel will reduce the total effective ESR. Input Capacitors The input capacitors for boost converters do not require low ESR due to the fact that the input current is continuous. Also, they do not contain large peak current as compared to the output capacitors. di = 2  0.277A = 0.555A 180V – 130V D = ---------------------------------- = 0.28 180V The ripple current at the input capacitor is: 0.28 dt = --------------------- = 2.8us 100kHz 0.3  Vin   Vout – Vin  Iin_ripple = --------------------------------------------------------------Fsw  L  Vout where Fsw is the switching frequency, 100 kHz in this example. The inductor value is determined by: 2.8us  130V dt  Vin L = --------------------- = ------------------------------------ = 656uH 0.555A di After the inductor value is calculated, we need to consider the DCR resistance and the Isat saturation current of the inductor. Inductor DCR is inversely Rev. 2.1 May 2012 proportional to the Isat. It is recommended to select an inductor for which the Isat value should be at least 50 % higher than the ILpeak value. To minimize the EMI effect, it is always preferable to use shielded type inductors. Electrolytic capacitors should work well with the appropriate voltage and ripple current rating, it is not recommended to use Tantalum capacitors because Boost converters do exhibit high surge currents during startup which can cause tantalum capacitors to fail. www.aosmd.com Page 11 of 16 AOZ1977 Current Sense Resistors There are two current sense resistors in this application, an LED current sense resistor RFB and a Boost switch current sense resistor RS. RFB LED current sense resistor is set by: ISET Voltage 0.5V RFB = ------------------------------------ = ------------ = 2.5 LED Current 0.2A LED current is a function of ISET voltage and RFB resistance. ISET voltage is generated by connecting a resistor divider (Rr1 and Rr2 on page 1) from 1.2 V VREF pin to ISET and GND pins. To minimize power consumption, it is recommended that the total resistance for the divider is approximately 20 kΩ. RS boost switch current sense resistor is set by: 0.3V 0.3V RS = -------------------------------------------------------------------------- = ---------------- = 0.55 0.55A LEDInductor Peak Current For typical application, it is recommend to set the voltage at CS to approximately 0.3 V when inductor current reaches the peak. Boost Feedback Loop Compensation The AOZ1977 employs peak current mode control for easy use and fast transient response. Peak current mode control eliminates the double pole effect of the output L&C filter. It greatly simplifies the compensation loop design. With peak current mode control, the boost power stage can be simplified to be a one-pole, one left plane zero and one right half plane (RHP) system in frequency domain. The pole is the dominant pole and can be calculated by: 1 f P1 = ----------------------------------2  C O  R L The zero is a ESR zero due to the output capacitor and its ESR. It is can be calculated by: 1 f Z1 = -----------------------------------------------2  C O  ESR CO The RHP zero has the effect of a zero in the gain causing an imposed +20 dB/decade on the roll off, but has the effect of a pole in the phase, subtracting 90o in the phase. The RHP zero can be calculated by: V IN2 -----------------------------------------f Z2 = 2  L  I O  V O The RHP zero obviously can cause the instable issue if the bandwidth is higher. It is recommended to design the bandwidth to lower than the one half frequency of RHP zero. The compensation design is actually to shape the converter close loop transfer function to get desired gain and phase. Several different types of compensation network can be used for AOZ1977. For most cases, a series capacitor and resistor network connected to the COMP pin sets the pole-zero and is adequate for a stable high-bandwidth control loop. In the AOZ1977, FB pin and COMP pin are the inverting input and the output of internal transconductance error amplifier. A series R and C compensation network connected to COMP provides one pole and one zero. The pole is: G EA f P2 = ------------------------------------------2  C C  G VEA where; GEA is the error amplifier transconductance, which is 200 x 10-6 A/V, GVEA is the error amplifier voltage gain, which is 1000 V/V, and CC is the compensation capacitor. The zero given by the external compensation network, capacitor CC and resistor RC is located at: 1 f Z2 = ----------------------------------2  C C  R C Choosing the suitable CC and RC by trading-off stability and bandwidth. where; CO is the output filter capacitor, RL is load resistor value, and ESRCO is the equivalent series resistance of output capacitor. Rev. 2.1 May 2012 www.aosmd.com Page 12 of 16 AOZ1977 PCB Layout Consideration Correct layout practices are essential for a working design that will meet expectations. It is recommended to use a two-layer board for the design. However, a single layer board would be sufficient if basic layout rules are followed. In any SMPS layout, external components should be grouped into Power or IC control. From typical application circuit, there are two GND symbols. The striped one is for Power GND and the solid one is for Signal/Control GND. Both symbols are connected to a single point connection on the layout, All Power connections should be as short and wide as possible in order to reduce undesired parasitic inductance. The output capacitors should be physically placed in the current path between the SMPS and the load. Input capacitors should be placed as close as possible to the input side of the inductor. To prevent interference and system noise, it is critical that the switch node connection for boost switch, inductor, and output diode must be as short and close as possible. A GND copper layer covers the top layer to help shield the noise. For two-layer board, it is essential that the GND plane under this switching node should be filled and uninterrupted. PWR GND Connect PWR GND and SGNL GND at 1 point S SGNL GND Single Point Connection Connecting PWR GND and Signal GND Rev. 2.1 May 2012 www.aosmd.com Page 13 of 16 AOZ1977 Package Dimensions, SOIC, 16L Gauge Plane 0.25 C 16 L E1 1 2 E 3 q D A2 A .004"(0.10mm) Seating Plane e A1 b Dimensions in millimeters RECOMMENDED LAND PATTERN 2.2 5.74 2.87 1.27 Symbols A A1 Min. 1.35 0.10 A2 b C D E1 e E L θ — 0.33 0.19 9.80 3.80 Nom. 1.60 — 1.45 — — — 3.90 1.27 TYP 5.80 6.00 0.40 — 0° — Dimensions in inches Max. 1.75 0.25 Symbols A A1 Min. 0.053 0.004 — 0.51 0.25 10.00 4.00 A2 b C D E1 e E L θ — 0.013 0.007 0.386 0.150 6.20 1.27 8° Nom. 0.063 — Max. 0.069 0.010 0.057 — — 0.020 — 0.010 — 0.394 0.154 0.157 0.050 TYP 0.228 0.236 0.244 0.016 — 0.050 0° — 8° 0.8 0.63 UNIT: mm Notes: 1. All dimensions are in millimeters. 2. Dimensions are inclusive of plating 3. Package body sizes exclude mold flash and gate burrs. Mold flash at the non-lead sides should be less than 6 mils. 2. Dimension L is measured in gauge plane. 3. Tolerance is 0.10mm unless otherwise specified. 4. Controlling dimension is millimeter, converted inch dimensions are not necessarily exact. Rev. 2.1 May 2012 www.aosmd.com Page 14 of 16 AOZ1977 Tape and Reel Dimensions, SOIC, 16L Carrier Tape P0 K0 D0 A P2 T E1 E2 CL B1 B0 E B2 K1 A1 P1 SECTION A--A A D1 A0 FEEDING DIRECTION UNIT: MM Package A0 B0 K0 SO16 (16 mm) 6.50 ±0.1 10.30 ±0.1 2.30 ±0.1 D0 K1 1.80 1.55 ±0.1 ±0.05 D1 E E1 E2 P0 P1 P2 T B1 B2 A1 1.6 ±0.1 16.00 ±0.3 1.75 ±0.1 7.50 ±0.1 4.0 ±0.1 8.00 ±0.1 2.0 ±0.1 0.3 ±0.05 REF. 6.6 REF. 1.5 REF. 3.5 Reel W3 (Include flange distortion at outer edge) W1 (Measured at Hub) S K M N (Hub Dia.) H W2 (Measured at Hub) T UNIT: MM Tape Size M N T W1 W2 W3 S K H 16mm Ø332 MAX. Ø100.0 ±2.0 2.0 ±0.5 16.4 22.4 MAX. 15.9~19.4 2.2 TYP. 10.1 MIN. Ø13.0 ±0.2 +2.0 -0 Leader/Trailer and Orientation Trailer Tape 300mm min. Rev. 2.1 May 2012 Components Tape Orientation in Pocket www.aosmd.com Leader Tape 500mm min. Page 15 of 16 AOZ1977 Part Marking AOZ1977AI (SOIC-16) Z1977AI FAYWLT Part Number Code Assembly Lot Code Fab & Assembly Location Year & Week Code This datasheet 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. 2.1 May 2012 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 16 of 16