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| 19-4418; Rev 0; 4/09 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP General Description The MAX8884Y/MAX8884Z step-down converters with dual low-dropout (LDO) linear regulators are intended to power low-voltage microprocessors, DSPs, camera and Wi-Fi modules, or other point of load applications in portable devices. These ICs feature high efficiency with small external component size. The step-down converter output voltage is pin selectable between 1.2V and 1.8V, and provides guaranteed output current of 700mA. The 2/4MHz hysteretic-PWM control scheme allows for tiny external components and reduces no-load operating current to 50A. Two low quiescent current, low-noise LDOs operate down to 2.7V supply voltage. Two switching frequency options are available--MAX8884Y (2MHz) and MAX8884Z (4MHz)--allowing optimization for smallest solution size or highest efficiency. Fast switching allows the use of small ceramic 2.2F input and output capacitors while maintaining low ripple voltage. The MAX8884Y/MAX8884Z have individual enables for each output, maximizing flexibility. The MAX8884Y/MAX8884Z are available in a 16-bump, 2mm x 2mm CSP package (0.7mm max height). Features Step-Down Converter Pin-Selectable Output Voltage (1.2V/1.8V) 2MHz or 4MHz Switching Frequency Low-Output Voltage Ripple 700mA Output Drive Capability Simple Logic ON/OFF Control Tiny External Components Low-Noise LDOs 2 x 300mA LDO Pin-Selectable Output Voltage (LDO1) Low 26VRMS (typ) Output Noise High 65dB (typ) PSRR Simple Logic ON/OFF Control Low 0.1A Shutdown Current 2.7V to 5.5V Supply Voltage Range Thermal Shutdown Tiny, 2mm x 2mm x 0.65mm CSP Package (4x4 Grid) MAX8884Y/MAX8884Z Ordering Information PART MAX8884YEREKE+T MAX8884ZEREKE+T PIN-PACKAGE 16 CSP 16 CSP SWITCHING FREQUENCY 2MHz 4MHz Applications Cell Phones/Smartphones PDA and Palmtop Computers Portable MP3 and DVD Players Digital Cameras, Camcorders PCMCIA Cards Handheld Instruments Note: All devices are specified over the -40C to +85C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Typical Application Circuit appears at end of data sheet. Pin Configuration TOP VIEW (BUMPS ON BOTTOM) Typical Operating Circuit BATT 2.7V TO 5.5V IN1A 2.2F IN1B LX 2.2H 2.2F FB BUCK 1.2V/1.8V MAX8884Y MAX8884Z A1 REFBP B1 LDO2 A2 AGND B2 BUCK_EN C2 SEL D2 LDO1_EN A3 NC1 B3 LDO2_EN C3 IN1B D3 NC2 A4 PGND B4 LX C4 IN1A D4 FB BUCK ON/OFF BUCK_EN MAX8884Y MAX8884Z PGND REFBP BUCK/LDO1 VOLTAGE SELECTION LDO1 ON/OFF LDO2 ON/OFF BATT 2.7V TO 5.5V SEL LDO1_EN LDO2_EN AGND C1 LDO1 VLDO1 UP TO 300mA IN2 D1 IN2 LDO2 VLDO2 UP TO 300mA LDO1 CSP ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z ABSOLUTE MAXIMUM RATINGS IN1A, IN1B, IN2, REFBP to AGND ........................-0.3V to +6.0V FB to PGND ...........................................................-0.3V to +6.0V SEL, BUCK_EN to AGND...............-0.3V to (VIN1A/VIN1B + 0.3V) LDO1, LDO2, LDO1_EN, LDO2_EN to AGND.................................................-0.3V to (VIN2 + 0.3V) IN2 to IN1A, IN1B ..................................................-0.3V to +0.3V AGND to PGND .....................................................-0.3V to +0.3V IN1A, IN1B, LX Current .....................................................1ARMS Continuous Power Dissipation (TA = +70C) 16-Bump CSP (derate 12.5mW/C above +70C) ..............1W Operating Temperature .......................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Bump Temperature*.........................................................+260C *These ICs are constructed using a unique set of packaging techniques imposing a limit on the thermal profile used during board level solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow. Preheating is required. Hand or wave soldering is not allowed. Stresses beyond those listed under "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 for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN1A = VIN1B = VIN2 = VLDO1_EN = VLDO2_EN = VBUCK_EN = 3.6V. TA = -40C to +85C, typical values are at TA = +25C, unless otherwise noted.) (Note 1) PARAMETER INPUT SUPPLY Input Voltage Input Undervoltage Threshold Shutdown Supply Current No-Load Supply Current THERMAL PROTECTION Thermal Shutdown LOGIC CONTROL Logic Input-High Voltage (BUCK_EN, SEL, LDO1_EN, LDO2_EN) Logic Input-Low Voltage (BUCK_EN, SEL, LDO1_EN, LDO2_EN) Logic Input Current (BUCK_EN, SEL, LDO1_EN, LDO2_EN) FB Buck Converter Output Voltage FB Leakage Current LX On-Resistance p-channel MOSFET switch, ILX = -40mA n-channel MOSFET rectifier, ILX = 40mA 0.18 0.15 0.30 0.25 SEL = AGND, IBUCK = 0A VSEL = VIN1A, IBUCK = 0A VIN1A = VIN1B = VIN2 = 5.5V, VFB = 0 TA = +25C TA = +85C 1.18 1.78 1.22 1.80 0.01 1 1.24 1.85 1 V V A 2.7V VIN1A = VIN1B = VIN2 5.5V 1.3 V TA rising, 20C typical hysteresis +160 C VIN1A, VIN1B, VIN2 VIN1A, VIN1B, VIN2 rising, 180mV typical hysteresis VBUCK_EN = VLDO1_EN = VLDO2_EN = 0 TA = +25C TA = +85C 2.7 2.52 2.63 0.1 0.1 140 50 230 80 5.5 2.70 4 V V A A A CONDITIONS MIN TYP MAX UNITS VBUCK_EN = 0, ILDO1 = ILDO2 = 0A VLDO1_EN = VLDO2_EN = 0, IBUCK = 0A, no switching 2.7V VIN1A = VIN1B = VIN2 5.5V TA = +25C TA = +85C 0.01 0.1 0.4 1 V VIL = 0 or VIH = VIN1A = 5.5V A 2 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP ELECTRICAL CHARACTERISTICS (continued) (VIN1A = VIN1B = VIN2 = VLDO1_EN = VLDO2_EN = VBUCK_EN = 3.6V. TA = -40C to +85C, typical values are at TA = +25C, unless otherwise noted.) (Note 1) PARAMETER LX Leakage Current CONDITIONS VIN1A = VIN1B = VIN2 = 5.5V, VLX = 0 TA = +25C TA = +85C 0.8 0.6 MAX8884Y_ MAX8884Z_ MIN TYP 0.1 1 1.0 0.8 40 60 0.07 0.06 From VBUCK_EN rising to VLX rising VIN2 = 5.5V, ILDO_ = 1mA; VIN2 = 3.4V, ILDO_ = 100mA VIN2 = 5.5V, ILDO_ = 1mA; VIN2 = 3.4V, ILDO_ = 100mA VLDO_ = 0 ILDO_ = 100mA, TA = +25C (VLDO_ ILDO_ stepped from 50A to 200mA 10Hz to 100kHz, VLDO_ = 1.8V, CLDO_ = 2.2F, ILDO_ = 30mA 10Hz to 100kHz, VLDO_ = 1.8V, CLDO_ = 2.2F, ILDO_ = 30mA 0 < ILDO_ < 10mA 10mA < ILDO_ < 200mA 200mA < ILDO_ < 300mA VLDO1_EN = VLDO2_EN = 0 From VLDO_EN rising to VLDO_ output rising 0 IREFBP 1A 1.237 2.5V) VIN2 stepped from 3.5V to 5.5V, ILDO_ = 100mA SEL = AGND SEL = IN1_ 2.770 300 310 450 70 2.4 25 65 26 0.1 1 2.2 100 150 1.250 0.2 250 1.263 5 s V mV F 750 200 1.764 120 1.800 2.800 2.800 2.830 250 1.836 1.2 1.0 MAX 1 UNITS A A A mA s s s MAX8884Y/MAX8884Z p-Channel MOSFET Peak Current VLX = 0 Limit n-Channel MOSFET Valley Current Limit n-Channel MOSFET Zero-Crossing Threshold Minimum On-Time Minimum Off-Time Power-Up Delay LDO1, LDO2 Output Voltage VLDO1 Output Voltage VLDO2 Output Current Current Limit Dropout Voltage Line Regulation Load Regulation Power-Supply Rejection VLDO_/ VIN2 Output Noise Output Capacitor for Stable Operation Shutdown Output Impedance Power-Up Delay REFBP REFBP Output Voltage REFBP Supply Rejection VIN2 stepped from 2.55V to 5.5V V V mA mA mV mV mV dB VRMS Note 1: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design. _______________________________________________________________________________________ 3 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Typical Operating Characteristics (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25C, unless otherwise noted.) STEP-DOWN CONVERTER EFFICIENCY vs. LOAD CURRENT, VOUT = 1.8V MAX8884Y/Z toc01 STEP-DOWN CONVERTER EFFICIENCY vs. LOAD CURRENT, VOUT = 1.2V MAX8884Y/Z toc02 STEP-DOWN CONVERTER NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE VBUCK_EN = VIN VLDO1_EN = VLDO2_EN = 0 MAX8884Y/Z toc03 100 90 80 EFFICIENCY (%) 100 90 80 EFFICIENCY (%) 300 250 SUPPLY CURRENT (A) 200 VIN FALLING 150 100 50 MAX8884Z 0 VIN RISING MAX8884Y 70 60 50 40 30 1 10 MAX8884Y, VIN = 3.2V = 3.6V = 4.2V MAX8884Z, VIN = 3.2V = 3.6V = 4.2V 70 60 50 40 30 MAX8884Y, VIN = 3.2V = 3.6V = 4.2V MAX8884Z, VIN = 3.2V = 3.6V = 4.2V 100 1000 1 10 100 1000 0 1 2 3 4 5 6 LOAD CURRENT (mA) LOAD CURRENT (mA) INPUT VOLTAGE (V) STEP-DOWN OUTPUT VOLTAGE vs. LOAD CURRENT (VOLTAGE POSITIONING) 1.8 1.7 OUTPUT VOLTAGE (V) 1.6 1.5 1.4 1.3 1.2 1.1 1.0 1 10 100 1000 SEL = AGND VLX ILX SEL = IN1_ MAX8884Y/Z toc04 MAX8884Z STEP-DOWN CONVERTER LIGHT LOAD SWITCHING WAVEFORMS MAX8884Y/Z toc05 MAX8884Y STEP-DOWN CONVERTER LIGHT LOAD SWITCHING WAVEFORMS MAX8884Y/Z toc06 1.9 VOUT AC-COUPLED VOUT 20mV/div AC-COUPLED 10mV/div 100mA/div 0A 100mA/div 0A ILX 2V/div 0V VLX ILOAD = 50mA 2V/div 0V 400ns/div 1s/div LOAD CURRENT (mA) MAX8884Z STEP-DOWN CONVERTER HEAVY LOAD SWITCHING WAVEFORMS MAX8884Y/Z toc07 MAX8884Y STEP-DOWN CONVERTER HEAVY LOAD SWITCHING WAVEFORMS MAX8884Y/Z toc08 VOUT ILX AC-COUPLED 10mV/div 500mA/div 0A VOUT AC-COUPLED 10mV/div 500mA/div 0A ILX VLX ILOAD = 500mA 200ns/div 2V/div 0V VLX ILOAD = 500mA 400ns/div 2V/div 0V 4 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25C, unless otherwise noted.) MAX8884Z STEP-DOWN CONVERTER SOFT-START WAVEFORMS MAX8884Y/Z toc09 MAX8884Y/MAX8884Z MAX8884Y STEP-DOWN CONVERTER SOFT-START WAVEFORMS MAX8884Y/Z toc10 VOUT 1V/div 0V VOUT 1V/div 0V IIN1 200mA/div 0A IIN1 200mA/div 0A ILX 500mA/div 0A ILX 500mA/div 0A VBUCK_EN 40s/div 2V/div ILOAD = 500mA 0V VBUCK_EN 40s/div 2V/div ILOAD = 500mA 0V MAX8884Y STEP-DOWN CONVERTER LINE TRANSIENT RESPONSE MAX8884Y/Z toc11 MAX8884Z STEP-DOWN CONVERTER LINE TRANSIENT RESPONSE MAX8884Y/Z toc12 4V VIN 3.5V VOUT 4V 1V/div VIN 4V 4V 1V/div 3.5V AC-COUPLED 20mV/div VOUT AC-COUPLED 20mV/div ILX 200mA/div ILX 200mA/div ILOAD = 500mA 10s/div 0A 10s/div ILOAD = 500mA 0A MAX8884Z STEP-DOWN CONVERTER LOAD TRANSIENT MAX8884Y/Z toc13 MAX8884Y STEP-DOWN CONVERTER LOAD TRANSIENT MAX8884Y/Z toc14 VOUT 1.8V DC OFFSET 100mV/div VOUT 1.8V DC OFFSET 100mV/div ILX 500mA/div 0A ILX 500mA/div 0A 500mA/div 500mA 0A 10mA 10mA 20s/div 500mA 500mA/div IOUT 10mA 20s/div 10mA 0A IOUT _______________________________________________________________________________________ 5 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25C, unless otherwise noted.) MAX8884Y STEP-DOWN CONVERTER SHUTDOWN WAVEFORMS MAX8884Y/Z toc15 LDO1, LDO2 INPUT SUPPLY CURRENT vs. INPUT VOLTAGE VLDO1_EN = VLDO2_EN = VIN, VBUCK_EN = 0 MAX8884Y/Z toc16 350 1V/div SUPPLY CURRENT (A) 0V 300 250 200 150 100 50 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) VOUT ILX 500mA/div 0A VBUCK_EN 10s/div ILOAD = 500mA 5V/div 0V LDO2 DROPOUT VOLTAGE vs. LOAD CURRENT MAX8884Y/Z toc17 LDO POWER SUPPLY RIPPLE REJECTION, VOUT = 1.8V 70 RIPPLE REJECTION (dB) 60 50 40 30 20 10 ILDO = 30mA MAX8884Y/Z toc18 250 80 200 DROPOUT VOLTAGE (V) 150 100 50 0 0 50 100 150 200 250 300 LOAD CURRENT (mA) 0 0.01 0.1 1 10 100 1000 FREQUENCY (kHz) LDO POWER SUPPLY RIPPLE REJECTION, VOUT = 2.8V MAX8884Y/Z toc19 LDO OUTPUT VOLTAGE NOISE WAVEFORM, VOUT_ = 1.8V MAX8884Y/Z toc20 70 60 RIPPLE REJECTION (dB) 50 40 30 20 10 ILDO_ = 30mA 0 0.01 0.1 1 10 100 MAX8884Y/MAX8884Z LDO1 = 1.8 AT 30mA VIN = 3.6V 50V/div VN = 26.1VRMS, f = 100Hz to 100kHz, ILDO_ = 30mA 1000 400s/div FREQUENCY (kHz) 6 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25C, unless otherwise noted.) LDO OUTPUT-NOISE SPECTRAL DENSITY vs. FREQUENCY, VLDO_ = 1.8V MAX884Y/Z toc21 MAX8884Y/MAX8884Z LDO OUTPUT-NOISE SPECTRAL DENSITY vs. FREQUENCY, VLDO_ = 2.8V MAX884Y/Z toc22 10,000 10,000 NOISE DENSITY (nV(Hz)) NOISE DENSITY (nV(Hz)) 1000 1000 100 100 ILDO_ = 30mA 10 0.01 0.1 1 10 100 1000 FREQUENCY (kHz) 10 ILDO_ = 30mA 0.01 0.1 1 10 100 1000 FREQUENCY (kHz) LDO1, LDO2 LINE TRANSIENT MAX8884Y/Z toc23 LDO1, LDO2 LOAD TRANSIENT RESPONSE MAX8884Y/Z toc24 4V VIN 3.5V VLDO1 4V 1V/div ILDO2 1mA VLDO2 AC-COUPLED 5mV/div ILDO1 40mA 1mA 50mA/div AC-COUPLED 10mV/div 40mA 1mA 1mA VLDO2 AC-COUPLED 5mV/div VLDO1 ILDO1 = ILDO2 = 100mA 10s/div 50mA/div AC-COUPLED 10mV/div 20s/div _______________________________________________________________________________________ 7 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25C, unless otherwise noted.) LDO1, LDO2 LOAD TRANSIENT RESPONSE NEAR DROPOUT MAX8884Y/Z toc25 LDO1, LDO2 STARTUP AND SHUTDOWN RESPONSE MAX8884Y/Z toc26 ILDO2 1mA VLDO2 40mA 1mA 50mA/div VLDO1_EN = VLDO2_EN 2V/div 0V AC-COUPLED 10mV/div ILDO1 1mA VLDO1 40mA 1mA 50mA/div VLDO1 2V/div 0V AC-COUPLED 10mV/div VIN2 = VLDO2 + 200mV 20s/div VLDO2 2V/div 0V 400s/div REFBP SOFT-START CREFBP = 0.033F MAX8884Y/Z toc27 REFBP SOFT-START CREFBP = 0.15F MAX8884Y/Z toc28 1V/div VREFBP 0V VLDO1_EN 2V/div 0V VREFBP 1V/div 0V VLDO1_EN 2V/div 0V VLDO1 1V/div 0V VLDO1 1V/div 0V 100s/div 100s/div 8 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Pin Description PIN A1 A2 A3 A4 NAME REFBP AGND NC1 PGND FUNCTION Reference Noise Bypass. Bypass REFBP to AGND with a 0.033F ceramic capacitor to reduce noise on the LDO outputs. REFBP is internally pulled to ground through a 1k resistor during shutdown. Low-Noise Analog Ground. Connect to common ground plane. No Internal Connection. Connect NC1 to ground. Power Ground for Step-Down Converter. Connect to common ground plane. 300mA LDO Regulator 2 Output. For 300mA application, bypass LDO2 with a 2.2F ceramic capacitor as close as possible to LDO2 and AGND. For low-output current capability, up to 10mA, an output capacitor of 0.1F is sufficient to keep the output voltage stable. LDO2 is internally pulled to ground through a 100 resistor when this regulator is disabled. Step-Down Converter Enable Input. Connect BUCK_EN to IN1_ or logic-high for normal operation. Connect BUCK_EN to AGND or logic-low for step-down shutdown mode. LDO2 Enable Input. Connect LDO2_EN to IN2 or logic-high for normal operation. Connect LDO2_EN to AGND or logic-low for LDO2 shutdown mode. Inductor Connection. Connect an inductor from LX to the output of the step-down converter. Supply Voltage Input for LDO1, LDO2, and Internal Reference. Connect IN2 to a battery or supply voltage from 2.7V to 5.5V. Bypass IN2 with a 4.7F ceramic capacitor as close as possible to IN2 and AGND. Connect IN2 to the same source as IN1A and IN1B. Output Voltage Selection for LDO1 and Step-Down Converter. Connect to IN1_ or AGND for output voltage selection. See Table 1. Supply Voltage Input for Step-Down Converter. Connect IN1B and IN1A to a battery or supply voltage from 2.7V to 5.5V. Bypass the connection of IN1B and IN1A with a 2.2F ceramic capacitor as close as possible to IN1B, IN1A, and PGND. IN1A and IN1B are internally connected together. Connect IN1A and IN1B to the same source as IN2. 300mA LDO Regulator 1 Output. For 300mA application, bypass LDO1 with a 2.2F ceramic capacitor as close as possible to LDO1 and AGND. For low-output current capability, up to 10mA, an output capacitor of 0.1F is sufficient to keep output voltage stable. LDO1 is internally pulled to AGND through a 100 resistor when this regulator is disabled. LDO1 Enable Input. Connect LDO1_EN to IN2 or logic-high for normal operation. Connect LDO1_EN to AGND or logic-low for LDO1 shutdown mode. No Internal Connection. Connect NC2 to ground. FB is Connected to the Internal Feedback Network MAX8884Y/MAX8884Z B1 LDO2 B2 B3 B4 C1 BUCK_EN LDO2_EN LX IN2 C2 SEL C3, C4 IN1B, IN1A D1 LDO1 D2 D3 D4 LDO1_EN NC2 FB Detailed Description The MAX8884Y/MAX8884Z are designed to power the subcircuits within a system. These ICs contain a highfrequency, high-efficiency step-down converter and two LDOs. The step-down converter delivers 700mA with either 1.2V or 1.8V selectable output voltage using SEL. The hysteretic PWM control scheme provides extremely fast transient response, while 2MHz and 4MHz switching frequency options allow the trade-off between efficiency and the smallest external components. The MAX8884Y/MAX8884Z linear regulators can be used to power loads requiring a low output noise supply. Step-Down Converter Control Scheme A hysteretic PWM control scheme ensures high efficiency, fast switching, fast transient response, low-output voltage ripple, and physically tiny external components. The control scheme is simple: when the output voltage is below the regulation threshold, the error comparator begins a switching cycle by turning on the high-side switch. This high-side switch remains on until the minimum on-time expires and output voltage is within regulation, or the inductor current is above the current-limit threshold. Once off, the high-side switch remains off until the minimum off-time expires and the output voltage falls again below the regulation threshold. During 9 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z the off period, the low-side synchronous rectifier turns on and remains on until the high-side switch turns on again. The internal synchronous rectifier eliminates the need for an external Schottky diode. At inductor currents below 40mA (60mA), the MAX8884Y (MAX8884Z) automatically switches to pulse-skipping mode to improve light-load efficiency. Output voltage ripple remains low at all loads, while the skip-mode switching frequency remains ultrasonic down to 1mA (typ) loads. Table 1. SEL Output Voltage Selection SEL AGND IN1_ BUCK CONVERTER OUTPUT VOLTAGE (V) 1.2 1.8 LDO1 OUTPUT VOLTAGE (V) 1.8 2.8 Step-Down Converter Soft-Start The MAX8884Y/MAX8884Z step-down converter uses internal soft-start circuitry to limit inrush current at startup, reducing transients on the input source. Soft-start is particularly useful for supplies with high output impedance such as Li+ and alkaline cells. See the soft-start waveforms in the Typical Operating Characteristics. Voltage Positioning Load Regulation The MAX8884Y/MAX8884Z step-down converters utilize a unique feedback network. By taking a DC feedback from the LX node through R1 in the Block Diagram, the usual phase lag due to the output capacitor is removed, making the loop exceedingly stable and allowing the use of very small ceramic output capacitors. To improve the load regulation, resistor R3 is included in the feedback (see the Block Diagram). This configuration yields load regulation equal to half the inductor's series resistance multiplied by the load current. This voltage positioning load regulation greatly reduces overshoot during load transients. I x RDCR VBUCK = VBUCK _ NO _ LOAD - LOAD 2 ILOAD = load current RDCR = DC impedance of inductor VBUCK _ NO _ LOAD = 1.2V or 1.8V depending on SEL Thermal Shutdown Thermal shutdown limits total power dissipation in the MAX8884Y/MAX8884Z. If the junction temperature exceeds +160C, thermal shutdown circuitry turns off the MAX8884Y/MAX8884Z, allowing the ICs to cool. The ICs turn on and begin soft-start after the junction temperature cools by 20C. This results in a pulsed output during continuous thermal-overload conditions. Applications Information Output Voltages The MAX8884Y/MAX8884Z DC-DC step-down converter sets the BUCK and LDO1 output voltage based on the state of SEL. See Table 1. Contact the factory for other output voltage options. SEL Output Voltage Selection SEL is used to determine the output voltage of the buck converter and LDO1. See Table 1. LDO Dropout Voltage The regulator's minimum input/output differential (or dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this determines the useful end-of-life battery voltage. Because the MAX8884Y/MAX8884Z LDOs use a p-channel MOSFET pass transistor, their dropout voltages are a function of drain-to-source on-resistance (RDS(ON)) multiplied by the load current (see the Typical Operating Characteristics). Shutdown Mode Drive BUCK_EN to logic-low to place the MAX8884Y/ MAX8884Z step-down converter in shutdown mode. In shutdown, the control circuitry, internal switching MOSFET, and synchronous rectifier turn off and LX becomes high impedance. The LDOs are individually enabled. Connect LDO1_EN and LDO2_EN to GND or logic-low to place LDO1 and LDO2 in shutdown mode. In shutdown, the outputs of the LDOs are pulled to ground through an internal 100 resistor. When the step-down converter and all LDOs are in shutdown, the MAX8884Y/MAX8884Z enter a very low-power state, where the input current drops to 0.1A (typ). Inductor Selection The MAX8884Y operates with a switching frequency of 2MHz and utilizes a 2.2H inductor. The MAX8884Z operates with a switching frequency of 4MHz and utilizes a 1H inductor. The higher switching frequency of the MAX8884Z allows the use of physically smaller inductors at the cost of lower efficiency. The lower switching frequency of the MAX8884Y results in greater efficiency at the cost of a physically larger inductor. See the Typical Operating Characteristics for efficiency graphs for both the MAX8884Y and the MAX8884Z. 10 ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP The inductor's DC current rating only needs to match the maximum load of the application because the MAX8884Y/MAX8884Z feature zero current overshoot during startup and load transients. For optimum transient response and high efficiency, choose an inductor with DC series resistance in the 50m to 150m range. See Table 2 for suggested inductors and manufacturers. LDO2. Larger input capacitor values and lower ESR provide better noise rejection and line transient response. Note that some ceramic dielectrics exhibit large capacitance and ESR variation with temperature. With dielectrics such as Z5U and Y5V, it may be necessary to use two times the sum of the output capacitor value of LDO1 and LDO2 (or larger) to ensure stability at temperatures below -10C. With X7R or X5R dielectrics, a capacitance equal to the sum is sufficient at all operating temperatures. MAX8884Y/MAX8884Z Output Capacitor Selection For the DC-DC step-down converter, the output capacitor CBUCK is required to keep the output voltage ripple small and ensure regulation loop stability. CBUCK must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectric are highly recommended due to their small size, low ESR, and small temperature coefficients. Due to the unique feedback network, the output capacitance can be very low. A 2.2F ceramic capacitor is recommended for most applications. For optimum load-transient performance and very low output ripple, the output capacitor value can be increased. For LDO1 and LDO2, the minimum output capacitance required is dependent on the load currents. For loads lighter than 10mA, it is sufficient to use a 0.1F ceramic capacitor for stable operation over the full temperature range. For loads up to 200mA, an output capacitor of 1F is sufficient for stable operation over the entire temperature range. Operating the LDO at maximum rated current the LDO1 and LDO2 requires a 2.2F ceramic capacitor. Using larger output capacitors reduces output noise and improves load-transient response, stability, and power-supply rejection. Note that some ceramic dielectrics exhibit large capacitance and ESR variation with temperature. With dielectrics such as Z5U and Y5V, it is necessary to use 4.7F or more to ensure stability at temperatures below -10C. With X7R or X5R dielectrics, 2.2F is sufficient at all operating temperatures. These regulators are optimized for ceramic capacitors. Tantalum capacitors are not recommended. Reference Noise Bypass Capacitor Selection The REFBP capacitor reduces the output noise of LDO1 and LDO2. A value of 0.033F is sufficient for most applications. This value can be increased up to 0.150F with some effect on the soft-start time of the LDOs. See the Typical Operating Characteristics for more information. Do not use values greater than 0.150F as this degrades the performance of the internal reference voltage and has a corresponding impact on all output voltages. Ceramic capacitors with X5R or X7R dielectric are highly recommended due to their small size, low ESR, and small temperature coefficients. Note that some ceramic dielectrics exhibit large capacitance and ESR variation with temperature. With dielectrics such as Z5U and Y5V, it may be necessary to use two times the recommended value to achieve desired output noise performance at temperatures below -10C. Tantalum capacitors are not recommended. Thermal Considerations In most applications, the MAX8884Y/MAX8884Z do not dissipate much heat due to their high efficiency. But in applications where the MAX8884Y/MAX8884Z run at high ambient temperature with heavy loads, the heat dissipated may exceed the maximum junction temperature of the part. If the junction temperature reaches approximately +160C, all power switches are turned off and LX and FB become high impedance, and LDO1 and LDO2 are pulled down to ground through an internal 100 resistor. The MAX8884Y/MAX8884Z maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature difference between the die junction and ambient air, and the rate of airflow. The power dissipated in the device, PDISS, is: 1 PDISS = PBUCK - 1 + ILDO1(VIN2 - VLDO1) + ILDO2 (VIN2 - VLDO2 ) BUCK Input Capacitor Selection The input capacitor (CIN1) of the DC-DC step-down converter reduces the current peaks drawn from the battery or input power source and reduces switching noise in the MAX8884Y/MAX8884Z. The impedance of CIN1 at the switching frequency should be kept very low. Ceramic capacitors with X5R or X7R dielectric are highly recommended due to their small size, low ESR, and small temperature coefficients. A 2.2F ceramic capacitor is recommended for most applications. For optimum noise immunity and low input ripple, the input capacitor value can be increased. For the LDOs, use an input capacitance equal to the value of the sum of the output capacitance of LDO1 and where BUCK is the efficiency of the DC-DC step-down converter, and PBUCK is the output power of the DC-DC step-down converter. ______________________________________________________________________________________ 11 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Table 2. Suggested Inductors MANUFACTURER SERIES CB2016T Taiyo Yuden CB2518T 2.2 4.7 1.0 1.5 2.2 1.0 2.2 1.0 2.2 1.0 1.2 2.2 1.5 2.2 1.5 2.2 1.2 1.5 2.2 1.5 2.2 3.3 1.0 1.5 2.2 1.0 2.2 1.0 2.2 1.5 2.2 0.09 0.13 0.05 0.07 0.08 0.11 0.06 0.10 0.20 0.09 0.15 0.13 0.17 0.10 0.12 0.08 0.09 0.12 0.05 0.08 0.10 0.07 0.10 0.13 0.08 0.12 0.07 0.10 0.070 0.100 510 340 1500 1500 1300 1100 1000 790 1170 860 640 1230 1080 1290 1140 590 520 440 680 580 450 1600 1400 1100 1400 1000 1400 1100 2200 1800 2.5 x 1.8 x 2.0 = 9mm3 2.5 x 2.0 x 1.0 = 5mm3 2.0 x 1.6 x 1.0 = 3.2mm3 3.2 x 2.5 x 1.7 = 14mm3 3.0 x 3.0 x 1.0 = 9mm3 3.0 x 3.0 x 1.2 = 11mm3 3.6 x 3.6 x 1.0 = 13mm3 3.6 x 3.6 x 1.2 = 16mm3 3.0 x 3.0 x 1.0 = 9mm3 INDUCTANCE (H) 1.0 2.2 ESR () 0.09 0.13 CURRENT RATING (mA) 510 DIMENSIONS (mm) 2.0 x 1.6 x 1.8 = 5.8mm3 MIPF2520 FDK MIPF2016 Murata LQH32C_53 D3010FB D2812C TOKO D310F D312C CDRH2D09 Sumida CDRH2D11 3.2 x 3.2 x 1.2 = 12mm3 Coilcraft LPO3310 3.3 x 3.3 x 1.0 = 11mm3 3.2 x 3.2 x 1.2 = 12mm3 3.2 x 3.2 x 1.5 = 15mm3 2.5 x 2.0 x 1.0 = 5mm3 ELC3FN Panasonic ELL3GM Hitachi KSLI-252010 12 ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP The maximum allowed power dissipation, PMAX, is: PMAX = PCB Layout High switching frequencies and relatively large peak currents make the PCB layout a very important part of design. Good design minimizes excessive EMI on the feedback paths and voltage gradients in the ground plane, resulting in a stable and well regulated output. Minimize the ground loop formed by CIN1, CBUCK, and PGND. To do this, connect CIN1 close to IN1A/IN1B and PGND. Connect the inductor and output capacitor as close as possible to the IC and keep their traces short, direct, and wide. Keep noisy traces, such as the LX node, as short as possible. Connect AGND and PGND to the common ground plane. Figure 1 illustrates an example PCB layout and routing scheme. MAX8884Y/MAX8884Z (TJ _ MAX - TA ) JA where (T JMAX - T A ) is the temperature difference between the MAX8884Y/MAX8884Z die junction and the surrounding air, and JA is the thermal resistance of the junction through the PCB, copper traces, and other materials to the surrounding air. LDO1_EN BUCK_EN SEL LDO2_EN GND CREFBP REFBP A1 LDO2 CLDO2 IN2 C1 LDO1 D1 3.8mm CIN2 SEL C2 LDO1_EN D2 IN1B C3 NC2 D3 IN1A C4 FB D4 LDO2 B1 AGND A2 NC1 A3 PGND A4 LX B4 CIN1 CBUCK BUCK_EN LDO2_EN B2 B3 CLDO1 LBUCK IN LDO1 4.0mm BUCK Figure 1. Recommended PCB Layout ______________________________________________________________________________________ 13 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Block Diagram IN1A IN1B REF R7 PWM ERROR AMP PWM LOGIC SEL R6 C2 LX STEP-DOWN CURRENT LIMIT R1 C1 R3 PGND FB R2 IN2 REFBP AGND REFBP REF ERROR AMP R9 LDO1_EN LDO2_EN SEL BUCK_EN CONTROL LOGIC LDO1_EN R8 CURRENT LIMIT LDO1 SEL R7 CURRENT LIMIT ERROR AMP LDO2 R12 R11 REFBP MAX8884Y MAX8884Z LDO2_EN R10 14 ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Typical Application Circuit MAX8884Y/MAX8884Z IN1A Li+ BATTERY 2.2F IN1B MAX8884Y MAX8884Z 2-4MHz BUCK BASEBAND PROCESSOR GPIO GPIO GPIO 2.2H (MAX8884Y) 1.0H (MAX8884Z) LX FB PGND 1.2V CAMERA MODULE CORE 2.2F BUCK_EN LDO1_EN LDO2_EN SEL CONTROL REFBP 4.7F IN2 REF AGND LDO1 0.033F DIGITAL 2.2F LDO1 LDO2 2.2F LDO2 ANALOG Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 16 CSP PACKAGE CODE R162A2+1 DOCUMENT NO. 21-0226 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15 (c) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. |
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