19-4418; Rev 0; 4/09 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Features 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 50μA. 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 2.2μF 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). ♦ 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 26µVRMS (typ) Output Noise High 65dB (typ) PSRR Simple Logic ON/OFF Control ♦ Low 0.1µA Shutdown Current ♦ 2.7V to 5.5V Supply Voltage Range ♦ Thermal Shutdown ♦ Tiny, 2mm x 2mm x 0.65mm CSP Package (4x4 Grid) Applications Cell Phones/Smartphones Ordering Information PART SWITCHING FREQUENCY PIN-PACKAGE MAX8884YEREKE+T 16 CSP 2MHz MAX8884ZEREKE+T 16 CSP 4MHz Note: All devices are specified over the -40°C to +85°C operating temperature range. PDA and Palmtop Computers Portable MP3 and DVD Players Digital Cameras, Camcorders +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. PCMCIA Cards Typical Application Circuit appears at end of data sheet. Handheld Instruments Pin Configuration Typical Operating Circuit TOP VIEW (BUMPS ON BOTTOM) BATT 2.7V TO 5.5V BUCK 1.2V/1.8V IN1A 2.2μF IN1B LX 2.2μH BUCK ON/OFF BUCK_EN MAX8884Y MAX8884Z SEL LDO1 ON/OFF LDO1_EN LDO2 ON/OFF LDO2_EN PGND A2 A3 A4 REFBP AGND NC1 PGND B1 B2 B3 B4 LDO2 BUCK_EN LDO2_EN LX C1 C2 C3 C4 IN2 SEL IN1B IN1A D1 D2 D3 D4 LDO1 LDO1_EN NC2 FB AGND LDO1 VLDO1 UP TO 300mA LDO2 VLDO2 UP TO 300mA BATT 2.7V TO 5.5V IN2 A1 2.2μF REFBP BUCK/LDO1 VOLTAGE SELECTION MAX8884Y MAX8884Z FB CSP ________________________________________________________________ Maxim Integrated Products 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. 1 MAX8884Y/MAX8884Z General Description MAX8884Y/MAX8884Z 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP 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 = +70°C) 16-Bump CSP (derate 12.5mW/°C above +70°C) ..............1W Operating Temperature .......................................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Bump Temperature*.........................................................+260°C *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 = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 5.5 V 2.63 2.70 V TA = +25°C 0.1 4 TA = +85°C 0.1 INPUT SUPPLY Input Voltage VIN1A, VIN1B, VIN2 2.7 Input Undervoltage Threshold VIN1A, VIN1B, VIN2 rising, 180mV typical hysteresis 2.52 Shutdown Supply Current VBUCK_EN = VLDO1_EN = VLDO2_EN = 0 No-Load Supply Current VBUCK_EN = 0, ILDO1 = ILDO2 = 0A VLDO1_EN = VLDO2_EN = 0, IBUCK = 0A, no switching μA 140 230 μA 50 80 μA THERMAL PROTECTION Thermal Shutdown TA rising, 20°C typical hysteresis +160 °C LOGIC CONTROL Logic Input-High Voltage (BUCK_EN, SEL, LDO1_EN, LDO2_EN) 2.7V VIN1A = VIN1B = VIN2 5.5V Logic Input-Low Voltage (BUCK_EN, SEL, LDO1_EN, LDO2_EN) 2.7V VIN1A = VIN1B = VIN2 5.5V Logic Input Current (BUCK_EN, SEL, LDO1_EN, LDO2_EN) VIL = 0 or VIH = VIN1A = 5.5V 1.3 V 0.4 TA = +25°C 0.01 TA = +85°C 0.1 1 V μA FB Buck Converter Output Voltage SEL = AGND, IBUCK = 0A VSEL = VIN1A, IBUCK = 0A FB Leakage Current VIN1A = VIN1B = VIN2 = 5.5V, VFB = 0 1.18 1.78 1.22 1.24 V V 1.80 1.85 TA = +25°C 0.01 1 TA = +85°C 1 μA LX On-Resistance 2 p-channel MOSFET switch, ILX = -40mA 0.18 0.30 n-channel MOSFET rectifier, ILX = 40mA 0.15 0.25 _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP (VIN1A = VIN1B = VIN2 = VLDO1_EN = VLDO2_EN = VBUCK_EN = 3.6V. TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER LX Leakage Current CONDITIONS VIN1A = VIN1B = VIN2 = 5.5V, VLX = 0 MIN TYP MAX TA = +25°C 0.1 1 TA = +85°C 1 UNITS μA p-Channel MOSFET Peak Current VLX = 0 Limit 0.8 1.0 1.2 A n-Channel MOSFET Valley Current Limit 0.6 0.8 1.0 A n-Channel MOSFET Zero-Crossing Threshold MAX8884Y_ 40 MAX8884Z_ 60 Minimum On-Time mA 0.07 Minimum Off-Time μs 0.06 Power-Up Delay From VBUCK_EN rising to VLX rising μs 120 250 1.800 1.836 μs LDO1, LDO2 Output Voltage VLDO1 VIN2 = 5.5V, ILDO_ = 1mA; VIN2 = 3.4V, ILDO_ = 100mA Output Voltage VLDO2 VIN2 = 5.5V, ILDO_ = 1mA; VIN2 = 3.4V, ILDO_ = 100mA SEL = AGND 1.764 SEL = IN1_ Output Current V 2.800 2.770 2.800 2.830 450 750 200 300 mA Current Limit VLDO_ = 0 Dropout Voltage ILDO_ = 100mA, TA = +25°C (VLDO_ 2.5V) 70 Line Regulation VIN2 stepped from 3.5V to 5.5V, ILDO_ = 100mA 2.4 mV Load Regulation ILDO_ stepped from 50μA to 200mA 25 mV Power-Supply Rejection VLDO_/VIN2 10Hz to 100kHz, VLDO_ = 1.8V, CLDO_ = 2.2μF, ILDO_ = 30mA 65 dB Output Noise 10Hz to 100kHz, VLDO_ = 1.8V, CLDO_ = 2.2μF, ILDO_ = 30mA 26 μVRMS 0 < ILDO_ < 10mA 0.1 Output Capacitor for Stable Operation 310 V mA mV μF 10mA < ILDO_ < 200mA 200mA < ILDO_ < 300mA 1 2.2 Shutdown Output Impedance VLDO1_EN = VLDO2_EN = 0 100 Power-Up Delay From VLDO_EN rising to VLDO_ output rising 150 250 μs 1.250 1.263 V 0.2 5 mV REFBP REFBP Output Voltage 0 IREFBP 1μA REFBP Supply Rejection VIN2 stepped from 2.55V to 5.5V 1.237 Note 1: All devices are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design. _______________________________________________________________________________________ 3 MAX8884Y/MAX8884Z ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25°C, unless otherwise noted.) 90 80 70 EFFICIENCY (%) EFFICIENCY (%) 80 MAX8884Y, VIN = 3.2V = 3.6V = 4.2V MAX8884Z, VIN = 3.2V = 3.6V = 4.2V 60 50 70 MAX8884Y, VIN = 3.2V = 3.6V = 4.2V MAX8884Z, VIN = 3.2V = 3.6V = 4.2V 60 50 300 MAX8884Y/Z toc03 90 MAX8884Y/Z toc02 100 MAX8884Y/Z toc01 100 STEP-DOWN CONVERTER NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE STEP-DOWN CONVERTER EFFICIENCY vs. LOAD CURRENT, VOUT = 1.2V VBUCK_EN = VIN VLDO1_EN = VLDO2_EN = 0 250 SUPPLY CURRENT (μA) STEP-DOWN CONVERTER EFFICIENCY vs. LOAD CURRENT, VOUT = 1.8V 200 VIN FALLING 150 VIN RISING 100 40 40 50 30 30 0 MAX8884Y MAX8884Z 1 10 100 1000 10 1 100 0 1000 1 2 3 4 5 LOAD CURRENT (mA) LOAD CURRENT (mA) INPUT VOLTAGE (V) STEP-DOWN OUTPUT VOLTAGE vs. LOAD CURRENT (VOLTAGE POSITIONING) MAX8884Z STEP-DOWN CONVERTER LIGHT LOAD SWITCHING WAVEFORMS MAX8884Y STEP-DOWN CONVERTER LIGHT LOAD SWITCHING WAVEFORMS 1.8 SEL = IN1_ 1.7 VOUT 1.6 ILX 1.5 AC-COUPLED VOUT 20mV/div AC-COUPLED 10mV/div 100mA/div 100mA/div ILX 0A 0A 1.4 6 MAX8884Y/Z toc06 MAX8884Y/Z toc05 MAX8884Y/Z toc04 1.9 OUTPUT VOLTAGE (V) MAX8884Y/MAX8884Z 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP 1.3 VLX 1.2 2V/div SEL = AGND 1.1 2V/div VLX 0V 0V ILOAD = 50mA 1.0 1 10 100 1000 1μs/div 400ns/div LOAD CURRENT (mA) MAX8884Z STEP-DOWN CONVERTER HEAVY LOAD SWITCHING WAVEFORMS MAX8884Y STEP-DOWN CONVERTER HEAVY LOAD SWITCHING WAVEFORMS MAX8884Y/Z toc07 MAX8884Y/Z toc08 AC-COUPLED 10mV/div VOUT ILX 500mA/div AC-COUPLED 10mV/div VOUT 500mA/div ILX 0A 0A 2V/div VLX VLX 2V/div 0V 0V ILOAD = 500mA ILOAD = 500mA 200ns/div 4 400ns/div _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Z STEP-DOWN CONVERTER SOFT-START WAVEFORMS MAX8884Y STEP-DOWN CONVERTER SOFT-START WAVEFORMS MAX8884Y/Z toc09 VOUT MAX8884Y/Z toc10 1V/div VOUT 1V/div 0V 200mA/div IIN1 0V 200mA/div IIN1 0A 500mA/div ILX 0A 500mA/div ILX 0A 2V/div VBUCK_EN ILOAD = 500mA 0A 2V/div VBUCK_EN ILOAD = 500mA 0V 40μs/div 40μs/div MAX8884Y STEP-DOWN CONVERTER LINE TRANSIENT RESPONSE MAX8884Z STEP-DOWN CONVERTER LINE TRANSIENT RESPONSE MAX8884Y/Z toc11 4V MAX8884Y/Z toc12 4V 4V 1V/div VIN 4V 1V/div VIN 3.5V 3.5V AC-COUPLED 20mV/div VOUT ILX 200mA/div ILOAD = 500mA AC-COUPLED 20mV/div VOUT ILX 200mA/div ILOAD = 500mA 0A 10μs/div 10μs/div MAX8884Z STEP-DOWN CONVERTER LOAD TRANSIENT MAX8884Y STEP-DOWN CONVERTER LOAD TRANSIENT 1.8V DC OFFSET 100mV/div VOUT 500mA/div ILX 1.8V DC OFFSET 100mV/div VOUT 500mA/div ILX 0A 0A 500mA/div IOUT 500mA 500mA 500mA/div 10mA 0A MAX8884Y/Z toc14 MAX8884Y/Z toc13 IOUT 0V 0A 10mA 10mA 10mA 0A 20μs/div 20μs/div _______________________________________________________________________________________ 5 MAX8884Y/MAX8884Z Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25°C, unless otherwise noted.) MAX8884Y STEP-DOWN CONVERTER SHUTDOWN WAVEFORMS LDO1, LDO2 INPUT SUPPLY CURRENT vs. INPUT VOLTAGE MAX8884Y/Z toc15 ILX 500mA/div 0A VBUCK_EN ILOAD = 500mA VLDO1_EN = VLDO2_EN = VIN, VBUCK_EN = 0 300 SUPPLY CURRENT (μA) 0V MAX8884Y/Z toc16 350 1V/div VOUT 250 200 150 100 50 5V/div 0V 0 0 10μs/div 1 2 3 4 5 6 INPUT VOLTAGE (V) LDO POWER SUPPLY RIPPLE REJECTION, VOUT = 1.8V LDO2 DROPOUT VOLTAGE vs. LOAD CURRENT 150 100 MAX8884Y/Z toc18 DROPOUT VOLTAGE (V) 200 80 70 RIPPLE REJECTION (dB) MAX8884Y/Z toc17 250 60 50 40 30 20 50 10 ILDO = 30mA 0 0 0 50 100 150 200 250 300 0.01 0.1 1 10 100 LOAD CURRENT (mA) FREQUENCY (kHz) LDO POWER SUPPLY RIPPLE REJECTION, VOUT = 2.8V LDO OUTPUT VOLTAGE NOISE WAVEFORM, VOUT_ = 1.8V MAX8884Y/MAX8884Z LDO1 = 1.8 AT 30mA VIN = 3.6V MAX8884Y/Z toc19 60 50 40 50μV/div 30 20 10 VN = 26.1μVRMS, f = 100Hz to 100kHz, ILDO_ = 30mA ILDO_ = 30mA 0 0.01 0.1 1 10 100 1000 400μs/div FREQUENCY (kHz) 6 1000 MAX8884Y/Z toc20 70 RIPPLE REJECTION (dB) MAX8884Y/MAX8884Z 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP LDO OUTPUT-NOISE SPECTRAL DENSITY vs. FREQUENCY, VLDO_ = 1.8V 1000 100 MAX884Y/Z toc22 10,000 NOISE DENSITY (nV√(Hz)) MAX884Y/Z toc21 NOISE DENSITY (nV√(Hz)) 10,000 LDO OUTPUT-NOISE SPECTRAL DENSITY vs. FREQUENCY, VLDO_ = 2.8V 1000 100 ILDO_ = 30mA ILDO_ = 30mA 10 10 0.01 0.1 1 10 100 1000 0.01 FREQUENCY (kHz) 0.1 1 10 LDO1, LDO2 LINE TRANSIENT MAX8884Y/Z toc24 4V VIN 1000 LDO1, LDO2 LOAD TRANSIENT RESPONSE MAX8884Y/Z toc23 4V 100 FREQUENCY (kHz) ILDO2 1V/div 3.5V 50mA/div 40mA 1mA 1mA AC-COUPLED 10mV/div VLDO2 VLDO1 AC-COUPLED 5mV/div VLDO2 AC-COUPLED 5mV/div ILDO1 40mA 1mA 50mA/div 1mA AC-COUPLED 10mV/div VLDO1 ILDO1 = ILDO2 = 100mA 10μs/div 20μs/div _______________________________________________________________________________________ 7 MAX8884Y/MAX8884Z Typical Operating Characteristics (continued) (VIN = VIN1A = VIN1B = VIN2 = 3.6V, VBUCK = 1.2V, VLDO1 = 1.8V, VLDO2 = 2.8V, MAX8884YEVKIT, TA = +25°C, unless otherwise noted.) MAX8884Y/MAX8884Z 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 = +25°C, unless otherwise noted.) LDO1, LDO2 LOAD TRANSIENT RESPONSE NEAR DROPOUT LDO1, LDO2 STARTUP AND SHUTDOWN RESPONSE MAX8884Y/Z toc25 40mA ILDO2 MAX8884Y/Z toc26 50mA/div 1mA 1mA AC-COUPLED 10mV/div VLDO2 50mA/div 40mA ILDO1 1mA VLDO1_EN = VLDO2_EN 2V/div 0V VLDO1 2V/div 0V VLDO2 2V/div 0V 1mA AC-COUPLED 10mV/div VLDO1 VIN2 = VLDO2 + 200mV 20μs/div 400μs/div REFBP SOFT-START CREFBP = 0.033μF REFBP SOFT-START CREFBP = 0.15μF MAX8884Y/Z toc27 MAX8884Y/Z toc28 1V/div VREFBP 1V/div VREFBP 0V 0V 2V/div VLDO1_EN VLDO1_EN 2V/div 0V VLDO1 1V/div 0V 1V/div VLDO1 0V 100μs/div 8 0V 100μs/div _______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP PIN NAME FUNCTION Reference Noise Bypass. Bypass REFBP to AGND with a 0.033μF ceramic capacitor to reduce noise on the LDO outputs. REFBP is internally pulled to ground through a 1kΩ resistor during shutdown. A1 REFBP A2 AGND A3 NC1 A4 PGND Power Ground for Step-Down Converter. Connect to common ground plane. B1 LDO2 300mA LDO Regulator 2 Output. For 300mA application, bypass LDO2 with a 2.2μF ceramic capacitor as close as possible to LDO2 and AGND. For low-output current capability, up to 10mA, an output capacitor of 0.1μF is sufficient to keep the output voltage stable. LDO2 is internally pulled to ground through a 100Ω resistor when this regulator is disabled. B2 BUCK_EN 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. B3 LDO2_EN 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. B4 LX Inductor Connection. Connect an inductor from LX to the output of the step-down converter. C1 IN2 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 4.7μF ceramic capacitor as close as possible to IN2 and AGND. Connect IN2 to the same source as IN1A and IN1B. C2 SEL Output Voltage Selection for LDO1 and Step-Down Converter. Connect to IN1_ or AGND for output voltage selection. See Table 1. Low-Noise Analog Ground. Connect to common ground plane. No Internal Connection. Connect NC1 to ground. IN1B, IN1A 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 2.2μF 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. D1 LDO1 300mA LDO Regulator 1 Output. For 300mA application, bypass LDO1 with a 2.2μF ceramic capacitor as close as possible to LDO1 and AGND. For low-output current capability, up to 10mA, an output capacitor of 0.1μF is sufficient to keep output voltage stable. LDO1 is internally pulled to AGND through a 100Ω resistor when this regulator is disabled. D2 LDO1_EN 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. D3 NC2 D4 FB C3, C4 No Internal Connection. Connect NC2 to ground. FB is Connected to the Internal Feedback Network 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 MAX8884Y/MAX8884Z Pin Description MAX8884Y/MAX8884Z 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP 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. 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 × 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 Table 1. SEL Output Voltage Selection SEL BUCK CONVERTER OUTPUT VOLTAGE (V) LDO1 OUTPUT VOLTAGE (V) AGND 1.2 1.8 IN1_ 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. Thermal Shutdown Thermal shutdown limits total power dissipation in the MAX8884Y/MAX8884Z. If the junction temperature exceeds +160°C, 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 20°C. 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 LDO Dropout Voltage SEL is used to determine the output voltage of the buck converter and LDO1. See Table 1. 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 100Ω 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 0.1μA (typ). 10 Inductor Selection The MAX8884Y operates with a switching frequency of 2MHz and utilizes a 2.2μH inductor. The MAX8884Z operates with a switching frequency of 4MHz and utilizes a 1μH 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. ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP 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 2.2μF ceramic capacitor is recommended for most applications. For optimum load-transient performance and very low output ripple, the output capacitor value can be increased. 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 -10°C. With X7R or X5R dielectrics, a capacitance equal to the sum is sufficient at all operating temperatures. Reference Noise Bypass Capacitor Selection The REFBP capacitor reduces the output noise of LDO1 and LDO2. A value of 0.033μF is sufficient for most applications. This value can be increased up to 0.150μF 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 0.150μF as this degrades the performance of the internal reference voltage and has a corresponding impact on all output voltages. 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 0.1μF ceramic capacitor for stable operation over the full temperature range. For loads up to 200mA, an output capacitor of 1μF is sufficient for stable operation over the entire temperature range. Operating the LDO at maximum rated current the LDO1 and LDO2 requires a 2.2μF ceramic capacitor. Using larger output capacitors reduces output noise and improves load-transient response, stability, and power-supply rejection. 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 -10°C. Tantalum capacitors are not recommended. 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 4.7μF or more to ensure stability at temperatures below -10°C. With X7R or X5R dielectrics, 2.2μF is sufficient at all operating temperatures. These regulators are optimized for ceramic capacitors. Tantalum capacitors are not recommended. 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 +160°C, 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 100Ω resistor. 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 2.2μF 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 Thermal Considerations 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 ) ⎝ ηBUCK ⎠ where ηBUCK is the efficiency of the DC-DC step-down converter, and PBUCK is the output power of the DC-DC step-down converter. ______________________________________________________________________________________ 11 MAX8884Y/MAX8884Z 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 50mΩ to 150mΩ range. See Table 2 for suggested inductors and manufacturers. MAX8884Y/MAX8884Z 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP Table 2. Suggested Inductors MANUFACTURER SERIES INDUCTANCE (μH) ESR () CURRENT RATING (mA) DIMENSIONS (mm) CB2016T 1.0 2.2 0.09 0.13 510 2.0 x 1.6 x 1.8 = 5.8mm3 CB2518T 2.2 4.7 0.09 0.13 510 340 2.5 x 1.8 x 2.0 = 9mm3 MIPF2520 1.0 1.5 2.2 0.05 0.07 0.08 1500 1500 1300 2.5 x 2.0 x 1.0 = 5mm3 MIPF2016 1.0 2.2 0.11 1100 2.0 x 1.6 x 1.0 = 3.2mm3 LQH32C_53 1.0 2.2 0.06 0.10 1000 790 3.2 x 2.5 x 1.7 = 14mm3 D3010FB 1.0 0.20 1170 3.0 x 3.0 x 1.0 = 9mm3 D2812C 1.2 2.2 0.09 0.15 860 640 3.0 x 3.0 x 1.2 = 11mm3 D310F 1.5 2.2 0.13 0.17 1230 1080 3.6 x 3.6 x 1.0 = 13mm3 D312C 1.5 2.2 0.10 0.12 1290 1140 3.6 x 3.6 x 1.2 = 16mm3 CDRH2D09 1.2 1.5 2.2 0.08 0.09 0.12 590 520 440 3.0 x 3.0 x 1.0 = 9mm3 CDRH2D11 1.5 2.2 3.3 0.05 0.08 0.10 680 580 450 3.2 x 3.2 x 1.2 = 12mm3 LPO3310 1.0 1.5 2.2 0.07 0.10 0.13 1600 1400 1100 3.3 x 3.3 x 1.0 = 11mm3 ELC3FN 1.0 2.2 0.08 0.12 1400 1000 3.2 x 3.2 x 1.2 = 12mm3 ELL3GM 1.0 2.2 0.07 0.10 1400 1100 3.2 x 3.2 x 1.5 = 15mm3 KSLI-252010 1.5 2.2 0.070 0.100 2200 1800 2.5 x 2.0 x 1.0 = 5mm3 Taiyo Yuden FDK Murata TOKO Sumida Coilcraft Panasonic Hitachi 12 ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP (TJ _ MAX − TA ) θJA BUCK_EN LDO1_EN where (T JMAX - T A ) is the temperature difference between the MAX8884Y/MAX8884Z die junction and the surrounding air, and θJA is the thermal resistance of the junction through the PCB, copper traces, and other materials to the surrounding air. SEL LDO2_EN PMAX = 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. GND CREFBP LDO2 REFBP AGND NC1 PGND A1 A2 A3 A4 BUCK_EN LDO2_EN LDO2 LX B1 B2 B3 B4 IN2 SEL IN1B IN1A C1 C2 C3 C4 LDO1 LDO1_EN NC2 FB D1 D2 D3 D4 CIN1 CLDO2 CBUCK 3.8mm CIN2 CLDO1 LBUCK IN BUCK LDO1 4.0mm Figure 1. Recommended PCB Layout ______________________________________________________________________________________ 13 MAX8884Y/MAX8884Z PCB Layout The maximum allowed power dissipation, PMAX, is: 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP MAX8884Y/MAX8884Z Block Diagram IN1A IN1B REF PWM ERROR AMP R7 PWM LOGIC SEL R6 LX C2 STEP-DOWN CURRENT LIMIT PGND FB R1 C1 R3 R2 IN2 REFBP REFBP CURRENT LIMIT REF AGND ERROR AMP LDO1 R9 LDO1_EN LDO2_EN SEL BUCK_EN CONTROL LOGIC R8 LDO1_EN SEL R7 REFBP CURRENT LIMIT ERROR AMP MAX8884Y MAX8884Z LDO2 R12 LDO2_EN R11 R10 14 ______________________________________________________________________________________ 700mA DC-DC Step-Down Converters with Dual 300mA LDO in 2mm x 2mm CSP IN1A Li+ BATTERY 2.2μF MAX8884Y MAX8884Z IN1B 2.2μH (MAX8884Y) 1.0μH (MAX8884Z) LX FB 2–4MHz BUCK BASEBAND PROCESSOR 1.2V CAMERA MODULE CORE 2.2μF BUCK_EN LDO1_EN LDO2_EN SEL GPIO GPIO GPIO PGND CONTROL REFBP 4.7μF IN2 REF AGND 0.033μF LDO1 DIGITAL 2.2μF LDO1 LDO2 ANALOG 2.2μF LDO2 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16 CSP R162A2+1 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX8884Y/MAX8884Z Typical Application Circuit