19-0784; Rev 1; 7/07 KIT ATION EVALU E L B AVAILA 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables The MAX8667/MAX8668 dual step-down converters with dual low-dropout (LDO) linear regulators are intended to power low-voltage microprocessors or DSPs in portable devices. They feature high efficiency with small external component size. The step-down converters are adjustable from 0.6V to 3.3V (MAX8668) or factory preset (MAX8667) with guaranteed output current of 600mA for OUT1 and 1200mA for OUT2. The 1.5MHz hysteretic-PWM control scheme allows for tiny external components and reduces no-load operating current to 100µA with all outputs enabled. Dual low-quiescent-current, low-noise LDOs operate down to 1.7V supply voltage. The MAX8667/MAX8668 have individual enables for each output, maximizing flexibility. The MAX8667/MAX8668 are available in the spacesaving, 3mm x 3mm, 16-pin thin QFN package. Applications Cell Phones/Smartphones PDA and Palmtop Computers Portable MP3 and DVD Players Features o Tiny, Thin QFN 3mm x 3mm Package o Individual Enables o Step-Down Converters 600mA Guaranteed Output Current on OUT1 1200mA Guaranteed Output Current on OUT2 Tiny Size 2.2µH Chip Inductor (0805) Output Voltage from 0.6V to 3.3V (MAX8668) Ultra-Fast Line and Load Transients Low 25µA Supply Current Each o LDOs 300mA Guaranteed Low 1.7V Minimum Supply Voltage Low Output Noise Ordering Information PART PKG CODE TOP MARK MAX8667ETEAA+ T1633-4 AEQ MAX8667ETEAB+ T1633-4 AFI MAX8667ETEAC+ T1633-4 AFM MAX8667ETECQ+ T1633-4 AFN Note: All MAX8667/MAX8668 parts are in a 16-pin, thin QFN, 3mm x 3mm package and operate in the -40°C to +85°C extended temperature range. Digital Cameras, Camcorders PCMCIA Cards +Denotes a lead-free package. Handheld Instruments Ordering Information continued at the end of data sheet. Selector Guide appears at the end of data sheet. Pin Configuration EN3 EN2 REF OUT3 EN4 2.2µF OUT2 (FB2) 300mA OUT1 (FB1) 14 7 REF 6 GND 5 EN4 4.7µF MAX8667 MAX8668 EN1 15 EN2 16 2.2µH 1.2A LX2 OUT2 PGND2 1 EN3 OUT1 PGND1 9 8 4.7µF 2.2µH LX1 10 PGND1 13 MAX8667 600mA 11 300mA OUT4 GND 12 2.2µF 2 3 4 OUT4 0.01µF PGND2 4.7µF IN34 IN34 IN12 EN1 OUT3 10µF LX2 TOP VIEW IN12 2.6V TO 5.5V LX1 Typical Operating Circuit THIN QFN (3mm x 3mm) ( ) ARE FOR THE MAX8668 ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX8667/MAX8668 General Description MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables ABSOLUTE MAXIMUM RATINGS IN12, IN34, FB1, FB2, EN1, EN2, EN3, EN4, OUT1, OUT2, REF to GND............................................-0.3V to +6.0V OUT3, OUT4 to GND.....-0.3V to the lesser of + 6V or (VIN34 + 0.3V) PGND1, PGND2 to GND .......................................-0.3V to +0.3V LX1, LX2 Current ..........................................................1.5A RMS LX1, LX2 to GND (Note 1) .......................-0.3V to (VIN12 + 0.3V) Continuous Power Dissipation (TA = +70°C) 16-Pin, 3mm x 3mm Thin QFN (derate 20.8mW/°C above +70°C) .............................1667mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ..................................................... +150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: LX_ has internal clamp diodes to GND and IN12. Applications that forward bias these diodes should take care not to exceed the IC’s package-dissipation limits. 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 (VIN34 = VIN12 = 3.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER MAX UNITS VIN12 ≥ VIN34 1.7 5.5 V IN12 Supply Range MAX8668, VIN12 ≥ VIN34 2.6 5.5 V IN12 Suppy Range MAX8667, VIN12 ≥ VIN34 2.8 5.5 V 1 µA IN34 Supply Range CONDITIONS MIN TYP TA = +25°C Shutdown Supply Current, IIN12 + IIN34 VIN12 = VIN34 = 4.2V VEN_ = 0V No Load Supply Current, IIN12 + IIN34 MAX8667ETEJS+, all regulators enabled TA = +85°C 0.05 µA 100 150 µA 2.5 2.6 V 1.7 V UNDERVOLTAGE LOCKOUT IN12 UVLO IN34 UVLO VIN12 rising 2.4 VIN12 hysteresis 0.1 VIN34 rising 1.5 VIN34 hysteresis 1.6 V 0.1 V +160 °C 15 °C THERMAL SHUTDOWN Threshold TA rising Hysteresis REFERENCE Reference Bypass Output Voltage REF Supply Rejection 0.591 2.6V ≤ (VIN12 = VIN34) ≤ 5.5V 0.600 0.609 0.15 V mV/V LOGIC AND CONTROL INPUTS EN_ Input Low Level 1.7V ≤ VIN34 ≤ 5.5V 2.6V ≤ VIN12 ≤ 5.5V EN_ Input High Level 1.7V ≤ VIN34 ≤ 5.5V 2.6V ≤ VIN12 ≤ 5.5V EN_ Input Leakage Current VIN12 = VIN34 = 5.5V 0.4 1.44 TA = +25°C TA = +85°C V V -1 +1 0.001 µA STEP-DOWN CONVERTERS Minimum Adjustable Output Voltage 2 MAX8668 0.6 _______________________________________________________________________________________ V 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables (VIN34 = VIN12 = 3.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS Maximum Adjustable Output Voltage MAX8668 FB1, FB2 Regulation Voltage MAX8668, no load, VFB_ falling TA = +25°C 0.588 0.600 0.612 TA = -40°C to +85°C 0.582 0.600 0.618 OUT1, OUT2 Regulation Voltage MAX8667ETEJS+, no load, VOUT_ falling TA = +25°C 1.274 1.300 1.326 TA = -40°C to +85°C 1.261 1.300 1.339 FB1, FB2 Line Regulation MAX8668, VIN12 = 2.6V to 5.5V 0.01 %/V %/V OUT1, OUT2 Line Regulation FB1, FB2 Bias Current OUT1 Current Limit OUT2 Current Limit OUT1 On-Resistance OUT2 On-Resistance 3.3 MAX8667, VIN12 = 2.8V to 5.5V 0.05 MAX8668, shutdown mode 0.1 MAX8668, VFB1 = 0.5V 0.01 700 900 1100 nMOSFET rectifier (valley current) 500 750 1000 pMOSFET switch (ILIMP2) 1333 1667 2000 nMOSFET rectifier (valley current) 1200 1500 1800 pMOSFET switch, ILX1 = -400mA 0.3 0.6 nMOSFET rectifier, ILX1 = 400mA 0.3 0.6 pMOSFET switch, ILX2 = -400mA 0.12 0.27 nMOSFET rectifier, ILX2 = 400mA 0.12 0.27 60 120 LX_ = 5.5V TA = +25°C -1 TA = +85°C V V µA pMOSFET switch (ILIMP1) Rectifier-Off Current Threshold (ILXOFF) LX Leakage Current V +1 0.1 mA mA Ω Ω mA µA Minimum On-Time 100 ns Minimum Off-Time 50 ns LDO REGULATORS Supply Current Each LDO Output-Voltage Accuracy 20 µA 1mA load, TA = +25°C -1.5 +1.5 1mA to 300mA load -3.0 +3.0 Line Regulation VIN34 = 3.6V to 5.5V, 1mA load Dropout Voltage VIN34 = 1.8V, 300mA load Current Limit VOUT3, VOUT4 90% of nominal value Soft-Start Ramp Time To 90% of final value 0.1 ms Output Noise 100Hz to 100kHz, 30mA load, VOUT3 and VOUT4 = 2.8V 75 µVRMS Power-Supply Rejection Ratio f < 1kHz, 30mA load 57 dB 1 kΩ Shutdown Output Resistance 0.003 % 375 %/V 130 250 mV 420 465 mA TIMING (See Figure 2) Power-On Time (tPWRON) Enable Time (tEN) OUT1, OUT2 25 OUT3, OUT4 45 OUT1, OUT2 15 OUT3, OUT4 35 µs µs Note 1: All devices are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design. _______________________________________________________________________________________ 3 MAX8667/MAX8668 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VIN12 = VIN34 = 3.6V, circuit of Figure 4, VOUT1 = 1.2V, VOUT2 = 1.8V, VOUT3 = 2.8V, VOUT4 = 2.8V, TA = +25°C, unless otherwise noted.) OUT1 EFFICIENCY vs. LOAD CURRENT (VOUT1 = 1.2V) 70 50 40 30 20 60 50 40 30 ONLY OUT2 ENABLED 1 100 10 1000 0.1 1 10 100 1000 0 10000 100 200 300 400 500 600 LOAD CURRENT (mA) OUT2 LOAD REGULATION OUT1 OUTPUT VOLTAGE vs. INPUT VOLTAGE (600mA LOAD) OUT2 OUTPUT VOLTAGE vs. INPUT VOLTAGE (1200mA LOAD) 1.30 1.20 1.25 1.20 1.15 600 800 1000 1.65 1200 1.60 2.5 SWITCHING FREQUENCY vs. LOAD CURRENT 3.0 3.5 2500 2000 OUT2 1500 1000 4.0 4.5 5.0 5.5 0 600 900 1200 LOAD CURRENT (mA) 1500 1800 3.5 4.0 4.5 5.0 5.5 NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE ALL REGULATOR ENABLED NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE OUT1 AND OUT2 ONLY 120 MAX8667/88 toc08 100 80 SUPPLY VOLTAGE RISING 60 40 SUPPLY VOLTAGE FALLING 100 SUPPLY VOLTAGE FALLING 80 60 SUPPLY VOLTAGE RISING 40 20 0 300 3.0 INPUT VOLTAGE (V) 20 OUT1 2.5 INPUT VOLTAGE (V) 120 SUPPLY CURRENT (µA) MAX8667/88 toc07 3000 1.75 1.05 LOAD CURRENT (mA) 3500 1.80 1.70 SUPPLY CURRENT (µA) 400 1.85 1.10 1.00 200 1.90 MAX8667/88 toc09 1.40 1.95 OUTPUT VOLTAGE (V) 1.50 1.30 MAX8667/88 toc06 1.35 OUTPUT VOLTAGE (V) 1.60 2.00 MAX8667/88 toc05 1.40 MAX8667/88 toc04 1.70 0 0.95 LOAD CURRENT (mA) 1.80 500 1.00 LOAD CURRENT (mA) 1.90 0 1.05 0.80 0 0.1 1.10 0.85 10 0 OUTPUT VOLTAGE (V) 1.15 0.90 ONLY OUT1 ENABLED 4 1.20 20 10 MAX8667/88 toc03 80 EFFICIENCY (%) 60 1.25 OUTPUT VOLTAGE (V) 70 OUT1 LOAD REGULATION 90 MAX8667/88 toc02 80 EFFICIENCY (%) OUT2 EFFICIENCY vs. LOAD CURRENT (VOUT2 = 1.8V) MAX8667/88 toc01 90 SWITCHING FREQUENCY (kHz) MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 1.5 2.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5.0 5.5 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables VIN34 VOLTAGE FALLING 40 2.85 2.80 2.75 2.70 2.65 2.60 1 2 3 4 5 60 50 40 30 20 0 2.50 2.5 3.0 SUPPLY VOLTAGE (V) 3.5 4.0 4.5 5.0 0 5.5 100 200 300 LOAD CURRENT (mA) INPUT VOLTAGE (V) ENABLE WAVEFORMS SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX8667/88 toc14 1000 MAX8667/88 toc13 0 70 10 2.55 0 80 MAX8667/88 toc12 2.90 VIN34 VOLTAGE RISING 20 IN12 = IN34 2.4Ω LOAD ON OUT1 3.6Ω LOAD ON OUT2 NO LOAD ON OUT3 NO LOAD ON OUT4 900 800 SUPPLY CURRENT (mA) IIN34 (µA) 80 60 2.95 OUTPUT VOLTAGE (V) 100 3.00 MAX8667/88 toc11 VIN12 = 5.5V MAX8667/88 toc10 120 OUT3 DROPOUT VOLTAGE vs. LOAD CURRENT OUT3 OUTPUT VOLTAGE vs. INPUT VOLTAGE (300mA LOAD) DROPOUT VOLTAGE (mV) NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE OUT3 AND OUT4 ONLY 700 5V/div EN1/EN2/ EN3/EN4 VOUT1 600 VOUT2 500 VOUT3 400 VOUT4 300 2V/div 2V/div 2V/div 2V/div 2A/div IL1 200 2A/div 2A/div IL2 100 IIN12 + IIN34 0 2.5 3.0 3.5 4.0 4.5 5.0 40µs/div 5.5 SUPPLY VOLTAGE (V) OUT1 LOAD TRANSIENT SHUTDOWN WAVEFORMS MAX8667/88 toc16 MAX8667/88 toc15 EN1/EN2/ EN3/EN4 5V/div VOUT1 VOUT2 100mV/div (AC-COUPLED) VOUT1 300mA 1V/div VOUT3 1V/div VOUT4 IOUT1 10mA 10mA 200mA/div 1V/div IL1 200mA/div 1V/div 40µs/div 10µs/div _______________________________________________________________________________________ 5 MAX8667/MAX8668 Typical Operating Characteristics (continued) (VIN12 = VIN34 = 3.6V, circuit of Figure 4, VOUT1 = 1.2V, VOUT2 = 1.8V, VOUT3 = 2.8V, VOUT4 = 2.8V, TA = +25°C, unless otherwise noted.) MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Typical Operating Characteristics (continued) (VIN12 = VIN34 = 3.6V, circuit of Figure 4, VOUT1 = 1.2V, VOUT2 = 1.8V, VOUT3 = 2.8V, VOUT4 = 2.8V, TA = +25°C, unless otherwise noted.) OUT3 LOAD TRANSIENT OUT2 LOAD TRANSIENT MAX8667/88 toc18 MAX8667/88 toc17 200mV/div (AC-COUPLED) VOUT2 50mV/div (AC-COUPLED) VOUT3 600mA IOUT2 10mA 10mA 500mA/div 300mA IOUT3 200mA/div 500mA/div IL2 0mA 0mA 10µs/div 10µs/div OUT1 LIGHT-LOAD SWITCHING WAVEFORMS OUT4 LOAD TRANSIENT MAX8667/88 toc20 MAX8667/88 toc19 50mV/div (AC-COUPLED) VOUT4 VOUT1 20mV/div VLX1 2V/div 300mA IOUT4 200mA/div 0mA 0mA IL1 100mA/div 500µA LOAD 10µs/div 10µs/div OUT2 LIGHT-LOAD SWITCHING WAVEFORMS OUT1 HEAVY-LOAD SWITCHING WAVEFORMS MAX8667/88 toc21 VOUT2 MAX8667/88 toc22 20mV/div VLX2 2V/div VOUT1 20mV/div VLX1 2V/div 500mA/div IL2 500mA/div 500µA LOAD 500µA LOAD 40µs/div 6 IL1 400ns/div _______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables OUT2 HEAVY-LOAD SWITCHING WAVEFORMS MAX8667/88 toc23 70 VOUT3 = 2.80V ILOAD = 100Ω COUT3 = 4.7µF 60 VOUT2 20mV/div MAX8667/88 toc24 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VLX2 2V/div 500mA/div IL2 PSRR (dB) 50 40 30 20 10 500mA LOAD 0 400ns/div 0.01 0.1 1 10 100 1000 FREQUENCY (kHz) OUT3 NOISE OUT4 NOISE MAX8667/88 toc25 MAX8667/88 toc26 100µV/div 100µV/div VOUT3 = 2.80V ILOAD = 100Ω 1ms/div VOUT4 = 3.30V ILOAD = 100Ω 1ms/div _______________________________________________________________________________________ 7 MAX8667/MAX8668 Typical Operating Characteristics (continued) (VIN12 = VIN34 = 3.6V, circuit of Figure 4, VOUT1 = 1.2V, VOUT2 = 1.8V, VOUT3 = 2.8V, VOUT4 = 2.8V, TA = +25°C, unless otherwise noted.) 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables MAX8667/MAX8668 Pin Description PIN 8 NAME FUNCTION MAX8667 MAX8668 1 EN3 EN3 2 OUT3 OUT3 Output of Regulator 3. Bypass OUT3 with a 4.7µF ceramic capacitor to GND. OUT3 is discharged to GND through an internal 1kΩ in shutdown. 3 IN34 IN34 Input Voltage for LDO Regulators 3 and 4. Supply voltage range is from 1.7V to 5.5V. This supply voltage must not exceed VIN12. Connect a 4.7µF or larger ceramic capacitor from IN34 to ground. 4 OUT4 OUT4 Output of Regulator 4. Bypass OUT4 with a 4.7µF ceramic capacitor to GND. OUT4 is discharged to GND through an internal 1kΩ in shutdown. 5 EN4 EN4 Enable Input for Regulator 4. Drive EN4 high or connect to IN34 to turn on regulator 4. Drive low to turn off regulator 4 and reduce input quiescent current. 6 GND GND Ground 7 REF REF Reference Output. Bypass REF with a 0.01µF ceramic capacitor to GND. 8 OUT2 — — FB2 Enable Input for Regulator 3. Drive EN3 high or connect to IN34 to turn on regulator 3. Drive low to turn off regulator 3 and reduce input quiescent current. Feedback Input for Regulator 2. Connect OUT2 directly to the output of step-down regulator 2. Feedback Input for Regulator 2. Connect FB2 to the center of a resistor feedback divider between the output of regulator 2 and ground to set the output voltage. See the Setting the Output Voltages and Voltage Positioning section. 9 PGND2 PGND2 10 LX2 LX2 Inductor Connection for Regulator 2 Power Ground for Step-Down Regulator 2 11 IN12 IN12 Input Voltage for Step-Down Regulators 1 and 2. Supply voltage range is from 2.6V to 5.5V. This supply voltage must not be less than VIN34. Connect a 10µF or larger ceramic capacitor from IN12 to ground. Inductor Connection for Regulator 1 12 LX1 LX1 13 PGND1 PGND1 14 OUT1 — Feedback Input for Regulator 1. Connect OUT1 directly to the output of step-down regulator 1. — FB1 Feedback Input for Regulator 1. Connect FB1 to the center of a resistor feedback divider between the output of regulator 1 and ground to set the output voltage. See the Setting the Output Voltages and Voltage Positioning section. 15 EN1 EN1 Enable Input for Regulator 1. Drive EN1 high or connect to IN12 to turn on step-down regulator 1. Drive low to turn off the regulator and reduce input quiescent current. 16 EN2 EN2 Enable Input for Regulator 2. Drive EN2 high or connect to IN12 to turn on step-down regulator 2. Drive low to turn off the regulator and reduce input quiescent current. — EP EP Power Ground for Step-Down Regulator 1 Exposed Paddle. Connect to GND, PGND1, PGND2, and circuit ground. _______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables MAX8667/MAX8668 IN34 1.7V TO 5.5V IN12 2.8V TO 5.5V (2.6V TO 5.5V) STEP-DOWN IN EN OUT1 LX1 UVLO GND FB EN OUT1 (FB1) PGND1 REF REF AND BIAS STEP-DOWN IN REF EN GND LX2 OUT2 GND FB OUT2 (FB2) PGND2 EN1 EN2 EN3 IN PWRON LOGIC AND ENABLES EN LDO OUT OUT3 OUT OUT4 OUT3 GND EN4 LDO IN EN OUT4 GND () ARE FOR THE MAX8668 Figure 1. Functional Diagram _______________________________________________________________________________________ 9 MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Detailed Description The MAX8667/MAX8668 dual step-down converters with dual low-dropout (LDO) linear regulators are intended to power low-voltage microprocessors or DSPs in portable devices. They feature high efficiency with small external component size. The step-down outputs are adjustable from 0.6V to 3.3V (MAX8668) or factory preset (MAX8667) with guaranteed output current of 600mA for OUT1 and 1200mA for OUT2. The 1.5MHz hysteretic-PWM control scheme allows for tiny external components and reduces no-load operating current to 100µA (typ) with all regulators enabled. Dual, low-quiescent-current, low-noise LDOs operate down to 1.7V supply voltage. The MAX8667/MAX8668 have individual enable inputs for each output to facilitate any supply sequencing. Step-Down DC-DC Regulators (OUT1, OUT2) Step-Down Regulator Architecture The MAX8667/MAX8668 step-down regulators are optimized for high-efficiency voltage conversion over a wide load range, while maintaining excellent transient response, minimizing external component size, and minimizing output voltage ripple. The DC-DC converters (OUT1, OUT2) also feature an optimized on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency. The MAX8667/ MAX8668 utilize a proprietary hysteretic-PWM control scheme that switches with nearly fixed frequency at up to 1.5MHz allowing for ultra-small external components. The step-down converter output current is guaranteed up to 600mA for OUT1 and 1200mA for OUT2. When the step-down converter output voltage falls below the regulation threshold, the error comparator begins a switching cycle by turning the high-side p-channel MOSFET switch on. This switch remains on until the minimum on-time (tON) expires and the output voltage is in regulation or the current-limit threshold (I LIMP_ ) is exceeded. Once off, the high-side switch remains off until the minimum off-time (tOFF) expires and the output voltage again falls below the regulation threshold. During this off period, the low-side synchronous rectifier turns on and remains on until either the high-side switch turns on or the inductor current reduces to the rectifier-off current threshold (ILXOFF = 60mA typ). The internal synchronous rectifier eliminates the need for an external Schottky diode. Input Supply and Undervoltage Lockout The input voltage range of step-down regulators OUT1 and OUT2 is 2.6V to 5.5V. This supply voltage must be greater than or equal to the LDO supply voltage (VIN34). 10 A UVLO circuit prevents step-down regulators OUT1 and OUT2 from switching when the supply voltage is too low to guarantee proper operation. When VIN12 falls below 2.4V (typ), OUT1 and OUT2 are shut down. OUT1 and OUT2 turn on and begin soft-start when VIN12 rises above 2.5V (typ). Soft-Start When initially powered up, or enabled with EN_, the step-down regulators soft-start by gradually ramping up the output voltage. This reduces inrush current during startup. See the startup waveforms in the Typical Operating Characteristics section. Current Limit The MAX8667/MAX8668 limit the peak inductor current of the p-channel MOSFET (ILIMP_). A valley current limit is used to protect the step-down regulators during severe overload and output short-circuit conditions. When the peak current limit is reached, the internal p-channel MOSFET turns off and remains off until the output drops below regulation, the inductor current falls below the valley current-limit threshold, and the minimum off-time has expired. Voltage Positioning The OUT1 and OUT2 output voltages and voltage positioning of the MAX8668 are set by a resistor network connected to FB_. With this configuration, a portion of the feedback signal is sensed on the switched side of the inductor, and the output voltage droops slightly as the load current is increased due to the DC resistance of the inductor. This output voltage droop is known as voltage positioning. Voltage positioning allows the load regulation to be set to match the voltage droop during a load transient, reducing the peak-to-peak output voltage deviation during a load transient, and reducing the output capacitance requirements. Dropout As the input voltage approaches the output voltage, the duty cycle of the p-channel MOSFET reaches 100%. In this state, the p-channel MOSFET is turned on constantly (not switching), and the dropout voltage is the voltage drop due to the output current across the onresistance of the internal p-channel MOSFET (RPCH) and the inductor’s DC resistance (RL): VDO = ILOAD (RPCH + RL ) LDO Linear Regulators (OUT3, OUT4) The MAX8667/MAX8668 contain two low-dropout linear regulators (LDOs), OUT3 and OUT4. The LDO output voltages are factory preset, and each LDO supplies ______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Input Supply and Undervoltage Lockout The input voltage range of LDO regulators OUT3 and OUT4 is 1.7V to 5.5V. This supply voltage must be less than or equal to the voltage applied to IN12 (VIN34 ≤ VIN12). An undervoltage lockout circuit turns off the LDO regulators when the input supply voltage is too low to guarantee proper operation. When VIN34 falls below 1.5V (typ), OUT3 and OUT4 are shut down. OUT3 and OUT4 turn on and begin soft-start when VIN34 rises above 1.6V (typ). Soft-Start When initially powered up, or enabled with EN_, the LDOs soft-start by gradually ramping up the output voltage. This reduces inrush current during startup. The soft-start ramp time is typically 100µs from the start of the soft-start ramp to the output reaching its nominal regulation voltage. Current Limit The OUT3 and OUT4 output current is limited to 375mA (min). If the output current exceeds the current limit, the corresponding LDO output voltage drops. Dropout The maximum dropout voltage for the linear regulators is 250mV at 300mA load. To avoid dropout, make sure the IN34 supply voltage is at least 250mV higher than the highest LDO output voltage. Thermal-Overload Protection Thermal-overload protection limits the total power dissipation in the MAX8667/MAX8668. Thermal-protection circuits monitor the die temperature. If the die temperature exceeds +160°C, the IC is shut down, allowing the IC to cool. Once the IC has cooled by 15°C, the IC is enabled again. This results in a pulsed output during continuous thermal-overload conditions. The thermaloverload protection protects the MAX8667/MAX8668 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction temperature of +150°C. See the Thermal Considerations section for more information. tPWRON IS THE PERIOD REQUIRED TO ENABLE FROM SHUTDOWN IN12 tPWRON ENx OUTx tEN IS THE ENABLE TIME FOR SUBSEQUENT ENABLE SIGNALS FOLLOWING THE FIRST ENABLE ENy tEN OUTy ENx, ENy ARE ANY COMBINATION OF EN1–EN4. Figure 2. Timing Diagram ______________________________________________________________________________________ 11 MAX8667/MAX8668 loads up to 300mA. The LDOs include an internal reference, error amplifier, p-channel pass transistor, and internal voltage-dividers. Each error amplifier compares the reference voltage to the output voltage (divided by the internal voltage-divider) and amplifies the difference. If the divided feedback voltage is lower than the reference voltage, the pass-transistor gate is pulled lower, allowing more current to pass to the outputs and increasing the output voltage. If the divided feedback voltage is too high, the pass-transistor gate is pulled up, allowing less current to pass to the output. MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables C3 4.7µF INPUT 2.8V TO 5.5V 1.7V TO 5.5V C2 10µF IN12 IN34 EN1 EN3 EN2 REF OUT3 EN4 C1 0.01µF 300mA 300mA OUT4 C8 4.7µF GND C9 4.7µF MAX8667 L2 2.2µH OUT2 1.2A L1 2.2µH OUT2 PGND2 C7 2.2µF OUT1 600mA LX1 LX2 OUT1 C6 2.2µF PGND1 Figure 3. MAX8667 Typical Application Circuit INPUT 2.6V TO 5.5V C2 10µF IN12 EN1 IN34 EN3 EN4 EN2 REF OUT4, 300mA OUT4 C1 0.01µF C8 4.7µF GND MAX8668 L2 2.2µH OUT2 0.6V TO 3.3V, 1.2A OUT3, 300mA OUT3 LX2 L1 2.2µH R3 R1 R6* FB2 C6 2.2µF FB1 C5 C10* OUT1 0.6V TO 3.3V, 600mA LX1 R5* C7 2.2µF for VOUT2 ≤ 1.8V 4.7µF for VOUT2 > 1.8V C9 4.7µF C4 R4 PGND1 PGND2 R2 *C10, R5, AND R6 ARE OPTIONAL Figure 4. MAX8668 Typical Application Circuit 12 ______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Setting the Output Voltages and Voltage Positioning L1 The LDO output voltages of the MAX8667/MAX8668, and the step-down outputs of the MAX8667 are factory preset. See the Selector Guide to find the part number corresponding to the desired output voltages. The OUT1 and OUT2 output voltages of the MAX8668 are set by a resistor network connected to FB_ as shown in Figure 5. With this configuration, a portion of the feedback signal is sensed on the switched side of the inductor (LX), and the output voltage droops slightly as the load current is increased due to the DC resistance of the inductor (DCR). This allows the load regulation to be set to match the voltage droop during a load transient (voltage positioning), reducing the peakto-peak output-voltage deviation during a load transient, and reducing the output capacitance requirements. For the simplest method of setting the output voltage, R6 is not installed. Choose the value of R2 (a good starting value is 100kΩ), and then calculate the value of R1 as follows: ⎛V ⎞ R1 = R2 × ⎜ OUT − 1⎟ ⎝ VFB ⎠ where VFB is the feedback regulation voltage (0.6V). With the voltage set in this manner, the voltage positioning depends only on the DCR, and the maximum output voltage droop is: ∆VOUT(MAX) = DCR × IOUT(MAX) Setting the Output Voltages with Reduced Voltage Positioning To obtain less voltage positioning than described in the previous section, use the following procedure for setting the output voltages. The OUT1 and OUT2 output voltages and voltage positioning of the MAX8668 are set by a resistor network connected to FB_ as shown in Figure 5. To set the output voltage (VOUT), first select a value for R2 (a good starting value is 100kΩ). Then calculate the value of REQ (the equivalent parallel resistance of R1 and R6) as follows: ⎛V ⎞ REQ = ⎜ OUT − 1⎟ × R2 ⎝ VFB ⎠ where VFB is the feedback-regulation voltage (0.6V). DCR LX_ OUT ESR R1 R6 (OPTIONAL) C4 RLOAD C6 FB_ R2 Figure 5. MAX8668 Feedback Network Calculate the factor m based on the desired load-regulation improvement: m= IOUT(MAX) × DCR ∆VOUT(DESIRED) where IOUT(MAX) is the maximum output current, DCR is the inductor series resistance, and ∆VOUT(DESIRED) is the maximum allowable droop in the output voltage at full load. The calculated value for m must be between 1.1 and 2; m = 2 results in a 2x improvement in load regulation. Now calculate the values of R1 and R6 as follows: R1 = REQ × m R6 = REQ × m m−1 The value of R1 should always be lower than the value of R6. Power-Supply Sequencing The MAX8667/MAX8668 have individual enable inputs for each regulator to allow complete control over the power sequencing. When all EN_ inputs are low, the IC is in low-power shutdown mode, reducing the supply current to less than 1µA. After one of the EN_ inputs asserts high, the corresponding regulator begins softstart after a delay of tEN (see Figure 2). The first output enabled from shutdown mode or initially powering up the IC has a longer delay (tPWRON) as the IC exits the low-power shutdown mode. Inductor Selection The MAX8667/MAX8668 step-down converters operate with inductors between 2.2µH and 4.7µH. Low inductance values are physically smaller, but require faster switching, resulting in some efficiency loss. The inductor’s DC current rating must be high enough to account ______________________________________________________________________________________ 13 MAX8667/MAX8668 Applications Information MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Table 1. Recommended Inductors MANUFACTURER INDUCTOR L (µH) RL (mΩ) FDK MIPF2016 2.2 110 1.1 2.0 x 1.6 x 1.0 FDK MIPF2520D 2.2 80 1.3 2.5 x 2.0 x 1.0 LQH32CN2R2M5 2.2 97 0.79 3.2 x 2.5 x 1.55 3.2 x 1.6 x 0.95 Murata CURRENT RATING (A) L x W x H (mm) LQM31P 2.2 220 0.9 Sumida CDRH2D09 2.2 120 0.44 3.2 x 3.2 x 1.0 TDK GLF251812T 2.2 200 0.6 2.5 x 1.8 x 1.35 TOKO D2812C 2.2 140 0.77 2.8 x 2.8 x 1.2 TOKO MDT2520-CR 2.2 80 0.7 2.5 x 2.0 x 1.0 TPC Series 2.2 55 1.8 4.0 x 4.0 x 1.1 TPC Series 4.7 124 1.35 4.0 x 4.0 x 1.1 CB2518T 2.2 90 0.51 2.5 x 1.8 x 2.0 Wurth Taiyo Yuden for peak ripple current and load transients. The stepdown converter’s unique architecture has minimal current overshoot during startup and load transients and in most cases, an inductor capable of 1.3x the maximum load current is acceptable. For output voltages above 2V, when light-load efficiency is important, the minimum recommended inductor is 2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 200mA) and minimal load regulation, keep the inductor resistance as small as possible. For light-load applications (up to 200mA), higher resistance is acceptable with very little impact on performance. small and to ensure regulation loop stability. These capacitors must have low impedance at the switching frequency. Surface-mount ceramic capacitors are a good choice due to their small size and low ESR. Make sure the capacitor maintains its capacitance over temperature and DC bias. Ceramic capacitors with X5R or X7R temperature characteristics generally perform well. The output capacitance can be very low. For most applications, a 2.2µF ceramic capacitor is sufficient. For C7 of the MAX8668, a 2.2µF (VOUT2 ≤ 1.8V) or a 4.7µF (VOUT2 > 1.8V) ceramic capacitor is recommended. For optimum load-transient performance and very low output ripple, the output capacitor value in µF should be equal to or greater than the inductor value in µH. Capacitor Selection Feed-Forward Capacitor The feed-forward capacitors on the MAX8668 (C4 and C5 in Figure 4) set the feedback loop response, control the switching frequency, and are critical in obtaining the best efficiency possible. Small X7R and C0G ceramic capacitors are recommended. For OUT1, calculate the value of C4 as follows: C4 = 1.2 x 10-5(s/V) x (VOUT / R1) For OUT2, calculate the value of C5 and C10 as follows: Cff = 1.2 x 10-5(s/V) x (VOUT / R3) Cff = C5 + (C10 / 2) (C10 / C5) + 1 = (VOUT / VFB), where VFB is 0.6V. Rearranging the formulas: C10 = 2 x Cff x (VOUT - VFB)/(VOUT + VFB) C5 = Cff – (C10 / 2) Input Capacitors The input capacitor for the step-down converters (C2 in Figures 3 and 4) reduces the current peaks drawn from the battery or input power source and reduces switching noise in the IC. The impedance of C2 at the switching frequency should be very low. Surface-mount ceramic capacitors are a good choice due to their small size and low ESR. Make sure the capacitor maintains its capacitance over temperature and DC bias. Ceramic capacitors with X5R or X7R temperature characteristics generally perform well. A 10µF ceramic capacitor is recommended. A 4.7µF ceramic capacitor is recommended for the LDO input capacitor (C3 in Figure 3). Step-Down Output Capacitors The step-down output capacitors (C6 and C7 in Figures 3 and 4) are required to keep the output-voltage ripple 14 ______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables LDO Output Capacitor and Stability Connect a 4.7µF ceramic capacitor between OUT3 and GND, and a second 4.7µF ceramic capacitor from OUT4 to GND. For a constant loading above 10mA, the output capacitors can be reduced to 2.2µF. The equivalent series resistance (ESR) of the LDO output capacitors affects stability and output noise. Use output capacitors with an ESR of 0.1Ω or less to ensure stable operation and optimum transient response. Surfacemount ceramic capacitors have very low ESR and are commonly available. Connect these capacitors as close as possible to the IC’s pins to minimize PCB trace inductance. Thermal Considerations The maximum package power dissipation of the MAX8667/MAX8668 is 1667mW. Make sure the power dissipated by the MAX8667/MAX8668 does not exceed this rating. The total IC power dissipation is the sum of the power dissipation of the four regulators: PD = PD1 + PD2 + PD3 + PD4 Estimate the OUT1 and OUT2 power dissipations as follows: PD1 = IOUT1 × VOUT1 × 1− η η PD2 = IOUT2 × VOUT2 × 1− η η where RL is the inductor’s DC resistance, and η is the efficiency (see the Typical Operating Characteristics section). Calculate the OUT3 and OUT4 power dissipations as follows: PD3 = IOUT3 × (VIN34 − VOUT3 ) PD4 = IOUT4 × (VIN34 − VOUT4 ) The maximum junction temperature of the MAX8667/ MAX8668 is +150°C. The junction-to-case thermal resistance (θJC) of the MAX8667/MAX8668 is 6.9°C/W. When mounted on a single-layer PCB, the junction to ambient thermal resistance (θ JA ) is about 64°C/W. Mounted on a multilayer PCB, θJA is about 48°C/W. Calculate the junction temperature of the MAX8667/MAX8668 as follows: TJ = TA + PD × θJA where TA is the maximum ambient temperature. Make sure the calculated value of TJ does not exceed the +150°C maximum. PCB Layout High switching frequencies and relatively large peak currents make PCB layout a very important aspect of design. Good design minimizes excessive EMI on the feedback paths and voltage gradients in the ground plane, both of which can result in instability or regulation errors. Connect the input capacitors as close as possible to the IN_ and PGND_ pins. Connect the inductor and output capacitors as close as possible to the IC and keep the traces short, direct, and wide. The feedback network traces are sensitive to inductor magnetic field interference. Route these traces away from the inductors and noisy traces such as LX. Keep the feedback components close to the FB_ pin. Connect GND and PGND_ to the ground plane. Connect the exposed paddle to the ground plane with one or more vias to help conduct heat away from the IC. Refer to the MAX8668 evaluation kit for a PCB layout example. ______________________________________________________________________________________ 15 MAX8667/MAX8668 C10 is needed if VOUT > 1.5V or VIN12 can be less than VOUT / 0.65. MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Ordering Information (continued) PART PKG CODE TOP MARK MAX8667ETEHR+ T1633-4 AFJ MAX8667ETEJS+ T1633-4 MAX8668ETEA+ T1633-4 MAX8668ETEP+ Selector Guide PART OUT1 (V) OUT2 (V) OUT3 (V) OUT4 (V) AFQ MAX8667ETEAA+ 1.20 1.80 2.80 2.80 AER MAX8667ETEAB+ 1.20 1.80 2.85 2.85 T1633-4 AFK MAX8667ETEAC+ 1.20 1.80 1.20 1.20 MAX8668ETEQ+ T1633-4 AFR MAX8667ETECQ+ 1.60 1.80 2.80 1.20 MAX8668ETET+ T1633-4 AFS MAX8667ETEHR+ 1.80 1.20 2.60 2.80 MAX8668ETEU+ T1633-4 AFL MAX8667ETEJS+ 1.30 1.30 3.30 2.70 MAX8668ETEV+ T1633-4 AFT MAX8668ETEA+ ADJ ADJ 2.80 2.80 MAX8668ETEW+ T1633-4 AFU MAX8668ETEP+ ADJ ADJ 3.30 1.80 MAX8668ETEX+ T1633-4 AFV MAX8668ETEQ+ ADJ ADJ 2.80 1.20 MAX8668ETET+ ADJ ADJ 3.30 3.30 MAX8668ETEU+ ADJ ADJ 3.30 2.80 MAX8668ETEV+ ADJ ADJ 3.30 2.50 All MAX8667/MAX8668 parts are in a 16-pin, thin QFN, 3mm x 3mm package and operate in the -40°C to = +85°C extended temperature range. +Denotes a lead-free package. MAX8668ETEW+ ADJ ADJ 3.30 3.00 MAX8668ETEX+ ADJ ADJ 2.80 1.80 Chip Information PROCESS: BiCMOS 16 ______________________________________________________________________________________ 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables 12x16L QFN THIN.EPS (NE - 1) X e E MARKING E/2 D2/2 (ND - 1) X e D/2 AAAA e CL D D2 k CL b 0.10 M C A B E2/2 L E2 0.10 C C L 0.08 C C L A A2 A1 L L e e PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 I 1 2 ______________________________________________________________________________________ 17 MAX8667/MAX8668 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) MAX8667/MAX8668 1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual Enables Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) PKG 8L 3x3 12L 3x3 REF. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 b 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 D 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 E 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 e L 0.65 BSC. 0.35 0.55 16L 3x3 0.50 BSC. 0.50 BSC. 0.75 0.45 0.55 0.65 0.30 0.40 N 8 12 16 ND 2 3 4 NE 2 3 4 0 A1 A2 k 0.02 0.05 0 0.25 - 0.02 0.05 0 0.20 REF 0.20 REF - 0.25 - EXPOSED PAD VARIATIONS 0.02 0.50 0.05 0.20 REF - 0.25 - PKG. CODES TQ833-1 E2 D2 PIN ID MIN. NOM. MAX. MIN. NOM. MAX. 0.25 0.70 1.25 0.25 0.70 1.25 0.35 x 45° JEDEC WEEC T1233-1 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-1 T1233-3 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-1 T1233-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-1 T1633-2 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 T1633F-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45° WEED-2 T1633FH-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45° WEED-2 T1633-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 T1633-5 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45° WEED-2 - NOTES: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. N IS THE TOTAL NUMBER OF TERMINALS. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm FROM TERMINAL TIP. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. DRAWING CONFORMS TO JEDEC MO220 REVISION C. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. WARPAGE NOT TO EXCEED 0.10mm. PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 I 2 2 Revision History Pages changed at Rev 1: 1, 12, 14, 18 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. 18 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products. Inc.