LTC3446IDE-TRPBF

LTC3446 Monolithic Buck Regulator with Dual VLDO Regulators FEATURES n n DESCRIPTION The LTC®3446 combines a synchronous buck DC/DC converter with two very low dropout (VLDO) linear regulators to provide up to three stepped-down output voltages from a single input voltage. The input voltage range is ideally suited for Li-Ion battery-powered applications, as well as powering low voltage logic from 5V or 3.3V rails. The output voltage range extends down to 0.4V for the VLDO regulators and 0.8V for the buck. The 1A synchronous buck converter provides the main output with high efficiency, typically 85%. The two 300mA VLDO regulators can run off the main output to provide two additional lower voltage outputs. A built-in supply monitor provides a power good indication. The buck converter switches at 2.25MHz, allowing the use of small surface mount inductors and capacitors. Constant frequency current mode operation produces controlled output spectrum and fast transient response. A modeselect pin allows automatic Burst Mode operation to be enabled for higher efficiency at light load, or disabled for lower noise operation down to very light loads. The two VLDO regulators are stable with ceramic output capacitors as small as 1μF . L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. VLDO is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6611131, 6304066, 6498466, 6580258. n n n n n n n n n n n n High Efficiency Triple Step-Down Outputs from a Single Input Supply 1A Synchronous Buck Regulator Provides Main Step-Down Output and Powers Two 300mA VLDO™ Linear Regulators Output Voltages as Low as 400mV (VLDO Outputs) Power Good Output Input Voltage Range: 2.7V to 5.5V Independent Internal Soft-Start for Each Supply Independent Enable Pin for Each Supply Low (140μA Typ) No-Load Quiescent Current with all Outputs Enabled Constant Frequency Current Mode Operation 2.25MHz Switching Frequency Uses Small Inductors Defeatable Automatic Burst Mode® Operation for High Efficiency at Light Loads ±1.5% Reference Accuracy Overtemperature Protection Thermally Enhanced 4mm × 3mm 14-Pin DFN Package APPLICATIONS n n Low Power Handheld Devices Low Voltage and Multivoltage Power for Digital Logic, I/O, FPGAs, CPLDs, ASICs and CPUs TYPICAL APPLICATION L1 1.8μH VIN 2.9V TO 5.5V 22μF X7R VIN SW 59k BUCKFB LTC3446 LVIN PGOOD LVOUT1 MODESEL ENBUCK ENLDO1 LVFB1 ENLDO2 3.3k ITH 1000pF LVFB2 GND 3446 TA01 22μF X7R VOUT 1.8V 400mA MAX Buck Efficiency vs Buck Load Current 100 90 EFFICIENCY (%) 80 70 60 50 40 VIN = 2.7V VIN = 3.6V VIN = 4.2V 1 10 100 LOAD CURRENT (mA) 1000 3446 TA01b 47.5k VOUT 1.5V 300mA MAX Burst Mode OPERATION PWM MODE DIGITAL CONTROL 110k 2.2μF X7R 40.2k VOUT 1.2V 300mA MAX LVOUT2 80.6k 2.2μF X7R 40.2k L1: TOKO A960AW-1R8M 3446fd 1 LTC3446 ABSOLUTE MAXIMUM RATINGS (Note 1) PIN CONFIGURATION TOP VIEW MODESEL VIN ITH PGOOD LVOUT1 LVIN LVOUT2 1 2 3 4 5 6 7 15 14 SW 13 ENBUCK 12 BUCKFB 11 ENLDO1 10 LVFB1 9 LVFB2 8 ENLDO2 VIN, LVIN to GND ......................................... – 0.3V to 6V MODESEL, ENBUCK, ENLDO1, ENLDO2 to GND .......................................... –0.3V to 6V BUCKFB to GND .......................................... –0.3V to 6V LVFB1, LVFB2 to GND .................................... –0.3V to 6V ITH to GND ..... –0.3V to the Lesser of (VIN + 0.3V) or 3V SW to GND......–0.3V to the Lesser of (VIN + 0.3V) or 6V LVOUT1, LVOUT2 to GND .......... –0.3V to the Lesser of (LVIN + 0.3V) or 6V PGOOD to GND ............................................ –0.3V to 6V LVOUT1, LVOUT2 Short-Circuit to GND Duration............................................... Indefinite Operating Temperature Range (Note 2) LTC3446EDE ........................................ –40°C to 85°C LTC3446IDE ....................................... –40°C to 125°C Junction Temperature (Note 1) ........................... 125°C Storage Temperature Range.................. –65°C to 125°C DE PACKAGE 14-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 35°C/W EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LTC3446EDE#PBF LTC3446IDE#PBF TAPE AND REEL LTC3446EDE#TRPBF LTC3446IDE#TRPBF PART MARKING* 3446 3446 PACKAGE DESCRIPTION 14-Lead (4mm × 3mm) Plastic DFN 14-Lead (4mm × 3mm) Plastic DFN TEMPERATURE RANGE –40°C to 85°C –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V unless otherwise specified. (Note 2) SYMBOL VIN VUVLO IQ PARAMETER Input Voltage Range VIN Undervoltage Lockout Threshold VIN Undervoltage Lockout Hysteresis VIN Quiescent Current (Note 4) Buck Enabled Only, Not Sleeping Buck Enabled Only, Sleeping One LDO Enabled Only All Three Outputs Enabled, Buck Not Sleeping All Three Outputs Enabled, Buck Sleeping Shutdown CONDITIONS (Note 3) VIN Rising ● ● ELECTRICAL CHARACTERISTICS MIN 2.7 TYP 2.37 10 310 50 75 400 140 MAX 5.5 2.5 30 500 75 100 600 210 1 UNITS V V mV μA μA μA μA μA μA 3446fd VBUCKFB = 0V, ISW = 0mA VBUCKFB = 1V, ISW = 0mA VLVIN = 1.5V, 10μA LDO Output Load VBUCKFB = 0V, ISW = 0mA, VLVIN = 1.5V, 10μA Output Load on Each LDO VBUCKFB = 1V, ISW = 0mA, VLVIN = 1.5V, 10μA Load on Each LDO VENBUCK = 0V, VENLDO1 = 0V, VENLDO2 = 0V 2 LTC3446 ELECTRICAL CHARACTERISTICS SYMBOL RPGOOD IPGOOD IBUCKFB VBUCKFB ΔVBUCKFB IMAXP IMAXN PARAMETER PGOOD Output Resistance PGOOD Hi-Z Leakage Current Feedback Current Regulated Feedback Voltage Feedback Voltage Line Regulation Maximum Peak Inductor Current NMOS Overcurrent Limit Feedback Voltage Load Regulation (with Respect to VITH) fOSC RPFET RNFET ILSW VENBUCK IENBUCK VMODESEL IMODESEL gm VLVIN ILVIN VLVFB ILVFB ILVOUT(MAX) VENLDOx IENLDOx Oscillator Frequency RDS(ON) of P-Channel FET RDS(ON) of N-Channel FET SW Leakage Buck Enable Pin Threshold Buck Enable Pin Leakage Current Mode Select Pin Threshold Mode Select Pin Leakage Current Error Amplifier Transconductance LVIN Pin Operating Voltage LVIN Pin Operating Current LVIN Shutdown Current Feedback Pin Regulation Voltage (Note 7) Feedback Pin Input Current Continuous Output Current Short-Circuit Output Current LDO Enable Pin Threshold LDO Enable Pin Leakage Current Output Voltage Load Regulation (Referred to the LVFB Pin) LVFB Line Regulation (with Respect to the LVIN Pin) LVFB Line Regulation (with Respect to the VIN Pin) VDO LVIN – LVOUT Dropout Voltage VENLDOx = 5.5V, All Other Pins Grounded ΔIOUT = 1mA to 300mA VLVIN = 1.5V to 5.5V, VIN = 3.6V, VLVOUT = 1.2V, IOUT = 1mA VLVIN = 1.5V, VIN = 2.7V to 5.5V, VLVOUT = 1.2V, IOUT = 1mA VIN = 2.8V, VLVIN = 1.5V, VLVFB = 0.37V, IOUT = 300mA (Note 9) ● ● The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V unless otherwise specified. (Note 2) CONDITIONS ● MIN ● ● ● ● ● TYP 8 87 MAX 10 120 1 ±30 UNITS % Ω μA nA V mV/V A A mV/V VPG(THRESH) PGOOD Threshold (Note 8) PGOOD Low, Sinking 1mA VPGOOD = 6V (Note 5) (Note 5) VIN = 2.7V to 5.5V (Note 5) VBUCKFB = 0V, Duty Cycle < 35% VITH = 0.5V to 1V, VMODESEL = VIN (Note 5) Synchronous Buck Converter 0.788 1.2 0.800 0.3 1.55 1.8 0.5 ● 0.812 0.5 2.0 1.8 2.25 0.13 0.14 2.7 MHz Ω Ω ISW = 500mA ISW = – 500mA VENBUCK = 0V, VSW = 0V or 5.5V, VIN = 5.5V ● ±1 0.3 0.3 450 ● ● μA V μA V μA μA/V V μA μA V V nA mA mA 0.65 0.65 700 1 1 1 1 950 5.5 VENBUCK = 5.5V, All Other Pins Grounded VMODESEL = 5.5V, All Other Pins Grounded VITH = 0.6V (Note 6) IOUT = 10μA VENLDO = 0V 1mA ≤ IOUT ≤ 300mA, 1.5V ≤ VLVIN ≤ 5.5V VLVFB at Regulation ● ● ● Each VLDO: VIN = 3.6V, VLVIN = 1.5V, VLVOUT = 1.2V, Unless Otherwise Specified 0.9 3 1.5 ● ● ● 20 2 0.405 0.408 ±10 0.395 0.392 300 0.400 0.400 2 760 0.3 0.65 –1 7.5 0.44 68 1 1 V μA mV/A μV/V mV/V 175 mV 3446fd 3 LTC3446 ELECTRICAL CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC3446E is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the – 40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3446I is guaranteed to meet performance specifications over the –40°C to 125°C operating temperature range. Note 3: Minimum operating VIN voltage required for the VLDO regulators to stay in regulation is: VIN ≥ LVOUT(MAX) + 1.4V and VIN ≥ 2.7V Note 4: Dynamic supply current is higher due to the internal gate charge being delivered at the switching frequency. Note 5: The LTC3446 is tested in a feedback loop that connects the BUCKFB pin to the output of the buck converter’s error amplifier (i.e., the ITH pin). Note 6: Minimum operating LVIN voltage required for the VLDO regulators to stay in regulation is: LVIN ≥ LVOUT(MAX) + 100mV and LVIN ≥ 0.9V Note 7: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current, the input voltage range must be limited. Note 8: PGOOD assertion indicates that the feedback voltages of all enabled supplies are within the specified percentage of their target values. Note 9: Dropout voltage in the DFN package is assured by design, characterization and statistical process control. 3446fd 4 LTC3446 TYPICAL PERFORMANCE CHARACTERISTICS Buck Regulated Feedback Voltage vs Temperature 808 806 804 VBUCKFB (mV) VLVFB1 (mV) VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V 802 800 798 796 794 408 406 404 402 400 398 396 394 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V LDO1 Regulated Feedback Voltage vs Temperature 792 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G01 392 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G02 LDO2 Regulated Feedback Voltage vs Temperature 408 406 404 VLVFB2 (mV) 402 400 398 396 394 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V 2.50 2.45 2.40 2.35 VIN (V) 2.30 2.25 2.20 2.15 2.10 2.05 Undervoltage Lockout Threshold vs Temperature UVLO RISING UVLO FALLING 392 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G03 2.00 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G04 Maximum Peak Inductor Current 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 –50 –30 2.50 2.45 OSCILLATOR FREQUENCY (MHz) 2.40 2.35 2.30 2.25 2.20 2.15 2.10 2.05 Oscillator Frequency vs Temperature CURRENT (A) VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G05 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V 2.00 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 3446 G06 3446fd 5 LTC3446 TYPICAL PERFORMANCE CHARACTERISTICS Peak Inductor Current vs ITH Voltage 1.6 PEAK INDUCTOR CURRENT (A) VIN = 3.6V 1.4 VMODESEL = 3.6V VLDO CURRENT LIMIT (mA) 1800 1600 1400 1200 1000 800 600 400 200 0 0.25 0.5 0.75 1 1.25 1.5 1.75 ITH PIN VOLTAGE (V) 2 0 0.00 1.00 2.00 3.00 4.00 LVIN PIN VOLTAGE (V) 5.00 6.00 PULSED MEASUREMENT, TJ ≈ TA ≈ 27°C VIN = 3.6V LVOUT = 0V VLDO Current Limit vs LVIN Voltage 1.2 1.0 0.8 0.6 0.4 0.2 0 3446 G07 3446 G08 VLDO Dropout Voltage vs Load Current 100 VIN = 2.8V 90 LVOUT = 1.2V –45°C 80 27°C 90°C 70 130°C 60 50 40 30 20 10 0 0 50 150 200 100 LOAD CURRENT (mA) 250 300 450 400 350 VIN CURRENT (μA) 300 250 200 150 100 50 0 VIN Bias Current vs VLDO Load Current DROPOUT VOLTAGE (mV) VIN = 3.6V LVIN = 1.5V LVOUT = 1.2V ONLY ONE VLDO ENABLED –45°C 27°C 90°C 130°C 0 100 150 50 250 200 VLDO OUTPUT CURRENT (mA) 300 3446 G10 3446 G09 LVIN No-Load Operating Current 20 18 16 LVIN CURRENT (μA) 14 12 10 8 6 4 2 0 0 1 3 4 LVIN PIN VOLTAGE (V) 2 –45°C 27°C 90°C 130°C 5 6 3446 G11 Enable/MODESEL Thresholds 1000 ENABLE/MODESEL THRESHOLD (mV) 900 800 700 600 500 400 300 200 100 0 2.5 3 3.5 4 VIN (V) 4.5 –45°C 27°C 90°C 130°C 5 5.5 3446 G12 VIN = 5V BOTH VLDOS ON AND REGULATING 0.8V 3446fd 6 LTC3446 TYPICAL PERFORMANCE CHARACTERISTICS Buck PMOS Switch On-Resistance 200 180 160 140 120 100 80 –45 –20 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V 55 30 80 5 TEMPERATURE (°C) 105 130 NMOS RESISTANCE (mΩ) PMOS RESISTANCE (mΩ) 200 180 160 140 120 100 80 –45 –20 VIN = 2.7V VIN = 3.6V VIN = 4.2V VIN = 5.5V 55 30 80 5 TEMPERATURE (°C) 105 130 Buck NMOS Switch On-Resistance 3446 G17 3446 G18 Buck Transient Response with Burst Mode Defeated Buck Transient Response with Burst Mode Enabled BUCK OUTPUT VOLTAGE 50mV/DIV AC-COUPLED 500mA LOAD CURRENT 50mA 100μs/DIV FRONT PAGE APPLICATION CIRCUIT 3446 G13 BUCK OUTPUT VOLTAGE 50mV/DIV AC-COUPLED 500mA LOAD CURRENT 50mA 100μs/DIV FRONT PAGE APPLICATION CIRCUIT 3446 G14 VLDO Transient Response VLVIN = BUCK VOUT 20mV/DIV AC-COUPLED VLVOUT 10mV/DIV AC-COUPLED VLDO Rejection of Buck DC/DC Burst Mode Ripple VLDO OUTPUT VOLTAGE 20mV/DIV AC-COUPLED 300mA LOAD CURRENT 30mA 100μs/DIV LVOUT = 1.5V OR 1.2V FRONT PAGE APPLICATION CIRCUIT 3446 G15 2μs/DIV VLVIN = BUCK VOUT = 1.8V VIN = 4.2V VLVOUT = 1.5V ILVOUT = 50mA CLVOUT = 2.2μF 3446 G16 3446fd 7 LTC3446 PIN FUNCTIONS MODESEL (Pin 1): Chooses Between Burst Mode Operation and Pulse Skipping Operation at Light Loads. Forcing this pin below 0.3V allows the buck converter to automatically enter Burst Mode operation at light loads. Forcing this pin above 1V disallows entering Burst Mode operation; the buck converter will cycle skip at light loads. Do not leave this pin floating. This is a MOS gate input. VIN (Pin 2): Input Supply to the LTC3446. Must be closely decoupled to GND with a 10μF or greater ceramic capacitor. ITH (Pin 3): Buck Error Amplifier Output and Servo-Loop Compensation Point. PGOOD (Pin 4): Supply Monitor Output, Open-Drain NMOS. LVOUT1 (Pin 5): Output of the First VLDO Regulator. LVIN (Pin 6): Input Supply to the LTC3446’s VLDO Circuits. Bypass LVIN to GND with at least a 1μF low ESR ceramic capacitor. Typical LTC3446 application circuits will connect this pin to the output of the buck converter but this is not required. The VLDO regulators may be used independently of the buck converter. LVOUT2 (Pin 7): Output of the Second VLDO Regulator. LVFB2 (Pin 9): Feedback Pin for the Second VLDO Regulator. An output divider should be connected from LVOUT2 to LVFB2 to set the desired LVOUT2 regulated output voltage. LVFB1 (Pin 10): Feedback Pin for the First VLDO Regulator. An output divider should be connected from LVOUT1 to LVFB1 to set the desired LVOUT1 regulated output voltage. ENLDO1/ENLDO2 (Pin 11/Pin 8): Enable Pin for the First and Second VLDO Regulators, Respectively. Forcing this pin above 1V enables the corresponding VLDO regulator and forcing this pin below 0.3V shuts it down. Each VLDO regulator draws