LM2772SD

LM2772 Low-Ripple Switched Capacitor Step-Down Regulator December 2006 LM2772 Low-Ripple Switched Capacitor Step-Down Regulator General Description The LM2772 is a switched capacitor step-down regulator that produces a 1.2V output. It is capable of supplying loads up to 150mA with 3% output voltage regulation over line, load, and temperature. The LM2772 operates with an input voltage from 3.0V to 5.5V, accommodating 1-cell Li-Ion batteries and chargers. The LM2772 utilizes a highly efficient regulated multi-gain charge pump. Pre-regulated 1.1MHz fixed-frequency switching results in very low ripple and noise on both the input and the output. When output currents are low, the part automatically switches to a low-ripple PFM regulation mode to maintain high efficiency over the entire load range. The LM2772 is available in National’s 10-pad Leadless Leadframe No-Pullback Package (LLP-10). Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Low-Noise Fixed Frequency Operation 1.2V Output Voltage 3% Output Voltage Regulation Li-Ion (3.6V) to 1.2V with 80% Efficiency Very Low Output Ripple: 8mV @ 150mA Output Currents up to 150mA 2.7V to 5.5V Input Voltage Range Shutdown Disconnects Load from VIN 1.1MHz Switching Frequency No Inductors…Small Solution Size Short Circuit and Thermal Protection LLP-10 Package (3mm × 3mm × 0.8mm) Applications ■ DSP, Memory, and Microprocessor Power Supplies ■ Mobile Phones and Pagers ■ Portable Electronic Devices Typical Application Circuit LM2772 Efficiency vs. Low-Dropout Linear Regulator (LDO) Efficiency 20216401 20216413 © 2007 National Semiconductor Corporation 202164 www.national.com LM2772 Connection Diagram and Package Mark Information 10-Pin Non-Pullback Leadless Frame Package (LLP-10) National Semiconductor Package Number SDA10A   20216402 Pin Descriptions Pin # 1 2 3 4 5 6 7 8 9 10 Name VIN GND VOUT C3C3+ C2C2+ C1C1+ EN Ground Output Voltage Flying Capacitor 3: Negative Terminal Flying Capacitor 3: Positive Terminal Flying Capacitor 2: Negative Terminal Flying Capacitor 2: Positive Terminal Flying Capacitor 1: Negative Terminal Flying Capacitor 1: Positive Terminal Enable Pin Logic Input. Applying a logic HIGH voltage signal enables the part. A logic LOW voltage signal places the the device in shutdown. Description Input Voltage: Recommended VIN operating range 3.0V to 5.5V. Order Information Output Voltages 1.2V 1.2V Order Number LM2772SD LM2772SDX Package Mark ID XXXXX = ¢Z¢2¢X YYYYY = L2772 XXXXX = ¢Z¢2¢X YYYYY = L2772 Package SDA10A Non-Pullback LLP Supplied as: 1000 Units, Tape and Reel 4500 Units, Tape and Reel www.national.com 2 LM2772 Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN Pin Voltage EN Pin Voltage Continuous Power Dissipation (Note 3) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Note 4) ESD Rating (Note 5) Human Body Model: -0.3V to 6.0V -0.3V to (VIN+0.3V) w/ 6.0V max Internally Limited 150ºC -65ºC to +150º C 265ºC   2.0kV (Notes 2, 8) Operating Ratings (Notes 1, 2) Input Voltage Range Recommended Load Current Range Junction Temperature (TJ) Range Ambient Temperature (TA) Range (Note 6) 2.7V to 5.5V 0mA to 150mA -30°C to +110°C -30°C to +85°C Thermal Properties Junction-to-Ambient Thermal Resistance (θJA), LLP10 Package (Note 7) 55°C/W Electrical Characteristics Limits in standard typeface are for TJ = 25ºC. Limits in boldface type apply over the full operating junction temperature range (-30° C ≤ TJ ≤ +110°C) . Unless otherwise noted, specifications apply to the LM2772 Typical Application Circuit (pg. 1) with: VIN = 3.6V; V(EN) = 1.8V, CIN = C1 = C2 = C3 = 1.0µF, COUT = 4.7µF. (Note 9) Symbol Parameter Condition 3.0V ≤ VIN ≤ 5.5V VOUT 1.2V Output Voltage Regulation 0mA ≤ IOUT ≤ 150mA Min 1.164 (−3%) 1.178 (−1.8%) Typ 1.2 1.2 0.15 0.2 IOUT = 150mA IOUT = 0mA (Note 10) 40mA ≤ IOUT ≤ 150mA IOUT < 40mA V(EN) = 0V 3.0V ≤ VIN ≤ 5.5V VIN = 5.5V 0V ≤ VOUT ≤ 0.2V 3.0V ≤ VIN ≤ 5.5V 3.0V ≤ VIN ≤ 5.5V V(EN) = 1.8V (Note 11) Logic Input = 0V 0 1.1 5 0.01 0.80 80 47 8 12 0.01 1.15 500 150 0.63 VIN 0.3 1.50 50 Max 1.236 (+3%) 1.236 (+3.0%) mV/mA %/V % µA mV mV µA MHz mA µs V V µA µA Units V 0mA ≤ IOUT ≤ 150mA VOUT/IOUT VOUT/VIN E IQ VR VR–PFM ISD FSW ICL tON VIL VIH IIH IIL Output Load Regulation Output Line Regulation Power Efficiency Quiescent Supply Current Fixed Frequency Output Ripple PFM–Mode Output Ripple Shutdown Current Switching Frequency Output Current Limit Turn-on Time Logic-low Input Voltage Logic-high Input Voltage Logic-high Input Current Logic-low Input Current 0mA ≤ IOUT ≤ 150mA Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 2: All voltages are with respect to the potential at the GND pins. Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150ºC (typ.) and disengages at TJ=140ºC (typ.). Note 4: For detailed information on soldering requirements and recommendations, please refer to National Semiconductor's Application Note 1187 (AN-1187): Leadless Leadframe Package (LLP). Note 5: The Human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. MIL-STD-883 3015.7 Note 6: Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 110ºC), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). 3 www.national.com LM2772 Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues. Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm. Note 9: CIN, COUT, C1, C2, C3: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics. Note 10: VOUT is set to 1.3V during this test (Device is not switching). Note 11: There is a 350kΩ pull-down resistor connected internally between the EN pin and GND. Block Diagram 20216403 www.national.com 4 LM2772 Typical Performance Characteristics Unless otherwise specified: VIN = 3.6V, CIN = C1 = C2 = C3 = 1.0µF, COUT = 4.7µF, TA = 25ºC. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's). Output Voltage vs. Input Voltage Output Voltage vs. Output Current 20216412 20216414 Efficiency vs. Input Voltage Operating Supply Current 20216413 20216426 5 www.national.com LM2772 Input and Output Voltage Ripple, Load = 150mA Load Step 10mA to 150mA, VIN = 3.6V 20216415 20216423 CH1: VIN, Scale: 50mV/Div, AC Coupled CH3: VOUT, Scale: 10mV/Div, AC Coupled Time scale: 1µs/Div CH3: VOUT; Scale: 50mV/Div, AC Coupled CH4: IOUT; Scale: 100mA/Div Time scale: 40µs/Div Load Step 10mA to 150mA, VIN = 4.7V Line Step 3.5V to 4.0V with Load = 150mA 20216424 20216421 CH3: VOUT; Scale: 50mV/Div, AC Coupled CH4: IOUT; Scale: 100mA/Div Time scale: 40µs/Div CH2: VIN; Scale: 1V/Div, DC Coupled CH3: VOUT; Scale: 20mV/Div, AC Coupled Time scale: 400µs/Div Line Step 4.0V to 3.5V with Load = 150mA Oscillator Frequency vs. Input Voltage 20216422 CH2: VIN; Scale: 1V/Div, DC Coupled CH3: VOUT; Scale: 20mV/Div, AC Coupled Time scale: 400µs/Div 20216425 www.national.com 6 LM2772 Startup Behavior, Load = 150mA 20216416 CH1: VOUT; Scale: 200mV/Div, DC Coupled Time scale: 20µs/Div 7 www.national.com LM2772 Operation Description OVERVIEW The LM2772 is a switched capacitor converter that produces a regulated, low voltage output. The core of the part is a highly efficient charge pump that utilizes fixed frequency pre-regulation and Pulse Frequency Modulation to minimize ripple and power losses over wide input voltage and output current ranges. A description of the principal operational characteristics of the LM2772 is detailed in the Circuit Description, and Efficiency Performance sections. These sections refer to details in the Block Diagram. CIRCUIT DESCRIPTION The core of the LM2772 is a two-phase charge pump controlled by an internally generated non-overlapping clock. The charge pump operates by using external flying capacitors C1, C2, and C3 to transfer charge from the input to the output. At input voltages below 3.5V (typ.) the LM2772 operates in a 1/2x Gain, with the input current being equal to 1/2 of the load current. At input voltages between 3.5V to 4.6V(typ.) the part utilizes a gain of 2/5x, resulting in an input current equal to 2/5 times the load current. At input voltages above 4.6V (typ.), the part is in a gain of 1/3, with the input current being 1/3 of the load current. The two phases of the switched capacitor switching cycle will be referred to as the "charge phase" and the "discharge phase". During the charge phase, the flying capacitor is charged by the input supply. After half of the switching cycle [ t = 1/(2×FSW) ], the LM2772 switches to the discharge phase. In this configuration, the charge that was stored on the flying capacitors in the charge phase is transferred to the output. The LM2772 uses fixed frequency pre-regulation to regulate the output voltage to 1.2V during moderate to high load currents. The input and output connections of the flying capacitors are made with internal MOS switches. Pre-regulation limits the gate drive of the MOS switch connected between the voltage input and the flying capacitors. Controlling the on resistance of this switch limits the amount of charge transferred into and out of each flying capacitor during the charge and discharge phases, and in turn helps to keep the output ripple very low. When output currents are low (