LM2773

LM2773 Low-Ripple 1.8V/1.6V Spread-Spectrum Switched Capacitor Step-Down Regulator January 22, 2008 LM2773 Low-Ripple 1.8V/1.6V Spread-Spectrum Switched Capacitor Step-Down Regulator General Description The LM2773 is a switched capacitor step-down regulator that produces a selectable 1.8V or 1.6V output. It is capable of supplying loads up to 300mA. The LM2773 operates with an input voltage from 2.5V to 5.5V, accommodating 1-cell Li-Ion batteries and chargers. The LM2773 utilizes a regulated charge pump with gains of 2/3x and 1x. It has very low ripple and noise on both the input and output due to its pre-regulated 1.15MHz (typ.) switching frequency and spread spectrum operation. When output currents are low, the LM2773 automatically switches to a lowripple PFM regulation mode to maintain high efficiency over the entire load range. The LM2773 is available in National’s 0.5mm pitch 9-bump Micro-SMD (µSMD-9). Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Low-Noise Spread Spectrum Operation 1.8V/1.6V Selectable Output Voltage 2% Output Voltage Regulation > 75% Efficiency in 1.8V Mode Very Low Output Ripple: 10mV @ 300mA Output Currents up to 300mA 2.5V to 5.5V Input Voltage Range Shutdown Disconnects Load from VIN 1.15MHz Switching Frequency No Inductors…Small Solution Size Short Circuit and Thermal Protection 0.5mm pitch, µSMD-9 (1.511 × 1.511mm × 0.6mm) Applications ■ Power Supply for DSP's, Memory, and Microprocessors ■ Mobile Phones and Pagers ■ Digital Cameras, Portable Music Players, and Other Portable Electronic Devices Typical Application Circuit LM2773 Efficiency vs. Low-Dropout Linear Regulator (LDO) Efficiency 30047401 30047410 © 2008 National Semiconductor Corporation 300474 www.national.com LM2773 Connection Diagram and Package Mark Information 9-Bump Micro SMD (µSMD-9) NS Package Number TLA9ZZA, 0.5mm Pitch 1.511mm x 1.511mm x 0.6mm 30047402 Note 1: The actual physical placement of the package marking will vary from part to part. The package marking "X" designates the single digit date code. "V" is a NSC internal code for die traceability. Both will vary considerably. "DJ" identifies the device (part number, option, etc.). Pin Descriptions Pin # A1 A2 A3 B1 B2 B3 C1 C2 C3 Name C2VOUT C1+ GND EN VIN SEL C1C2+ Flying Capacitor 2: Negative Terminal Output Voltage Flying Capacitor 1: Positive Terminal Ground Device Enable. Logic HIGH: Enabled, Logic LOW: Shutdown. Input Voltage. Recommended VIN Operating Range = 2.5V to 5.5V. Voltage Mode Select. Logic HIGH: VOUT = 1.6V, Logic LOW: VOUT = 1.8V Flying Capacitor 1: Negative Terminal Flying Capacitor 2: Positive Terminal Description Order Information Output Voltages 1.8V/1.6V 1.8V/1.6V Order Number LM2773TL LM2773TLX Package Mark ID XV DJ XV DJ Package TLA9ZZA 9-Bump µSMD Supplied as: 1000 Units, Tape and Reel 4500 Units, Tape and Reel www.national.com 2 LM2773 Absolute Maximum Ratings (Notes 2, 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN Pin Voltage EN, SEL Pin Voltage Continuous Power Dissipation (Note 4) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Soldering, 10 sec.) ESD Rating (Note 5) Human Body Model: -0.3V to 6.0V -0.3V to (VIN+0.3V) w/ 6.0V max Internally Limited 150°C -65°C to +150° C 265°C   2.5kV (Notes 3, 8) Operating Ratings (Notes 2, 3) Input Voltage Range Recommended Load Current Range Junction Temperature (TJ) Range Ambient Temperature (TA) Range (Note 6) 2.5V to 5.5V 0mA to 300mA -30°C to +110°C -30°C to +85°C Thermal Properties Junction-to-Ambient Thermal Resistance (θJA), µSMD-9 Package (Note 7) 75°C/W Electrical Characteristics Limits in standard typeface are for TJ = 25°C. Limits in boldface type apply over the full operating junction temperature range (-30° C ≤ TJ ≤ +110°C) . Unless otherwise noted, specifications apply to the LM2773 Typical Application Circuit (pg. 1) with: VIN = 3.6V; V(EN) = 1.8V, V(SEL) = 0V, CIN = C1 = C2 = 1.0µF, COUT = 4.7µF. (Note 10) Symbol Parameter 1.8V Mode Output Voltage Regulation VOUT 1.6V Mode Output Voltage Regulation Output Load Regulation Output Line Regulation Power Efficiency Quiescent Supply Current Fixed Frequency Output Ripple PFM–Mode Output Ripple Shutdown Current Switching Frequency Open-Loop Output Resistance IOUT = 300mA IOUT = 0mA (Note 11) IOUT = 300mA IOUT < 40mA V(EN) = 0V 3.0V ≤ VIN ≤ 5.5V IOUT = 300mA (Note 9) VIN = 5.5V ICL tON VIL VIH IIH IIL Output Current Limit Turn-on Time Logic-low Input Voltage Logic-high Input Voltage Logic-high Input Current Logic-low Input Current EN, SEL Pins 2.5V ≤ VIN ≤ 5.5V EN, SEL Pins 2.5V ≤ VIN ≤ 5.5V V(EN), V(SEL) = 1.8V (Note 12) V(EN), V(SEL) = 0V 0 1.0 5 0.01 0V ≤ VOUT ≤ 0.2V (Note 13) 0.80 Condition 2.5V ≤ VIN ≤ 5.5V V(SEL) = 1.8V 2.5V ≤ VIN ≤ 5.5V 0mA ≤ IOUT ≤ 300mA 1.587 (−2%) 1.619 0.15 0.3 75 48 10 12 0.1 1.15 1.0 0.625 1.50 55 1.651 (+2%) mV/mA %/V % µA mV mV µA MHz Ω 0mA ≤ IOUT ≤ 300mA Min 1.779 (−2%) Typ 1.815 Max 1.851 (+2%) V Units VOUT/IOUT VOUT/VIN E IQ VR VR–PFM ISD FSW ROL 0mA ≤ IOUT ≤ 300mA 500 150 0.5 VIN mA µs V V µA µA Note 2: 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 3: All voltages are with respect to the potential at the GND pins. 3 www.national.com LM2773 Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150°C (typ.) and disengages at TJ=140°C (typ.). 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 = 110°C), 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). 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: Open loop output resistance can be used to predict output voltage when, under low VIN and high IOUT conditions, VOUT falls out of regulation. VOUT = (Gain)VIN - (ROL x IOUT) Note 10: CIN, COUT, C1, C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics. Note 11: VOUT is set to 1.9V during this test (Device is not switching). Note 12: There are 350kΩ pull-down resistors connected internally between the EN pin and GND and the SEL pin and GND. Note 13: Under the stated conditions, the maximum input current is equal to 2/3 the maximum output current. Block Diagram 30047403 www.national.com 4 LM2773 Typical Performance Characteristics Unless otherwise specified: VIN = 3.6V, CIN = C1 = C2 = 1.0µF, COUT = 4.7µF, V(EN) = 1.8V, V(SEL) = 0V, TA = 25°C. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's). Output Voltage vs. Input Voltage, 1.8V Mode Output Voltage vs. Input Voltage, 1.6V Mode 30047404 30047405 Output Voltage vs. Output Current, 1.8V Mode Output Voltage vs. Output Current, 1.6V Mode 30047406 30047407 5 www.national.com LM2773 Efficiency vs. Input Voltage, 1.8V Mode Efficiency vs. Input Voltage, 1.6V Mode 30047408 30047409 Shutdown Supply Current Operating Supply Current 30047412 30047411 Line Step 3.0V to 4.2V with Load = 300mA, 1.8V Mode Line Step 3.0V to 4.2V with Load = 300mA, 1.6V Mode 30047413 30047414 CH1: VIN; Scale: 1V/Div, DC Coupled CH2: VOUT; Scale: 20mV/Div, AC Coupled Time scale: 10ms/Div CH1: VIN; Scale: 1V/Div, DC Coupled CH2: VOUT; Scale: 20mV/Div, AC Coupled Time scale: 10ms/Div www.national.com 6 LM2773 Load Step 0mA to 300mA, VIN = 3.6V, 1.8V Mode Load Step 300mA to 0mA, VIN = 3.6V, 1.8V Mode 30047415 30047416 CH2: VOUT; Scale: 100mV/Div, DC Coupled, Offset 1.834V CH4: IOUT; Scale: 100mA/Div Time scale: 4ms/Div CH2: VOUT; Scale: 100mV/Div, DC Coupled, Offset 1.834V CH4: IOUT; Scale: 100mA/Div Time scale: 4ms/Div Load Step 0mA to 300mA, VIN = 3.6V, 1.6V Mode Load Step 300mA to 0mA, VIN = 3.6V, 1.6V Mode 30047417 30047418 CH2: VOUT; Scale: 100mV/Div, DC Coupled, Offset 1.633V CH4: IOUT; Scale: 100mA/Div Time scale: 4ms/Div CH2: VOUT; Scale: 100mV/Div, DC Coupled, Offset 1.633V CH4: IOUT; Scale: 100mA/Div Time scale: 4ms/Div 1.8V Mode Startup, Load = 300mA 1.6V Mode Startup, Load = 300mA, VSEL = VIN 30047419 30047420 CH1: VEN; Scale: 5V/Div, DC Coupled CH2: VOUT; Scale: 500mV/Div, DC Coupled Time scale: 10µs/Div CH1: VEN; Scale: 5V/Div, DC Coupled CH2: VOUT; Scale: 500mV/Div, DC Coupled Time scale: 10µs/Div 7 www.national.com LM2773 Operation Description OVERVIEW The LM2773 is a switched capacitor converter that produces a selectable 1.8V or 1.6V regulated output. The core of the part is a highly efficient charge pump that utilizes fixed frequency pre-regulation, Pulse Frequency Modulation, and spread spectrum to minimize conducted noise and power losses over wide input voltage and output current ranges. A description of the principal operational characteristics of the LM2773 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 LM2773 is a two-phase charge pump controlled by an internally generated non-overlapping clock. The charge pump operates by using external flying capacitors C1 and C2 to transfer charge from the input to the output. The LM2773 will operate in a 1x Gain, with the input current being equal to the load current, when the input voltage is at or below 3.5V (typ.) for 1.8V mode or 3.3V (typ.) for 1.6V mode. At input voltages above 3.5V (typ.) or 3.3V (typ.) for the respective voltage mode selected, the part utilizes a gain of 2/3x, resulting in an input current equal to 2/3 times 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 LM2773 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 LM2773 uses fixed frequency pre-regulation to regulate the output voltage to 1.8V 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 (