LM2612 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter Ul
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LM2612 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter Ultra Low-Voltage Circuits
LM2612 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter Ultra Low-Voltage Circuits
LM2612 step-down DC-DC converter optimized powering ultra-low voltage circuits from single Lithium-Ion cell. provides 400mA (300mA grade), over input voltage range 2.8V 5.5V. programmable output voltages 1.05V, 1.3V, 1.5V 1.8V allow adjustment voltage options without board redesign external feedback resistors. device three pin-selectable modes maximizing battery life mobile phones similar portable applications. Low-noise mode offers 600kHz fixed-frequency operation reduce interference data acquisition applications during full-power operation. mode, internal synchronous rectification provides high efficiency (91% typ. 1.8VOUT). SYNC input allows synchronizing switching frequency range 500kHz 1MHz avoid noise from intermodulation with system frequencies. Low-current hysteretic mode reduces quiescent current (typ.) during system standby. Shutdown mode turns device reduces battery consumption 0.1µA (typ.). Additional features include soft start current overload protection. LM2612 available micro packge. This package uses National's wafer level chip-scale micro technology offers smallest possible size. Only three small external surface-mount components, inductor ceramic capacitors required.
Specifications
Operates from single LiION cell (2.8V 5.5V) programmable output voltage (1.05V, 1.3V, 1.5V 1.8V) 400mA maximum load capability (300mA grade) mode output voltage precision mode output voltage ripple mode quiescent current 0.1µA shutdown mode current Internal synchronous rectification high mode efficiency (91% 2.8VIN, 1.8VOUT) 600kHz mode switching frequency SYNC input mode frequency synchronization from 500kHz 1MHz
Features
Sub-miniature 10-pin micro package Only three tiny surface-mount external components required Uses small ceramic capacitors. Internal soft start Current overload protection external compensation required
Applications
Mobile Phones Hand-Held Radios Battery Powered Devices
Typical Application Circuit
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2003 National Semiconductor Corporation
DS200071
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LM2612
Connection Diagrams
micro package
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VIEW
BOTTOM VIEW
Ordering Information
Order Number 10-Pin micro LM2612ABP LM2612BBP LM2612ABPX LM2612BBPX 10-bump Wafer Level Chip Scale (micro SMD) BPA10VWB Units, Tape Reel Units, Tape Reel 3000 Units, Tape Reel 3000 Units, Tape Reel Package Type Package Drawing Supplied
Description
Number(*) Name VID1 VID0 SYNC/MODE Function Feedback Analog Input. Connect output output filter capacitor (Figure Output Voltage Control Inputs. output voltage using these digital inputs (see Table output defaults 1.5V these pins unconnected. Synchronization Input. this digital input frequency selection modulation control. Set: SYNC/MODE high low-noise 600kHz mode SYNC/MODE low-current mode SYNC/MODE 500kHz 1MHz external clock synchronization external clock mode. Synchronization Operating Modes Device Information section. Enable Input. this CMOS Schmitt trigger digital input high normal operation. shutdown, SGND. during power-up other supply voltage conditions. (See Shutdown Mode Device Information section.) Power Ground Switching Node connection internal PFET switch NFET synchronous rectifier. Connect inductor with saturation current rating that exceeds 850mA Switch Peak Current Limit specification LM2612 (Figure Power Supply Input internal PFET switch. Connect input filter capacitor (Figure Analog Supply Input. board layout optimum, optional 0.1µF ceramic capacitor suggested (Figure Analog Control Ground
PGND
PVIN SGND
note numbering scheme MicroSMD package revised April, 2002 comform JEDEC standard. Only numbers were revised. changes physical location inputs/outputs were made. reference purpose, obsolete numbering VID1 VID0 SYNC PGND PVIN SGND
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LM2612
Absolute Maximum Ratings (Note
Military/Aerospace specified devices required, please contact National Semiconductor Sales Office/ Distributors availability specifications. PVIN, VDD, SGND PGND SGND SYNC/MODE, VID0, VID1 SGND -0.2V -0.2V +0.2V -0.2V (GND -0.2V) (VDD +0.2V)
Storage Temperature Range Lead temperature (Soldering, sec.) Junction Temperature (Note Minimum Rating Human body model, 100pF, Thermal Resistance (JA) LM2612ABP LM2612BBP (Note
-45°C +150°C 260°C -25°C 125°C
2.5kV
170°C/W
Electrical Characteristics
Specifications with standard typeface 25°C, those bold face type apply over full Operating Temperature Range -25°C +85°C). Unless otherwise specified, PVIN SYNC 3.6V, VID0 VID1 Symbol Parameter Input Voltage Range (Note Feedback Voltage (Note Comparator Hysteresis Voltage (Note Shutdown Supply Current Bias Current into (VOUT 1.5V) Conditions PVIN VID1 VIN, VID0 VID0 VIN, VID1 VID0 VIN, VID1 VID0 VID1 VID0 VID1 VHYST Mode (SYNC No-Load, mode (SYNC/MODE No-Load, mode (SYNC/MODE VIN) Pin-Pin Resistance Pin-Pin Resistance Resistance Temperature Coefficient Switch Peak Current Limit (Note Positive Going Threshold Voltage (Note Negative Going Threshold Voltage (Note SYNC/MODE Positive Going Threshold Voltage SYNC/MODE Negative Going Threshold Voltage VID0, VID1 Positive Going Threshold Voltage VID0, VID1 Negative Going Threshold Voltage VID1, VID0 Pull Down Current VID1, VID0 3.6V LM2612ABP LM2612BBP 3.6V 2.54 3.6V 1.70 2.00 2.85 LM2612ABP LM2612BBP LM2612ABP LM2612BBP 1.00 1.274 1.470 1.764 1.05 1.30 1.50 1.10 1.326 1.530 1.836 Units
ISHDN RDSON RDSON RDSON Ilim VEN_H
VEN_L
VSYNC_H VSYNC_L VID_H VID_L IVID
0.95 0.92 0.83
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LM2612
Electrical Characteristics
(Continued) Specifications with standard typeface 25°C, those bold face type apply over full Operating Temperature Range -25°C +85°C). Unless otherwise specified, PVIN SYNC 3.6V, VID0 VID1 Symbol Parameter SYNC/MODE Clock Frequency Range (Note Internal Oscillator Frequency LM2612ABP, Mode (SYNC VIN) LM2612BBP, Mode (SYNC VIN) Conditions 1000 Units
fsync
FOSC
Tmin
Minimum ON-Time Switch Mode Load Transient Response Mode Line Transient Response Mode Circuit Figure IOUT 20mA 200mA Step Circuit Figure 3.0V 3.6V Step
Note Absolute Maximum Ratings indicate limits beyond which damage device occur. Operating Ratings conditions which device intended functional, parameter specifications guaranteed. guaranteed specifications associated test conditions, limits Conditions Electrical Characteristics table. Electrical Characteristics table limits guaranteed production testing, design correlation using standard Statistical Quality Control methods. Typical (Typ) specifications mean average values from characterization guaranteed. Note mode, Thermal shutdown will occur junction temperature exceeds 150°C maximum junction temperature device. Note Thermal resistance specified with layer PCB(0.5/0.5 cu). Note Thermal resistance specified with layer (2/1/1 vias 0.33mm diameter (see Application Note AN-1187). Note LM2612 designed cell phone applications where turn-on after power-up controlled system processor internal UVLO (Under Voltage LockOut) circuitry unecessary. LM2612 UVLO circuitry should kept shutdown holding until input voltage exceeds 2.8V. Although LM2612 exhibited safe behavior during pre-production evaluation while enabled input voltages, this guaranteed. Note feedback voltage trimmed 1.5V output setting. other output voltages result from selection internal DAC's divider ratios. precision feedback voltages except 1.05V setting, which Contact Portable Power Applications group National Semiconductor, trimming other voltages desired. Note hysteresis voltage minimum voltage swing that causes internal feedback control circuitry turn internal PFET switch then off, during mode. Note Current limit built-in, fixed, adjustable. current limit reached while output pulled below about 0.7V, internal PFET switch turns allow inductor current diminish. Note CMOS Schmitt trigger digital input with logic thresholds that scale with supply voltage pin. nominal logic thresholds approximately 0.71VDD 0.55VDD high thresholds respectively. Note SYNC driven with external clock switching between GND. When external clock present SYNC, forced mode external clock frequency. LM2612 synchronizes rising edge external clock.
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LM2612
Typical Operating Characteristics
LM2612ABP, Circuit Figure 3.6V, 25°C, unless otherwise noted. Quiescent Supply Current Temperature Quiescent Supply Current Supply Voltage
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Shutdown Quiescent Current Temperature
Output Voltage Temperature (PWM Mode)
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Output Voltage Temperature (PFM Mode)
Output Voltage Supply Voltage (VOUT 1.8V, Mode)
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Output Voltage Supply Voltage (VOUT 1.8V, Mode) Output Voltage Supply Voltage (VOUT 1.5V, Mode)
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Output Voltage Supply Voltage (VOUT 1.5V, Mode)
Output Voltage Supply Voltage (VOUT 1.3V, Mode)
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Output Voltage Supply Voltage (VOUT 1.3V, Mode)
Output Voltage Supply Voltage (VOUT 1.05V, Mode)
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Output Voltage Supply Voltage (VOUT 1.05V, Mode) Output Voltage Output Current (VOUT 1.8V, Mode)
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Output Voltage Output Current (VOUT 1.8V, Mode)
Output Voltage Output Current (VOUT 1.5V, Mode)
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Output Voltage Output Current (VOUT 1.5V, Modee)
Output Voltage Output Current (VOUT 1.3V, Mode)
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Output Voltage Output Current (VOUT 1.3V, Mode) Output Voltage Output Current (VOUT 1.05V, Mode, With Diode)
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Output Voltage Output Current (VOUT 1.05V, Mode, With Diode)
Efficiency Output Current (VOUT 1.8V, Mode, With Diode)
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Efficiency Output Current (VOUT 1.8V, Mode, With Diode)
Efficiency Output Current (VOUT 1.5V, Mode, With Diode)
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Efficiency Output Current (VOUT 1.5V, Mode, With Diode) Efficiency Output Current (VOUT 1.3V, Mode, With Diode)
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Efficiency Output Current (VOUT 1.3V, Mode)
Efficiency Output Current (VOUT 1.05V, Mode)
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Efficiency Output Current (VOUT 1.05V, Mode, With Diode)
Efficiency Output Current (VOUT 1.8V, Mode,No Diode)
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Efficiency Output Current (VOUT 1.8V, Mode, Diode) Switching Frquency Temperature (PWM Mode)
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Load Transient Response (PWM Mode)
Load Transient Response (PFM Mode)
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INDUCTOR CURRENT, 500mA/div PIN, 5V/div VOUT, 50mV/div, COUPLED LOAD, 20mA 200mA, 200mA/div
INDUCTOR CURRENT, 500mA/div PIN, 5V/div VOUT, 50mV/div, COUPLED LOAD, 10mA 100mA, 100mA/div
Shutdown Response (PWM Mode)
Shutdown Response (PFM Mode)
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INDUCTOR CURRENT, 500mA/div PIN, 2V/div VOUT, 1V/div 5V/div
INDUCTOR CURRENT, 500mA/div PIN, 2V/div VOUT, 1V/div 5V/div
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LM2612
Typical Operating Characteristics LM2612ABP, Circuit Figure 3.6V, 25°C,
unless otherwise noted. (Continued) Response Line Transient Response (PWM Mode)
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INDUCTOR CURRENT, 500mA/div PIN, 2V/div VOUT, 50mV/div, COUPLED SYNC/MODE, 5V/div
SUPPLY VOLTAGE, 500mV/div, COUPLED PIN, 5V/div VOUT, 10mV/div, COUPLED
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LM2612
Device Information
LM2612 simple, step-down DC-DC converter optimized powering low-voltage CPUs DSPs cell phones other miniature battery powered devices. provides pin-selectable output voltages 1.05V, 1.3V, 1.5V 1.8V from single 2.8V 5.5V LiION battery cell. designed maximum load capability 400mA (300mA grade). device three pin-selectable operating modes required cell phones other complex portable devices. Such applications typically spend small portion their time operating full power. During full power operation, synchronized fixed-frequency mode offers full output current capability while minimizing interference sensitive data acquisition circuits. mode uses synchronous rectification high efficiency: typically 100mA load with 1.8V output, 2.8V input. These applications spend remainder their time low-current standby operation shutdown conserve battery power. During standby operation, hysteretic mode reduces quiescent
current 150µA maximize battery life. Shutdown mode turns device reduces battery consumption 0.1µA (typ.). LM2612 offers good performance full features. based current-mode switching buck architecture cycle-by-cycle current limiting. mode output voltage precision most output voltages 1.05V. SYNC/MODE input accepts external clock between 500kHz 1MHz. output voltage selection pins eliminate external feedback resistors. Additional features include soft-start, current overload protection, over-voltage protection thermal overload protection. LM2612 constructed using chip-scale 10-pin micro package. micro package offers smallest possible size space critical applications, such cell phones. Required external components only small 10uH inductor, tiny 10uF 22uF ceramic capacitors reduced board area.
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FIGURE Typical Operating Circuit
Circuit Operation
Referring Figure Figure Figure LM2612 operates follows: During first part each switching cycle, control block LM2612 turns internal PFET switch. This allows current flow from input through inductor output filter capacitor load. inductor limits current ramp with slope (VIN -VOUT)/L, storing energy magnetic field. During second part each cycle, controller turns PFET switch off, blocking current flow from input, then turns NFET synchronous rectifier response, inductor's magnetic field collapses, generating voltage that forces current from ground through synchronous rectifier output filter capacitor load. stored energy
transferred back into circuit depleted, inductor current ramps down with slope VOUT/L. inductor current reaches zero before next cycle, synchronous rectifier turned prevent current reversal. output filter capacitor stores charge when inductor current high, releases when low, smoothing voltage across load. output voltage regulated modulating PFET switch on-time control average current sent load. effect identical sending duty-cycle modulated rectangular wave formed switch synchronous rectifier low-pass filter created inductor output filter capacitor. output voltage equal average voltage pin.
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LM2612
Circuit Operation
(Continued)
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FIGURE Simplified Functional Diagram
Operation
LM2612 current-mode operation connecting SYNC/MODE VDD. While (Pulse Width Modulation) mode, output voltage regulated switching constant frequency then modulating energy cycle control power load. Energy cycle modulating PFET switch on-time pulse-width control peak inductor current. This done controlling PFET switch using flip-flop driven oscillator comparator that compares ramp from current-sense amplifier with error signal from voltage-feedback error amplifier. beginning each cycle, oscillator sets flip-flop turns PFET switch, causing inductor current ramp When current sense signal ramps past error amplifier signal,
comparator resets flip-flop turns PFET switch, ending first part cycle. NFET synchronous rectifier turns until next clock pulse inductor current ramps zero. increase load pulls output voltage down, error amplifier output increases, which allows inductor current ramp higher before comparator turns PFET switch. This increases average current sent output adjusts increase load. Before going comparator, current sense signal summed with slope compensation ramp from oscillator stability current feedback loop. During second part cycle, zero crossing detector turns NFET synchronous rectifier inductor current ramps zero.
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LM2612
Operation
(Continued)
Mode Switching Waveform
Mode Switching Waveform
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INDUCTOR CURRENT, 500mA/div PIN, 2V/div VOUT, 10mV/div, COUPLED
INDUCTOR CURRENT, 500mA/div PIN, 2V/div VOUT, 50mV/div, COUPLED
FIGURE Typical Circuit Waveforms Mode Mode
Operation
Connecting SYNC/MODE SGND sets LM2612 hysteretic operation. While (Pulse Frequency Modulation) mode, output voltage regulated switching with discrete energy cycle then modulating cycle rate, frequency, control power load. This done using error comparator sense output voltage control PFET switch. device waits load discharges output filter capacitor, until output voltage drops below lower threshold errorcomparator. Then error comparator initiates cycle turning PFET switch. This allows current flow from input, through inductor output, charging output filter capacitor. PFET switch turned when output voltage rises above regulation threshold error comparator. After PFET switch turns off, output voltage rises little higher inductor transfers stored energy output capacitor pushing current into output cacitor. Thus, output voltage ripple mode proportional hysteresis error comparator inductor current. mode, device only switches needed service load. This lowers current consumption reducing power consumed during switching action circuit transition losses internal MOSFETs, gate drive currents, eddy current losses inductor, etc. also improves light-load voltage regulation. During second part cycle, intrinsic body diode NFET synchronous rectifier conducts until inductor current ramps zero. LM2612 does turn synchronous rectifier while mode.
50mA precise regulation reduced current consumption when system standby.The LM2612 over-voltage protection feature that activate device left mode under low-load conditions 50mA) prevent output voltage from rising high. Overvoltage Protection, more information. Select modes with SYNC/MODE using signal with slew rate faster than 5V/100µs. comparator Schmitt trigger logic gate drive SYNC/MODE pin. leave floating allow linger between logic levels. These measures will prevent output voltage errors that could otherwise occur response indeterminate logic state. Ensure minimum load keep output voltage regulation when switching modes frequently. minimum load requirement varies depending mode change frequency. typical load required when modes changed intervals, 85µA 800µA
Frequency Synchronization (SYNC/MODE Pin)
SYNC/MODE input also used frequency synchronization. synchronize LM2612 external clock, supply digital signal SYNC/MODE with voltage swing exceeding 0.4V 1.3V. During synchronization, LM2612 initiates cycles rising edge clock. When synchronized external clock, operates mode. device synchronize dutycycle clock over frequencies from 500kHz 1MHz. following waveform duty-cycle guidelines when applying external clock SYNC/MODE pin. Each clock cycle should have high periods between 1.3µs 200ns duty cycle between 70%. total clock period should less. Clock under/ overshoot should less than 100mV below above VDD. When applying noisy clock signals, especially sharp edged signals from long cable during evaluation, terminate cable characteristic impedance; filter SYNC pin, necessary, soften slew rate
Operating Mode Selection (SYNC/MODE Pin)
SYNC/MODE digital input used select between operating modes. SYNC/MODE high (above 1.3V) 600kHz operation when system active load above 50mA. SYNC/MODE (below 0.4V) select mode when load less than
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LM2612
Frequency Synchronization (SYNC/MODE Pin) (Continued)
over/undershoot. Note that sharp edged signals from pulse function generator develop under/overshoot high improperly terminated cable. Drive SYNC/MODE using signal with slew rate faster than 5V/100µs. comparator Schmitt trigger logic gate drive SYNC/MODE pin. leave floating allow linger between logic levels. These measures will prevent output voltage errors that could otherwise occur response indeterminate logic state.
Overvoltage Protection
LM2612 over-voltage comparator that prevents output voltage from rising high when device left mode under low-load conditions. Otherwise, output voltage could rise regulation from minimum energy transferred cycle 200ns minimum on-time PFET switch while mode. When output voltage rises 30mV over regulation threshold, comparator inhibits operation skip pulses until output voltage returns regulation threshold. over voltage protection, output voltage ripple increase slightly.
designed conduct through it's intrinsic body diode during transient intervals before turns eliminating need external diode. Synchronous rectification disabled NFET conducts through it's body diode during second part each cycle while mode reduce quiescent current associated with synchronous rectifier's control circuitry. synchronous rectifier also remain mode when duty cycles short high input-output voltage differentials light loads, when there insufficient time synchronous rectifier activate. body diode NFET also used under these conditions. increase efficiency short duty-cycle conditions, place external Schottky diode from PGND Contact Portable Power applications group National Semiconductor, interested device with synchronous rectification mode.
Current Limiting
current limit feature allows LM2612 protect itself external components during overload conditions. Current limiting implemented using independent internal comparator that trips 850mA max, (980mA grade devices). mode, cycle-by-cycle current limiting normally used. excessive load pulls output voltage down approximately 0.7V, then device switches timed current limit mode. timed current limit mode internal P-FET switch turned after current comparator trips beginning next cycle inhibited 2.5µs force instantaneous inductor current ramp down safe value. mode also uses timed current limit operation. synchronous rectifier timed current limit mode. Timed current limit prevents loss current control seen some products when output voltage pulled serious overload conditions.
Shutdown Mode
Setting digital input SGND places LM2612 0.1uA (typ) shutdown mode. During shutdown, PFET switch, NFET synchronous rectifier, reference, control bias LM2612 turned off. Setting high enables normal operation. While turning soft start activated. CMOS Schmitt trigger digital input with thresholds that scale with input voltage VDD. nominal logic thresholds approximately 0.71VDD 0.55VDD high thresholds respectively. Drive using CMOS logic referenced supply voltage LM2612. must turn LM2612 during power-up undervoltage conditions when supply less than 2.8V minimum operating voltage. LM2612 designed mobile phones similar applications where power sequencing determined system controller internal UVLO (Under Voltage LockOut) circuitry unnecessary. LM2612 UVLO circuitry. Although LM2612 exhibited safe behavior during pre-production evaluation while enabled input voltages, this guaranteed.
Current Limiting Mode Transient Response Considerations
LM2612 designed fast response moderate load steps. Harsh transient conditions during loads above 300mA cause inductor current swing 850mA current limit, resulting mode jitter instability from activation current limit comparator. avoid this jitter instability, power-up start LM2612 into full load (loads near above 400mA). change operating modes output voltages when operating full load. Avoid extremely sharp wide-ranging load steps full load, such from 30mA 350mA.
Internal Synchronous Rectification
While mode, LM2612 uses internal NFET synchronous rectifier improve efficiency reducing rectifier forward voltage drop associated power loss. general, synchronous rectification provides significant improvement efficiency whenever output voltage relatively compared voltage drop across ordinary rectifier diode. Under moderate heavy loads, internal NFET synchronous rectifier turned during inductor current down-slope second part each cycle. synchronous rectifier turned prior next cycle, when inductor current ramps near zero light loads. NFET
Selectable Output Voltage
LM2612 features pin-selectable output voltage eliminate need external feedback resistors. output 1.05V, 1.3V, 1.5V 1.8V configuring VID0 VID1 pins. Setting Output Voltage Application Information section further details.
Soft-Start
LM2612 soft start reduce current inrush during power-up startup. This reduces stress LM2612 external components. also reduces startup transients power source.
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LM2612
Soft-Start
(Continued)
VOUT 1.05
Logic Level VID0 N.C. VID1 N.C.
Soft start implemented ramping internal reference LM2612 gradually increase output voltage. reference ramps about 400µs. When powering mode, soft start take additional 200us allow time error amplifier compensation network charge.
Thermal Overload Protection
LM2612 thermal overload protection function that operates protect itself from short-term misuse overload conditions. When junction temperature exceeds about 155°C, device initiates soft-start cycle which completed after temperature drops below 130°C. Prolonged operation thermal overload conditions damage device considered practice.
VID0 VID1 digital inputs. They high connecting connecting SGND. Optionally, VID0 VID1 driven digital gates that provide over 1.2V high state less than 0.4V state ensure valid logic levels. VID0 VID1 inputs each have internal pull-down that pulls them default 1.5V output, when left unconnected. Leaving these pins open acceptable, setting pins high recommended. INDUCTOR SELECTION 10µH inductor with saturation current rating over 850mA (980mA grade) recommended most applications. inductor's resistance should less than good efficiency. Table Suggested Inductors Their Suppliers lists suggested inductors suppliers.
Application Information
SETTING OUTPUT VOLTAGE LM2612 features pin-selectable output voltage eliminate need external feedback resistors. Select output voltage 1.05V, 1.3V, 1.5V 1.8V configuring VID0 VID1 pins, directed Table VID0 VID1 Output Voltage Selection Settings. TABLE VID0 VID1 Output Voltage Selection Settings VOUT Logic Level VID0 VID1
TABLE Suggested Inductors Their Suppliers Model DO1608C-103 DO1606T-103 UP1B-100 UP0.4CB-100 ELL6GM100M ELL6PM100M P1174.103T CDRH5D18-100 CDRH4D28-100 CDC5D23-100 NP05D B100M NP04S B100N SLF6025T-100M1R0 SLF6020T-100MR90 A918CY-100M A915AY-100M Vendor Coilcraft Coilcraft Coiltronics Coiltronics Panasonic Panasonic Pulse Engineering Sumida Sumida Sumida Taiyo Yuden Taiyo Yuden Toko Toko saturation current rating current level beyond which inductor looses it's inductance. Beyond this rating, inductor looses it's ability limit current through PFET switch ramp allows switch current increase rapidly. This cause poor efficiency, regulation errors stress DC-DC converters like LM2612. Saturation occurs when magnetic flux density from current
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low-cost applications, unshielded bobbin inductor suggested. noise critical applications, toroidal shielded-bobbin inductor should used. good practice board with overlapping footprints both types design flexibility. This allows substitution low-noise toroidal inductor, event that noise from low-cost bobbin models unacceptable.
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LM2612
Application Information
(Continued)
ductor's core material support with energy storage corresponding magnetic field.
through windings inductor exceeds what inTABLE Suggested Capacitors Their Suppliers Model C3225X5RIA226M JMK325BJ226MM ECJ4YB0J226M GRM42-2X5R226K6.3 C2012X5R0J106M JMK212BJ106MG ECJ3YB0J106K GRM40X5R106K6.3 Size 1210 1210 1210 1210 0805 0805 1206 0805 Vendor Taiyo-Yuden Panasonic muRata Taiyo Yuden Panasonic muRata Phone 847-803-6100 847-925-0888 714-373-7366 404-436-1300 847-803-6100 847-925-0888 714-373-7366 404-436-1400 THERMAL DESIGN LM2612 thermal overload protection feature which activates when junction temperature exceeds around 155°C, until device cools 130°C. However, running device this continually damage poor practice. Sufficient thermal design should done keep device below specified 125°C maximum operating junction temperature. MICRO PACKAGE ASSEMBLY micro package requires specialized board layout, precision mounting careful reflow techniques, detailed National Semiconductor Application Note AN1112. Refer section Surface Mount Technology (SMT) Assembly Considerations. best results assembly, alignment ordinals board should used facilitate placement device. Since micro packaging technology, layouts assembly means must thoroughly tested prior production. particular, proper placement, solder reflow resistance thermal cycling must verified. 10-Bump package used LM2612 170micron solder balls requires 6.7mil (6.7/1000 in.) pads mounting circuit board. trace each should enter with entry angle prevent debris from being caught deep corners. Initially, trace each should wide, section long longer, thermal relief. Then each trace should neck optimal width over span mils more, that taper extends beyond edge package. important criterion symmetry. This ensures solder bumps LM2612 re-flow evenly that device solders level board. particular, special attention must paid pads bumps 6-9. Because PVIN PGND typically connected large copper planes, inadequate thermal reliefs result late inadequate reflow these bumps. style used with micro package must NSMD (non-solder mask defined) type. This means that solder-mask opening larger than size 9.7mils LM2612. This prevents that otherwise forms solder-mask overlap. This hold device surface board interfere with mounting. Applications Note AN-1112 specific instructions. micro package optimized smallest possible size applications with infra-red opaque cases. Because micro package lacks plastic encapsu17 www.national.com
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22µF, Ceramic Capacitor (Output Filter Capacitor)
10µF, 6.3V, Ceramic Capacitor (Input Filter Capacitor)
CAPACITOR SELECTION 10µF, 6.3V, ceramic input filter capacitor 22uF, ceramic output filter capacitor. These provide optimal balance between small size, cost, reliability performance. ceramic capacitors. Table Suggested Capacitors Their Suppliers lists suggested capacitors suppliers. 10µF ceramic capacitor used output filter capacitor smaller size applications where worstcase transient load step less than 200mA. 10µF output capacitor trades smaller size increase output voltage ripple, undershoot during line load transient response. input filter capacitor supplies current PFET switch LM2612 first part each cycle reduces voltage ripple imposed input power source. output filter capacitor smoothes current flow from inductor load, helps maintain steady output voltage during transient load changes reduces output voltage ripple. These capacitors must selected with sufficient capacitance sufficiently perform these functions. ESR, equivalent series resistance, filter capacitors major factor voltage ripple. contribution from voltage ripple around 75-95% most electrolytic capacitors considerably less ceramic capacitors. remainder ripple from charge storage capacitance. DIODE SELECTION optional Schottky diode Figure added increase efficiency mode light-load mode. This desired applications where increased efficiency improving operational battery life takes precedence over increased system size associated with Schottky diode. Typically, external schottky diode increases mode efficiency from 72.7% 85.0% load, VOUT 1.8V, 3.6V). efficiency curves Typical Operating Characteristics. Schottky diode with current rating higher than 850mA, such MBRM140T3. device rated more reduces diode reverse leakage high temperature applications.
LM2612
Application Information
(Continued)
lation characteristic larger devices, vulnerable light. Back-side metalization and/or epoxy coating, along with front-side shading printed circuit board, reduce this sensitivity. However, package exposed edges. particular, micro devices sensitive light Infrared range shining package's exposed edges. power-up LM2612 while subjecting high intensity infrared light, otherwise degraded, unpredictable erratic operation result. Examples light sources with high infrared content include halogen lamps. Package circuit case opaque infrared light. BOARD LAYOUT CONSIDERATIONS board layout important part DC-DC converter design. Poor board layout disrupt performance DC-DC converter surrounding circuitry contributing EMI, ground bounce, resistive voltage loss traces. These send erroneous signals DC-DC converter resulting poor regulation instability. Poor layout also result reflow problems leading poor solder joints between micro package board pads. Poor solder joints result erratic degraded performance. Good layout LM2612 implemented following simple design rules: Place LM2612 6.7mil pads micro package. thermal relief, connect each with 6mil wide trace (micro SMD), 6mils long longer, then incrementally increase each trace optimal width over span that taper extends beyond edge package. important criterion symmetry ensure re-flow occurs evenly (see Micro Package Assembly Use). Place LM2612, inductor filter capacitors close together make traces short. traces between these components carry relatively high switching currents antennas. Following this rule reduces radiated noise. Place capacitors inductor within 0.2in (5mm) LM2612. Arrange components that switching current loops curl same direction. During first part
each cycle, current flows from input filter capacitor, through LM2612 inductor output filter capacitor back through ground, forming current loop. second part each cycle, current pulled from ground, through LM2612 inductor, output filter capacitor then back through ground, forming second current loop. Routing these loops current curls same direction prevents magnetic field reversal between part-cycles reduces radiated noise. Connect ground pins LM2612 filter capacitors together using generous component-side copper fill pseudo-ground plane. Then, connect this ground-plane used) with several vias. This reduces ground-plane noise preventing switching currents from circulating through ground plane. also reduces ground bounce LM2612 giving low-impedance ground connection. wide traces between power components power connections DC-DC converter circuit. This reduces voltage errors caused resistive losses across traces. Route noise sensitive traces, such voltage feedback path, away from noisy traces between power components. voltage feedback trace must remain close LM2612 circuit should direct should routed away from noisy components. This reduces radiated onto DC-DC converter's voltage feedback trace. Place noise sensitive circuitry, such radio blocks, away from DC-DC converter, CMOS digital blocks other noisy circuitry. Interference with noisesensitive circuitry system reduced through distance. mobile phones, example, common practice place DC-DC converter corner board, arrange CMOS digital circuitry around (since this also generates noise), then place sensitive preamplifiers stages diagonally opposing corner. Often, sensitive circuitry shielded with metal power post-regulated reduce conducted noise, using lowdropout linear regulators, such LP2966.
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LM2612 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter Ultra Low-Voltage Circuits
Physical Dimensions
inches (millimeters) unless otherwise noted
NOTES: UNLESS OTHERWISE SPECIFIED EPOXY COATING 63Sn/37Pb EUTECTIC BUMP RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD. ESTABLISHED LOWER LEFT CORNER WITH RESPECT TEXT ORIENTATION. REMAINING PINS NUMBERED COUNTER CLOCKWISE. DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE PACKAGE WIDTH, PACKAGE LENGTH PACKAGE HEIGHT. 6.NO JEDEC REGISTRATION SEPT. 2000.
10-Bump micro Package Package Number BPA10 dimensions given: 1.996 0.030mm 2.504 0.030mm 0.850 0.1mm
LIFE SUPPORT POLICY NATIONAL'S PRODUCTS AUTHORIZED CRITICAL COMPONENTS LIFE SUPPORT DEVICES SYSTEMS WITHOUT EXPRESS WRITTEN APPROVAL PRESIDENT GENERAL COUNSEL NATIONAL SEMICONDUCTOR CORPORATION. used herein: Life support devices systems devices systems which, intended surgical implant into body, support sustain life, whose failure perform when properly used accordance with instructions provided labeling, reasonably expected result significant injury user. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that products packing materials meet provisions Customer Products Stewardship Specification (CSP-9-111C2) Banned Substances Materials Interest Specification (CSP-9-111S2) contain ``Banned Substances'' defined CSP-9-111S2.
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LM2612 400mA Sub-miniature, Programmable, Step-Down DC-DC Converter Ultra Low-Voltage Circuits
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Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560
National does assume responsibility circuitry described, circuit patent licenses implied National reserves right time without notice change said circuitry specifications.
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