LM2636 5-Bit Programmable Synchronous Buck Regulator Controller L

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

LM2636 5-Bit Programmable Synchronous Buck Regulator Controller L

Datasheet Thumbnail

Top Searches for this datasheet

LM2636 5-Bit Programmable Synchronous Buck Regulator Controller
LM2636 5-Bit Programmable Synchronous Buck Regulator Controller
LM2636 high speed controller designed specifically synchronous DC/DC buck converters advance microprocessors. 5-bit accepts code directly from adjusts output voltage from 1.3V 3.5V. provides power good, over-voltage protection, output enable features required Intel specifications. Current limiting achieved monitoring voltage drop across rDS_ON high side MOSFET, which eliminates expensive current sense resistor. LM2636 employs fixed-frequency voltage mode architecture. provide faster response large fast load transient, ultra-fast comparators built monitor output voltage override primary control loop when necessary. frequency adjustable from through external resistor. wide range frequency gives power supply designer flexibility make trade-offs between load transient response performance, MOSFET cost overall efficiency. adaptive non-overlapping MOSFET gate drivers help avoid potential shoot-through problem while maintaining high efficiency. BiCMOS gate drivers with rail-to-rail swing ensure that spurious turn-on occur. When only available, bootstrap structure employed accommodate NMOS high side switch. precision reference trimmed 2.5% over temperature available externally other regulators. Dynamic positioning load voltage, which helps number output capacitors, also implemented easily.
Features
1.3V 3.5V 5-bit programmable output voltage Synchronous rectification Power Good flag output enable Over-voltage protection Initial Output Accuracy: 1.5% over temperature Current limit without external sense resistor Adaptive non-overlapping MOSFET gate drives Adjustable switching frequency: Dynamic output voltage positioning 1.256V reference voltage available externally Plastic SO-20 package TSSOP-20 package
Applications
Motherboard power supply/VRM Cyrix Gxm, Cyrix Gxi, Cyrix MII, PentiumII, Pentium Pro, 6x86 processors 1.3V-3.5V high current power supplies
Typical Application
DS100834-1
FIGURE 1.3V-3.5V, Power Supply
Pentiumis trademark Intel Corporation.
1999 National Semiconductor Corporation
DS100834
www.national.com
LM2636
Connection Diagrams
VIEW means higher than preset voltage across IMAX resistor, which interpreted overcurrent condition. VREF (Pin Bandgap reference voltage. This voltage mainly other power supplies motherboard which need reference. EA_OUT (Pin 10): Output error amplifier. voltage level this compared with internally generated ramp signal determine duty cycle. This necessary compensating primary control loop. (Pin 11): Inverting input error amplifier. necessary compensating control loop. FREQ_ADJ (Pin 12): Switching frequency adjustment. Switching frequency adjusted changing grounding resistance this pin. PWRGD (Pin 13): Power Good. There windows around output voltage that associated with PWRGD pin, window window. PWRGD initially high (open drain state) output voltage travels window, PWRGD goes (low impedance ground). PWRGD initially output voltage travels into window stayed within window least PWRGD goes high. PWRGD high means output voltage least within window whereas PWRGD indicates output voltage definitely outside window. VID4:0 (Pins 18): Voltage Identification Code. five pins accept open-ground pattern 5-bit binary code from outside chip (typically from CPU) generating desired output voltage. Each internally pulled current source. Table shows code table. OUTEN (Pin 19): Output Enable. output voltage disabled when this pulled low. internally pulled current source. HSGATE (Pin 20): Gate drive high-side N-channel MOSFET. This signal interlocked with LSGATE (Pin avoid shoot-through problem. TABLE Code Output VID4
DS100834-3
Plastic SO-20 Order Number LM2636M Package Number M20B VIEW
DS100834-3
Plastic TSSOP-20 Order Number LM2636MTC Package Number MTC20
Descriptions
LSGATE (Pin Gate drive low-side N-channel MOSFET. This signal interlocked with HSGATE (Pin avoid shoot-through problem. BOOTV (Pin Power supply high-side N-channel MOSFET gate drive. voltage should least gate threshold above converter input voltage properly operate high-side N-FET. PGND (Pin Ground high current circuitry. should connected system ground. SGND (Pin Ground signal level circuitry. should connected system ground. (Pin Power supply controller. SENSE (Pin Converter output voltage sensing. provides input power good, fast dual comparator control loop, over-voltage protection circuitry. recommended that capacitor connected between this ground avoid potential noise problems. IMAX (Pin Current limit threshold setting. sinks fixed current. connecting resistor between high side MOSFET drain this pin, fixed voltage drop built across resistor. This voltage drop compared with high-side N-MOSFET determine overcurrent condition occurred. (Pin High-side N-MOSFET source voltage sensing. This below drain voltage. When this voltage lower than that IMAX during time high-side
www.national.com
VID3
VID2
VID1
VID0
Rated Output Voltage 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00
LM2636
Descriptions
VID4 VID3 VID2 VID1
(Continued)
TABLE Code Output (Continued) VID0 Rated Output Voltage 2.05 (shutdown)
www.national.com
LM2636
Absolute Maximum Ratings (Note
Military/Aerospace specified devices required, please contact National Semiconductor Sales Office/ Distributors availability specifications. (All voltages referenced PGND SGND pins.) BOOTV Junction Temperature 150°C Power Dissipation (Note 1.42W Storage Temperature -65°C +150°C
Soldering Time, Temperature Wave seconds) Infrared seconds) Vapor Phase seconds) Susceptibility (Note
260°C 240°C 219°C
Recommended Operating Conditions (Note
Supply Voltage Range (VCC) Junction Temperature Range 4.5V 5.5V +125°C
Electrical Characteristics
unless otherwise indicated under Conditions column. Typicals limits appearing plain type apply +25°C. Limits appearing boldface type apply over +70°C. Symbol VBOOTV VDACOUT Parameter Driver Supply Voltage 5-Bit Output Voltage VID4:0=01111 VID4:0=01101 VID4:0=01011 VID4:0=01001 VID4:0=00111 VID4:0=00101 VID4:0=00001 VID4:0=11101 VID4:0=11010 VID4:0=10111 VOUT SREA BWEA IQ_VCC IQ_BOOTV DMAX DMIN RSENSE RDS_SRC Load Regulation Line Regulation Error Amplifier Gain Error Amplifier Slew Rate Error Amplifier Unity Gain Bandwidth Operating Current Shutdown Current BOOTV Quiescent Current Maximum Duty Cycle Minimum Duty Cycle SENSE Resistance Ground Driver Drain-Source Resistance when Sourcing Current Driver Drain-Source Resistance when Sinking Current Oscillator Frequency BOOTV=5V OUTEN=VCC=5V, VID=10111 OUTEN Floating, VID0:4 Floating BOOTV=12V, OUTEN=0, VID0:4 Floating IOUT=0 Figure VIN=4.75V 5.25V Figure 1.284 1.385 1.483 1.585 1.683 1.784 1.983 2.173 2.471 2.768 1.304 1.406 1.506 1.609 1.709 1.811 2.013 2.206 2.509 2.81 11.5 Conditions 1.324 1.427 1.529 1.633 1.735 1.838 2.043 2.239 2.547 2.852 V/µs Units
RDS_SINK
(Independent BOOTV Voltage)
fOSC
10.5
1000 2000
IMAX
IMAX Sink Current
VIMAX VIFB
www.national.com
LM2636
Electrical Characteristics
Symbol VOUTEN_IH Parameter OUTEN Input Logic Logic High Trip Point OUTEN Input Logic High Logic Trip Point Band Reference Reference Voltage Full Load Reference Voltage High Line Reference Voltage Line Reference Voltage Load Regulation Reference Voltage Line Regulation Ramp Signal Valley Voltage Ramp Signal Peak Voltage PWRGD Trip Points (see Description PWRGD Trip Points (see Description Over-voltage Protection Trip Point Power Good Response Time Power Good Response Time OUTEN Internal Pull-Up Current Pins Logic High Trip Point Pins Logic Trip Point VID0:4 Internal Pull-Up Current Soft Start Duration
(Continued)
unless otherwise indicated under Conditions column. Typicals limits appearing plain type apply +25°C. Limits appearing boldface type apply over +70°C. Conditions OUTEN Voltage OUTEN Voltage IVREF IVREF Sourcing IVREF 5.25V IVREF 4.75V IVREF Sourcing IVREF Changes from 5.25V 4.75V 1.225 1.223 1.226 1.224 1.256 1.254 1.257 1.255 -0.5 1.25 3.25 above Output Voltage, when Output Voltage below Output Voltage, when Output Voltage above Output Voltage, when Output Voltage below Output Voltage, when Output Voltage above Output Voltage VSENSE Rises from Rated VOUT VSENSE Falls from Rated VOUT 2048 clock cycles 1.287 1.285 1.288 1.286 Units
VOUTEN_IL
VREF VREF_LOAD VREF_525 VREF_475 VREF_LOAD VREF_LINE VSAWL VSAWH VPWRBAD_GD
VPWRGD_BAD
VOVP tPWRGD tPWRBAD IOUTEN VVID_IH VVID_IL IVID
Note Absolute Maximum Ratings limits beyond which damage device occur. Recommended Operating Conditions conditions under which device operates correctly. Recommended Operating Conditions imply guaranteed performance limits. Note Maximum allowable power dissipation function maximum junction temperature, TJMAX junction-to-ambient thermal resistance, ambient temperature, maximum allowable power dissipation ambient temperature calculated using:
junction-to-ambient thermal resistance, LM2636 M20B package 88°C/W, 120°C/W MTC20 package.
www.national.com
LM2636
Electrical Characteristics Block Diagram
(Continued)
Note pins rated except IMAX (Pin which rated
DS100834-2
Test Circuit
DS100834-4
FIGURE
www.national.com
LM2636
Applications Information
OVERVIEW LM2636 high speed synchronous buck regulator controller designed vendors motherboard manufacturers need build on-board power supplies Cyrix MII, Pentium Deschutes microprocessors. built-in 5-bit decode 5-bit word provided supply corresponding voltage. also power good (PWRGD) output enable (OUTEN) functions required specification. employs voltage mode control scheme plus fast responding comparators quickly respond large load transients. fast drivers drive high-side low-side NMOS switches synchronous buck regulator. frequency adjustable from through external resistor. Over-voltage protection achieved shutting high-side driver turning low-side driver 100% time. Current limiting implemented sensing high-side NMOS switch shutting present switching cycle when over current condition detected. Soft start functionality realized through internal digital counter internal DAC. THEORY OPERATION Start When voltage exceeds 4.2V, OUTEN logic high code valid, soft start circuitry starts work. duration soft start determined internal digital counter switching frequency. During soft start, output error amplifier allowed increase gradually. When counter counted 2,048 clock cycles, soft start session ends output voltage level error amplifier released allowed value that determined feedback loop. PWRGD forced during soft start turned over output voltage monitoring circuitry after that. Before reaches 4.2V, internal logic power reset state drivers disabled. During normal operation, voltage drops below 3.8V, internal circuitry will into power reset again. hysteresis helps decrease noise sensitivity pin. After soft starts ends during normal operation, converter output voltage exceeds 115% output voltage, LM2636 will lock into over voltage protection mode. high side drive will disabled, side drive will high. There ways clear mode. cycle voltage once. other toggle OUTEN level. After over voltage protection mode cleared, LM2636 will enter soft start session start over. Normal Operation During normal operation mode, LM2636 regulates converter output voltage adjusting duty ratio. output voltage determined 5-bit code user/load. frequency external resistor between FREQ_ADJ ground. resistance needed desired switching frequency
example, desired switching frequency kHz, resistance should around minimum allowable frequency kHz. MOSFET Gate Drive LM2636 gate drives that suitable driving external N-MOSFETs synchronous buck topology. power drivers supplied BOOTV pin. This BOOTV voltage needs least VGS(th) higher than converter input voltage high side fully turned voltage either supplied from separate source other than input voltage generated locally utilizing charge pump structure. typical desktop microprocessor application, chosen input voltage, then used BOOTV. available, simple charge pump circuitry consisting diode small capacitor used, shown Figure
DS100834-6
FIGURE BOOTV Voltage Supplied Charge Pump When side charge pump capacitor charged near input voltage through diode. When side turned off, high side driver enabled, charge pump capacitor starts charge high side gate until fully this time high side source node will close input voltage level upper node capacitor will also input voltage higher than input voltage, enabling high side driver continue working. BOOTV 12V, initial gate charging current typically initial gate discharging current typically good high speed switching. LM2636 gate drives BiCMOS design. Unlike some other bipolar control ICs, gate drive railto-rail swing that ensures spurious turn-on capacitive coupling. Another feature gate drives adaptive nonoverlapping mechanism. gate driver turned until other fully off. dead time between typically This avoids potential shoot-through problem helps improve efficiency. Load Transient Response typical modern application such Pentium core voltage power supply, load transient response critical issue. LM2636 utilizes conventional voltage feedback technology primary feedback control method. When load transient happens, error output voltage level error amplifier. output
www.national.com
LM2636
Applications Information
(Continued)
error amplifier then compared with internally generated ramp signal result comparison series pulses with certain duty ratios. These pulses used control turn-on turn-off MOSFET gate drivers. this way, error output voltage gets "compensated" cancelled change duty ratio switches. During large load transient, depending compensation design, change duty ratio fast less than switching cycle. Refer Design Considerations section more details. Besides usual voltage mode feedback control loop, LM2636 also pair fast comparators (the comparators) help maintain output voltage during large fast load transient. trip points comparators output voltage. When load transient large that output voltage goes outside window, comparator will bypass primary voltage control loop immediately duty ratio either maximum value zero. This provides fastest possible react such large load transient classical buck converter. Power Good Signal power good signal used indicate that output voltage within specified range. LM2636, range window output voltage. During soft start, power good signal always low. soft start session,the output voltage checked PWRGD will asserted voltage within specified range. Over Voltage Protection When output voltage exceeds 115% output voltage after soft start, LM2636 will enter over voltage protection mode which shuts itself down. upper gate driver held while lower gate driver held high. PWRGD will low. LM2636 recover from mode, either OUTEN voltage toggled. Another more subtle recover float pins reapply correct code. Current Limit Current limit realized sensing voltage high side MOSFET when Since rDS_ON MOSFET known value, current through MOSFET known monitoring VDS. relationship between three parameters
example, know that rDS_ON MOSFET current limit want 20A, then should choose value RIMAX provide greatest protection over high side MOSFET, cycle cycle protection implemented. sampling starts early about after switch turned Whenever over current condition detected, high side switch immediately turned side switch turned until next switching cycle comes. delay circumvent switching noise when MOSFET first turned DESIGN CONSIDERATIONS Control Loop Compensation switching regulator should properly compensated achieve stable condition. synchronous buck regulator that needs meet stringent load transient requirement such Pentium core voltage supply, simple 2-pole-1-zero compensation network should suffice, such shown Figure (C1, R2). This because zero typical output capacitors enough make control-to-output transfer function single-pole-roll-off. example, figure values compensation network components Figure Assume following parameters: switching frequency kHz. These parameters based typical application Figure Notice inductor resistance resistance MOSFETs.
implement current limit function, external resistor RIMAX need. resistor should connected between drain high side MOSFET IMAX pin. constant current around forced into IMAX causes fixed voltage drop across RIMAX resistor. This voltage drop then compared with high side MOSFET latter higher, over current reached. appropriate value RIMAX predetermined current limit level ILIM calculated following equation:
DS100834-9
FIGURE Buck Converter from Control Point View
www.national.com
LM2636
Applications Information
control-to-output transfer function
(Continued)
where
zero frequency
power stage double pole frequency
poles located origin help achieve highest gain. there three parameters determine, position zero, position second pole, constant determine cutoff frequency phase margin, loop bode plots need generated. loop transfer function
corresponding Bode plots shown Figure
-TF1 choosing zero close double pole position second pole half switching frequency, closed loop transfer function turns very good. That 1.32 kHz, kHz, 10-6 then cutoff frequency will kHz, phase margin will 72°, gain will that error amplifier. Figure below.
DS100834-13
FIGURE Control-to-Output Bode Plots Since zero frequency low, effectively cancels phase shift from power stage poles. This limits total phase shift 90%. Although this regulator design stable (phase shift when gain 0dB), needs compensation improve gain frequency (0dB frequency). Otherwise, gain cause poor line regulation, cutoff frequency will hurt transient response performance. transfer function 2-pole-1-zero compensation network shown Figure
DS100834-17
FIGURE Loop Bode Plots compensation network component values determined following equations:
Notice there three equations four variables. variables chosen arbitrarily. Since current driving capability error amplifier limited around good idea have high impedance path from output error amplifier output converter. From above equations told that larger will
www.national.com
LM2636
Applications Information
(Continued)
result smaller larger However, large also bring error bias current required inverting input error amplifier. Calculations show that following combination good one: 0.022 different application different type output capacitors, different compensation scheme necessary. user either follow steps above figure appropriate component values contact factory help. MOSFET SELECTION selection MOSFET switches affects both efficiency whole converter current limit setting. From efficiency point view suggested that high-side switch, only logic level MOSFETs used. Standard MOSFETs used side switch when used power BOOTV pin. lower loss associated with MOSFETs two-fold Ohmic loss switching loss. Ohmic loss easy calculate whereas switching loss much more difficult estimate. general switching loss directly proportional switching frequency. power MOSFET technology advances, lower lower gate charge devices will available. That should allow user higher switching frequencies without penalty losing much efficiency. example, select MOSFETs converter with target efficiency load 2.8V, 14A. Assume inductors lose capacitors lose 0.75W total switching loss 3.2W. total allowed power loss 9.8W, MOSFET Ohmic loss should exceed 4.9W. Assume switches have same conduction loss, i.e., 2.5W each, then resistance switches
quickly supply current output capacitors when load suddenly kicks quickly stop supplying current when load suddenly removed. Multilayer ceramic (MLC) capacitors have very also capacitance value compared other kinds capacitors. aluminum electrolytic capacitors tend have large sizes capacitances. Tantalum electrolytic capacitors have fairly with much smaller size capacitance than aluminum capacitors. Certain OSCON capacitors present ultra long life span. time total output capacitor bank reaches around capacitance aluminum/ tantalum/OSCON capacitors usually already millifarad range. those capacitors, only factor consider. MLCs have same amount total with much less capacitance, most probably under very small inductor, ultra fast control loop high switching frequency become necessary such case deal with fast charging/discharging rate output capacitor bank. From cost savings point view, aluminum electrolytic capacitors most popular choice output capacitors. They have reasonably long life span they tend have huge capacitance withstand charging discharging process during load transient fairly long period. Sanyo MV-GX series gives good performance when enough capacitors paralleled. 6MV1500GX capacitor typical Five these capacitors should sufficient case on-board power supply Pentium motherboard. challenge input capacitors ripple current. large ripple current drawn high side switch tends generate quite some heat capacitor ESR. ripple current ratings capacitor catalogs usually specified under highest allowable temperature. case desktop applications, those ratings seem conservative. good ensure enough number capacitors through evaluation. input current ripple value determined following equation:
power loss each input capacitor side switch resistance much higher than high side because 2.8V duty cycle higher than becomes even larger full load. high side switch, IRL3202 (TO-220 package) IRL3202S (D2PAK) should sufficient. side switch, IRL3303 (TO-220 package) IRL3303S (D2PAK) should sufficient. Since each dissipating 3.2W/2 2.5W 4.1W, suggested that appropriate heat sinks used case TO-220 package large enough copper area connected drain case surface mount package. CAPACITOR SELECTION selection capacitors extremely important step when designing converter load such Pentium Since typical slew rate load current during large load transient around 20A/µs 30A/µs, switching converter rely output capacitors take care first microseconds. Under such current slew rate, output capacitors more concern than ESL. Depending kind capacitors being used, capacitance output capacitors important factor. When output capacitance low, converter have have small output inductor
www.national.com
case Pentium power supply, maximum output current around 14A. Under worst case when duty cycle 50%, maximum input capacitor ripple current half output current, i.e., found that three Sanyo 16MV820GX capacitors enough under room temperature. typical those capacitors power loss each them around (7A)2 m/32 0.24W. Note that power loss each capacitor inversely proportional square total number capacitors, which means power loss each capacitor quickly drops when number capacitors increases. INDUCTOR SELECTION size output determined number parameters. Basically larger inductor, smaller output ripple voltage, slower converter's response speed during load transient. other hand, smaller inductor requires higher switching frequency maintain same level output ripple, probably results more lossy converter, less inertia responding load tran-
LM2636
Applications Information
(Continued)
sient. case Pentium power supply, fast recovery load voltage from transient window back steady state window considered important. This limits highest inductance value that used. lowest inductance value limited highest switching frequency that practically employed. switching frequency increases, switching loss MOSFETs tends increase, resulting less converter efficiency larger heat sinks. good switching frequency probably frequency under which MOSFET conduction loss higher than switching loss because cost MOSFET directly related RDSON. inductor size determined following equation:
where (di/dt)MAX maximum allowable input current slew rate, which 0.1A/µs case Pentium power supply. input inductor size, according above equation, should DYNAMIC POSITIONING LOAD VOLTAGE Since Intel specifications have defined operating windows core voltage, being steady state window other transient window, good idea dynamically position steady state output voltage steady state window with respect load current level that output voltage more headroom load transient response. This requires information about load current. There least simple ways implement this idea with LM2636. utilize output inductor resistance, Figure average voltage across output inductor actually that across resistance. That average voltage proportional load current. Since switching node voltage bounces between input voltage ground switching frequency, impossible choose point feedback point, otherwise dynamic performance will suffer system have some noise problems. Using pass filter network around inductor, such shown figure, seems good idea. feedback point
where VO_RIP peak-to-peak output ripple voltage, switching frequency. commonly used RDSON MOSFETs, reasonable switching frequency kHz. Assume output peak-peak ripple voltage guaranteed, total output capacitor input voltage output voltage 2.8V. inductance value according above equation will then highest slew rate inductor current when load changes from load full load determined follows:
where DMAX maximum allowed duty cycle, which around LM2636. load transient from 14A, highest current slew rate inductor, according above equation, 0.85A/µs, therefore shortest possible total recovery time 14A/(0.85A/µs) 16.5 Notice that output voltage starts recover whenever inductor starts supply current. highest slew rate inductor current when load changes from full load load determined from same equation, DMIN instead DMAX. Since DMIN LM2636 slew rate therefore -1.4A/µs. approximate total recovery time will 14A/(1.4A/µs) input inductor limiting input current slew rate during load transient. case that aluminum electrolytic capacitors used input capacitor bank, voltage change capacitor charging/discharging usually negligible first dominant factor determining amount capacitor voltage undershoot/overshoot load transient. worst case when load changes between load full load, under which condition input inductor sees highest voltage change across input capacitors. Assume input capacitor bank made three 16MV820GX, i.e., total Whenever there sudden load current change, initially supported input capacitor bank instead input inductor. full load swing between 14A, voltage seen input inductor following equation determine minimum inductance value:
DS100834-26
FIGURE Dynamic Voltage Positioning Utilizing Output Inductor Resistance Since switching frequency impedance much less than bouncing voltage point will mainly applied across resistor point will much quieter than However, average still majority average, because resistor divider. steady state VCORE, where inductor resistance. load, output voltage equal full load, output voltage lower than further utilize steady state window, resistor connected between ground increase load output voltage close upper limit window.
www.national.com
LM2636
Applications Information
(Continued)
REFERENCE VOLTAGE VREF have many uses, such watchdog circuitry controller. Figure shows application where VREF used build N-FET controller. appropriate compensation network necessary tailor dynamic performance whole power supply.
DS100834-28 DS100834-27
FIGURE Dynamic Voltage Positioning Using Stand-Alone Resistor possible drawback scheme Figure slow transient recovery speed. Since resistor capacitor have large time constant, settling point steady state value during load transient take milliseconds. Depending interaction between compensation network capacitor, Vcore take different routes reach steady state value. This undesired when load transients happens more than 1000 times second. Reducing time constant will result more fluctuating less effective pass filter. Fine tuning parameters balance tradeoffs. Another implement dynamic voltage positioning through stand-alone resistor, such resistor Figure above. advantage this implementation over previous much faster speed VCORE from transient level steady state level. disadvantage less efficiency. total power loss 0.78W load current. cost resistor minimized implementing through trace.
FIGURE VREF Used N-FET Supply LAYOUT CONSIDERATIONS There several points consider. copper ground plane tight load regulation desired. case dynamic voltage positioning, this concern because loose load regulation desired anyway. However, forget take into consideration voltage drop caused ground plane when calculating dynamic voltage positioning parameters. keep gate traces short. However, make them short else LM2636 stay close MOSFETs heated them. same reason, wide traces, traces should enough. When employing dynamic voltage positioning, place feedback point connector pins have tight load regulation. on-board power supply, place feedback point Slot connector wherever closest MPU. Start component placement with power devices such MOSFETs inductors. place LM2636 directly underneath MOSFETs when when surface mount MOSFETs used. possible, keep capacitors some distance away from inductors that capacitors will have lower temperature environment. When implementing dynamic voltage positioning through trace, aware that trace heat source avoid placing trace directly underneath LM2636.
www.national.com
LM2636
Physical Dimensions
inches (millimeters) unless otherwise noted
20-Lead Plastic Package Order Number LM2636M Package Number M20B
www.national.com
LM2636 5-Bit Programmable Synchronous Buck Regulator Controller
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
20-Lead Plastic TSSOP (MTC) Order Number LM2636MTC Package Number MTC20
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.
National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: 80-530 Email: europe.support@nsc.com Deutsch Tel: 80-530 English Tel: 80-532 Tel: 80-532 Italiano Tel: 80-534
critical component component life support device system whose failure perform reasonably expected cause failure life support device system, affect safety effectiveness.
National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com
National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
National does assume responsibility circuitry described, circuit patent licenses implied National reserves right time without notice change said circuitry specifications.

LM2636 5-Bit Programmable Synchronous Buck Regulator Controller L

Top Searches for this datasheet

Other recent searches