Range: 5.5V Continuous Output Current Adjustable Output Voltage 0.5V R
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Input Voltage, High Efficiency, Integrated Synchronous Step down DC/DC Regulator
Range: 5.5V Continuous Output Current Adjustable Output Voltage 0.5V RDS(ON) integrated FETs: Efficiency Synchronizable Programmable Frequency: 200kHz 2MHz Power Good Monitor <1µA Shutdown Current Programmable Soft Start Programmable Current Limit Over Temperature protection Ambient Temperature Range 4X4mm MLPQ-20 packages- WEEE RoHS compliant
SC4624A
SC4624A highly integrated synchronous stepdown DC/DC regulator designed input voltage range 2.3V Volts. deliver continuous output current with output voltage Volts. internal RDS(ON) synchronous power switches eliminate need external Schottky diode while delivering overall converter efficiency 95%. power good available monitor output voltage status. Operating frequency adjustable from 2MHz with single resistor synchronized external clock. SC4624A offers adjustable current limit, soft start over temperature protection safeguard device under extreme operating conditions. soft start provides controlled output voltage ramp startup. When logic applied Enable pin, SC4624A enters shutdown mode consumes less than current. SC4624A available MLPQ-20 rated over -40°C +85°C ambient temperature range.
Applications
Voltage Distributed DC-DC Converters Telecommunication Power Supplies Portable Equipment xDSL
Typical Application Circuit
PVIN SYNC/EN PGOOD
Vout
SC4624A
ISET
COMP
AGND
PGND
Revision: July 2008
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SC4624A
POWER MANAGEMENT Configuration
Ordering Information
View
Device
Mark 4624A
Package MLPQ-20
SC4624AMLTRT SC4624AEVB-MLPQ
PVIN
PVIN ISET
Evaluation Board
PGND
PGND
AGND
Notes: Available tape reel only. reel contains 3,000 devices MLPQ-20 package. Available lead-free package only. Device WEEE RoHS compliant.
20Pin MLPQ
29°C/W; 2.5°C/W.
SYNC/EN
PGOOD
COMP
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SC4624A
POWER MANAGEMENT Absolute Maximum Ratings
Parameter Supply Voltage PVIN COMP, ISET, SYNC/EN, PGOOD AGND PGND AGND PHASE Voltage PGND PHASE Pulse Voltage PGND Tpulse 50ns Storage Temperature Range Junction Temperature Reflow Temperature Protection Level(1)
Note: Tested accordance JEDEC standard JESD22-A114B.
Exceeding specifications below result permanent damage device, device malfunction. Operation outside parameters specified Electrical Characteristics section implied.
Symbol PVIN,
Maximum -0.3 -0.3 VCC+
Units
VPHASE VPHASE TSTG
VESD
-0.3 PVIN+ PVIN+
Recommended Operating Conditions
Performance guarantied exceeding specifications below.
Parameter Power Supply Input Voltage Operating Range Ambient Temperature Range Junction Temperature Max. Output Current
Symbol
Conditions
Units
IOUTMAX
Electrical Characteristics
Unless otherwise specified, VIN= VCC=SYNC/EN=3.3V, ROSC=51.1K, RISET=27.4K, -40°C 85°C
Parameter Power Supply Start Threshold Voltage, UVLO Hysteresis Voltage, UVLO Supply Current, Shutdown Supply Current, Operating
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Symbol
Conditions
Units
VIUV VIUVHY IQswitching
Rising
2.25
VSYNC COMP, Load 0.6V, Load
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SC4624A
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless otherwise specified, VIN= VCC=SYNC/EN=3.3V, ROSC=51.1K, RISET=27.4K, -40°C 85°C.
Parameter Thermal Shutdown Thermal Shutdown Trip Point Thermal Shutdown Hysteresis Synchronization, Enable Input SYNC/EN Threshold Frequency Range, SYNC Oscillator Osciilator Frequency Range Osciilator Frequency Accuracy Ramp Peak Valley(1) Ramp Peak Voltage(1) Ramp Valley Voltage(1) Soft Start, Current Limit Soft-Start Charge Current ISET Bias Voltage Over Current Trip Output UVLO Hiccup period(1) Error Amplifier Error Amplifier Open Loop Voltage Gain Error Amplifier Unity Gain Bandwidth(1) Output Voltage Slew Rate, COMP(1) Source Output Current, COMP Sink Output Current, COMP Output Voltage High, COMP
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Symbol
Conditions
Units
TOTP TOTP_HYS
Temperature Rising
VENL VENH FSYNC
Logic Logic High Higher than FOSC
2000
FOSC ROSC= 51.1K ROSC=51.1K, TA=TJ=25°C
1.25 0.25
2000
VISET IIST VOUV TOCHP RISET 27.4K RISIT 57.6K drop 0.45
0.55 2.55 131072 0.61
clks
0.4V 0.6V 0.4V, ICOMP -1mA
V/µs
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SC4624A
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless otherwise specified, VIN= VCC=SYNC/EN=3.3V, ROSC=51.1K, RISET=27.4K, -40°C 85°C.
Parameter Error Amplifier (Cont.) Output Voltage Low, COMP Feedback Voltage Input Bias Current(1) Power Switches High-Side P-MOSFET Side N-MOSFET Power Good PGood Voltage PGood Leakage Current PGood Delay Time(1) PGood High Window
Note: Guaranteed design.
Symbol
Conditions
Units
0.6V, ICOMP 0.4925 2.3V 5.5V FB=VREF
0.25 0.5075
RDSH(on) RDSL(on)
VIN=VCC=5V, ISOURCE TA=TJ=25 VIN=VCC=5V, ISINK TA=TJ=25
VPGL IPGOOD
IPGOOD PGOOD Vout rising Vout falling With respect nominal output, TA=TJ=25
1024
clks
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SC4624A
POWER MANAGEMENT Start Operation Typical Performance Characteristics
Circuit condition: Application circuit#1, 5VIN, 1VOUT
5V/DIV 5V/DIV VOUT Vout 5V/DIV 5V/DIV VOUT Vout
Test condition: 5Vin, 1Vo, Io=0A
Start
Test condition: 5Vin, 1Vo, Io=0A
0.5V/DIV 5V/DIV 10ms/DIV
PGOOD PGOOD
0.5V/DIV 5V/DIV 10ms/DIV
PGOOD PGOOD
Figure Start VIN@0A Shutdown
Test condition: 5Vin, 1Vo, Io=0A
FigureShutdownUp VIN@4A Start
Test condition: 5Vin, 1Vo, Io=4A
5V/DIV 5V/DIV 0.5V/DIV VVout 5V/DIV
PGOOD PGOOD
5V/DIV 5V/DIV
0.5V/DIV VOUT 5V/DIV
Vout PGOOD PGOOD
5ms/DIV
1ms/DIV
Figure Transient responseIN@0A Shutdown
Test condition: 5Vin, 1Vo, Io=0 R=F=2.5A/us,T1=T2=0.1ms
Figure ShutdownRipple Stability
Test condition: 5Vin, 1Vo, Io=4A, (Operating stably)
Vout
20mV/DIV 50mV/DIV
Vout
VOUT Vout
2A/DIV 20us/DIV
lOUT IOUT
2.0V/DIV 1us/DIV
Vphase
PHASE
Figure Transient Response@
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Figure Ripple Stability@4A
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SC4624A
POWER MANAGEMENT Over current protection Operation Typical Performance Characteristics (Cont.)
Test condition: circuit#1, Circuit condition: Application5Vin, 1Vout
Thermal protection
Test condition: 5Vin, 1Vout
0.6V/DIV
0.6V/DIV
Vout
VVout
5.0V/DIV
5.0V/DIV
3.0V/DIV 100ms/DIV
Vphase PHASE
3V/DIV 1s/DIV
Vphase VPHASE
Figure Over Load Hiccup
SYNC
External clock singal=650kHz, duty=50%
Sync Signal Efficiency(%)
Figure Thermal Shutdown Protection@0A
Efficiency
5Vin
2.0V/DIV
SYNC
2.5Vin 3.3Vin
2.0V/DIV 1us/DIV
VPHASE Vphase
Output Current(A)
Figure Synchronization
Internal PMOS RDSON Room Temperature
Figure Efficiency(VIN)
Internal NMOS RDSON Room Temperature
2.5VIN
RDSON
RDSON
2.5VIN
3.3VIN
3.3VIN
5VIN
5VIN
IOUT
IOUT
Figure High-Side P-MOSFET
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Figure Low-Side N-MOSFET
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SC4624A
POWER MANAGEMENT Operation Typical Performance Characteristics (Cont.)
Regulation During Switching Linear Mode
2.54 2.52 2.50 2.48
VOUT
Trip
3.3Vin
5Vin
VOUT
IOUT
2.46 2.44 2.42 2.40 2.38 2.36
2.5Vin
IOUT
RISET
Figure Loading Regulation
Figure Over Current Setting versus RISET
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SC4624A
POWER MANAGEMENT Descriptions
Name MLPQ-20 7,12 8,19,20 PVIN ISET PGOOD Functions Power supply voltage high side MOSFETs. Current limit setting pin. resistor connected between ISET AGND sets over current protection threshold. ceramic decoupling between ISET AGND have reserved prevent from noise influence. Soft start time setting pin. connected from this sets soft start time. Oscillator frequency setting pin. external resistor connected from this sets oscillator frequency. Power good indicator. open drain output. when output below power good threshold level. Power supply voltage analog section controller. connection.
oscillator frequency SC4624A when SYNC/EN pulled held above SYNC/EN synchronous mode activated SYNC/EN driven external clock. shutdown mode invoked SYNC/EN pulled held below 0.8V. COMP AGND PGND This output error amplifier. voltage this point connected inverting input comparator. compensation network required order optimize dynamic performance voltage mode control loop. inverting input error amplifier. serves output voltage feedback point buck controller. senses output voltage through external divider. Analog signal ground. Power ground. Switching nodes
14,15 16,17,18
THERMAL heatsinking purposes only. Connect ground plane using multiple vias. electrically connected internally.
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SC4624A
POWER MANAGEMENT Block Diagram
ASYNCHRONOUS START THERMAL SHUTDOWN
0.5V
BANDGAP
UVLO
GATE
PVIN1 PVIN2
BANDGAP HIGH SIDE DRIVER LOGIC AGND VREF
CONTROL HICCUP
ISET
F(R_ISET)
OVER CURRENT PROTECT
COMP SYNC/EN
CLOCK
BLOCK LOGIC
SHOOTTHRU PROTECTION
SIDE DRIVER LOGIC
0.9VREF
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DELAY
1.1VREF
BOTTOM GATE
SOFT START
ERROR OPAMP
PGND1 PGND2
PGOOD
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SC4624A
POWER MANAGEMENT Application Information
Overview SC4624A programmable high switching frequency, integrated MOSFET, synchronous step down regulator. This reduces external component count makes effective applications which cost sized small. non-overlap protection provided gate drive signals prevent shoot through internal MOSFET pair. SC4624A capable producing output voltage 0.5V operation frequency programmable 2MHz external resistor. features lossless current sensing voltage drop across internal drain source resistance high side MOSFET during conduction period. quiescent supply current shutdown mode typically lower than 1µA. external soft start provided prevent output voltage overshoot during start-up. Over Temperature Protection, Power Good Indicator, External Clock Synchronization some internal added features. Enable SC4624A enabled applying voltage greater than (typical) SYNC/EN pin. voltage determines operation SC4624A. increases during start UVLO block senses keeps high side side MOSFETs internal soft start voltage until reaches faults present, SC4624A will initiate soft start when exceeds typical 120mV hysteresis UVLO comparator provides noise immunity during start (refer Figures Shutdown SC4624A disabled when falls below 1.88V (typical) shutdown mode operation invoked clamping SYNC/EN voltage below 0.8V. During shutdown mode, typical 0.2µA current draw through pin, internal soft start voltage held internal MOSFETs turned off. (refer Figures Soft Start soft start function required step down controllers prevent excess in-rush current through during start external capacitor necessary soft start function connected from AGND.
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During start restart, typical sourcing current charges capacitor then voltage capacitor ramp error reference slowly. closed loop creates narrow width driver pulses while output voltage allows these pulses increase their steady state duty cycle output voltage reaches regulated value. duration soft start SC4624A controlled external capacitor. SC4624A starts asynchronous mode before voltage reaches 0.5V, bottom diode used circulating current during time. voltage level clamped finally. Oscillator used oscillator frequency through external resistor that connected from AGND. internal ramp triangle frequency with peak voltage 1.25V valley voltage 0.25V. approximate operating frequency determined value external resistor shown Figure
Switching Frequency Setting
5VIN
2.5VIN
1000
1200
1400
1600
1800
2000
Fosc (kHz)
Figure Switching Frequency
operation frequency programmed 2MHz, there minimum on-time limitation which around 110ns. Users should take care minimum limitation operating duty cycle under high frequency application.
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SC4624A
POWER MANAGEMENT Operation Information (Cont.) Application
Synchronization Frequency Synchronization operation mode invoked using external clock signal activated when SYNC/EN pulled held above held below 0.8V. range synchronization frequency from 200kHz 2MHz. jitter happens when sync pulse clock edge less than 120ns before phase switches. caused ground bounce synchronization pulse coupled comparator. Users avoid this application. (refer Figure Power Good Indicator PGOOD open-drain incorporated window comparators output. It's necessary that pull-up resistor from PGOOD input supply setting logic high level PGOOD signal. When voltage within +10% setting output voltages typical, output power good comparator becomes high impedance after delay time. PGOOD signal delay time around 1024/ FOSC. shutdown mode power good output actively pulled low. example, 1MHz switching frequency applications, PGOOD delay time around 1ms. Thermal Shutdown When junction temperature rises around 160°C, internal soft start voltage held low, internal high side side MOSFETs turned output voltage will fall zero. Once junction temperature goes below hysteresis temperature around 10°C, regulator will restart. (refer Figure Linear Mode Operation (100% duty) SC4624A allows 100% duty cycle operation. Vout where Output inductor current. RDSH(ON) High side P-MOSFET conduction resistance. After high side PMOS turn around 30ns, comparator will compare between When converter detects over current condition shown Figure SC4624A proceeds into cycle cycle protection mode (Point Point which responds minor over current cases output voltage monitored. over current output voltage (set nominal output voltage) occur same time, pull internal switch comp pulled Test condition: 3.3Vin, 1.2Vo, Io=0 start devices stops switching. Assume from R=F=2.5A/us,T1=T2=0.3ms 0.5V. Once voltage rise forward voltage exceeds 0.4V, hiccup comparator becomes enabled. hiccup period around 217/FOSC. (Point Point attention internal high side PMOS minimum time limitation related duty cycle rate. This condition makes working duty cycle perform randon with output ripple increasing poor transient response. Above phenomenon improved larger output capacitor smaller output inductor. Users need verify whether above application condition opposite influence entire circuit. Over Current Protection over current setting programmed external resistor (RISET). goes through internal sense resistor generates voltage.
where current generated RISET amplified internal current amplifier. RONSENSE Internal sense resistor. Output inductor current goes through internal high side P-MOSFET generate voltage.
Transient response
where Output inductor resistance. RDSH Internal high side P-MOSFET resistance. (refer Figure11). drops gradually close Vout, buck regulator will into 100% duty cycle ratio. matter needing
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example, with switching frequency application
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SC4624A
POWER MANAGEMENT Application information (Cont.)
550kHz, hiccup period around 238ms. (refer Figure poor layout will make trip point shift easily calculate RISET. This because affected ground bounce, spiker voltage between pin, internal parameter tolerance. Users refer Figure shows maximum output current RISET. After required inductor value selected, proper selection core material based peak inductor current efficiency requirements. core must able handle peak inductor current IPEAK without saturation produce core loss during high frequency operation given follows:
Vout
power loss inductor includes core loss copper loss. possible, winding resistance should minimized reduce copper loss inductor, (the core loss found manufacturer's datasheet).
Vout
inductor's copper loss estimated follows:
Iout
Imax
where ILRMS current inductor. This current calculated follows:
Figure Over Current Protection Characteristic Inductor Selection typical SC4624A application, inductor selection mainly based value, saturation current resistance. inductor should able handle peak current without saturating copper resistance winding should possible minimize resistive power loss. inductor value determined according operating point switching frequency follows:
Output Capacitor Selection Basically there major factors consider selecting type quantity output capacitors. first required (Equivalent Series Resistance) which should enough reduce voltage deviation from nominal during load changes. second required capacitance, which should high enough hold output voltage. Before SC4624A regulates inductor current value during load transient, output capacitor delivers additional current needed load. output capacitor, loop parasitic inductance between output capacitor load combined with inductor ripple current major contributors output voltage ripple. Input Capacitor Selection input capacitor selection based ripple current level, required capacitance voltage rating. This capacitor must able provide ripple current
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where switching frequency. ratio peak peak inductor current maximum output load current. peak peak inductor current
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SC4624A
POWER MANAGEMENT Operation Information (Cont.) Application
switching actions. continuous conduction mode, value input capacitor calculated from:
SC4624A
COMP
This current gives capacitor's power loss follows:
Vout
This capacitor's loss significant part total loss converter reduces overall converter efficiency. input ripple voltage mainly depends input capacitor's capacitance given load, input voltage output voltage. Assuming that input current converter constant, required input capacitance given voltage ripple calculated
Figure Compensation Network Provides Poles Zeros
voltage mode step down applications shown Figure power stage transfer function
where VO/VI duty ratio. given input voltage ripple. Loop Compensation Design DC/DC converter, usually required that converter loop gain high cross-over frequency fast load response, high frequency gain steady state error, enough phase margin operating stability. Often have these properties same time. purpose loop compensation arrange poles zeros compensation network meet requirements specific application. SC4624A internal error amplifier requires compensation network connect among COMP pin, GND, output shown Figure compensation network includes used program output voltage according
where load resistance C4's ESR. compensation network will have these characteristics:
GCOMP
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SC4624A
POWER MANAGEMENT Operation Information (Cont.) Application
where
design guidelines SC4624A applications follows: loop gain crossover corner frequency given switching corner frequency 2pfs, Place integrator origin increase frequency gains. Select such that they placed near damp peaking loop gain -20dB/ rate across line obtaining wide bandwidth. Cancel zero from C4's compensator pole (wP1 wESR 1/(RCC4)). Place high frequency compensator pole (wP2 pfs) maximum attenuation switching ripple high frequency noise with adequate phase compensated loop gain will given show Figure
T(s) GPWM GCOMP s2L1C s2L1C
After compensation, converter will have following loop gain:
where GPWM gain. 1.0V, ramp peak valley voltage SC4624A.
Figure Asymptotic Diagrams Power Stage Loop Gain
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SC4624A
POWER MANAGEMENT Operation Information (Cont.) Application
Layout Guidelines order achieve optimal thermal noise immunity high frequency converters, special attention must paid layout. goal layout optimization minimize high di/dt loops reduce ground bounce. Output voltage setting, line regulation, stability switching frequency trip point shifted affected poor layout. following guidelines should used ensure proper functions converters. Both Power ground (PGND) signal ground (AGND) separated. ground plane recommended minimize noise copper losses, maximize heat dissipation. Start layout placing power components first. Arrange power circuit achieve clean power flow route. Minimize high di/dt loops. These loops pass high di/dt current. Make sure trace width wide enough reduce copper losses this loop. Ground bounce happen magnetic flux changed proportional magnetic filed which goes through high di/dt loops. input ceramic capacitor (CIN) should close PVIN pins PGND pins. Both input ceramic capacitor output ceramic capacitor same port. snubber circuit between PVIN pins helpful stability operation. careful with power derating snubber circuit. bypass capacitor should placed next AGND pins. setting resistor (RISET) filter capacitor (CISET) should placed next ISET AGND pins. Feedback divider connects output connector Kelvin connection away from noise sources such switching node switching components. multilayer chip beads between AGND PGND will reduce ground bounce injected "quiet" circuit. It's helpful stability operation. large copper area underneath SC4624 necessary heat sinking purpose. multiple layers large copper area connected through vias used better thermal performance. size vias connection between multiple layers should large solder seep through
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vias bottom layer during re-flow process.
SC4624A
POWER MANAGEMENT Operation Information (Cont.) Application
5Vin
5VIN, 1VOUT, ceramic capacitors application circuit
PGOOD SYNC/EN COMP AGND ISET PVIN PVIN PGND 22uF 47.5k 47nF
2.2pF 390pF
1Vout@4A
270pF 2.32k 28.7k
1.8uH
22uF
PGND
28.7k
SC4624A
MLB-160808-0600R-S2
VIN=5V; Vout=1V/4A Switching Frequency=550kHz Note: (1,2) Option stability TOKO D104C(919AS-1R8N) R12: Multilayer chip inductors; MLB-160808-0600R-S2 Input(C9)/Output Capacitors(C4): Panasonic ECJ33YBOJ226M(22uF/6.3V)
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SC4624A
POWER MANAGEMENT Operation Layout
Component Side (TOP)
(TOP layer)
(Bottom layer)
(IN1 layer)
(IN2 layer)
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SC4624A
POWER MANAGEMENT
Outline Drawing MLPQ
SEATING PLANE
DIMENSIONS INCHES MILLIMETERS
.031 .035 .039 .000 .001 .002 (.008) .007 .010 .012 .154 .157 .161 .100 .106 .110 .154 .157 .161 .100 .106 .110 .020 .012 .016 .020 .004 .004 0.80 0.90 1.00 0.00 0.02 0.05 (0.20) 0.18 0.25 0.30 3.90 4.00 4.10 2.55 2.70 2.80 3.90 4.00 4.10 2.55 2.70 2.80 0.50 0.30 0.40 0.50 0.10 0.10
INDICATOR (LASER MARK)
NOTES:
CONTROLLING DIMENSIONS MILLIMETERS (ANGLES DEGREES).
COPLANARITY APPLIES EXPOSED WELL TERMINALS.
Land Pattern MLPQ
DIMENSIONS INCHES (.156) .122 .106 .106 .020 .010 .033 .189 MILLIMETERS (3.95) 3.10 2.70 2.70 0.50 0.25 0.85 4.80
NOTES:
THIS LAND PATTERN REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES MET. THERMAL VIAS LAND PATTERN EXPOSED SHALL CONNECTED SYSTEM GROUND PLANE. FAILURE COMPROMISE THERMAL AND/OR FUNCTIONAL PERFORMANCE DEVICE.
Contact Information
Semtech Corporation Power Management Products Division Flynn Road, Camarillo, 93012 Phone: (805) 498-2111 Fax: (805) 498-3804
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