LTC2927 provides simple solution power supply tracking sequencing requ

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LTC2927 provides simple solution power supply tracking sequencing requ

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LTC2927 Single Power Supply Tracking Controller DESCRIPTIO
LTC2927 provides simple solution power supply tracking sequencing requirements. selecting resistors, supply configured ramp-up ramp-down with differing ramp rates, voltage offsets, time delays relative other supplies master signal. forcing current into feedback node independent supply, LTC2927 causes output track ramp signal without inserting pass element losses. Because current controlled open-loop manner, LTC2927 does affect transient response stability supply. compact solution point load minimizes trace length DC/DC circuit sensitive node. Furthermore, presents high impedance when power-up complete, effectively removing from DC/DC circuit.
Lare registered trademarks Linear Technology Corporation. ThinSOT trademark Linear Technology Corporation. other trademarks property their respective owners. Patents Pending.
Flexible Power Supply Tracking Tracks Both Down Power Supply Sequencing Supply Stability Affected Count Controls Single Supply without Series FETs Adjustable Ramp Rate Supply Shutdown Output Available 8-Lead ThinSOTand 8-Lead (3mm 2mm) Packages
APPLICATIO
VCORE VI/O Supply Tracking Microprocessor, FPGA Supplies Multiple Supply Systems Point-of-Load Supplies
TYPICAL APPLICATIO
EARLY 3.3V 138k 100k LTC2927 RAMPBUF 16.5k TRACK RAMP
Track-Up Track-Down Waveforms
0.1F
0.1F RUN/SS
DC/DC
1V/DIV 1.8V
1.235V 16.5k
35.7k
EARLY 3.3V LTC2927 RAMPBUF 887k TRACK 412k
2927 TA01a
0.1F RAMP RUN/SS DC/DC 0.8V 887k 10ms/DIV
2927 TA01c
RAMP (3.3V) 2.5V 1.8V 2.5V 1V/DIV
412k
RAMP (3.3V) 2.5V 1.8V
10ms/DIV
2927 TA01b
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LTC2927 ABSOLUTE RATI (Note
Average Current TRACK .5mA .5mA RAMPBUF .5mA Operating Temperature Range LTC2927C 70°C LTC2927I. -40°C 85°C Storage Temperature Range. -65°C 150°C Lead Temperature (Soldering, sec) 300°C Supply Voltage (VCC) -0.3V Input Voltages -0.3V TRACK .-0.3V 0.3V Output Voltages -0.3V RAMP RAMPBUF .-0.3V 0.3V
CONFIGURATION
VIEW VIEW RAMP RAMPBUF TRACK RAMP RAMPBUF TRACK
PACKAGE 8-LEAD (3mm 2mm) PLASTIC EXPOSED (PIN GND, CONNECTION OPTIONAL TJMAX 125°C, 76°C/W
ORDER INFORMATION
LEAD FREE FINISH LTC2927CDDB#PBF LTC2927IDDB#PBF LTC2927CTS8#PBF LTC2927ITS8#PBF LEAD BASED FINISH LTC2927CDDB LTC2927IDDB LTC2927CTS8 LTC2927ITS8 TAPE REEL LTC2927CDDB#TRPBF LTC2927IDDB#TRPBF LTC2927CTS8#TRPBF LTC2927ITS8#TRPBF TAPE REEL LTC2927CDDB#TR LTC2927IDDB#TR LTC2927CTS8#TR LTC2927ITS8#TR PART MARKING* LBQH LBQH LTBQJ LTBQJ PART MARKING* LBQH LBQH LTBQJ LTBQJ PACKAGE DESCRIPTION 8-Lead (3mm 2mm) Plastic 8-Lead (3mm 2mm) Plastic 8-Lead Plastic TSOT-23 8-Lead Plastic TSOT-23 PACKAGE DESCRIPTION 8-Lead (3mm 2mm) Plastic 8-Lead (3mm 2mm) Plastic 8-Lead Plastic TSOT-23 8-Lead Plastic TSOT-23 TEMPERATURE RANGE 70°C -40°C 85°C 70°C -40°C 85°C TEMPERATURE RANGE 70°C -40°C 85°C 70°C -40°C 85°C
Consult Marketing parts specified with wider operating temperature ranges. *The temperature grade identified label shipping container. more information lead free part marking, http://www.linear.com/leadfree/ more information tape reel specifications,
PACKAGE 8-LEAD PLASTIC TSOT-23 TJMAX 125°C, 250°C/W
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LTC2927 ELECTRICAL CHARACTERISTICS
SYMBOL VCC(UVLO) VCC(UVHYST) VON(TH) VON(HYST) IRAMP VRAMPBUF(OL) VRAMPBUF(OH) IERROR(%) VTRACK IFB(LEAK) VFB(CLAMP) VSDO(OL) PARAMETER Supply Voltage Supply Current Supply Undervoltage Lockout Supply Undervoltage Lockout Hysteresis Threshold Voltage Hysteresis Input Current RAMP Input Current RAMPBUF Output Voltage RAMPBUF Output High Voltage, VRAMPBUF(OH) VRAMPBUF Ramp Buffer Offset, VRAMPBUF VRAMP ITRACK Current Mismatch IERROR(%) (IFB ITRACK)/ITRACK TRACK Voltage Leakage Current Clamp Voltage Output Voltage 1.2V, 5.5V VRAMP VCC, Ramp VRAMP VCC, Ramp IRAMPBUF IRAMPBUF -1mA VRAMP VCC/2, IRAMPBUF ITRACK -10A ITRACK -1mA ITRACK -10A ITRACK -1mA 5.5V ISDO 1mA, 2.3V
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. 2.9V 5.5V unless otherwise noted (Note
CONDITIONS
0.25 1.210
0.56 1.230
1.250 ±100 0.82 0.82 ±100
UNITS
0mA, ITRACK -1mA, ITRACK -1mA, IRAMPBUF -1mA Rising Rising
0.77 0.77
0.800 0.800
Note Stresses beyond those listed under Absolute Maximum Ratings cause permanent damage device. Exposure Absolute Maximum Rating condition extended periods affect device reliability lifetime.
Note currents into device pins positive; currents device pins negative. voltages referenced ground unless otherwise specified.
TYPICAL PERFORMANCE CHARACTERISTICS
ITRACK IRAMBUF 4.70
ITRACK -1mA IRAMBUF -2mA
VTRACK Temperature
4.65 VTRACK (mV)
(mA)
4.60
4.55
4.50
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4.45
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TEMPERATURE (°C)
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LTC2927 TYPICAL PERFOR CHARACTERISTICS
VON(TH) Temperature
1.240 1.235 1.230 VON(TH) 1.225 1.220 1.215 1.210 TEMPERATURE (°C)
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VRAMPBUF(OH) (mV)
VRAMPBUF(OL) (mV)
ITRACK
VTRACK
ITRACK (mA)
VSDO(OL)
ERROR
FUNCTIONS TSOT/DFN Packages
(Pin 1/Pin Supply Voltage Input. Operating range from 2.9V 5.5V. undervoltage lockout asserts until 2.5V. should bypassed with 0.1F capacitor. (Pin 2/Pin Slave Supply Shutdown Output. open-drain output that holds shutdown (RUN/SS) slave supply until pulled above 2.5V, pulled above 1.23V, RAMP above 200mV. pulled again when both RAMP 200mV 1.23V. slave supply capable operating with input supply that lower than LTC2927's minimum operating voltage 2.9V, used hold slave supply. unused. (Pin 3/Pin Feedback Control Output. pulls feedback node slave supply. Tracking achieved mirroring current from TRACK into resistive divider connecting RAMPBUF TRACK will force output voltage slave supply track RAMP prevent damage slave supply, will force slave's feedback node above 2.3V. addition, LTC2927 will actively sink current from this node, even when unpowered.
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VRAMPBUF(OL) Temperature
VRAMPBUF(OH) Temperature
TEMPERATURE (°C)
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TEMPERATURE (°C)
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Tracking Cell Error ITRACK
ERROR VTRACK 0.8V ITRACK
VSDO(OL)
ISDO
ISDO
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ITRACK (mA)
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LTC2927 CTIO TSOT/DFN Packages
(Pin 4/Pin Device Ground. TRACK (Pin 5/Pin Tracking Control Input. resistive voltage divider between RAMPBUF TRACK determines tracking profile slave supply. TRACK servos 0.8V, current supplied TRACK mirrored TRACK capable supplying least when 2.9V. Under short circuit conditions, TRACK capable supplying 70mA. connect extended periods. Limit capacitance TRACK less than 25pF RAMPBUF (Pin 6/Pin Ramp Buffer Output. Provides impedance buffered version signal RAMP pin. This buffered output drives resistive voltage divider that connects TRACK pin. Limit capacitance RAMPBUF less than 100pF Float RAMPBUF unused. RAMP (Pin 7/Pin Ramp Buffer Input. RAMP input voltage buffer whose output drives resistive voltage divider connected TRACK pin. Connect this input capacitor ramp voltage generated from internal pull-up pull-down currents. RAMP also connected external ramping signal tracking. Ground RAMP unused. (Pin 8/Pin Control Input. voltage level relative 1.23V threshold (with 75mV hysteresis) controls tracking direction LTC2927. active high causes pull-up current flow RAMP pin, which charges external capacitor. active causes pull-down current RAMP discharge external capacitor relative GND. Exposed (NA/Pin Exposed left open connected device ground.
CTIO BLOCK DIAGRA
RAMPBUF
1.23V
2.5V
UVLO
TRACK
0.8V
RAMP
0.2V
2927
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LTC2927 APPLICATIO ATIO
Power Supply Tracking Sequencing LTC2927 handles variety power-up profiles satisfy requirements digital logic circuits including FPGAs, PLDs, DSPs microprocessors. These requirements fall into four general categories illustrated Figures Some applications require that potential difference between power supplies must never exceed specified voltage. This requirement applies during power-up power-down well during steady-state operation, often prevent destructive latch-up dual supply ASIC. Typically, this achieved ramping supplies down together (Figure other applications desirable have supplies ramp down with fixed voltage offsets between them (Figure have them ramp down ratiometrically (Figure Certain applications require supply come after another. example, system clock need start
1V/DIV
10ms/DIV
2927
Figure Coincident Tracking
1V/DIV
10ms/DIV
2927
Figure Ratiometric Tracking
before block logic. this case, supplies sequenced Figure where 2.5V supply ramps after 1.8V supply completely powered. Operation LTC2927 provides simple solution power supply tracking sequencing profiles shown Figures single LTC2927 controls single supply that tracks "master" signal. With resistors, slave supply configured ramp function master signal. This master signal separate supply ramp signal generated tying RAMP external capacitor. Tracking Cell LTC2927's operation based tracking cell shown Figure which uses proprietary wide-range current mirror. tracking cell shown Figure servos TRACK 0.8V. current supplied TRACK
MASTER SLAVE1 SLAVE2 1V/DIV MASTER SLAVE1 SLAVE2 10ms/DIV
2927
Figure Offset Tracking
MASTER SLAVE1 SLAVE2 1V/DIV
MASTER SLAVE1 SLAVE2
10ms/DIV
2927
Figure Supply Sequencing
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LTC2927 APPLICATIO ATIO
mirrored establish voltage output slave supply. slave output voltage varies with master signal, enabling slave supply controlled function master signal with terms RTB. selecting appropriate values RTB, possible generate profiles Figures Controlling Ramp-Up Ramp-Down Behavior operation LTC2927 most easily understood referring simplified functional diagram Figure When low, master signal RAMP pulled ground. Since current through maximum when master signal low, current from also maximum. This current drives slave output minimum voltage. When rises above 1.23V, master signal rises slave supply tracks master signal. ramp rate external capacitor driven current source RAMP pin. Alternatively, RAMP connected separate supply used master signal. properly designed system, when master signal reached maximum voltage current from TRACK zero. this case, there current from LTC2927 effect output voltage accuracy, transient response stability slave supply. When falls below VON(TH) VON(HYST), typically 1.225V, RAMP pulls down with master signal slave supplies will fall same rate they rose previously.
MASTER
TRACK
0.8V
DC/DC SLAVE
2927
Figure Simplified Tracking Cell
controlled digital used monitor input supply. connecting resistive divider from input supply pin, supplies will ramp only after monitored supply reached preset voltage. resistive divider used voltage, choose values that will keep this voltage above maximum threshold voltage 1.25V lowest operating supply level. Ramp Buffer RAMPBUF provides buffered version RAMP voltage that drives resistive divider TRACK pin. buffered master signal provides drive resistors. Shutdown Output some applications might necessary control shutdown RUN/SS pins slave supplies. LTC2927 able supply rated current from when below 2.9V. slave power supply capable operating input voltages, open-drain output drive SHDN RUN/SS slave supply (see Figure This will hold slave supply output until above 1.23V above 2.5V undervoltage lockout condition.
RONB RONA 1.2V
RAMP CRAMP MASTER
RAMPBUF
TRACK
0.8V
DC/DC
SLAVE
2927
Figure Simplified Functional Diagram
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LTC2927 APPLICATIO ATIO
EARLY 3.3V RONB 138k RONA 100k LTC2927 RAMPBUF 16.5k TRACK
2927
0.1F
RAMP CRAMP 10pF RUN/SS MASTER DC/DC 1.235V 1.8V
35.7k
16.5k
Figure Shutdown Application
pulls again when pulled below 1.23V RAMP below about 200mV. 3-Step Design Procedure following 3-step procedure allows complete design tracking sequencing profiles shown Figures basic single supply application circuit shown Figure ramp rate master signal. Solve value CRAMP, capacitor RAMP pin, based desired ramp rate (V/s) master supply, RAMP IRAMP where IRAMP
Solve pair resistors that provide desired ramp rate slave supply, assuming delay.
EARLY 0.1F
RONB RONA
RAMP CRAMP LTC2927 MASTER RAMPBUF DC/DC TRACK SLAVE
2927
Figure Single Supply Application
Choose ramp rate slave supply, slave supply ramps coincident with master signal with fixed voltage offset, then ramp rate equals master supply's ramp rate. sure fast enough ramp rate slave supply that will finish ramping before master signal reached final supply value. not, slave supply will held below intended regulation value master signal. following formulas determine resistor values desired ramp rate, where feedback resistors slave supply feedback reference voltage slave supply: VTRACK TRACK where VTRACK 0.8V. Note that large ratios slave ramp rate master ramp rate, SS/SM, result negative values RTA'. sufficiently large delay used step will positive, otherwise SS/SM must reduced. Choose obtain desired delay. delay required, such coincident ratiometric tracking, then simply RTA'. delay desired, offset tracking supply sequencing, calculate RTA" determine value where desired delay seconds. VTRACK parallel combination RTA' RTA". noted step small delays large ratios slave ramp rate master ramp rate (usually only seen sequencing) result solutions with negative values RTA. such cases, either delay must increased ratio slave ramp rate master ramp rate must reduced.
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LTC2927 APPLICATIO ATIO
Coincident Tracking Example
1V/DIV
10ms/DIV
Figure Coincident Tracking (from Figure
typical application shown Figure master signal 3.3V ramp generated LTC2927. slave supply 1.8V switching power supply slave supply 2.5V switching power supply. Both slave supplies track coincidently with 3.3V ramping master signal. ramp rate supplies 100V/s. 3-step design procedure detailed previously used determine component values. Only slave supply considered here procedure same slave supply. ramp rate master signal. From Equation RAMP 0.1F 100V
Solve pair resistors that provide desired slave supply behavior, assuming delay. From Equation 16.5k 100V 16.5k 100V
EARLY 3.3V
From Equation 0.8V 1.235V 1.235V 0.8V 16.5k 35.7k 16.5k
Choose obtain desired delay. Since delay desired, RTA'
MASTER SLAVE2 SLAVE1 1V/DIV 10ms/DIV
2927
this example, supply remains while held below 1.23V. When rises above 1.23V, pulls master signal CRAMP 100V/s. master signal buffered from RAMP RAMPBUF pin. this output RAMPBUF rise, current from TRACK reduced. Consequently, voltage slave supply's output increased, slave supply tracks master signal. When again pulled below 1.23V, will pull down CRAMP 100V/s. loads outputs sufficient, outputs will track down coincidently 100V/s.
EARLY 3.3V RONB 138k RONA 100k LTC2927 RAMPBUF RTB1 16.5k TRACK RTA1 RFA1 35.7k RFB1 16.5k 0.1F RAMP 0.1F RUN/SS 3.3V DC/DC 1.235V SLAVE1 1.8V MASTER 3.3V
0.1F LTC2927 RAMPBUF RTB2 887k TRACK RTA2 412k
2927
RAMP 3.3V RUN/SS DC/DC 0.8V RFB2 887k SLAVE2 2.5V
RFA2 412k
Figure Coincident Tracking Example
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LTC2927 APPLICATIO ATIO
Ratiometric Tracking Example
1V/DIV
10ms/DIV
Figure Ratiometric Tracking (from Figure
This example converts coincident tracking example ratiometric tracking profile shown Figure ramp rate master signal remains unchanged (Step there delay ratiometric tracking (Step only result step 3-step design procedure needs considered. this example, ramp rate 1.8V slave supply ramps 60V/s 2.5V slave supply ramps 85V/s. Always verify that chosen ramp rate will allow supplies ramp-up completely before RAMPBUF reaches VCC. 1.8V supply were ramp-up 50V/s would only reach 1.65V because RAMPBUF signal would reach final value 3.3V before slave supply reached 1.8V. Solve pair resistors that provide desired slave supply behavior, assuming delay. From Equation 100V 16.5k 27.4k
From Equation 0.8V 1.235V 1.235V 0.8V 16.5k 35.7k 27.4k
Step unnecessary because there delay, RTA'
MASTER SLAVE2 SLAVE1 1V/DIV 10ms/DIV
2927
EARLY 3.3V
RONB 138k RONA 100k
0.1F RAMP LTC2927 RAMPBUF 0.1F RUN/SS 3.3V DC/DC TRACK 1.235V RFB1 16.5k SLAVE1 1.8V MASTER 3.3V
RTB1 27.4k RTA1
RFA1 35.7k
EARLY 3.3V LTC2927 RAMPBUF RTB2 TRACK RTA2 383k
2927
0.1F RAMP 3.3V RUN/SS DC/DC 0.8V RFB2 887k SLAVE2 2.5V
RFA2 412k
Figure Ratiometric Tracking Example
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LTC2927 APPLICATIO ATIO
Offset Tracking Example
1V/DIV
10ms/DIV
Figure Offset Tracking (from Figure
Converting circuit coincident tracking example offset tracking shown Figure relatively simple. Here 1.8V slave supply ramps below master. ramp rate remains same (100V/s), there changes necessary steps 3-step design procedure. Only step must considered. sure verify that chosen voltage offset will allow slave supply ramp completely. this example, voltage offset were slave supply would only ramp 3.3V 1.3V. Choose obtain desired delay. First, convert desired voltage offset, VOS, delay using ramp rate: 10ms From Equation 0.8V 16.5k 13.2k 10ms 100V
From Equation 13.1k 13.2k 6.65k
MASTER SLAVE2 SLAVE1 1V/DIV 10ms/DIV
2927
EARLY 3.3V
RONB 138k RONA 100k
0.1F RAMP LTC2927 RAMPBUF 0.1F RUN/SS 3.3V DC/DC TRACK 1.235V RFB1 16.5k SLAVE1 1.8V MASTER 3.3V
RTB1 16.5k RTA1 6.65k
RFA1 35.7k
EARLY 3.3V LTC2927 RAMPBUF RTB2 887k TRACK RTA2 316k
2927
0.1F RAMP 3.3V RUN/SS DC/DC 0.8V RFB2 887k SLAVE2 2.5V
RFA2 412k
Figure Offset Tracking Example
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LTC2927 APPLICATIO ATIO
Supply Sequencing Example
1V/DIV
10ms/DIV
Figure Supply Sequencing (from Figure
Figure slave supply slave supply sequenced instead tracking. 3.3V master ramps 100V/s. 1.8V slave supply ramps 1000V/s beginning 10ms after master signal starts ramp 2.5V slave supply ramps 1000V/s beginning 25ms after master signal begins ramp Note that every combination ramp rates delays possible. Small delays large ratios slave ramp rate master ramp rate result solutions that require negative resistors. such cases, either delay must increased ratio slave ramp rate master ramp rate must reduced. this example, solving slave supply yields: ramp rate master signal. From Equation RAMP 0.1F 100V
Solve pair resistors that provide desired slave supply behavior, assuming delay. 100V 16.5k 1.65k 1000V
From Equation 0.8V -2.13k 1.235V 1.235V 0.8V 16.5k 35.7k 1.65k
MASTER SLAVE2 SLAVE1 1V/DIV 10ms/DIV
2927
Choose obtain desired delay. From Equation 0.8V 1.65k 1.32k 10ms 100V
From Equation -2.13k 1.32k 3.48k
EARLY 3.3V RONB 138k RONA 100k LTC2927 RAMPBUF RTB1 1.65k TRACK RTA1 3.48k RFA1 35.7k RFB1 16.5k 0.1F RAMP 0.1F RUN/SS 3.3V DC/DC 1.235V SLAVE1 1.8V MASTER 3.3V
EARLY 3.3V LTC2927 RAMPBUF RTB2 88.7k TRACK RTA2 36.5k
2927
0.1F RAMP 3.3V RUN/SS DC/DC 0.8V RFB2 887k SLAVE2 2.5V
RFA2 412k
Figure Supply Sequencing Example
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LTC2927 APPLICATIO ATIO
Final Sanity Checks collection equations below useful identifying unrealizable solutions. stated step slave supply must finish ramping before master signal reached final voltage. This verified following equation: VTRACK VMASTER Here, VTRACK 0.8V. VMASTER final voltage master signal (VCC RAMP pin). possible choose resistor values that require LTC2927 supply more current than Electrical Characteristics table guarantees. avoid this condition, check that ITRACK does exceed IRAMPBUF does exceed ±2mA. confirm that ITRACK 1mA, TRACK pin's maximum guaranteed current, verify that: VTRACK Finally, check that RAMPBUF will forced sink more than when forced source more than when VMASTER. VTRACK MASTER Resistive Divider
MASTER
Check that voltage above 1.25V maximum threshold lowest possible supply voltage value. RONB VCC(MIN) RONA 1.25V Also check that supply voltage above minimum LTC2927 operating supply voltage 2.9V before above 1.21V minimum threshold voltage.
1V/DIV SLAVE
RONB 2.9V RONA 1.21V example, typical application shown page 3.3V ±10% VIN, lowest possible operating supply voltage will 2.97. RONB 2.97V 1.376 RONA 1.25V RONA 100k then RONB must greater than 137.6k. Therefore, 138k chosen. These values must checked ensure supply reaches LTC2927 minimum operating supply voltage 2.9V before above minimum threshold. 1.38 2.9V 1.389 1.21V Load Requirements When supply ramped down quickly, either load supply itself must capable sinking enough current support ramp rate. example, there large output capacitance supply weak resistive load, supplies that sink current will have their falling ramp rate limited time constant load output capacitance. Figure shows case when slave supply does track master near ground.
10ms/DIV
2927
Figure Weak Resistive Load
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LTC2927 APPLICATIO ATIO
Start-Up Delays Often power supplies start-up immediately when their input supplies applied. LTC2927 tries ramp-up these power supplies soon input supply present, start-up outputs delayed, defeating tracking circuit (Figure 18). Often this delay intentionally configured soft-start capacitor. This remedied either reducing soft-start capacitor slave supply including capacitor pin's resistive divider delay ramp Figure
MASTER
1V/DIV
20ms/DIV
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Figure Power Supply Start-Up Delayed
LTC2927 MASTER MINIMIZE TRACE LENGTH SLAVE 1V/DIV 0.1F
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5ms/DIV
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Figure Delayed
Layout Considerations sure place 0.1F bypass capacitor near possible supply LTC2927. minimize noise slave supply's output, keep trace connecting LTC2927 feedback node slave supply short possible. addition, route this trace next signals with fast transition times. some circumstances might advantageous resistor near feedback node slave supply series with LTC2927. This resistor must exceed: RSERIES
SLAVE
1.5V 1.5V IMAX
This resistor most effective there already capacitor feedback node slave supply (often compensation component). Increasing capacitance slave supply's feedback node will further improve noise immunity, could affect stability transient response supply.
RSERIES
DC/DC
Figure Layout Considerations
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LTC2927 PACKAGE DESCRIPTIO
Package 8-Lead Plastic (3mm 2mm)
(Reference 05-08-1702)
0.61 ±0.05 SIDES) 0.675 ±0.05 2.50 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 0.25 0.05 0.50 2.20 ±0.05 SIDES) RECOMMENDED SOLDER PITCH DIMENSIONS NOTE: DRAWING CONFORMS VERSION (WECD-1) JEDEC PACKAGE OUTLINE M0-229 DRAWING SCALE DIMENSIONS MILLIMETERS DIMENSIONS EXPOSED BOTTOM PACKAGE INCLUDE MOLD FLASH. MOLD FLASH, PRESENT, SHALL EXCEED 0.15mm SIDE EXPOSED SHALL SOLDER PLATED SHADED AREA ONLY REFERENCE LOCATION BOTTOM PACKAGE MARK (SEE NOTE 2.00 ±0.10 SIDES) 3.00 ±0.10 SIDES) 0.115 0.56 0.05 SIDES) 0.38 0.10 0.200 0.75 ±0.05 0.25 0.05 2.15 ±0.05 SIDES) BOTTOM VIEW-EXPOSED CHAMFER EXPOSED
(DDB8) 1103
0.50
0.05
Package 8-Lead Plastic TSOT-23
(Reference 05-08-1637)
0.52 0.65 2.90 (NOTE
1.22
3.85 2.62
2.80
1.50 1.75 (NOTE
RECOMMENDED SOLDER LAYOUT CALCULATOR
0.65
0.22 0.36 PLCS (NOTE
0.80 0.90 0.20 1.00 DATUM 0.01 0.10
0.30 0.50 0.09 0.20 (NOTE NOTE: DIMENSIONS MILLIMETERS DRAWING SCALE DIMENSIONS INCLUSIVE PLATING DIMENSIONS EXCLUSIVE MOLD FLASH METAL BURR MOLD FLASH SHALL EXCEED 0.254mm JEDEC PACKAGE REFERENCE MO-193
1.95
TSOT-23 0802
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Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology Corporation makes representation that interconnection circuits described herein will infringe existing patent rights.
LTC2927 TYPICAL APPLICATIO
EARLY 3.3V RONB 138k RONA 100k LTC2927 RAMPBUF 16.5k TRACK
2927 TA02a
Single Supply Application
EARLY 3.3V RONB 138k RAMP CRAMP 0.1F RUN/SS MASTER 3.3V DC/DC 1.235V 1.8V 78.7k RONA 100k
0.1F
35.7k
RELATED PARTS
PART NUMBER LTC2920 LTC2921/LTC2922 LTC2923 LTC2924 LTC2925 LTC2926 LTC2928 LT4220 LTC4221 LTC4230 LTC4253 DESCRIPTION Power Supply Margining Controller Power Supply Tracker with Input Monitors Power Supply Tracking Controller Quad Power Supply Sequencer Multiple Power Supply Tracking Controller with Power Good Timeout MOSFET-Controlled Power Supply Tracker Multichannel Power Supply Sequencer Supervisor Dual Supply SwapController Dual Swap Controller Triple Swap Controller with Multifunction Current Control -48V Swap Controller Supply Sequencer COMMENTS Single Dual Versions, Symmetric Symmetric High Margining Includes (LTC2921) (LTC2922) Remote Sense Switches Controls Supplies Tracking Sequencing Controls Supplies Sequencing Controls Supplies Tracking Sequencing Active Tracking Control with Series MOSFETs Programmable with External Components; Software Required ±2.7V ±16.5V, Supply Tracking Mode Operates from 13.5V, Allows Supply Sequencing, Active Current Limiting 1.7V 16.5V, Active Inrush Limiting, Fast Comparator Floating Supply from -15V, Active Current Limiting, Enables Three DC/DC Converters
Swap trademark Linear Technology Corporation.
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, 95035-7417
(408) 432-1900 FAX: (408) 434-0507
High Voltage Supply Application
0.1F LTC2927 RAMPBUF TRACK 16.5k
2927 TA02b
RAMP CRAMP 0.4F RUN/SS
MASTER 3.3V DC/DC 1.235V SLAVE
35.7k
311k
2927fb 0308 PRINTED
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LINEAR TECHNOLOGY CORPORATION 2006

LTC2927 provides simple solution power supply tracking sequencing requ

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