LTC2927 Linear Technology, LTC2927 Datasheet
LTC2927
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LTC2927 Summary of contents
Page 1
... By forcing current into a feedback node of an independent supply, the LTC2927 causes the output to track a ramp signal without inserting any pass element losses. Because the current is controlled in an open-loop manner, the LTC2927 does not affect the transient response or stabil- ity of the supply ...
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... For more information on tape and reel specifi cations (Note 1) Average Current TRACK .................................................................5mA FB ........................................................................5mA + 0.3V RAMPBUF ............................................................5mA CC Operating Temperature Range LTC2927C ................................................ 0°C to 70°C + 0.3V LTC2927I.............................................. –40°C to 85°C CC Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300° SDO FB GND ...
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... Note 2: All currents into the device pins are positive; all currents out of device pins are negative. All voltages are referenced to ground unless otherwise specifi –1mA TRACK –2mA RAMBUF 4.65 4.60 4.55 4.50 4.45 6.0 2.5 3.0 3.5 4.0 4.5 5.0 V (V) CC LTC2927 www.DataSheet4U.com MIN TYP MAX l 2.9 5.5 l 0.25 0.56 1 –1mA 3 3.6 4.2 l 2.2 2.5 2 1.210 1.230 1.250 150 l 0 ± ...
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... RAMP . CC To prevent damage to the slave supply, the FB pin will not force the slave’s feedback node above 2.3V. In addition, the LTC2927 will not actively sink current from this node, even when it is unpowered. www.DataSheet4U.com V ...
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... Ground RAMP if unused. ON (Pin 8/Pin 1): On Control Input. The voltage level of the ON pin relative to its 1.23V threshold (with 75mV hysteresis) controls the tracking direction of the LTC2927. An active high causes a 10μA pull-up current to fl the RAMP pin, which charges an external capacitor. An active low at the ON pin causes a 10μ ...
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... The LTC2927 provides a simple solution to all of the power supply tracking and sequencing profi les shown in Figures single LTC2927 controls a single sup- ply that tracks to a “master” signal. With two resistors, a slave supply is confi gured to ramp function of the master signal ...
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... Shutdown Output In some applications it might be necessary to control the shutdown or RUN/SS pins of the slave supplies. The LTC2927 may not be able to supply the rated 1mA of current from the FB pin when V supply is capable of operating at low input voltages, use the open-drain SDO output to drive the SHDN or RUN/SS pin of the slave supply (see Figure 7) ...
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... M 2. Solve for the pair of resistors that provide the desired ramp rate of the slave supply, assuming no delay. EARLY V IN 0.1μF R ONB RAMP C RAMP R ONA LTC2927 RAMPBUF TRACK GND 2927 F08 Figure 8. Single Supply Application Choose a ramp rate for the slave supply, S supply ramps up coincident with the master signal or with a fi ...
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... APPLICATIO S I FOR ATIO Coincident Tracking Example 1V/DIV A typical application is shown in Figure 10. The master signal is a 3.3V ramp generated by the LTC2927. The slave 1 supply is a 1.8V switching power supply and the slave 2 supply is a 2.5V switching power supply. Both slave supplies track coincidently with the 3.3V ramping master signal ...
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... RAMP 0.1μF 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 1.235V OUT TRACK R R FB1 GND FA1 16.5k 35.7k 0.1μ RAMP 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 0.8V OUT TRACK R FB2 R GND FA2 887k 412k 2927 F12 Figure 12. Ratiometric Tracking Example MASTER 3.3V SLAVE1 1.8V SLAVE2 2.5V 2927fb ...
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... V CC MASTER ON RAMP 3.3V 0.1μF 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 1.235V OUT TRACK R FB1 R FA1 GND 16.5k 35.7k 0.1μ RAMP 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 0.8V OUT TRACK R FB2 R GND FA2 887k 412k 2927 F14 Figure 14. Offset Tracking Example SLAVE1 1.8V SLAVE2 2.5V 2927fb 11 ...
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... CC ON RAMP 0.1μF 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 1.235V OUT TRACK R R FB1 FA1 GND 16.5k 35.7k 0.1μ RAMP 3.3V LTC2927 SDO RUN/SS IN DC/DC RAMPBUF 0.8V OUT TRACK R R FB2 FA2 GND 887k 412k 2927 F16 Figure 16. Supply Sequencing Example MASTER 3.3V SLAVE1 1.8V SLAVE2 2.5V 2927fb ...
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... R ONB R ONA 100k then R ONA Therefore, 138k is chosen. These values must be checked to ensure the supply reaches the LTC2927 minimum op- erating supply voltage of 2.9V before the ON pin is above the minimum threshold. does not RAMPBUF < Load Requirements When the supply is ramped down quickly, either the load or the supply itself must be capable of sinking enough current to support the ramp rate ...
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... In addition, do not route this trace next to signals with fast transition times. In some circumstances it might be advantageous to add a resistor near the feedback node of the slave supply in series with the FB pin of the LTC2927. This resistor must not exceed: MASTER R ...
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... PACKAGE OUTLINE 0.200 REF TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.65 REF 1.22 REF 1.50 – 1.75 2.80 BSC 1.4 MIN (NOTE 4) 0.65 BSC 0.80 – 0.90 1.00 MAX 0.09 – 0.20 (NOTE 3) LTC2927 www.DataSheet4U.com R = 0.115 0.38 ± 0.10 TYP 5 8 0.56 ± 0.05 (2 SIDES) 2.00 ±0.10 (2 SIDES) PIN 1 CHAMFER OF EXPOSED PAD 4 1 0.25 ± 0.05 0.75 ±0.05 0.50 BSC 2.15 ± ...
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... Operates from 1V to 13.5V, Allows Supply Sequencing, Active Current Limiting 1.7V to 16.5V, Active Inrush Limiting, Fast Comparator Floating Supply from –15V, Active Current Limiting, Enables Three DC/DC Converters www.linear.com ● www.DataSheet4U.com High Voltage Supply Application 0.1μ RAMP MASTER C RAMP 0.4μF LTC2927 3.3V SDO RUN/SS IN DC/DC RAMPBUF 1.235V OUT TRACK GND FA 311k 35 ...