LTC1698 LINER [Linear Technology], LTC1698 Datasheet
LTC1698
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LTC1698 Summary of contents
Page 1
... The LT3781 synchronizes the LTC1698 through a small pulse transformer and the LTC1698 drives a feedback optocoupler to close the feedback loop. Output accuracy of 0.8% and high efficiency over a wide range of load currents are obtained. ...
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... (Note 2) ......................... – 0.3V to 5.3V COMP COMP Power Dissipation .............................................. 500mW Operating Temperature Range LTC1698E (Note 3) ............................ – LTC1698I ........................................... – Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER ...
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... For guaranteed performance to specifications over the – range, the LTC1698I is available. Note 4: All currents into device pins are positive; all currents out of the device pins are negative. All voltages are referenced to ground unless otherwise specified ...
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... LTC1698 W U TYPICAL PERFOR A CE CHARACTERISTICS V vs Temperature FB 1.248 1.242 1.236 1.230 1.224 1.218 50 –50 – 100 125 150 TEMPERATURE ( C) 1698 G01 I Threshold vs Temperature SNS –22 –23.0 –23.5 –24.0 –24.5 –25.0 –25.5 –26.0 –26.5 –27.0 –27.5 –50 –25 ...
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... COMP I = –10mA OPTODRV 0 –50 – 100 125 150 10 TEMPERATURE ( C) LTC1698 V vs Load Current AUX 3.465 3.424 3.383 3.341 3.300 3.259 3.218 3.176 3.135 LOAD CURRENT (mA) ...
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... LTC1698 W U TYPICAL PERFOR A CE CHARACTERISTICS I vs SYNC Frequency VDD 4700pF 3300pF 2200pF 1000pF 100 150 200 250 300 350 400 450 500 f (kHz) SYNC 1698 G19 ...
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... GND (Pin 4): Logic and Signal Ground. GND is referenced to the internal low power circuitry. Careful board layout techniques must be used to prevent corruption of signal ground reference. Connect GND and PGND together di- rectly at the LTC1698. OPTODRV (Pin 5): Optocoupler Driver Output. This pin drives a ground referenced optocoupler through an exter- nal resistor low, OPTODRV pulls low ...
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... It supplies high power without the need of bulky heat sinks, which is often a problem in any space constrained application. The LTC1698 not only provides synchronous drivers for the external MOSFETs, it comes with other housekeeping functions performed on the secondary side of the power supply, all within a single integrated controller ...
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... The pulse transformer T2 synchronizes the primary and secondary MOSFET drivers typical conversion cycle, the primary MOSFETs Q1 and Q2 turn on simultaneously. SG goes low and generates a negative spike at the LTC1698 SYNC input through the pulse transformer. The LTC1698 forces FG to turn on and CG to turn off. Power is delivered to the load through the transformer T1 and the inductor L1 ...
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... Characteristics section. V Regulator DD The bias supply for the LTC1698 is generated by peak rectifying the isolated transformer secondary winding. As shown in Figure 2, the zener diode Z1 is connected from base ground such that the emitter regulated to one diode drop below the zener voltage. R selected to bring Z1 into conduction and also provide base current to Q5 ...
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... During this time interval, the drivers pulse width might be prematurely terminated, and the inductor current flows through the MOSFETs body diode. Once the LTC1698 timer locks to the clocking frequency, the LTC1698 drivers follow the SYNC signal without fail. Figure 5 shows the SYNC time-out wave- ...
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... LTC1698 U U APPLICATIO S I FOR ATIO MARGIN Adjustment The MARGIN input is used for adjusting the programmed output voltage linearly by varying the current flowing into and out of the pin. Forcing 100 A into the pin moves the output voltage 5% higher. Forcing 100 A out of the pin moves the output voltage 5% lower ...
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... C C )• • • • CTR 1 F • • • • LTC1698 + V REF + V REF 20k – – V COMP 1698 F07 and r vary and C . The OUT << ...
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... The bigger the biasing current, the faster the aging. The LTC1698 opto driver is designed to source up to 10mA of current and swing between 0. – ...
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... The pin requires at least a 0.1 F bypass capacitor. MOSFET Selection Two logic-level N-channel power MOSFETs (Q3 and Q4 in Figure 1) are required for most LTC1698 circuits. They are selected based primarily on the on-resistance and body diode considerations. The required MOSFET R be determined based on input and output voltage, allow- able power dissipation and maximum required output current ...
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... For a more detailed discussion on transformer core and winding losses, see Application Note AN19. Inductor Selection The output inductor in a typical LTC1698 circuit is chosen for inductance value and saturation current rating. The 2 ) output inductor in a forward converter operates the same buck regulator ...
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... When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC1698. These items are also illustrated graphically in Figure 9. Check the following for your layout: 1. Keep the power circuit and the signal circuit segre- gated. Place the power circuit, shown in bold, so that the two MOSFET drain connections are made directly at the transformer ...
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... R7 R2 PGND 4 GND I 5 OPTODRV COMP SENSGND MARGIN PWRGD OVPIN FB Figure 9. LTC1698 Layout Diagram BIAS 10k V V BOOST DD CC SYNC GBIAS V COMP 10pF CG LT3710 V CSET 680pF FG I SNS ILCOMP LTC1698 SS VA 10k 0 ...
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... U TYPICAL APPLICATIO S • • • • LTC1698 1698f 19 ...
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... LTC1698 U TYPICAL APPLICATIO S • • • • 20 1698f ...
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... U TYPICAL APPLICATIO S • • • • LTC1698 1698f 21 ...
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... LTC1698 PACKAGE DESCRIPTIO .254 MIN .0165 .0015 RECOMMENDED SOLDER PAD LAYOUT .007 – .0098 (0.178 – 0.249) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" ...
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... N .053 – .069 (1.346 – 1.752) 0 – 8 TYP .014 – .019 (0.355 – 0.483) TYP LTC1698 .386 – .394 (9.804 – 10.008) NOTE .150 – .157 (3.810 – 3.988) ...
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... McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 LT3781/LTC1698 Isolated 5V/30A Converter LT3781/LTC1698 Isolated 3.3V/15A Converter COMMENTS Operation Up to 60V Maximum General Purpose with External Application Resistor 0.4% Initial Voltage Tolerance Operation Up to 60V Maximum ...