lt3695 Linear Technology Corporation, lt3695 Datasheet
lt3695
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lt3695 Summary of contents
Page 1
... Operation standard PWM operation. with No Load The LT3695 tolerates adjacent pin shorts or an open pin without raising the output voltage above its programmed value. Low ripple Burst Mode operation maintains high effi - ciency at low output currents while keeping output ripple below 15mV in a typical application. Shutdown reduces input supply current to less than 1μ ...
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... PG Voltage ................................................................30V Operating Junction Temperature Range (Notes 4, 5) LT3695E ............................................. –40°C to 125°C LT3695I .............................................. –40°C to 125°C LT3695H ............................................ –40°C to 150°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C ORDER INFORMATION LEAD FREE FINISH ...
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... Not Switching RUN/ Pin Voltage = 800mV 3.6V < V < 36V ±1.5μ 8.06k 29. 158k RT E- and I-Grades H-Grade SYNC = 0V SYNC = 3.3V or Clocked 0V 36V SW IN LT3695 MIN TYP MAX UNITS l 3.4 3.6 l 3.4 4 39.9 0.01 0 160 0.01 0 100 0 –5 2.8 ...
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... The LT3695I is guaranteed over the full –40°C to 125°C operating junction temperature range. The LT3695H is guaranteed over the full –40°C to 150°C operating junction temperature range. 4 ...
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... TEMPERATURE (°C) Maximum Load Current 1.50 TYPICAL 1.25 1.00 0.75 MINIMUM 0.50 V OUT SYNC = 4.7μH SYNC = 2MHz 0. INPUT VOLTAGE (V) LT3695 T = 25°C, unless otherwise noted. A Effi ciency (V = 3.3V, SYNC = 0V) OUT 100 V = 12V 3.3V 90 OUT L = 10μ 800kHz ...
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... LT3695 TYPICAL PERFORMANCE CHARACTERISTICS Switch Current Limit 1.9 1.7 SYNC < 0.3V 1.5 1.3 SYNC > 0.8V OR CLOCKED 1.1 0.9 0.7 0 DUTY CYCLE (%) 3695 G10 BOOST Pin Current 0.25 0.50 0.75 1.00 SWITCH CURRENT (A) 3695 G13 Frequency Foldback 1200 R = 29.4k RT 1000 800 600 400 200 0 0 100 200 300 400 ...
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... Maximum 3.3V OUT L = 10μ 800kHz SYNC = 3. 0.6 0.7 0.8 0.9 1 3695 G29 LT3695 T = 25°C, unless otherwise noted. A Error Amplifi er Output Current –10 –20 –30 –40 –50 –60 1 –200 –100 0 FB PIN ERROR VOLTAGE (mV) ...
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... LT3695 TYPICAL PERFORMANCE CHARACTERISTICS Maximum V for Full Frequency 25˚ 85˚ OUT L = 4.7μ 2MHz SYNC = 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 LOAD CURRENT(A) 3695 G31 Switching Waveforms, Burst Mode Operation V SW 5V/DIV I L 0.2A/DIV V OUT 20mV/DIV 3695 G34 5μs/DIV ...
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... SW (Pin 4): The SW pin is the output of the internal power switch. Connect this pin to the inductor, catch diode and boost capacitor. RUN/SS (Pin 5): The RUN/SS pin is used to put the LT3695 in shutdown mode. Tie to ground to shut down the LT3695. Tie to 2.5V or more for normal operation. RUN/SS also provides a soft-start function ...
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... LT3695 BLOCK DIAGRAM INTERNAL 0.8V REF SYNC 7 RUN/SS 5 SOFT-START 0.720V – GND – OVLO + SLOPE COMP R Q OUT S OSCILLATOR 250kHz-2.2MHz OUTB SYNC DISABLE Burst Mode DETECT ERROR AMP V CLAMP C + – R1 THERMAL BD SHUTDOWN 15 BOOST ...
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... FB pin is at 90% of its regulated value. The PG output is an open-collector transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the LT3695 is enabled and V The LT3695 has an overvoltage protection feature which disables switching action when V cal) during transients ...
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... LT3695 APPLICATIONS INFORMATION FB Resistor Network The output voltage of the LT3695 is programmed with a resistor divider between the output and the FB pin. Choose the resistor values according to: ⎛ ⎞ V OUT = − ⎜ ⎟ ⎝ ⎠ Reference designators refer to the Block Diagram of the LT3695 ...
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... DA pin prevents the switch + V from turning on again if the inductor valley current is above SW 1.6A nominal. In these cases, the inductor peak current is therefore the maximum current limit of the LT3695 plus OFF(MIN) the additional current overshoot during the turn off delay due to minimum on time PEAK ...
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... OUT L(PEAK) the maximum output load current and ΔI tor ripple current. The LT3695 limits its switch current in order to protect itself and the system from overload faults. Therefore, the maximum output current that the LT3695 will deliver depends on the switch current limit, the inductor value and the input and output voltages ...
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... The input capacitor is required to reduce the resulting voltage ripple at the LT3695 and to force this very high frequency switching current into a tight local loop, minimizing EMI. A 2.2μF capacitor is capable of this task, but only placed close to the LT3695 (see the PCB Layout section for more information) ...
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... LT3695 APPLICATIONS INFORMATION Table 3. Capacitor Vendors VENDOR PHONE Panasonic (714) 373-7366 Kemet (864) 963-6300 Sanyo (408) 749-9714 Murata (408) 436-1300 AVX Taiyo Yuden (864) 963-6300 Low ESR is important, so choose one that is intended for use in switching regulators. The ESR should be specifi the supplier, and should be 0.05Ω ...
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... LT3695 due to their piezoelectric nature. When in Burst Mode operation, the LT3695’s switching frequency depends on the load current, and at very light loads the LT3695 can excite the ceramic capacitor at audio frequencies, generating audible noise. Since the LT3695 operates at a lower current limit during Burst Mode operation, the noise is typically very quiet ...
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... Burst Mode operation or pulse-skipping mode which are selected using the SYNC pin. See the Synchronization section for more information. To enhance effi ciency at light loads, the LT3695 can be operated in low ripple Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current ...
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... For proper start-up, the minimum input voltage is also limited by the boost circuit. If the input voltage is ramped slowly, or the LT3695 is turned on with its RUN/SS pin when the output is already in regulation, then the boost capacitor may not be fully charged. Because the boost capacitor is charged ...
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... Figure 7). There is another situation to consider 3695 F05 5ms/DIV in systems where the output will be held high when the input to the LT3695 is absent. This may occur in battery charging applications or in battery backup systems where a battery or some other supply is diode ORed with the V ...
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... To keep thermal resistance low, extend the ground plane as much as possible and add thermal vias under and near the LT3695 to any additional ground planes within the circuit board and on the bottom side. Keep in mind that the thermal design must keep the junctions of the IC below the specifi ...
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... LFPM airfl ow, this resistance can fall by another 25%. Further increases in airfl ow will lead to lower thermal resistance. Because of the large output current capability of the LT3695 possible to dissipate enough heat to raise the junction temperature beyond the absolute maxi- mum. When operating at high ambient temperatures, the maximum load current should be derated as the ambient temperature approaches these maximums ...
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... V will fall below regulation voltage. OUT SYNC V may fall below regulation voltage. A fl oating SYNC pin confi gures the LT3695 for pulse-skipping mode. However, a fl oating SYNC OUT pin is sensitive to noise which can degrade device performance will fall below regulation voltage. ...
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... R IN LOAD pin (if connected Since this causes V OUT the LT3695 stops switching. The resistive divider formed by R3 and must be adjusted for V LOAD to exceed its nominal value at the required maximum input voltage must supply suffi cient current into ...
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... 100k SYNC SYNC C S 100pF LT3695 Protects Circuitry Connecting to SYNC S LT3695 • 0.36 • (1 – MIN is the maximum load current and DC (see Input Voltage Range section for IN(MAX) 3695 F11 MIN 3695f 25 ...
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... LT3695 RT B140 PG DA 17.4k 71.5k SYNC FB GND PGND 330pF 100k 102k f = 500kHz 5V, 2MHz Step-Down Converter 2.2μF ON OFF RUN/SS BOOST 0.22μ LT3695 RT B140 PG DA 13.3k 9.76k SYNC FB GND PGND 680pF 100k 102k f = 2MHz V OUT 3.3V D2 0.9A, V > B140 1A, V > 6. 10μH 0.22μF ...
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... MAX SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3695 8 0.35 REF 1.651 0.102 0.12 REF (.065 .004) DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. DETAIL “B” FOR REFERENCE ONLY 9 NO MEASUREMENT PURPOSE ...
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... High Effi ciency Step-Down DC/DC Converter OUT Linear Technology Corporation 28 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 5V Step-Down Converter 2.2μF ON OFF RUN/SS BOOST 0.22μ LT3695 RT B140 PG DA 16.2k 40.2k SYNC FB GND PGND 470pF 100k 102k f = 800kHz COMMENTS ...