LT3689 LINER [Linear Technology], LT3689 Datasheet
LT3689
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LT3689 Summary of contents
Page 1
... WDO pulls low if too long of a period passes before a watchdog transition is detected. In window mode, the LT3689 monitors for WDI falling edges grouped too close together or too far apart. L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation ...
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... For more information on tape and reel specifi cations, go to: 2 (Note 1) Operating Junction Temperature Range (Note 3) LT3689E ............................................. –40°C to 125°C LT3689I .............................................. –40°C to 125°C LT3689H ............................................ –40°C to 150°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) MSOP ............................................................... 300°C ...
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... IN Quiescent Current from V IN Quiescent Current from OUT LT3689-5 Quiescent Current from V LT3689-5 Quiescent Current from OUT LT3689 FB Voltage LT3689-5 Output Voltage LT3689 FB Pin Bias Current LT3689 FB Voltage Line Regulation LT3689-5 Output Voltage Line Regulation f Switching Frequency SW t Switch Off-Time SW(OFF) ...
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... The LT3689I is guaranteed over the full –40°C to 125°C operating junction temperature range. The LT3689H is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125° ...
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... SYNC = 3. 0.1 0.2 0.3 0.4 0.5 0.7 LOAD CURRENT (A) Switch Current Limit vs Temperature 2.0 SYNC = LOW 1.5 SYNC = HIGH 1.0 0.5 0 100 –50 – 100 TEMPERATURE (°C) LT3689/LT3689-5 Maximum Load Current, 5V 1.4 TYPICAL 1.2 1.0 0.8 MINIMUM 0.6 0 25° 12μ 1MHz 0 125 150 (V) IN 3689 G05 Maximum Output Current, 3.3V 1 ...
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... LT3689/LT3689-5 TYPICAL PERFORMANCE CHARACTERISTICS BST Pin Current 125° –50° 25° 400 600 800 1000 0 200 SWITCH CURRENT (mA) 3689 G13 Switching Frequency 25° 0.8 1.2 1.6 2 0.4 FREQUENCY (MHz) 3689 G16 ...
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... I L 0.2A/DIV V SW 5V/DIV 5μs/DIV V = 12V, FRONT PAGE APPLICATION 6mA LOAD 0.730 0.725 0.720 0.715 3689 G28 0.710 LT3689/LT3689-5 Boost Diode Forward Voltage 900 800 T = –50°C A 700 600 T = 150°C A 500 400 300 200 100 ...
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... LT3689/LT3689-5 TYPICAL PERFORMANCE CHARACTERISTICS Transient Duration vs POR Comparator Overdrive 800 700 600 500 RESET OCCURS ABOVE THE CURVE 400 300 200 100 0 0.10 1.00 10.00 100.00 POR COMPARATOR OVERDRIVE VOLTAGE AS PERCENTAGE OF RESET THRESHOLD, V (%) RST 3689 G30 Reset Timeout Period 8.2nF POR MURATA: GRM2195C1H822FA01 ...
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... FB: The LT3689 regulates the feedback pin to 0.800V. Con- nect the feedback resistor divider tap to this pin. For the fi xed LT3689-5 output, this pin can be used to connect a phase lead capacitor between the OUT pin and FB pin to optimize transient response. ...
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... LT3689/LT3689-5 BLOCK DIAGRAM INTERNAL 0.8V REF EN/UVLO SYNC SOFT-START V OUT OUT LT3689-5 ERROR AMP ONLY R1 525k FB R2 100k WDE WDI W/T + 80mV FB – – 3. – + SLOPE COMP OSCILLATOR – TRANSITION WATCHDOG DETECT TIMER ADJUSTABLE RESET PULSE GENERATOR 22μ ...
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... WATCHDOG WINDOW MODE LOWER BOUNDARY PERIOD WDL V = OUTPUT VOLTAGE RESET THRESHOLD UV V OUT RST RST POWER-ON RESET TIMING t WDU WATCHDOG TIMING (W/T = HIGH), TIMEOUT MODE t t RST WDU WATCHDOG TIMING (W/T = LOW), WINDOW MODE GOES BELOW V OUT UV LT3689/LT3689-5 t RST t RST 3689 TD 3689fa 11 ...
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... RS fl ip- T Power-On Reset and Watchdog Timer Operation The LT3689 has a power-on reset (POR) comparator that monitors the regulated output voltage. If the output volt error age is below 10% of the regulation value, the RST pin is C pulled low ...
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... LT3689 no longer operates with constant- SW(MAX) 16.9 frequency. The LT3689 enters pulse-skipping mode at 14.7 frequencies higher than f 12.7 tion on the LT3689’s minimum on-time of 130ns. As the 9.53 switching frequency is increased above f 7.5 is required to switch for shorter periods of time to maintain 6.04 the same duty cycle. Delays associated with turning off 4 ...
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... The LT3689 will not switch off at the end of each clock cycle if there is suffi cient voltage across the boost capacitor (C3 in the Block Diagram). Eventually, the voltage on the boost capacitor falls and requires refreshing. Circuitry detects 50mV/DIV 0.5A/DIV 3689 F01 ...
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... This places a limitation on the maximum duty cycle. The maximum duty cycle that the LT3689 can sustain is 90%. From this DC number, the minimum operating voltage MAX ...
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... EMI. A ceramic capacitor is capable of is less OUT this task, but only placed close to the LT3689 and the catch diode (see the PCB Layout section). A second precaution regarding the ceramic input capacitor concerns the maximum input voltage rating of the LT3689. A ceramic input capacitor combined with trace or cable inductance forms a high quality (under damped) tank circuit ...
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... APPLICATIONS INFORMATION LT3689 circuit is plugged into a live supply, the input volt- age can ring to twice its nominal value, possibly exceeding the LT3689’s voltage rating. For a complete discussion, see Linear Technology’s Application Note 88. Output Capacitor and Output Ripple The output capacitor has two essential functions. Along with the inductor, it fi ...
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... F AVE The LT3689 uses current mode control to regulate the (A) (mV) output, which simplifi es loop compensation. In particular, the LT3689 does not require the ESR of the output capaci- 1 530 1 550 tor for stability, allowing the use of ceramic capacitors to achieve low output ripple and small circuit size. Figure 3 ...
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... Figure 5). At higher output loads (above approximately 60mA 12V for the front page application) the LT3689 will be IN running at the frequency programmed by the R and will be operating in standard PWM mode. The transi- tion between PWM and low ripple Burst Mode operation is seamless, and will not disturb the output voltage ...
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... Voltage Range section. For proper start-up, the minimum input voltage is also limited by the boost circuit. If the input voltage is ramped slowly, or the LT3689 is turned on with its EN/UVLO pin when the output is already in regulation, then the boost capacitor may not be fully charged. Because ...
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... This reduces the minimum input voltage to approximately 300mV above V currents, the inductor current is continuous and the duty cycle is limited by the maximum duty cycle of the LT3689, requiring a higher input voltage to maintain regulation. Soft-Start The LT3689 has an internal soft-start that gradually ramps up the switch current limit from about 100mA to the switch’ ...
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... Shutdown and Undervoltage Lockout Figure 9 shows how to add undervoltage lockout (UVLO) to the LT3689. Typically, UVLO is used in situations where the input supply is current limited, or has a relatively high source resistance. A switching regulator draws constant power from the source, so source current increases as source voltage drops ...
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... POR comparator circuit monitor the LT3689 output voltage. The switcher’s output voltage must be above 90% of programmed value for RST not to be as- serted (refer to the Timing Diagram). The LT3689 will assert RST during power-up, power-down and brownout conditions. Once the output voltage rises above the RST threshold, the adjustable reset timer is started and RST is released after the reset timeout period ...
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... LT3689/LT3689-5 APPLICATIONS INFORMATION In both watchdog modes, when WDO is asserted, the reset timer is enabled. Any WDI pulses that appear while the reset timer is running are ignored. When the reset timer expires, the WDO is allowed to go high again. Therefore input is applied to the WDI pin, then the watchdog circuitry produces a train of pulses on the WDO pin ...
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... Figure 13). There is another situation to consider in systems where the output will be held high when the input to the LT3689 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 pin and ground ...
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... EN/UVLO pin is grounded, the SW pin current will drop to essentially zero. However, if the V IN the output is held high, then parasitic diodes inside the LT3689 can pull large currents from the output through the SW pin and the V pin. Figure 14 shows a circuit that IN will run only when the input voltage is present and that protects against a shorted or reversed input ...
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... LT3689. Placing additional vias can reduce thermal resistance further. Because of the large output current capability of the LT3689 possible to dissipate enough heat to raise the junction temperature beyond the absolute maximum of 125°C (150°C for H-grade). When operating at high ...
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... RT C SYNC POR GND = 182ms C5 68nF f = 700kHz 157ms RST 5V, 2MHz Step-Down Converter 1μF V EN/UVLO IN OUT W/T BST WDE WDI SW LT3689-5 WDO RST WDT RT C SYNC POR GND = 182ms C5 68nF f = 2MHz 157ms RST C2 L1 0.1μF 12μH C4 10pF D1 R1 316k 3 ...
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... MAX SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3689/LT3689-5 8 0.35 REF 1.651 0.102 0.12 REF (.065 .004) DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY 9 NO MEASUREMENT PURPOSE ...
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... LT3689/LT3689-5 PACKAGE DESCRIPTION 3.50 0.05 1.45 0.05 (4 SIDES) 2.10 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 0.10 PIN 1 TOP MARK (NOTE 6) NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5 ...
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... DESCRIPTION A 04/10 Added LT3689-5 Fixed Output Voltage Option Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...
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... FAX: (408) 434-0507 ● Watchdog Timing or Output Voltage Failure 3.6V TO 16V 1μF V EN/UVLO TRANSIENT TO 27V IN OUT W/T WINDOW TIMEOUT BST WDE WATCHDOG_DEFEAT μP I/O WDI SW LT3689 WDO RESET RST WDT C RT POR C6 C5 SYNC 68nF 10nF GND t = 182ms t = 157ms RST WDU ...