lt3990 Linear Technology Corporation, lt3990 Datasheet
lt3990
Available stocks
Related parts for lt3990
lt3990 Summary of contents
Page 1
... The V OUT LT3990 is available in small, thermally enhanced 16-pin MSOP and 3mm × 3mm DFN packages. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 0.22µ ...
Page 2
... For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: (Note 1) Operating Junction Temperature Range (Note 2) LT3990E ............................................. –40°C to 125°C LT3990I .............................................. –40°C to 125°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) MS Only ............................................................ 300° ...
Page 3
... Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT3990I is guaranteed over the full –40°C to 125°C operating junction temperature range. The ...
Page 4
... LT3990 Typical perFormance characTerisTics Efficiency 3.3V OUT 12V 24V 36V 48V FRONT PAGE APPLICATION V = 3.3V 30 OUT 576k 20 0.01 0 100 LOAD CURRENT (mA) 3990 G01 No-Load Supply Current 4.0 FRONT PAGE APPLICATION V = 3.3V OUT 3 576k 3.0 2.5 2.0 1.5 1 ...
Page 5
... TEMPERATURE (°C) Minimum Input Voltage 3.3V OUT 5.0 FRONT PAGE APPLICATION V = 3.3V OUT 4.5 TO START TO RUN 4.0 3.5 3.0 2.5 500 0 50 100 150 200 250 LOAD CURRENT (mA) LT3990 T = 25°C, unless otherwise noted. A Switching Frequency 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 125 150 –50 – TEMPERATURE (°C) 3990 G11 ...
Page 6
... LT3990 Typical perFormance characTerisTics Boost Diode Forward Voltage 1.2 1.0 0.8 0.6 0.4 –50°C 25°C 0.2 125°C 150° 100 150 BOOST DIODE CURRENT (mA) 3990 G19 Power Good Threshold –50 – 100 125 150 TEMPERATURE (°C) 3990 G22 Transient Load Response; Load ...
Page 7
... FuncTions (DFN, MSOP) FB (Pin 1/Pins 1, 2): The LT3990 regulates the FB pin to 1.21V. Connect the feedback resistor divider tap to this pin. EN/UVLO (Pin 2/Pin 4): The part is in shutdown when this pin is low and active when this pin is high. The threshold voltage is 1.21V going up with 32mV of hysteresis. Tie shutdown feature is not used ...
Page 8
... The LT3990 contains a power good comparator which trips when the FB pin is at 90% of its regulated value. The PG output is an open-drain 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 LT3990 is enabled and V is above 4.2V. IN ...
Page 9
... Input Voltage Range 45.3 The minimum input voltage is determined by either the LT3990’s minimum operating voltage of 4. its maximum duty cycle (as explained in previous section). The minimum input voltage due to duty cycle is MIN ( where V IN(MIN) ) for a ...
Page 10
... X7R or X5R type. Y5V types have poor performance over temperature and applied voltage, and should not be used. A 1µF to 4.7µF ceramic capacitor is adequate to bypass the LT3990 and will easily handle the ripple current. Note that larger input capacitance is required when a lower switching frequency is used is the voltage drop of the catch diode (~0.7V MHz. The inductor’ ...
Page 11
... The second function is that the output capacitor, along with the inductor, filters the square wave generated by the LT3990 to produce the DC output. In this role it determines the output ripple, so low impedance (at the switching frequency) is important. The output ripple decreases with increasing output capacitance, down to approximately 1mV ...
Page 12
... If the LT3990 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT3990’s rating. This situation is easily avoided (see the Hot Plugging Safely section) ...
Page 13
... IN the absolute maximum rating of the BOOST pin. Enable and Undervoltage Lockout The LT3990 is in shutdown when the EN/UVLO pin is low and active when the pin is high. The rising threshold of the EN/UVLO comparator is 1.21V, with a 32mV hysteresis. This threshold is accurate when lower than 4 ...
Page 14
... MBRS140 V IN SHDN 3990 F06 Figure 7. Diode D4 Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output. It Also Protects the Circuit from a Reversed Input. The LT3990 Runs Only when the Input Is Present GND EN/UVLO V IN GND VIAS TO LOCAL GROUND PLANE VIAS TO V Figure 8 ...
Page 15
... IN input voltage, possibly exceeding the LT3990’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LT3990 into an energized supply, the input network should be designed to prevent this overshoot. See Linear Technology Application Note 88 for a complete discussion. ...
Page 16
... IN C3 0.22µF V BOOST IN L1 LT3990 15µH OFF ON EN/UVLO 47pF GND 536k f = 300kHz 5V Step-Down Converter C3 0.22µF V BOOST IN L1 LT3990 33µH OFF ON EN/UVLO 22pF GND R2 392k 316k f = 400kHz 3990 TA03 V OUT 2.5V 350mA 47µF R2 931k 3990 TA04 ...
Page 17
... BD 1.3M 22pF RT FB 2.2µF GND 392k f = 400kHz Start-Up from High Impedance Input Source 5V/DIV V 2V/DIV 10 12 3990 TA08b LT3990 5V, 2MHz Step-Down Converter C3 0.1µF V BOOST IN L1 LT3990 10µH OFF ON EN/UVLO 22pF GND R2 52.3k 316k f = 2MHz V OUT 5V 350mA 1M 22µF 316k 3990 TA08a ...
Page 18
... LT3990 package DescripTion 3.55 0.05 1.65 0.05 2.15 0.05 (2 SIDES) 0.25 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev B) 0.70 0.05 PACKAGE OUTLINE 0.50 BSC 2.38 0.05 (2 SIDES) 3.00 0.10 1.65 0.10 (4 SIDES) (2 SIDES) 0.75 0.05 0.00 – 0.05 NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). ...
Page 19
... MAX SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3990 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 ...
Page 20
... High Efficiency Micropower Step-Down MAX DC/DC Converter 0 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 1.21V Step-Down Converter 0.22µF V BOOST IN L1 LT3990 15µH OFF ON EN/UVLO 2.2µF GND 536k f = 300kHz 3990 TA09 COMMENTS V : 4.2V to 40V 3mm × ...