lt1940l Linear Technology Corporation, lt1940l Datasheet
lt1940l
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lt1940l Summary of contents
Page 1
... LT1940 regulates a wide variety of power sources, from 4-cell batteries and 5V logic rails to unregulated wall trans- formers, lead acid batteries and distributed-power supplies. The LT1940L is intended to operate from regulated 5V supplies. A current mode PWM architecture provides fast transient response with simple compensation components and cycle-by-cycle current limiting ...
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... LT1940/LT1940L ABSOLUTE AXI U RATI GS (Note 1) V Voltage IN LT1940 .................................................... (–0.3), 25V LT1940L ................................................... (–0.3), 7V BOOST Pin Voltage LT1940 ................................................................ 35V LT1940L ............................................................. 16V BOOST Pin Above SW Pin LT1940 ................................................................ 25V LT1940L ............................................................. 16V PG Pin Voltage LT1940 ................................................................ 25V LT1940L ............................................................... 7V SW Voltage ................................................................V RUN/SS, FB Pins ...................................................... 6V Maximum Junction Temperature .......................... 125 C Operating Temperature Range (Note 2) ...– ...
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... Efficiency 3.3V OUT 100 V = 3.3V OUT L = 3.3 H (SUMIDA CR43-3R3 12V 18V 0.5 1.0 1.5 LOAD CURRENT (A) 1940 G02 LT1940/LT1940L MIN TYP MAX UNITS 150 kHz 1.8 2.4 3.2 A 210 320 1.8 2 2.3 A 0.3 0 125 160 mV 0.22 ...
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... SWITCH CURRENT (A) 1940 G07 Frequency vs Temperature 1.3 1.2 1.1 1.0 0.9 –50 – 100 125 TEMPERATURE ( C) 1940 G10 *Maximum for LT1940L Maximum Load Current 3.3V OUT 1.8 SLOPE COMPENSATION REQUIRES L > 2.2 H FOR V < 7 WITH V = 3.3V IN OUT 1 4 3 2.2 H 1.2 1 ...
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... If neither feature is used, leave these pins unconnected. GND (Pin 17): The Exposed Pad of the package provides both electrical contact to ground and good thermal con- tact to the printed circuit board. The Exposed Pad must be soldered to the circuit board for proper operation. LT1940/LT1940L Minimum Input Voltage OUT 7.5 ...
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... LT1940/LT1940L W BLOCK DIAGRA 2 A RUN/SS2 2 A RUN/SS1 0.75V SLOPE SLAVE OSC CLK + – 0. RUN/ GND Figure 2. Block Diagram of the LT1940 with Associated External Components (One of Two Switching Regulators Shown) The LT1940 is a dual, constant frequency, current mode buck regulator with internal 2A power switches ...
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... The maximum load current that the LT1940 can deliver at 3.3V depends on the accuracy of the 5V input supply. With a low loss inductor (DCR less than 80m ), the LT1940 can deliver 1A for V 1.4A for LT1940/LT1940L is greater than ~2.4V the forward voltage drop of the catch diode is the voltage drop of the internal switch ...
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... Note that this is OUT OUT a restriction on the operating input voltage; the circuit will tolerate transient inputs up to the absolute maximum rating. For the LT1940L, the maximum input voltage is 7V. Inductor Selection and Maximum Output Current A good first choice for the inductor value is )/1 ...
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... F ceramic capacitor in parallel with a low ESR tantalum capacitor. For the electrolytic capacitor, a value larger than 10 F will be required to meet the ESR and ripple current requirements. Because the input capacitor LT1940/LT1940L • This is given by: OUT = I [V • ...
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... LT1940/LT1940L U U APPLICATIO S I FOR ATIO is likely to see high surge currents when the input source is applied, tantalum capacitors should be surge rated. The manufacturer may also recommend operation below the rated voltage of the capacitor. Be sure to place the 1 F ceramic as close as possible to the V the IC for optimal noise immunity ...
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... BOOST pin is less than the maximum specified in the Absolute Maximum Ratings section OUT IN V IN2 > OUT IN 1940 F03 3V Figure 3. Generating the Boost Voltage LT1940/LT1940L D2 C3 BOOST LT1940 OUT IN GND V – BOOST SW IN MAX V 2V BOOST IN ...
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... LT1940/LT1940L U U APPLICATIO S I FOR ATIO The boost circuit can also run directly from a DC voltage that is higher than the input voltage by more than 3V Figure 3d. The diode is used to prevent damage to the LT1940 in case V is held low while V IN2 circuit saves several components (both BOOST pins can be tied to D2) ...
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... RUN/SS1, then output 1 will go low, PG1 will pull down on RUN/SS2, and the LT1940 will enter its low current shutdown state. This disables PG1, and RUN/SS2 ramps up again to enable the LT1940. The circuit will oscillate and pull extra current from the input. LT1940/LT1940L IN 1940fa 13 ...
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... LT1940/LT1940L U U APPLICATIO S I FOR ATIO OFF ON (5a) Channel 2 is Delayed OFF ON OFF2 ON2 (5c) Independent Control of Channel 2 Figure 5. Several Methods of Sequencing the Two Outputs. Channel 1 Starts First. Figure 6. Diode D4 Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output. Shorted Input Protection If the inductor is chosen so that it won’ ...
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... FB pins together and the two V 1940 F08 channels will share the load current. There are several advantages to this two-phase buck regulator. Ripple cur- rents at the input and output are reduced, reducing voltage ripple and allowing the use of smaller, less expensive LT1940/LT1940L GND (7b) ...
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... LT1940/LT1940L U U APPLICATIO S I FOR ATIO capacitors. Although two inductors are required, each will be smaller than the inductor required for a single-phase regulator. This may be important when there are tight height restrictions on the circuit. The Typical Applications section shows circuits with maximum heights of 1.4mm, 1 ...
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... SW1 SW2 D1 FB1 FB2 PG1 PG2 RUN/SS1 RUN/SS2 GND 1nF 1nF D1, D2: MICROSEMI UPS140 OR ON SEMI MBRM140 D3, D4: CENTRAL CMDSH-3 L1: SUMIDA CDRH4D28-3R3 L2: SUMIDA CDRH4D28-4R7 LT1940/LT1940L Start-Up Waveforms > 5V 2V/DIV V OUT1 2V/DIV V OUT2 2V/DIV POWER GOOD 2V/DIV 50 s/DIV D4 OUT2 5V 1. ...
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... LT1940/LT1940L U TYPICAL APPLICATIO 10V TO 25V C3 D3A 4 3.3 H OUT1 3.3V 1.4A 16.5k C1 15k 10. 330pF 100k PGOOD –5V LOAD SHOULD BE LESS THAN 1/2 5V LOAD (SEE DESIGN NOTE 100 16V C3 4.7 F PGOOD D1, D2: MICROSEMI UPS120 D3: BAT-54A L1, L2: SUMIDA CDRH5D18-4R1 C1: TAIYO YUDEN JMK316BJ226ML C3: TAIYO YUDEN EMK325BJ475MN 18 3 ...
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... BSC 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT MILLIMETERS (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE LT1940/LT1940L 22 25V 3mA C10 13V 300mA D5B ...
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... Linear Technology Corporation 20 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com 0. RUN/SS1 BOOST1 1nF 0.1 F RUN/SS2 SW1 PG1 100k PG2 LT1940L V C1 4.7k 1500pF V BOOST2 C2 0.1 F FB1 330pF SW2 FB2 16.5k GND 10k D1, D2: MICROSEMI UPS120 C1: 2X TAIYO YUDEN JMK212BJ106ML ...