ltm8040 Linear Technology Corporation, ltm8040 Datasheet
ltm8040
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ltm8040 Summary of contents
Page 1
... Unique PWM circuitry allows a dimming range of 400:1, avoiding the color shift normally associated with LED current dimming. With its wide input range 36V, the LTM8040 regu- lates a broad array of power sources, from 4-cell batteries and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies ...
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... LTM8040EV#PBF LTM8040V LTM8040IV#PBF LTM8040V Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi ...
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... The LTM8040I is guaranteed to meet specifi cations over the full –40°C to 125°C internal operating temperature range. Note that the maximum internal temperature is determined by specifi c operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors ...
Page 4
... LTM8040 TYPICAL PERFORMANCE CHARACTERISTICS Minimum Running Voltage vs Output Voltage 2. LEDs LOAD 4 0.5A LOAD 0.1A LOAD OUTPUT VOLTAGE 8040 G07 Minimum Start Voltage vs Load 3. LEDs 14 SINGLE LED 2 LEDs 12 3 LEDs 200 400 600 800 ...
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... I LOAD PIN FUNCTIONS LEDA (Bank 1): This pin is the regulated current source of the LTM8040. Connect the anode of the LED string to this pin. This voltage must be at least 2.4V for accurate current regulation. SHDN (Pin L4): The SHDN pin is used to shut down the switching regulator and the internal bias circuits. The 2 ...
Page 6
... GND (Bank 2): Tie all GND pins directly to a local ground plane. These pins serve as both signal and power return to the LTM8040 μModule, as well as providing the primary thermal path for heat dissipation within the unit. See the Applications Information section for more information about heat-sinking and printed circuit board layout ...
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... If the SHDN pin is tied to ground, the LTM8040 is shut down and draws minimal current from the input source . If the SHDN pin exceeds 1.5V, the internal bias ...
Page 8
... Open LED Protection The LTM8040 has internal open LED circuit protection. If the LED is absent or fails open, the LTM8040 clamps the voltage on the LEDA pin to 14V. The switching regulator then skips cycles to limit the input current. The input current and output voltage during an open LED condition is shown in the Typical Performance Characteristics section ...
Page 9
... F02a Figure 2b. BIAS May be Tied to XV LTM8040 LEDA IN SHDN C1 LPWR 2.2μF V BIAS ADJ PWM RT GND LPWR are Suitable LTM8040 and BIAS is IN LTM8040 2.7V V LEDA IN SHDN C1 LPWR 2.2μF V BIAS ADJ PWM RT GND 8040 F02b if LPWR is Below 2.6V IN 2.7V 3.3V RED LED 8040 F02c ...
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... When the PWM pin goes high again, the LED current returns rapidly to its previous on state. This fast settling time allows the LTM8040 to maintain LED current regulation with PWM pulse widths as short as 40μ also possible to not use an external ...
Page 11
... In addition, it takes more input voltage to initially start than is required for continuous operation. This start voltage is also dependent on whether turn-on is controlled by the LTM8040’s SHDN pin or UVLO (that is, the SHDN pin is tied See Typical Performance Characteristics for IN details ...
Page 12
... Layout Hints Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of in- tegration of the LTM8040. The LTM8040 is nevertheless a switching power supply, and care must be taken to minimize EMI and ensure proper operation. Even with the high level of integration, you may fail to achieve specifi ...
Page 13
... LTM8040 f RADJ BIAS CONNECTION MIN MAX 0.50M 154 2.8V to 25V source 0.50M 154 LPWR 0.50M 154 LPWR 0.50M 154 LPWR 0.50M 453 2.8V to 25V source 0.70M 453 LPWR ...
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... Step Down 350mA Drive with Three Series Red LEDs LTM8040 LEDA IN SHDN LPWR 1μF BIAS 2.87k ADJ PWM RT GND 137k 750kHz Step Down 1A Drive with Three White Series LEDs LTM8040 LEDA IN SHDN LPWR 1μF BIAS ADJ PWM RT GND 137k 750kHz 2. 8040 TA02 ...
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... LGA Package 66-Lead (15mm × 9mm × 2.82mm) (Reference LTC DWG # 05-08-1810 Rev Ø bbb 6.350 5.080 3.810 2.540 1.5875 1.270 0.9525 0.000 1.270 2.540 3.810 5.080 6.350 LTM8040 8040p 15 ...
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... DC/DC μModule LTM8023 2A, 36V DC/DC μModule PolyPhase is a trademark of Linear Technology Corporation Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 Step Down 1A Drive with Four Series Red LEDs LTM8040 * IN V LEDA IN SHDN LPWR 1μF BIAS ADJ ...