LTC3251 LINER [Linear Technology], LTC3251 Datasheet
LTC3251
Available stocks
Related parts for LTC3251
LTC3251 Summary of contents
Page 1
... Super Burst Low operating current ( Burst Mode operation Super Burst mode operation) and low external parts count make the LTC3251/LTC3251-1.2/LTC3251-1.5 ideally suited for space-constrained battery-powered applications. The parts are short-circuit and overtempera- ture protected, and are available in a thermally enhanced 10-pin MSOP package ...
Page 2
... EXPOSED PAD IS GND (PIN 11), MUST BE SOLDERED TO PCB LTB4 T = 125 C, JMAX The denotes the specifications which apply over the full operating = 3.6V 1.5V for LTC3251, all capacitors ceramic, unless otherwise noted. OUT CONDITIONS (Notes 4,5) (Note 0mA OUT MD0 MD1 ...
Page 3
... Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Based on long term current density limitations. Note 3: The LTC3251E is guaranteed to meet specified performance from Specifications over the – operating temperature range are assured by design, characterization and correlation with statistical process controls ...
Page 4
... LTC3251/ LTC3251-1.2/LTC3251-1 TYPICAL PERFOR A CE CHARACTERISTICS No Load Supply Current vs Supply Voltage (Super Burst Mode Operation – 2.7 4.2 4.7 5.2 3.2 3.7 V (V) IN 3251 G02 1.5V Output Voltage vs Supply Voltage (Super Burst Mode Operation) 1. 0mA A 1.58 10mA 40mA 1 ...
Page 5
... V (V) IN 3251 G11 Output Transient Response (Burst Mode Operation) 450mA 50mA V OUT (AC s/DIV A 3251 G14 X5R 6.3V OUT V = 1.5V OUT LTC3251-1.5 Output Voltage Ripple SPECT SPECT 200ns/DIV A 3251 G16 X5R 6.3V OUT I = 500mA OUT V = 1.5V OUT OUT 20mV/DIV (AC) ...
Page 6
... V low ESR ceramic capacitor to GND (C Capacitor Selection for capacitor size requirements (Pin 8): Flying Capacitor 2 Positive Terminal (C2). FB (Pin 10) (LTC3251): Feedback Input Pin. An output divider should be connected from V the output voltage. may be IN MODE (Pin 10) (LTC3251-1.2/LTC3251-1.5): Spread with low ESR Spectrum Operation Mode Pin ...
Page 7
... IN 2 BURST DETECT CIRCUIT LTC3251-1.2/LTC3251-1.5 W LTC3251-1.2/ LTC3251-1.5 ONLY MD0 MD1 MODE SWITCH CONTROL SPREAD SPECTRUM AND SOFT-START OSCILLATOR CHARGE PUMP 1 CHARGE PUMP 2 – + GND 5 11 LTC3251 – INTERNAL ON LTC3251-1.2/ LTC3251-1.5 V OUT – 3251 BD 32511215fa 7 ...
Page 8
... C. It will re-enable the OUT charge pumps once the junction temperature drops back to approximately 150 C. The LTC3251 will cycle in and out of thermal shutdown without latch-up or damage until the overstress condition is removed. Long term overstress via ...
Page 9
... O Low Current Burst Mode Operation To improve efficiency at low output currents, a Burst Mode function is included in the LTC3251 family of parts. An output current sense is used to detect when the required output current drops below an internally set threshold (50mA typ). When this occurs, the part shuts down the internal oscillator and goes into a low current operating = 1 ...
Page 10
... Ultralow Current Super Burst Mode Operation To further optimize the supply current for low output current requirements, a Super Burst mode operaton is included in the LTC3251 family of parts. This mode is very similar to Burst Mode operation, but much of the internal circuitry and switch is shut down to further reduce supply current ...
Page 11
... OPERATIO (Refer to Block Diagram) Further output noise reduction can be achieved by filtering the LTC3251 output through a very small series inductor as shown in Figure 4. A 10nH inductor will reject the fast output transients caused by the blanking period. The 10nH inductor can be fabricated on the PC board with about 1cm (0.4" ...
Page 12
... PC board considerably. Using this method a 40 C/W should be achieved. Power Efficiency The power efficiency ( ) of the LTC3251 family is approxi mately double that of a conventional linear regulator. This occurs because the input current for a 2-to-1 step-down charge pump is approximately half the output current ...
Page 13
... U OPERATIO (Refer to Block Diagram) At moderate to high output power the switching losses and quiescent current of the LTC3251 family is negligible and the expression above is valid. For example with V 3.6V 200mA and V regulating to 1.5V the OUT OUT measured efficiency is 81% which is in close agreement with the theoretical 83.3% calculation. ...
Page 14
... OUT – – 73.2k 5,11 10 GND FB 536k 3.3V to 1.4V Conversion, Continuous Spread Spectrum Operation with Shutdown OFF MD0 MD1 LTC3251 OUT 3. – – 5,11 10 GND 0.9V OUT ...
Page 15
... DETAIL “A” 0 – 6 TYP 0.53 0.152 1.10 (.021 .006) (.043) MAX DETAIL “A” SEATING PLANE 0.17 – 0.27 (.007 – .011) TYP LTC3251/ BOTTOM VIEW OF EXPOSED PAD OPTION 2.06 0.102 (.081 .004) 1 1.83 0.102 (.072 .004) 10 0.497 0.076 (.0196 .003 REF 3 ...
Page 16
... DC/DC Converter LTC3440 600mA (I ), 2MHz, Synchronous OUT Buck-Boost DC/DC Converter LTC3441 1. 1MHz, Synchronous OUT Buck-Boost DC/DC Converter Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 MD0 MD1 LTC3251-1 OUT – ...