LTC3561 LINER [Linear Technology], LTC3561 Datasheet
LTC3561
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LTC3561 Summary of contents
Page 1
... The output voltage is adjustable from 0.8V to 5V. Internal synchronous 0.11Ω power switches with 1.4A peak current ratings provide high efficiency. The LTC3561’s current mode architecture and external compensation allow the transient response to be optimized over a wide range of loads and output capacitors ...
Page 2
... IN temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: The LTC3561 is tested in a feedback loop which servos V midpoint for the error amplifier (V Note 4: Dynamic supply current is higher due to the internal gate charge being delivered at the switching frequency. ...
Page 3
... ELECTRICAL CHARACTERISTICS Note calculated from the ambient T and power dissipation according to the following formula: LTC3561EDD • 43°C/ Note 6: Switch on-resistance is guaranteed by correlation to wafer level measurements. Note 7: 4MHz operation is guaranteed by design but not production tested and is subject to duty cycle limitations (see Applications Information). ...
Page 4
... LTC3561 W U TYPICAL PERFOR A CE CHARACTERISTICS Frequency Variation vs Temperature –2 –4 –6 –8 –10 –50 – 100 TEMPERATURE (°C) 3561 G10 CTIO S SHDN/R (Pin 1): Combination Shutdown and Timing T Resistor Pin. The oscillator frequency is programmed by connecting a resistor from this pin to ground ...
Page 5
... IN 6 0.8V REFERENCE OPERATIO The LTC3561 uses a constant frequency, current mode architecture. The operating frequency is determined by the value of the R resistor. T The output voltage is set by an external divider returned to the V pin. An error amplifier compares the divided FB output voltage with a reference voltage of 0.8V and adjusts the peak inductor current accordingly ...
Page 6
... The choice of which style induc- T tor to use often depends more on the price vs size require- ments and any radiated field/EMI requirements than on what the LTC3561 requires to operate. Table 1 shows some typical surface mount inductors that work well in LTC3561 applications. ≈ 6.67 • (V ...
Page 7
... Ceramic capacitors have the lowest ESR and cost but also have the lowest capacitance density, a high voltage and temperature coefficient and exhibit audible LTC3561 ) Selection OUT is driven by the required ESR to OUT OUT ⎛ ...
Page 8
... Other capacitor types include the Panasonic specialty polymer (SP) capacitors. In most cases, 0.1µF to 1µF of ceramic capacitors should also be placed close to the LTC3561 in parallel with the main capacitors for high frequency decoupling. Ceramic Input and Output Capacitors Higher value, lower cost ceramic capacitors are now becoming available in smaller case sizes ...
Page 9
... V by gradually increasing IN the peak inductor current. Power supply sequencing can also be accomplished using this pin. The LTC3561 has an internal digital soft-start which steps up a clamp on I over 1024 clock cycles, as can be seen in Figure 3. The soft-start time can be increased by ramping the voltage on I during start-up as shown in Figure 2(c) ...
Page 10
... ...) where L1, L2, etc. are the individual losses as a percentage of input power. Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC3561 circuits: 1) LTC3561 V , the load step capa- 2) switching losses The V IN electrical characteristics which excludes MOSFET driver and control currents ...
Page 11
... RISE AMBIENT example, consider the case when the LTC3561 is in dropout at an input voltage of 3.3V with a load current of 1A. From the Typical Performance Characteristics graph of Switch Resistance, the R BOT)(1 – DC) DS(ON) P-channel switch is 0.11Ω. Therefore, power dissipated by the part is: ...
Page 12
... R2 is then 887k. The compensation should be optimized for these compo- nents by examining the load step response but a good place to start for the LTC3561 is with a 13kΩ and 1000pF filter. The output capacitor may need to be increased depending on the actual undershoot during a load step. ...
Page 13
... R4 R1A R1B R1C 324k 280k 412k 698k 3561 F07a L1 D1 2.2µH 1. 22pF 100k 22µ 200k 324k 3561 TA02 LTC3561 Efficiency vs Load Current 100 3. 2.5V 10 OUT f = 1MHz 100 1000 LOAD CURRENT (mA) ...
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... L1: TOKO A916CY-4R7M L2: TOKO A914BYW-2R2M (D52LC SERIES) Efficiency and V Ripple OUT 100 V = 2.4V IN 3. 100 I (mA) LOAD 3561 TA07 C5 10µ 2.2µH LTC3561 887k 22µF V SHDN 10pF SGND PGND 412k 3561 TA06 1000 V OUT 1.8V/1A 3561f ...
Page 15
... 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. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON TOP AND BOTTOM OF PACKAGE LTC3561 R = 0.115 TYP 5 8 3.00 ±0.10 1.65 ± ...
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... LTC3561 U TYPICAL APPLICATIO 1mm Height, 2MHz, Li-Ion to 1.8V Converter V IN 2.63V 4. 10µF LTC3561 SGND PGND SHDN/R 10k 47pF C3 1000pF C1, C2: AVX 08056D106M L1: TDK VLF3010ATIR5NIRZ RELATED PARTS PART NUMBER DESCRIPTION LTC1879 1. 550kHz Synchronous Step-Down DC/DC Converter OUT LTC3405/LTC3405A 300mA ( ...