Datasheet LT1073 (Analog Devices) - 6
| Fabricante | Analog Devices |
| Descripción | Micropower DC-DC Converter Adjustable and Fixed 5V, 12V |
| Páginas / Página | 17 / 6 — APPLICATIONS INFORMATION Table 1. Component Selection for Step-Up … |
| Formato / tamaño de archivo | PDF / 1.4 Mb |
| Idioma del documento | Inglés |
APPLICATIONS INFORMATION Table 1. Component Selection for Step-Up Converters. INPUT. BATTERY. OUTPUT. INDUCTOR. CAPACITOR
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LT1073
APPLICATIONS INFORMATION Table 1. Component Selection for Step-Up Converters INPUT BATTERY OUTPUT OUTPUT INDUCTOR INDUCTOR CAPACITOR VOLTAGE (V) TYPE VOLTAGE (V) CURRENT (MIN) VALUE (µH) PART NUMBER VALUE (µF) NOTES
1.55-1.25 Single Alkaline 3 60mA 82 G GA10-822K, CB 7300-12 150 1.30-1.05 Single Ni-Cad 3 20mA 180 G GA10-183K, CB 7300-16 47 1.55-1.25 Single Alkaline 5 30mA 82 G GA10-822K, CB 7300-12 100 1.30-1.05 Single Ni-Cad 5 10mA 180 G GA10-183K, CB 7300-16 22 3.1-2.1 Two Alkaline 5 80mA 120 G GA10-123K, CB 7300-14 470 * 3.1-2.1 Two Alkaline 5 25mA 470 G GA10-473K, CB 7300-21 150 * 3.3-2.5 Lithium 5 100mA 150 G GA40-153K, CB 6860-15 470 * 3.1-2.1 Two Alkaline 12 25mA 120 G GA10-123K, CB 7300-14 220 3.1-2.1 Two Alkaline 12 5mA 470 G GA10-473K, CB 7300-21 100 3.3-2.5 Lithium 12 30mA 150 G GA10-153K, CB 7300-15 220 4.5-5.5 TTL Supply 12 90mA 220 G GA40-223K, CB 6860-17 470 * 4.5-5.5 TTL Supply 12 22mA 1000 G GA10-104K, CB 7300-25 100 * 4.5-5.5 TTL Supply 24 35mA 220 G GA40-223K, CB 6860-17 150 * G = GOWANDA CB = CADDELL-BURNS *Add 68Ω from ILIM to VIN
Measuring Input Current at Zero or Light Load
LT1073. The circuit must be “booted” by shorting V2 to Obtaining meaningful numbers for quiescent current and VSET. After the LT1073 output voltage has settled, dis- efficiency at low output current involves understanding connect the short. Input voltage is V2 and average input how the LT1073 operates. At very low or zero load current, current can be calculated by this formula: the device is idling for seconds at a time. When the output voltage falls enough to trip the comparator, the power IIN = V2– V1 100Ω switch comes on for a few cycles until the output voltage rises sufficiently to overcome the comparator hysteresis.
Inductor Selection
When the power switch is on, inductor current builds up to hundreds of milliamperes. Ordinary digital multimeters A DC/DC converter operates by storing energy as magnetic are not capable of measuring average current because flux, in an inductor core and then switching this energy of bandwidth and dynamic range limitations. A different into the load. Since it is flux, not charge, that is stored, approach is required to measure the 100µA off-state and the output voltage can be higher, lower, or opposite in 500mA on-state currents of the circuit. polarity to the input voltage by choosing an appropriate switching topology. To operate as an efficient energy 1MΩ transfer element, the inductor must fulfill three require- 12V ments. First, the inductance must be low enough for the 1µF* inductor to store adequate energy under the worst-case – 100Ω condition of minimum input voltage and switch ON time. LTC1050 LT1073 V1 V2 CIRCUIT The inductance must also be high enough so that maxi- + + 1000µF mum current ratings of the LT1073 and inductor are not VSET *NONPOLARIZED 1073 F01 exceeded at the other worst-case condition of maximum
Figure 1. Test Circuit Measures No-Load
input voltage and ON time. Additionally, the inductor
Quiescent Current of LT1073 Converter
core must be able to store the required flux, i.e., it must not saturate. At power levels general y encountered Quiescent current can be accurately measured using the with LT1073-based designs, small axial-lead units with circuit in Figure 1. VSET is set to the input voltage of the Rev B 6 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagrams Operation Applications Information Typical Applications Package Description Typical Application Related Parts
APPLICATIONS INFORMATION Table 1. Component Selection for Step-Up Converters INPUT BATTERY OUTPUT OUTPUT INDUCTOR INDUCTOR CAPACITOR VOLTAGE (V) TYPE VOLTAGE (V) CURRENT (MIN) VALUE (µH) PART NUMBER VALUE (µF) NOTES
1.55-1.25 Single Alkaline 3 60mA 82 G GA10-822K, CB 7300-12 150 1.30-1.05 Single Ni-Cad 3 20mA 180 G GA10-183K, CB 7300-16 47 1.55-1.25 Single Alkaline 5 30mA 82 G GA10-822K, CB 7300-12 100 1.30-1.05 Single Ni-Cad 5 10mA 180 G GA10-183K, CB 7300-16 22 3.1-2.1 Two Alkaline 5 80mA 120 G GA10-123K, CB 7300-14 470 * 3.1-2.1 Two Alkaline 5 25mA 470 G GA10-473K, CB 7300-21 150 * 3.3-2.5 Lithium 5 100mA 150 G GA40-153K, CB 6860-15 470 * 3.1-2.1 Two Alkaline 12 25mA 120 G GA10-123K, CB 7300-14 220 3.1-2.1 Two Alkaline 12 5mA 470 G GA10-473K, CB 7300-21 100 3.3-2.5 Lithium 12 30mA 150 G GA10-153K, CB 7300-15 220 4.5-5.5 TTL Supply 12 90mA 220 G GA40-223K, CB 6860-17 470 * 4.5-5.5 TTL Supply 12 22mA 1000 G GA10-104K, CB 7300-25 100 * 4.5-5.5 TTL Supply 24 35mA 220 G GA40-223K, CB 6860-17 150 * G = GOWANDA CB = CADDELL-BURNS *Add 68Ω from ILIM to VIN
Measuring Input Current at Zero or Light Load
LT1073. The circuit must be “booted” by shorting V2 to Obtaining meaningful numbers for quiescent current and VSET. After the LT1073 output voltage has settled, dis- efficiency at low output current involves understanding connect the short. Input voltage is V2 and average input how the LT1073 operates. At very low or zero load current, current can be calculated by this formula: the device is idling for seconds at a time. When the output voltage falls enough to trip the comparator, the power IIN = V2– V1 100Ω switch comes on for a few cycles until the output voltage rises sufficiently to overcome the comparator hysteresis.
Inductor Selection
When the power switch is on, inductor current builds up to hundreds of milliamperes. Ordinary digital multimeters A DC/DC converter operates by storing energy as magnetic are not capable of measuring average current because flux, in an inductor core and then switching this energy of bandwidth and dynamic range limitations. A different into the load. Since it is flux, not charge, that is stored, approach is required to measure the 100µA off-state and the output voltage can be higher, lower, or opposite in 500mA on-state currents of the circuit. polarity to the input voltage by choosing an appropriate switching topology. To operate as an efficient energy 1MΩ transfer element, the inductor must fulfill three require- 12V ments. First, the inductance must be low enough for the 1µF* inductor to store adequate energy under the worst-case – 100Ω condition of minimum input voltage and switch ON time. LTC1050 LT1073 V1 V2 CIRCUIT The inductance must also be high enough so that maxi- + + 1000µF mum current ratings of the LT1073 and inductor are not VSET *NONPOLARIZED 1073 F01 exceeded at the other worst-case condition of maximum
Figure 1. Test Circuit Measures No-Load
input voltage and ON time. Additionally, the inductor
Quiescent Current of LT1073 Converter
core must be able to store the required flux, i.e., it must not saturate. At power levels general y encountered Quiescent current can be accurately measured using the with LT1073-based designs, small axial-lead units with circuit in Figure 1. VSET is set to the input voltage of the Rev B 6 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagrams Operation Applications Information Typical Applications Package Description Typical Application Related Parts