Datasheet LT3506, LT3506A (Analog Devices) - 9
| 制造商 | Analog Devices |
| 描述 | Dual Monolithic 1.6A Step-Down Switching Regulator |
| 页数 / 页 | 24 / 9 — APPLICATIONS INFORMATION. Table 1. Inductors. VALUE. HEIGHT. PART NUMBER. … |
| 文件格式/大小 | PDF / 221 Kb |
| 文件语言 | 英语 |
APPLICATIONS INFORMATION. Table 1. Inductors. VALUE. HEIGHT. PART NUMBER. (μH). ISAT (A). DCR (. (mm). Sumida. Coilcraft. Cooper. Toko
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LT3506/LT3506A
APPLICATIONS INFORMATION
The current in the inductor is a triangle wave with an
Table 1. Inductors
average value equal to the load current. The peak switch
VALUE HEIGHT
current is equal to the output current plus half the peak-to-
PART NUMBER (μH) ISAT (A) DCR (
Ω
) (mm)
peak inductor ripple current. The LT3506 limits its switch
Sumida
current in order to protect itself and the system from CR43-3R3 3.3 1.44 0.086 3.5 overload faults. Therefore, the maximum output current CR43-4R7 4.7 1.15 0.109 3.5 that the LT3506 will deliver depends on the current limit, CDC5d23-2R2 2.2 2.16 0.030 2.5 the inductor value and the input and output voltages. L CDRH5D28-2R6 2.6 2.60 0.013 3.0 is chosen based on output current requirements, output CDRH6D26-5R6 5.6 2.00 0.027 2.8 voltage ripple requirements, size restrictions and effi ciency CDH113-100 10 2.00 0.047 3.7 goals. When the switch is off, the inductor sees the output
Coilcraft
voltage plus the catch diode drop. This gives the peak-to- DO1606T-152 1.5 2.10 0.060 2.0 peak ripple current in the inductor: DO1606T-222 2.2 1.70 0.070 2.0 ΔI DO1608C-332 3.3 2.00 0.080 2.9 L = (1 – DC)(VOUT + VD)/(L • f) DO1608C-472 4.7 1.50 0.090 2.9 where f is the switching frequency of the LT3506 and L DO1813P-682HC 6.8 2.20 0.080 5.0 is the value of the inductor. The peak inductor and switch
Cooper
current is SD414-2R2 2.2 2.73 0.061 1.35 ISWPK = ILPK = IOUT + ΔIL/2. SD414-6R8 6.8 1.64 0.135 1.35 UP1B-100 10 1.90 0.111 5.0 To maintain output regulation, this peak current must be
Toko
less than the LT3506’s switch current limit ILIM. ILIM is at least 2A at low duty cycle and decreases linearly to 1.7A (D62F)847FY-2R4M 2.4 2.5 0.037 2.7 at DC = 0.8. The maximum output current is a function of (D73LF)817FY-2R2M 2.2 2.7 0.03 3.0 the chosen inductor value:
Input Capacitor Selection
IOUT(MAX) = ILIM – ΔIL/2 = 2A•(1 – 0.21•DC) – ΔIL/2 Bypass the input of the LT3506 circuit with a 4.7μF or If the inductor value is chosen so that the ripple current higher ceramic capacitor of X7R or X5R type. A lower is small, then the available output current will be near value or a less expensive Y5V type can be used if there is the switch current limit. One approach to choosing the additional bypassing provided by bulk electrolytic or tan- inductor is to start with the simple rule given above, look talum capacitors. The following paragraphs describe the at the available inductors, and choose one to meet cost or input capacitor considerations in more detail. Step-down space goals. Then use these equations to check that the regulators draw current from the input supply in pulses LT3506 will be able to deliver the required output current. with very fast rise and fall times. The input capacitor is Note again that these equations assume that the inductor required to reduce the resulting voltage ripple at the LT3506 current is continuous. Discontinuous operation occurs and to force this very high frequency switching current when I into a tight local loop, minimizing EMI. The input capaci- OUT is less than ΔIL/2 as calculated above. 3506afc 9
APPLICATIONS INFORMATION
The current in the inductor is a triangle wave with an
Table 1. Inductors
average value equal to the load current. The peak switch
VALUE HEIGHT
current is equal to the output current plus half the peak-to-
PART NUMBER (μH) ISAT (A) DCR (
Ω
) (mm)
peak inductor ripple current. The LT3506 limits its switch
Sumida
current in order to protect itself and the system from CR43-3R3 3.3 1.44 0.086 3.5 overload faults. Therefore, the maximum output current CR43-4R7 4.7 1.15 0.109 3.5 that the LT3506 will deliver depends on the current limit, CDC5d23-2R2 2.2 2.16 0.030 2.5 the inductor value and the input and output voltages. L CDRH5D28-2R6 2.6 2.60 0.013 3.0 is chosen based on output current requirements, output CDRH6D26-5R6 5.6 2.00 0.027 2.8 voltage ripple requirements, size restrictions and effi ciency CDH113-100 10 2.00 0.047 3.7 goals. When the switch is off, the inductor sees the output
Coilcraft
voltage plus the catch diode drop. This gives the peak-to- DO1606T-152 1.5 2.10 0.060 2.0 peak ripple current in the inductor: DO1606T-222 2.2 1.70 0.070 2.0 ΔI DO1608C-332 3.3 2.00 0.080 2.9 L = (1 – DC)(VOUT + VD)/(L • f) DO1608C-472 4.7 1.50 0.090 2.9 where f is the switching frequency of the LT3506 and L DO1813P-682HC 6.8 2.20 0.080 5.0 is the value of the inductor. The peak inductor and switch
Cooper
current is SD414-2R2 2.2 2.73 0.061 1.35 ISWPK = ILPK = IOUT + ΔIL/2. SD414-6R8 6.8 1.64 0.135 1.35 UP1B-100 10 1.90 0.111 5.0 To maintain output regulation, this peak current must be
Toko
less than the LT3506’s switch current limit ILIM. ILIM is at least 2A at low duty cycle and decreases linearly to 1.7A (D62F)847FY-2R4M 2.4 2.5 0.037 2.7 at DC = 0.8. The maximum output current is a function of (D73LF)817FY-2R2M 2.2 2.7 0.03 3.0 the chosen inductor value:
Input Capacitor Selection
IOUT(MAX) = ILIM – ΔIL/2 = 2A•(1 – 0.21•DC) – ΔIL/2 Bypass the input of the LT3506 circuit with a 4.7μF or If the inductor value is chosen so that the ripple current higher ceramic capacitor of X7R or X5R type. A lower is small, then the available output current will be near value or a less expensive Y5V type can be used if there is the switch current limit. One approach to choosing the additional bypassing provided by bulk electrolytic or tan- inductor is to start with the simple rule given above, look talum capacitors. The following paragraphs describe the at the available inductors, and choose one to meet cost or input capacitor considerations in more detail. Step-down space goals. Then use these equations to check that the regulators draw current from the input supply in pulses LT3506 will be able to deliver the required output current. with very fast rise and fall times. The input capacitor is Note again that these equations assume that the inductor required to reduce the resulting voltage ripple at the LT3506 current is continuous. Discontinuous operation occurs and to force this very high frequency switching current when I into a tight local loop, minimizing EMI. The input capaci- OUT is less than ΔIL/2 as calculated above. 3506afc 9