Datasheet LT3048 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Low Noise Bias Generator in 2mm × 2mm DFN |
| Pages / Page | 16 / 10 — OPERATION. APPLICATIONS INFORMATION Capacitor Selection. Inductor … |
| Revision | B |
| File Format / Size | PDF / 1.6 Mb |
| Document Language | English |
OPERATION. APPLICATIONS INFORMATION Capacitor Selection. Inductor Selection
Model Line for this Datasheet
- LT3048EDC#TRMPBF LT3048EDC#TRPBF LT3048EDC-12#TRMPBF LT3048EDC-12#TRPBF LT3048EDC-15#TRMPBF LT3048EDC-15#TRPBF LT3048EDC-3.3#TRMPBF LT3048EDC-3.3#TRPBF LT3048EDC-5#TRMPBF LT3048EDC-5#TRPBF LT3048IDC#TRMPBF LT3048IDC#TRPBF LT3048IDC-12#TRMPBF LT3048IDC-12#TRPBF LT3048IDC-15#TRMPBF LT3048IDC-15#TRPBF LT3048IDC-3.3#TRMPBF LT3048IDC-3.3#TRPBF LT3048IDC-5#TRMPBF LT3048IDC-5#TRPBF
Text Version of Document
LT3048 Series
OPERATION
The LT3048 combines a boost regulator with a low drop- fast transient response, and good stability. The error am- out linear regulator to produce a programmable output plifier, A1, regulates BSTOUT (and LDOIN) to 1.1V above from a lower input voltage. The LT3048-15, LT3048-12, LDOOUT or VIN, whichever is higher. LT3048-5, LT3048-3.3 regulate to 15V, 12V, 5V and 3.3V, Regulating 1.1V between LDOIN and LDOOUT allows the respectively. With EN below 0.4V, all circuits are turned linear regulator to provide good transient response and off, Q2 disconnects the load from the input, and current ripple rejection, while maintaining good efficiency. This consumption is less than 1µA. Driving EN high enables the regulation loop also minimizes total power dissipation oscillator and all bias circuits including voltage reference in fault conditions. If the output is overloaded, the linear and regulation amplifiers. regulator will enter current limit, LDOOUT voltage will The boost regulator uses peak current mode operation, decrease. By reducing the boost regulator output voltage, providing cycle-by-cycle current regulation and limiting, the voltage across Q2 will be reduced, limiting dissipation in Q2. Thermal shutdown provides additional protection.
APPLICATIONS INFORMATION Capacitor Selection Inductor Selection
A 4.7μF ceramic capacitor should be sufficient for the A 5.6μH inductor will suffice for most LT3048 applications. boost regulator output bypass. Low ESR (equivalent See Table 2 for recommended inductor values. Smaller series resistance) ceramic capacitors should be used value inductors can be used at the cost of reduced maximum at the outputs of the regulator to minimize the output load current. Figure 2 shows the maximum load current as ripple voltage. Use only X5R or X7R dielectrics, as these a function of output voltage. The inductor’s RMS current materials retain their capacitance over wider voltage and rating must be greater than the maximum input current. temperature ranges better than other dielectrics. To keep efficiency high, the DCR (series resistance) should be minimized. Table 3 lists several vendors.
Table 1. Ceramic Capacitor Manufacturers MANUFACTURER PHONE WEB Table 2. Recommended Inductor Values
Taiyo Yuden (408) 573-4150 www.t-yuden.com
PART # INDUCTANCE
AVX (803) 448-9411 www.avxcorp.com LT3048 5.6μH Murata (714) 852-2001 www.murata.com LT3048-15 10μH LT3048-12 10μH
FB Resistor Network
LT3048-5 4.7μH The output voltage is programmed with a resistor divider LT3048-3.3 3.3μH between the output and FB pin. Choose the 1% resistors according to:
Table 3. Inductor Manufacturers VENDOR URL
⎛ V ⎞ R1= R2 OUT ⎜ − 1⎟ Coilcraft www.coilcraft.com ⎜ ⎟ 1.235V ⎝ ⎠ Sumida www.sumida.com R2 should be 200k or less to avoid bias current errors. Toko www.toko.com Würth Elektronik www.we-online.com Rev B 10 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions LT3048 LT3048-xx LT3048 Block Diagrams Operation Applications Information Package Description Revision History Related Parts
OPERATION
The LT3048 combines a boost regulator with a low drop- fast transient response, and good stability. The error am- out linear regulator to produce a programmable output plifier, A1, regulates BSTOUT (and LDOIN) to 1.1V above from a lower input voltage. The LT3048-15, LT3048-12, LDOOUT or VIN, whichever is higher. LT3048-5, LT3048-3.3 regulate to 15V, 12V, 5V and 3.3V, Regulating 1.1V between LDOIN and LDOOUT allows the respectively. With EN below 0.4V, all circuits are turned linear regulator to provide good transient response and off, Q2 disconnects the load from the input, and current ripple rejection, while maintaining good efficiency. This consumption is less than 1µA. Driving EN high enables the regulation loop also minimizes total power dissipation oscillator and all bias circuits including voltage reference in fault conditions. If the output is overloaded, the linear and regulation amplifiers. regulator will enter current limit, LDOOUT voltage will The boost regulator uses peak current mode operation, decrease. By reducing the boost regulator output voltage, providing cycle-by-cycle current regulation and limiting, the voltage across Q2 will be reduced, limiting dissipation in Q2. Thermal shutdown provides additional protection.
APPLICATIONS INFORMATION Capacitor Selection Inductor Selection
A 4.7μF ceramic capacitor should be sufficient for the A 5.6μH inductor will suffice for most LT3048 applications. boost regulator output bypass. Low ESR (equivalent See Table 2 for recommended inductor values. Smaller series resistance) ceramic capacitors should be used value inductors can be used at the cost of reduced maximum at the outputs of the regulator to minimize the output load current. Figure 2 shows the maximum load current as ripple voltage. Use only X5R or X7R dielectrics, as these a function of output voltage. The inductor’s RMS current materials retain their capacitance over wider voltage and rating must be greater than the maximum input current. temperature ranges better than other dielectrics. To keep efficiency high, the DCR (series resistance) should be minimized. Table 3 lists several vendors.
Table 1. Ceramic Capacitor Manufacturers MANUFACTURER PHONE WEB Table 2. Recommended Inductor Values
Taiyo Yuden (408) 573-4150 www.t-yuden.com
PART # INDUCTANCE
AVX (803) 448-9411 www.avxcorp.com LT3048 5.6μH Murata (714) 852-2001 www.murata.com LT3048-15 10μH LT3048-12 10μH
FB Resistor Network
LT3048-5 4.7μH The output voltage is programmed with a resistor divider LT3048-3.3 3.3μH between the output and FB pin. Choose the 1% resistors according to:
Table 3. Inductor Manufacturers VENDOR URL
⎛ V ⎞ R1= R2 OUT ⎜ − 1⎟ Coilcraft www.coilcraft.com ⎜ ⎟ 1.235V ⎝ ⎠ Sumida www.sumida.com R2 should be 200k or less to avoid bias current errors. Toko www.toko.com Würth Elektronik www.we-online.com Rev B 10 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions LT3048 LT3048-xx LT3048 Block Diagrams Operation Applications Information Package Description Revision History Related Parts
