Datasheet LT3082 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | 200mA Single Resistor Low Dropout Linear Regulator |
| Pages / Page | 20 / 9 — APPLICATIONS INFORMATION. Table 1. 1% Resistors for Common Output Voltages |
| File Format / Size | PDF / 301 Kb |
| Document Language | English |
APPLICATIONS INFORMATION. Table 1. 1% Resistors for Common Output Voltages
Model Line for this Datasheet
- LT3082EDD#PBF LT3082EDD#PBF LT3082EDD#TRPBF LT3082EDD#TRPBF LT3082EST#PBF LT3082EST#PBF LT3082EST#TRPBF LT3082EST#TRPBF LT3082ETS8#PBF LT3082ETS8#TRMPBF LT3082ETS8#TRMPBF LT3082ETS8#TRPBF LT3082ETS8#TRPBF LT3082IDD#PBF LT3082IDD#PBF LT3082IDD#TRPBF LT3082IDD#TRPBF LT3082IST#PBF LT3082IST#PBF LT3082IST#TRPBF LT3082IST#TRPBF LT3082ITS8#PBF LT3082ITS8#TRMPBF LT3082ITS8#TRMPBF LT3082ITS8#TRPBF LT3082ITS8#TRPBF LT3082MPST LT3082MPST#PBF LT3082MPST#PBF LT3082MPST#TR LT3082MPST#TRPBF LT3082MPST#TRPBF
Text Version of Document
LT3082
APPLICATIONS INFORMATION Table 1. 1% Resistors for Common Output Voltages If guard ring techniques are used, this bootstraps any VOUT (V) RSET (k) stray capacitance at the SET pin. Since the SET pin is
1 100
a high impedance node, unwanted signals may couple
1.2 121
into the SET pin and cause erratic behavior. This will
1.5 150
be most noticeable when operating with minimum
1.8 182
output capacitors at full load current. The easiest way
2.5 249
to remedy this is to bypass the SET pin with a small
3.3 332
amount of capacitance from SET to ground; 10pF to
5 499
20pF is suffi cient. Stability and Output Capacitance
With a 10μA current source generating the reference voltage, leakage paths to or from the SET pin can create The LT3082 requires an output capacitor for stability. It errors in the reference and output voltages. High qual- is designed to be stable with most low ESR capacitors ity insulation should be used (e.g., Tefl on, Kel-F). The (typically ceramic, tantalum or low ESR electrolytic). A cleaning of all insulating surfaces to remove fl uxes and minimum output capacitor of 2.2μF with an ESR of 0.5Ω other residues may be required. Surface coating may be or less is recommended to prevent oscillations. Larger necessary to provide a moisture barrier in high humidity values of output capacitance decrease peak deviations environments. and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple Minimize board leakage by encircling the SET pin and individual components powered by the LT3082, increase circuitry with a guard ring that is operated at a potential the effective output capacitor value. For improvement in close to itself. Tie the guard ring to the OUT pin. Guarding transient response performance, place a capacitor across both sides of the circuit board is required. Bulk leakage the voltage setting resistor. Capacitors up to 1μF can be reduction depends on the guard ring width. 10nA of leak- used. This bypass capacitor reduces system noise as well, age into or out of the SET pin and its associated circuitry but start-up time is proportional to the time constant of creates a 0.1% reference voltage error. Leakages of this the voltage setting resistor (R magnitude, coupled with other sources of leakage, can SET in Figure 1) and SET pin bypass capacitor. cause signifi cant offset voltage and reference drift, es- pecially over the possible operating temperature range. Give extra consideration to the use of ceramic capacitors. Figure 2 depicts an example guard ring layout. Ceramic capacitors are manufactured with a variety of di- OUT SET GND 3082 F02
Figure 2. Example Guard Ring Layout for DFN Package
3082f 9
APPLICATIONS INFORMATION Table 1. 1% Resistors for Common Output Voltages If guard ring techniques are used, this bootstraps any VOUT (V) RSET (k) stray capacitance at the SET pin. Since the SET pin is
1 100
a high impedance node, unwanted signals may couple
1.2 121
into the SET pin and cause erratic behavior. This will
1.5 150
be most noticeable when operating with minimum
1.8 182
output capacitors at full load current. The easiest way
2.5 249
to remedy this is to bypass the SET pin with a small
3.3 332
amount of capacitance from SET to ground; 10pF to
5 499
20pF is suffi cient. Stability and Output Capacitance
With a 10μA current source generating the reference voltage, leakage paths to or from the SET pin can create The LT3082 requires an output capacitor for stability. It errors in the reference and output voltages. High qual- is designed to be stable with most low ESR capacitors ity insulation should be used (e.g., Tefl on, Kel-F). The (typically ceramic, tantalum or low ESR electrolytic). A cleaning of all insulating surfaces to remove fl uxes and minimum output capacitor of 2.2μF with an ESR of 0.5Ω other residues may be required. Surface coating may be or less is recommended to prevent oscillations. Larger necessary to provide a moisture barrier in high humidity values of output capacitance decrease peak deviations environments. and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple Minimize board leakage by encircling the SET pin and individual components powered by the LT3082, increase circuitry with a guard ring that is operated at a potential the effective output capacitor value. For improvement in close to itself. Tie the guard ring to the OUT pin. Guarding transient response performance, place a capacitor across both sides of the circuit board is required. Bulk leakage the voltage setting resistor. Capacitors up to 1μF can be reduction depends on the guard ring width. 10nA of leak- used. This bypass capacitor reduces system noise as well, age into or out of the SET pin and its associated circuitry but start-up time is proportional to the time constant of creates a 0.1% reference voltage error. Leakages of this the voltage setting resistor (R magnitude, coupled with other sources of leakage, can SET in Figure 1) and SET pin bypass capacitor. cause signifi cant offset voltage and reference drift, es- pecially over the possible operating temperature range. Give extra consideration to the use of ceramic capacitors. Figure 2 depicts an example guard ring layout. Ceramic capacitors are manufactured with a variety of di- OUT SET GND 3082 F02
Figure 2. Example Guard Ring Layout for DFN Package
3082f 9
