Datasheet LTC3025 (Analog Devices) - 6
| Hersteller | Analog Devices |
| Beschreibung | 300mA Micropower VLDO Linear Regulator |
| Seiten / Seite | 12 / 6 — BLOCK DIAGRAM. APPLICATIONS INFORMATION. Operation (Refer to Block … |
| Dateiformat / Größe | PDF / 182 Kb |
| Dokumentensprache | Englisch |
BLOCK DIAGRAM. APPLICATIONS INFORMATION. Operation (Refer to Block Diagram). Figure 1. LTC3025 Transient Response
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LTC3025
BLOCK DIAGRAM
BIAS 1 REFERENCE SOFT-START IN SHDN 3 6 SHDN 0.4V + – 6μA OUT GND 4 2 ADJ 5 3025 BD
APPLICATIONS INFORMATION Operation (Refer to Block Diagram)
300mA The LTC3025 is a micropower, VLDO (very low dropout) IOUT 0mA linear regulator which operates from input voltages as low as 0.9V. The device provides a high accuracy output that is capable of supplying 300mA of output current with a typical dropout voltage of only 45mV. A single ceramic VOUT capacitor as small as 1μF is all that is required for output AC 20mV/DIV bypassing. A low reference voltage allows the LTC3025 output to be programmed to much lower voltages than available in common LDOs (range of 0.4V to 3. 6V). VIN = 1.5V 100μs/DIV 3025 F01 VOUT = 1.2V V As shown in the Block Diagram, the BIAS input supplies BIAS = 3.6V COUT = 1μF the internal reference and LDO circuitry while all output current comes directly from the IN input for high effi ciency
Figure 1. LTC3025 Transient Response
regulation. The low quiescent supply currents IIN = 4μA, IBIAS = 50μA drop to IIN = 1μA, IBIAS = 0.01μA typical in
Adjustable Output Voltage
shutdown making the LTC3025 an ideal choice for use in The output voltage is set by the ratio of two external resis- battery-powered systems. tors as shown in Figure 2. The device servos the output The device includes current limit and thermal overload to maintain the ADJ pin voltage at 0.4V (referenced to protection. The fast transient response of the follower ground). Thus the current in R1 is equal to 0.4V/R1. For output stage overcomes the traditional tradeoff between good transient response, stability, and accuracy, the current dropout voltage, quiescent current and load transient in R1 should be at least 8μA, thus the value of R1 should response inherent in most LDO regulator architectures. be no greater than 50k. The current in R2 is the current in The LTC3025 also includes overshoot detection circuitry R1 plus the ADJ pin bias current. Since the ADJ pin bias which brings the output back into regulation when going current is typically <10nA, it can be ignored in the output from heavy to light output loads (see Figure 1). voltage calculation. The output voltage can be calculated 3025fd 6
BLOCK DIAGRAM
BIAS 1 REFERENCE SOFT-START IN SHDN 3 6 SHDN 0.4V + – 6μA OUT GND 4 2 ADJ 5 3025 BD
APPLICATIONS INFORMATION Operation (Refer to Block Diagram)
300mA The LTC3025 is a micropower, VLDO (very low dropout) IOUT 0mA linear regulator which operates from input voltages as low as 0.9V. The device provides a high accuracy output that is capable of supplying 300mA of output current with a typical dropout voltage of only 45mV. A single ceramic VOUT capacitor as small as 1μF is all that is required for output AC 20mV/DIV bypassing. A low reference voltage allows the LTC3025 output to be programmed to much lower voltages than available in common LDOs (range of 0.4V to 3. 6V). VIN = 1.5V 100μs/DIV 3025 F01 VOUT = 1.2V V As shown in the Block Diagram, the BIAS input supplies BIAS = 3.6V COUT = 1μF the internal reference and LDO circuitry while all output current comes directly from the IN input for high effi ciency
Figure 1. LTC3025 Transient Response
regulation. The low quiescent supply currents IIN = 4μA, IBIAS = 50μA drop to IIN = 1μA, IBIAS = 0.01μA typical in
Adjustable Output Voltage
shutdown making the LTC3025 an ideal choice for use in The output voltage is set by the ratio of two external resis- battery-powered systems. tors as shown in Figure 2. The device servos the output The device includes current limit and thermal overload to maintain the ADJ pin voltage at 0.4V (referenced to protection. The fast transient response of the follower ground). Thus the current in R1 is equal to 0.4V/R1. For output stage overcomes the traditional tradeoff between good transient response, stability, and accuracy, the current dropout voltage, quiescent current and load transient in R1 should be at least 8μA, thus the value of R1 should response inherent in most LDO regulator architectures. be no greater than 50k. The current in R2 is the current in The LTC3025 also includes overshoot detection circuitry R1 plus the ADJ pin bias current. Since the ADJ pin bias which brings the output back into regulation when going current is typically <10nA, it can be ignored in the output from heavy to light output loads (see Figure 1). voltage calculation. The output voltage can be calculated 3025fd 6