Datasheet LTC3541 (Analog Devices) - 9

LTC3541
BLOCK DIAGRAM
2.2μH IOUT(BUCK) = 500mA VIN(MIN) LVOUT + 1.4V 10μF 10 V SW IN 10μF 1 500mA BUCK VIN SW 22pF REF BUCKFB FB 3 GND PGND LVIN 6 VLDO/LINEAR REG VIN LVIN REF REF ENBUCK + LVOUT(MAX) < VIN – 1.4V 2 IOUT = 300mA (VLDO REG) ENVLDO CONTROL IOUT = 30mA (LINEAR REG) 9 LFB LOGIC – MODE LVOUT CNTRL 5 8 GND 2.2μF LFB 4 GND PGND 7 11 3541 F01
Figure 1. LTC3541 Functional Block Diagram OPERATION
The LTC3541 contains a high efficiency synchronous when using the buck regulator to provide the power for buck converter, a very low dropout regulator (VLDO) and both the VLDO and for external loads. a linear regulator. It can be used to provide up to two output voltages from a single input voltage making the With the ENBUCK pin driven to a logic low and ENVLDO LTC3541 ideal for applications with limited board space. driven to a logic high, the LTC3541 enables the linear The combination and configuration of these major blocks regulator, providing a low noise regulated output voltage within the LTC3541 is determined by way of the control at the LVOUT pin while drawing minimal quiescent current pins ENBUCK and ENVLDO as defined in Table 1. from the VIN input pin. This feature allows output voltage LVOUT to be brought into regulation without the presence With the ENBUCK pin driven to a logic high and ENVLDO of the LVIN voltage. driven to a logic low, the LTC3541 enables the buck con- verter to efficiently reduce the voltage provided at the V With the ENBUCK and ENVLDO pins both driven to a IN input pin to an output voltage which is set by an external logic high, the LTC3541 enables the high efficiency buck feedback resistor network. The buck regulator can be con- converter and VLDO regulator, providing dual output oper- figured for Pulse-Skip or Burst Mode operation by driving ation from a single input voltage. When configured in this the MODE pin to a logic high or logic low respectively. The manner, the LTC3541’s auto start-up sequencing feature buck regulator is capable of providing a maximum output will bring the buck output into regulation in a controlled current of 500mA, which must be taken into consideration manner prior to enabling the VLDO regulator without the 3541fb For more information www.linear.com/LTC3541 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information BUCK Regulator VLDO/Linear regulator Applications Information Efficiency Considerations Thermal Considerations Applications Information Pc Board Layout Checklist Design Example Typical Applications Package Description Revision History Related Parts