Design Note 465 LINEAR Ultralow Power Boost Converters Require Only 8.5μA of Standby Quiescent Current

Ultralow Power Boost Converters Require Only 8.5µA of Standby Quiescent Current Design Note 465 Xiaohua Su Introduction effi ciency over a wide load range. Figures 2 and 3 show

Industrial remote monitoring systems and keep-alive effi ciency and output peak-to-peak ripple for Figure 1’s circuits spend most of their time in standby mode. Many circuit. Output ripple voltage is less than 10m V despite of these systems also depend on battery power, so power the circuit’s small (0.1μF) output capacitor.

supply effi ciency in standby state is very important to

The soft-start feature is implemented by connecting an

maximize battery life. The LT®8410/-1 high effi ciency

external capacitor to the VREF pin. If soft-start is not

boost converter is ideal for these systems, requiring

needed, the capacitor can be removed. Output voltage

FF IC IE

only 8.5μA of quiescent current in standby mode. The

is set by a resistor divider from the VREF pin to ground

device integrates high value (12.4M/0.4M) output feed-

with the center tap connected to the FBP pin, as shown

back resistors, signifi cantly reducing input current when

in Figure 1. The FBP pin can also be biased directly by

the output is in regulation with no load. Other features

an external reference.

include an integrated 40V switch and Schottky diode,

The SHDN pin of the LT8410/-1 can serve as an on/off

output disconnect with current limit, built in soft-start,

switch or as an undervoltage lockout via a simple resistor

overvoltage protection and a wide input range, all in a

divider from VCC to ground.

tiny 8-pin 2mm × 2mm DFN package.

Application Example Ultralow Quiescent Current Boost Converter with Output Disconnect

Figure 1 details the LT8410 boost converter generat-

ing a 16V output from a 2.5V-to-16V input source. The Low quiescent current in standby mode and high value LT8410/-1 controls power delivery by varying both the integrated feedback resistors allow the LT8410/-1 to peak inductor current and switch off time. This control regulate a 16V output at no load from a 3.6V input with

scheme results in low output voltage ripple as well as high L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

VIN = 12V

2.5V to 16V

VIN = 5V

VIN = 3.6V

SW CAP

VOUT = 16V

VCC VOUT LT8410 0.1μF* CHIP VREF SHDN

ENABLE

GND FBP 0.1μF

*HIGHER VALUE CAPACITOR IS REQUIRED 0.01 100100.1

WHEN THE VIN IS HIGHER THAN 5V 8410-1 TA01a LOAD CURRENT (m A) 8410-1 TA03

Figure 1. 2.5V-16V To 16V Boost Converter Figure 2. Effi ciency vs Load Current For Figure 1 Converter