Ultralow supply current monitors ideal for portable electronics
(Technology News, 02 Jun 2008 )
Linear Technology Corporation has introduced the LTC2934 and LTC2935, ultralow power supply monitors that only draw 500nA of quiescent current. Battery life is of the utmost importance in portable applications, where it is essential to reduce the amount of supply current the device draws during normal and standby operation. It is important to minimize quiescent current in supporting power components like voltage monitors in an effort to prolong battery life. These LTC2934 and LTC2935 single-channel voltage monitors fulfill these functions in tiny 2mm x 2mm DFN or ThinSOT packages, making them ideal for compact, single-cell applications.
The unique features of the LTC2934 and LTC2935 differentiate them in the low power monitor market and make them excellent choices for single Li+ coin cell, AA, AAA and other compact battery-powered or "green" applications. The LTC2935 has three binary inputs that allow selection of one of eight integrated reset thresholds, from 3.3V down to 2.25V in 150mV increments. The device's internal precision attenuators allow the part to maintain only 500nA of supply current and accuracy. The LTC2934 allows an external resistive divider to finely set the reset threshold anywhere from 1.6V to 6V. The reset thresholds in both devices are +/-1.5% accurate over temperature which helps to minimize supply overdesign. An early warning of a threatening low voltage condition is provided via a power-fail output. The supervisory circuits monitor VCC and pull the reset output low if the supply voltage drops below the configured reset threshold. The LTC2934 includes two reset timeout-periods of 15ms or 200ms, settable via a time-out selection pin, while the LTC2935 offers a fixed 200ms timeout. A manual reset pin is also provided on both devices for optional use of a pushbutton switch to force a system reset.
