Analog Devices Inc./Maxim Integrated

The MAX834/MAX835 micropower voltage monitors contain a 1.204V precision bandgap reference, comparator, and latched output in a 5-pin SOT23 package. Using the latched output prevents deep discharge of batteries. The MAX834 has an open-drain, n-channel output driver, while the MAX835 has a push-pull output driver. Two external resistors set the trip-threshold voltage.The MAX834/MAX835 feature a level-sensitive latch, eliminating the need to add hysteresis to prevent oscillations in battery-load-disconnect applications.ApplicationsBattery-Powered ApplicationsLoad SwitchingPrecision Battery MonitoringThreshold Detectors

The MAX836/MAX837 micropower voltage monitors contain a 1.204V precision bandgap reference and a comparator in a SOT143 package. The MAX836 has an open-drain, N-channel output driver, while the MAX837 has a push-pull output driver. Two external resistors set the trip threshold voltage.ApplicationsBattery-Powered SystemsLoad SwitchingPrecision Battery MonitoringThreshold Detectors

The MAX840/MAX843/MAX844 low-noise, inverting charge-pump power supplies are ideal for biasing GaAsFETs in cellular telephone transmitter amplifiers. They operate with inputs down to 2.5V.The MAX840 offers both a -2V preset output and a -0.5V to -9.4V adjustable output. The MAX843/MAX844 use an external positive control voltage to set the negative output voltage. Input voltage range for all the devices is 2.5V to 10V, and output current is 4mA with VIN> 2.7V. These circuits can operate with small capacitors, as low as 0.22µF.An internal linear regulator reduces the MAX840's output voltage ripple to 1mVp-p. With a well-filtered control voltage (VCTRL), the MAX843/MAX844 also achieve less than 1mVp-p typical output ripple. Supply current is 750µA, and reduces to less than 1µA in shutdown (MAX840/MAX843). The MAX844's unregulated output is active in shutdown, with the charge pump switching at 20kHz. It provides a low-power LCD supply.ApplicationsCell PhonesContinuously Adjustable GaAsFET BiasGaAsFET Power Amplifier ModulesLCD-Bias Contrast ControlPersonal Communicators, PDAsRegulated Negative Power SuppliesWireless Data Loggers