MAX687CSA

MAX687CSA Application Field and Working Principle

The MAX687CSA is a low-dropout (LDO) linear voltage regulator designed to support portable applications, since it offers low quiescent current and excellent line/load regulation, while operating with input voltages as low as 1 V. It is a compact, low-noise, high-accuracy LDO solution, which is useful in both battery operated and non-battery operated products. The MAX687CSA is available in the 2 mm x 2 mm chip-scale package and has a temperature range from -40 °C to +105 °C.

Application Field

The MAX687CSA integrates several features to simplify the application of battery powered applications, such as:

• Low dropout voltage to allow flexibility when selecting the battery and application
• High output current (2 A at low no-load quiescent current) to minimize power dissipation
• Low quiescent current to extend battery life
• High accuracy output voltage (over- and undervoltage protection) to provide reliable operation
• High Ripple rejection ratio to minimize noise interference
• Short-circuit protection, overcurrent protection and overvoltage protection features to prevent any damage to the load
• Wide supply voltage range (1 V to 10 V) to cover a wide range of battery voltage levels
• Wide temperature range (-40 °C to +105 °C) to provide reliable operation across temperature extremes

Working Principle

The MAX687CSA is a low-dropout (LDO) linear voltage regulator. It uses an on-chip voltage reference and an NMOS pass transistor to regulate a low-noise output voltage from a higher input voltage. The device incorporates two error amplifiers (EA) to control the output voltage. The EA is a differential amplifier with two inputs and one output. When the output voltage deviates from the reference voltage, the output of the EA will be driven up or down until the two inputs are equal. The second EA is used to set the overall output voltage and provides a voltage shutdown function.

The MAX687CSA features various features to provide protection against overcurrent, overvoltage and short circuits. The current limit feature prevents excessive current flow during an overload. An internal voltage clamp protects the regulator from excessive input voltages. A temperature shutdown also prevents the device from operating above its safe operating temperature.

The device is optimized for low noise operation, and has an on-chip low-noise voltage reference with a nominal output voltage of 1.225 V and a low-noise internal 2 A pass transistor to reduce the output noise.

In summary, the MAX687CSA is a low-noise, high-accuracy LDO solution for both battery operated and non-battery operated products. It offers excellent line/load regulation and a wide voltage range, low dropout voltage and quiescent current, as well as several protection features to ensure reliability and safety.