MAX690TEPA+

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MAX690TEPA+ Application Field and Working Principle
The Supervisors PMIC, MAX690TEPA+ is a programmable voltage supervisory IC for system power management. It includes two standard digital software-controlled voltage monitoring circuits that operate from 0.4V to 5.25V. In addition, MAX690TEPA+ has an adjustable precision 2.5V reference to support up to four user-programmable reference settings from 0.8V to 5.25V. This advanced programmable circuit makes possible to monitor power supplies independently and accurately with significantly improved power sequencing capability. Moreover, a few optional features are available, such as noise-margin selection, power-fail warning, sequenced system reset and built-in brownout protection.

The primary application fields of MAX690TEPA+ are wide. It can be used as a voltage supervisor in systems offering multiple power rails, providing low-voltage microprocessors and memory with the safety of regulated and sequenced power supply. For microprocessor-driven systems, MAX690TEPA+ helps detect and account for voltage dropouts due to excessive current demands, providing reliable system protection and efficient low power operation. This IC also provides the indispensable protection needed for systems powered from high-transient batteries, such as those used in portable devices. Furthermore, MAX690TEPA+ can be used in many other applications as a system supervisor and voltage monitor, such as systems receiving intermittent power from a wall AC adapter or in-person monitoring systems using trucks.

Figure 1 illustrates the block diagram of MAX690TEPA+. As the Fig. 1 depicts, it includes two voltage supply layers: Input Supply and Reference Supply, an on-chip band gap reference, Programmable Sequencer, and Output Monitor. The Voltage Input layer takes in five pins representing the Voltage+ and Voltage- inputs, as well as the Oscillator, ENABLE/DISABLE and ENHIBIT inputs. Both the ENABLE/DISABLE and ENHIBIT pins have TTL voltage levels. The Reference Supply contains an adjustable output voltage of 2.5V, which can be programmed to have four user-programmable outputs from 0.8V to 5.25V. The Programmable Sequencer controls the voltage monitors, while the Output Monitor gives out a 3.2V reset pulse when the Voltage+ Input goes below the user-defined threshold voltage.

In terms of its working principle, MAX690TEPA+ is quite easy to understand. On power-up, the ENABLE/DISABLE pin is activated, which causes the Voltage+ input to enter the supply domain. Following that, the on-chip band gap reference voltage is compared with the Voltage+ input. When the Voltage+ input is greater than the reference voltage, the Output Monitor is released from reset mode and functions as a low-active open collector reset signal. The Output Monitor also has a Reset Mode changing feature that changes the reset signal state in response to a negative transition of the Voltage+ input level. If the Voltage+ goes to zero, the Output Monitor releases its reset mode and the reset signal returns to its low-active open collector reset state. This reset signal can be extended to the software layer for a controlled shutdown of the system.

In summary, MAX690TEPA+ is an advanced version of a voltage supervisory IC, providing multiple advanced features. It offers high accuracy and noise margin margins and a broad operating range from 0.4 to 5.25 volts, with improved power sequencing feature. The primary applications range from low-voltage microprocessors to portable devices supported with battery power. MAX690TEPA+ provides reliable system protection and efficient low power operation, and its working principle is easy to understand.

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