Abstract: In Telecom systems such as Radio Link and Point to Point, the point-to-mulTIpoint controller shuts the system off in the event of a fault. When the fault is brief (for instance, a momentary short circuit due to measurement and calibraTIon acTIons), the auto-retry controller attempts to restart the system.
The MAX1637 (IC2 in Figure 1) is a popular device for telecom applicaTIons. It offers PWM operation, small size, high MOSFET-drive capability, wide VIN and VOUT ranges, and excellent protection against over- and under-voltage faults.
Undervoltage is related to a short circuit: VOUT falls when a short circuit is present and the controller cannot regulate the supply voltage. If that voltage remains below 70% of its nominal value for 6144 clock cycles, IC2 latches and turns both devices off. To restart IC2, you must either switch off the power supply or toggle the active-low SHDN signal.
Figure 1. The circuit adds auto-retry capability to IC2, thereby enhancing its usefulness for telecom and other applications.
The microprocessor supervisor (IC1) includes an internal power-fail comparator and manual-reset circuitry (MR). IC1's PFI input detects whether VOUT (1.8V) is above the internal reference voltage (1.25V). If VOUT falls below 1.25V ( due to a short circuit, for instance), the active-low PFO output generates a pulse using the internal 60k pull-up resistor and external 0.1µF capacitor. The pulse drives active-low MR low, causing active-low RST to assert and pull active-low SHDN low. After a timeout delay of 140ms, active-low RESET and active-low SHDN go high, re-enabling IC2. This supervision is also in effect when the supply voltage is first switched on: the 3.5V rail stabilizes after 140ms, causing active-low RST to go high and activate IC2.
A similar version of this article appeared in the September 2, 2002 issue of Electronica magazine.
The MAX1637 (IC2 in Figure 1) is a popular device for telecom applicaTIons. It offers PWM operation, small size, high MOSFET-drive capability, wide VIN and VOUT ranges, and excellent protection against over- and under-voltage faults.
Undervoltage is related to a short circuit: VOUT falls when a short circuit is present and the controller cannot regulate the supply voltage. If that voltage remains below 70% of its nominal value for 6144 clock cycles, IC2 latches and turns both devices off. To restart IC2, you must either switch off the power supply or toggle the active-low SHDN signal.
Figure 1. The circuit adds auto-retry capability to IC2, thereby enhancing its usefulness for telecom and other applications.
The microprocessor supervisor (IC1) includes an internal power-fail comparator and manual-reset circuitry (MR). IC1's PFI input detects whether VOUT (1.8V) is above the internal reference voltage (1.25V). If VOUT falls below 1.25V ( due to a short circuit, for instance), the active-low PFO output generates a pulse using the internal 60k pull-up resistor and external 0.1µF capacitor. The pulse drives active-low MR low, causing active-low RST to assert and pull active-low SHDN low. After a timeout delay of 140ms, active-low RESET and active-low SHDN go high, re-enabling IC2. This supervision is also in effect when the supply voltage is first switched on: the 3.5V rail stabilizes after 140ms, causing active-low RST to go high and activate IC2.
A similar version of this article appeared in the September 2, 2002 issue of Electronica magazine.
Minsound offers a great range of Driver Units,providing accurate reproduction.high intelligibility and dependable performance in commercial sound,signaling and public address loudspeaker systems.
All models are suited for Minsound reflex horns,equipped with the industry standard 1-3/8"-male tread pattern.
This series driver units are made of Neodymium magnet for good performance.
Neodymium Driver Units,Neodymium Driver,Neodymium Drivers,neodymium speaker magnets,Neodymium magnets
Taixing Minsheng Electronic Co.,Ltd. , https://www.paloudspeaker.com