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AS431 Family of References

The AS431 is a three-terminal adjustable shunt regulator providing an accurate 2.5V bandgap reference. The adjustable shunt regulator is ideal for a wide variety of linear applications that can be implemented using external components to obtain adjustable currents and voltages, though many of aspects of the AS431 have been optimized for its use as an amplifier.

In the standard shunt configuration, the combination of low temperature coefficient (T.C.), sharp turn-on characteristics, low output impedance and programmable output voltage make this precision reference a perfect zener diode replacement.

The AS1431 has nominal precision of 0.4% and operates over the full -55C to 125C temperature range. The AS431 operates over the range of 0 to 105C and is specified at 0.5% tolerance. The A431 has a 1% bandgap reference and can be used as a direct replacement for the standard TL431. These products are available in TO-92, 8 lead SOIC, and SOT-89 packages.

The AS2431 is functionally identical to the 431, but has been implemented on a smaller die to allow packaging in the SOT-23. The newer technology supports an 18V breakdown compared to 36V on an AS431.

The new AS432 represents a functionally similar device with a reference of 1.25V. The production release of this device is pending. Initial silicon has been made available to major customers for sampling. Comments on the proposed specifications are welcome; send to ASD's sales group.

AS1004 Micropower Reference

The AS1004 is a two-terminal precision band-gap voltage reference with a low turn-on current of 10 mA.

Emulating a 1.235 V zener diode, the AS1004 operates more than three orders of magnitude of output current with minute output impedance and guaranteed stability. With an initial tolerance of ± 4 mV and guaranteed temperature performance, it is ideal for precision instrumentation, especially in low power applications. Being a low-voltage reference, the AS1004 is also well-suited as a reference for low-voltage power supply applications.

The AS1004 is pin-for-pin compatible with the LT1004 and the LM385 and offers improved specifications over both the LM385 and the MP5010. It is also available as a 2.5 V reference with a guaranteed start-up current of 20 mA.

AS384x series Current Mode PWM Controllers

The AS3842 family of control ICs provide pin-for-pin replacement of the industry standard UC2842 series of devices. The devices are redesigned to provide significantly improved tolerances in power supply manufacturing. The 2.5 V reference has been trimmed to 1.0% tolerance. The oscillator discharge current is trimmed to provide guaranteed duty cycle clamping rather than specified discharge current. The circuit is more completely specified to guarantee all parameters impacting power supply manufacturing tolerances. The AS3842 performs to electrical specifications more demanding than industry standard 2842, over the temperature range of 0 to 105C. A wider range AS2842 family extends the range to -40C.

In addition, the oscillator and flip-flop sections have been enhanced to provide additional performance. The RT/CT pin now doubles as a synchronization input that can be easily driven from open collector/open drain logic outputs. This sync input is a high impedance input and can easily be used for externally clocked systems. The new flip-flop topology allows the duty cycle on the AS3844/5 to be guaranteed between 49 and 50%. The AS3843/5 requires less than 0.5 mA of start-up current over the full temperature range.

A new addition to the family scheduled for release in 1998, the AS2208 , loses the error amplifier input of the 3842 and replaces it with the latching OV fault input. Faults remain latched even as the chip cycles through its shutdown state using the Undervoltage Lockout. Additionally, the AS2208 has an improved micropower start-up current (< 100 uA).

Temperature Transducer

The AS300 is a two-terminal integrated circuit temperature sensor. It is a precision-trimmed shunt type regulator that emulates a zener diode in function. Its output voltage is linearly proportional to temperature in Kelvin. The output voltage is calibrated for 3.000 V at 27 C (300 K) and increases by 10 mV/C. The AS300 is available in three packages. The SOT-223, TO-92 and 8 lead SOIC.

Over-Temperature Monitor

The AS273 is a series of programmable over-temperature detectors. Each is internally composed of a precision 2.5 V shunt reference, a proportional-to-absolute temperature thermal sensor, a comparator with controlled hysteresis, and an open collector output that indicates an over-temp condition. The threshold for the over-temp signal can be set to any of three values on a given part by controlling the magnitude of the reference shunt current.

The AS273 has an excellent absolute temperature accuracy of ±3 C for each of the three over-temp thresholds. The low power dissipation minimizes any temperature sensing errors due to self-heating. There is either 5 or 10 degrees of temperature hysteresis to prevent bouncing when an over-temp condition is removed. The AS273 is available in three packages. The SOT-223, TO-92 and 8 lead SOIC.

Bipolar Semicustom Array

The AS17xx is Astec's proprietary semicustom bipolar array. This semicustom IC is a collection of individual transistors and resistors in a fixed configuration. The custom circuit is manufactured by creating a single metal mask to connect the components. The spec includes device data, layout information, and SPICE models.

ATX Chipset

The AS2214 and AS2316 are a chipset intended for use in offline power supples. They are scheduled for release for sale to our external customers in 1998.

The AS2214 provides a basic current mode control similar to the AS3842. In addition, it allows for soft-start, a buffered ramp for slope injection, and a bulk under-voltage monitor to allow for controlled turn-on. The chip is intended both for use with an auxilliary rail or for auto-restart. In either case, a UV input can monitor either the bulk or a secondary fault signal to latch the controller off. An AC monitoring scheme allows resetting of faults by cycling AC but without forcing discharge of the bulk supply.

The AS2316 AS2316 provides monitoring of +5 and +12V outputs, plus optionally +3.3V, -5V and -12V. Also monitored is the "AC" condition (usually switching waveform on transformer) to generate standard POK signal and a fault output. The fault output responds to overvoltages of the rails, and optionally can respond to undervoltages, with blanking of the initial turn-on undervoltage condition.