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AS1923 Datasheet PDF : 17 Pages
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AS1923
Datasheet - Detailed Description
8 Detailed Description
The AS1923 is a very small, low-power, quad-voltage microprocessor supervisory circuit designed to maintain system integrity in multi-supply
systems (see Figure 10). The device offers several factory-trimmed under-voltage threshold values that minimize or eliminate the need for exter-
nal components.
Preset voltage monitoring values of +5.0, +3.3, +3.0, +2.5, +1.8, and -5.0V (see Ordering Information on page 14) are available for a wide range
of applications such as telecommunications equipment, desktop and notebook computers, high-end printers, data storage equipment, and net-
working equipment applications.
The device is powered via the IN2 input (3.0 to 3.3V) and a reset is asserted if VIN1 or VIN2 is > 1V. For improved performance, the AS1923 was
lid also designed to ignore fast INx transients.
Figure 10. AS1923 - Block Diagram
va 4
+
IN1
ill –
t 5
+
G s IN2
–
s A nt 6
+
e IN3
m t –
IN1
3V
5V Pullup
Timeout
(220ms)
3
RESETN
a n 1
+
o IN4
–
al c Bandgap
ic Reference
AS1923
Optional on AS1923B Only
hn The quad-voltage monitor/reset circuitry includes an accurate bandgap reference, four precision comparators, and a series of internal trimmed
resistor-divider networks to set the factory-trimmed reset threshold values.
c The resistor networks scale the specified INx reset voltages to match the internal bandgap reference/comparator voltage. User-adjustable
e threshold options bypass the internal resistor networks and connect directly to one of the comparator inputs (an external resistor-divider network
is required for threshold matching).
TEach of the internal comparators has a typical hysteresis of 0.5% with respect to its reset threshold. This built-in hysteresis improves device
immunity to ambient noise without significantly reducing threshold accuracy when an input sits at its specified reset voltage.
Note: Threshold voltage options (fixed and adjustable) are designated by the single-letter code in the model number (see Ordering Informa-
tion on page 14).
www.austriamicrosystems.com/Supervisors/AS1923
Revision 1.01
8 - 16
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