AS1920-18-T austriamicrosystems, AS1920-18-T Datasheet - Page 8

• Manufacturer Part Number: AS1920-18-T
• Description: IC SUPERVISOR PUSH/PULL SOT23-5
• Manufacturer: austriamicrosystems
• Type: Multi-Voltage Supervisorr

Specifications of AS1920-18-T

• Number Of Voltages Monitored: 3
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 1.683V, 2.805V, Adj
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AS1920/AS1922
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
Supply Monitoring
The AS1920/AS1922 are low-power, high-accuracy triple-supply monitoring circuits with a single 200ms microproces-
sor reset output.
All V
AS1920/AS1922 will assert a reset during powerup, powerdown and brownout conditions on one or all of the V
inputs.
Power Detect
The AS1920/AS1922 is powered from the 3V input pin (V
pin RESETN low as soon as the primary input pin is ≥1V or the secondary input pin is ≥1V.
Powerup
The power detect circuitry ensures that RESETN will be low when either V
V
nal timer will be started and RESETN will be driven high after 200ms.
Powerdown
On powerdown, if any of the V
teed until V
Override Functions
As the trip points for V
should be tied to V
V
Note: Pin V
Ensuring RESETN Valid for Supply Voltages < 1V
When the supplies drops below 1V the RESETN output current sink capability is greatly reduced. Stray currents and
stray capacitance to signals other than GND can cause the RESETN output to float. This is not relevant for most appli-
cations since most microprocessors and other circuits do not operate with a supply voltage < 1V.
In applications where the RESETN output must be valid down to 0V, a pulldown resistor from pin RESETN to ground
will ensure RESETN is held low
Figure 12. Typical Application w/Resistor on RESETN Output to GND
The value of the pulldown resistor (R
value of R
excess supply current, therefore a value of 100kΩ is recommended for the pulldown resistor.
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CC
CC18
CC
inputs is below its reset threshold, RESETN will stay at a logic low. When all V
and operating from a 1.8V supply will assure the continuous assertion of RESETN.
inputs (V
3
CC3
is too large RESETN may still float, and if the value of R
CC3
and V
CC18
must be used in all configurations.
CC3
, V
CC18
CC3
or V
CC3
Adjustable
and V
< 1V.
CC18
, and V
Supply
CC
. In a similar manner if pin V
CC18
(see Figure
inputs drop below its threshold, RESETN is held at a logic low (0.3V) and is guaran-
CCA
3
will always be greater than the trip point for V
) is a trade-off between pulldown strength and loading of the RESETN pin. If the
R
) must be above their thresholds to prevent a reset from being asserted. The
1.8V
1
3V
12).
R
2
V
V
V
CC18
CCA
CC3
5
4
3
Revision 1.00
AS1920/
AS1922
CC3
CC18
). The power detect circuitry ensures that the device pulls
is not used it should be tied to V
3
is too small it may load RESETN and also use
1
RESETN
2
GND
CC18
or V
100kΩ
CCA
CC
R
CC3
3
inputs have stabilized, an inter-
, if pin V
≥1V. As long as any one of the
CCA
CC3
is not used, it
. Tying V
CC3
CC
8 - 14
to