RayStar Microelectronics Technology Inc.
Features
Data Sheet
RS/IT809 Reset IC
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digital systems. They provide excellent circuit reliability
and low cost by eliminating external components and
adjustments when used with +3.3V, +3.0V, or 2.5V
powered circuits.
These circuits perform a single function: they assert
a reset signal whenever the VCC supply voltage declines
below a preset threshold, keeping it asserted for at least
140ms after VCC has risen above the reset threshold.
Reset thresholds suitable for operation with a variety of
supply voltages are available.
Configurations
for
The RS/IT809 have push-pull outputs and have an
active-low /RESET output. The reset comparator is
designed to ignore fast transients on V
CC
, and the
outputs are guaranteed to be in the correct logic state for
V
CC
down to 1V.
Low supply current makes the RS/IT809 ideal for
use in portable equipment. The ICs are available in 3 pin
SOT23 packages.
Precision supply-voltage monitor
- 4.63V (RS/IT809L)
- 4.38V (RS/IT809M)
-
4.00V (RS/IT809J)
- 3.08V (RS/IT809T)
- 2.93V (RS/IT809S)
- 2.63V (RS/IT809R)
- 2.32V (RS/IT809Z)
140ms(min) reset pulse width
Push-Pull
RS/IT809
/RESET
Output
12μA Supply Current
Guaranteed Reset(/Reset) Valid to V
CC
= +1.0V
Power Supply Transient Immunity
No External Components
Ordering Information
Part Number
RS/IT809XTE
Package
Lead free and Green SOT23-3
Note:
“x” refers to voltage range, see below table.
Description
The RS/IT809 are microprocessor (μP) supervisory
circuits used to monitor the power supplies in μP and
Suffix: X—Monitored Voltage
X
L
Reset Threshold (V)
4.63
M
4.26
J
4.0
T
3.08
S
2.93
R
2.63
Z
2.32
Block Diagram
V
CC
V
RST
+
-
Reset Logic
and Timer
RESET
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Pin Configuration
RS809XT
1
GND
Data Sheet
RS/IT809 Reset IC
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VCC
3
2
RESET
SOT23-3
Pin Description
Pin
Type
Description
Supply Voltage.
Reset is asserted when V
CC
drops below the Reset Threshold Voltage (V
RST
). Reset
remains asserted until V
CC
rises above V
RST
and keep asserted for the duration of the Reset Timeout
Period (t
RS
) once V
CC
rises above V
RST
.
Ground
Active-Low Reset Output (Push-Pull).
It goes low when Vcc is below the reset threshold. It remains
low for about 240ms after Vcc rises above the reset threshold (V
RST
).
VCC
-
GND
-
RESET
O
Functional Description
Reset Output
A microprocessor (P) reset input starts the
P
in a known state. Whenever the
P
is in an unknown state, it should be held in
reset. The supervisory circuits assert reset during power-up and prevent code execution errors during power-down or brownout
conditions.
On power-up, once Vcc reaches about 1.0V, /RESET is a guaranteed logic low of 0.4V or less. As Vcc rises, /RESET stays low.
When Vcc rises above the reset threshold, an internal timer releases /RESET after about 200ms. /RESET pulses low whenever
Vcc drops below the reset threshold, i.e. brownout condition. If brownout occurs in the middle of a previously initiated reset pulse,
the pulse continues for at least another 200ms. On power-down, once Vcc falls below the reset threshold, /RESET stays low and is
guaranteed to be 0.4V or less until Vcc drops below 1.0V. Reset
Timing Diagram
shows the timing relationship.
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Typical Application Circuit
Data Sheet
RS/IT809 Reset IC
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RS809
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Maximum Ratings
Storage Temperature ............................................................-55
o
C to +150
o
C
Ambient Temperature with Power Applied.......................... -40
o
C to +85
o
C
Supply Voltage to Ground Potential (Vcc to GND) ..............-0.3V to +6.0V
DC Input Voltage (All inputs except Vcc and GND)......-0.3V to V
CC
+0.3V
DC Output Current (All outputs) ..........................................................20mA
Power Dissipation .............................................................................. 320mW
Data Sheet
RS/IT809 Reset IC
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Note:
Stresses greater than those listed under MAXIMUM
RATINGS may cause permanent damage to the
device. This is a stress rating only and functional
operation of the device at these or any other condi-
tions above those indicated in the operational sec-
tions of this specification is not implied. Exposure
to absolute maximum rating conditions for extended
periods may affect reliability.
Recommended Operation Conditions
Sym
Description
Supply Voltage for RS/IT809(L/M)
Supply Voltage for RS/IT809(T/S)
Supply Voltage for RS/IT809(R)
Supply for RS/IT809(Z)
T
A
Operating Temperature
Test Conditions
-
-
-
-
-
Min
4.5
3.0
2.8
2.5
-40
Typ
5.0
3.3
3.0
-
-
Max
5.5
5.5
5.5
5.5
85
Unit
V
V
V
V
℃
V
CC
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DC Electrical Characteristics
(V
CC
= V
RN
+ 5% to 5.5V, T
A
= -40~85º unless otherwise noted.)(Note 1)
C,
Symbol
V
CC
I
CC
I
CC
Description
Operating Voltage Range
Supply Current
Supply Current
Threshold voltage(Falling
Edge) Note 2
Test Conditions
-
Vcc < 5.5V, RS8xxL/M
Vcc < 3.6V, RS8xxR/S/T/Z
T
A
= 25º
C
Vrst
T
A
= -40 ~ 85º
C
RS/IT809L~Z
RS/IT809L~Z
Min
1.0
-
-
V
RN
- 1.5%
V
RN
- 2.5%
Vcc-1.5
0.8×
Vcc
0.8×
Vcc
0.8×
Vcc
-
-
Typ
-
10
10
V
RN
V
RN
-
-
-
-
-
-
Data Sheet
RS/IT809 Reset IC
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Max
5.5
30
30
V
RN
+ 1.5%
Unit
V
µA
V
V
RN
+ 2.5%
-
-
-
-
0.4
0.3
V
V
Vcc
4.5V Isource=800µ
A
V
OH
Output High Voltage
Vcc
2.7V Isource=500µ
A
Vcc
1.8V Isource=150µ
A
Vcc
1.0V Isource=4µ
A
Vcc
4.5V Isink=3.2mA
V
OL
Output Low Voltage
Vcc
2.7V Isink=1.2mA
-
-
0.3
Vcc
1.0V Isink=100µ
A
Note: 1.
Parameters of room temperature guaranteed by production test and parameters of full-temperature guaranteed by design.
2.
V
RST
is Reset threshold voltage when V
CC
falls from high to low level. V
RN
is nominal reset threshold voltage.
AC Electrical Characteristics
Symbol
Description
Test Conditions
T
A
= -40~85º
C
RS/IT809L~Z
Min
140
Typ
240
Max
400
Unit
ms
Reset Timing Diagram
VCC
V
RST
V
RST
+ V
RTH
t
RS
RESET
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