YB1921
3-Pin Microprocessor Reset Monitor
Introduction
The YB1921 is a cost-effective system
supervisor Integrated Circuit (IC) designed to monitor
V
CC
in digital and mixed signal systems and provide a
warning signal when the system power supply is out
of working range, and a reset signal to the host
processor when necessary. No external components
are required.
The reset output is driven active within 20μsec
of V
CC
falling through the reset voltage threshold.
Reset is maintained active for a minimum of 140msec
after V
CC
rises above the reset threshold. The YB1921
has an active-low RESET output. The output of the
YB1921 is guaranteed valid down to V
CC
=1V.
The YB1921 is optimized to reject fast transient
glitches on the V
CC
line. Low supply current of 18μA
(V
CC
=3.3V) makes these devices suitable for battery
powered applications.
Features
Precision V
CC
Monitor for 2.8V, 3.0V, 3.3V,
and 5.0V Supplies
140msec Guaranteed Minimum RESET
Output Duration
RESET Output Guaranteed to V
CC
=1.0V
Low 18μA Supply Current
V
CC
Transient Immunity
Small SOT-23 Package
No External Components
Wide Operating Temperature: 0°C to 85°C
Applications
Computers
Embedded systems
Battery powered equipment
Critical µP power supply monitoring
Application Diagram
YB1921
www.yobon.com.tw
1
YB1921
3-Pin Microprocessor Reset Monitor
Absolute Maximum Ratings
(1)
Parameter
Symbol
Value
Value
5.5
-0.3 to (Vcc+0.3)
20
20
Internally Limited
(3)
Infinite
230
0~85
260
0 to+125
-60 to+150
Unit
V
V
mA
mA
—
—
°C/W
°C
°C
°C
°C
Input Voltage
Output Voltage
Input Current
Output Current
Power Dissipation
Output Short Circuit Duration
Thermal Resistance, Junction-to-Ambient
Operating Temperature Range
Lead Temperature (Soldering, 10 sec.)
Junction Temperature
Storage Temperature
V
CC
RESET
—
I
OUT
P
D
—
Θ
JA
T
A
—
T
J
T
S
Recommended Operating Conditions
(2)
Parameter
Symbol
Min
Power Supply Voltage
Junction Temperature
V
CC
T
J
2.0
0
Value
Type.
—
—
Max
5.5
+125
Unit
V
°C
YB1921
www.yobon.com.tw
2
YB1921
3-Pin Microprocessor Reset Monitor
Electrical Characteristics
Vcc=5V for L/M/J; 3.3V for T/S; 3.0V for R, TA = 25°C, unless otherwise specified.
Parameter
Input Voltage
Supply Current
Symbol
V
CC
I
CC
Condition
—
—
Min
2.0
—
4.54
4.29
3.92
3.02
2.87
2.58
—
Typ
—
18
4.63
4.38
4.00
3.08
2.93
2.63
30
Max
5.5
25
4.72
4.47
4.08
3.14
2.99
2.68
—
Unit
V
μA
Reset Threshold
V
TH
YB1921
L-4.63V
YB1921
M-4.38V
YB1921
J-4.00V
YB1921
T-3.08V
YB1921
S-2.93V
YB1921
R-2.63V
—
V
Reset Threshold Temperature
Coefficient
(4)
V
CC
to Reset Delay V
CC
= V
TH
to
(V
TH
– 100mV)
Reset Active Timeout Period
RESET Output Voltage Low
RESET Output Voltage High
—
ppm/°C
—
—
V
OL
V
OH
—
—
I
SINK
= 3mA
I
SOURCE
= 800μA
—
—
—
0.8V
CC
20
240
—
—
—
—
0.4
—
μsec
msec
V
V
Note 1:
Exceeding the absolute maximum rating may damage the device.
Note 2:
The device is not guaranteed to function outside its operating rating.
Note 3:
The maximum allowable power dissipation at any T
A
(ambient temperature) is calculated using: P
D (MAX)
=
(T
J (MAX)
– T
A
)/Θ
JA
. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the
regulator will go into thermal shutdown. See “Thermal Consideration” section for details
Note 4:
RESET threshold temperature coefficient is the worst case voltage change divided by the total temperature
range.
YB1921
www.yobon.com.tw
3
YB1921
3-Pin Microprocessor Reset Monitor
Pin Configuration
Pin Description
Pin No.
2
Symbol
GND
Ground
Description
RESET
1
VCC
3
S809La
1
GND
2
RESET
RESET output remains low while Vcc is
below the reset voltage threshold and
for 240msec(typ) after Vcc rises above
reset threshold
Supply Voltage (typ.)
3
Vcc
Ordering/Marking Information
Reset Vcc
threshold (V)
4.63
4.38
4.00
SOT-23
3.08
2.93
2.63
Package
Part Number
Marking
S809La
S809Ma
S809Ja
S809Ta
S809Sa
S809Ra
•
Marking Information
Starting with 0, a bar underlined 0 is for
production year 2006, on top of 9 is for year 2007.
And underlined 9 is for year 2008
The next character is marked on top of 8 for
2009, and underlined 8 for 2010. The naming
pattern continues with consecutive characters for
later years.
The last character is the week code. (A-Z: 1-26,
YB1921
LB-F
YB1921
MB-F
YB1921
JB-F
YB1921
TB-F
YB1921
SB-F
YB1921
RB-F
•
•
•
•
a-z: 27-52)
A dot on top right corner is for lead-free process.
•
Ordering Information
YB1921
www.yobon.com.tw
4
YB1921
3-Pin Microprocessor Reset Monitor
Dimension
Outline Drawing For SOT-23
C
J
B
H
D
A
E
F
G
K
L
SYMBOL
MIN
A
B
C
D
E
F
G
H
J
K
L
0.110
0.047
0.083
0.035
0.070
0.018
0.015
INCHES
MAX
0.120
0.055
0.104
0.040
0.080
0.024
0.020
0.004
0.040
0.007
0.027
MILLIMETERS
MIN
2.80
1.20
2.10
0.89
1.78
0.45
0.37
0.013
0.887
0.085
—
MAX
3.04
1.40
2.64
1.03
2.05
0.60
0.51
0.10
1.02
0.18
0.69
0.0005
0.034
0.003
—
YB1921
www.yobon.com.tw
5
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